Effects of inhalation of the hydrogen-rich gas before sleep on fatigue recovery in healthy adults

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We included 100 healthy adults with no sleep disorders. All participants completed two study visits with a 7-day break. On each of the two, they randomly inhaled either hydrogen-rich (HS) or control gas (CS) for 20 minutes. Each participant completed the assessment of fatigue (e.g., quick recovery, Karolinska Sleepiness scale (KSS)) and functional performance (e.g., Countermovement jump (CMJ), Maximum voluntary isometric contraction (MVIC) and muscle force perception) before inhaling gas and after waking up. No significant difference in the percent change of HRV paraments (i.e., LF/HF, RMSSD, SDNN, LF average, HF average, VLF average) and KSS scale from night to morning were observed between CS and HS ( p > 0.67). Similarly, no significant difference in the percent change of CMJ ( p = 0.12, Z = 1.55) was observed between CS and HS. Compared to CS, the percent change of MVIC (F = 4.95, p = 0.03, η²=0.03) and muscle force perception ( p = 0.01, Z=-2.50) were significantly lower in HS. Inhaling hydrogen-rich gas before sleep can accelerate the recovery of muscle strength and muscle proprioception on the next day in healthy adults. hydrogen fatigue physical functional performance Introduction Humans often recover from fatigue and restore energy for mental and physical functions after the daytime activities via sleep, 1 , 2 which is critical to help maintain the intact functional performance on the next day. 3 Studies have shown that, for example, the prolonged fatigue after the nocturnal sleep may lead to various physical and mental problems including cardiovascular disease, metabolic disease, depression, and anxiety. 4 , 5 Therefore, it is important to accelerate the recovery of fatigue during sleep, which will ultimately benefit the functional performance on the next day. One of the main factors to fatigue is the elevated oxidative stress as induced by excessed free radicals. 6 – 8 Recent studies have shown that molecular hydrogen is an effective antioxidant. With its selective antioxidant function and non-toxic disadvantages, hydrogen has been widely used to relieve fatigue and promote physical performance after high intensity exercise. 9 – 12 Molecular hydrogen can easily permeate bio-membranes and subcellular compartments to selectively reduce OH and ONOO- owing to its lower molecular weight and electrical neutrality. 11 , 13 , 14 Hydrogen can further activate Nrf2 pathways and subsequent induction of Phase-2 antioxidant enzymes to induce lasting effects on anti-oxidative stress for fatigue alleviation. 15 Uniquely, the antioxidants are more effective when the body is exposed to higher levels of oxidative stress. 16 According to the theory called the “sleep paradox”, free radicals accumulated to peak before sleep as fatigue arrived to peak. 17 Inhaling hydrogen immediately before sleep may thus be effective to clear free radicals and thus accelerate the alleviation of fatigue, which, however, has not been examined explicitly. We here therefore contend that inhaling hydrogen gas immediately before sleep can continuously accelerate fatigue recovery, and thus improve the functional performance on the morning of next day. In this study, we examined if inhalation of hydrogen-rich gas immediately before sleep can induce less fatigue and improve physical performance after waking up in healthy adults. Specifically, we hypothesize that: compared to control, inhaling hydrogen-rich gas before sleep would induce i) lower fatigue level as assessed by heart rate variability in Quick recovery test; ii) greater improvement in physical performance assessed by counter-movement jump (CMJ). Materials and methods Participants This study recruited 102 healthy adults from Beijing Sport University (Beijing, China) through posters and they signed a written informed consent before the experiment. The inclusion criteria were: i) all participants with good sleep quality (PSQI score < 5); ii) have no injury history in the past six months and no respiratory disease; iii) did not participate in another biomedical study during the experiment; iv) avoid consuming alcohol or caffeinated foods in the study. The exclusion criteria is self-reported sleep disorder. The Experimental Ethics Committee approved the study protocols for Sports Science at Beijing Sport University (Registration number 2022056H). Participants were informed of the procedures and purpose of the study and provided their written consent to take part. All the applied procedures followed the Declaration of Helsinki with its amendments. Experimental design This study is single-blinded and self-controlled. Participants slept in a standardized sleep laboratory environment at sleep laboratory (Beijing Sport University, Beijing, China), and completed interventions and tests. Participants were required to complete two study visits in the laboratory and keep the same level of daily physical activity monitored by an accelerometer on these two days. On each of the two visits, they inhaled either hydrogen-rich gas (HS) or a control gas (CS) for 20 minutes in randomized order decided by random number. If a single digit appears, participant was assigned to the HS group, whereas if a double digit appears, participant was allocated to the CS group. A 7-day washout period was provided between these two visits to eliminate the potential carry-over effects for the prior visit. Both gases are colorless and odorless, the participants were blinded to the intervention type. Within each visit, before inhaling gas (9:00 p.m.-10:30 p.m.) and after waking up (8:00 a.m.- 9:30 a.m. on the next day), participants completed a series of tests supervised by the same physiotherapist who blinded to patient group allocation. Physiotherapists did not participate in the gas intervention process. Specifically, each participant completed the assessment of quick recovery test in a quiet state, as followed by KSS scoring. Subsequently, a warm-up session was conducted, and participants then completed tests such as CMJ, MVIC, and muscle force perception test. Administration of Hydrogen-rich gas Hydrogen-rich gas was supplied through a hydrogen supply unit (Zhiheng Hydrogen Health Technology Co., Ltd., Fuzhou, China) connected to a nasal inhaler. The ratio of oxygen to hydrogen in the H 2 gas is 2:1, and the maximum concentrations are 21.57% and 4.08%, respectively. The flow rate of H 2 gas is 1800 mL/min. The control gas was supplied by the same hydrogen supply unit that did not initiate the hydrogen production program. The airflow was generated solely through air, and the flow rate was the same as that of the Hydrogen-rich gas. Physical activity level monitor Since the physical activity levels of participants can impact their own sleep quality and fatigue recovery in the subsequent day, potentially affecting the results of data analysis, we monitored their daytime physical activity levels using accelerometer (ActiGraph GT3X+). Participants were instructed to wear the monitor during all waking hours, except when bathing or swimming, and record the days the monitor was worn. Devices were modeled according to the manufacturer’s instructions and configured for the individual’s age /date of birth, sex, and name before monitoring. Each participant wore an GT3X+ (sampling rate 30Hz, Pensacola, FL) secured on a elastic waistband around their side of the dominant hip. The data collected by accelerometer were analyzed by the software, Actilife 6.13. and we chose Troiano Adult's (2008) criteria to calculate the energy consumption. Fatigue Recovery Assessment Quick recovery test: The Firstbeat heart rate band (Firstbeat Analytics, Jyvaskyla, Finland) was placed right below the sternum and in direct contact with the skin. The tightness of the band was adjusted to ensure comfort according to the participants’ size and comfort level. Participants were required to lie down and keep awake, and we started the three minutes of quick recovery test after HR data showing the stable changes. We collected the time domain index (standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences (RMSSD)) and frequency domain index (low frequency (LF) and high frequency (HF)) of HRV. HRV represents the recovery of autonomic nervous system. We used this HRV test in quiet state as the indicator of overall fatigue recovery level. 