title: 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.
authors.affiliation: 1School of Psychology and Exercise Science, Murdoch University, Murdoch, Australia;2School of Health Professions, Murdoch University, Murdoch, Australia; and3Kinesiology and Physical Education program, College of Education and Human Development, The University of Maine, Orono, Maine.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Fairchild
authors.forename: Paul
authors.initials: P
authors.lastname: Dillon
authors.forename: Caroline
authors.initials: C
authors.lastname: Curtis
authors.forename: Alasdair R
authors.initials: AR
authors.lastname: Dempsey
mesh_terms: D000328:Adult; D001628:Beverages; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004576:Electromyography; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D053580:Muscle Strength / Q000187:drug effects*; D058573:Performance-Enhancing Substances / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D058573:Performance-Enhancing Substances; D005947:Glucose