The effect of a blended indoor and outdoor multicomponent structured exercise program on depressive symptoms in Hong Kong older adults: study protocol of a randomized controlled trial

The effect of a blended indoor and outdoor multicomponent structured exercise program on depressive symptoms in Hong Kong older adults: study protocol of a randomized controlled trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Study protocol The effect of a blended indoor and outdoor multicomponent structured exercise program on depressive symptoms in Hong Kong older adults: study protocol of a randomized controlled trial Shishi CHENG, Yanping DUAN, Wui-Man Benson LAU, Wei LIANG, Ngai-Man Jackie CHAN, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4274102/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Nov, 2025 Read the published version in BMC Public Health → Version 1 posted 4 You are reading this latest preprint version Abstract Background: Depression is a mental health problem often occurring in older adults. More attention has been paid to the benefits of green exercise on mental health in recent years. However, most existing studies of structured exercise on older adults’ depressive symptoms only encompassed one or two exercise components (aerobic/muscular strength/balance) in indoor setting. Considering the advantages of indoor exercise and the high relevance between nature and mental health, the combination of indoor and outdoor multicomponent structured exercise (MSE) programs might be able to maximize intervention effectiveness. The aim of this study is to develop and examine the effect of a blended indoor and outdoor MSE program on depressive symptoms, physical fitness and physical activity (PA) enjoyment in Hong Kong older adults with depressive symptoms. Methods: The 16-week single-blinded randomized controlled trial (RCT) (2 sessions/week, 90 min/session) will include 129 community-dwelling older adults aged 60 to 74 years old with depressive symptoms. Participants will be randomized to one of three groups (IG-1: a blended indoor and outdoor MSE group; IG-2: an indoor-only MSE group; CG: a control group) using 1:1:1 allocation ratio. The MSE program (aerobic + muscular strength + balance) will be conducted in IG-1 and IG-2. Primary outcome will be depressive symptoms. Secondary outcomes will include salivary cortisol, physical fitness, physical activity (PA) enjoyment. In addition, the mediating role of connectedness to nature (CN) will be examined to reveal the psychological mechanism of intervention. All measured data will be collected at the pre-intervention, post-intervention, and 3-month follow up stages. Discussion: This study will take the initiative to implement the blended indoor and outdoor MSE intervention catering older adults with depressive symptoms. The results will provide more comprehensive evidence support for non-pharmacological interventions and guide future relevant public health policies for the improvement of older adults’ depressive symptoms. Trial registration: This trial is prospectively registered in the ClinicalTrials.gov. Trial registration number NCT06190327 registered 19 December 2023. Multicomponent structured exercise depressive symptoms older adults blended environment outdoor exercise indoor exercise Figures Figure 1 Background Depression is a common mental health problem often occurring in older adults, and it is also a major risk factor for disability and death in older adults [1, 2]. Among the estimated 280 million individuals affected by depression globally, those with the age over 60 years old occupied nearly 5.7% [3]. Moreover, a previous study indicated a high prevalence rate of depressive symptoms (around 30%) among older adults in Hong Kong [4]. The prevalence of depressive symptoms among Hong Kong older adults have been aggravated during the COVID-19 pandemic leading to 43.7% for males and 54.8% for female [5]. Older adults who suffer from depressive symptoms may lead to several negative consequences on their physical and mental health, which includes anxiety, insomnia, vague somatic pains, poor quality of life, cognitive decline, social isolation, and recurrent thoughts of death or suicide [6, 7, 8]. In addition, older population with mild and severe depressive symptoms may require and use more medical services but use fewer social or recreational services than those without depressive symptoms [9]. Therefore, improving depression among Hong Kong older adults is a public health and economic imperative. Exercise has been demonstrated as an effective way to buffer older adults’ depressive symptoms from numerous evidence [10, 11]. It is attributed to some physiological changes, such as stimulating the release of endorphins [12], increasing the production of brain-derived neurotrophic factor (BDNF) [13], regulating hypothalamic-pituitary-adrenal (HPA) axis and reducing cortisol level [14]. In addition, the majority of RCT examining physical exercise on depression have mainly focused on conducting structured exercise. Three systematic reviews have revealed that the aerobic exercise (e.g., walking, dancing) [15], muscular strength training (resistance training) [16], and balance training [17], as three key exercise components of structured exercise, can significantly improve depressive symptoms of middle-aged and older adults respectively. Moreover, a recent systematic review has highlighted that exercise programs combining aerobic training and resistance training have a greater improvement on older adults’ depressive symptoms than only adopting one exercise components [18]. However, most of existing related RCTs just comprise of one or two exercise components of structured exercise and focus on the clinical patients associated with major depression. There is limited research combining all three key exercise components in an exercise program and targeting non-clinical older adults with depressive symptoms. Over the past two decades, more attention has been paid to the role of nature, and the benefit of outdoor exercise on human health in the past two decades. A growing body of evidence have illustrated that exercise in a natural environment (green exercise) can provide greater physiological and psychological benefits compared to indoor exercise [19, 20]. It may provide the double beneficial effect on depression improvement via promoting a greater feeling of revitalization, and enjoyment [21, 22]. There are several mechanisms can justify the effect of natural environment on depression. From the perspectives of biology and physiology, exposing to nature is associated with biological stress recovery [23]. In the brain, nature exposure is linked to reduced lateral prefrontal activation, which is associated with less rumination, a common symptom in depression [24]. Furthermore, nature exposure is also related to perceptual fluency (the ease with which a stimulus is processed in the brain), where individuals seem to prefer the type of fractal patterns (having high internal repetition of visual information) that are displayed in nature, responding to those with stress relief, as compared with nonnatural, or nonfractal patterns [24]. From the psychological perspective, mental health benefits from exposure to natural environments occur through a sense of belonging, embeddedness and connection to nature, which is linked to the concept of connectedness to nature (CN) [25]. CN, as a trait, is defined as the individual’s experiential sense of oneness with the natural world [26]. Numerous evidence have shown that outdoor exercise engagement is associated with CN [27]. Several longitudinal studies have shown that CN is one of a key predictor of mental health, and individual who feel stronger connection with nature are more likely to have more positive emotions and less depressive symptoms [28, 29]. However, the partial mediating role of CN was only investigated by a cross-sectional study [26], and CN as a mediators in the effect of green exercise on depression has not been sufficiently examined using RCTs. Although exercising in natural environment have already shown the improvement effect of depression, existing studies of structured exercise programs for older adults with depressive symptoms were mainly conducted in the lab or indoor environment [20]. Compared with outdoor exercise which is easily influenced by the weather and with low access of available facilities, indoor exercise is more comfortable, quiet, and convenient to operate, especially for older adults [20]. Considering the high relevance between nature and mental health, the combination of indoor and outdoor exercise programs might be able to maximize intervention effectiveness while maintaining the benefits for each type of intervention. However, there were few empirical evidence on the blended indoor and outdoor exercise program. Only one cross-sectional study revealed that adults who combine outdoor with indoor exercise reported more psychological well-being related with exercise than those taking indoor exercise [30]. Only one RCT study supported the effects of a 8-week blended indoor-outdoor balance training programme on improving balance, gait and functional performance in patient with Parkinson's disease [31]. Therefore, more RCT studies of exercise program conducted in both indoor and outdoor settings among non-clinical older adults with depressive symptoms are needed. Furthermore, the potential psychological mechanism of the intervention should be explored. Aim of the current study The aim of this study is to develop and examine a blended indoor and outdoor MSE program on depressive symptoms, physical fitness and PA enjoyment in Hong Kong community-dwelling older adults with depressive symptoms. Five hypotheses will be tested in this study: (a) The intervention groups (IG-1: the blended indoor and outdoor MSE intervention group; IG-2: indoor-only MSE intervention group) would improve depressive symptoms (determined by the 15-item Geriatric Depression Scale) greater than the control group (CG). IG-1 would also improve depressive symptoms more than IG-2. (b) The intervention groups (IG-1 & IG-2) would decrease concentration of salivary cortisol more than CG. IG-1 would also decrease concentration of salivary cortisol more than IG-2. (c) The intervention groups (IG-1 & IG-2) would improve physical fitness more than CG. (d) The intervention groups (IG-1 & IG-2) would improve PA enjoyment more than CG. IG-1 would also improve PA enjoyment more than IG-2. (e) CN would mediate the effectiveness of the MSE intervention (IG-1=1; IG-2=0) on depressive symptoms. Methods and design Study design This study is a single-blind three-arm parallel RCT approved by the Research Ethics Committee of Hong Kong Baptist University (ID:REC/21/22/0281) and registered in the ClinicalTrials.gov (NCT06190327). This protocol follows the standardized guidelines proposed by the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT). Participants will be recruited from community senior service centers in Hong Kong, where all older adults are community-dwelling residents. All eligible participants will be randomly assigned into three groups: (a) IG-1: the blended indoor and outdoor MSE intervention group; (b) IG-2: indoor-only MSE intervention group; (c): CG: control group, using the random function available in Excel software, in a ratio of 1:1:1. Assessments will be conducted at pre-intervention (T1: immediately after the eligibility assessment), post-intervention (T2: immediately after 16-week intervention), 3-month follow up (T3: 3 month after intervention the end of the intervention). Assignments will be blinded to the assessors until all tests are finished. Study population Older adults will be involved in this study if they: 1) are aged 60-74 years living in the community. 2) no contraindications for physical exercise (e.g., physical disability, unstable cardiovascular diseases, etc.). 3) scoring 5-15 using 15-item Geriatric Depression Scale (GDS-15) [32] (i.e., mild, moderate, and severe level of depressive symptoms). 4) able to communicate in Cantonese. Participants will be excluded if they: 1) suffer from cognitive impairment identified by the Chinese version of the Mini-Mental Status Examination (MMSE) (i.e., score < 24) [33]; 2) fail to pass the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+) screening or without the physician’s approval for the readiness of participation in the moderate-intensity exercise. 3) have history of a clinical diagnosis of depression and receiving relevant treatment. 