18 , 19 Karolinska Sleepiness Scale (KSS) test: This is a 9-point scale (1 = extremely alert, 3 = alert, 5 = neither alert nor sleepy, 7 = sleepy but no difficulty remaining awake, and 9 = extremely sleepy and fighting sleep). It has been used in studies of shift work, jetlag, for driving abilities, attention and performance, and in clinical settings. This scale aims to measure the subjective level of sleepiness and reflects the overall psychological state. Physical Function Assessment Countermovement jump test (CMJ): The test was performed using a fixed three-dimensional force platform (Kistler), and the data was collected through a data acquisition box (Shanghai Yingfu Instrument Technology Company, model INFO-FP01) and Kistler BioWare software. The test was performed by standing on the force platform, starting from an upright position with hands on their hips. The participants quickly performed a squat until their thighs were parallel to the ground, followed by an immediate jump, landing on the force platform. Throughout the jumping process, they were instructed to maintain an upright posture. The test was repeated 3 times and start each time after readjusting. The jump height was calculated using the flight time and the average of the three heights was taken. The time when the vertical ground reaction force (F VGR ) was less than 10 N during the test was used as flight time (t fly ), and the jump height H FT was calculated according to the kinematic formula for vertical projectile motion: H FT = 1/2*g* (t fly /2) 2 g represents gravitational acceleration, taken as 9.8 m/s 2 . A higher CMJ value means better power and neuromuscular coordination. Maximum voluntary isometric contraction test (MVIC): Participants sit at the edge of the bed with straps to stabilize the trunk and thighs to avoid generating compensatory force. The maximum isometric knee extension force at 60° of knee flexion was tested using a LINK isometric dynamometer (KFORCE, KINVENT BIOMECANIQUE, France) for 5s, repeated 3 times with 5s intervals, and taken the average. A higher MVIC represents better peripheral muscle strength. Muscle force perception test: The ability to reproduce 25% MVIC of participants was examined in the isometric contraction mode (KFORCE, KINVENT BIOMECANIQUE, France). After testing the maximum isometric knee extension force at a 60° flexed knee position, we calculated the target isometric force value (25% MVIC). The participant was asked to concentrate on feeling the force for 5s, and relax and then reproduce the 25%MVIC force as much as possible and hold it for 5s. The researcher recorded the average value for the 5s. Test repeated 3 times with 5s intervals and test results were not reported back to the participant each time. We calculated the absolute value of the difference between the average of the three results and 25%MVIC, and the smaller the difference, the better the muscle force perception. A smaller force perception difference indicates that the knee joint can more accurately achieve the required muscle force, suggesting better muscle proprioception performance. Duration of sleep Participants were required to go to sleep before 0:00 a.m. and wake up around 8:00 a.m. Then they self-reported the sleep duration on the second day. Statistical analyses Statistical analyses were performed using Stata v16.0 (STATA Corp., College Station, TX). To assess the overall fatigue recovery, we used the LF/HF of quick recovery test as the primary outcome and KSS scale as the secondary outcome. To assess the physical function, we used the performance of CMJ as the primary outcome, and the MVIC and the muscle force perception as the secondary outcomes. All data used mean (standard deviation) for descriptive analysis. We calculated the percent change from pre-sleep (i.e., assessed at evening on the first day) to wake-up (i.e., assessed on the morning next day) for each outcome and used in the analyses. The distribution normality of the percent changes were examined by Shapiro-Wilk test. If it was normally distributed, we used one-way ANOVA models. The model factors were intervention (i.e., hydrogen-rich gas and air), and the dependent variables were the percent change of each primary outcome of overall fatigue recovery and physical function. The physical activity and sleep duration were included as covariates. Similar models were used for secondary outcomes. If the data were not normally distributed, we ran Wilcoxon signed rank test for analysis. To determine the effect size of the intervention, the eat-squared (η²) in one-way ANOVA and Z in Wilcoxon were calculated. The η² was classified as small (0.01 ~ 0.06), medium (0.06 ~ 0.14), or large (> 0.14). 20 And the Z was classified as small (0.1 ~ 0.3), medium (0.3 ~ 0.5), or large (> 0.5). 21 The significant level was set at p < 0.05. Data availability The data associated with the paper are not publicly available but are available from the corresponding author on reasonable request Results Baseline characteristics of the participants A total of 102 participants were screened and participated in this study. One participant was not adapted to the laboratory sleep environment, and another participant’s device did not have enough effective data to collect. The data of 100 participants were thus included in the analysis. There is no significant difference between groups in the physical activity ( p = 0.35) and sleep duration ( p = 0.64). The baseline characteristics of participants are shown in Table I. All the primary outcomes were not normally distributed, we thus used the Wilcoxon signed rank test. In secondary outcomes, RMSSD, SDNN, and MVIC were normally distributed, we thus used one-way ANOVA models; and the Wilcoxon signed rank test was used for other secondary outcomes that were not normally distributed. At baseline, the muscle force perception ( p = 0.04) and KSS scale ( p = 0.01) were significantly different between the CS and HS group, we thus used the Wilcoxon signed rank test. The effects of H2 inhalation before sleep on overall fatigue recovery The primary model showed no significant difference in the percent change of LF/HF between CS group and HS group ( p = 0.67, Z = 0.06, Table II). Similarly, no significant difference in the percent change of secondary outcomes (i.e., RMSSD, SDNN, LF average, HF average and VLF average) of fatigue recovery were observed between CS and HS group ( p > 0.44, Table II). The secondary model showed no significant percent change of KSS scale ( p = 0.59, Z = 0.53) between CS and HS group. The results of H2 inhalation before sleep on physical function The primary model showed no significant difference in the percent change of CMJ ( p = 0.12, Z = 1.55, Table II) between CS and HS group. The secondary models showed that compared to CS group, the percent change of MVIC (F = 4.95, p = 0.03, η²=0.03) and muscle force perception ( p = 0.01, Z=-2.50) were significantly lower in HS group. No significant effects of the covariates (i.e., physical activity and sleep duration) on these outcomes were observed. Adverse events No adverse events were observed in our intervention. Discussion To our knowledge, this is the first study to explore the effects of hydrogen-rich gas inhalation before sleep on fatigue recovery and physical function in next day. It is observed that the inhalation of hydrogen-rich gas before sleep did not significantly improve the overall fatigue recovery (i.e., HRV, KSS scale) after sleep, and can only induce significant improvement in muscle strength (i.e., MVIC) and proprioception (i.e., muscle force perception). The knowledge obtained from this work provide critical knowledge for the design of future study exploring the appropriate protocol of intaking Hydrogen-rich gas before sleep to help the functional recovery. Inhalation of hydrogen-rich gas before sleep did not improve overall fatigue recovery. Theoretically, hydrogen can promote fatigue recovery by improving the quality of sleep. Studies have demonstrated that ingesting hydrogen-rich water for four weeks improves subjective sleep quality; 22 and in another study, it was observed that when mice were exposed to low concentrations of hydrogen for seven consecutive days, the sleep latency was reduced and total sleep time was prolonged as compared to the control. 