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

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.