Skip to main content

Research Repository

Advanced Search

Graded reductions in pre-exercise muscle glycogen impair exercise capacity but do not augment cell skeletal muscle signalling: implication for CHO periodisation

Graded reductions in pre-exercise muscle glycogen impair exercise capacity but do not augment cell skeletal muscle signalling: implication for CHO periodisation Thumbnail


Abstract

We examined the effects of graded muscle glycogen on exercise capacity and modulation of skeletal muscle signalling pathways associated with the regulation of mitochondrial biogenesis. In a repeated measures design, eight males completed a sleep-low, train-low model comprising an evening glycogen depleting cycling protocol followed by an exhaustive exercise capacity test (8 x 3 min at 80% PPO, followed by 1 min efforts at 80% PPO until exhaustion) the subsequent morning. Following glycogen depleting exercise, subjects ingested a total of 0 g kg-1 (L-CHO), 3.6 g kg-1 (M-CHO) or 7.6 g kg-1 (H-CHO) of carbohydrate during a 6 h period prior to sleeping, such that exercise was commenced the next morning with graded (P < 0.05) muscle glycogen concentrations (Mean ± SD) (L-CHO: 88 ± 43, M-CHO: 185 ± 62, H-CHO: 278 ± 47 mmol kg-1 dw). Despite differences (P < 0.05) in exercise capacity at 80% PPO between trials (L-CHO: 18 ± 7, M-CHO: 36 ± 3, H-CHO: 44 ± 9 min) exercise induced comparable AMPKThr172 phosphorylation ( 4 fold) and PGC-1a mRNA expression ( 5 fold) post- and 3 h post-exercise, respectively. In contrast, exercise nor CHO availability affected the phosphorylation of p38MAPKThr180/Tyr182, CaMKIIThr268 or mRNA expression of p53, Tfam, CPT-1, CD36 or PDK4. Data demonstrate that when exercise is commenced with muscle glycogen below 300 mmol kg-1 dw, further graded reductions of 100 mmol kg-1 dw impair exercise capacity but do not augment skeletal muscle cell signaling.

Acceptance Date Apr 30, 2019
Publication Date Jun 1, 2019
Publicly Available Date Mar 28, 2024
Journal Journal of Applied Physiology
Print ISSN 8750-7587
Publisher American Physiological Society
Pages 1587-1597
DOI https://doi.org/10.1152/japplphysiol.00913.2018
Keywords exercise capacity, mitochondrial biogenesis, muscle glycogen, train low, sleep low
Publisher URL http://dx.doi.org/10.1152/japplphysiol.00913.2018

Files




Downloadable Citations