The Influence of Carbohydrate Availability on Exercise Performed at the Maximal Lactate Steady State
Date
2022-01-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The impact of carbohydrate (CHO) availability on time to task failure (TTF) and key physiological responses to exercise at the maximal lactate steady state (MLSS) has not been studied. The primary objective of this thesis was to determine how various levels of CHO availability affected TTF at MLSS. The secondary objectives of this thesis were to explore how changes in CHO availability impacted i) [BLa] and CHO oxidation rates at MLSS and ii) neuromuscular fatigue (NMF) and subjective ratings of fatigue and exertion when exercise is performed at MLSS. A combination of nutritional (carbohydrate [CHO] and placebo [PLA]) and exercise interventions (no exercise [REST] and glycogen depletion [GD]) created four conditions with distinct levels of CHO availability at the time of data collection (RESTCHO > RESTPLA > GDCHO > GDPLA). Specifically, CHO and PLA involved consuming beverages containing 7g or 0g of CHO per kg of body mass, respectively, and REST and GD involved no exercise intervention or a glycogen depletion intervention the evening prior to data collection, respectively. Ten participants (4 females, 6 males) completed this double blinded study. TTF at MLSS was not improved by CHO loading, as RESTCHO (57.1 ± 15.8 min) and RESTPLA (57.1 ± 14.8 min) were not significantly different (p = 1.0); however, TTF was significantly reduced in both GD conditions (p < 0.05), and GDCHO (39.1 ± 8.8 min) had a significantly longer TTF compared to GDPLA (20.6 ± 6.5 min; p < 0.001). Pre-TTF to post-TTF changes in NMF variables were not significantly different between conditions despite the large differences in TTF (p> 0.05). Further, at task failure, there was no significant differences in subjective ratings of fatigue and exertion (p > 0.05); however, prior to the TTF trial, participants reported significantly higher ratings of fatigue in GD conditions compared to rest conditions (p < 0.001), with no significant difference between GD conditions (p > 0.05). Finally, the magnitude of some physiological variables (i.e. [BLa] and RER) were impacted by CHO availability, but the pattern of these responses remained unchanged. These findings indicate that changes in CHO availability hinder MLSS determination through a reduction in TTF (i.e., inability to cycle for 30 min continuously), not via changes in metabolic responses to exercise at MLSS (i.e., [BLa] was stable in all conditions).
Description
Keywords
Exercise Physiology, Metabolism, Nutrition
Citation
Quinn, C. P. (2022). The Influence of Carbohydrate Availability on Exercise Performed at the Maximal Lactate Steady State (Master thesis). University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca .