Carbohydrate Availability and Training Adaptation: Effects on Cell Metabolism

John A. Hawley; Louise M. Burke

Disclosures

Exerc Sport Sci Rev. 2010;38(4):152-160. 

In This Article

Summary and Conclusions

This review has summarized the effects of manipulating carbohydrate availability on endurance training adaptation. Current evidence supports the hypothesis that commencing a portion of short-term (3–10 wk), endurance-based training programs in the face of low muscle glycogen content and/or low exogenous carbohydrate availability promotes training adaptation (i.e., mitochondrial biogenesis) to a greater extent than when subjects undertake a similar training regimen with normal or elevated glycogen levels. Although several putative cell signaling pathways have been implicated in this nutrient-exercise adaptation process (i.e., the AMPK and p38 MAPK), further work is required to determine the precise mechanisms promoting the amplified endurance training adaptation when individuals commence selected training sessions with low carbohydrate availability. There are several studies of the acute effects of commencing resistance-based exercise in the face of low muscle glycogen stores;[8,12] however, the results from these investigations suggest that such a practice may have a negative impact on cellular growth and adaptation. Indeed, low muscle glycogen content has variable effects on transcription of select metabolic and myogenic genes at rest, with any differences in basal transcription being completely abolished after a single bout of heavy resistance training. For now, it seems prudent to suggest that competitive athletes may wish to manipulate carbohydrate availability before, during, or after selected training sessions that form part of a long-term periodized training-nutrition plan to promote metabolic training adaptations that should, in theory, promote endurance-based performances.

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