Glucose Ingestion Does Not Improve Maximal Isokinetic Force.

Abstract

The purpose of this study was to assess maximal isokinetic leg extension force in response to glucose ingestion and to determine whether any performance changes occur in a time-dependent manner. Seventeen young (22.1 ± 3.9 years), lean (%body fat [%BF]: 14.3 ± 8.0; %BF males: 9.7 ± 4.2; %BF females: 23.7 ± 4.2), and recreationally active (>150 min · wk(-1) of physical activity) male (n = 11) and female participants completed the trials. Using a double-blinded crossover design, participants performed sets of 3 maximum isokinetic efforts on a dynamometer (HumacNorm) before and after (5, 15, 30, 45, 60, 75, and 90 minutes after) ingesting either a carbohydrate (75 g glucose) or isovolumic placebo (saccharin-flavored) drink. Blood glucose and electromyography (EMG) were recorded concurrent with force output (max peak force; mean peak force). Despite a significant rise in blood glucose (mean glycemic excursion = 4.01 ± 1.18 mmol · L(-1)), there were no significant interactions in any (absolute or percentage) force (mean peak force: p ≥ 0.683; max peak force: p ≥ 0.567) or EMG (mean peak EMG: p ≥ 0.119; max peak EMG: p ≥ 0.247) parameters measured. The ingestion of glucose resulted in a 3.4% reduction in mean force across subsequent time points (highest: +2.1% at 15 minutes; lowest: -8.6% at 90 minutes after ingestion); however, this effect was small (d < 0.1). The ingestion of glucose does not alter performance of maximal isokinetic efforts in recreationally active young individuals. Additionally, there were no differences in force when assessed as a function of time after glucose ingestion. Consequently, in the absence of fatigue, carbohydrate ingestion is unlikely to present any ergogenic benefits to athletes performing resistance-based exercise.