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Hearris, MA, Hammond, KM, Seaborne, RA, Stocks, B, Shepherd, SO, Philp, A, Sharples, AP, Morton, JP and Louis, JB (2019) Graded reductions in pre-exercise muscle glycogen impair exercise capacity but do not augment cell skeletal muscle signalling: implication for CHO periodisation. Journal of Applied Physiology. ISSN 8750-7587
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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-1α 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.
| Item Type: | Article |
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| Uncontrolled Keywords: | 06 Biological Sciences, 11 Medical and Health Sciences |
| Subjects: | R Medicine > RC Internal medicine > RC1200 Sports Medicine |
| Divisions: | Sport & Exercise Sciences |
| Publisher: | American Physiological Society |
| Date Deposited: | 07 May 2019 08:53 |
| Last Modified: | 04 Sep 2021 09:28 |
| DOI or ID number: | 10.1152/japplphysiol.00913.2018 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/10640 |
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