Acute neuromuscular responses and recovery after three different resistance exercise loadings in male power and strength athletes

The frequency, volume, intensity and length of rest intervals affect neuromuscular fatigue caused by the resistance exercise. Acute neuromuscular responses and long-term adaptations to different types of resistance exercises have been examined in the previous studies, but they still are not entirely understood. The neuromuscular fatigue has been studied widely in untrained subjects, nevertheless, there is a lack of evidence about neuromuscular responses to resistance exercise in recreational and especially elite level athletes. The purpose of this study was to examine, whether the training background affected the acute neuromuscular responses during resistance exercise loadings or during the recovery of two days. In total 23 men participated in the study. Subjects were divided into three groups by their training background - power athletes (POA, n=8), strength athletes (SA, n=8) and nonathletes (NA, n=7). The subject groups performed power (7x6x50% of 1RM), maximal strength (7x3x90% of 1RM) and hypertrophic (5x10x70% of 1RM) loadings separated by one week. The neuromuscular measurements were performed before, during and immediately after the loading and after 15 minutes, 24 hours and 48 hours of recovery. The measurements included maximal isometric force and average force during the first 500 ms of contraction in the leg press, average power during the half back-squat, countermovement jump height, maximal isometric force of knee extensors, electrical stimulation of QF during the maximal isometric voluntary contraction, sEMG from VL and VM, and blood lactate. It was shown that all resistance exercise loadings led to an acute decrease in neuromuscular performance. For instance, MIVCLP decreased from Pre to Post -7.6 to -13.4% during the power loading, -13.4 to -15.6% during the maximal strength loading and -24.5 to -29.9% during the hypertrophic loading. sEMG measured during in MIVCLP declined from Pre to Post -10.1 to -12.9%, -12.6 to -20.3% and -5.3 to 9.7% respectively. During the power loading, significant differences were observed from Pre to Mid (p=0.044) between POA (-12.5%) and SA (-5.6%) in MIVCLP and from Pre to Mid (p=0.024) between SA (-4.1%) and NA (-11.4%) in CMJheight. The recovery within the groups was similar after all resistance exercise loadings and no significant differences between groups were found during the recovery. In conclusion, this study indicated that the neuromuscular fatigue caused by both the power and maximal strength loadings was mainly of central origins, whereas the hypertrophic loading caused more peripheral neuromuscular fatigue. The significant differences observed between groups during the power loading could suggest that the training background may affect the acute responses after this type of resistance exercise loading. The training background seemed to have a limited effect on the recovery after the present types of resistance exercise loadings