Maximum O2 uptake, O2 debt and deficit, and muscle metabolites in Thoroughbred horses.

This research investigates the maximum allowance of oxygen uptake (VO2max), maximum oxygen deficit, and recovery of oxygen (O2 debt) in Thoroughbred racehorses during treadmill exercise. It also explores their metabolite levels in muscle tissues post-exercise.

Research Overview

• The study examined Thoroughbred racehorses and their physical responses to exercise, providing detailed insights into their oxygen consumption rates, their oxygen debt, and the ensuing metabolic changes at cellular levels.

Procedure and Measurements

• The researchers selected eight Thoroughbred horses for their study. They made these horses exercise on an inclined treadmill to measure their oxygen uptake in relation to speed.
• The oxygen uptake (VO2) kept on increasing linearly up to a speed limit of 10 m/s and VO2max values varied between 131 and 153 ml.kg-1.min-1.
• Post reaching their maximum oxygen uptake, six horses were subjected to further exercise, this time at 120% of their VO2max, until they reached exhaustion.
• The researchers measured variables such as VO2, the production of CO2 (VCO2), and concentration of plasma lactate (La) before, during, and after exercise (for an hour of recovery).

Muscle Biopsies

• Muscle biopsies were carried out at regular intervals (before and upto 60 minutes after exercise).
• Concentrations of various muscle metabolites like adenosine 5′-triphosphate (ATP), phosphocreatine (PC), La, glucose 6-phosphate (G-6-P), and creatine were determined. The pH of the muscles was also measured.

Findings

• The oxygen deficit recorded was 128 +/- 32 (SD) ml/kg mean (64 +/- 13 liters).
• The recovery oxygen uptake (oxygen debt) was 324 +/- 62 ml/kg (159 +/- 37 liters), around two to three times the values typically found in human beings.
• ATP concentration remained the same, but PC concentration was significantly lower than the pre-exercise values at less than or equal to 10 minutes of recovery.
• There was a negative correlation between PC concentration and VO2 during the fast and slow phases of recovery.
• Measured muscle lactate and glucose-6-phosphate were elevated for 10 minutes following exercise.
• The mean muscle pH decreased from a pre-exercise level of 7.05 to 6.75 at 1.5 minutes of recovery, and the mean peak plasma lactate value was 34.5 mmol/l.