Temperature-induced changes in metabolic and hormonal responses to intensive dynamic exercise

Area of Science:

• Exercise Physiology
• Muscle Metabolism
• Environmental Extremes

Background:

• Muscle temperature significantly influences metabolic responses during exercise.
• Understanding the impact of cold muscle on energy production is crucial for athletic performance and injury prevention.

Purpose of the Study:

• To investigate the metabolic and circulatory effects of subnormal muscle temperature during intensive cycle exercise.
• To compare physiological responses at subnormal muscle temperature (Tm) versus normal Tm.

Main Methods:

• Seven male subjects underwent intensive cycle exercise to exhaustion at both subnormal (29°C) and normal (35°C) muscle temperatures.
• Measurements included arterial and femoral venous blood gases, lactate, catecholamines, calf blood flow, and muscle metabolite concentrations.

Main Results:

• Subnormal Tm resulted in higher arterial and femoral venous oxygen content due to increased hemoglobin concentration, but similar arterial-femoral venous oxygen difference.
• Plasma adrenaline and noradrenaline were elevated at subnormal Tm. Calf blood flow was reduced at rest and post-exercise in the cold.
• Muscle glucose-6-phosphate and lactate concentrations were significantly higher post-exercise at subnormal Tm.

Conclusions:

• Subnormal muscle temperature during exercise may increase glycolysis, potentially due to reduced work efficiency and/or impaired blood flow.
• Cold-induced changes in muscle metabolism warrant further investigation in athletic and clinical settings.