Muscle adenine nucleotide degradation during submaximal treadmill exercise to fatigue.

The research studies the metabolic changes in the muscles of horses undergoing submaximal treadmill exercise, focusing on the degradation of adenine nucleotides. The study found evidence of adenine nucleotide breakdown during submaximal exercise, which may be related to the onset of fatigue.

Objectives and Methodology

• The purpose of the study was to explore how muscle metabolism responds to submaximal treadmill exercise until fatigue, with particular focus on the degradation of adenine nucleotides.
• Five Standardbred trotters performed treadmill exercises at two different speeds (7 m/s and 10 m/s) on two different occasions.
• Venous blood samples and muscle biopsies were collected at rest, during exercise, and after exercise. Muscle temperature was also recorded before and after exercise.
• The exercise duration varied among the horses, lasting from 48-58 minutes at 7 m/s and from 10-15.5 minutes at 10m/s.

Findings

• A gradual increase in plasma lactate and uric acid concentrations was observed during exercise at both speeds. However, post-exercise uric acid values were higher and lactate values were lower at 7 m/s speed compared to 10 m/s.
• No major changes were discerned in plasma concentrations of hypoxanthine or xanthine during the exercise.
• Muscle glycogen levels decreased after exercise irrespective of the speed, with some muscle fibers showing notable depletion.
• Muscle lactate concentrations increased after the exercise at both speeds.
• Adenosine triphosphate (ATP), Adenosine Diphosphate (ADP), and Adenosine Monophosphate (AMP) concentrations in the muscles showed no significant changes, except for a noticeable increase in inosine monophosphate (IMP) concentrations.

Conclusions

• This research suggests that AMP deamination, a process that results in an increase of IMP concentrations, occurs with submaximal exercise.
• This degradation of adenine nucleotides in the muscles might be linked to the development of fatigue during submaximal exercise.

This study could provide valuable insights into the metabolic changes occurring in the muscles during submaximal exercise, furthering our understanding of fatigue development in muscles and potentially leading to more efficient training and performance optimization strategies.