The acute effects of unilateral ankle plantar flexors static-stretching on postural sway and gastrocnemius muscle activity during single-leg balance tasks

The aim of this study was to investigate the acute effects of unilateral ankle plantar flexors static-stretching on surface electromyography (semg) and the center of pressure (cop) during a single-leg balance task in both lower limbs. fourteen young healthy,non-athletic individuals performed unipodal quiet standing for 30s before and after (stretched limb: immediately post-stretch,10 and 20 minutes and non-stretched limb: immediately post-stretch) a unilateral ankle plantar flexor staticstretching protocol [6 sets of 45s/15s,70-90% point of discomfort (pod)]. postural sway was described using the cop area,cop speed (antero-posterior and medio-lateral directions) and cop frequency (antero-posterior and medio-lateral directions). surface emg (emg integral [iemg] and median frequency[ fm]) was used to describe the muscular activity of gastrocnemius lateralis. ankle dorsiflexion passive range of motion increased in the stretched limb before and after the static-stretching protocol (mean ± sd: 15.0° ± 6.0 and 21.5° ± 7.0 [p < 0.001]). cop area and iemg increased in the stretch limb between pre-stretching and immediately post-stretching (p = 0.015 and p = 0.036,respectively). in conclusion,our staticstretching protocol effectively increased passive ankle rom. the increased rom appears to increase postural sway and muscle activity; however these finding were only a temporary or transient effect. © journal of sports science and medicine.