Neuromuscular fatigue and physiological responses after five dynamic squat exercise protocols.

The present study aimed to analyze neuromuscular, physiological and perceptual responses to a single bout of five different dynamic squat exercise protocols. In a randomized and counterbalanced order, fifteen male resistance-trained athletes (mean±SD; age: 23.1±1.9 years, body mass: 77.4±8.0 kg) completed a traditional multiple sets (MS: 4 x 6, 85% 1RM), drop sets (DS: 1 x 6, 85% 1RM + 3 drop sets), eccentric overload (EO: 4 x 6, 70% 1RM concentric, 100% 1RM eccentric), flywheel YoYo Squat (FW: 4 x 6, all-out), and a plyometric jump protocol (PJ: 4 x 15, all-out). Blood lactate (La), ratings of perceived exertion (RPE), counter movement jump height (CMJ), multiple rebound jump performance (MRJ), maximal voluntary isometric contraction force (MVIC), serum creatine kinase (CK) and delayed onset muscle soreness (DOMS) were measured. Immediately post-exercise, La was significantly (p<0.001) higher in FW (mean±95% CL; 12.2±0.9 mmol·L) and lower in PJ (3.0±0.8 mmol·L) compared to MS (7.7±1.5 mmol·L), DS (8.5±0.6 mmol·L) and EO (8.2±1.6 mmol L), accompanied by similar RPE responses. Neuromuscular performance (CMJ, MRJ) significantly remained decreased (p<0.001) from 0.5 to 48 h post-exercise in all protocols. There was a significant time x protocol interaction (p<0.05) in MRJ with a significant lower performance in DS, EO and FW compared to PJ (0.5 h post-exercise), and in EO compared to all other protocols (24 h post-exercise). A significant main time effect with peak values 24 h post-exercise was observed in CK serum concentrations (p<0.001), but there was no time x protocol interaction. In conclusion, (1.) metabolic and perceptual demands were higher in FW and EO compared to MS, DS and PJ, (2.) neuromuscular fatigue was consistent up to 48 h post-exercise in all protocols, and (3.) EO induced the greatest neuromuscular fatigue.