Effects of Head Kinematics and COM on CHS of 5-Iron Among Male Golfers of Varied Skill Levels

Effects of Head Kinematics and COM on CHS of 5-Iron Among Male Golfers of Varied Skill Levels | 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 Research Article Effects of Head Kinematics and COM on CHS of 5-Iron Among Male Golfers of Varied Skill Levels Lin Huang, Heng Liu, Chao Li, Baohua Liu, ZeFeng Wang, Liang Chen, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8213762/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Objective The present study investigates the impact of head stability characteristics on clubhead speed (CHS) during 5-iron swings in golfers of varying skill levels. Methods Twelve male golfers from Tianjin University of Sport were recruited as participants.The Qualisys three-dimensional motion capture system (250 Hz) was employed to collect head kinematic parameters, center of mass (COM), club head speed (CHS), and ball-striking performance indicators.Independent-samples t-tests and Pearson correlation analyses were performed to examine associations among the parameters. Results (1) CHS characteristics: X-CHS (target-direction velocity component): During 20%–40% of the swing cycle, national-level athletes demonstrated significantly lower values than national second-level athletes (t = − 1.562, d = − 0.462); Y-CHS (anterior-posterior velocity component): During 80%–90% of the swing cycle, national-level athletes showed significantly higher values than national second-level athletes (t = 1.625, d = 0.321); Z-CHS (vertical velocity component): During 20%–40% of the swing cycle, national-level athletes exhibited significantly higher values than national second-level athletes (t = 4.819, d = 1.621). (2) Head posture characteristics: Throughout the 0%–100% swing cycle, national-level athletes maintained a significantly greater head forward lean angle than national second-level athletes (t = − 3.887, d = − 0.916). (3) COM characteristics: Throughout the entire swing cycle, national-level athletes demonstrated significantly greater mediolateral (ML) COM displacement than national second-level athletes (t = 3.942, d = 1.134, p < 0.001). (4) Correlation analysis: For national-level athletes, head forward lean showed a positive correlation with X-CHS during 78%–85% of the swing cycle (r = 0.689, p < 0.001). National second-level athletes exhibited multiphase fluctuations in correlations between head posture and CHS. During 46%–63% of the swing cycle, national-level athletes' AP-COM (anterior-posterior direction) demonstrated a negative correlation with X-CHS (r = − 0.635, p = 0.008). During 0%–60% of the swing cycle, national second-level athletes' vertical-COM axis showed a significant negative correlation with Z-CHS (r = − 0.661, p = 0.005). During 8%–62% of the swing cycle, national-level athletes' AP-COM exhibited a significant negative correlation with head lateral displacement (r = − 0.533, p = 0.01); national second-level athletes showed positive correlations between triaxial COM and head displacement throughout the entire cycle (0%–100%) (r = 0.982, p < 0.001). Conclusion National-level athletes achieved efficient energy transfer through head stability control and head-center of mass (COM) coordination, whereas national second-level athletes exhibited fluctuating head posture control characteristics. National-level athletes attained higher clubhead speed by precisely controlling the head forward lean angle, moderately increasing lateral displacement, and establishing antagonistic coordination with the COM, thereby achieving dynamic stability of the rotation axis and efficient energy transfer. National second-level athletes demonstrated insufficient head stability, and their movement pattern of complete synchronization between the COM and head limited the separation effect of the kinetic chain. Golf Postural characteristics Club head speed 5-iron Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Golf is a precision sport that demands high levels of body control, requiring athletes to maintain exceptional stability and coordination throughout the swing motion to achieve precise control over ball-striking outcomes.Within the diversified club system, the 5-iron combines medium- to long-distance striking demands with precision landing requirements. Compared to short irons, it requires greater swing speed stability to ensure distance output; compared to the driver, it demands more stringent control precision over club face angle. Consequently, the 5-iron swing technique serves not only as a core indicator for assessing athletes' skill levels but also as a critical technical vehicle in both training and competition [ 1 – 5 ].Sports biomechanics research indicates that head joint stability is one of the core biomechanical factors regulating complex human motor performance. In gymnastics balance beam events, stable head posture enhances movement completion precision during jumps and rotations [ 6 ]. In figure skating triple axels, head rotational axis control determines aerial posture symmetry, whereas insufficient joint synchronization affects landing stability [ 7 ]. Freestyle swimming breathing requires precise head control, as excessive head lifting causes lower limb sinking, whereas stable head rotation optimizes stroke rhythm [ 8 ].In tennis serves, head stability enables the orderly release of upper limb explosive power, increasing racket head speed, whereas excessive head hyperextension disrupts kinetic chain sequencing, leading to amplified serve landing errors [ 9 ]. In cricket batting, stable head rotation angle control results in higher hitting accuracy, whereas insufficient head flexibility shortens bat preparation time and delays striking response [ 10 ].In the golf full swing, a neutral head position maintains the player's visual lock on ball position and target line, reducing club face open-close deviation; excessive head lateral tilt amplifies landing error.Within the kinetic chain transmission mechanism, body center of mass (COM) transfer exhibits close coordination with head stability: rational COM displacement facilitates lower limb-trunk-upper limb "chain-linked force generation," ensuring striking moment precision [ 11 – 14 ].Existing research has revealed the biomechanical value of the COM from multiple dimensions. Skill level difference studies demonstrate that advanced players achieve precise kinetic chain regulation by controlling COM fluctuation range during critical striking phases; this strategy reduces ineffective work by the core musculature and enhances energy transfer efficiency to the club head.Kinetic chain coordination research has identified significant coupling between COM lateral transfer and lower limb ground reaction force (GRF) [ 15 ]. Existing research predominantly focuses on COM characteristics during driver swings, lacking comparative analysis of COM in short iron swings, whereas differences in club physical parameters may lead to differentiation in kinetic chain COM regulation requirements.Golf biomechanics research has established multidimensional investigative trajectories around the COM and center of pressure (COP). Hobara et al. discovered through motion capture systems that professional players' COM backward displacement toward the non-target side was significantly smaller than that of amateur players; skill level difference studies revealed that professional players adopt an active regulation strategy of COM dominance with COP following [ 16 – 17 ].Investigation of specific kinematic patterns regarding the head joint and COM, as well as swing speed differences in 5-iron swings, remains a gap in current research.To further investigate the technical characteristics of full 5-iron swings among athletes of different skill levels, achieve longer and more accurate ball striking, and enhance athletic performance, the present study analyzes the kinematic characteristics of athletes at different levels through head stability, COM, and CHS across the swing cycle.Through comparative analysis between two skill levels, the present study aims to refine the foundational theoretical framework of golf swing kinematics, establish a quantifiable technical improvement framework for collegiate golf athletes, and facilitate the transformation of training paradigms from traditional "experience-dominated" approaches toward "data-supported" methodologies.The research findings not only provide support for athletes' technical refinement but also enable personalized instruction in golf pedagogy. 2. Materials and Methods 2.1 Research Subjects Table 1 presents the statistical characteristics of the twelve male golfers of different skill levels from Tianjin University of Sport (all right-handed) were recruited as experimental participants for 5-iron full swing data collection.Inclusion criteria: Participants were required to be physically healthy, with no injury history within the previous 6 months, no cardiovascular diseases or any contraindications, no history of major sports injuries such as severe muscle strains, and in good physical condition during the testing period.This study was approved by all participants signed informed consent forms.Tianjin University of Sport (TJUS2024 − 062). The recruitment period for this study is from December 30, 024 to January 20, 2025. Table 1 Basic Information of Athletes( \(\:\stackrel{-}{\text{x}}\pm\:\text{s}\) , n=12) Level Age (y) Ball Age (y) Height (m) Body Mass (kg) National Level Athletes 21.33 ± 1.53 5.33 ± 4.04 1.75 ± 0.04 72.00 ± 11.54 National second-level athlete 21.00 ± 1.73 5.33 ± 3.22 1.77 ± 0.05 78.82 ± 1.28 2.2 Experimental Protocol The experiment was conducted in a standardized indoor sports biomechanics laboratory. A golf swing-specific hitting cage measuring 3.15 m (length) × 1.6 m (width) × 2.8 m (height) was constructed to define the swing space, with crash pads placed 4.5 m from the cage exit on the outer side to ensure safety. The Qualisys motion capture system (Qualisys Track Manager, Sweden) was employed, with the high-speed camera sampling frequency set at 250 Hz. On-site data scanning was performed using a T-shaped wand, and a virtual coordinate system was established using an L-shaped frame. The coordinate system was configured according to the operational specifications of Visual3D 2020 software (X-axis: mediolateral direction, positive toward the target; Y-axis: anterior-posterior direction, positive toward the participant's body; Z-axis: vertical direction, positive pointing upward). Participants were required to wear tight-fitting athletic pants, remain bare-chested, and bring their own equipment conforming to R&A golf rules, including a 5-iron club, non-slip golf glove, and professional golf shoes. A standardized 10-minute warm-up, consisting of 3 minutes of dynamic stretching, 4 minutes of practice swings, and 3 minutes of ball-striking practice, was performed to facilitate adaptation to the environment and prevent injury. Two trained experimenters affixed reflective markers using a 16-mm infrared reflective passive marker set based on the Qualisys Sports Marker Set-golf model. A total of 41 markers (35 on the body) were positioned on the head, trunk, upper limbs, and lower limbs and secured to the skin with hypoallergenic medical tape. Prior to marker placement, the experimental procedures were explained to the participants to minimize psychological interference. After placement, system pre-scanning was performed to confirm clear marker identification. During testing, participants stood on the hitting mat with feet shoulder-width apart and stance angle adjusted according to individual preference. After the experimenters confirmed a stable stance and normal marker recognition, a "start" command was issued. Five valid swing trials were collected from each participant. To avoid fatigue from striking, a 30-second interval was maintained between each swing. 