Effects of Short-Term Strength Training on Maximal Velocity Parameters and Rate of Muscle Activation

Abstract

It has been suggested that training-related increases in maximal velocity parameters (MVPs) may be mediated through neural mechanisms, however; little evidence exists regarding training induced changes in early-phase muscle activation and MVPs. PURPOSE: To examine the effects of short-term strength training (ST) on MVPs and rate of muscle activation. METHODS: Twenty males who had not performed ST within the past 6 months participated in this study. A training group (TG; n = 13, age = 22 ± 1.9 yrs.) performed 3 sessions per week of unilateral isokinetic ST of the dominant leg for 4 weeks. A control group (CG; n = 7, age = 23 ± 4.3 yrs.) only participated in the testing sessions. ST sessions consisted of maximal concentric contractions of the knee extensors at 45°·s-1 for 4 sets of 10 repetitions. Subjects were instructed to “kick out as hard and fast as possible” during each ST session. Maximal concentric isokinetic testing of the knee extensors at 500°s-1 (IsoK500) was performed before (pre), at week 2 (mid), and after week 4 (post) of ST . There was no resistance during IsoK500, with the exception of lever arm mass, as this velocity was above all subjects’ maximum velocity. The highest velocity attained (PV) and the linear slope of the velocity-time curve from the onset of contraction to PV (RVD) were recorded for each IsoK500. Surface electromyography (EMG) of the vastus lateralis was recorded in order to obtain the linear slope of the rectified EMG-time curve for a 100 ms period after the onset of contraction (RER). The contraction producing the highest PV was used for subsequent analysis of all dependent variables (DVs). Non-parametric statistics were used to make baseline comparisons between the TG and CG as well as comparisons across time in the CG. A one-way repeated measures ANOVA was used to examine changes across time in the TG. RESULTS: There were no baseline differences between the TG and CG for any of the DVs (p = 0.191-0.405). There were no changes in any of the DVs across time in the CG (p > 0.05). PV (p = 0.448), RVD ( p = 0.378), and RER ( p = 0.168) remained unchanged across time in the TG. CONCLUSION: The results revealed that low-velocity ST performed with a ballistic intent had no effect on RVD, PV, or RER. Although it is unclear, this may be due to the low-velocity used for training and the possibility of velocity-specific adaptations.