Exercise Metabolism: Fuels for the Fire

Abstract

During exercise, the supply of adenosine triphosphate (ATP) is essential for the energy-dependent processes that underpin ongoing contractile activity. These pathways involve both substrate-level phosphorylation, without any need for oxygen, and oxidative phosphorylation that is critically dependent on oxygen delivery to contracting skeletal muscle by the respiratory and cardiovascular systems and on the supply of reducing equivalents from the degradation of carbohydrate, fat, and, to a limited extent, protein fuel stores. The relative contribution of these pathways is primarily determined by exercise intensity, but also modulated by training status, preceding diet, age, gender, and environmental conditions. Optimal substrate availability and utilization before, during, and after exercise is critical for maintaining exercise performance. This review provides a brief overview of exercise metabolism, with expanded discussion of the regulation of muscle glucose uptake and fatty acid uptake and oxidation.

The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment

“…Skeletal muscle is a primary regulator of human metabolism. It acts as a major storage site for energy substrates and accounts for a large proportion of whole-body energy expenditure at rest and during exercise (19). By disrupting the body's circadian rhythm, acute and chronic sleep loss have the potential to profoundly affect muscle health.…”

Nutrition Strategies for Triathlon

“…The complexity of contemporary guidelines for the carbohydrate (CHO) and protein intakes of endurance athletes is well illustrated by their application to the needs of triathlon CHO is an important dietary nutrient since body stores are relatively limited and can be acutely manipulated by daily intake and even a single training session within a triathlete's program [20]. CHO is a key fuel for the brain and central nervous system and provides a versatile muscle substrate because it can support exercise over the large range of intensities seen in a triathlon due to its utilization by both anaerobic and oxidative pathways [20]. There is robust evidence that the performance of prolonged sustained or intermittent high-intensity exercise is enhanced by strategies that maintain high CHO availability, defined as matching endogenous (e.g.…”

“…CHO consumed during exercise) sources to the fuel demands of exercise [21,22]. Meanwhile, depletion of these stores is associated with fatigue in the form of reduced work rates, impaired skill and concentration, and increased perception of effort [20][21][22]. These findings underpin various race nutrition strategies, discussed subsequently, that supply carbohydrate before, during, and in the recovery between events to enhance carbohydrate availability, but should also be extended to training scenarios where high quality outputs or race simulation is desired.…”

Sodium citrate supplementation: An updated revision and practical recommendations on exercise performance, hydration status, and potential risks

“…Lactic acid immediately dissociates into H + and lactate ions (Lac‐), and this chemical event causes the acidification of the intracellular muscular environment. In particular, the exercise‐induced acidosis occurs when the production of H + overcomes the capacity of skeletal muscle disposal, and this event is followed by different consequences on cell energetics leading to muscle fatigue and performance reduction 1‐3 . As shown by several studies, 4,5 acidification is mirrored by a significant decrease of muscle pH from ~7.1 (at rest) to ~6.5 after high‐intensity exercise until exhaustion.…”