2.3 Data Processing The golf model in Visual3D (C-Motion, Inc., USA) was employed to screen, interpolate, and process biomechanical indicators. The motion capture data were filtered using a bidirectional Butterworth low-pass filter with a cutoff frequency of 6 Hz and aligned according to timestamps. 2.4 Statistical analysis Biomechanical parameters of the golf full swing were first averaged within participants and then across participants to generate mean ± standard deviation normalized curves. Cycle normalization and curve generation were performed using custom algorithms developed in MATLAB (The MathWorks, Natick, MA). Each swing was normalized across the golf cycle phases, from the address position (0%) to follow-through completion (100%). Data were summarized and integrated using Excel 2019, means of valid data were calculated, and Shapiro-Wilk normality tests were conducted using SPSS 27.0 software. The data conformed to a normal distribution. Statistical significance was set at p < 0.05, with high significance defined as p < 0.01. Statistical Parametric Mapping (SPM) was employed to conduct statistical inference on continuous time-series data throughout the full swing cycle. Time periods exhibiting significant differences between the two groups across the entire movement cycle were identified. 2.4 Definition of Indicators Center of mass (COM): In biomechanics, the center of mass (COM) is the average position of mass distribution in an object, representing the concentrated point of action in mechanical analysis. Head displacement: Position changes of the head in three-dimensional space, which collectively reflect body postural stability in conjunction with COM displacement. Head angle: Angular changes of the head relative to the trunk in three-dimensional space (sagittal, coronal, and horizontal planes), used to quantify head position and movement status. Clubhead speed (CHS): Velocity components of the clubhead in three-dimensional directions (X-CHS, Y-CHS, Z-CHS), used to evaluate ball-striking power output. National-level athletes: Athletes placing 9th–12th individually or 5th–8th in team competition (meeting playing requirements) in the National Golf Championships or China Open (Professional); 4th–6th individually in the National Amateur Championships, China Amateur Open, China Amateur Championship, National Amateur Elite Tournament, or Chinese University Golf Championships (Super Division); top 3 individually in Chinese University Golf Championships (Professional Division) or China Junior Level-1 Series (Group A, maximum 6 events annually); 21st–50th in China Professional Year-End Rankings; 11th–30th in National Amateur Year-End Rankings; top 20 in National Junior Year-End Rankings (Group A); or top 2 individually or in team competition (meeting playing requirements) in provincial games or provincial sports administration championships (or title competitions). National second-level athletes: Athletes placing 3rd–8th individually or 3rd–4th in team competition (meeting playing requirements) in provincial games or provincial sports administration championships (or title competitions). 3. Results 3.1 Club Head Speed Figure 1 illustrates the three-dimensional velocity component characteristics of athletes at varying skill levels during critical phases of the movement. During the 20%–40% swing cycle, X-CHS of national-level athletes was significantly lower than that of national second-level athletes (t = − 1.562, d = − 0.462). During the 70%–80% swing cycle, X-CHS of national-level athletes was significantly higher than that of national second-level athletes (t = 0.253, d = 0.272). During the 80%–90% swing cycle, Y-CHS of national-level athletes was significantly higher than that of national second-level athletes (t = 1.625, d = 0.321). During the 20%–40% swing cycle, Z-CHS of national-level athletes was significantly higher than that of national second-level athletes (t = 4.819, d = 1.621). During the 50%–80% swing cycle, Z-CHS of national-level athletes was significantly lower than that of national second-level athletes (t = − 3.118, d = 0.610). 3.2 Head Kinematic Characteristics Figure 2 displays Head joint forward lean angle: Throughout the 0%–100% swing cycle, the forward lean angle of national-level athletes was significantly greater than that of national second-level athletes (t = − 3.887, d = − 0.916). Lateral tilt angle: During the 0%–40% swing cycle, national-level athletes demonstrated smaller angles than national second-level athletes (t = − 2.44, d = − 0.567). During the 40%–100% swing cycle, national-level athletes showed significantly greater angles than national second-level athletes (t = 2.507, d = 0.776). Rotation angle: During the 40%–60% swing cycle, national-level athletes exhibited smaller angles than national second-level athletes (t = − 5.237, d = − 1.875). Figure 3 presents the correlation analysis revealed that during the 2%–30% swing cycle, the head forward lean angle of national-level athletes showed a negative correlation with X-CHS (r = − 0.685, p = 0.002). During the 78%–85% swing cycle, the head forward lean angle showed a positive correlation with X-CHS (r = 0.689, p < 0.001). During the 0%–20% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r = − 0.695, p = 0.004). During the 31%–43% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r = − 0.508, p = 0.003). During the 55%–68% swing cycle, the head rotation angle showed a positive correlation with Z-CHS (r = 0.648, p = 0.01). For national second-level athletes, during the 27%–73% swing cycle, the head forward lean angle exhibited a strong negative correlation with X-CHS (r = − 0.733, p = 0.002). During the 48%–60% swing cycle, the head forward lean angle exhibited a strong positive correlation with X-CHS (r = 0.704, p = 0.002). During the 88%–94% swing cycle, the head forward lean angle showed a significant positive correlation with X-CHS (r = 0.706, p = 0.002). During the 15%–35% swing cycle, the head lateral tilt angle showed a significant negative correlation with Y-CHS (r = − 0.728, p = 0.003). During the 39%–47% swing cycle, the head lateral tilt angle showed a significant positive correlation with Y-CHS (r = 0.692, p = 0.003). During the 54%–73% swing cycle, the head lateral tilt angle showed a significant negative correlation with Y-CHS (r = − 0.615, p = 0.002). During the 75%–82% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r = − 0.891, p < 0.001). During the 84%–90% swing cycle, the head rotation angle showed a positive correlation with Z-CHS (r = 0.751, p = 0.003). Note 1 Ⅰ denotes national-level athletes; Ⅱ denotes national second-level athletes. Table 2 displays mean head displacement in the anterior-posterior direction: During the 88%–100% swing cycle, head displacement of national-level athletes was significantly greater than that of national second-level athletes (t = 3.194, p = 0.005, d = 0.974). Mediolateral direction: Throughout the 0%–100% swing cycle, head displacement of national-level athletes was significantly greater than that of national second-level athletes (t = 5.069, p < 0.0001, d = 1.735). Vertical direction: During the 0%–47% swing cycle, head displacement of national-level athletes was significantly smaller than that of national second-level athletes (t = 3.315, p = 0.002, d = 0.884). During the 75%–100% swing cycle, head displacement of national-level athletes was significantly smaller than that of national second-level athletes (t = − 3.045, p = 0.009, d = − 0.791). Table 2 Head Displacement Parameters Characteristic Kinematics parameters Athlete Grading Differential interval t p d Head displacement X National Level Athletes 88%-100% 3.194 0.005 0.974 National second-level athlete Head displacement Y National Level Athletes 0%-100% 5.069 <0.0001 1.735 National second-level athlete Head displacement Z National Level Athletes 0%-47%, 75%-100% 3.315, -3.045 0.002,0.009, 0.884,-0.791 National second-level athlete 3.3 Center of Mass Characteristics Center of mass (COM) in the anterior-posterior direction(see Table 3 ): During the 84%–100% swing cycle, anterior-posterior COM displacement of national-level athletes was significantly greater than that of national second-level athletes (t = 2.226, p = 0.024, d = 1.134). Mediolateral direction: Throughout the 0%–100% swing cycle, mediolateral COM displacement of national-level athletes was significantly greater than that of national second-level athletes (t = 3.942, p = 0.001, d = 1.134). Vertical direction: During the 0%–5% swing cycle, vertical COM displacement of national-level athletes was significantly smaller than that of national second-level athletes (t = − 1.991, p = 0.046, d = − 0.051). Table 3 COM Characteristics at Different Level Kinematics parameters Athlete Grading Differential interval t p d COMX National Level Athletes 84%-100% 2.226 0.024 0.652 National second-level athlete COMY National Level Athletes 0%-100% 3.946 0.001, 0.003 1.134 National second-level athlete COMZ National Level Athletes 0%-5% -1.991 0.046 -0.051 National second-level athlete Figure 4 provides during the 44%–54% swing cycle, head displacement along the X-axis of national-level athletes showed a negative correlation with X-CHS (r = − 0.526, p = 0.006). During the 63%–72% swing cycle, head displacement along the X-axis showed a positive correlation with X-CHS (r = 0.459, p = 0.018). During the 57%–70% swing cycle, head displacement along the Y-axis showed a positive correlation with Y-CHS (r = 0.651, p = 0.003). During the 74%–80% swing cycle, head displacement along the Y-axis showed a negative correlation with Y-CHS (r = − 0.727, p < 0.001).During the 47%–54% swing cycle, head displacement along the Z-axis showed a positive correlation with Z-CHS (r = 0.449, p = 0.007). During the 70%–78% swing cycle, head displacement along the Z-axis showed a positive correlation with Z-CHS (r = 0.595, p = 0.015). During the 4%–26% swing cycle, head displacement along the X-axis of national second-level athletes showed a negative correlation with X-CHS (r = − 0.764, p = 0.002). During the 29%–47% swing cycle, head displacement along the X-axis showed a positive correlation with X-CHS (r = 0.715, p = 0.003). During the 51%–78% swing cycle, head displacement along the X-axis showed a