Early phase interference between low-intensity running and power training in moderately trained females.

Abstract

The aim of the study was to investigate the effects of low-intensity running performed immediately after lower-body power-training sessions on power development. Twenty young females participated in 6weeks, 3/week, of either lower body power training (PT) or lower body power training followed by 30min of low-intensity running (PET) eliciting 60-70% of maximal heart rate. The following were measured before and after the training period: counter-movement jump, isometric leg press force and rate of force development (RFD), half squat 1-RM, vastus lateralis fiber type composition and cross sectional area, resting intramuscular fiber conduction velocity (MFCV), and heart rate during the modified Bruce treadmill test. Counter-movement jump height and peak power increased after PT (10.7±6.2 and 12.9±18.7%, p<0.05) but not after PET (3.4±7.6 and 5.11±10.94%, p>0.05). Maximum isometric force, RFD, and half squat 1-RM increased similarly in both groups. Muscle fiber type composition was not altered in either group. Muscle fiber cross sectional area increased only after PT (17.5±17.4, 14.5±10.4, 20.36±11.3%, in type I, IIA, and IIX fibers, respectively, p<0.05). Likewise, mean MFCV increased with PT only (before: 4.53±0.38ms(-1), after: 5.09±0.39ms(-1), p=0.027). Submaximal heart rate during the Bruce treadmill test remained unchanged after PT but decreased after PET. These results suggest that low-intensity running performed after lower-body power training impairs the exercise-induced adaptation in stretch-shortening cycle jumping performance (vertical jump height, peak power), during the first 6weeks of training, which may be partially linked to inhibited muscle fiber hypertrophy and muscle fiber conduction velocity.