23 It is known to all that sleep homeostasis can be disrupted by inflammation and oxidative stress. Specifically, it is proposed that systemic inflammation may activate microglial cells and astrocytes in brain regions involved in sleep and circadian regulation. Activated glial cells may secrete pro-inflammatory cytokines, nitric oxide (NO), gliotransmitters, which may affect the expression of key regulators of circadian rhythms (e.g., CLOCK gene). In addition, oxidative stress activates cGMP, which mediates NO regulation of normal sleep homeostasis. 24 Recent studies indicated that hydrogen down-modulates the activation of pro-inflammatory cytokines and NO. 25 Moreover, chronic sleep disruption may increase the activity of the sympathetic nervous system and lead to the disruption of the circadian clock. 26 Meanwhile, Mizuno et al. suggested lower sympathetic nerve activity (i.e., lower LF) after 4-week hydrogen water administration compared to the placebo water group. 19 Our insignificant results may arise from potential celling effects that the sleep quality in this group of healthy younger participants was good enough and cannot be further improved by intaking H 2 (e.g., the sleep duration were similar between CS and HS group). It thus highly demanded that future studies consisting of individuals suffering from sleep disorders to explore the potential benefits of intaking hydrogen acutely before sleep for fatigue recovery. Our study indicated that there was no ergogenic effect of hydrogen inhalation on explosive-strength performance in CMJ. Besides peripheral muscular strength, the performance of CMJ requires high degrees of motor unit recruitment and frequency of nerve pulse delivery. 27 – 29 One session of intaking hydrogen, which though can facilitate local ROS clearance promoting muscle fatigue recovery, may not induce significant improvements in CMJ performance, which depends upon multiple neurophysiological elements. Still, we observed that H 2 inhalation before sleep significantly improved the MVIC and muscle force perception. The performance of MVIC depends on the motoneuronal drive and muscle fibers (e.g., maximal nerve pulse and recruitment of motor units). 30 Muscle force perception is mainly dependent on sensory feedback and discharge from the commands from the central nervous system, 31 for example, helping match if the signal is incoming (related to the magnitude of force sense) or outgoing (related to the production of force). 32 Therefore, the activation of the elements in central nervous system plays an important role in the regulation of MVIC and muscle force perception. Previous studies have demonstrated that intaking hydrogen can facilitate the activation in multiple brain regions. Todorovic et al. observed that, for example, the hydrogen molecules can significantly increase the ratios of choline to creatine in frontal white and gray matter; 33 and in another study, Hong et al. demonstrated that hydrogen induces greater activation of the prefrontal cortex 34 during the performance of endurance test in younger adults. Taken together, it may suggest that in addition to the effects of hydrogen on the clearance of exceeded free radicals, the hydrogen-induced increase in the excitability of cortical regions of the brain may be one of the most important contributors to its benefits for the physical function. Future studies implementing neuroimaging techniques are needed to explore and provide direct evidence to the effects of hydrogen on supraspinal control pertaining to fatigue and physical function in different populations (e.g., professional athlete who took long-term endurance training, or those non-athletic individuals). Limitations Our study focuses on the effects of a single inhalation of hydrogen oxygen mixture gas on fatigue recovery, and future studies could focus on long-term effects of intervention. Meanwhile, in order to better verify the oxidative stress mechanism related to its fatigue recovery, more relevant biochemical indicators can be included in future studies. The effect of inhalation of hydrogen oxygen mixture gas on sleep staging was not measured in this study due to the limitation of conditions, and it can also be accurately explored in the future by using polysomnography and so on. Conclusions Inhaling hydrogen-rich gas before sleep can accelerate the recovery of muscle strength and muscle proprioception on the next day in healthy adults. Declarations Conflicts of interest The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript Funding This research was funded by a grant from National Key Research and Development Program of China (2019YFF0301803). Authors’ contributions Qian Li, Yiting Li, Haochong Liu, Yubo Wang, and Dapeng Bao have given substantial contributions to study conception and design, Qian Li, Yiting Li and Junhong Zhou to data acquisition, analysis and interpretation, Qian Li and Yiting Li to manuscript writing, Junhong Zhou, Haoyang Liu and Dapeng Bao to manuscript critical revision. All authors read and approved the final version of the manuscript. Data availability All data are maintained by the administrator in the laboratory. The data sets generated during the current study are available from the corresponding author on reasonable request. 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Tables Table I.¾ Baseline characteristics of participants Variables CS group HS group Age (years) 22.57±2.44 Height (cm) 171.87±9.08 Weight (kg) 67.10±12.51 BMI (kg/m 2 ) 22.55±2.64 Physical activity (Kcal) 565.93±359.00 562.97±310.82 Sleep duration (min) 437.18±53.31 439.81±31.03 Table II.¾ Effects of inhalation of hydrogen-rich gas for overall fatigue recovery and physical function Variables CS-Night CS-Morning HS-Night HS-Morning CS-Diff (%) HS-Diff (%) p-value Overall fatigue RMSSD (ms) 49.91±24.50 65.36±31.47 46.70±20.90 57.94±24.73 40.01±69.28 35.21±67.27 0.67 SDNN (ms) 54.32±23.60 67.17±26.05 50.46±17.51 64.28±22.70 27.58±38.37 29.25±39.17 0.78 LF/HF (%) 81.59±82.04 73.55±61.84 86.69±108.22 74.19±56.91 37.10±125.12 42.59±157.86 0.95 LF average (ms^2) 1929.75±2671.86 2432.74±2694.46 1451.95±1472.01 2198.60±1986.84 103.86±198.54 211.19±563.28 0.44 HF average (ms^2) 3027.85±3044.66 4539.23±3917.25 2396.97±1982.12 3978.70±3135.27 147.81±354.98 233.31±635.88 0.73 VLF average (ms^2) 136.92±134.03 218.63±212.76 131.12±133.25 212.16±179.20 149.18±297.35 180.52±392.02 0.59 KSS scale 5.75±1.40 5.64±1.87 5.30±1.66 5.40±1.88 32.23±46.39 35.43±47.15 0.59 Physical function CMJ (cm) 26.28±9.59 25.26±9.40 26.83±10.44 26.37±9.68 -4.98±17.67 -0.67±47.31 0.12 MVIC (kg) 55.43±20.01 52.78±19.35 53.14±20.11 53.78±19.77 -3.29±17.46 3.13±19.62 0.03 Force perception (kg) 1.46±3.83 2.12±3.45 2.84±4.70 1.77±3.14 200.48±740.38 88.04±457.98 0.01 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4262540","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":293601313,"identity":"4abd426b-a9ef-43c2-972b-838e9c1e58df","order_by":0,"name":"Qian Li","email":"","orcid":"","institution":"Sports Coaching College, Beijing Sport