The Influence Of Eccentric Muscle Loading On Cycle Performance In A Glycogen-reduced State.

Abstract

Sustained eccentric muscle action is commonly associated with development of impaired muscle function, development of muscle soreness, and impaired glucose uptake by the damaged fibers. PURPOSE: This study was designed to assess the influence of eccentric muscle loading on CHO oxidation and on time to fatigue performance. METHODS: Seven moderately to well-trained volunteers (six male, 1 female) completed a cycle VO2peak test and three experimental trials, each trial separated by one week. Each experimental trial consisted of a glycogen-lowering phase (via cycling) and a 10-min treadmill run. Upon completion of the run subjects were provided a beverage containing either 60 g CHO (maltodextrin) or a placebo. The conditions were: 1) flat run followed by CHO (F-CHO); 2) flat run followed by placebo (F-PL); 3) downhill run (−10% grade) followed by CHO (DH-CHO). Two hours later, subjects completed a performance ride to volitional fatigue at 75% Wmax. Subjects were blinded to beverage type and to elapsed time during the performance ride. RESULTS: CHO oxidation rate (F-CHO: 3.5±0.3 g/min; F-PL:3.2±0.3 g/min; DHCHO: 3.4±0.3 g/min), VO2 (F-CHO: 3.18±0.3 l/min; F-PL: 3.19±0.3 l/min; DH-CHO: 3.13±0.2 l/min), HR, RPE and performance times (F-CHO: 30.1±3.1 min; F-PL: 28.5±2.7 min; DH-CHO: 27.8±1.8 min) were not different by condition (p>0.05). CONCLUSIONS: Based on the results of this study, a short DH run had no effect on CHO delivery and use or on time to fatigue when cycling in a glycogen-reduced state. It is possible that the DH run provided insufficient eccentric loading to impair CHO uptake by the fiber or that such an effect would be more likely to manifest during the presentation of DOMS symptoms.