Effects Of Recovery Methods On Motor Unit Recruitment And Blood Lactate Levels Following Fatigue

PURPOSE: To examine the effects of recovery methods on motor unit recruitment of the vastus medialis and blood lactate levels following fatigue. METHODS: Eight physically active individuals (23.6 + 3.5 yrs) reported to the lab on four separate occasions to first complete an incremental cycling protocol to volitional fatigue. The highest power output obtained was recorded as peak power output (PPO). During the three remaining sessions, participants completed a cycling protocol alternating between 125% of their PPO for 30 seconds and 50 Watts for 10 seconds until fatigue, followed by one of three recovery protocols: cold water immersion (CWI), pneumatic compression (PC), and foam rolling (FOAM). Electromyography (EMG) data was recorded from the vastus medialis (VM) during maximal voluntary isometric contractions (MVICs) and analyzed for root mean square (RMS) before fatigue (BASE), post-fatigue (PF), post-recovery (PREC), and 24 hours post (24H). Blood lactate (BLa) was collected at the same timepoints. Data was analyzed using repeated measure ANOVA. RESULTS: A recovery x time interaction (p = 0.03) was observed for RMS of the VM. A main effect of time was observed for FOAM (p < 0.001), with significantly greater RMS at PF (0.35 + 0.02; p < 0.001) and PREC (0.36 + 0.02; p < 0.001) compared to BASE (0.22 + 0.01). No significant difference was observed between PF and PREC (p > 0.05) or PF and 24H (0.32 + 0.01; p > 0.05). A main effect of time was also observed for PC (p < 0.001) with significantly greater RMS at PF (0.41 + 0.02) compared to BASE (0.22 + 0.01; p < 0.001). RMS was significantly lower at PREC (0.23 + 0.01; p < 0.001) and 24H (0.21 + 0.02; p < 0.001) compared to PF. A main effect of time was also observed for CWI (p < 0.01) with significantly greater RMS at PF (0.41 + 0.01; p < 0.001) and PREC (0.40 + 0.02; p = 0.012) compared to BASE (0.21 + 0.02). RMS was significantly lower at 24H (0.21 + 0.02; p < 0.001) compared to PF. There was a main effect of recovery (p = 0.006) with significantly lower BLa following PC (4.0 + 0.18) and CWI (3.9 + 0.23) compared to FOAM (7.78 + 0.44). No significant differences were observed between PC and CWI (p = 0.71). CONCLUSIONS: Data suggests that PC and CWI may result in lowered BLa following fatigue compared to FOAM. Additionally, PC appears to have the greatest impact on motor unit recruitment and recovery.