Summary Ten trotting Standardbred colts were recorded by high‐speed cinematography at the ages of eight, 12 and 18 months. The horses were trotting on a treadmill operating at 4.0 m/secs. Five horses were subjected to a programme of intensified training from eight months of age, whereas the others were not trained and acted as controls. The films were analysed on a semi‐automatic film‐reading equipment and a number of variables used to demonstrate the gait symmetry were calculated and scaled by computer. Certain differences between left and right diagonal and contralateral pair of limbs, respectively, were noted, suggesting that laterality in horses may be inherited. The most pronounced systematic differences were found in 18‐month old horses in the trained group. The results show the importance of careful gait examination and comprehensive coordination training at an early age.
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.
Summary Although different physiological and behavioural attributes are needed for various types of equine competition, successful racing depends primarily on the animal's metabolic ability to convert chemical energy to mechanical energy — the function of muscle. Components of these energetic processes include the rate, efficiency and interaction of aerobic and anaerobic metabolism in muscle and the supply and utilisation of fuel. In anaerobic work like racing, fatigue processes may be largely regarded as a function of an intramuscular fuel (phosphogen) depletion, despite the fact that substrates are supplied via the circulation. Physical work capacity in the horse depends then mainly on the rate of aerobic metabolism and the capacity of the anaerobic processes to supply energy for continued muscle contraction. Underlying these processes are physiological limitations of the cardiovascular system and the ultrastructure and biochemistry of muscle. A model is proposed whereby prediction of equine performance is based entirely on parameters of energy metabolism. Résumé Des aptitudes physiologiques et des qualités de comportement sont nécessaires pour satisfaire aux exigences variées de la compétition équine. Nonobstant ceci le succès en course dépend d'abord de l'aptitude métabolique de l'animal à convertir l'énergie chimique en énergie mécanique: c'est le rôle des muscles. Les facteurs de ces phénomènes énergétiques sont en particular la rapidité l'efficacité et les interactions des métabolismes aérobies et anaerobies dans le muscle; aussi l'alimentation et l'aptitude à utiliser les sources d'énergie. Dans une activité anaerobic telle que la cour se, les phénomènes de fatigue peuvent être considérés comme dépendant largement d'un appauvrissement des sources musculaires d'énergie (phosphogène); ceci en dépit des apports énergétiques du système circulatoire. L'aptitude du cheval au travail physique dépend donc beaucoup de la rapidité du métabolisme aérobic et de la capacité des phénomènes anaérobics à fournir l'énergie pour la contraction musculaire. Mais le muscle — dans sa structure profonde et dans sa biochimieet le système cardiovasculaire comportent des limites physiologiques. On propose un modèle pour lequel la prévision des performances est fondée sur des paramètres du métabolisme énergétique. Zusammenfassung Obgleich verschiedene physiologische und verhaltensbestimmende Attribute für die verschiedenen Zweige des Pferdesports notwendig sind, kann man festhalten, dass Erfolge im Rennsport vor allem abhängen von der Fähigkeit des Tieres, chemische Energie in mechanische zu verwandeln: die Funktion der Muskulatur. Diese energetischen Vorgänge setzen sich zusammen aus der Geschwindigkeit, der Effizienz und der Interaktion aerober und anaerober Stoffwechselprozesse im Muskel und der Versorgung und Verbrennung von Brennstoff. Während einer anaeroben Arbeit (Rennen) können Ermüdungserscheinungen vor allem als Funktion einer intramuskulären Brennstoffunterversorgung (Phosphogen) angesehen werden, trotz des Umstandes, d...
Age, height, mass, fat-free mass and vital capacity were used as predictors of maximum aerobic power (VO2 max). The variables were cast in linear form by logarithmic transfomation and submitted to multiple regression analysis. Results indicate VO2 max as a power function of age, height and mass in 50 untrained boys aged 7 to 13 years. In this group the relationship between VO2 max and body mass may be expressed by the equation Y=0.076X0.88 (r=0.92, P <0.01). Age, height and mass together accounted for 89 per cent of the variance in VO2 max (R=0.94, P <0.01). In 30 girl swimmers and in 14 young boys during 22 months of running training, VO2 max was proportional to body mass and indicated greater maximum aerobic power for their size and age. In normally growing children, VO2 max appears to increase more slowly than body mass. Children subjected to aerobic training evidently maintain VO2 max in proportion to their increasing mass throughout adolescence.
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