negative correlation with X-CHS (r = − 0.815, p = 0.001). During the 5%–12% swing cycle, head displacement along the Z-axis showed a significant positive correlation with Z-CHS (r = 0.478, p = 0.014). During the 14%–39% swing cycle, head displacement along the Z-axis showed a significant positive correlation with Z-CHS (r = 0.597, p = 0.004). During the 46%–59% swing cycle, head displacement along the Z-axis showed a significant negative correlation with Z-CHS (r = − 0.615, p = 0.004). During the 46%–63% swing cycle, COM along the X-axis of national-level athletes showed a negative correlation with X-CHS (r = − 0.635, p = 0.008). During the 33%–44% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r = 0.686, p = 0.004). During the 60%–71% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r = 0.624, p = 0.004). During the 74%–81% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r = − 0.711, p = 0.002). During the 83%–90% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r = − 0.682, p = 0.002). During the 10%–40% swing cycle, COM along the Z-axis showed a negative correlation with Z-CHS (r = − 0.527, p = 0.004). For national second-level athletes, during the 29%–46% swing cycle, COM along the X-axis showed a negative correlation with X-CHS (r = − 0.751, p = 0.001). During the 51%–78% swing cycle, COM along the X-axis showed a positive correlation with X-CHS (r = 0.818, p < 0.001). During the 38%–47% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r = 0.617, p = 0.005). During the 57%–64% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r = − 0.525, p = 0.013). During the 6%–36% swing cycle, COM along the Z-axis showed a positive correlation with Z-CHS (r = 0.812, p < 0.001). During the 40%–60% swing cycle, COM along the Z-axis showed a significant negative correlation with Z-CHS (r = − 0.661, p = 0.005). For national-level athletes, COM along the X-axis and head displacement along the X-axis showed a significant negative correlation during the 8%–62% swing cycle (r = − 0.533, p = 0.01). COM along the Y-axis and head displacement along the Y-axis showed a significant positive correlation during the 0%–9% swing cycle (r = 0.889, p = 0.004). COM along the Z-axis and head displacement along the Z-axis showed a significant positive correlation during the 0%–54% and 72%–77% swing cycles (r = 0.667, 0.559; p = 0.001, 0.003, respectively). For national second-level athletes, COM along the X-axis and head displacement along the X-axis showed a significant positive correlation throughout the 0%–100% swing cycle (r = 0.971, p = 0.001). COM along the Y-axis and head displacement along the Y-axis showed a significant positive correlation throughout the 0%–100% swing cycle (r = 0.947, p = 0.001). COM along the Z-axis and head displacement along the Z-axis showed a significant positive correlation throughout the 0%–100% swing cycle (r = 0.748, p = 0.001). (see Table 4 ) Table 4 Correlation Between COM and Head Displacement Continuity Kinematics parameters Kinematics parameters Relevance interval r p Ⅰ-COMX Ⅰ-Head displacement X 8%-62% -0.533 0.001 Ⅱ-COMX Ⅱ-Head displacement X 0%-100% 0.971 0.001 Ⅰ-COMY Ⅰ-Head displacement Y 0%-9% 0.889 0.004 Ⅱ-COMY Ⅱ-Head displacement Y 0%-100% 0.947 0.001 Ⅰ-COMZ Ⅰ-Head displacement Z 0%-54%, 72%-77% 0.667, 0.559 0.001, 0.003 Ⅱ-COMZ Ⅱ-Head displacement Z 0%-100% 0.748 0.001 Note 1 : Ⅰ denotes national-level athletes; Ⅱ denotes national second-level athletes. 3. Discussion The present study compared CHS velocity components, head posture, and COM displacement between national-level and national second-level golfers throughout the full swing cycle, revealing the biomechanical characteristics of head stability and CHS during 5-iron swings among athletes of varying skill levels. The study found that during the 20%–40% swing cycle, the absolute value of X-CHS in national-level athletes was greater than that in national second-level athletes, indicating that national-level athletes initiated movement away from the target direction more rapidly in the early swing phase [ 18 ]. During the 70%–80% swing cycle, the X-axis velocity component rapidly transitions from moving away from the target to moving toward the target, with the X-CHS nadir of national-level athletes occurring at 75%, earlier than the 77% observed in national second-level athletes, demonstrating that national-level athletes completed the velocity direction transition earlier. This is consistent with findings that clubhead angular velocity continuously increases during the downswing release phase in elite athletes [ 19 ]. During the 20%–40% swing cycle, Z-CHS of national-level athletes was greater than that of national second-level athletes, indicating that national-level athletes accumulate energy through body lowering and power storage. During the 50%–80% swing cycle, the absolute value of Z-CHS in national-level athletes was greater than that in national second-level athletes, which represents efficient conversion of vertical potential energy to horizontal kinetic energy [ 20 ]. Head angle changes are important biomechanical characteristics during the swing process, reflecting players' perception of ball position and visual lock on the target line [ 21 ]. The present study found that throughout the full swing cycle, the head forward lean angle of national-level athletes was significantly greater than that of national second-level athletes. This indicates that national-level athletes synchronously adjust the head forward lean angle with clubhead acceleration and exhibit gradual lateral tilt, similar to head lateral tilt changes in professional players. During the 2%–30% swing cycle, the head forward lean angle of national-level athletes correlates with X-CHS to avoid body rotational axis deviation during power transfer. Elite golfers maintain movement coordination through phase-specific regulation of head forward lean [ 22 ]. Professional players maintain a highly neutral head position during iron address setup to achieve more solid downward ball striking [ 23 ]. During the 0%–40% swing cycle, the degree of head lateral tilt in national-level athletes was smaller than that in national second-level athletes. During the 5-iron address position, national-level athletes maintain neutrality and show a positive correlation with clubhead movement, thereby maintaining spinal angle stability by restricting excessive head forward lean during this cycle [ 24 ]. During the 78%–85% swing cycle, the head forward lean angle showed a positive correlation with X-CHS, demonstrating that national-level athletes exhibit moderate head forward lean after ball contact to coordinate with body extension toward the target direction [ 25 ]. National second-level athletes exhibited a negative correlation between head forward lean angle and X-CHS during the 27%–73% swing cycle, while showing a positive correlation during the 48%–60% swing cycle, reflecting instability in head posture control among national second-level athletes, which is detrimental to CHS stability [ 26 ]. During the 0%–20% swing cycle, the head faces toward the target direction, thereby restricting premature hip rotation, which is a prerequisite for establishing the X-factor [ 27 ]. During the 31%–43% swing cycle, national-level athletes maintained a rotation pattern where the head lags behind the body [ 28 ]. During the 55%–68% swing cycle, the head begins active rotation to release stored elastic potential energy. National second-level athletes exhibited a different pattern of head rotation; the negative correlation during the 75%–82% swing cycle can increase the absolute value of Z-CHS, with the head maintaining a more leftward rotation angle (for right-handed players), helping players achieve greater downward CHS. During the 15%–35% swing cycle, national second-level athletes showed a significant negative correlation between head lateral tilt angle and Y-CHS, a positive correlation during the 39%–47% swing cycle, and a negative correlation during the 54%–73% swing cycle. The multiphase head change pattern aligns with the swing trajectory [ 29 ]. This correlation was not observed in national-level athlete data, demonstrating that the head serves only as functional coordination rather than an active power generation site, which is consistent with research findings that ground reaction force peaks occur during mid-downswing rather than at ball contact in elite athletes [ 30 ]. Throughout the 0%–100% full swing cycle, national-level athletes exhibited a greater displacement range in head lateral movement and Y-COM compared to national second-level athletes, because national-level athletes demonstrate more rightward tilt of head and COM during address setup, which generates greater lateral displacement amplitude as the club moves [ 31 ]. During the 46%–63% swing cycle, national-level athletes showed a negative correlation between AP-COM and X-CHS; during this phase, players maintain rotational axis stability and achieve efficient energy transfer by restricting forward COM movement toward the target direction. During the 51%–78% swing cycle, forward COM movement of national second-level athletes was synchronized with X-CHS. National-level athletes exhibited multiphase changes in ML-COM regulation: a positive correlation during the 33%–44% and 60%–71% swing cycles, and a negative correlation during the 74%–81% and 83%–90% swing cycles. The multiphase changes reflect that dynamic regulation ensures improved conversion efficiency of horizontal kinetic energy, achieving greater clubhead speed [ 32 ]. During the 6%–36% swing cycle, national second-level athletes' vertical-COM showed a positive correlation with Z-CHS, which transitioned to a negative correlation during the 40%–60% swing cycle, demonstrating that national second-level athletes increase vertical-COM during early backswing to complete upward club initiation, and active COM lowering during the 40%–60% swing cycle assists club potential energy accumulation. Differences exist in head displacement-swing speed coupling between national-level and national second-level athletes; national-level athletes exhibited higher correlation between ML-head displacement and Y-CHS during the 51%–80% swing cycle. National second-level athletes exhibited higher correlation between vertical-head displacement and Z-CHS during the 40%–65% swing cycle. This indicates that national-level athletes establish strong coupling between head displacement and swing speed earlier than the downswing phase and maintain it through ball contact. National second-level athletes exhibit coupling with CHS only during the 40%–65% swing cycle, meaning that head displacement characteristics of national second-level athletes do not correlate with CHS after the backswing peak. Throughout the 0%–100% full swing cycle, AP-COM of national second-level athletes was completely synchronized with anterior-posterior head displacement. During the 8%–62% swing cycle, national-level athletes exhibited antagonistic characteristics between AP-COM and anterior-posterior head displacement, which is consistent with research findings that elite athletes demonstrate greater shoulder-hip separation angles. 