Abstract

What is the central question of this study? Does achieving energy balance mainly with ingested fat in a 'sleep-low' model of training with low muscle glycogen affect the early training adaptive response during recovery? What is the main finding and its importance? Replenishing the energy expended during exercise mainly from ingested fat to achieve energy balance in a 'sleep-low' model does not enhance the response of skeletal muscle markers of early adaptation to training and impairs glycaemic control the morning after compared to training with low energy availability. These findings are important for optimizing post-training dietary recommendations in relation to energy balance and macronutrient intake. Training with low carbohydrate availability (LCHO) has been shown to acutely enhance endurance training skeletal muscle response, but the concomitant energy deficit (ED) in LCHO interventions has represented a confounding factor in past research. This study aimed at determining if achieving energy balance with high fat (EB-HF) acutely enhances the adaptive response in LCHO compared to ED with low fat (ED-LF). In a crossover design, nine well-trained males completed a 'sleep-low' protocol: on day1 they cycled to deplete muscle glycogen while reaching a set energy expenditure (30kcal(kg of fat free mass (FFM))-1 ). Post-exercise, low carbohydrate, protein-matched meals completely (EB-HF, 30kcal(kg FFM)-1 ) or partially (ED-LF, 9kcal(kg FFM)-1 ) replaced the energy expended, with the majority of energy derived from fat in EB-HF. In the morning of day2, participants exercised fasted, and skeletal muscle and blood samples were collected and a carbohydrate-protein drink was ingested at 0.5h recovery. Muscle glycogen showed no treatment effect (P<0.001) and decreased from 350±98to 192±94mmol(kg dry mass)-1 between rest and 0.5h recovery. Phosphorylation status of the mechanistic target of rapamycin and AMP-activated protein kinase pathway proteins showed only time effects. mRNA expression of p53 increased after exercise (P=0.005) and was higher in ED-LF at 3.5h compared to EB-HF (P=0.027). Plasma glucose and insulin area under the curve (P<0.04) and peak values (P≤0.05) were higher in EB-HF after the recovery drink. Achieving energy balance with a high-fat meal in a 'train-low' ('sleep-low') model did not enhance markers of skeletal muscle adaptation and impaired glycaemia in response to a recovery drink following training in the morning.

Highlights

  • Training with low endogenous and exogenous carbohydrate availability (LCHO) by means of strategically restricting carbohydrate intake can acutely enhance skeletal muscle response to endurance exercise (Bartlett, Hawley, & Morton, 2015)

  • During the energy deficit (ED) exercise, there was a faster increase in free fatty acids which resulted in higher peak values during ED (646 ± 241 μmol l−1) versus EB (466 ± 215 μmol l−1; P = 0.005)

  • The area under the curve for glucose between post-exercise and until 2.5 h postexercise was higher in EB versus ED and there were large effect sizes (113 ± 15 vs. 100 ± 15 arbitrary units (AU), respectively; ES, 0.82, 95% CL 0.16–1.48, P = 0.02)

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Summary

Introduction

Training with low endogenous and exogenous carbohydrate availability (LCHO) by means of strategically restricting carbohydrate intake can acutely enhance skeletal muscle response to endurance exercise (Bartlett, Hawley, & Morton, 2015). Provided that energy deficit can increase muscle oxidative capacity (Civitarese et al, 2007; Coen et al, 2015), it is unclear if a negative energy balance plays a role skeletal muscle adaptation during LCHO training. Increasing circulating fatty acids through diet could enhance skeletal muscle oxidative capacity through up-regulation of AMPK activity (Yeo et al, 2008), carnitine-acyl transferase activity (Goedecke et al, 1999), and fatty-acid translocase (FAT/CD36) (Cameron-Smith et al, 2003)

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