4) are attending other health projects related to physical exercise. Sample size was calculated by G*Power software (version 3.1.9.6) with MANOVA with repeated measures. Based on the previous meta-analysis examine the effect of exercise intervention on people with non-clinical depressive symptoms (Cohen's d=0.34) [34] and a study compared the effect of the combined exercise (aerobic + resistance) on depression for postmenopausal women in outdoor setting to it conducted in indoor setting (Cohen's d=0.44) [35], an average small effect size (Cohen’s d) of 0.34 is used in the present study to achieve adequate power. Assuming a statistical power (1-β) of 80%, α of 0.05, and approximately 20% dropout rate, a total of 129 participants (43 in each arm) will be required to achieve a robust evaluation of treatment effects. Participants will be recruited from community senior service centers in Hong Kong. Advertisement of this program will be distributed by the manager of the senior center to all senior members via social media (e.g. WhatsApp groups, Facebook), seniors' group meetings, and bulletin boards. If interested, potential participants will be able to register their details. After registration, the GDS-15 with Chinese version [32] will be adopted to screen out those with depressive symptoms. Participants who score less than five will be excluded. If participants suffer from cognitive impairment identified by MMSE [33] screening with the score less than 24, will also be excluded. Moreover, if participants answer “yes” to any of the items of PAR-Q+ screening, they will be required to obtain medical approval from their general practitioner before involving in this exercise program. Eligible participants will attend the baseline assessment (T1) at community senior service centers close to their area of residence. Investigator will introduce the study procedures individually to them, and all questions will be clarified. And then, they will be asked to sign an informed consent form before the commencement of the intervention, and authorize the research team to anonymously record, analyze, and use their data for academic purposes. Figure 1 shows the flowchart of participants from recruitment and allocation in this study. Intervention There will be four steps at the preparation stage of intervention development. Step 1: a steering group, consisting of key stakeholders who are involved in this program (i.e., elderly participants, manager of senior service center, exercise coach, and research team members), will be formed to develop intervention content, optimize the intervention components, to identify the facilitators and barriers for the intervention implementation, and to formulate strategies for maintaining participants’ engagement and adherence. Step 2: a one-month pilot study for blended indoor and outdoor MSE intervention group (IG-1) will be implemented to test and optimize the strategies and relevant materials. Participant recruitment, instruments, data collection, adaptability and feasibility of the intervention will be sufficiently considered in the pilot study. Step 3: a comprehensive plan of the intervention implementation will be established to guarantee the safety, effectiveness, supportiveness and enjoyment of the intervention implementation. An operational manual will also be constructed in this step. Step 4: an evaluation plan for the effectiveness of intervention implementation will be developed. Any amendments will be made if necessary. In addition, a briefing session will be provided for all eligible participants in senior service centers, participants will receive detailed information about the exercise program in which they are enrolled (e.g., study procedure, schedule). Furthermore, another briefing session with a mock test for student helpers (major in sport science) also will be arranged one to two weeks before the pre-test to introduce the details of data collection and intervention implementation. Intervention settings Participants in 16-week blended indoor and outdoor MSE intervention group (IG-1) will engage in one indoor exercise session and one outdoor session in each week, while those who are randomly assigned to 16-week indoor-only MSE intervention group (IG-2) will engage in two indoor exercise sessions in each week. Regarding the intervention setting, the indoor exercise session will be conducted in the activity room of the government sports center, which is around 150 square meters in size (see Picture 1). The outdoor exercise session will be held in an urban park namely Kowloon Park, which has outdoor facilities including a jogging track, a large open space with seats around and loggia. All these outdoor facilities are in the green natural environment (see Picture 2 to Picture 4). Exercise prescription Based on the British National Institute for Health and Care Excellence guidelines [36] and previous studies [34, 37], effective exercise training programs for older adults with depressive symptoms are generally 10-16 weeks with 2-3 sessions/week (≥ 45 min/session). Thus, this study will adopt a modest dose of intervention, including 16 weeks with 2 sessions/week (90 minutes/session). As the exercise mode of this study will be MSE combining aerobic, muscular strength and balance trainings, each 90-min session will consist of 10-min warm-up, 30-min aerobic training, 20-min muscular strength training, 20-min postural balance training, and 10-min cool-down. Both two intervention groups (IG-1 & IG-2) will be delivered safely and effectively by qualified coach recommended by the Physical Fitness Association of Hong Kong, China (PFA) with professional monitoring. According to the guidelines introduced by “ACSM’s Exercise for Older Adults” [38] and advice of PFA, the prescription of exercise programs for the two intervention groups will be formed (as shown in Table 1). First, a 10-min warm up (e.g. light walking and stretching) will be conducted. During the aerobic training, session 1/week of two intervention groups will conduct dancing via using chairs and towel, while session 2/week of two intervention groups will conduct walking (IG-1: outdoor walking in urban park, IG-2: indoor walking). As for the muscular strength training, weights (resistance) will be derived from participants’ own bodies, resistance band (15 pounds & 25 pounds), and adjustable ankle weights (0.5kg, 1kg, 2kg). The intensity of both aerobic training and muscular strength training will be light to somewhat hard (The rate of perceived exertion (RPE) 11 to 13, using the Cantonese version) [39]. Each participant will be required to report their RPEs during the aerobic and muscular strength training sessions. During postural balance training, there will be no restricted intensity, but the difficulty level of exercise will be increased from performing balance exercise without equipment (week 1-6) to with equipment (25cm Yoga mini balls) (week 7-16). Adjustment of training intensity and difficulty will be made in accordance with individual’s fitness level, and adaptability of the training. To ensure the safety and effectiveness of this exercise program, each intervention group will be separated into two sub-groups, with maximum 22 participants in each sub-group. It means that 2 sub-groups of 2 intervention groups will be conducted in separate timeslots but taught by the same coach at the same venue to ensure both sub-groups will receive similar teaching and learning quality. Participants in both two intervention groups will not be required to change their usual care pathways (e.g., medication use), and all interventions will be delivered while maintaining their original lifestyles. In order to strengthen the CN of IG-1 participants during the outdoor exercise session at Kowloon Park, the following strategies will be employed. During the 10-min warm up, the coach will lead participants executing light walking and stretching while guiding them to focus on their sensory experience during the exercise. Such as looking at the green vegetation around themselves and the sunlight falling through the gaps in the leaves (visual sense), listening to the birds singing from nature and the wind rustling through the leaves (auditory sense), smelling the fresh air mixed with grass and soil (olfactory sense), and feeling the touch of the breeze on the skin (tactile sense). During the aerobic training section, IG-1 participants will engage in a 30-minute nature walking along a trail surrounded by greenery. The walking route will circle an artificial lake and pass through some gentle ascents and descents in the terrain. During the nature walking, the coach will guild participants to interact with nature, including touching leaves and flowers and listening the sound of waterfalls and birds to deepen the immersion in the natural environment. During the muscular strength training and balance training, sounds from nature will be used as background music, and participants’ auditory senses will be stimulated and reinforced. The coach will ask all participants a question “When you perform the exercise, do you hear the birds singing from nature and the wind rustling through the leaves?” during strength training section and balance training section, respectively. All participants will be asked to report their answers (“Yes” or “No”) to the student helper. If participant’s answer is “No”, the student helper will remind the participant to focus on his/her auditory senses in the natural environment. Lastly, during the 10-minute cool down at the end of the outdoor MSE session, in addition to stretching, the coach will guide the participants to close their eyes with mind-body breathing to reflect on what they just have seen and felt during the exercise session in natural environment, such as the smell of soil and vegetation, the sound of waterfall, the feeling of touching the leaves and the color of flowers. By implementing these strategies, a stronger connection with nature can be promoted among participants in IG-1. Safety considerations and adverse events for two exercise groups During outdoor exercise session, if it rains and the rainfall is light or intermittent, participants can walk on the jogging track holding an umbrella and perform muscular strength and balance trainings in the open space of the park with loggia (see Picture 4). In case of the extreme weather conditions, such as yellow rainstorm warning or above issued by the Observatory, and extreme heat (above 30°C), the outdoor exercise session may be notified of cancellation in advance or rescheduled if deemed unsafe by the tutor. All outdoor sessions will be scheduled in the morning to avoid stronger sunlight and uncomfortable temperatures. Moreover, the researchers or coach will encourage and remind participants the night before each outdoor session to bring their plenty of water, towels, hat, sunglasses, and an alternative clothing. In response to sports injuries during indoor and outdoor exercise sessions, the first aid box will be prepared on-site. In addition, the coach and student helpers (major in sport science) who involving in this study all have first-aid certificates and equipped with knowledges and skills about sports injury prevention and preliminary treatment. They are capable to handle any sports injury issue among participants during this time. All adverse events reported by the participant will be recorded. Control group Participants randomly allocated to the CG will not receive any intervention during the whole program (16-week treatment and 3-month follow-up), and they will be required to maintain their current lifestyles. To monitor the control condition, participants will need to keep diaries to record their daily physical exercise, mood, medicines used, illness and participation in other health-related activities. The research assistant will biweekly give telephone calls to the participants to check their diaries and identify if they change their lifestyles or experience adverse events. Participant retention strategies Several effective strategies will be adopted for participant retention based on previous studies on depression treatment for older adults [40]. 1) emphasizing study benefits and promote positive attitudes for participating in this program (e.g., expected health outcomes, free tests of physical fitness). The results of each assessment will be compiled into a health report to be provided as feedback to the participants; 2) designing the intervention components according to the Safety, Supportive, Active, and Enjoyable principles (e.g., group-based, diverse exercise mode, utility of music and equipment); 3) applying several behavioral change techniques that facilitate the maintenance of participation during the intervention implementation (e.g., positive persuasion, social support, verbal encouragement, message reminder prior to the intervention session); and 4) providing financial incentives for completing all measurements of outcomes (HK$300 supermarket coupons for each participant). The retention strategies will be discussed with all relevant stakeholders who are the members of the steering group. Amendments will be made if necessary. Outcome evaluation of the intervention Data collection for all tests will be done by the researchers. All participants will be informed that the data obtained during the program will be stored in a computer and will be treated confidentially. Identification code will be used to identify each participant. Data entry will be handled by two other researchers in the research team. For this protocol, Data monitoring committee (DMC) is not needed as it is a low-risk study with short intervention duration. Primary outcome Depressive symptoms : The Chinese version of the 15-item Geriatric Depression Scale (GDS-15) [32] will be used to measure subjective depression levels. The GDS-15, as an effective measure of depressive symptoms in older adults, has been shown to have good reliability and validity in Chinese older adults [32, 41]. Answers will be given on a yes/no scale. Sample items will include “Are you basically satisfied with your life?” and “Do you prefer to stay at home, rather than going out and doing things?” in past