Effects of low- and moderate-intensity training on metabolic responses to exercise in thoroughbreds.

The research article investigates the effects of varying exercise intensities on the metabolic responses in Thoroughbred horses. It concludes that the level of exercise intensity has minimal effect on various measured variables.

Methodology

• The researchers conducted experiments with ten Thoroughbred horses who had been resting in paddocks for four months before the project started.
• The horses underwent a training regimen of five days per week, for nine weeks. The training distances ranged from 1600m in the first week to 4000m in the ninth week.
• The group was divided at random into “fast” or “slow” subgroups, each of which ran the same distances daily.
• The speed for the “fast” subgroup was set to a level that induced a post-training blood lactate level of 4-8 mmol/l, while the “slow” group trained at half that speed (blood lactate < 2 mmol/l).
• Throughout the experiment, various physiological parameters were recorded, including heart rate (HR), oxygen consumption (VO2), carbon dioxide production (VCO2), and blood lactate concentration.
• Blood samples were collected at the end of each test to determine red cell and plasma volumes, and muscle biopsies were conducted to assess specific muscle responses to the training.

Results

• The researchers found minimal effects of the training intensity on the majority of the measured variables, leading them to combine the results for the two groups in most cases.
• The horses’ body weights remained stable regardless of the training regimen.
• Among the “fast” group, the economy of locomotion decreased slightly from before to after training.
• Training intensity did not affect run time to fatigue.
• Both groups exhibited an increase in VO2max (maximum rate of oxygen consumption), which correlated with run time.
• Also, the peak heart rates increased slightly after the first four weeks of training in both groups.
• Contrary to expectations, plasma volume decreased during the final three weeks of training, but blood volume, red cell volume, and red cell volume per bodyweight were not affected by intensity or duration of training.
• In the first five weeks of the training period, there was an increase in the activity of Citrate Synthase (CS), an enzyme involved in aerobic metabolism, in the muscles. However, the activity of HAD (3-Hydroxyacyl-CoA Dehydrogenase), another enzyme involved in metabolism, was not influenced by intensity or duration of training.