Strength Training Leading to Failure Induces Insulin-like Growth Factor-I Reduction and IGFBP-3 Elevation

Abstract

Dramatic changes in volume and intensity of the training stimulus can overstress the nervous and endocrine systems leading to an elevated catabolic and/or lowered anabolic state. It can be hypothesized that a training approach where each repetition was not performed to failure would result in minor changes in resting anabolic/ catabolic hormones. PURPOSE: To examine the efficacy of 11 weeks of resistance training to failure vs. non-failure, followed by an identical 5- week peaking period of maximal strength and power training for both groups as well as to examine the underlying physiological changes in basal circulating anabolic/catabolic hormones. METHODS: Forty-two physic ally-active men were matched and then randomly assigned to either a training to failure (RF; n=14), non-failure (NRF; n=15) or control groups (C; n=13). Muscular and power testing and blood draws to determine basal hormonal concentrations were conducted before the initiation of training (T0), after 6 wk of training (T1), after 11 wk of training (T2), and after 16 wk of training (T3). Subjects undertook a 16-wk (mesocycle) periodized resistance training program divided into three microcycles of 5–6 wk. One group performed high-fatigue strength training exercise to failure (3sets of 10RM and 3sets of 6RM), whereas the other performed the same volume and intensity but did not complete sets to failure (6 sets of 5 reps at 10RM and 6 sets of 3 reps at 6RM), from T0 to T1 and T1 to T2, respectively. During the peaking phase (from T2 to T3), both groups trained at 75%–80% of 1RM (∼5RM), 3 sets of 2–4 repetitions and performed a ballistic training program (i.e. Vertical jumps, sprint runs and various throwing exercises). RESULTS: Both RF and NRF resulted in similar gains in 1RM bench press (23% and 23% and) and half squat (22% and 23%), and muscle power output of the arm (27% and 28%) and leg extensor muscles (26% and 29%). The peaking phase (T2 to T3) followed after NRF resulted in larger gains in muscle power output of the lower extremities. Strength training leading to RF resulted in reductions in resting concentrations of IGF-1 and elevations in IGFBP-3, whereas NRF resulted in reduced resting cortisol concentrations and an elevation in resting serum total testosterone concentration. CONCLUSIONS This investigation demonstrated a potential beneficial stimulus of NRF for improving strength and power, especially during the subsequent peaking training period. Elevation in IGFBP-3 following resistance training may have been compensatory to accommodate the reduction in IGF-1 in order to preserve IGF availability.