Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion

Raja, G., Brau, L., Palmer, T.N. and Fournier, P.A. 2008, Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion, American Journal of Physiology: Regulatory Integrative and Comparative Physiology, vol. 295, no. 2, pp. R633-R641, doi: 10.1152/ajpregu.00874.2007.

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Title Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion
Author(s) Raja, G.
Brau, L.ORCID iD for Brau, L. orcid.org/0000-0001-7105-8339
Palmer, T.N.
Fournier, P.A.
Journal name American Journal of Physiology: Regulatory Integrative and Comparative Physiology
Volume number 295
Issue number 2
Start page R633
End page R641
Total pages 10
Publisher American Physiological Society
Place of publication Bethesda, MD
Publication date 2008-06-02
ISSN 0363-6119
1522-1490
Keyword(s) Carbohydrate
Exercise
Glycogen synthesis
Regulation
Sprint
Summary Mild physical activity performed immediately after a bout of intense exercise in fasting humans results in net glycogen breakdown in their slow oxidative (SO) muscle fibers and glycogen repletion in their fast twitch (FT) fibers. Because several animal species carry a low proportion of SO fibers, it is unclear whether they can also replenish glycogen in their FT fibers under these conditions. Given that most skeletal muscles in rats are poor in SO fibers (<5%), this issue was examined using groups of 24-h fasted Wistar rats (n = 10) that swam for 3 min at high intensity with a 10% weight followed by either a 60-min rest (passive recovery, PR) or a 30-min swim with a 0.5% weight (active recovery, AR) preceding a 30-min rest. The 3-min sprint caused 61–79% glycogen fall across the muscles examined, but not in the soleus (SOL). Glycogen repletion during AR without food was similar to PR in the white gastrocnemius (WG), where glycogen increased by 71%, and less than PR in both the red and mixed gastrocnemius (RG, MG). Glycogen fell by 26% during AR in the SOL. Following AR, glycogen increased by 36%, 87%, and 37% in the SOL, RG, and MG, respectively, and this was accompanied by the sustained activation of glycogen synthase and inhibition of glycogen phosphorylase in the RG and MG. These results suggest that mammals with a low proportion of SO fibers can also replenish the glycogen stores of their FT fibers under extreme conditions combining physical activity and fasting.
Language eng
DOI 10.1152/ajpregu.00874.2007
Field of Research 110102 Medical Biochemistry: Carbohydrates
110602 Exercise Physiology
Socio Economic Objective 970111 Expanding Knowledge in the Medical and Health Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2008, The American Phsiological Society
Persistent URL http://hdl.handle.net/10536/DRO/DU:30048041

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