week. The total score ranges from 0 to 15, where 0-4 = normal, 5-8 = mild depressive symptoms, 9-11 = moderate depressive symptoms and 12-15 = severe depressive symptoms. Assessments will be conducted at T1, T2 and T3. Secondary outcomes Salivary cortisol: Salivary cortisol will be measured as a biomarker for depressive symptoms. All participants will be provided with two salivate tubes and asked to collect the saliva samples (2-3ml) at awakening, and 30 min after awakening respectively on the next day. Participants will be instructed to rinse their mouth with normal saline but abstain from eating, drinking, or brushing their teeth prior to saliva collection. Participants will use passive drool method to collect saliva naturally in the mouth for 60 seconds before dribbling the saliva into containers. Following the collection of samples, participants will be instructed to record the exact time of collection on the label and freeze the salivate tubes in their home refrigerator (0-4 ℃) to keep the salivary cortisol stable until transport to the research lab. All the uncentrifuged saliva samples will then be transported and stored at -20℃ until analyses. Saliva will be assayed for cortisol (μg/dL) concentrations by a registered laboratory using a Salimetric high sensitivity ELISA kit [42]. The inter assay coefficients of variation (based on low- and high-control samples) is set at 5% for cortisol. Assessments will be conducted at T1, T2 and T3. Physical fitness: Physical fitness will be assessed using the Senior Fitness Test (SFT) Manual [43], which includes body mass index (BMI), 30s chair stand, 30s arm curl, 2min step test, chair sit-and-reach test, back scratch test and 8ft up-and-go test, to measure muscular strength, aerobic endurance, flexibility, agility and dynamic balance for older adults. This validated instrument is reliable with an intra-class correlation coefficient (ICC) ranged from 0.8 to 0.98. Assessments will be conducted at T1, T2 and T3. Physical activity enjoyment: The Chinese version of the 8-item physical activity enjoyment scale (PACES) [44] will be adopted to measure participant’s enjoyment level after engaging in blended indoor and outdoor MSE program. This scale has revealed strong internal consistency and reliability among Hong Kong older adults (Cronbach's alpha=0.92). It will be scored by 7 bipolar rating, from one extreme to the other extreme, for example, from “it’s very pleasant” to “it’s very unpleasant”. Assessments will be conducted at T1, T2 and T3. Connectedness to nature (CN) (mediator): CN will be measured using the 14-item connectedness to nature scale with Chinese version [45] to assess the sense of belonging to the natural world. The original scale was developed by Mayer & Frantz [46] with sound reliability (Cronbach's alpha=0.84). This five-point scale, ranging from 1 “strongly disagree” to 5 “strongly agree”. Sample items will include “I often feel like I am only a small part of the natural world around me, and that I am no more important than the grass on the ground or the birds in the trees”. Assessments will be conducted at T1, T2 and T3. Loneliness (covariate) : Loneliness will be measured by using the 6-item De Jong Gierveld Loneliness Scale with Chinese version [47]. This scale has been shown a sound reliability and validity for older adults in Hong Kong (Cronbach's alpha=0.76) [47]. Item 1 to item 3 as negatively worded items will be measured “emotional loneliness”, answer “yes” will score 1, answer “more or less” will score 1, answer “no” will score 0. Item 4 to item 6 as positively worded items will be used to assessed “social loneliness”, answer “yes” will score 0, answer “more or less” will score 1, answer “no” will score 1. Sample items will include “I experience a general sense of emptiness”, and “There are many people I can trust completely”. Assessments will be conducted at T1. Sociodemographic characteristics include name, mobile number, gender, age, educational level, household income, marital status, number of children and living status, will be collected at T1. Process evaluation of the intervention Process evaluation will be used to understand and evaluate implementation and participants’ viewpoints of the acceptability of the intervention components and outcome measures. A comprehensive framework for designing and reporting process evaluation of RCTs will be employed [48], which including the changes of outcome variables, the safety, acceptability and satisfactory of intervention implementation. Upon completion of the last intervention session of the 16-week period, participants in two intervention groups will be asked to complete the Questionnaire of Process Evaluation and the Exercise Acceptability Questionnaire. The quality and data review for auditing trial conduct will conduct every 6 months by sponsor with a review of all source documents and a review of data entry. Statistical analysis SPSS 29.0 and Mplus 7 will be employed for data analysis. Diagnostic tests (e.g., outlier detection and distribution examination) will be conducted for all data prior to the main analysis. Skewed data of continuous variables will be log-transformed or replaced with median values prior to the data analyses. Missing data (missing at random) will be addressed with multiple imputation approach with chained equations, except for the dropouts (attrition under 30%) that will be imputed with the last observed values. Sensitivity testing (per-protocol analysis) will be employed to detect the impact of missing data and attrition. Intention-to-treat principles will be used for the primary analysis. Independent samples t tests, F tests, and Chi square tests will be applied to compare the baseline characteristics before the intervention (T1). A series of generalized linear mixed models will be employed to evaluate the intervention effects on outcome measures, with time, groups, and their interaction as fixed effects with individuals as random effects. The baseline values will be controlled for all analyses. In addition, structural equation modeling will be employed to analyze mediating effects (CN) of intervention effectiveness, using the 95% bias-corrected bootstrap approach (5000 resamples). The significance level will be set as 95% (two-tailed). The results will be reported following the guide of CONSORT checklist. Pilot study A 4-week pilot study of the blended indoor and outdoor MSE program will be conducted to test the adaptability and feasibility of the intervention as well as the data collection instruments in older adults. 12 participants will be recruited from one community elderly center in Hong Kong. They will be asked to complete all measurements (questionnaires, fitness test and saliva collection) and a 4-week blended indoor and outdoor MSE course. The 4-week pilot study (1 indoor MSE session + 1 outdoor MSE session per week) will include all the movements of three components of MSE in the main intervention but shrink the week duration compared to the main intervention. The detailed exercise content of the pilot study can be found in Table 2. Amendments will be made where necessary. The participants in the pilot study will not be involved in the main study. Time schedule of the study The proposed study will be completed in 24 months, as shown in Figure 2 (additional file 1). Discussion This study aims to compare the effects of blended indoor and outdoor MSE group, indoor-only MSE group and control group on depressive symptoms, physical fitness and PA enjoyment for non-clinical Hong Kong older adults. Moreover, the mediating role of CN in the relationship between MSE program and depressive symptoms will also be assessed. Given that numerous evidence have demonstrated exercise as an effective way can significantly buffer older adults’ depressive symptoms and promote their physical fitness [10, 11], it is expected that participants in both two intervention groups (IG-1 & IG-1) would have significant improvements on depressive symptoms, physical fitness and PA enjoyment compared with participants in the control group. More importantly, considering the high relevance between nature and mental health, and additional benefits may be provided by natural environment for the improvement of older adults’ depressive symptoms [21], we are also expected the IG-1 would have more improvements on these outcomes than IG-2. Furthermore, a previous study proved the partial mediating role of CN between outdoor exercise engagement and wellbeing [26], we assume CN would mediate the effectiveness of the MSE intervention (IG-1=1; IG-2=0) on depressive symptoms in this study. To the best of our knowledge, this study will take the initiative to implement the blended indoor and outdoor MSE intervention catering older adults with depressive symptoms. More effective alternatives for the treatment and improvement of depressive symptoms in non-clinical community-dwelling older adults have been widely concerned by many stakeholders. This study will make relevant contributions in the following aspects: The blended MSE program combining aerobic, muscular strength and balance trainings in indoor and outdoor settings will provide a new mode of exercise intervention on buffering older adults’ depressive symptoms, and the findings will add new knowledge and evidence for the application and validation of this blended environment exercise intervention for the studies of geriatric depression. In addition, the mediating effect of CN will reveal the psychological mechanisms by which the effect of blended indoor and outdoor MSE program on the improvement of older adults’ depressive symptoms, and it will also highlight the role of nature during the outdoor exercise. Furthermore, the knowledge of blended indoor and outdoor MSE program will be transferred to the practice in the community to bring health benefits to older adults with depressive symptom, including improve their depressive symptoms, loneliness, and promote their physical fitness and PA enjoyment. It will also provide an insight and assistance to future practitioners, including community senior centers, health professionals and social workers as well as policy makers to implement exercise interventions to address older adults’ depressive symptoms and promote their mental health and wellbeing. Regarding the limitations, in light of the limited resources, non-cluster RCT design in this study may lead to contamination between participants in two intervention groups and a control group recruited from the same senior service centers [49]. A cluster RCT for stratified sampling at senior centers level is warranted in the future. Furthermore, only self-reported RPE will be used to monitor whether the exercise intensity is mild to moderate, it may lead to some potential biases, such as recall bias, and self-perception bias. Therefore, using objective device (e.g., Polar sports watches) to monitor participants' exercise consumption to control exercise intensity consistency between the two intervention groups is desirable in future studies. In spite of these limitations, this study makes a valuable contribution to non-pharmacological interventions for alleviating depressive symptoms in community-dwelling older adults. As the initiative of exercise intervention in blended environments for community-dwelling older adults with depressive symptoms, this procedure and intervention need to be further tested in other countries to assess whether its effects are generic to a wider area, or whether it should be adapted. Abbreviations MSE: multicomponent structured exercise CN: connectedness to nature PA: physical activity RCT: randomized controlled trial BDNF: brain-derived neurotrophic factor HPA: hypothalamic-pituitary-adrenal SPIRIT: the Standard Protocol Items: Recommendations for Interventional Trials GDS-15: the 15-item Geriatric Depression Scale IG: intervention group CG: control group MMSE: the Mini-Mental Status Examination PAR-Q+: the Physical Activity Readiness Questionnaire for Everyone RPE: The rate of perceived exertion PFA: the Physical Fitness Association of Hong Kong, China Declarations Acknowledgement We would like to express our gratitude to the Food and Health Bureau of Hong Kong SAR who provided us the financial support as well as to the elderly community centers who provided generous assistance in participant recruitment and data collection. Authors’ contributions Conceptualization, Y.D.; methodology, Y.D., S.C., W.M.L., W.L., N.C., K.Y., J,S.B., T.L.; validation, Y.D., and S.C.; formal analysis, S.C., and Y.D.; investigation, Y.D. and S.C.; resources, Y.D ; data curation, S.C., and Y.D.; writing—original draft preparation, S.C., and Y.D.; writing—review and editing, W.M.L., W.L., K.Y., J,S.B., T.L.; supervision, Y.D.; project administration, Y.D.; funding acquisition, Y.D. All authors have read and agreed to the published version of the manuscript. The results will be disseminated to the scientific community and relevant groups via publications in scientific journals, presentations at conferences etc. Funding This study was funded by the Health and Medical Research Fund (HMRF), Food and Health Bureau, Hong Kong SAR (Ref. 05200098). The funders had no role in the study design, data collection and data analyses in the writing of the manuscript or in the decision to submit the manuscript for publication. Ethics approval and consent to participate This study has received an ethics approval from the Research Ethics Committee of Hong Kong Baptist University (ID:REC/21/22/0281). All participants will sign the informed consent before their participation in the study. Consent for publication Not applicable. Informed consent materials will be available from the corresponding author upon request. Availability of data and materials Requests of future data and developed materials should be directed to the corresponding author. Competing interests The authors declare that they have no conflicts of interests. References Baghai TC, Varallo-Bedarida G, Born C, Häfner S, Schüle C, Eser D, et al. Classical risk factors and inflammatory biomarkers: one of the missing biological links between cardiovascular disease and major depressive disorder. International Journal of Molecular Sciences. 