Upper body muscle activation during acceleration and sprinting

The purpose of this study was to measure EMG activity of the upper body and its relationship with sprint performance variables during a 40-m sprint. Fourteen adults (eight females, six males) completed three sprints, with mean activation for the deltoid, trapezius, biceps, triceps, latissimus dorsi, erector spinae, external oblique and rectus abdominus measured for each 10 m phase of the sprints, along with velocity, acceleration, net horizontal force (F_H) and the ratio of F_H to net sagittal ground reaction force (RF%). Overall, activation of the deltoid, trapezius, biceps and triceps declined during the later phases of the spint, while latissimus dorsi, erector spinae and external oblique activation increased after 0-10 m. From 10 to 20 m, activation of the latissimus dorsi and erector spinae were positively correlated with velocity, acceleration, F_H and RF% (p-values 0.003-0.04). Erector spinae activity was also positively correlated with velocity (p = 0.01) and acceleration (p = 0.03) from 20 to 30 m. It seems that activation of the shoulder and arm musculature declines as runners near peak velocity, while trunk musculature activation increases. Erector spinae and latissimus dorsi activity may also be critical during the transition from peak acceleration to peak velocity while sprinting.