Effects Of Recovery Methods On Motor Unit Recruitment Of The Vastus Lateralis Following Fatigue

PURPOSE: To examine the effects of recovery methods on motor unit recruitment of the vastus lateralis following fatigue. METHODS: Eight physically active individuals (23.6 + 3.5 yrs) reported to the lab to first complete an incremental cycling protocol to volitional fatigue, with the highest power output achieved recorded as peak power output (PPO). Participants then returned to the lab for three more sessions, during which they completed a cycling protocol alternating between 125% of their PPO for 30 seconds and 50 Watts for 10 seconds until volitional fatigue, followed by one of three recovery protocols: cold water immersion (CWI), pneumatic compression boots (PC), and foam rolling (FOAM). EMG data was recorded from the vastus lateralis (VL) during maximal voluntary isometric contractions (MVICs) and analyzed for root mean square (RMS) before fatigue (BASE), immediately following fatigue (PF), immediately following each recovery protocol (PREC), and 24 hours post fatigue (24H). Data was analyzed using repeated measures ANOVA. RESULTS: A recovery x time interaction (F = 3.821, p = 0.006) was observed for RMS of the VL. A main effect of time was observed for FOAM (p < 0.001), with significantly greater RMS at PF (0.362 + 0.024; p < 0.001), PREC ( 0.358 + 0.026; p < 0.001), and 24H (0.343 + 0.027; p < 0.001) compared to BASE (0.227 + 0.024). No significant difference was observed between PF and PREC (p > 0.05). A main effect of time was also observed for PC (F = 15.831, p < 0.001) with significantly greater RMS at PF (0.417 + 0.026) compared to BASE (0.23 + 0.027; p < 0.001). RMS was significantly lower at PREC (0.222 + 0.027; p < 0.001) and 24H (0.218 + 0.022; p < 0.001) compared to PF (0.417 + 0.026). No significant differences were observed between BASE and PREC (p = 0.267) or BASE (p = 0.181) and 24H. A main effect of time was also observed for CWI (F = 101.026, p < 0.001) with significantly greater RMS at PF (0.444 + 0.024) compared to BASE (0.227 + 0.024; p < 0.001). RMS was significantly lower at PREC (0.219 + 0.02; p < 0.001) and 24H (0.21 + 0.025; p < 0.001) compared to PF (0.444 + 0.022). No significant differences were observed between BASE and PREC (p = 0.314). CONCLUSIONS: Data suggest that PC and CWI result in greater improvements following fatigue compared to FOAM, indicated by reduced motor unit recruitment after recovery.