Muscle weakness, including low maximal & explosive strength, contribute to the functional limitations experienced by numerous patient groups, including osteoarthritis patients. Strength training can improve function in different populations. However, adaptations to different types of strength training are not well understood which limits the efficacy of training prescription. Explosive training (ET), involving rapid torque development with short duration contractions, provides a less fatiguing loading modality that may be preferably tolerated by patient groups.
PURPOSE: The purpose of this study was to compare the functional, neural, & morphological adaptations to ET vs. conventional training (CT).
METHODS: Healthy males completed ET (n=13) or CT (n=16) for 12-wks. Training involved 4 x 10 repetitions (x3/wk): contracting as fast & hard as possible for ~1 s (ET); or gradually increasing to 75% maximal voluntary torque (MVT) before holding for 3 s (CT). Torque & EMG during maximal (MVT & QEMGMVT) & explosive (T100 & EMG0-100) contractions, & total Quadriceps volume (QUADSVOL) were measured pre & post. Absolute changes were considered different between groups when: post hoc P-values were < 0.1 & effect size (ES) was > 0.5.
RESULTS: MVT improved after both types of training (CT: +56 ± 23 Nm; ET: +40 ± 22 Nm), but increased more following CT (P=0.052; ES=0.69). There were similar EMGMVT changes after CT (+0.06 ± 0.03 mV) & ET (+0.04 ± 0.08 mV; P=0.449; ES=0.36), but QUADSVOL increases after CT (+148 ± 135 cm3) were greater than ET (+46 ± 137 cm3; P=0.074; ES=0.74). Improvements in T100 were greater after ET (+23 ± 25 Nm) vs CT (+7 ± 18 Nm; P=0.092; ES=0.72). Changes in EMG0-100 were greater with ET (+0.03 ± 0.04 mV) than CT (+0.01 ± 0.04 mV), but did not reach significance (P=0.253; ES=0.46).
CONCLUSIONS: These results provide evidence for distinct neural & morphological adaptations specific to the training stimulus. However, given the lower contraction durations, fatigue & effort involved in ET, this type of training appears to provide an efficient means of increasing maximal & explosive function in previously untrained individuals.