The research article investigates the changes in metabolic responses in Thoroughbred horses when subjected to high-intensity interval training with varying rest periods. The authors noted significant differences in metabolite concentrations after bouts of exercises and the effects these changes have on energy production.

Objective of the Research

• The purpose of the study was to explore the underlying physiological mechanisms behind high-intensity interval training. By assessing fluctuating metabolite concentrations in equine skeletal muscles, the researchers sought to shed light on the effects of rest intervals on the physiological adaptations prompted by high-intensity exercise.

Study Design and Analysis

• The experiment involved Thoroughbred horses undergoing high-intensity interval training. The training sessions differed in their rest intervals, which were either 15 minutes or 2 minutes.
• Using metabolomics techniques, the researchers studied changes in metabolic network responses to these exercises. Specifically, they tracked metabolite concentrations in the horses’ skeletal muscles as an indicator of energy production and use.
• The study also measured peak plasma lactate levels and arterial oxygen saturation throughout the trial.

Key Findings of the Research

• The researchers observed that the peak plasma lactate level was notably higher during the high-intensity exercise with a 2-minute rest interval than during the interval with a 15-minute rest. This data relates to the muscle lactate concentrations usually associated with anaerobic exercise and indicates that the shorter rest interval likely pushed the horses’ systems into more intense energy usage and potential anaerobic conditions.
• Arterial oxygen saturation dropped to a lower level at the end of all exercise sessions with a 2-minute rest than in sessions with a 15-minute rest. This drop could signify the horses’ increased oxygen demands during intense exercise and the reduced ability to restore oxygen levels with shorter rest periods.
• In the 15-minute rest interval sessions, significant changes in metabolite concentrations were noted immediately following the first and third bouts. In comparison, the 2-minute rest sessions did not exhibit significant changes of this type.

Conclusion of the Research

• The study concludes that changes in the activity of each energy production system may not always translate directly into apparent changes in metabolite concentrations. This phenomenon might arise from better sync between metabolite flux and the pathway and cycle, as well as between metabolite production and disposal.
• The study highlights that the number of repetitions and the length of rest periods between exercises greatly affect metabolite concentrations, even if the exercises are identical. This finding can influence our understanding of designing high-intensity interval training for optimal physiological adaptations.