University","correspondingAuthor":false,"prefix":"","firstName":"Qian","middleName":"","lastName":"Li","suffix":""},{"id":293601314,"identity":"770e1c6a-dc9c-4aa6-a1cd-bc164abf0024","order_by":1,"name":"Yiting Li","email":"","orcid":"","institution":"School of Sport Medicine and Physical Therapy, Beijing Sport University","correspondingAuthor":false,"prefix":"","firstName":"Yiting","middleName":"","lastName":"Li","suffix":""},{"id":293601315,"identity":"e5dc5360-dbe9-431d-829d-a4089bf71baf","order_by":2,"name":"Haochong Liu","email":"","orcid":"","institution":"Sports Coaching College, Beijing Sport University","correspondingAuthor":false,"prefix":"","firstName":"Haochong","middleName":"","lastName":"Liu","suffix":""},{"id":293601316,"identity":"e8851c6f-2f7b-4b2e-98bc-46d7077646af","order_by":3,"name":"Yubo Wang","email":"","orcid":"","institution":"China Institute of Sport and Health Science, Beijing Sport University","correspondingAuthor":false,"prefix":"","firstName":"Yubo","middleName":"","lastName":"Wang","suffix":""},{"id":293601317,"identity":"434b5a43-1efd-4e88-be00-ea5c6d1e43e0","order_by":4,"name":"Dapeng Bao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuElEQVRIiWNgGAWjYBACAyCWYKg4AOZIkKDlDMlaGNtI0WLOfvjg7cJ5d+wNDjAfvM3DYJdHUItlT1qy9cxtzxI3HGBLtuZhSC4m7LADOWbSvNsOJxgc4DGT5mE4kNhAUMv5N0Atcw4DHcb/jUgtN0C2NBxm3HCAh404LZYzniVbzzj2LHHmYTZjyzkGyYS1mPMnH7xdUHPHnu9488MbbyrsCGsBAWYEaUCMeriWUTAKRsEoGAW4AADxNzwRA8n8DQAAAABJRU5ErkJggg==","orcid":"","institution":"China Institute of Sport and Health Science, Beijing Sport University","correspondingAuthor":true,"prefix":"","firstName":"Dapeng","middleName":"","lastName":"Bao","suffix":""},{"id":293601318,"identity":"e10aff0a-ce05-495b-b8a1-dd90805e46b4","order_by":5,"name":"Haoyang Liu","email":"","orcid":"","institution":"Sports Coaching College, Beijing Sport University","correspondingAuthor":false,"prefix":"","firstName":"Haoyang","middleName":"","lastName":"Liu","suffix":""},{"id":293601319,"identity":"bc7d7802-5a64-4144-b2c2-c8e2d922db96","order_by":6,"name":"Junhong Zhou","email":"","orcid":"","institution":"Hebrew Senior Life Hinda and Arthur Marcus Institute for Aging Research, Harvard Medical School","correspondingAuthor":false,"prefix":"","firstName":"Junhong","middleName":"","lastName":"Zhou","suffix":""}],"badges":[],"createdAt":"2024-04-13 16:44:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4262540/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4262540/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62250369,"identity":"9d7bd29a-1add-460f-b226-8717a6cb718a","added_by":"auto","created_at":"2024-08-12 05:59:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":537398,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4262540/v1/593a488d-550d-4f66-a285-4b88cf897578.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of inhalation of the hydrogen-rich gas before sleep on fatigue recovery in healthy adults","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHumans often recover from fatigue and restore energy for mental and physical functions after the daytime activities via sleep,\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e which is critical to help maintain the intact functional performance on the next day.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e Studies have shown that, for example, the prolonged fatigue after the nocturnal sleep may lead to various physical and mental problems including cardiovascular disease, metabolic disease, depression, and anxiety.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e Therefore, it is important to accelerate the recovery of fatigue during sleep, which will ultimately benefit the functional performance on the next day.\u003c/p\u003e \u003cp\u003eOne of the main factors to fatigue is the elevated oxidative stress as induced by excessed free radicals.\u003csup\u003e\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e Recent studies have shown that molecular hydrogen is an effective antioxidant. With its selective antioxidant function and non-toxic disadvantages, hydrogen has been widely used to relieve fatigue and promote physical performance after high intensity exercise.\u003csup\u003e\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e Molecular hydrogen can easily permeate bio-membranes and subcellular compartments to selectively reduce OH and ONOO- owing to its lower molecular weight and electrical neutrality.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e Hydrogen can further activate Nrf2 pathways and subsequent induction of Phase-2 antioxidant enzymes to induce lasting effects on anti-oxidative stress for fatigue alleviation.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eUniquely, the antioxidants are more effective when the body is exposed to higher levels of oxidative stress.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e According to the theory called the \u0026ldquo;sleep paradox\u0026rdquo;, free radicals accumulated to peak before sleep as fatigue arrived to peak.\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e Inhaling hydrogen immediately before sleep may thus be effective to clear free radicals and thus accelerate the alleviation of fatigue, which, however, has not been examined explicitly. We here therefore contend that inhaling hydrogen gas immediately before sleep can continuously accelerate fatigue recovery, and thus improve the functional performance on the morning of next day.\u003c/p\u003e \u003cp\u003eIn this study, we examined if inhalation of hydrogen-rich gas immediately before sleep can induce less fatigue and improve physical performance after waking up in healthy adults. Specifically, we hypothesize that: compared to control, inhaling hydrogen-rich gas before sleep would induce i) lower fatigue level as assessed by heart rate variability in Quick recovery test; ii) greater improvement in physical performance assessed by counter-movement jump (CMJ).\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003e This study recruited 102 healthy adults from Beijing Sport University (Beijing, China) through posters and they signed a written informed consent before the experiment. The inclusion criteria were: i) all participants with good sleep quality (PSQI score\u0026thinsp;\u0026lt;\u0026thinsp;5); ii) have no injury history in the past six months and no respiratory disease; iii) did not participate in another biomedical study during the experiment; iv) avoid consuming alcohol or caffeinated foods in the study. The exclusion criteria is self-reported sleep disorder. The Experimental Ethics Committee approved the study protocols for Sports Science at Beijing Sport University (Registration number 2022056H). Participants were informed of the procedures and purpose of the study and provided their written consent to take part. All the applied procedures followed the Declaration of Helsinki with its amendments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eExperimental design\u003c/h2\u003e \u003cp\u003eThis study is single-blinded and self-controlled. Participants slept in a standardized sleep laboratory environment at sleep laboratory (Beijing Sport University, Beijing, China), and completed interventions and tests. Participants were required to complete two study visits in the laboratory and keep the same level of daily physical activity monitored by an accelerometer on these two days. On each of the two visits, they inhaled either hydrogen-rich gas (HS) or a control gas (CS) for 20 minutes in randomized order decided by random number. If a single digit appears, participant was assigned to the HS group, whereas if a double digit appears, participant was allocated to the CS group. A 7-day washout period was provided between these two visits to eliminate the potential carry-over effects for the prior visit. Both gases are colorless and odorless, the participants were blinded to the intervention type. Within each visit, before inhaling gas (9:00 p.m.-10:30 p.m.) and after waking up (8:00 a.m.