Exercise training with blood flow restriction has little effect on muscular strength and does not change IGF-1 in fit military warfighters

Abstract

Objective: Aerobic exercise with blood flow restriction (aBFR) has been proposed as an adjunctive modality in numerous populations, potentially via an enhanced growth factor response. However, the effects of aBFR on highly trained warfighters have yet to be examined. The purpose of this study was to determine if adjunctive aBFR as part of a regular physical training regimen would increase markers of aerobic fitness and muscle strength in elite warfighters. In addition, we sought to determine whether the changes in blood lactate concentration induced by aBFR would be associated with alterations in the insulin-like growth factor (IGF) axis.

Design: Active-duty US Naval Special Warfare Operators (n=18, age=36.8 ± 2.2 years, weight=89.1 ± 1.2 kg, height=181.5 ± 1.4 cm) from Naval Amphibious Base Coronado were recruited to participate in 20 days of adjunctive aBFR training. Peak oxygen consumption (VO2 peak), ventilatory threshold (VT), and 1-repetition max (1-RM) bench press and squat were assessed pre- and post-aBFR training. Blood lactate and plasma IGF-1 and IGF-binding protein-3 (IGFBP-3) were assessed pre-, 2 min post-, and 30 min post-aBFR on days 1, 9, and 20 of aBFR training.

Results: Following aBFR training there were no changes in VO2 peak or VT, but there was an increase in the 1-RM for the bench press and the squat (5.0 and 3.9%, respectively, P<0.05). Blood lactate concentration at the 2-min post-exercise time point was 4.5-7.2-fold higher than pre-exercise levels on all days (P<0.001). At the 30-min post-exercise time point, blood lactate was still 1.6-2.6-fold higher than pre-exercise levels (P<0.001), but had decreased by 49-56% from the 2-min post-exercise time point (P<0.001). Plasma IGF-1 concentrations did not change over the course of the study. On day 9, plasma IGFBP-3 concentration was 4-22% lower than on day 1 (P<0.01) and 22% lower on day 9 than on day 20 at the 30-min post-exercise time point (P<0.001).

Conclusions: Our data suggest that aBFR training does not lead to practical strength adaptations or alterations in the IGF axis in a population of highly trained warfighters.

Keywords: Blood flow restriction; Exercise; IGF axis; Insulin-like growth factor-1; Warfighters.