Abstract
Using an amalgamation of previously studied “train‐low” paradigms, we tested the effects of reduced carbohydrate (CHO) but high leucine availability on cell‐signaling responses associated with exercise‐induced regulation of mitochondrial biogenesis and muscle protein synthesis (MPS). In a repeated‐measures crossover design, 11 males completed an exhaustive cycling protocol with high CHO availability before, during, and after exercise (HIGH) or alternatively, low CHO but high protein (leucine enriched) availability (LOW + LEU). Muscle glycogen was different (P < 0.05) pre‐exercise (HIGH: 583 ± 158, LOW + LEU: 271 ± 85 mmol kg−1 dw) but decreased (P < 0.05) to comparable levels at exhaustion (≈100 mmol kg−1 dw). Despite differences (P < 0.05) in exercise capacity (HIGH: 158 ± 29, LOW + LEU: 100 ± 17 min), exercise induced (P < 0.05) comparable AMPK α2 (3–4‐fold) activity, PGC‐1α (13‐fold), p53 (2‐fold), Tfam (1.5‐fold), SIRT1 (1.5‐fold), Atrogin 1 (2‐fold), and MuRF1 (5‐fold) gene expression at 3 h post‐exercise. Exhaustive exercise suppressed p70S6K activity to comparable levels immediately post‐exercise (≈20 fmol min−1 mg−1). Despite elevated leucine availability post‐exercise, p70S6K activity remained suppressed (P < 0.05) 3 h post‐exercise in LOW + LEU (28 ± 14 fmol min−1 mg−1), whereas muscle glycogen resynthesis (40 mmol kg−1 dw h−1) was associated with elevated (P < 0.05) p70S6K activity in HIGH (53 ± 30 fmol min−1 mg−1). We conclude: (1) CHO restriction before and during exercise induces “work‐efficient” mitochondrial‐related cell signaling but; (2) post‐exercise CHO and energy restriction maintains p70S6K activity at basal levels despite feeding leucine‐enriched protein. Our data support the practical concept of “fuelling for the work required” as a potential strategy for which to amalgamate train‐low paradigms into periodized training programs.
Highlights
Traditional nutritional strategies for endurance athletes have typically advised high carbohydrate (CHO) availability before, during, and after training sessions in order to support high daily training volume and intensities (Burke et al 2011)
Confirming our hypothesis, we provide novel data by demonstrating that reduced CHO availability impaired exercise capacity, our CHO restriction protocol induced comparable AMPK-PGC-1a signaling, inducing “work-efficient” signaling responses
Refraining from CHO intake in the post-exercise period maintains p70S6K activity at basal levels. These data have practical implications by suggesting that: (1) CHO restriction before and during exercise induces work-efficient cell signaling related to mitochondrial biogenesis but ; (2) complete CHO and energy restriction in the post-exercise period reduces the activation of key signaling proteins regulating skeletal muscle modeling processes
Summary
Traditional nutritional strategies for endurance athletes have typically advised high carbohydrate (CHO) availability before, during, and after training sessions in order to support high daily training volume and intensities (Burke et al 2011). In the last decade, accumulating data demonstrate that strategic periods of reduced CHO availability (the so-called “train-low” paradigm) augments selected skeletal muscle markers of training adaptation (Hawley and Morton 2014; Bartlett et al 2015). Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society In the context of nutrient-gene interactions, it is apparent that the acute molecular regulation of cell signaling processes provides a theoretical basis for understanding the molecular mechanisms underpinning chronic training adaptations
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