Effects Of Eccentric Training Combined To Neuromuscular Electrical Stimulation On Electromechanical Delay Of Peroneal Muscles In Individuals With Functional Ankle Instability

The electromechanical delay (EMD) represents the time required by the muscles to provide a protective response to an injurious mechanism. Individuals with functional ankle instability (FAI) have showed longer EMD times for the peroneal muscles (EMD-P) than ankles of healthy individuals; which is thought to increase the risk of the recurrence of ankle sprains. However, there's currently no noninvasive treatment to shorten EMD-P. PURPOSE: The aim of this study was to investigate the effects of eccentric training combined with neuromuscular electrical stimulation (NMES) on the EMD time of peroneal muscles during eccentric muscle action in individuals with FAI. METHODS: This was a three-arm, single-blinded, randomized controlled trial. Thirty-nine volunteers (21 ± 3ys) with FAI were randomly assigned to control (CON; n = 13), eccentric training (ECC; n = 13), or eccentric training combined with neuromuscular electrical stimulation groups (ECC+NMES; n = 13). The control group received conventional rehabilitation therapy (CRT), involving strength and balance training. The ECC group performed isokinetic concentric and eccentric training of the peroneal muscles based on CRT. The ECC+NMES group received NMES simultaneous to the isokinetic training. Both groups trained 3 days/week for eight weeks. The EMD-P was calculated when peroneal muscles contracted eccentrically at 90./s using the isokinetic system before and after training. A one-way ANOVA was used to look at the differences in EMD-P between three groups. RESULTS: No significant differences existed for EMD-P among the groups before training (F = 0.295, P > 0.05). Compared with pre-training, the EMD-P was significantly shorter in the ECC group (133 ± 8 vs. 127 ± 8 ms, P < 0.05) and ECC+NMES groups (135 ± 11 vs. 119 ± 9 ms, P < 0.05). However, no change occurred in CON (134 ± 7 vs. 135 ± 10 ms, P > 0.05). The ECC group showed a significant lower EMD-P Compared with CON after training (127 ± 8 vs. 135 ± 10 ms, P = 0.027), whilst EMD-P was shorter after training in ECC+NMES compared with ECC (119 ± 9 vs. 127 ± 8 ms, P = 0.03). CONCLUSION: Eccentric training effectively shortened the EMD-P in individuals with FAI compared with conventional treatment. However, ECC combined with NMES further enhanced the reduction in EMD-P. Therefore, ECC+NMES could be an effective treatment for FAI.