Publications

Publications Search

Search for publications by author
Search for publications by abstract keyword(s)

Graded reductions in preexercise muscle glycogen impair exercise capacity but do not augment skeletal muscle cell signaling: implications for CHO periodization

Abstract

We examined the effects of graded muscle glycogen on exercise capacity and modulation of skeletal muscle signaling pathways associated with the regulation of mitochondrial biogenesis. In a repeated-measures design, eight men 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% peak power output (PPO), followed by 1-min efforts at 80% PPO until exhaustion] the subsequent morning. After glycogen-depleting exercise, subjects ingested a total of 0 g/kg (L-CHO), 3.6 g/kg (M-CHO), or 7.6 g/kg (H-CHO) of carbohydrate (CHO) during a 6-h period before sleeping, such that exercise was commenced the next morning with graded (P < 0.05) muscle glycogen concentrations (means +/- SD: L-CHO: 88 +/- 43, M-CHO: 185 +/- 62, H-CHO: 278 +/- 47 mmol/kg dry wt). 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 AMPK(Thr172) phosphorylation (~4-fold) and PGC-1alpha mRNA expression (~5-fold) after exercise and 3 h after exercise, respectively. In contrast, neither exercise nor CHO availability affected the phosphorylation of p38MAPK(Thr180/Tyr182) or CaMKII(Thr268) or mRNA expression of p53, Tfam, CPT-1, CD36, or PDK4. Data demonstrate that when exercise is commenced with muscle glycogen < 300 mmol/kg dry wt, further graded reductions of 100 mmol/kg dry weight impair exercise capacity but do not augment skeletal muscle cell signaling. NEW & NOTEWORTHY We provide novel data demonstrating that when exercise is commenced with muscle glycogen below 300 mmol/kg dry wt (as achieved with the sleep-low, train-low model) further graded reductions in preexercise muscle glycogen of 100 mmol/kg dry wt reduce exercise capacity at 80% peak power output by 20-50% but do not augment skeletal muscle cell signaling.

Type Journal
ISBN 1522-1601 (Electronic) 0161-7567 (Linking)
Authors Hearris, M. A.; Hammond, K. M.; Seaborne, R. A.; Stocks, B.; Shepherd, S. O.; Philp, A.; Sharples, A. P.; Morton, J. P.; Louis, J. B.
Responsible Garvan Author Dr Andy Philp
Publisher Name JOURNAL OF APPLIED PHYSIOLOGY
Published Date 2019-06-01
Published Volume 126
Published Issue 6
Published Pages 1587-1597
Status Published in-print
DOI 10.1152/japplphysiol.00913.2018
URL link to publisher's version https://www.ncbi.nlm.nih.gov/pubmed/31046515