2018;19(6):1740. Santomauro DF, Herrera AMM, Shadid J, Zheng P, Ashbaugh C, Pigott DM, et al. 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Gordon BR, McDowell CP, Hallgren M, Meyer JD, Lyons M, Herring MP. Association of efficacy of resistance exercise training with depressive symptoms: meta-analysis and meta-regression analysis of randomized clinical trials. JAMA psychiatry. 2018;75(6):566-76. Feldman R, Schreiber S, Pick C, Been E. Gait, balance and posture in major mental illnesses: depression, anxiety and schizophrenia. Austin Medical Sciences. 2020;5(1):1-6. Mahmoudi A, Amirshaghaghi F, Aminzadeh R, Mohamadi Turkmani E. Effect of aerobic, resistance, and combined exercise training on depressive symptoms, quality of life, and muscle strength in healthy older adults: a systematic review and meta-analysis of randomized controlled trials. Biological Research For Nursing. 2022;24(4):541-59. Eigenschenk B, Thomann A, McClure M, Davies L, Gregory M, Dettweiler U, et al. Benefits of outdoor sports for society. A systematic literature review and reflections on evidence. 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Journal of Environmental Psychology. 2023:102085. van den Bosch M, Meyer-Lindenberg A. Environmental exposures and depression: biological mechanisms and epidemiological evidence. Annual review of public health. 2019;40:239-59. Bratman GN, Anderson CB, Berman MG, Cochran B, De Vries S, Flanders J, et al. Nature and mental health: An ecosystem service perspective. Science advances. 2019;5(7):eaax0903. Mayer FS, Frantz CM, Bruehlman-Senecal E, Dolliver K. Why is nature beneficial? The role of connectedness to nature. Environment and behavior. 2009;41(5):607-43. Salatto RW. The Effects of Green Exercise on Perception and Connectedness to Nature: University of Nevada, Las Vegas; 2021. Berman MG, Kross E, Krpan KM, Askren MK, Burson A, Deldin PJ, et al. Interacting with nature improves cognition and affect for individuals with depression. Journal of affective disorders. 2012;140(3):300-5. Lackey NQ, Tysor DA, McNay GD, Joyner L, Baker KH, Hodge C. Mental health benefits of nature-based recreation: a systematic review. Annals of Leisure Research. 2021;24(3):379-93. Loureiro A, Veloso TJ. Outdoor exercise, well-being and connectedness to nature. Psico. 2014;45(3):299-304. Yu Wong SKI. The effects of a multi-system balance training programme on improving balance, gait and functional performance in people with Parkinson's disease: a randomized controlled trial with 12-month follow-up. 2016. Cheng S-T, Chan A. A brief version of the geriatric depression scale for the chinese. Psychological Assessment. 2004;16(2):182. Chiu HF, Lee H, Chung W, Kwong P. Reliability and validity of the Cantonese version of Mini-Mental State Examination. East Asian Archives of Psychiatry. 1994;4(2):25. Bellon JA, Conejo-Ceron S, Sanchez-Calderon A, Rodriguez-Martin B, Bellon D, Rodriguez-Sanchez E, et al. Effectiveness of exercise-based interventions in reducing depressive symptoms in people without clinical depression: systematic review and meta-analysis of randomised controlled trials. The British Journal of Psychiatry. 2021;219(5):578-87. Lacharité-Lemieux M, Brunelle J-P, Dionne IJ. Adherence to exercise and affective responses: comparison between outdoor and indoor training. Menopause. 2015;22(7):731-40. Excellence TNIfHaC. Exercise for depression: Health Scotland; 2023 [updated Jan. 4 2023. Available from: https://www.nhsinform.scot/healthy-living/mental-wellbeing/low-mood-and-depression/exercise-for-depression/. Catalan-Matamoros D, Gomez-Conesa A, Stubbs B, Vancampfort D. Exercise improves depressive symptoms in older adults: an umbrella review of systematic reviews and meta-analyses. Psychiatry research. 2016;244:202-9. Chodzko-Zajko W, Medicine ACoS. ACSM's exercise for older adults: Lippincott Williams & Wilkins; 2013. Chung P, Zhao Y, Quach B, Liu J, editors. The Use of the Cantonese Rating of Perceived Exertion Scale in Older People. Proceedings of the 12th SCSEPF Annual Conference; 2013. Zivin K, Kales HC. Adherence to depression treatment in older adults: a narrative review. Drugs & aging. 2008;25(7):559-71. Zhang C, Zhang H, Zhao M, Chen C, Li Z, Liu D, et al. Psychometric properties and modification of the 15-item geriatric depression scale among Chinese oldest-old and centenarians: a mixed-methods study. BMC geriatrics. 2022;22(1):144. Milrad SF, Hall DL, Jutagir DR, Lattie EG, Czaja SJ, Perdomo DM, et al. Depression, evening salivary cortisol and inflammation in chronic fatigue syndrome: a psychoneuroendocrinological structural regression model. International journal of psychophysiology. 2018;131:124-30. Rikli RE, Jones CJ. Senior fitness test manual: Human kinetics; 2013. Chung P-K, Leung K-M. Psychometric properties of eight-item physical activity enjoyment scale in a Chinese population. Journal of aging and physical activity. 2019;27(1):61-6. Li N, Wu J. Revise of the connectedness to nature scale and its reliability and validity. China Journal of Health Psychology. 2016;24(9):1347-50. Mayer FS, Frantz CM. The connectedness to nature scale: A measure of individuals’ feeling in community with nature. Journal of environmental psychology. 2004;24(4):503-15. Leung GTY, de Jong Gierveld J, Lam LCW. Validation of the Chinese translation of the 6-item De Jong Gierveld Loneliness Scale in elderly Chinese. International psychogeriatrics. 2008;20(6):1262-72. Grant A, Treweek S, Dreischulte T, Foy R, Guthrie B. Process evaluations for cluster-randomised trials of complex interventions: a proposed framework for design and reporting. Trials. 2013;14:1-10. Sanson-Fisher RW, Bonevski B, Green LW, D’Este C. Limitations of the randomized controlled trial in evaluating population-based health interventions. American journal of preventive medicine. 2007;33(2):155-61. Tables Table 1. The detailed exercise contents for two intervention groups Physical exercise program 16 -week blended indoor and outdoor MSE intervention group (IG-1) 16 -week indoor-only MSE intervention group (IG-2) Frequency one indoor and one outdoor sessions/week two indoor sessions/week Warm-up • Duration: 10 mins • Exercise: light walking and stretching Aerobic training • Duration: 30 mins • Intensity: RPE 11-13 • Exercise: 1) Session 1/week (indoor) of two IGs: dancing Week 1-2: chair dancing. Week 3-8: dancing without equipment Week 9-16: towel dancing 2) Session 2/week: nature walking Session 2/week: indoor walking Muscular strength training • Duration: 20 mins • Intensity: RPE 11-13 • Volume of each exercise: 2 sets, 8-12 repetitions per set, with 1–2 minute rest intervals (depending on participants’ physical capacity) • Exercise Week 1-4: four movements including squats, wall push-ups, toe stands, biceps curl ( to strengthen body slowly and gently using only own body weight ). Week 5-12: six movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press ( using own body weight and resistance band ). Week 13-16: eight movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press, knee extension, knee curl ( using own body weight and resistance band and adjustable ankle weights ). Postural balance training • Duration: 20 mins • Exercise: Week 1-6: exercise without equipment. Week 7-16: exercise with equipment (Yoga mini balls) • Eight movements performed in standing and hands-and-knees positions, including walking in place, free-leg swinging, weight shift in all directions, stepping exercises, tandem walking, maintaining a hands-and-knees position while raising either an upper or lower limb or one upper and the opposite lower limb Cool-down • Duration: 10 mins • Exercise: stretching and mind-body breathing Table 2. The protocol of 4-week pilot study Physical exercise program The 4-week blended indoor and outdoor MSE intervention group Frequency one indoor + one outdoor sessions/week Warm-up • Duration: 10 mins • Exercise: light walking and stretching Aerobic training • Duration: 30 mins • Intensity: RPE 11-13 • Exercise: 1) Session 1/week (indoor): dancing Week 1: chair dancing. Week 2: dancing without equipment Week 3: towel dancing Week 4: towel dancing 2) Session 2/week (outdoor): nature walking Muscular strength training • Duration: 20 mins • Intensity: RPE 11-13 • Volume of each exercise: 2 sets, 8-12 repetitions per set, with 1–2-minute rest intervals (depending on participants’ physical capacity) • Exercise Week 1: four movements including squats, wall push-ups, toe stands, biceps curl ( to strengthen body slowly and gently using only own body weight ). Week 2: six movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press ( using own body weight and resistance band ). Week 3-4: eight movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press, knee extension, knee curl ( using own body weight and resistance band and adjustable ankle weights ). Postural balance training • Duration: 20 mins • Exercise: Week 1-2: exercise without equipment. Week 3-4: exercise with equipment (Yoga mini balls) • Movements: eight exercises performed in standing and hands-and-knees positions, including walking in place, free-leg swinging, weight shift in all directions, stepping exercises, tandem walking, maintaining a hand-and- knees position while raising either an upper or lower limb or one upper and the opposite lower limb Cool-down • Duration: 10 mins • Exercise: stretching and mind-body breathing Pictures Pictures 1 and 4 are available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files Picture1.jpg Picture.1 The indoor activity room of the gymnasium (source: https://fitz.hk/life/local/彩榮路體育館12-29開幕%EF%BC%8E實地視察-落雨跑步唔使擔遮/) Picture2.jpg Picture.2 Natural environment with dense vegetation in Kowloon Park Picture3.jpg Picture.3 Jogging track in Kowloon Park Picture4.jpg Picture.4 Loggia in Kowloon Park Cite Share Download PDF Status: Published Journal Publication published 14 Nov, 2025 Read the published version in BMC Public Health → Version 1 posted Editorial decision: Revision requested 18 Sep, 2024 Submission checks completed at journal 19 Apr, 2024 Editor assigned by journal 19 Apr, 2024 First submitted to journal 16 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Park\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4274102/v1/c5986ab07103a9c66c4678cd.jpg"},{"id":55517626,"identity":"20ad57e4-bf0d-41ef-a5c3-4b5c51641c07","added_by":"auto","created_at":"2024-04-29 13:26:19","extension":"jpg","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":303827,"visible":true,"origin":"","legend":"\u003cp\u003ePicture.3 Jogging track in Kowloon Park\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4274102/v1/d9d8911fb1d949cb7e2be27f.jpg"},{"id":55517625,"identity":"337b4654-9c22-46d0-a203-afb79fb27532","added_by":"auto","created_at":"2024-04-29 13:26:19","extension":"jpg","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":277005,"visible":true,"origin":"","legend":"\u003cp\u003ePicture.4 Loggia in Kowloon Park\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4274102/v1/e692d5a512d27ec9d9d95d78.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"The effect of a blended indoor and outdoor multicomponent structured exercise program on depressive symptoms in Hong Kong older adults: study protocol of a randomized controlled trial","fulltext":[{"header":"Background","content":"\u003cp\u003eDepression is a common mental health problem often occurring in older adults, and it is also a major risk factor for disability and death in older adults [1, 2]. Among the estimated 280 million individuals affected by depression globally, those with the age over 60 years old occupied nearly 5.7% [3]. Moreover, a previous study indicated a high prevalence rate of depressive symptoms (around 30%) among older adults in Hong Kong [4]. The prevalence of depressive symptoms among Hong Kong older adults have been aggravated during the COVID-19 pandemic leading to 43.7% for males and 54.8% for female [5]. Older adults who suffer from depressive symptoms may lead to several negative consequences on their physical and mental health, which includes anxiety, insomnia, vague somatic pains, poor quality of life, cognitive decline, social isolation, and recurrent thoughts of death or suicide [6, 7, 8]. In addition, older population with mild and severe depressive symptoms may require and use more medical services but use fewer social or recreational services than those without depressive symptoms [9]. Therefore, improving depression among Hong Kong older adults is a public health and economic imperative.