- 9:30 a.m. on the next day), participants completed a series of tests supervised by the same physiotherapist who blinded to patient group allocation. Physiotherapists did not participate in the gas intervention process. Specifically, each participant completed the assessment of quick recovery test in a quiet state, as followed by KSS scoring. Subsequently, a warm-up session was conducted, and participants then completed tests such as CMJ, MVIC, and muscle force perception test.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eAdministration of Hydrogen-rich gas\u003c/h2\u003e \u003cp\u003eHydrogen-rich gas was supplied through a hydrogen supply unit (Zhiheng Hydrogen Health Technology Co., Ltd., Fuzhou, China) connected to a nasal inhaler. The ratio of oxygen to hydrogen in the H\u003csub\u003e2\u003c/sub\u003e gas is 2:1, and the maximum concentrations are 21.57% and 4.08%, respectively. The flow rate of H\u003csub\u003e2\u003c/sub\u003e gas is 1800 mL/min. The control gas was supplied by the same hydrogen supply unit that did not initiate the hydrogen production program. The airflow was generated solely through air, and the flow rate was the same as that of the Hydrogen-rich gas.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003ePhysical activity level monitor\u003c/h2\u003e \u003cp\u003eSince the physical activity levels of participants can impact their own sleep quality and fatigue recovery in the subsequent day, potentially affecting the results of data analysis, we monitored their daytime physical activity levels using accelerometer (ActiGraph GT3X+). Participants were instructed to wear the monitor during all waking hours, except when bathing or swimming, and record the days the monitor was worn. Devices were modeled according to the manufacturer\u0026rsquo;s instructions and configured for the individual\u0026rsquo;s age /date of birth, sex, and name before monitoring. Each participant wore an GT3X+ (sampling rate 30Hz, Pensacola, FL) secured on a elastic waistband around their side of the dominant hip. The data collected by accelerometer were analyzed by the software, Actilife 6.13. and we chose Troiano Adult's (2008) criteria to calculate the energy consumption.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eFatigue Recovery Assessment\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eQuick recovery test: The Firstbeat heart rate band (Firstbeat Analytics, Jyvaskyla, Finland) was placed right below the sternum and in direct contact with the skin. The tightness of the band was adjusted to ensure comfort according to the participants\u0026rsquo; size and comfort level. Participants were required to lie down and keep awake, and we started the three minutes of quick recovery test after HR data showing the stable changes. We collected the time domain index (standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences (RMSSD)) and frequency domain index (low frequency (LF) and high frequency (HF)) of HRV. HRV represents the recovery of autonomic nervous system. We used this HRV test in quiet state as the indicator of overall fatigue recovery level.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eKarolinska Sleepiness Scale (KSS) test: This is a 9-point scale (1\u0026thinsp;=\u0026thinsp;extremely alert, 3\u0026thinsp;=\u0026thinsp;alert, 5\u0026thinsp;=\u0026thinsp;neither alert nor sleepy, 7\u0026thinsp;=\u0026thinsp;sleepy but no difficulty remaining awake, and 9\u0026thinsp;=\u0026thinsp;extremely sleepy and fighting sleep). It has been used in studies of shift work, jetlag, for driving abilities, attention and performance, and in clinical settings. This scale aims to measure the subjective level of sleepiness and reflects the overall psychological state.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePhysical Function Assessment\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eCountermovement jump test (CMJ): The test was performed using a fixed three-dimensional force platform (Kistler), and the data was collected through a data acquisition box (Shanghai Yingfu Instrument Technology Company, model INFO-FP01) and Kistler BioWare software. The test was performed by standing on the force platform, starting from an upright position with hands on their hips. The participants quickly performed a squat until their thighs were parallel to the ground, followed by an immediate jump, landing on the force platform. Throughout the jumping process, they were instructed to maintain an upright posture. The test was repeated 3 times and start each time after readjusting. The jump height was calculated using the flight time and the average of the three heights was taken. The time when the vertical ground reaction force (F\u003csub\u003eVGR\u003c/sub\u003e) was less than 10 N during the test was used as flight time (t\u003csub\u003efly\u003c/sub\u003e), and the jump height H\u003csub\u003eFT\u003c/sub\u003e was calculated according to the kinematic formula for vertical projectile motion:\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eH\u003csub\u003eFT\u003c/sub\u003e = 1/2*g* (t\u003csub\u003efly\u003c/sub\u003e /2)\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eg represents gravitational acceleration, taken as 9.8 m/s\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA higher CMJ value means better power and neuromuscular coordination.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eMaximum voluntary isometric contraction test (MVIC): Participants sit at the edge of the bed with straps to stabilize the trunk and thighs to avoid generating compensatory force. The maximum isometric knee extension force at 60\u0026deg; of knee flexion was tested using a LINK isometric dynamometer (KFORCE, KINVENT BIOMECANIQUE, France) for 5s, repeated 3 times with 5s intervals, and taken the average. A higher MVIC represents better peripheral muscle strength.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMuscle force perception test: The ability to reproduce 25% MVIC of participants was examined in the isometric contraction mode (KFORCE, KINVENT BIOMECANIQUE, France). After testing the maximum isometric knee extension force at a 60\u0026deg; flexed knee position, we calculated the target isometric force value (25% MVIC). The participant was asked to concentrate on feeling the force for 5s, and relax and then reproduce the 25%MVIC force as much as possible and hold it for 5s. The researcher recorded the average value for the 5s. Test repeated 3 times with 5s intervals and test results were not reported back to the participant each time. We calculated the absolute value of the difference between the average of the three results and 25%MVIC, and the smaller the difference, the better the muscle force perception. A smaller force perception difference indicates that the knee joint can more accurately achieve the required muscle force, suggesting better muscle proprioception performance.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eDuration of sleep\u003c/h2\u003e \u003cp\u003eParticipants were required to go to sleep before 0:00 a.m. and wake up around 8:00 a.m. Then they self-reported the sleep duration on the second day.