Effect of Resistance Exercise on Indices of Fatigue

Abstract

The ergogenic effects of carbohydrate ingestion on aerobic exercise have been well established; however, the literature is mixed regarding resistance training. PURPOSE: To determine the ergogenic effects of carbohydrate ingestion on isometric leg exercise, plasma glucose (PG) responses, plasma free fatty acid (FFA), plasma glycerol, and blood lactate responses (La) during a selected resistance protocol. METHODS: Six male subjects with a minimum of three years of bodybuilding and/or power lifting experience performed one mock trial and two randomly assigned exercise trials in which either a glucose polymer (GP) solution (0.17g·kg-1 body mass) or placebo (P) was administered in a double-blind fashion. Participants performed single-leg isometric contractions at 50% of one repetition maximum (1RM) for 20 seconds (s), followed by 40 s of rest between contractions, until failure occurred. Failure was defined as the inability to sustain target force for 5 consecutive seconds. The decrease in force generating capacity was tested from brief maximal voluntary contractions and short bursts of 60 Hz stimulation applied at 5 min intervals. Slope of fatigue was measured using a strain gauge type load cell, which sent an amplified signal to a desktop computer for interpretation. Plasma glucose, FFA, glycerol, and La were measured prior to testing, midway through the protocol, immediately post-exercise, and at five min post-exercise. RESULTS: A statistical evaluation of temporal changes linear regression analysis revealed a more linear slope in the GP than P trial (GP = -0.0594 ± -0.0299 and P = -0.0300 ± -0.0109). This result was significant (p =.028). A 2 × 4 ANOVA with repeated measures revealed PG and La were significantly elevated in the GP protocol. No significant differences were observed between the treatments for FFA and glycerol concentrations. Finally, a Pearson's correlation revealed a significant relationship between force production and blood lactate (r = -0.689, p <.05). CONCLUSIONS: The results suggest that the ingestion of a liquid carbohydrate supplement prior to and intermittently throughout single-leg isometric lower body resistance training protocols appears to elevate blood glucose levels and provide an ergogenic effect that is reflected by a more linear slope of fatigue.