\u003c/p\u003e\n\u003cp\u003eExercise has been demonstrated as an effective way to buffer older adults\u0026rsquo; depressive symptoms from numerous evidence [10, 11]. It is attributed to some physiological changes, such as stimulating the release of endorphins [12], increasing the production of brain-derived neurotrophic factor (BDNF) [13], regulating hypothalamic-pituitary-adrenal (HPA) axis and reducing cortisol level [14]. In addition, the majority of RCT examining physical exercise on depression have mainly focused on conducting structured exercise. Three systematic reviews have revealed that the aerobic exercise (e.g., walking, dancing) [15], muscular strength training (resistance training) [16], and balance training [17], as three key exercise components of structured exercise, can significantly improve depressive symptoms of middle-aged and older adults respectively. Moreover, a recent systematic review has highlighted that exercise programs combining aerobic training and resistance training have a greater improvement on older adults\u0026rsquo; depressive symptoms than only adopting one exercise components [18]. However, most of existing related RCTs just comprise of one or two exercise components of structured exercise and focus on the clinical patients associated with major depression. There is limited research combining all three key exercise components in an exercise program and targeting non-clinical older adults with depressive symptoms.\u003c/p\u003e\n\u003cp\u003eOver the past two decades, more attention has been paid to the role of nature, and the benefit of outdoor exercise on human health in the past two decades. A growing body of evidence have illustrated that exercise in a natural environment (green exercise) can provide greater physiological and psychological benefits compared to indoor exercise [19, 20]. It may provide the double beneficial effect on depression improvement via promoting a greater feeling of revitalization, and enjoyment [21, 22]. There are several mechanisms can justify the effect of natural environment on depression. From the perspectives of biology and physiology, exposing to nature is associated with biological stress recovery [23]. In the brain, nature exposure is linked to reduced lateral prefrontal activation, which is associated with less rumination, a common symptom in depression [24]. Furthermore, nature exposure is also related to perceptual fluency (the ease with which a stimulus is processed in the brain), where individuals seem to prefer the type of fractal patterns (having high internal repetition of visual information) that are displayed in nature, responding to those with stress relief, as compared with nonnatural, or nonfractal patterns [24]. From the psychological perspective, mental health benefits from exposure to natural environments occur through a sense of belonging, embeddedness and connection to nature, which is linked to the concept of connectedness to nature (CN) [25].\u003c/p\u003e\n\u003cp\u003eCN, \u0026nbsp;as a trait, is defined as the individual\u0026rsquo;s experiential sense of oneness with the natural world [26]. Numerous evidence have shown that outdoor exercise engagement is associated with CN [27]. Several longitudinal studies have shown that CN is one of a key predictor of mental health, and individual who feel stronger connection with nature are more likely to have more positive emotions and less depressive symptoms [28, 29]. However, the partial mediating role of CN was only investigated by a cross-sectional study [26], and CN as a mediators in the effect of green exercise on depression has not been sufficiently examined using RCTs.\u003c/p\u003e\n\u003cp\u003eAlthough exercising in natural environment have already shown the improvement effect of depression, existing studies of structured exercise programs for older adults with depressive symptoms were mainly conducted in the lab or indoor environment [20]. Compared with outdoor exercise which is easily influenced by the weather and with low access of available facilities, indoor exercise is more comfortable, quiet, and convenient to operate, especially for older adults [20]. Considering the high relevance between nature and mental health, the combination of indoor and outdoor exercise programs might be able to maximize intervention effectiveness while maintaining the benefits for each type of intervention. However, there were few empirical evidence on the blended indoor and outdoor exercise program. Only one cross-sectional study revealed that adults who combine outdoor with indoor exercise reported more psychological well-being related with exercise than those taking indoor exercise [30]. Only one RCT study supported the effects of a\u0026nbsp;8-week blended indoor-outdoor balance training programme on improving balance, gait and functional performance\u0026nbsp;in patient with Parkinson\u0026apos;s disease [31]. Therefore, more RCT studies of exercise program\u0026nbsp;conducted in both indoor and outdoor settings among non-clinical older adults with depressive symptoms are needed. Furthermore, the potential psychological mechanism of the intervention should be\u0026nbsp;explored.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAim of\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003ethe current study\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe aim of this study is to develop and examine a blended indoor and outdoor MSE program on depressive symptoms, physical fitness and PA enjoyment in Hong Kong community-dwelling older adults with depressive symptoms. Five hypotheses will be tested in this study: (a) The intervention groups (IG-1: the blended indoor and outdoor MSE intervention group; IG-2: indoor-only MSE intervention group) would improve depressive symptoms (determined by the 15-item Geriatric Depression Scale) greater than the control group (CG). IG-1 would also improve depressive symptoms more than IG-2. (b) The intervention groups (IG-1 \u0026amp; IG-2) would decrease concentration of salivary cortisol more than CG. IG-1 would also decrease concentration of salivary cortisol more than IG-2. (c) The intervention groups (IG-1 \u0026amp; IG-2) would improve physical fitness more than CG. (d) The intervention groups (IG-1 \u0026amp; IG-2) would improve PA enjoyment more than CG. IG-1 would also improve PA enjoyment more than IG-2. (e) CN would mediate the effectiveness of the MSE intervention (IG-1=1; IG-2=0) on depressive symptoms.\u003c/p\u003e"},{"header":"Methods and design","content":"\u003cp\u003e\u003cstrong\u003eStudy design\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study is a single-blind three-arm parallel RCT approved by the Research Ethics Committee of Hong Kong Baptist University (ID:REC/21/22/0281) and registered in the ClinicalTrials.gov (NCT06190327). This protocol follows the standardized guidelines proposed by the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT). Participants will be recruited from community senior service centers in Hong Kong, where all older adults are community-dwelling residents. All eligible participants will be randomly assigned into three groups: (a) IG-1: the blended indoor and outdoor MSE intervention group; (b) IG-2: indoor-only MSE intervention group; (c): CG: control group, using the random function available in Excel software, in a ratio of 1:1:1. Assessments will be conducted at pre-intervention (T1: immediately after the eligibility assessment), post-intervention (T2: immediately after 16-week intervention), 3-month follow up (T3: 3 month after intervention the end of the intervention). Assignments will be blinded to the assessors until all tests are finished.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy population\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOlder adults will be involved in this study if they: 1) are aged 60-74 years living in the community. 2) no contraindications for physical exercise (e.g., physical disability, unstable cardiovascular diseases, etc.). 3) scoring 5-15 using 15-item Geriatric Depression Scale (GDS-15) [32] (i.e., mild, moderate, and severe level of depressive symptoms). 4) able to communicate in Cantonese. Participants will be excluded if they: 1) suffer from cognitive impairment identified by the Chinese version of the Mini-Mental Status Examination (MMSE) (i.e., score \u0026lt; 24) [33]; 2) fail to pass the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+) screening or without the physician\u0026rsquo;s approval for the readiness of participation in the moderate-intensity exercise. 3) have\u0026nbsp;history of a clinical diagnosis of depression and receiving relevant treatment. 4) are attending other health projects related to physical exercise.\u003c/p\u003e\n\u003cp\u003eSample size was calculated by G*Power software (version 3.1.9.6) with MANOVA with repeated measures. Based on the previous meta-analysis examine the effect of exercise intervention on people with non-clinical depressive symptoms (Cohen\u0026apos;s d=0.34) [34] and a study compared the effect of the combined exercise (aerobic + resistance) on depression for postmenopausal women in outdoor setting to it conducted in indoor setting (Cohen\u0026apos;s d=0.44) [35], an average small effect size (Cohen\u0026rsquo;s d) of 0.34 is used in the present study to achieve adequate power. Assuming a statistical power (1-\u0026beta;) of 80%, \u0026alpha; of 0.05, and approximately 20% dropout rate, a total of 129 participants (43 in each arm) will be required to achieve a robust evaluation of treatment effects.\u003c/p\u003e\n\u003cp\u003eParticipants will be recruited from community senior service centers in Hong Kong. Advertisement of this program will be distributed by the manager of the senior center to all senior members via social media (e.g. WhatsApp groups, Facebook), seniors\u0026apos; group meetings, and bulletin boards. If interested, potential participants will be able to register their details.\u003c/p\u003e\n\u003cp\u003eAfter registration, the GDS-15 with Chinese version [32] will be adopted to screen out those with depressive symptoms. Participants who score less than five will be excluded. If participants suffer from cognitive impairment identified by MMSE [33] screening with the score less than 24, will also be excluded. Moreover, if participants answer \u0026ldquo;yes\u0026rdquo; to any of the items of PAR-Q+ screening, they will be required to obtain medical approval from their general practitioner before involving in this exercise program.\u003c/p\u003e\n\u003cp\u003eEligible participants will attend the baseline assessment (T1) at community senior service centers close to their area of residence. Investigator will introduce the study procedures individually to them, and all questions will be clarified. And then, they will be asked to sign an informed consent form before the commencement of the intervention, and authorize the research team to anonymously record, analyze, and use their data for academic purposes. Figure 1 shows the flowchart of participants from recruitment and allocation in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIntervention\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere will be four steps at the preparation stage of intervention development. Step 1: a steering group, consisting of key stakeholders who are involved in this program (i.e., elderly participants, manager of senior service center, exercise coach, and research team members), will be formed to develop intervention content, optimize the intervention components, to identify the facilitators and barriers for the intervention implementation, and to formulate strategies for maintaining participants\u0026rsquo; engagement and adherence. Step 2: a one-month pilot study for blended indoor and outdoor MSE intervention group (IG-1) will be implemented to test and optimize the strategies and relevant materials. Participant recruitment, instruments, data collection, adaptability and feasibility of the intervention will be sufficiently considered in the pilot study.\u0026nbsp;Step 3:\u0026nbsp;a comprehensive plan of the intervention implementation will be established to guarantee the safety, effectiveness, supportiveness and enjoyment of the intervention implementation. An operational manual will also be constructed in this step.\u0026nbsp;Step 4:\u0026nbsp;an evaluation plan for the effectiveness of intervention implementation will be developed. Any amendments will be made if necessary.