4. Conclusion National-level athletes maintained a greater head forward lean angle throughout the full swing cycle, coordinating with the downswing to follow-through phases to establish a stable rotational axis. National second-level athletes exhibited fluctuating characteristics in head posture control. National-level athletes maintained rotational axis stability by restricting premature forward COM movement, thereby ensuring efficient energy transfer along the vertical axis to the clubhead. National-level athletes demonstrated a faster velocity direction transition during the downswing phase and achieved greater club head speed at ball contact. National second-level athletes lacked temporal coordination among three-dimensional velocity components, resulting in energy dispersion at ball contact and limited overall swing speed performance. It is recommended that athletes perform the following training protocols: stance position holding with ball training, 5–6 times per week, 4–6 sets × 60 seconds per session. Backswing peak head static hold training, 4–5 times per week, 3–5 sets × 10 repetitions per session. Focal point fixation swing training, 5–7 times per week, 3–4 sets × 12–15 repetitions per session. These training protocols will enhance head and COM stability during the swing. Declarations Institutional Review Board Statement: Ethical approval was granted by the Ethics Review of Tianjin Institute of Physical Education at Tianjin University of Sport, Tianjin, China (Application Number: TJUS2024-062) All participants signed informed consent forms. Funding: This research was supported by Basic Research Business Funding Project of China Institute of Sport Science, General Administration of Sport of China Basic[ 22-09].All procedures described in this study were performed following the principles of the Declaration of Helsinki. Availability of data and material: The data are available upon request from the authors Author Contributions Conceptualization, L.H. and B.L.; methodology, L.H. and Z.W.; software H.L. and CL, validation, LH, C.L and C.l, formal analysis, HL.; investigation, C.L.; resources B.L.; data curation, H.Z; writing-original draft preparation, L.H.; writing-review and editing L.H, visualization, C.L; supervision, L.C., project administration, B.L.,; funding acquisition,Z.W All authors have read and agreed to the published version of the manuscript. Acknowledgmentse: The authors would like to thank the college golfers for their contributions, as well as the Sports Biomechanics Laboratory of Tianjin University of port for its support in the research on golf. References YANG C-C, CHANG C-C, CHAO T, et al. The effects of different iron shaft weights on golf swing performance [J]. Front Bioeng Biotechnol. 2024;12:1343530. SHAN G, ZHANG X, LI X, et al. 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Supplementary Files Supplementarymaterial.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 06 Jan, 2026 Reviewers agreed at journal 30 Dec, 2025 Reviewers invited by journal 23 Dec, 2025 Editor invited by journal 02 Dec, 2025 Editor assigned by journal 30 Nov, 2025 Submission checks completed at journal 30 Nov, 2025 First submitted to journal 26 Nov, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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2","display":"","copyAsset":false,"role":"figure","size":2348492,"visible":true,"origin":"","legend":"Head Kinematic Parameters","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8213762/v1/a4a5919e71c1fce1491fb44a.png"},{"id":99217840,"identity":"78f1c583-db07-4762-b226-c1476c1c07ac","added_by":"auto","created_at":"2025-12-30 09:12:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":127534,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation Between Head Kinematic and CHS\u003c/p\u003e\n\u003cp\u003eNote 1:Ⅰ denotes national-level athletes; Ⅱdenotes national second-level athletes.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8213762/v1/9e69caa18e3c1a2f0006c886.png"},{"id":99316666,"identity":"cd9e8b17-b8b9-4ea8-a98e-c47f79eab4d9","added_by":"auto","created_at":"2025-12-31 16:28:55","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":183116,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation Between Head Displacement ,COM and CHS\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8213762/v1/208cd48bd1b4ae0664cba2d8.png"},{"id":99217843,"identity":"ca92ad9c-8869-421a-8ae1-19909529a17e","added_by":"auto","created_at":"2025-12-30 09:12:06","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":10784,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-8213762/v1/76bbe397936add80787132f1.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of Head Kinematics and COM on CHS of 5-Iron Among Male Golfers of Varied Skill Levels","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eGolf is a precision sport that demands high levels of body control, requiring athletes to maintain exceptional stability and coordination throughout the swing motion to achieve precise control over ball-striking outcomes.Within the diversified club system, the 5-iron combines medium- to long-distance striking demands with precision landing requirements. Compared to short irons, it requires greater swing speed stability to ensure distance output; compared to the driver, it demands more stringent control precision over club face angle. Consequently, the 5-iron swing technique serves not only as a core indicator for assessing athletes' skill levels but also as a critical technical vehicle in both training and competition [\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].Sports biomechanics research indicates that head joint stability is one of the core biomechanical factors regulating complex human motor performance. In gymnastics balance beam events, stable head posture enhances movement completion precision during jumps and rotations [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In figure skating triple axels, head rotational axis control determines aerial posture symmetry, whereas insufficient joint synchronization affects landing stability [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Freestyle swimming breathing requires precise head control, as excessive head lifting causes lower limb sinking, whereas stable head rotation optimizes stroke rhythm [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].In tennis serves, head stability enables the orderly release of upper limb explosive power, increasing racket head speed, whereas excessive head hyperextension disrupts kinetic chain sequencing, leading to amplified serve landing errors [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In cricket batting, stable head rotation angle control results in higher hitting accuracy, whereas insufficient head flexibility shortens bat preparation time and delays striking response [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].In the golf full swing, a neutral head position maintains the player's visual lock on ball position and target line, reducing club face open-close deviation; excessive head lateral tilt amplifies landing error.Within the kinetic chain transmission mechanism, body center of mass (COM) transfer exhibits close coordination with head stability: rational COM displacement facilitates lower limb-trunk-upper limb \"chain-linked force generation,\" ensuring striking moment precision [\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].Existing research has revealed the biomechanical value of the COM from multiple dimensions. Skill level difference studies demonstrate that advanced players achieve precise kinetic chain regulation by controlling COM fluctuation range during critical striking phases; this strategy reduces ineffective work by the core musculature and enhances energy transfer efficiency to the club head.Kinetic chain coordination research has identified significant coupling between COM lateral transfer and lower limb ground reaction force (GRF) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Existing research predominantly focuses on COM characteristics during driver swings, lacking comparative analysis of COM in short iron swings, whereas differences in club physical parameters may lead to differentiation in kinetic chain COM regulation requirements.Golf biomechanics research has established multidimensional investigative trajectories around the COM and center of pressure (COP). Hobara et al. discovered through motion capture systems that professional players' COM backward displacement toward the non-target side was significantly smaller than that of amateur players; skill level difference studies revealed that professional players adopt an active regulation strategy of COM dominance with COP following [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].Investigation of specific kinematic patterns regarding the head joint and COM, as well as swing speed differences in 5-iron swings, remains a gap in current research.To further investigate the technical characteristics of full 5-iron swings among athletes of different skill levels, achieve longer and more accurate ball striking, and enhance athletic performance, the present study analyzes the kinematic characteristics of athletes at different levels through head stability, COM, and CHS across the swing cycle.Through comparative analysis between two skill levels, the present study aims to refine the foundational theoretical framework of golf swing kinematics, establish a quantifiable technical improvement framework for collegiate golf athletes, and facilitate the transformation of training paradigms from traditional \"experience-dominated\" approaches toward \"data-supported\" methodologies.The research findings not only provide support for athletes' technical refinement but also enable personalized instruction in golf pedagogy.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Research Subjects\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the statistical characteristics of the twelve male golfers of different skill levels from Tianjin University of Sport (all right-handed) were recruited as experimental participants for 5-iron full swing data collection.Inclusion criteria: Participants were required to be physically healthy, with no injury history within the previous 6 months, no cardiovascular diseases or any contraindications, no history of major sports injuries such as severe muscle strains, and in good physical condition during the testing period.This study was approved by all participants signed informed consent forms.Tianjin University of Sport (TJUS2024\u0026thinsp;\u0026minus;\u0026thinsp;062). The recruitment period for this study is from December 30, 024 to January 20, 2025.