Muscle Fiber Types of Gluteus Medius in the Colombian Creole Horse

Blood lactate concentrations and heart rates of Colombian Paso horses during a field exercise test

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The heart rate during the field exercise test increased according to the protocol used.

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The blood lactate concentration values during the test were remarkably dispersed.

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The mean blood lactate clearance percentage was 56.3 ± 16, similar in most animals.

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The heart rate at which a blood lactate concentration of 4 mmol/L was reached was notably different among individuals.

Information on performance indices in Paso horses is scarce. Field exercise tests are necessary to recreate the exertion that occurs during training and competition.

To describe blood lactate concentrations and heart rates of untrained Colombian Paso horses (CPHs) in response to a field exercise test.

A 30-minutes-long standardized field exercise test was carried out on 11 untrained adult CPHs of both sexes. Blood lactate concentration (BLConc) and heart rate (HR) were measured before, during each step of the test, and at recovery. The BLConc and HR were used to calculate the HR at which a BLConc of 4 mmol/L or anaerobic threshold (HRL₄) was reached.

The HR during the field exercise test increased according to the protocol used. The BLConc during the test was variable and, despite having been increasing like the HR, the distribution of the values in each step of the test was remarkably dispersed. The mean blood lactate clearance (BLClear) percentage was 56.3 ± 16, similar in most animals. The HRL₄ was reached at a notably different HR among individuals (132 to 251 bpm).

The field exercise test protocol used herein is useful to assess BLConc and HR changes in acute response to exercise in CPHs. It would be useful to evaluate training kinetics with other parameters including cell blood count and muscle enzymes.

Dietary conjugated linoleic acid supplementation alters skeletal muscle mitochondria and antioxidant status in young horses

Conjugated linoleic acid (CLA) improves oxidative stress and mitochondrial biogenesis in various species but has not been thoroughly investigated in horses. We collected blood and muscle samples from lightly exercising horses before and 6 and 12 wk after receiving either soybean oil (CON; n = 5) or CLA (CLA; n = 5) supplementation. Samples were analyzed for markers of mitochondrial characteristics, antioxidant status, oxidative stress, and muscle damage. Data were analyzed using a linear model with repeated measures. In the triceps brachii (TB), citrate synthase (CS) activity was higher in CON than CLA horses (P = 0.003) but was unaffected by diet in the gluteus medius (GM). Integrative (relative to mg protein) cytochrome c oxidase (CCO) activity was higher in TB than the GM (P < 0.0001), while intrinsic (relative to CS) CCO was lower in the TB than the GM (P = 0.02) and tended to be lower in CON than CLA horses (P = 0.06). Neither CS nor integrative CCO activities were affected by time. In the GM, superoxide dismutase activity tended to increase in CON through week 12 (P = 0.10). Over both muscle groups, glutathione peroxidase activity tended to be higher in CON compared with CLA at week 12 (P = 0.06). Malondialdehyde was higher in the TB than the GM (P = 0.0004) but was unaffected by diet, while serum creatine kinase activity tended to be lower in CLA than CON horses (P = 0.07). These results suggest that CLA supplementation may lead to mitochondrial adaptations and prevent myofiber perturbation in skeletal muscle of young, lightly exercised horses.

Efectos de dos protocolos de entrenamiento sobre el lactato sanguíneo en caballos de paso fino

Objetivo: Comparar los efectos de un protocolo de entrenamiento de resistencia (ER) con un protocolo tradicional (ET) sobre la concentración sanguínea de lactato y CK. Materiales y Métodos: Se aplicaron dos protocolos de entrenamiento durante 6 meses divididos en tres etapas. Se realizaron pruebas de esfuerzo antes de comenzar los protocolos de entrenamiento y al finalizar cada una de las etapas. En cada prueba se tomaron muestras de sangre venosa en reposo, durante el ejercicio y en recuperación para medir el lactato (L), y al inicio y al final para medir la creatin kinasa (CK) e inferir las adaptaciones metabólicas y musculares. Se calculó la diferencia de medianas del lactato basal por medio de la U Mann Whitney y se comparó la diferencia de medias del porcentaje de aclaramiento entre los grupos a través de la T de Students. Resultados: Se encontró una diferencia significativa en el porcentaje de depuración de lactato entre ER y ET. También hubo un aumento significativo de los valores de CK intra-grupos, antes y después de las pruebas, pero manteniéndose dentro de los rangos de referencia. Discusión: El ER aumentó la capacidad de metabolizar el lactato pos-ejercicio en potros con entrenamiento de resistencia, aunque no hubo diferencias entre la máxima producción de L entre el grupo ER y ET. El comportamiento de la CK dentro de los rangos de referencia indica que no hubo daño muscular en los potros de ambos grupos.