Fuel for the work required: a practical approach to amalgamating train-low paradigms for endurance athletes

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.

Periodization of Carbohydrate Intake: Short-Term Effect on Performance

“…The lack of any effect of the SL strategy on substrate oxidation is similar to the findings of our first study using a three-week SL strategy [15], but contrasts with the observations from previous studies on training with low glycogen availability. Typically, these studies report higher activity of enzymes involved in fat metabolism [12,13], and changes in transcription for adaptive genes [14] or factors involved in mitochondrial biogenesis [17]. However, a difference between our study and others is that our performance tests were undertaken pre- and post- intervention with subjects following strategies of high CHO availability (i.e., high CHO diet in the preceding day, pre-exercise CHO intake, CHO intake during the exercise).…”

“…This has led to interest in a “periodized” approach to CHO availability in the training program, where sessions undertaken to promote adaptation are carefully integrated with others focused on high quality performance outcomes. The “sleep-low” (SL) strategy represents one such sequence of periodized CHO availability, which allows athletes to perform high intensity training sessions supported by high CHO availability while enhancing metabolic adaptation associated with low glycogen availability [14,15,16,17]. …”

Insulin, glucose and beta-hydroxybutyrate responses to a medium-chain triglyceride-based sports supplement: A pilot study

“…In dramatic opposition to the highcarbohydrate diets and frequent 'carb-loading' strategies previously used by endurance athletes, many elite longdistance runners, triathletes and cyclists are now employing regular carbohydrate restriction, including during races, to improve performance. 8,20,21 This approach was largely pioneered by the work of Jeff Volek and Stephen Phinney, as well other high-profile medical doctors such as Timothy Noakes and Philip Maffetone. 1,22,23 As such, there is increasing interest in supplements that can be used to fuel prolonged endurance efforts without large increases in blood glucose and insulin that would suppress endogenous fatty acid oxidation.…”

“…Restricting carbohydrates may also result in greater glycogen depletion, increasing AMPK activation and promoting pathways associated with mitochondrial biogenesis. 21,25 However, other data suggest that endurance exercise itself is the largest stimulus for mitochondrial biogenesis regardless of carbohydrate timing 26 and that the signalling benefits of training in a carbohydrate-restricted state may be enhanced by consuming a carbohydrate source during the recovery period. 21 Other than the signalling effects of lower carbohydrate availability during exercise, the antiinflammatory and epigenetic (via histone deacetylase inhibition) effects of elevated ketone bodies such as BHB after carbohydrate restriction may provide other beneficial adaptations for the endurance athlete.…”

“…21,25 However, other data suggest that endurance exercise itself is the largest stimulus for mitochondrial biogenesis regardless of carbohydrate timing 26 and that the signalling benefits of training in a carbohydrate-restricted state may be enhanced by consuming a carbohydrate source during the recovery period. 21 Other than the signalling effects of lower carbohydrate availability during exercise, the antiinflammatory and epigenetic (via histone deacetylase inhibition) effects of elevated ketone bodies such as BHB after carbohydrate restriction may provide other beneficial adaptations for the endurance athlete. 27,28 Despite a greater contribution of fatty acids to TEE during aerobic exercise, keto-adapted athletes deplete muscle glycogen at a similar rate to athletes consuming a carbohydrate-based diet.…”