Ankle strength and force sense after a progressive, 6-week strength-training program in people with functional ankle instability

Abstract

Context: Although strength training is commonly used to rehabilitate ankle injuries, studies investigating the effects of strength training on proprioception have shown conflicting results.

Objective: To determine the effects of a 6-week strength-training protocol on force sense and strength development in participants with functional ankle instability.

Design: Randomized controlled clinical trial.

Setting: University athletic training research laboratory.

Patients or other participants: A total of 40 participants with functional ankle instability were recruited. They were randomly placed into a training group (10 men, 10 women: age = 20.9 ± 2.2 years, height = 76.4 ± 16.1 cm, mass = 173.0 ± 7.9 kg) or control group (10 men, 10 women: age = 20.2 ± 2.1 years, height = 78.8 ± 24.5 cm, mass = 173.7 ± 8.2 kg).

Intervention(s): Participants in the training group performed strength exercises with the injured ankle 3 times per week for 6 weeks. The protocol consisted of a combination of rubber exercise bands and the Multiaxial Ankle Exerciser, both clinically accepted strengthening methods for ankle rehabilitation. The progression of this protocol provided increasingly resistive exercise as participants changed either the number of sets or resistance of the Thera-Band or Multiaxial Ankle Exerciser. Main Outcome Measure(s): A load cell was used to measure strength and force sense. Inversion and eversion strength was recorded to the nearest 0.01 N. Force-sense reproduction was measured at 2 loads: 20% and 30% of maximal voluntary isometric contraction.

Results: Increases in inversion (F(1,38) = 11.59, P < 0.01, η(p)(2) = 0.23, power = 0.91) and eversion (F(1,38) = 57.68, P < .01, η(p)(2) = 0.60, power = 0.99) strength were found in the training group at the posttest when compared with the control group. No significant improvements were noted in force-sense reproduction for either group.

Conclusions: Strength training at the ankle increased strength but did not improve force sense.

Figure 1

Participant positioning for maximal voluntary isometric contraction strength testing for the left ankle. A, Eversion strength. B, Inversion strength. Arrow illustrates direction of force application.

Figure 2

Participant positioning in Multiaxial Ankle Exerciser (Multiaxial, Inc, Lincoln, RI) for 6-week strength-training protocol.