\u003c/p\u003e\n\u003cp\u003eIn addition, a briefing session will be provided for all eligible participants in senior service centers, participants will receive detailed information about the exercise program in which they are enrolled (e.g., study procedure, schedule). Furthermore, another briefing session with a mock test for student helpers (major in sport science) also will be arranged one to two weeks before the pre-test to introduce the details of data collection and intervention implementation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eIntervention settings\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eParticipants in 16-week blended indoor and outdoor MSE intervention group (IG-1) will engage in one indoor exercise session and one outdoor session in each week, while those who are randomly assigned to 16-week indoor-only MSE intervention group (IG-2) will engage in two indoor exercise sessions in each week. Regarding the intervention setting, the indoor exercise session will be conducted in the activity room of the government sports center, which is around 150 square meters in size (see Picture 1). The outdoor exercise session will be held in an urban park namely Kowloon Park, which has outdoor facilities including a jogging track, a large open space with seats around and loggia. All these outdoor facilities are in the green natural environment (see Picture 2 to Picture 4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eExercise prescription\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBased on the British National Institute for Health and Care Excellence guidelines [36] and previous studies [34, 37], effective exercise training programs for older adults with depressive symptoms are generally 10-16 weeks with 2-3 sessions/week (\u0026ge; 45 min/session). Thus, this study will adopt a modest dose of intervention, including 16 weeks with 2 sessions/week (90 minutes/session). As the exercise mode of this study will be MSE combining aerobic, muscular strength and balance trainings, each 90-min session will consist of 10-min warm-up, 30-min aerobic training, 20-min muscular strength training, 20-min postural balance training, and 10-min cool-down. Both two intervention groups (IG-1 \u0026amp; IG-2) will be delivered safely and effectively by qualified coach recommended by the Physical Fitness Association of Hong Kong, China (PFA) with professional monitoring.\u003c/p\u003e\n\u003cp\u003eAccording to the guidelines introduced by \u0026ldquo;ACSM\u0026rsquo;s Exercise for Older Adults\u0026rdquo; [38] and advice of PFA, the prescription of exercise programs for the two intervention groups will be formed (as shown in Table 1). First, a 10-min warm up (e.g. light walking and stretching) will be conducted. During the aerobic training, session 1/week of two intervention groups will conduct dancing via using chairs and towel, while session 2/week of two intervention groups will conduct walking (IG-1: outdoor walking in urban park, IG-2: indoor walking). As for the muscular strength training, weights (resistance) will be derived from participants\u0026rsquo; own bodies, resistance band (15 pounds \u0026amp; 25 pounds), and adjustable ankle weights (0.5kg, 1kg, 2kg). The intensity of both aerobic training and muscular strength training will be light to somewhat hard (The rate of perceived exertion (RPE) 11 to 13, using the Cantonese version) [39]. Each participant will be required to report their RPEs during the aerobic and muscular strength training sessions. During postural balance training, there will be no restricted intensity, but the difficulty level of exercise will be increased from performing balance exercise without equipment (week 1-6) to with equipment (25cm Yoga mini balls) (week 7-16). Adjustment of training intensity and difficulty will be made in accordance with individual\u0026rsquo;s fitness level, and adaptability of the training. To ensure the safety and effectiveness of this exercise program, each intervention group will be separated into two sub-groups, with maximum 22 participants in each sub-group. It means that 2 sub-groups of 2 intervention groups will be conducted in separate timeslots but taught by the same coach at the same venue to ensure both sub-groups will receive similar teaching and learning quality. Participants in both two intervention groups will not be required to change their usual care pathways (e.g., medication use), and all interventions will be delivered while maintaining their original lifestyles.\u003c/p\u003e\n\u003cp\u003eIn order to strengthen the CN of IG-1 participants during the outdoor exercise session at Kowloon Park, the following strategies will be employed. During the 10-min warm up, the coach will lead participants executing light walking and stretching while guiding them to focus on their sensory experience during the exercise. Such as looking at the green vegetation around themselves and the sunlight falling through the gaps in the leaves (visual sense), listening to the birds singing from nature and the wind rustling through the leaves (auditory sense), smelling the fresh air mixed with grass and soil (olfactory sense), and feeling the touch of the breeze on the skin (tactile sense).\u003c/p\u003e\n\u003cp\u003eDuring the\u0026nbsp;aerobic training section,\u0026nbsp;IG-1 participants will engage in a 30-minute nature walking along a trail surrounded by greenery. The walking route will circle an artificial lake and pass through some gentle ascents and descents in the terrain. During the nature walking, the coach will guild participants to interact with nature, including touching leaves and flowers and listening the sound of waterfalls and birds to deepen the immersion in the natural environment.\u003c/p\u003e\n\u003cp\u003eDuring the muscular strength training and balance training, sounds from nature will be used as background music, and participants\u0026rsquo; auditory senses will be stimulated\u0026nbsp;and reinforced. The coach will ask\u0026nbsp;all participants a question\u0026nbsp;\u0026ldquo;When you perform the exercise, do\u0026nbsp;you hear the birds singing from nature and the wind rustling through the leaves?\u0026rdquo;\u0026nbsp;during strength training section and balance training section, respectively. All participants will be asked to report their answers (\u0026ldquo;Yes\u0026rdquo; or \u0026ldquo;No\u0026rdquo;) to the student helper. If participant\u0026rsquo;s answer is \u0026ldquo;No\u0026rdquo;, the student helper will remind the participant to focus on his/her\u0026nbsp;auditory senses\u0026nbsp;in the natural environment.\u003c/p\u003e\n\u003cp\u003eLastly, during the 10-minute cool down at the end of the outdoor MSE session, in addition to stretching, the coach will guide the participants to close their eyes with mind-body breathing to reflect on what they\u0026nbsp;just have seen and felt during the exercise session in natural environment, such as the smell of soil and vegetation, the sound of waterfall, the feeling of touching the leaves and the color of flowers. By implementing these strategies, a stronger connection with nature can be promoted among participants in IG-1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSafety considerations and adverse events\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;for two exercise groups\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring outdoor exercise session, if it rains and the rainfall is light or intermittent, participants can walk on the jogging track holding an umbrella and perform muscular strength and balance trainings in the open space of the park with loggia (see Picture 4). In case of the extreme weather conditions, such as yellow rainstorm warning or above issued by the Observatory, and extreme heat (above 30\u0026deg;C), the outdoor exercise session may be notified of cancellation in advance or rescheduled if deemed unsafe by the tutor. All outdoor sessions will be scheduled in the morning to avoid stronger sunlight and uncomfortable temperatures. Moreover, the researchers or coach will encourage and remind participants the night before each outdoor session to bring their plenty of water, towels, hat, sunglasses, and an alternative clothing.\u003c/p\u003e\n\u003cp\u003eIn response to sports injuries during indoor and outdoor exercise sessions, the first aid box will be prepared on-site. In addition, the coach and student helpers (major in sport science) who involving in this study all have first-aid certificates and equipped with knowledges and skills about sports injury prevention and preliminary treatment. \u0026nbsp;They are capable to handle any sports injury issue among participants during this time. All adverse events reported by the participant will be recorded.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eControl group\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eParticipants randomly allocated to the CG will not receive any intervention during the whole program (16-week treatment and 3-month follow-up), and they will be required to maintain their current lifestyles. To monitor the control condition, participants will need to keep diaries to record their daily physical exercise, mood, medicines used, illness and participation in other health-related activities. The research assistant will biweekly give telephone calls to the participants to check their diaries and identify if they change their lifestyles or experience adverse events.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eParticipant retention strategies\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeveral effective strategies will be adopted for participant retention based on previous studies on depression treatment for older adults [40]. 1) emphasizing study benefits and promote positive attitudes for participating in this program (e.g., expected health outcomes, free tests of physical fitness). The results of each assessment will be compiled into a health report to be provided as feedback to the participants; 2) designing the intervention components according to the Safety, Supportive, Active, and Enjoyable principles (e.g., group-based, diverse exercise mode, utility of music and equipment); 3) applying several behavioral change techniques that facilitate the maintenance of participation during the intervention implementation (e.g., positive persuasion, social support, verbal encouragement, message reminder prior to the intervention session); and 4) providing financial incentives for completing all measurements of outcomes (HK$300 supermarket coupons for each participant). The retention strategies will be discussed with all relevant stakeholders who are the members of the steering group. Amendments will be made if necessary.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOutcome\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;evaluation of the intervention\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData collection for all tests will be done by the researchers. All participants will be informed that the data obtained during the program will be stored in a computer and will be treated confidentially. Identification code will be used to identify each participant. Data entry will be handled by two other researchers in the research team. For this protocol, Data monitoring committee (DMC) is not needed as it is a low-risk study with short intervention duration.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePrimary outcome\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDepressive symptoms\u003c/em\u003e: The Chinese version of the 15-item Geriatric Depression Scale (GDS-15) [32] will be used to measure subjective depression levels. The GDS-15, as an effective measure of depressive symptoms in older adults, has been shown to have good reliability and validity in Chinese older adults [32, 41]. Answers will be given on a yes/no scale. Sample items will include \u0026ldquo;Are you basically satisfied with your life?\u0026rdquo; and \u0026ldquo;Do you prefer to stay at home, rather than going out and doing things?\u0026rdquo; in past week. The total score ranges from 0 to 15, where 0-4 = normal, 5-8 = mild depressive symptoms, 9-11 = moderate depressive symptoms and 12-15 = severe depressive symptoms. Assessments will be conducted at T1, T2 and T3.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSecondary outcomes\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSalivary cortisol:\u0026nbsp;\u003c/em\u003eSalivary cortisol will be measured as a biomarker for depressive symptoms. All participants will be provided with two salivate tubes and asked to collect the saliva samples (2-3ml) at awakening, and 30 min after awakening respectively on the next day. Participants will be instructed to rinse their mouth with normal saline but abstain from eating, drinking, or brushing their teeth prior to saliva collection. Participants will use passive drool method to collect saliva naturally in the mouth for 60 seconds before dribbling the saliva into containers. Following the collection of samples, participants will be instructed to record the exact time of collection on the label and freeze the salivate tubes in their home refrigerator (0-4 ℃)\u0026nbsp;to keep the salivary cortisol stable until transport to the research lab. All the uncentrifuged saliva samples will then be transported and stored at -20℃\u0026nbsp;until analyses. Saliva will be assayed for cortisol (\u0026mu;g/dL) concentrations by a registered laboratory using a Salimetric high sensitivity ELISA kit [42]. The inter assay coefficients of variation (based on low- and high-control samples) is set at 5% for cortisol. Assessments will be conducted at T1, T2 and T3.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ePhysical fitness:\u003c/em\u003e Physical fitness will be assessed using the Senior Fitness Test (SFT) Manual [43], which includes body mass index (BMI), 30s chair stand, 30s arm curl, 2min step test, chair sit-and-reach test, back scratch test and 8ft up-and-go test, to measure muscular strength, aerobic endurance, flexibility, agility and dynamic balance for older adults. This validated instrument is reliable with an intra-class correlation coefficient (ICC) ranged from 0.8 to 0.98. Assessments will be conducted at T1, T2 and T3.