Localized Ankle Fatigue Development and Fatigue Perception in Adults With or Without Chronic Ankle Instability

Fatigue could contribute to ankle-sprain injuries during sport, particularly for individuals with chronic ankle instability (CAI).

To examine whether adults with or without CAI develop fatigue at similar rates when performing ankle exercises at the same relative effort level and whether these groups differ in their subjective perceptions of fatigue.

Controlled laboratory study.

Biomechanics research laboratory.

A total of 11 volunteers with CAI (1 man, 10 women; age = 23.5 ± 3.0 years, height = 168.0 ± 11.2 cm, mass = 64.3 ± 13.5 kg) were recruited for the unstable-ankle group, and 11 volunteers matched for age, height, mass, and sex (1 man, 10 women; age = 24.1 ± 2.1 years, height = 169.5 ± 9.7 cm, mass = 62.3 ± 9.7 kg) were recruited as control participants.

Localized muscle fatigue (LMF) was induced in the ankle of the dominant limb using a custom fatigue protocol. Plantar-flexion and dorsiflexion exertions were completed at a rate of 12 cycles per minute at isotonic loads equal to 70% and 30%, respectively, of individual maximal voluntary isometric strength. Intermittent measures of maximal voluntary isometric strength and ratings of perceived exertion (RPEs) were obtained.

We compared isometric-strength measures and RPE scores at each observation time (prefatigue and at 4, 8, 12, and 16 minutes into the fatigue protocol) and the group correlations between changes in strength and changes in RPE scores.

Based on ankle-strength measures, the 2 test groups developed LMF at similar rates when exercising at equivalent levels of relative effort. The 2 groups also reported similar levels of discomfort as fatigue progressed.

The rate of LMF development at the ankle and the associated perception of fatigue did not differ between adults with or without CAI.