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Lookup NU author(s): Dr Fiona Smith, Professor Peter ThelwallORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025 The Author(s). The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.Abstract: Post-exercise carbohydrate intake is required to replenish endogenous glycogen stores. Although adequate carbohydrate consumption has been reported to restore muscle glycogen contents within 24 h of post-exercise recovery, the time required to replenish liver glycogen contents is less evident. Twelve well-trained male cyclists (age: 25 ± 5 years; V̇O2peak: 67 ± 5 ml/min/kg; Wmax: 5.8 ± 0.7 W/kg) participated in this trial. Ultra-high-field (UHF) 13C magnetic resonance spectroscopy (13C MRS) was applied to assess muscle and liver glycogen concentrations before and immediately after glycogen-depleting exercise on two test days. This was followed by 12 h of recovery during which participants remained fasted (CON) or consumed 10 g carbohydrate per kg body mass (BM) in the form of sucrose-containing beverages (1.2 g/kg BM/h over the first 6 h) and carbohydrate-rich meals (CHO). Muscle and liver glycogen concentrations were again assessed at 6 and 12 h into recovery using 13C MRS. Furthermore muscle biopsies were collected to assess muscle glycogen concentrations using biochemical analysis. Exercise significantly reduced muscle (from 159 ± 32 to 56 ± 19 mmol/l; −64%) and liver (from 166 ± 40 to 110 ± 44 mmol/l; −34%) glycogen concentrations (P < 0.05), with no significant differences between test days (P > 0.05). In the absence of carbohydrate intake (CON) muscle and liver glycogen concentrations remained unchanged during recovery. After carbohydrate intake (CHO) muscle glycogen concentrations increased from 56 ± 19 to 88 ± 16 and 110 ± 19 mmol/l (or from 269 ± 90 to 418 ± 78 and 523 ± 92 in mmol/kg dry mass), after 0, 6 and 12 h of recovery, respectively, remaining well below pre-exercise values (i.e. 55% of pre-exercise at 6 h and 69% at 12 h). Liver glycogen concentrations increased from 110 ± 44 to 236 ± 39 and 258 ± 40 mmol/l, after 0, 6 and 12 h of recovery, respectively, exceeding pre-exercise values within 6 h of recovery (i.e. 142% of pre-exercise). A very strong correlation (r = 0.89, P < 0.001), good agreement (ICC: 0.87) and low bias (4.1 ± 23.7 mmol/l) were observed when comparing muscle glycogen concentrations assessed using 13C MRS and biochemical analyses. Sucrose ingestion (1.2 g/kg BM/h) fully restored liver glycogen concentrations well within 6 h of post-exercise recovery. Ingesting large amounts of carbohydrate (10 g/kg BM) did not allow muscle glycogen stores to be replenished within 12 h of post-exercise recovery. (Figure presented.). Key points: Carbohydrate ingestion is required to replenish muscle and liver glycogen stores after a strenuous bout of exercise. Carbon-13 magnetic resonance spectroscopy at ultra-high-field (7T) allows non-invasive measurement of both muscle and liver glycogen contents before and after exercise, and at 6 and 12 h of recovery with (CHO) and without (CON) carbohydrate ingestion (10 g per kg body mass). Exercise strongly reduces glycogen contents of both muscle and liver tissue. Without carbohydrate ingestion muscle and liver glycogen levels remain depleted. After ingestion of large amounts of carbohydrate both muscle and liver glycogen contents increase rapidly, with liver glycogen stores being fully repleted within 6 h. Ample carbohydrate ingestion allows rapid replenishment of liver but not muscle glycogen stores within 6 and 12 h of post-exercise recovery.
Author(s): Fuchs CJ, Veeraiah P, Hermans WJH, Brauwers B, Voncken R, Brouwers K, Petrick HL, Hendriks FK, Bels JLM, van den Hurk J, Weber J, Senden JM, Smith FE, Thelwall PE, Prompers JJ, van Loon LJC
Publication type: Article
Publication status: Published
Journal: Journal of Physiology
Year: 2025
Pages: epub ahead of print
Online publication date: 20/08/2025
Acceptance date: 29/07/2025
Date deposited: 02/09/2025
ISSN (print): 0022-3751
ISSN (electronic): 1469-7793
Publisher: John Wiley and Sons Inc
URL: https://doi.org/10.1113/JP289115
DOI: 10.1113/JP289115
Data Access Statement: All data generated and analysed during this study are available from the corresponding author on reasonable request
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