Metabolic and hormonal changes after exercise in relation to muscle glycogen concentrations.

This research explores the changes in metabolic and hormone levels following exercise in relation to muscle glycogen concentrations in horses. The study found that neither elevating insulin levels nor increasing the availability of glucose precursor could significantly boost glycogen accumulation in the muscles post-exercise.

Methodology

• The study involved 9 trained half-breed riding horses, which underwent a 1.5 hour competition exercise test (CET) on a treadmill. Each horse performed the CET three times.
• After 30 minutes post-exercise, each horse was given one of three solutions: an isotonic glucose-electrolyte (GE) solution, GE supplemented with 50 grams of leucine (GEL) for enhancing insulin secretion, or GE supplemented with 200 ml propionic acid (GEP), a glucose precursor.

Results

• The administration of the GE solutions did not lead to an increase in plasma glucose concentration in the horses.
• Increased insulin concentration was found in both the GEL and the GE group indicating an insulin secretion response. However, the highest insulin concentration was measured after the GEL solution was administered.
• The GEP solution inhibited the increase in insulin concentration in horses.
• Glucagon levels rose after exercise, with specific increases noted 6 and 22.5 hours after CET.
• None of the post-exercise treatments significantly impacted the glycogen content 22.5 hours after CET.

Conclusions

• The research reveals that neither increasing insulin levels to boost muscle glucose uptake nor enhancing the availability of the glucose precursor, propionic acid, effectively increased the accumulation of glycogen in the middle gluteal muscle of the horses post-exercise.
• This finding challenges prevailing thoughts on how to best restore muscle glycogen after strenuous exercise in horses, suggesting that traditional methods may not be as effective as previously believed.