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analyses\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using Stata v16.0 (STATA Corp., College Station, TX). To assess the overall fatigue recovery, we used the LF/HF of quick recovery test as the primary outcome and KSS scale as the secondary outcome. To assess the physical function, we used the performance of CMJ as the primary outcome, and the MVIC and the muscle force perception as the secondary outcomes. All data used mean (standard deviation) for descriptive analysis. We calculated the percent change from pre-sleep (i.e., assessed at evening on the first day) to wake-up (i.e., assessed on the morning next day) for each outcome and used in the analyses. The distribution normality of the percent changes were examined by Shapiro-Wilk test. If it was normally distributed, we used one-way ANOVA models. The model factors were intervention (i.e., hydrogen-rich gas and air), and the dependent variables were the percent change of each primary outcome of overall fatigue recovery and physical function. The physical activity and sleep duration were included as covariates. Similar models were used for secondary outcomes. If the data were not normally distributed, we ran Wilcoxon signed rank test for analysis. To determine the effect size of the intervention, the eat-squared (η\u0026sup2;) in one-way ANOVA and Z in Wilcoxon were calculated. The η\u0026sup2; was classified as small (0.01\u0026thinsp;~\u0026thinsp;0.06), medium (0.06\u0026thinsp;~\u0026thinsp;0.14), or large (\u0026gt;\u0026thinsp;0.14).\u003csup\u003e20\u003c/sup\u003e And the Z was classified as small (0.1\u0026thinsp;~\u0026thinsp;0.3), medium (0.3\u0026thinsp;~\u0026thinsp;0.5), or large (\u0026gt;\u0026thinsp;0.5).\u003csup\u003e21\u003c/sup\u003e The significant level was set at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe data associated with the paper are not publicly available but are available from the corresponding author on reasonable request\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eBaseline characteristics of the participants\u003c/h2\u003e \u003cp\u003eA total of 102 participants were screened and participated in this study. One participant was not adapted to the laboratory sleep environment, and another participant\u0026rsquo;s device did not have enough effective data to collect. The data of 100 participants were thus included in the analysis. There is no significant difference between groups in the physical activity (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.35) and sleep duration (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.64). The baseline characteristics of participants are shown in Table I. All the primary outcomes were not normally distributed, we thus used the Wilcoxon signed rank test. In secondary outcomes, RMSSD, SDNN, and MVIC were normally distributed, we thus used one-way ANOVA models; and the Wilcoxon signed rank test was used for other secondary outcomes that were not normally distributed. At baseline, the muscle force perception (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.04) and KSS scale (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01) were significantly different between the CS and HS group, we thus used the Wilcoxon signed rank test.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eThe effects of H2 inhalation before sleep on overall fatigue recovery\u003c/h2\u003e \u003cp\u003eThe primary model showed no significant difference in the percent change of LF/HF between CS group and HS group (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.67, Z\u0026thinsp;=\u0026thinsp;0.06, Table II). Similarly, no significant difference in the percent change of secondary outcomes (i.e., RMSSD, SDNN, LF average, HF average and VLF average) of fatigue recovery were observed between CS and HS group (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.44, Table II). The secondary model showed no significant percent change of KSS scale (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.59, Z\u0026thinsp;=\u0026thinsp;0.53) between CS and HS group.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eThe results of H2 inhalation before sleep on physical function\u003c/h2\u003e \u003cp\u003eThe primary model showed no significant difference in the percent change of CMJ (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.12, Z\u0026thinsp;=\u0026thinsp;1.55, Table II) between CS and HS group. The secondary models showed that compared to CS group, the percent change of MVIC (F\u0026thinsp;=\u0026thinsp;4.95, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.03, η\u0026sup2;=0.03) and muscle force perception (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01, Z=-2.50) were significantly lower in HS group. No significant effects of the covariates (i.e., physical activity and sleep duration) on these outcomes were observed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eAdverse events\u003c/h2\u003e \u003cp\u003eNo adverse events were observed in our intervention.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eTo our knowledge, this is the first study to explore the effects of hydrogen-rich gas inhalation before sleep on fatigue recovery and physical function in next day. It is observed that the inhalation of hydrogen-rich gas before sleep did not significantly improve the overall fatigue recovery (i.e., HRV, KSS scale) after sleep, and can only induce significant improvement in muscle strength (i.e., MVIC) and proprioception (i.e., muscle force perception). The knowledge obtained from this work provide critical knowledge for the design of future study exploring the appropriate protocol of intaking Hydrogen-rich gas before sleep to help the functional recovery.\u003c/p\u003e \u003cp\u003eInhalation of hydrogen-rich gas before sleep did not improve overall fatigue recovery. Theoretically, hydrogen can promote fatigue recovery by improving the quality of sleep. Studies have demonstrated that ingesting hydrogen-rich water for four weeks improves subjective sleep quality;\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e and in another study, it was observed that when mice were exposed to low concentrations of hydrogen for seven consecutive days, the sleep latency was reduced and total sleep time was prolonged as compared to the control.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e It is known to all that sleep homeostasis can be disrupted by inflammation and oxidative stress. Specifically, it is proposed that systemic inflammation may activate microglial cells and astrocytes in brain regions involved in sleep and circadian regulation. Activated glial cells may secrete pro-inflammatory cytokines, nitric oxide (NO), gliotransmitters, which may affect the expression of key regulators of circadian rhythms (e.g., CLOCK gene). In addition, oxidative stress activates cGMP, which mediates NO regulation of normal sleep homeostasis.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e Recent studies indicated that hydrogen down-modulates the activation of pro-inflammatory cytokines and NO.\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e Moreover, chronic sleep disruption may increase the activity of the sympathetic nervous system and lead to the disruption of the circadian clock.\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e Meanwhile, Mizuno et al. suggested lower sympathetic nerve activity (i.e., lower LF) after 4-week hydrogen water administration compared to the placebo water group.\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e Our insignificant results may arise from potential celling effects that the sleep quality in this group of healthy younger participants was good enough and cannot be further improved by intaking H\u003csub\u003e2\u003c/sub\u003e (e.g., the sleep duration were similar between CS and HS group). It thus highly demanded that future studies consisting of individuals suffering from sleep disorders to explore the potential benefits of intaking hydrogen acutely before sleep for fatigue recovery.\u003c/p\u003e \u003cp\u003eOur study indicated that there was no ergogenic effect of hydrogen inhalation on explosive-strength performance in CMJ. Besides peripheral muscular strength, the performance of CMJ requires high degrees of motor unit recruitment and frequency of nerve pulse delivery.\u003csup\u003e\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e One session of intaking hydrogen, which though can facilitate local ROS clearance promoting muscle fatigue recovery, may not induce significant improvements in CMJ performance, which depends upon multiple neurophysiological elements. Still, we observed that H\u003csub\u003e2\u003c/sub\u003e inhalation before sleep significantly improved the MVIC and muscle force perception. The performance of MVIC depends on the motoneuronal drive and muscle fibers (e.g., maximal nerve pulse and recruitment of motor units).