Effect of fatigue on neuromuscular function at the ankle.

CONTEXT: Lateral ankle sprains occur more frequently than any other orthopedic injury. Athletes often report sustaining more injuries late in competition when fatigue is present.

OBJECTIVE

To evaluate neuromuscular function of the ankle musculature after fatigue.

DESIGN

Experimental, pretest-posttest.

SETTING

Research laboratory.

PARTICIPANTS

Ten female and 9 male college-aged subjects.

INTERVENTION: Fatigue was induced via continuous concentric and eccentric muscle actions of the ankle: inversion (INV), eversion (EV), plantar flexion (PF), and dorsiflexion (DF).

MAIN OUTCOME MEASURES: Peak torque (PT), peak EMG, and median frequency (MF) were calculated prefatigue and postfatigue in the tibialis anterior (TA), peroneus longus (PER), and lateral gastrocnemius (GAS) muscles.

RESULTS

Main effects were noted for test (P < 0.0125) in all statistical tests performed indicating changes in PT, peak EMG, and MF after fatigue.

CONCLUSIONS

A significant decrease in MF of the PER muscle after PF fatigue and corresponding with a decreased firing rate, may be of importance, especially with regard to the role in countering the violent moment seen with inversion ankle sprains.