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic Information of Athletes(\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{\\text{x}}\\pm\\:\\text{s}\\)\u003c/span\u003e\u003c/span\u003e, n=12)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLevel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAge (y)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBall Age (y)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHeight (m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBody Mass (kg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNational Level Athletes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e21.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.33\u0026thinsp;\u0026plusmn;\u0026thinsp;4.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e72.00\u0026thinsp;\u0026plusmn;\u0026thinsp;11.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNational second-level athlete\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e21.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e1.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e78.82\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental Protocol\u003c/h2\u003e \u003cp\u003eThe experiment was conducted in a standardized indoor sports biomechanics laboratory. A golf swing-specific hitting cage measuring 3.15 m (length) \u0026times; 1.6 m (width) \u0026times; 2.8 m (height) was constructed to define the swing space, with crash pads placed 4.5 m from the cage exit on the outer side to ensure safety. The Qualisys motion capture system (Qualisys Track Manager, Sweden) was employed, with the high-speed camera sampling frequency set at 250 Hz. On-site data scanning was performed using a T-shaped wand, and a virtual coordinate system was established using an L-shaped frame. The coordinate system was configured according to the operational specifications of Visual3D 2020 software (X-axis: mediolateral direction, positive toward the target; Y-axis: anterior-posterior direction, positive toward the participant's body; Z-axis: vertical direction, positive pointing upward). Participants were required to wear tight-fitting athletic pants, remain bare-chested, and bring their own equipment conforming to R\u0026amp;A golf rules, including a 5-iron club, non-slip golf glove, and professional golf shoes. A standardized 10-minute warm-up, consisting of 3 minutes of dynamic stretching, 4 minutes of practice swings, and 3 minutes of ball-striking practice, was performed to facilitate adaptation to the environment and prevent injury. Two trained experimenters affixed reflective markers using a 16-mm infrared reflective passive marker set based on the Qualisys Sports Marker Set-golf model. A total of 41 markers (35 on the body) were positioned on the head, trunk, upper limbs, and lower limbs and secured to the skin with hypoallergenic medical tape. Prior to marker placement, the experimental procedures were explained to the participants to minimize psychological interference. After placement, system pre-scanning was performed to confirm clear marker identification. During testing, participants stood on the hitting mat with feet shoulder-width apart and stance angle adjusted according to individual preference. After the experimenters confirmed a stable stance and normal marker recognition, a \"start\" command was issued. Five valid swing trials were collected from each participant. To avoid fatigue from striking, a 30-second interval was maintained between each swing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Data Processing\u003c/h2\u003e \u003cp\u003eThe golf model in Visual3D (C-Motion, Inc., USA) was employed to screen, interpolate, and process biomechanical indicators. The motion capture data were filtered using a bidirectional Butterworth low-pass filter with a cutoff frequency of 6 Hz and aligned according to timestamps.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e \u003cp\u003eBiomechanical parameters of the golf full swing were first averaged within participants and then across participants to generate mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation normalized curves. Cycle normalization and curve generation were performed using custom algorithms developed in MATLAB (The MathWorks, Natick, MA). Each swing was normalized across the golf cycle phases, from the address position (0%) to follow-through completion (100%). Data were summarized and integrated using Excel 2019, means of valid data were calculated, and Shapiro-Wilk normality tests were conducted using SPSS 27.0 software. The data conformed to a normal distribution. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, with high significance defined as p\u0026thinsp;\u0026lt;\u0026thinsp;0.01. Statistical Parametric Mapping (SPM) was employed to conduct statistical inference on continuous time-series data throughout the full swing cycle. Time periods exhibiting significant differences between the two groups across the entire movement cycle were identified.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Definition of Indicators\u003c/h2\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eCenter of mass (COM): In biomechanics, the center of mass (COM) is the average position of mass distribution in an object, representing the concentrated point of action in mechanical analysis.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eHead displacement: Position changes of the head in three-dimensional space, which collectively reflect body postural stability in conjunction with COM displacement.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eHead angle: Angular changes of the head relative to the trunk in three-dimensional space (sagittal, coronal, and horizontal planes), used to quantify head position and movement status.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eClubhead speed (CHS): Velocity components of the clubhead in three-dimensional directions (X-CHS, Y-CHS, Z-CHS), used to evaluate ball-striking power output.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eNational-level athletes: Athletes placing 9th\u0026ndash;12th individually or 5th\u0026ndash;8th in team competition (meeting playing requirements) in the National Golf Championships or China Open (Professional); 4th\u0026ndash;6th individually in the National Amateur Championships, China Amateur Open, China Amateur Championship, National Amateur Elite Tournament, or Chinese University Golf Championships (Super Division); top 3 individually in Chinese University Golf Championships (Professional Division) or China Junior Level-1 Series (Group A, maximum 6 events annually); 21st\u0026ndash;50th in China Professional Year-End Rankings; 11th\u0026ndash;30th in National Amateur Year-End Rankings; top 20 in National Junior Year-End Rankings (Group A); or top 2 individually or in team competition (meeting playing requirements) in provincial games or provincial sports administration championships (or title competitions).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eNational second-level athletes: Athletes placing 3rd\u0026ndash;8th individually or 3rd\u0026ndash;4th in team competition (meeting playing requirements) in provincial games or provincial sports administration championships (or title competitions).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Club Head Speed\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the three-dimensional velocity component characteristics of athletes at varying skill levels during critical phases of the movement. During the 20%\u0026ndash;40% swing cycle, X-CHS of national-level athletes was significantly lower than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.562, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.462). During the 70%\u0026ndash;80% swing cycle, X-CHS of national-level athletes was significantly higher than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;0.253, d\u0026thinsp;=\u0026thinsp;0.272). During the 80%\u0026ndash;90% swing cycle, Y-CHS of national-level athletes was significantly higher than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;1.625, d\u0026thinsp;=\u0026thinsp;0.321). During the 20%\u0026ndash;40% swing cycle, Z-CHS of national-level athletes was significantly higher than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;4.819, d\u0026thinsp;=\u0026thinsp;1.621). During the 50%\u0026ndash;80% swing cycle, Z-CHS of national-level athletes was significantly lower than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.118, d\u0026thinsp;=\u0026thinsp;0.610).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Head Kinematic Characteristics\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays Head joint forward lean angle: Throughout the 0%\u0026ndash;100% swing cycle, the forward lean angle of national-level athletes was significantly greater than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.887, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.916). Lateral tilt angle: During the 0%\u0026ndash;40% swing cycle, national-level athletes demonstrated smaller angles than national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.44, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.567). During the 40%\u0026ndash;100% swing cycle, national-level athletes showed significantly greater angles than national second-level athletes (t\u0026thinsp;=\u0026thinsp;2.507, d\u0026thinsp;=\u0026thinsp;0.776). Rotation angle: During the 40%\u0026ndash;60% swing cycle, national-level athletes exhibited smaller angles than national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;5.237, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.875).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the correlation analysis revealed that during the 2%\u0026ndash;30% swing cycle, the head forward lean angle of national-level athletes showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.685, p\u0026thinsp;=\u0026thinsp;0.002). During the 78%\u0026ndash;85% swing cycle, the head forward lean angle showed a positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.689, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). During the 0%\u0026ndash;20% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.695, p\u0026thinsp;=\u0026thinsp;0.004). During the 31%\u0026ndash;43% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.508, p\u0026thinsp;=\u0026thinsp;0.003). During the 55%\u0026ndash;68% swing cycle, the head rotation angle showed a positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.648, p\u0026thinsp;=\u0026thinsp;0.01). For national second-level athletes, during the 27%\u0026ndash;73% swing cycle, the head forward lean angle exhibited a strong negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.733, p\u0026thinsp;=\u0026thinsp;0.002). During the 48%\u0026ndash;60% swing cycle, the head forward lean angle exhibited a strong positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.704, p\u0026thinsp;=\u0026thinsp;0.002). During the 88%\u0026ndash;94% swing cycle, the head forward lean angle showed a significant positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.706, p\u0026thinsp;=\u0026thinsp;0.002). During the 15%\u0026ndash;35% swing cycle, the head lateral tilt angle showed a significant negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.728, p\u0026thinsp;=\u0026thinsp;0.003). During the 39%\u0026ndash;47% swing cycle, the head lateral tilt angle showed a significant positive correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;0.692, p\u0026thinsp;=\u0026thinsp;0.003). During the 54%\u0026ndash;73% swing cycle, the head lateral tilt angle showed a significant negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.615, p\u0026thinsp;=\u0026thinsp;0.002). During the 75%\u0026ndash;82% swing cycle, the head rotation angle showed a negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.891, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). During the 84%\u0026ndash;90% swing cycle, the head rotation angle showed a positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.751, p\u0026thinsp;=\u0026thinsp;0.003).