Neuromuscular Electrical Stimulation And Heat Therapy Modalities On Recovery After Exercise-Induced Muscle Fatigue

Exercise induced fatigue is associated with a build-up of metabolites and tissue inflammation in the muscle. Increasing blood flow to the exercised area to allow for metabolite removal and prevention of fatigue may allow an individual to return to exercise sooner. Modes that have been used to increase blood flow post-exercise to damaged muscles include neuromuscular electrical stimulation (NMES) and heat therapy (HT). PURPOSE: We aimed to evaluate the effectiveness of NMES and HT as recovery modalities after inducing fatigue with maximal exercise in active individuals. METHODS: A randomized controlled study design with four groups: control, NMES, HT, NMES+HT was used to achieve the study aim. Thirty-two participants performed maximal exercise pre-intervention and then rested (control) or received HT, NMES, NMES+HT for 15 min before performing another bout of maximal exercise. The maximal exercise was performed on a force plate and consisted of a 30-sec maximal isometric contraction in the high hang pull position with a clean grip and a fixed knee angle of 45 degrees, using lifting straps to prevent hand movement and handgrip fatigue. Outcomes included vertical (Fz) force output and ratings of perceived exertion (RPE) immediately after exercise. A two-way mixed ANOVA was used to determine whether outcomes were different pre-to-post and across recovery modalities. RESULTS: There was no significant time by intervention effect (p > 0.05), indicating vertical (Fz) force output pre-post was not different between the groups. No significant main effects for time or intervention were observed (p > 0.05 for both). Pre-intervention vertical (Fz) force output was: 2015.47 ± 598.92 N for the control group; 2360.51 ± 822.28 N for HT; 2287.62 ± 816.44 N for NMES; and 2193.03 ± 628.22 N for NMES+HT. Post-intervention vertical (Fz) force output was: 1895.64 N ± 716.24 for the control group; 2314.53 N ± 839.65 N for HT; 2348.93 ± 756.83 N for NMES; and 2214.15 ± 836.13 N for NMES+HT. CONCLUSIONS: No significant main effects for time or intervention were observed (p > 0.05 for both). The limited sample size and high variability in ground reaction force may have contributed to the absence of statistically significant interactions. However, mean values indicate positive trends in the use of HT and NMES as recovery modalities compared to a control.