\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e Muscle force perception is mainly dependent on sensory feedback and discharge from the commands from the central nervous system,\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e for example, helping match if the signal is incoming (related to the magnitude of force sense) or outgoing (related to the production of force).\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e Therefore, the activation of the elements in central nervous system plays an important role in the regulation of MVIC and muscle force perception. Previous studies have demonstrated that intaking hydrogen can facilitate the activation in multiple brain regions. Todorovic et al. observed that, for example, the hydrogen molecules can significantly increase the ratios of choline to creatine in frontal white and gray matter;\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e and in another study, Hong et al. demonstrated that hydrogen induces greater activation of the prefrontal cortex\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e during the performance of endurance test in younger adults. Taken together, it may suggest that in addition to the effects of hydrogen on the clearance of exceeded free radicals, the hydrogen-induced increase in the excitability of cortical regions of the brain may be one of the most important contributors to its benefits for the physical function. Future studies implementing neuroimaging techniques are needed to explore and provide direct evidence to the effects of hydrogen on supraspinal control pertaining to fatigue and physical function in different populations (e.g., professional athlete who took long-term endurance training, or those non-athletic individuals).\u003c/p\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eOur study focuses on the effects of a single inhalation of hydrogen oxygen mixture gas on fatigue recovery, and future studies could focus on long-term effects of intervention. Meanwhile, in order to better verify the oxidative stress mechanism related to its fatigue recovery, more relevant biochemical indicators can be included in future studies. The effect of inhalation of hydrogen oxygen mixture gas on sleep staging was not measured in this study due to the limitation of conditions, and it can also be accurately explored in the future by using polysomnography and so on.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eInhaling hydrogen-rich gas before sleep can accelerate the recovery of muscle strength and muscle proprioception on the next day in healthy adults.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eConflicts of interest\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by a grant from National Key Research and Development Program of China (2019YFF0301803).\u003cs\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/s\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAuthors\u0026rsquo; contributions\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eQian Li, Yiting Li, Haochong Liu, Yubo Wang, and Dapeng Bao have given substantial contributions to study conception and design, Qian Li, Yiting Li and Junhong Zhou to data acquisition, analysis and interpretation, Qian Li and Yiting Li to manuscript writing, Junhong Zhou, Haoyang Liu and Dapeng Bao to manuscript critical revision. All authors read and approved the final version of the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eData availability\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAll data are maintained by the administrator in the laboratory. The data sets generated during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgements\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge funding from the Key Research and Development Program of China. \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMariman, A. N. \u003cem\u003eet al.\u003c/em\u003e Sleep in the chronic fatigue syndrome. \u003cem\u003eSleep Medicine Reviews\u003c/em\u003e \u003cstrong\u003e17\u003c/strong\u003e, 193\u0026ndash;199 (2013).\u003c/li\u003e\n\u003cli\u003eSimon, K. C., McDevitt, E. A., Ragano, R. \u0026amp; Mednick, S. C. 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Perception of finger forces within the hand after index finger fatiguing exercise. \u003cem\u003eExp Brain Res\u003c/em\u003e \u003cstrong\u003e182\u003c/strong\u003e, 169\u0026ndash;177 (2007).\u003c/li\u003e\n\u003cli\u003eTodorovic, N. \u003cem\u003eet al.\u003c/em\u003e Hydrogen-rich water and caffeine for alertness and brain metabolism in sleep-deprived habitual coffee drinkers. \u003cem\u003eFood Sci Nutr\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 5139\u0026ndash;5145 (2021).\u003c/li\u003e\n\u003cli\u003eHong, Y. \u003cem\u003eet al.\u003c/em\u003e Effects of pre-exercise H2 inhalation on physical fatigue and related prefrontal cortex activation during and after high-intensity exercise. \u003cem\u003eFront Physiol\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 988028 (2022).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable I.\u0026frac34; \u003cem\u003eBaseline characteristics of participants\u003c/em\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariables\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCS\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHS\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.285509325681495%\" valign=\"top\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"66.71449067431851%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e22.57\u0026plusmn;2.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.285509325681495%\" valign=\"top\"\u003e\n \u003cp\u003eHeight (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"66.71449067431851%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e171.87\u0026plusmn;9.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.285509325681495%\" valign=\"top\"\u003e\n \u003cp\u003eWeight (kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"66.71449067431851%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e67.10\u0026plusmn;12.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.285509325681495%\" valign=\"top\"\u003e\n \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"66.71449067431851%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e22.55\u0026plusmn;2.64\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003ePhysical activity (Kcal)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e565.93\u0026plusmn;359.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e562.97\u0026plusmn;310.82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003eSleep duration (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e437.18\u0026plusmn;53.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.333333333333336%\" valign=\"top\"\u003e\n \u003cp\u003e439.81\u0026plusmn;31.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTable II.\u0026frac34; \u003cem\u003eEffects of inhalation of hydrogen-rich gas for overall fatigue recovery and physical function\u003c/em\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eVariables\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCS-Night\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCS-Morning\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHS-Night\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHS-Morning\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCS-Diff (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eHS-Diff (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ep-value\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eOverall fatigue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eRMSSD (ms)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e49.91\u0026plusmn;24.