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNote 1\u003c/strong\u003e \u003cp\u003eⅠ denotes national-level athletes; Ⅱ denotes national second-level athletes.\u003c/p\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays mean head displacement in the anterior-posterior direction: During the 88%\u0026ndash;100% swing cycle, head displacement of national-level athletes was significantly greater than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;3.194, p\u0026thinsp;=\u0026thinsp;0.005, d\u0026thinsp;=\u0026thinsp;0.974). Mediolateral direction: Throughout the 0%\u0026ndash;100% swing cycle, head displacement of national-level athletes was significantly greater than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;5.069, p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001, d\u0026thinsp;=\u0026thinsp;1.735). Vertical direction: During the 0%\u0026ndash;47% swing cycle, head displacement of national-level athletes was significantly smaller than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;3.315, p\u0026thinsp;=\u0026thinsp;0.002, d\u0026thinsp;=\u0026thinsp;0.884). During the 75%\u0026ndash;100% swing cycle, head displacement of national-level athletes was significantly smaller than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.045, p\u0026thinsp;=\u0026thinsp;0.009, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.791).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHead Displacement Parameters Characteristic\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026minus;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKinematics parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAthlete Grading\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDifferential interval\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003et\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ed\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHead displacement X\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e88%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.194\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.974\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHead displacement Y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e5.069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u0026lt;0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.735\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHead displacement Z\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0%-47%, 75%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.315, -3.045\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.002,0.009,\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.884,-0.791\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Center of Mass Characteristics\u003c/h2\u003e \u003cp\u003eCenter of mass (COM) in the anterior-posterior direction(see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e): During the 84%\u0026ndash;100% swing cycle, anterior-posterior COM displacement of national-level athletes was significantly greater than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;2.226, p\u0026thinsp;=\u0026thinsp;0.024, d\u0026thinsp;=\u0026thinsp;1.134). Mediolateral direction: Throughout the 0%\u0026ndash;100% swing cycle, mediolateral COM displacement of national-level athletes was significantly greater than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;3.942, p\u0026thinsp;=\u0026thinsp;0.001, d\u0026thinsp;=\u0026thinsp;1.134). Vertical direction: During the 0%\u0026ndash;5% swing cycle, vertical COM displacement of national-level athletes was significantly smaller than that of national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.991, p\u0026thinsp;=\u0026thinsp;0.046, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.051).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCOM Characteristics at Different Level\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026minus;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKinematics parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAthlete Grading\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDifferential interval\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003et\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ed\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOMX\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e84%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e2.226\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.652\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOMY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.946\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001, 0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.134\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCOMZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational Level Athletes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0%-5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e-1.991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e-0.051\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNational second-level athlete\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e provides during the 44%\u0026ndash;54% swing cycle, head displacement along the X-axis of national-level athletes showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.526, p\u0026thinsp;=\u0026thinsp;0.006). During the 63%\u0026ndash;72% swing cycle, head displacement along the X-axis showed a positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.459, p\u0026thinsp;=\u0026thinsp;0.018). During the 57%\u0026ndash;70% swing cycle, head displacement along the Y-axis showed a positive correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;0.651, p\u0026thinsp;=\u0026thinsp;0.003). During the 74%\u0026ndash;80% swing cycle, head displacement along the Y-axis showed a negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.727, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).During the 47%\u0026ndash;54% swing cycle, head displacement along the Z-axis showed a positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.449, p\u0026thinsp;=\u0026thinsp;0.007). During the 70%\u0026ndash;78% swing cycle, head displacement along the Z-axis showed a positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.595, p\u0026thinsp;=\u0026thinsp;0.015). During the 4%\u0026ndash;26% swing cycle, head displacement along the X-axis of national second-level athletes showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.764, p\u0026thinsp;=\u0026thinsp;0.002). During the 29%\u0026ndash;47% swing cycle, head displacement along the X-axis showed a positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.715, p\u0026thinsp;=\u0026thinsp;0.003). During the 51%\u0026ndash;78% swing cycle, head displacement along the X-axis showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.815, p\u0026thinsp;=\u0026thinsp;0.001). During the 5%\u0026ndash;12% swing cycle, head displacement along the Z-axis showed a significant positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.478, p\u0026thinsp;=\u0026thinsp;0.014). During the 14%\u0026ndash;39% swing cycle, head displacement along the Z-axis showed a significant positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.597, p\u0026thinsp;=\u0026thinsp;0.004). During the 46%\u0026ndash;59% swing cycle, head displacement along the Z-axis showed a significant negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.615, p\u0026thinsp;=\u0026thinsp;0.004). During the 46%\u0026ndash;63% swing cycle, COM along the X-axis of national-level athletes showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.635, p\u0026thinsp;=\u0026thinsp;0.008). During the 33%\u0026ndash;44% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;0.686, p\u0026thinsp;=\u0026thinsp;0.004). During the 60%\u0026ndash;71% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;0.624, p\u0026thinsp;=\u0026thinsp;0.004). During the 74%\u0026ndash;81% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.711, p\u0026thinsp;=\u0026thinsp;0.002). During the 83%\u0026ndash;90% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.682, p\u0026thinsp;=\u0026thinsp;0.002). During the 10%\u0026ndash;40% swing cycle, COM along the Z-axis showed a negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.527, p\u0026thinsp;=\u0026thinsp;0.004). For national second-level athletes, during the 29%\u0026ndash;46% swing cycle, COM along the X-axis showed a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.751, p\u0026thinsp;=\u0026thinsp;0.001). During the 51%\u0026ndash;78% swing cycle, COM along the X-axis showed a positive correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;0.818, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). During the 38%\u0026ndash;47% swing cycle, COM along the Y-axis showed a positive correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;0.617, p\u0026thinsp;=\u0026thinsp;0.005). During the 57%\u0026ndash;64% swing cycle, COM along the Y-axis showed a negative correlation with Y-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.525, p\u0026thinsp;=\u0026thinsp;0.013). During the 6%\u0026ndash;36% swing cycle, COM along the Z-axis showed a positive correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;0.812, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). During the 40%\u0026ndash;60% swing cycle, COM along the Z-axis showed a significant negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.661, p\u0026thinsp;=\u0026thinsp;0.005).