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


OBJECTIVE
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 (approximately 60% HRmax) high intensity training programme (approximately 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 of Phase 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.


CONCLUSIONS
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.
de Graaf-Roelfsema
E
E
The Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
van Ginneken
M E
ME
van Breda
E
E
Wijnberg
I D
ID
Keizer
H A
HA
van der Kolk
J H
JH
D000222:Adaptation, Physiological; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D005080:Exercise Test / Q000662:veterinary; D015309:Glucose Clamp Technique / Q000662:veterinary; D006736:Horses / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D007328:Insulin / Q000378:metabolism*; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D012420:Running / Q000502:physiology; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin