Influence of elevated muscle temperature on metabolism during intense, dynamic exercise

Area of Science:

• Exercise Physiology
• Muscle Metabolism

Background:

• Muscle temperature is a critical factor influencing metabolic responses during physical activity.
• Understanding how elevated muscle temperature affects energy production is vital for optimizing athletic performance and training.

Purpose of the Study:

• To investigate the direct effects of increased muscle temperature on intramuscular metabolic processes during high-intensity exercise.
• To determine if elevated muscle temperature alters energy substrate utilization and high-energy phosphate metabolism.

Main Methods:

• Seven active, untrained men performed two 2-minute cycle ergometer tests at 115% maximal oxygen uptake (VO2).
• One trial involved normal conditions (CT), while the other (HT) included pre-exercise thigh warming via a heating blanket.
• Muscle temperature (Tm), rectal temperature, plasma catecholamines, and intramuscular metabolites (adenine nucleotides, lactate, glycogen, creatine phosphate) were measured.

Main Results:

• Pre-exercise warming significantly elevated muscle temperature (Tm) in the HT trial compared to CT.
• During exercise, elevated Tm led to increased ATP degradation and accumulation of inosine 5'-monophosphate and ammonia.
• Post-exercise, higher lactate and lower glycogen concentrations were observed in the HT trial, indicating increased glycolysis and glycogenolysis.

Conclusions:

• Elevated muscle temperature per se enhances muscle glycogenolysis, glycolysis, and high-energy phosphate degradation during exercise.
• These metabolic alterations may stem from an increased rate of ATP turnover or shifts in the anaerobic/aerobic contribution to ATP resynthesis.