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor national-level athletes, COM along the X-axis and head displacement along the X-axis showed a significant negative correlation during the 8%\u0026ndash;62% swing cycle (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.533, p\u0026thinsp;=\u0026thinsp;0.01). COM along the Y-axis and head displacement along the Y-axis showed a significant positive correlation during the 0%\u0026ndash;9% swing cycle (r\u0026thinsp;=\u0026thinsp;0.889, p\u0026thinsp;=\u0026thinsp;0.004). COM along the Z-axis and head displacement along the Z-axis showed a significant positive correlation during the 0%\u0026ndash;54% and 72%\u0026ndash;77% swing cycles (r\u0026thinsp;=\u0026thinsp;0.667, 0.559; p\u0026thinsp;=\u0026thinsp;0.001, 0.003, respectively). For national second-level athletes, COM along the X-axis and head displacement along the X-axis showed a significant positive correlation throughout the 0%\u0026ndash;100% swing cycle (r\u0026thinsp;=\u0026thinsp;0.971, p\u0026thinsp;=\u0026thinsp;0.001). COM along the Y-axis and head displacement along the Y-axis showed a significant positive correlation throughout the 0%\u0026ndash;100% swing cycle (r\u0026thinsp;=\u0026thinsp;0.947, p\u0026thinsp;=\u0026thinsp;0.001). COM along the Z-axis and head displacement along the Z-axis showed a significant positive correlation throughout the 0%\u0026ndash;100% swing cycle (r\u0026thinsp;=\u0026thinsp;0.748, p\u0026thinsp;=\u0026thinsp;0.001). (see Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrelation Between COM and Head Displacement Continuity\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026minus;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKinematics parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKinematics parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRelevance interval\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003er\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅠ-COMX\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅠ-Head displacement X\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e8%-62%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.533\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡ-COMX\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅡ-Head displacement X\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e0%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.971\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅠ-COMY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅠ-Head displacement Y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e0%-9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.889\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡ-COMY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅡ-Head displacement Y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e0%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅠ-COMZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅠ-Head displacement Z\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e0%-54%, 72%-77%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.667, 0.559\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001, 0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eⅡ-COMZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eⅡ-Head displacement Z\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c3\"\u003e \u003cp\u003e0%-100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.748\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eNote \u003cspan refid=\"FPar1\" class=\"InternalRef\"\u003e1\u003c/span\u003e: Ⅰ denotes national-level athletes; Ⅱ denotes national second-level athletes.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Discussion","content":"\u003cp\u003eThe present study compared CHS velocity components, head posture, and COM displacement between national-level and national second-level golfers throughout the full swing cycle, revealing the biomechanical characteristics of head stability and CHS during 5-iron swings among athletes of varying skill levels. The study found that during the 20%\u0026ndash;40% swing cycle, the absolute value of X-CHS in national-level athletes was greater than that in national second-level athletes, indicating that national-level athletes initiated movement away from the target direction more rapidly in the early swing phase [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. During the 70%\u0026ndash;80% swing cycle, the X-axis velocity component rapidly transitions from moving away from the target to moving toward the target, with the X-CHS nadir of national-level athletes occurring at 75%, earlier than the 77% observed in national second-level athletes, demonstrating that national-level athletes completed the velocity direction transition earlier. This is consistent with findings that clubhead angular velocity continuously increases during the downswing release phase in elite athletes [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. During the 20%\u0026ndash;40% swing cycle, Z-CHS of national-level athletes was greater than that of national second-level athletes, indicating that national-level athletes accumulate energy through body lowering and power storage. During the 50%\u0026ndash;80% swing cycle, the absolute value of Z-CHS in national-level athletes was greater than that in national second-level athletes, which represents efficient conversion of vertical potential energy to horizontal kinetic energy [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Head angle changes are important biomechanical characteristics during the swing process, reflecting players' perception of ball position and visual lock on the target line [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The present study found that throughout the full swing cycle, the head forward lean angle of national-level athletes was significantly greater than that of national second-level athletes. This indicates that national-level athletes synchronously adjust the head forward lean angle with clubhead acceleration and exhibit gradual lateral tilt, similar to head lateral tilt changes in professional players. During the 2%\u0026ndash;30% swing cycle, the head forward lean angle of national-level athletes correlates with X-CHS to avoid body rotational axis deviation during power transfer. Elite golfers maintain movement coordination through phase-specific regulation of head forward lean [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Professional players maintain a highly neutral head position during iron address setup to achieve more solid downward ball striking [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. During the 0%\u0026ndash;40% swing cycle, the degree of head lateral tilt in national-level athletes was smaller than that in national second-level athletes. During the 5-iron address position, national-level athletes maintain neutrality and show a positive correlation with clubhead movement, thereby maintaining spinal angle stability by restricting excessive head forward lean during this cycle [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. During the 78%\u0026ndash;85% swing cycle, the head forward lean angle showed a positive correlation with X-CHS, demonstrating that national-level athletes exhibit moderate head forward lean after ball contact to coordinate with body extension toward the target direction [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. National second-level athletes exhibited a negative correlation between head forward lean angle and X-CHS during the 27%\u0026ndash;73% swing cycle, while showing a positive correlation during the 48%\u0026ndash;60% swing cycle, reflecting instability in head posture control among national second-level athletes, which is detrimental to CHS stability [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. During the 0%\u0026ndash;20% swing cycle, the head faces toward the target direction, thereby restricting premature hip rotation, which is a prerequisite for establishing the X-factor [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. During the 31%\u0026ndash;43% swing cycle, national-level athletes maintained a rotation pattern where the head lags behind the body [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. During the 55%\u0026ndash;68% swing cycle, the head begins active rotation to release stored elastic potential energy. National second-level athletes exhibited a different pattern of head rotation; the negative correlation during the 75%\u0026ndash;82% swing cycle can increase the absolute value of Z-CHS, with the head maintaining a more leftward rotation angle (for right-handed players), helping players achieve greater downward CHS. During the 15%\u0026ndash;35% swing cycle, national second-level athletes showed a significant negative correlation between head lateral tilt angle and Y-CHS, a positive correlation during the 39%\u0026ndash;47% swing cycle, and a negative correlation during the 54%\u0026ndash;73% swing cycle. The multiphase head change pattern aligns with the swing trajectory [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. This correlation was not observed in national-level athlete data, demonstrating that the head serves only as functional coordination rather than an active power generation site, which is consistent with research findings that ground reaction force peaks occur during mid-downswing rather than at ball contact in elite athletes [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Throughout the 0%\u0026ndash;100% full swing cycle, national-level athletes exhibited a greater displacement range in head lateral movement and Y-COM compared to national second-level athletes, because national-level athletes demonstrate more rightward tilt of head and COM during address setup, which generates greater lateral displacement amplitude as the club moves [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. During the 46%\u0026ndash;63% swing cycle, national-level athletes showed a negative correlation between AP-COM and X-CHS; during this phase, players maintain rotational axis stability and achieve efficient energy transfer by restricting forward COM movement toward the target direction. During the 51%\u0026ndash;78% swing cycle, forward COM movement of national second-level athletes was synchronized with X-CHS. National-level athletes exhibited multiphase changes in ML-COM regulation: a positive correlation during the 33%\u0026ndash;44% and 60%\u0026ndash;71% swing cycles, and a negative correlation during the 74%\u0026ndash;81% and 83%\u0026ndash;90% swing cycles. The multiphase changes reflect that dynamic regulation ensures improved conversion efficiency of horizontal kinetic energy, achieving greater clubhead speed [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. During the 6%\u0026ndash;36% swing cycle, national second-level athletes' vertical-COM showed a positive correlation with Z-CHS, which transitioned to a negative correlation during the 40%\u0026ndash;60% swing cycle, demonstrating that national second-level athletes increase vertical-COM during early backswing to complete upward club initiation, and active COM lowering during the 40%\u0026ndash;60% swing cycle assists club potential energy accumulation. Differences exist in head displacement-swing speed coupling between national-level and national second-level athletes; national-level athletes exhibited higher correlation between ML-head displacement and Y-CHS during the 51%\u0026ndash;80% swing cycle. National second-level athletes exhibited higher correlation between vertical-head displacement and Z-CHS during the 40%\u0026ndash;65% swing cycle. This indicates that national-level athletes establish strong coupling between head displacement and swing speed earlier than the downswing phase and maintain it through ball contact. National second-level athletes exhibit coupling with CHS only during the 40%\u0026ndash;65% swing cycle, meaning that head displacement characteristics of national second-level athletes do not correlate with CHS after the backswing peak. Throughout the 0%\u0026ndash;100% full swing cycle, AP-COM of national second-level athletes was completely synchronized with anterior-posterior head displacement. During the 8%\u0026ndash;62% swing cycle, national-level athletes exhibited antagonistic characteristics between AP-COM and anterior-posterior head displacement, which is consistent with research findings that elite athletes demonstrate greater shoulder-hip separation angles.