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e65.36\u0026plusmn;31.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e46.70\u0026plusmn;20.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e57.94\u0026plusmn;24.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e40.01\u0026plusmn;69.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e35.21\u0026plusmn;67.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eSDNN (ms)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e54.32\u0026plusmn;23.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e67.17\u0026plusmn;26.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e50.46\u0026plusmn;17.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e64.28\u0026plusmn;22.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e27.58\u0026plusmn;38.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e29.25\u0026plusmn;39.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eLF/HF (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e81.59\u0026plusmn;82.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e73.55\u0026plusmn;61.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e86.69\u0026plusmn;108.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e74.19\u0026plusmn;56.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e37.10\u0026plusmn;125.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e42.59\u0026plusmn;157.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eLF average (ms^2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e1929.75\u0026plusmn;2671.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e2432.74\u0026plusmn;2694.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e1451.95\u0026plusmn;1472.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e2198.60\u0026plusmn;1986.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e103.86\u0026plusmn;198.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e211.19\u0026plusmn;563.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eHF average (ms^2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e3027.85\u0026plusmn;3044.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e4539.23\u0026plusmn;3917.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e2396.97\u0026plusmn;1982.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e3978.70\u0026plusmn;3135.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e147.81\u0026plusmn;354.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e233.31\u0026plusmn;635.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eVLF average (ms^2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e136.92\u0026plusmn;134.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e218.63\u0026plusmn;212.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e131.12\u0026plusmn;133.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e212.16\u0026plusmn;179.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e149.18\u0026plusmn;297.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e180.52\u0026plusmn;392.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eKSS scale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e5.75\u0026plusmn;1.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e5.64\u0026plusmn;1.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e5.30\u0026plusmn;1.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e5.40\u0026plusmn;1.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e32.23\u0026plusmn;46.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e35.43\u0026plusmn;47.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003ePhysical function\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eCMJ (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e26.28\u0026plusmn;9.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e25.26\u0026plusmn;9.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e26.83\u0026plusmn;10.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e26.37\u0026plusmn;9.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e-4.98\u0026plusmn;17.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e-0.67\u0026plusmn;47.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eMVIC (kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e55.43\u0026plusmn;20.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e52.78\u0026plusmn;19.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e53.14\u0026plusmn;20.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e53.78\u0026plusmn;19.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e-3.29\u0026plusmn;17.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e3.13\u0026plusmn;19.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.346938775510203%\" valign=\"top\"\u003e\n \u003cp\u003eForce perception (kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e1.46\u0026plusmn;3.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.285714285714286%\" valign=\"top\"\u003e\n \u003cp\u003e2.12\u0026plusmn;3.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e2.84\u0026plusmn;4.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.26530612244898%\" valign=\"top\"\u003e\n \u003cp\u003e1.77\u0026plusmn;3.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e200.48\u0026plusmn;740.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.224489795918368%\" valign=\"top\"\u003e\n \u003cp\u003e88.04\u0026plusmn;457.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.122448979591836%\" valign=\"top\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"hydrogen, fatigue, physical functional performance","lastPublishedDoi":"10.21203/rs.3.rs-4262540/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4262540/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOur objective was to examine if inhalation of hydrogen-rich gas before sleep can help alleviate fatigue and improve physical performance after waking up in healthy adults. We included 100 healthy adults with no sleep disorders. All participants completed two study visits with a 7-day break. On each of the two, they randomly inhaled either hydrogen-rich (HS) or control gas (CS) for 20 minutes. Each participant completed the assessment of fatigue (e.g., quick recovery, Karolinska Sleepiness scale (KSS)) and functional performance (e.g., Countermovement jump (CMJ), Maximum voluntary isometric contraction (MVIC) and muscle force perception) before inhaling gas and after waking up. No significant difference in the percent change of HRV paraments (i.e., LF/HF, RMSSD, SDNN, LF average, HF average, VLF average) and KSS scale from night to morning were observed between CS and HS (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.67). Similarly, no significant difference in the percent change of CMJ (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.12, Z\u0026thinsp;=\u0026thinsp;1.55) was observed between CS and HS. Compared to CS, the percent change of MVIC (F\u0026thinsp;=\u0026thinsp;4.95, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.03, η\u0026sup2;=0.03) and muscle force perception (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01, Z=-2.50) were significantly lower in HS.\u003c/p\u003e \u003cp\u003eInhaling hydrogen-rich gas before sleep can accelerate the recovery of muscle strength and muscle proprioception on the next day in healthy adults.\u003c/p\u003e","manuscriptTitle":"Effects of inhalation of the hydrogen-rich gas before sleep on fatigue recovery in healthy adults","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-23 16:12:55","doi":"10.21203/rs.3.rs-4262540/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d640ffd5-d646-4524-a9bf-f9ed98113f4b","owner":[],"postedDate":"April 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-08-12T05:51:52+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-23 16:12:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4262540","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4262540","identity":"rs-4262540","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}