Changes in human skeletal muscle contractility and hormone status during 2weeks of heavy strength training

To examine neuromuscular and hormone changes during 2 weeks of heavy streng th training, Is weight-trained male students were recruited either into a h eavy training group (HT, n = 11) or into a control group (Ctr, n = 7). The heavy training protocol consisted of leg-extensor workouts performed daily, while workouts were performed twice a week in the Ctr group. A test of one repetition maximum (1 RM) was performed before heavy training and on the 2 nd day after heavy training. Isokinetic knee extensions, electrical stimula tion, and squat jumps were performed before, on the 8th day of heavy traini ng, and on the 4th day after heavy training. Morning blood samples (0800 ho urs) were drawn before, on the gth day of heavy training, and on the 4th da y after heavy training. Before, and on the 5th day after heavy training, 24 h urine samples were collected. The I RIM leg press increased by 6 (SEM 2) % in the HT group. Testosterone and insulin-like growth factor-1 concentrat ions were respectively 12 (SEM 5)% and 11(SEM 3)% lower than baseline on th e 8th day of heavy training; however, hormone levels were back to baseline on the 4th day after heavy training. A significant correlation between indi vidual changes in 1 RM leg press and changes in testosterone concentrations was observed in the HT group (r = 0.69). In the HT group, 24 h urinary cat echolamine excretion increased by 26 (SEM 12)%, 3-methylhistidine excretion increased by 21 (SEM 6)% and creatinine excretion increased by II (SEM 5)% . There were no significant changes in the Ctr group. This work addresses t he role of changes in basal hormone status (morning samples) for skeletal m uscle adaptation to heavy strength training.