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eNational-level athletes maintained a greater head forward lean angle throughout the full swing cycle, coordinating with the downswing to follow-through phases to establish a stable rotational axis. National second-level athletes exhibited fluctuating characteristics in head posture control. National-level athletes maintained rotational axis stability by restricting premature forward COM movement, thereby ensuring efficient energy transfer along the vertical axis to the clubhead. National-level athletes demonstrated a faster velocity direction transition during the downswing phase and achieved greater club head speed at ball contact. National second-level athletes lacked temporal coordination among three-dimensional velocity components, resulting in energy dispersion at ball contact and limited overall swing speed performance. It is recommended that athletes perform the following training protocols: stance position holding with ball training, 5\u0026ndash;6 times per week, 4\u0026ndash;6 sets \u0026times; 60 seconds per session. Backswing peak head static hold training, 4\u0026ndash;5 times per week, 3\u0026ndash;5 sets \u0026times; 10 repetitions per session. Focal point fixation swing training, 5\u0026ndash;7 times per week, 3\u0026ndash;4 sets \u0026times; 12\u0026ndash;15 repetitions per session. These training protocols will enhance head and COM stability during the swing.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eInstitutional Review Board Statement:\u003c/strong\u003e Ethical approval was granted by the Ethics Review of Tianjin Institute of Physical Education at Tianjin University of Sport, Tianjin, China (Application Number: TJUS2024-062)\u0026nbsp;All participants signed informed consent forms.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by Basic Research Business Funding Project of China Institute of Sport Science, General Administration of Sport of China Basic[ 22-09].All procedures described in this study were performed following the principles of the Declaration of Helsinki.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data are available upon request from the authors\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization, L.H. and B.L.; methodology, L.H. and Z.W.; software H.L. and CL, validation, LH, C.L and C.l, formal analysis, HL.; investigation, C.L.; resources B.L.; data curation, H.Z; writing-original draft preparation, L.H.; writing-review and editing L.H, visualization, C.L; supervision, L.C., project administration, B.L.,; funding acquisition,Z.W All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgmentse:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the college golfers for their contributions, as well as the Sports Biomechanics Laboratory of Tianjin University of port for its support in the research on golf.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eYANG C-C, CHANG C-C, CHAO T, et al. The effects of different iron shaft weights on golf swing performance [J]. Front Bioeng Biotechnol. 2024;12:1343530.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSHAN G, ZHANG X, LI X, et al. Quantification of golfer-club interaction and club-type\u0026rsquo;s affect on dynamic balance during a golf swing [J]. Int J Perform Anal Sport. 2011;11(3):417\u0026ndash;26.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCORKE T W, BETZLER N F, WALLACE E S, et al. Predicting golf ball launch characteristics using iron clubhead presentation variables and the influence of mishits [J]. J Sports Eng Technol Health Care. 2022;236(2):124\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eH\u0026eacute;BERT-LOSIER K, WARDELL GL. Acute and persistence of the effects of the SuperSpeed Golf\u0026trade; weighted-club warm-up on golf driving performance and kinematics [J]. 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J Sports Sci Med. 2015;14(3):354\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTeulier C, Delignieres D. The nature of the transition between novice and skilled coordination during learning to swing[J]. Hum Mov Sci. 2007;26(3):376\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBetzler NF, Monk SA, Wallace ES et al. The relationships between driver clubhead presentation characteristics, ball launch conditions and golf shot outcomes[J]. Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2014, 228(4): 242\u0026ndash;249.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNesbit SM, Serrano M. Work and power analysis of the golf swing[J]. J sports Sci Med. 2005;4(4):520.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003evan Lier WH, van der Kamp J, Savelsbergh GJP. Perception and action in golf putting: Skill differences reflect calibration[J]. 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Front Sports Act Living. 2022;4:873526.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":false,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Golf, Postural characteristics, Club head speed, 5-iron","lastPublishedDoi":"10.21203/rs.3.rs-8213762/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8213762/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eThe present study investigates the impact of head stability characteristics on clubhead speed (CHS) during 5-iron swings in golfers of varying skill levels.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTwelve male golfers from Tianjin University of Sport were recruited as participants.The Qualisys three-dimensional motion capture system (250 Hz) was employed to collect head kinematic parameters, center of mass (COM), club head speed (CHS), and ball-striking performance indicators.Independent-samples t-tests and Pearson correlation analyses were performed to examine associations among the parameters.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003e(1) CHS characteristics: X-CHS (target-direction velocity component): During 20%\u0026ndash;40% of the swing cycle, national-level athletes demonstrated significantly lower values than national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.562, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.462); Y-CHS (anterior-posterior velocity component): During 80%\u0026ndash;90% of the swing cycle, national-level athletes showed significantly higher values than national second-level athletes (t\u0026thinsp;=\u0026thinsp;1.625, d\u0026thinsp;=\u0026thinsp;0.321); Z-CHS (vertical velocity component): During 20%\u0026ndash;40% of the swing cycle, national-level athletes exhibited significantly higher values than national second-level athletes (t\u0026thinsp;=\u0026thinsp;4.819, d\u0026thinsp;=\u0026thinsp;1.621). (2) Head posture characteristics: Throughout the 0%\u0026ndash;100% swing cycle, national-level athletes maintained a significantly greater head forward lean angle than national second-level athletes (t\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.887, d\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.916). (3) COM characteristics: Throughout the entire swing cycle, national-level athletes demonstrated significantly greater mediolateral (ML) COM displacement than national second-level athletes (t\u0026thinsp;=\u0026thinsp;3.942, d\u0026thinsp;=\u0026thinsp;1.134, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). (4) Correlation analysis: For national-level athletes, head forward lean showed a positive correlation with X-CHS during 78%\u0026ndash;85% of the swing cycle (r\u0026thinsp;=\u0026thinsp;0.689, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). National second-level athletes exhibited multiphase fluctuations in correlations between head posture and CHS. During 46%\u0026ndash;63% of the swing cycle, national-level athletes' AP-COM (anterior-posterior direction) demonstrated a negative correlation with X-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.635, p\u0026thinsp;=\u0026thinsp;0.008). During 0%\u0026ndash;60% of the swing cycle, national second-level athletes' vertical-COM axis showed a significant negative correlation with Z-CHS (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.661, p\u0026thinsp;=\u0026thinsp;0.005). During 8%\u0026ndash;62% of the swing cycle, national-level athletes' AP-COM exhibited a significant negative correlation with head lateral displacement (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.533, p\u0026thinsp;=\u0026thinsp;0.01); national second-level athletes showed positive correlations between triaxial COM and head displacement throughout the entire cycle (0%\u0026ndash;100%) (r\u0026thinsp;=\u0026thinsp;0.982, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eNational-level athletes achieved efficient energy transfer through head stability control and head-center of mass (COM) coordination, whereas national second-level athletes exhibited fluctuating head posture control characteristics. National-level athletes attained higher clubhead speed by precisely controlling the head forward lean angle, moderately increasing lateral displacement, and establishing antagonistic coordination with the COM, thereby achieving dynamic stability of the rotation axis and efficient energy transfer. National second-level athletes demonstrated insufficient head stability, and their movement pattern of complete synchronization between the COM and head limited the separation effect of the kinetic chain.\u003c/p\u003e","manuscriptTitle":"Effects of Head Kinematics and COM on CHS of 5-Iron Among Male Golfers of Varied Skill Levels","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-30 09:12:01","doi":"10.21203/rs.3.rs-8213762/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-01-06T14:37:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"158503999112320452923665498324520229562","date":"2025-12-30T07:22:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-23T11:44:39+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-02T06:41:57+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-01T01:24:52+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-01T01:23:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2025-11-26T13:54:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3acfe463-6976-4a4e-8d40-e5210f162188","owner":[],"postedDate":"December 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-30T09:12:01+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-30 09:12:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8213762","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8213762","identity":"rs-8213762","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}