Muscle Activation During Landing Before and After Fatigue in Individuals With or Without Chronic Ankle Instability.

Context: Ankle instability is a common condition in physically active individuals. It often occurs during a jump landing or lateral motion, particularly when participants are fatigued.

Objective: To compare muscle activation during a lateral hop prefatigue and postfatigue in individuals with or without chronic ankle instability (CAI).

Design: Cross-sectional study.

Setting: Sports medicine research laboratory.

Patients Or Other Participants: A total of 32 physically active participants volunteered for the study. Sixteen participants with CAI (8 men, 8 women; age = 20.50 ± 2.00 years, height = 172.25 ± 10.87 cm, mass = 69.13 ± 13.31 kg) were matched with 16 control participants without CAI (8 men, 8 women; age = 22.00 ± 3.30 years, height = 170.50 ± 9.94 cm, mass = 69.63 ± 14.82 kg) by age, height, mass, sex, and affected side.

Intervention(s): Electromyography of the tibialis anterior, peroneus longus, gluteus medius, and gluteus maximus was measured before and after a functional fatigue protocol.

Main Outcome Measure(s): Activation of 4 lower extremity muscles was measured 200 milliseconds before and after landing from a lateral hop.

Results: We observed no interactions. The group main effects for the peroneus longus demonstrated higher muscle activation in the CAI group (52.89% ± 11.36%) than in the control group (41.12% ± 11.36%) just before landing the lateral hop (F = 8.58, P = .01), with a strong effect size (d = 1.01). The gluteus maximus also demonstrated higher muscle activation in the CAI group (45.55% ± 12.08%) than in the control group (36.81% ± 12.08%) just before landing the lateral hop (F = 4.19, P = .049), with a moderate effect size (d = 0.71). We observed a main effect for fatigue for the tibialis anterior, with postfatigue activation higher than prefatigue activation (F = 7.45, P = .01). No differences were present between groups for the gluteus medius.

Conclusions: Our results support the presence of a centralized feed-forward neuromuscular alteration in patients with CAI, not only in the ankle-joint muscles but also in the proximal hip muscles. These results may have implications for rehabilitation programs in these patients.