The Acute Effects of Antagonist Static Stretching on Agonist Performance.

Stretching the antagonist muscle to enhance agonist performance has gained considerable attention. However, most studies have focused on one stretching duration. Hence, the aim of this study was to compare varying durations (40-, 80-, and 120-seconds) of antagonist (dorsiflexors) static stretching (SS) on agonist (plantar flexors: PF) muscle performance. In this randomized crossover study, 16 participants (six females) underwent four sessions (40-, 80-, 120-s dorsiflexors SS and control), with pre- and post-intervention measurements of slow (60⁰/s) and fast (240⁰/s) PF isokinetic, isometric peak torque, total work, stiff leg drop jump (SDJ) performance (height, reactive strength index (RSI) and peak power), and tibialis anterior and soleus electromyography (EMG). Dorsiflexors SS protocol involved 1x40-s (40-s), 2x40-s (80-s), and 3x40-s (120-s). There were no significant pre- to post-intervention changes in any parameter. A main effect for time demonstrated an overall decrease in fast (p < 0.0001, 5.9%, d = 0.24) and slow (p = 0.05, 6.6%, d = 0.24) isokinetic peak torque, total work (p = 0.02, 5.1%, d = 0.20) and all SDJ measures (SDJ height: p = 0.02, 2.7%, d = 0.15, RSI: p < 0.0001, 5.9%, d = 0.23, peak power: p = 0.002, 4.4%, d = 0.22). Soleus EMG decreased from pre- to post-SS after 120-s in both isometric (p = 0.002, 13.6%, d = 0.73) and slow isokinetic (p = 0.002, 12.3%, d = 0.91) peak torque as well as 80-s with slow isokinetic peak torque (p = 0.02, 6.6%, d = 0.75). In summary, different durations of dorsiflexors SS (40-s, 80-s, 120-s) did not significantly influence PF performance. However, deficits associated with a main effect for time suggested possible testing effects as detected with the control condition.