Muscular adaptation of horses during intensive training and detraining

Abstract

Five horses were studied during a five-week regime of controlled intensive daily training on a high-speed treadmill followed by five weeks of detraining. Muscle biopsies were taken weekly from both the right and left gluteus muscle and from the sternocephalicus muscle before, and at the end of, the training and detraining periods. Histochemical and biochemical analyses of the sternocephalicus muscle showed no metabolic adaptation with either training or detraining. No significant differences were observed in any of the analysed parameters in the gluteus muscle between contralateral sites. Glycogen levels decreased by 10 to 15 per cent after one to two weeks of training, remained low during the training period and increased to pretraining levels after one week's cessation of training. Citrate synthase activity increased rapidly and was 27 per cent higher after one week and 42 per cent higher after five weeks of training. Lactate dehydrogenase activity decreased by 15 per cent during this period. The changes seen in these enzyme levels persisted during the detraining period. No alterations were seen in fibre type composition but type IIA fibre areas decreased by 19 per cent after five weeks training and capillary density increased by 17 per cent. It is concluded that a period of intensive training will rapidly increase the oxidative capacity and the capillary density in an actively working muscle, and that these metabolic adaptations are well maintained during a subsequent period of detraining.

Skeletal muscle adaptations to prolonged training, overtraining and detraining in horses

“…Most studies investigating training in horses have shown few if any changes in fibre area in response to the training stimulus [9,10,16]. The increased fibre area in all fibre types during the high-intensity phase of training (phase 2) in the current study indicates that high-intensigram in horses [10].…”

“…Studies investigating skeletal muscle adaptations to training in horses have found up to twofold increases in aerobic enzyme activity [9,10,15,16,19,26] and increases in capillarisation of muscle [17]. Straub et al [33] have found an increase in volume density of mitochondria after 4 weeks of training in horses.…”

A forage-only diet alters the metabolic response of horses in training

“…This suggests that horses are well adapted to rely on fat metabolism and aerobic energy supply at rest, but probably also during exercise. The adaptation to, and importance of, aerobic substrate utilisation during exercise in Thoroughbred and Standardbred horses has been documented in a number of studies (Lindholm and Piehl, 1974;Wilson et al, 1987;Essé n-Gustavsson et al, 1989) and is also confirmed by the correlation between the performance of Standardbred horses and plasma lactate threshold (V La4 ) (Persson, 1983). Equine muscle also shows high plasticity with respect to its adaptation to energetic demands as a result of exercise training (Voiton et al, 2007).…”

Myosin heavy chain‐based fibre types in red cell hyper‐ and normovolaemic Standardbred trotters

“…It is well known that skeletal muscle of well-trained horses have high type IIA/IIB ratios, oxidative capacities and capillary supplies (Essén-Gustavsson and Lindholm 1985;Essén-Gustavsson et al 1989;Karlström et al 1991). The gluteus medius muscle of HV horses has previously been analysed histochemically and compared to muscle of NV horses.…”