The effect of long-term exercise on glucose metabolism and peripheral insulin sensitivity in Standardbred horses

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Abstract

Reasons for performing study:

To study the possible long-term effect of improved glucose tolerance in horses after long-term training, as the impact of exercise training on glucose metabolism is still unclear in the equine species. It is not known whether there is a direct long-term effect of training or if the measurable effect on glucose metabolism is the residual effect of the last exercise session.

Objectives:

To determine the chronic effect on glucose metabolism and peripheral insulin sensitivity of long-term training in horses by use of the euglycaemic hyperinsulinaemic clamp technique.

Methods:

Eleven Standardbred horses were acclimatised to running on the high-speed treadmill for 4 weeks(Phase 1)followed by training for 18 weeks with an alternating endurance (∽ 60% HRmax) high intensity training programme (∽ 80% HRmax)(Phase 2).Training frequency was 4 days/week. At the end of Phase 1, a euglycaemic hyperinsulinaemic clamp was performed 72 h after the last bout of exercise in all horses. At the end ofPhase 2,the horses were clamped 24 h or 72 h after the last bout of exercise.

Results:

Glucose metabolism rate did not change significantly after 18 weeks of training, measured 72 h after the last exercise bout (0.018 ± 0.009 and 0.022 ± 0.006 mmol/kg bwt/min, respectively). Peripheral insulin sensitivity also did not change significantly following training (7.6 ± 5.7 x 10-6 and 8.0 ± 3.1 x 10-6, respectively). The same measurements 24 h after the last bout of exercise showed no significant differences.

Conclusions:

Results indicated that long-term training in Standardbreds neither changed glucose metabolism or insulin sensitivity 72 h after the last bout of exercise.

Potential relevance:

The fact that the beneficial effect of increased insulin sensitivity after acute exercise diminishes quickly in horses and no long-term effects on insulin sensitivity after chronic exercise have as yet been found in horses, implies that exercise should be performed on a regular basis in horses to retain the beneficial effect of improved insulin sensitivity.

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