An examination of the correlation between antagonist coactivation of the abdomen and rotational kinematics in skilled golfers

The objective was to examine how phase-specific abdominal antagonist co-activation (CoA) influences trunk rotational kinematics in skilled golfers. Thirty male amateurs (19.7 ± 0.7 years; handicap 9.6 ± 2.4) performed 6 iron swings with synchronised motion capture and surface electromyography of the external obliques (EO). Pearson correlations and linear regression were applied. CoA showed distinct phase-dependent effects. During take-away, higher CoA correlated with greater peak pelvic velocity (<i>r</i> = 0.460; <i>r²</i> = 0.21), indicating stabilising function. Early downswing CoA was negatively associated with X-factor at impact (<i>r</i> = -0.516; <i>r²</i> = 0.26) and peak pelvic velocity (<i>r</i> = -0.540; <i>r²</i> = 0.29), suggesting that reduced CoA facilitates proximal acceleration and elastic energy transfer. During downswing acceleration, CoA positively predicted peak thoracic velocity (<i>r</i> = 0.397; <i>r²</i> = 0.15) and thoracic deceleration (<i>r</i> = 0.450; <i>r²</i> = 0.20), reflecting a dual role in energy transfer and active braking. Early follow-through CoA was positively associated with thoracic deceleration (<i>r</i> = 0.440; <i>r²</i> = 0.19), supporting post-impact trunk control. These findings suggest that skilled golfers modulate EO CoA across swing phases to balance stability, energy transfer and controlled segmental deceleration, highlighting the functional significance of abdominal CoA for swing performance and injury prevention.