Changes in serum amino acid concentrations during prolonged endurance running

Area of Science:

• Exercise Physiology
• Human Metabolism
• Biochemistry

Background:

• Prolonged endurance exercise impacts substrate utilization and metabolic markers.
• Understanding metabolic shifts during sustained physical activity is crucial for optimizing performance and health.

Purpose of the Study:

• To investigate the metabolic responses to 3 hours of submaximal endurance exercise in trained distance runners.
• To examine changes in serum glucose, free fatty acids, urea, and amino acids, as well as urinary urea excretion.

Main Methods:

• Eight endurance-trained runners (5 male, 3 female) performed 3 hours of treadmill running at 60% VO2max.
• Blood samples were collected pre-exercise, every 30 minutes during exercise, and post-exercise.
• Urine samples were collected for the exercise day and a control day.

Main Results:

• Serum concentrations of alanine and proline significantly decreased, correlating with each other (r = 0.981).
• Serum glucose initially increased, then returned to resting levels; serum free fatty acids (FFA) significantly increased.
• Decreases in alanine and proline correlated with increases in FFA (r = -0.986 and r = -0.961, respectively).
• Total urinary urea excretion and urine volume were lower on the exercise day compared to the control day, with a significant decrease in urine volume.

Conclusions:

• Sustained submaximal exercise leads to significant alterations in amino acid and fuel metabolism in trained runners.
• The observed changes suggest a shift towards fat utilization and potential protein catabolism during prolonged endurance activity.
• Reduced urinary urea and fluid excretion indicate physiological adaptations to conserve resources during extended exercise.