Equine muscle glycogen stores require sufficient time for post-exercise repletion. Repletion cannot be hastened in any way other than rest.
For his thesis, Licentiate in Veterinary Medicine Seppo Hyyppä, from MTT Agrifood Research Finland, investigated post-exercise muscle glycogen repletion in horses. Glycogens are the carbohydrate stores in muscle. They are the most important nutrient during exercise. If glycogen stores are depleted the horse makes use of its own muscle protein stores as raw material for energy. This has a detrimental effect on muscle and on muscle performance. Over a longer period the improvement in fitness of the horse may decelerate or even come to a halt.
"If the diet is normal and the horse consumes the feed provided, neither extra carbohydrate nor extra fat will enhance the repletion of muscle glycogen stores. Dietary supplements may actually inhibit repletion", says Hyyppä.
Maintaining horses in a good state of hydration seems to have a moderate positive effect on repletion of muscle glycogen stores. Providing horses with an isotonic glucose-electrolyte rehydration solution soon after exercise helps to overcome dehydration significantly better than providing them with plain water.
Positive anabolic hormonal balance within the body aids the repletion of muscle glycogen stores; the trainer therefore needs to ensure exercise is suitable for the horse, with sufficient recovery time between intense training periods. During the most recent research project a horse was given anabolic steroids to ensure anabolic hormonal balance. This had a clear, positive effect on the repletion of muscle glycogen stores. Hyyppä emphasizes that anabolic steroids were administered solely for the purpose of establishing the significance of hormonal balance.
Observing the horse's condition
A rigorous training programme, for example, in trotting, may lead to progressive depletion of muscle glycogen stores, to the probable detriment of the horse’s condition in the long run.
Weighing the horse before and after exercise provides a reasonably accurate picture of repletion.
"If scales are unavailable, recording the horse’s chest measurement will indicate changes in weight. Obviously this will not be the case" , Hyyppä points out, "if the horse is already too thin".
Hyyppä stresses that the well-being and condition of the horse may be monitored, in addition to weight measurement, by observing the horse’s general alertness and, for example, suppleness or stiffness when initiating movement. A healthy appetite, too, reveals a good condition. Other good indicators are resting heart rate and body temperature; increases in these measurements are a sign that the training programme is in need of revision.
Hyyppä feels that people must get to know their horses and develop an eye for such changes. "If one person trains a horse and another person looks after it, a wealth of equine information will fall by the wayside", Hyyppä says.
Controlled exercise on the treadmill
The horses performed the physical tests at the Ypäjä trotting track and on MTT’s equine research treadmill. MTT’s own horses and horses from the Equine College were employed in the research. The treadmill was designed and built through cooperation involving MTT’s Equine Research, the Tampere University of Technology, and local enterprises. The treadmill has achieved notable success as an export product.
"The treadmill is a useful method for exercising horses under controlled conditions. Horses perform exercise by walking, trotting and galloping, from between half-an-hour and an hour-and-a-half at a time ", Hyyppä says.
Analysis of the research was carried out at the MTT laboratory in Ypäjä, and at the University of Helsinki’s Faculty of Veterinary Medicine, Department of Basic Veterinary Sciences.
Licentiate in Veterinary Medicine Seppo Hyyppä’s thesis in Basic Veterinary Sciences, ”Post-exercise Muscle Glycogen Repletion in Horses”, will be examined at the University of Helsinki on 12 November 2007. Professor Birgitta Essen-Gustavsson from the Swedish University of Agricultural Sciences will act as opponent and Professor Reeta Pösö from the University of Helsinki as custodian.
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