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ePhysical activity enjoyment:\u0026nbsp;\u003c/em\u003eThe Chinese version of the 8-item physical activity enjoyment scale (PACES) [44] will be adopted to measure participant\u0026rsquo;s enjoyment level after engaging in blended indoor and outdoor MSE program. This scale has revealed strong internal consistency and reliability among Hong Kong older adults (Cronbach\u0026apos;s alpha=0.92). It will be scored by 7 bipolar rating, from one extreme to the other extreme, for example, from \u0026ldquo;it\u0026rsquo;s very pleasant\u0026rdquo; to \u0026ldquo;it\u0026rsquo;s very unpleasant\u0026rdquo;. Assessments will be conducted at T1, T2 and T3.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConnectedness to nature (CN) (mediator):\u003c/em\u003e CN will be measured using the 14-item connectedness to nature scale with Chinese version [45] to assess the sense of belonging to the natural world. The original scale was developed by Mayer \u0026amp; Frantz [46] with sound reliability (Cronbach\u0026apos;s alpha=0.84). This five-point scale, ranging from 1 \u0026ldquo;strongly disagree\u0026rdquo; to 5 \u0026ldquo;strongly agree\u0026rdquo;. Sample items will include \u0026ldquo;I often feel like I am only a small part of the natural world around me, and that I am no more important than the grass on the ground or the birds in the trees\u0026rdquo;. Assessments will be conducted at T1, T2 and T3.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eLoneliness (covariate)\u003c/em\u003e: Loneliness will be measured by using the 6-item De Jong Gierveld Loneliness Scale with Chinese version [47]. This scale has been shown a sound reliability and validity for older adults in Hong Kong (Cronbach\u0026apos;s alpha=0.76) [47]. Item 1 to item 3 as negatively worded items will be measured \u0026ldquo;emotional loneliness\u0026rdquo;, answer \u0026ldquo;yes\u0026rdquo; will score 1, answer \u0026ldquo;more or less\u0026rdquo; will score 1, answer \u0026ldquo;no\u0026rdquo; will score 0. Item 4 to item 6 as positively worded items will be used to assessed \u0026ldquo;social loneliness\u0026rdquo;, answer \u0026ldquo;yes\u0026rdquo; will score 0, answer \u0026ldquo;more or less\u0026rdquo; will score 1, answer \u0026ldquo;no\u0026rdquo; will score 1. Sample items will include \u0026ldquo;I experience a general sense of emptiness\u0026rdquo;, and \u0026ldquo;There are many people I can trust completely\u0026rdquo;. Assessments will be conducted at T1.\u003c/p\u003e\n\u003cp\u003eSociodemographic characteristics include name, mobile number, gender, age, educational level, household income, marital status, number of children and living status, will be collected at T1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eProcess evaluation of the intervention\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProcess evaluation will be used to understand and evaluate implementation and participants\u0026rsquo; viewpoints of the acceptability of the intervention components and outcome measures. A comprehensive framework for designing and reporting process evaluation of RCTs will be employed\u0026nbsp;[48], which including the changes of outcome variables, the safety, acceptability and satisfactory of intervention implementation. Upon completion of the last intervention session of the 16-week period, participants in two intervention groups will be asked to complete the Questionnaire of Process Evaluation and the Exercise Acceptability Questionnaire. The quality and data review for auditing trial conduct will conduct every 6 months by sponsor with a review of all source documents and a review of data entry.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSPSS 29.0 and Mplus 7 will be employed for data analysis. Diagnostic tests (e.g., outlier detection and distribution examination) will be conducted for all data prior to the main analysis. Skewed data of continuous variables will be log-transformed or replaced with median values prior to the data analyses. Missing data (missing at random) will be addressed with multiple imputation approach with chained equations, except for the dropouts (attrition under 30%) that will be imputed with the last observed values. Sensitivity testing (per-protocol analysis) will be employed to detect the impact of missing data and attrition. Intention-to-treat principles will be used for the primary analysis.\u003c/p\u003e\n\u003cp\u003eIndependent samples t tests, F tests, and Chi square tests will be applied to compare the baseline characteristics before the intervention (T1). A series of generalized linear mixed models will be employed to evaluate the intervention effects on outcome measures, with time, groups, and their interaction as fixed effects with individuals as random effects. The baseline values will be controlled for all analyses. In addition, structural equation modeling will be employed to analyze mediating effects (CN) of intervention effectiveness, using the 95% bias-corrected bootstrap approach (5000 resamples). The significance level will be set as 95% (two-tailed). The results will be reported following the guide of CONSORT checklist.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePilot study\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA 4-week pilot study of the blended indoor and outdoor MSE program will be conducted to test the adaptability and feasibility of the intervention as well as the data collection instruments in older adults. 12 participants will be recruited from one community elderly center in Hong Kong. They will be asked to complete all measurements (questionnaires, fitness test and saliva collection) and a\u0026nbsp;4-week blended indoor and outdoor MSE course. The 4-week pilot study (1 indoor MSE session + 1 outdoor MSE session\u0026nbsp;per\u0026nbsp;week) will\u0026nbsp;include\u0026nbsp;all the movements of three components of MSE in the main intervention\u0026nbsp;but shrink the week duration compared to the main intervention. The detailed exercise content of the pilot study can be found in Table 2.\u0026nbsp;Amendments will be made where necessary. The participants in the pilot study\u0026nbsp;will not be involved in the main study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTime schedule of the study\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe proposed study will be completed in 24 months, as shown in Figure 2 (additional file 1).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study aims to\u0026nbsp;compare the effects of blended indoor and outdoor MSE group, indoor-only MSE group and control group on depressive symptoms, physical fitness and PA enjoyment for non-clinical Hong Kong older adults. Moreover, the mediating role of CN in the relationship between MSE program and depressive symptoms will also be assessed.\u0026nbsp;Given that numerous evidence have demonstrated exercise as an effective way can significantly buffer older adults\u0026rsquo; depressive symptoms and promote their physical fitness\u0026nbsp;[10, 11], it is expected that participants in both two intervention groups (IG-1 \u0026amp; IG-1) would have significant improvements on depressive symptoms,\u0026nbsp;physical fitness and PA enjoyment compared with participants in the control group. More importantly, considering the high relevance between nature and mental health, and additional benefits may be provided by natural environment for the improvement of older adults\u0026rsquo; depressive symptoms\u0026nbsp;[21], we are also expected the IG-1 would have more improvements on these outcomes than IG-2. Furthermore, a previous study proved the partial mediating role of CN between outdoor exercise engagement and wellbeing\u0026nbsp;[26], we assume CN would mediate the effectiveness of the MSE intervention (IG-1=1; IG-2=0) on depressive symptoms in this study.\u003c/p\u003e\n\u003cp\u003eTo the best of our knowledge, this study will take the initiative to implement the blended indoor and outdoor MSE intervention catering older adults with depressive symptoms. More effective alternatives for the treatment and improvement of depressive symptoms in non-clinical community-dwelling older adults have been widely concerned by many stakeholders. This study will make relevant contributions in the following aspects:\u003c/p\u003e\n\u003cp\u003eThe blended MSE program combining aerobic, muscular strength and balance trainings in indoor and outdoor settings will provide a new mode of exercise intervention on buffering older adults\u0026rsquo; depressive symptoms, and the findings will add new knowledge and evidence for the application and validation of this blended environment exercise intervention for the studies of geriatric depression. In addition, the mediating effect of CN will reveal the psychological mechanisms by which the effect of blended indoor and outdoor MSE program on the improvement of older adults\u0026rsquo; depressive symptoms, and it will also highlight the role of nature during the outdoor exercise. Furthermore, the knowledge of blended indoor and outdoor MSE program will be transferred to the practice in the community to bring health benefits to older adults with depressive symptom, including improve their depressive symptoms, loneliness, and promote their physical fitness and PA enjoyment. It will also provide an insight and assistance to future practitioners, including community senior centers, health professionals and social workers as well as policy makers to implement exercise interventions to address older adults\u0026rsquo; depressive symptoms and promote their mental health and wellbeing.\u003c/p\u003e\n\u003cp\u003eRegarding the limitations,\u0026nbsp;in light of the limited resources, non-cluster RCT design in this study may lead to contamination between participants in two intervention groups and a control group recruited from the same\u0026nbsp;senior service centers\u0026nbsp;[49].\u0026nbsp;A cluster RCT for stratified sampling at senior centers level is\u0026nbsp;warranted\u0026nbsp;in the future.\u0026nbsp;Furthermore, only self-reported RPE will be used to monitor whether the exercise intensity is mild to moderate, it may lead to some potential biases, such as recall bias, and self-perception bias. Therefore, using objective device (e.g., Polar sports watches) to monitor participants\u0026apos; exercise consumption to control exercise intensity consistency between the two intervention groups is desirable in future studies. In spite of these limitations, this study makes a valuable contribution to non-pharmacological interventions for alleviating depressive symptoms in community-dwelling older adults. As the initiative of exercise intervention in blended environments for community-dwelling older adults with depressive symptoms, this procedure and intervention need to be further tested in other countries to assess whether its effects are generic to a wider area, or whether it should be adapted.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eMSE: multicomponent structured exercise\u003c/p\u003e\n\u003cp\u003eCN: connectedness to nature\u003c/p\u003e\n\u003cp\u003ePA: physical activity\u003c/p\u003e\n\u003cp\u003eRCT: randomized controlled trial\u003c/p\u003e\n\u003cp\u003eBDNF: brain-derived neurotrophic factor\u003c/p\u003e\n\u003cp\u003eHPA: hypothalamic-pituitary-adrenal\u003c/p\u003e\n\u003cp\u003eSPIRIT: the Standard Protocol Items: Recommendations for Interventional Trials\u003c/p\u003e\n\u003cp\u003eGDS-15: the 15-item Geriatric Depression Scale\u003c/p\u003e\n\u003cp\u003eIG: intervention group\u003c/p\u003e\n\u003cp\u003eCG: control group\u003c/p\u003e\n\u003cp\u003eMMSE: the Mini-Mental Status Examination\u003c/p\u003e\n\u003cp\u003ePAR-Q+: the Physical Activity Readiness Questionnaire for Everyone\u003c/p\u003e\n\u003cp\u003eRPE: The rate of perceived exertion\u003c/p\u003e\n\u003cp\u003ePFA: the Physical Fitness Association of Hong Kong, China\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to express our gratitude to the Food and Health Bureau of Hong Kong SAR who provided us the financial support as well as to the elderly community centers who provided generous assistance in participant recruitment and data collection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization, Y.D.; methodology, Y.D., S.C., W.M.L., W.L., N.C., K.Y., J,S.B., T.L.; validation, Y.D., and S.C.; formal analysis, S.C., and Y.D.; investigation, Y.D. and S.C.; resources, Y.D ; data curation, S.C., and Y.D.; writing\u0026mdash;original draft preparation, S.C., and Y.D.; writing\u0026mdash;review and editing, W.M.L., W.L., K.Y., J,S.B., T.L.; supervision, Y.D.; project administration, Y.D.; funding acquisition, Y.D. All authors have read and agreed to the published version of the manuscript. The results will be disseminated to the scientific community and relevant groups via publications in scientific journals, presentations at conferences etc.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by the Health and Medical Research Fund (HMRF), Food and Health Bureau, Hong Kong SAR (Ref. 05200098). The funders had no role in the study design, data collection and data analyses in the writing of the manuscript or in the decision to submit the manuscript for publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has received an ethics approval from the Research Ethics Committee\u003c/p\u003e\n\u003cp\u003eof Hong Kong Baptist University (ID:REC/21/22/0281). All participants will sign the informed consent before their participation in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. Informed consent materials will be available from the corresponding author upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRequests of future data and developed materials should be directed to the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflicts of interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBaghai TC, Varallo-Bedarida G, Born C, H\u0026auml;fner S, Sch\u0026uuml;le C, Eser D, et al. 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American journal of preventive medicine. 2007;33(2):155-61.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1. The detailed exercise contents for two intervention groups\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" width=\"100%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003ePhysical exercise program\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"45%\"\u003e\n\u003cp\u003e\u003cstrong\u003e16\u003c/strong\u003e\u003cstrong\u003e-week blended indoor and outdoor MSE intervention group\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(IG-1)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"40%\"\u003e\n\u003cp\u003e\u003cstrong\u003e16\u003c/strong\u003e\u003cstrong\u003e-week indoor-only MSE intervention group\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(IG-2)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eFrequency\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"45%\"\u003e\n\u003cp\u003eone indoor and one outdoor sessions/week\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"40%\"\u003e\n\u003cp\u003etwo indoor sessions/week\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eWarm-up\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"86%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 10 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise: light walking and stretching\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAerobic training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"86%\"\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 30 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Intensity: RPE 11-13\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise:\u003c/p\u003e\n\u003cp\u003e1) Session 1/week (indoor) of two IGs: dancing\u003c/p\u003e\n\u003cp\u003eWeek 1-2: chair dancing.\u003c/p\u003e\n\u003cp\u003eWeek 3-8: dancing without equipment\u003c/p\u003e\n\u003cp\u003eWeek 9-16: towel dancing\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"45%\"\u003e\n\u003cp\u003e2) Session 2/week: nature walking\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"40%\"\u003e\n\u003cp\u003eSession 2/week: indoor walking\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eMuscular strength training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"86%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 20 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Intensity: RPE 11-13\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Volume of each exercise: 2 sets, 8-12 repetitions per set, with 1\u0026ndash;2 minute rest intervals (depending on participants\u0026rsquo; physical capacity)\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise\u003c/p\u003e\n\u003cp\u003eWeek 1-4: four movements including squats, wall push-ups, toe stands, biceps curl (\u003cem\u003eto strengthen body slowly and gently using only own body weight\u003c/em\u003e).\u003c/p\u003e\n\u003cp\u003eWeek 5-12: six movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press (\u003cem\u003eusing own body weight and resistance band\u003c/em\u003e).\u003c/p\u003e\n\u003cp\u003eWeek 13-16: eight movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press, knee extension, knee curl (\u003cem\u003eusing own body weight and resistance band and adjustable ankle weights\u003c/em\u003e).\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003ePostural balance training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"86%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 20 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise:\u003c/p\u003e\n\u003cp\u003eWeek 1-6: exercise without equipment.\u003c/p\u003e\n\u003cp\u003eWeek 7-16: exercise with equipment (Yoga mini balls)\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Eight movements performed in standing and hands-and-knees positions, including walking in place, free-leg swinging, weight shift in all directions, stepping exercises, tandem walking, maintaining a hands-and-knees position while raising either an upper or lower limb or one upper and the opposite lower limb\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eCool-down\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"86%\"\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 10 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise: stretching and mind-body breathing\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2. The protocol of 4-week pilot study\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" width=\"558\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003ePhysical exercise program\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u003cstrong\u003eThe 4-week \u003c/strong\u003e\u003cstrong\u003eblended indoor and outdoor MSE intervention group\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003eFrequency\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003eone indoor + one outdoor sessions/week\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003eWarm-up\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 10 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise: light walking and stretching\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003eAerobic training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 30 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Intensity: RPE 11-13\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise:\u003c/p\u003e\n\u003cp\u003e1) Session 1/week (indoor): dancing\u003c/p\u003e\n\u003cp\u003eWeek 1: chair dancing.\u003c/p\u003e\n\u003cp\u003eWeek 2: dancing without equipment\u003c/p\u003e\n\u003cp\u003eWeek 3: towel dancing\u003c/p\u003e\n\u003cp\u003eWeek 4: towel dancing\u003c/p\u003e\n\u003cp\u003e2) Session 2/week (outdoor): nature walking\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003eMuscular strength training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 20 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Intensity: RPE 11-13\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Volume of each exercise: 2 sets, 8-12 repetitions per set, with 1\u0026ndash;2-minute rest intervals (depending on participants\u0026rsquo; physical capacity)\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise\u003c/p\u003e\n\u003cp\u003eWeek 1: four movements including squats, wall push-ups, toe stands, biceps curl (\u003cem\u003eto strengthen body slowly and gently using only own body weight\u003c/em\u003e).\u003c/p\u003e\n\u003cp\u003eWeek 2: six movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press (\u003cem\u003eusing own body weight and resistance band\u003c/em\u003e).\u003c/p\u003e\n\u003cp\u003eWeek 3-4: eight movements including squats, wall push-ups, toe stands, biceps curl, side hip raise, overhead press, knee extension, knee curl (\u003cem\u003eusing own body weight and resistance band and adjustable ankle weights\u003c/em\u003e).\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003ePostural balance training\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 20 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise:\u003c/p\u003e\n\u003cp\u003eWeek 1-2: exercise without equipment.\u003c/p\u003e\n\u003cp\u003eWeek 3-4: exercise with equipment (Yoga mini balls)\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Movements: eight exercises performed in standing and hands-and-knees positions, including walking in place, free-leg swinging, weight shift in all directions, stepping exercises, tandem walking, maintaining a hand-and- knees position while raising either an upper or lower limb or one upper and the opposite lower limb\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"142\"\u003e\n\u003cp\u003e\u003cstrong\u003eCool-down\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"416\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Duration: 10 mins\u003c/p\u003e\n\u003cp\u003e\u0026bull;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Exercise: stretching and mind-body breathing\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Pictures","content":"\u003cp\u003ePictures 1 and 4 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pubh","sideBox":"Learn more about [BMC Public Health](http://bmcpublichealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pubh/default.aspx","title":"BMC Public Health","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Multicomponent structured exercise, depressive symptoms, older adults, blended environment, outdoor exercise, indoor exercise","lastPublishedDoi":"10.21203/rs.3.rs-4274102/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4274102/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eDepression is a mental health problem often occurring in older adults. More attention has been paid to the benefits of green exercise on mental health in recent years. However, most existing studies of structured exercise on older adults’ depressive symptoms only encompassed one or two exercise components (aerobic/muscular strength/balance) in indoor setting. Considering the advantages of indoor exercise and the high relevance between nature and mental health, the combination of indoor and outdoor multicomponent structured exercise (MSE) programs might be able to maximize intervention effectiveness. The aim of this study is to develop and examine the effect of a blended indoor and outdoor MSE program on depressive symptoms, physical fitness and physical activity (PA) enjoyment in Hong Kong older adults with depressive symptoms.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eThe 16-week single-blinded randomized controlled trial (RCT) (2 sessions/week, 90 min/session) will include 129 community-dwelling older adults aged 60 to 74 years old with depressive symptoms. Participants will be randomized to one of three groups (IG-1: a blended indoor and outdoor MSE group; IG-2: an indoor-only MSE group; CG: a control group) using 1:1:1 allocation ratio. The MSE program (aerobic + muscular strength + balance) will be conducted in IG-1 and IG-2. Primary outcome will be depressive symptoms. Secondary outcomes will include salivary cortisol, physical fitness, physical activity (PA) enjoyment. In addition, the mediating role of connectedness to nature (CN) will be examined to reveal the psychological mechanism of intervention. All measured data will be collected at the pre-intervention, post-intervention, and 3-month follow up stages.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDiscussion: \u003c/strong\u003eThis study will take the initiative to implement the blended indoor and outdoor MSE intervention catering older adults with depressive symptoms. The results will provide more comprehensive evidence support for non-pharmacological interventions and guide future relevant public health policies for the improvement of older adults’ depressive symptoms.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration: \u003c/strong\u003eThis trial is prospectively registered in the ClinicalTrials.gov. Trial registration number NCT06190327 registered 19 December 2023.\u003c/p\u003e","manuscriptTitle":"The effect of a blended indoor and outdoor multicomponent structured exercise program on depressive symptoms in Hong Kong older adults: study protocol of a randomized controlled trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-29 13:26:15","doi":"10.21203/rs.3.rs-4274102/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-09-18T15:41:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-20T00:21:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-20T00:21:06+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Public Health","date":"2024-04-16T07:36:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pubh","sideBox":"Learn more about [BMC Public Health](http://bmcpublichealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pubh/default.aspx","title":"BMC Public Health","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7bfa4cb6-7330-42b9-a7a2-eaa2ae798e08","owner":[],"postedDate":"April 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T16:05:41+00:00","versionOfRecord":{"articleIdentity":"rs-4274102","link":"https://doi.org/10.1186/s12889-025-25244-0","journal":{"identity":"bmc-public-health","isVorOnly":false,"title":"BMC Public Health"},"publishedOn":"2025-11-14 15:58:05","publishedOnDateReadable":"November 14th, 2025"},"versionCreatedAt":"2024-04-29 13:26:15","video":"","vorDoi":"10.1186/s12889-025-25244-0","vorDoiUrl":"https://doi.org/10.1186/s12889-025-25244-0","workflowStages":[]},"version":"v1","identity":"rs-4274102","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4274102","identity":"rs-4274102","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}