Antônio Raphael Teixeira-Neto

Blood lactate threshold reflects glucose responses in horses submitted to incremental exercise test

Determinou-se, em equinos, o efeito do treinamento sobre as concentracoes sanguineas de lactato e plasmaticas de glicose durante exercicio de intensidade progressiva em esteira rolante. Demonstrou-se que o treinamento aerobico causou diminuicao da concentracao maxima de lactato e que o limiar de lactato corresponde ao ponto de inflexao da curva de glicose plasmatica, confirmando esse parâmetro como indicador da capacidade aerobica de cavalos.

Alterations in muscular enzymes of horses competing long-distance endurance rides under tropical climate

This study tried to monitor the alterations of muscle enzymes activity - creatinokinase (CK), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) - in a group of horses that participated of 70 and 100km distance rides in five competitions of an annual endurance championship under tropical climate. Pre ride levels (U/l) were 245.13±9.84 for CK, 496.61±14.76 for LDH, and 328.95±8.65 for AST. When compared to these levels, the results revealed a significant decrease in all enzymes activities in the first moment of the rides. Peak levels, significantly different, were reached, immediately after rides by CK (413.591±50.75); 24 hours post rides by LDH (628.61±33.30); and 48 hours after rides by AST (389.89±16.96). Monitoring of recovery period revealed different behavior among enzymes activities with CK values returning to pre ride values (279.61±23.05) 24 hours post rides, while LDH and AST values returned to pre ride values (505.25±33.78 and 359.35±24.90, respectively) 72 hours post rides. These data revealed different alterations in concentration of muscular enzymes in endurance horses directly related to the duration of the effort.

Alterações hematológicas e cardíacas em cavalos Árabes submetidos ao teste de esforço crescente em esteira rolante

Estudaram-se alteracoes na frequencia cardiaca e variaveis hematologicas de equinos Puro Sangue Arabe (PSA), submetidos a exercicio intenso em esteira rolante sob condicoes tropicais. Para tanto, 24 equinos, treinados, realizaram exercicio teste de intensidade crescente e amostras de sangue foram obtidas durante as etapas de esforco 4; 5; 6; 7; 8; 9 e 10 m.s-1, com 10% de inclinacao. As colheitas de sangue foram realizadas 15 segundos antes do termino de cada etapa. A frequencia cardiaca foi obtida em cada etapa do exercicio teste. Com as amostras de sangue foram obtidos, hematocrito, hemacias, hemoglobina e leucocitos totais. Foram calculados indices hematimetricos absolutos, volume corpuscular medio (VCM), hemoglobina corpuscular media (HCM) e a concentracao de hemoglobina corpuscular media (CHCM). Os resultados mostram que houve variacao significativa (p < 0,05), a partir do repouso, entre os valores medios da frequencia cardiaca e das variaveis hematimetricas. Destaque para o VCM e HCM que aumentaram significativamente (p < 0,05) na etapa de esforco maximo (10m/s) demonstrando haver anisocitose durante o exercicio intenso. Desta forma, o grau das alteracoes destas variaveis fisiologicas esta relacionado com a intensidade e duracao do exercicio teste.

Reposição eletrolítica sobre variáveis fisiológicas de cavalos em provas de enduro de 30 e 60km

The objective of this work was to compare physiologic parameters of a group of trained horses submitted to 30 and 60km endurance exercises with an average speed of 10 and 15km/h, respectively. One of the groups was treated, orally, with an hipertonic electrolyte paste before, during and after the task. The results revealed that the administration of the electrolyte paste did not show any deleterious effect on the animals, and also suggest that the supplementation with an electrolyte source should contribute for the performance of horses submitted to prolonged efforts.

Long-term creatine supplementation improves the aerobic capacity of horses

The aim of the present study was to investigate the effect of long-term oral supplementation of creatine on the physiological responses to aerobic training. Twelve purebred Arabian horses were submitted to aerobic training for 90 days, with and without creatine supplementation which consisted of the daily administration of 75g of creatine monohydrate mixed into the ration for 90 days of training. Physical conditioning was conducted on a high performance treadmill and training intensity was stipulated by calculating the V4 (velocity at which blood lactate reaches 4mmol L-1) determined monthly for each animal. The individual intensity of physical force at 80% of aerobic threshold was established. An incremental exercise test was used to set the individual V4. After a warm up period of 4 min at 4m s-1, the speed was increased at 2min intervals to 6, 8 and 10m s-1. The blood samples were collected 15s before the end of each step to determine the concentration of lactate, packed cell volume, hemoglobin and red cell values. The results demonstrated a significant increase (P<0.05) in V4 in the groups that received creatine supplementation for 60 days or more when compared to the animals without creatine supplememntation. The other hematological variables were similar to all groups. The results showed that the prolonged creatine supplementation may have a beneficial al effect on the equine athletic performance.

Effects of intravenous administration of caffeine on physiologic variables in exercising horses

OBJECTIVE To investigate the effect of acute administration of caffeine on the athletic performance of Arabian horses. ANIMALS 12 healthy adult Arabian horses that were trained for exercise on a treadmill. PROCEDURES By use of a crossover study design, horses received each of the following treatments: IV administration of caffeine (5 mg/kg) and IV administration of approximately the same volume of saline (0.9% NaCl) solution. Order of treatment was randomized, and there was a 10-day interval between treatments. Thirty minutes after treatments, horses underwent an incremental exercise test (IET) on a treadmill. Blood samples were collected 15 seconds before the end of each velocity step of the IET for determination of blood lactate, blood glucose, plasma cortisol, and plasma insulin concentrations. Heart rate and hematologic variables were also analyzed. RESULTS Velocities achieved when heart rates were 180 and 200 beats/min increased significantly in caffeine-treated horses, compared with control horses. Velocities corresponding to blood lactate concentrations of 4 and 2 mmol/L decreased significantly in caffeine-treated horses, compared with control horses. In comparison between groups, insulinemia was greater in control horses and glycemia was greater in caffeine-treated horses. Plasma cortisol concentration was significantly lowered by treatment with caffeine. CONCLUSIONS AND CLINICAL RELEVANCE IV administration of caffeine at 5 mg/kg improved the performance of Arabian horses during intense exercise of short duration and diminished the oxidative metabolism of glucose.

Exercise intensity, but not electrolyte reposition, alters plasmatic cortisol and glucose levels of horses submitted to 30 and 60km distance endurance rides

This study was aimed at comparing cortisol and glucose plasmatic levels in a group of trained horses submitted to 30 and 60km endurance exercises, at the average speed of 10 and 15km h-1, respectively. The horses were randomly divided in two groups, one treated, orally, with a hypertonic electrolyte paste before, during and after the tasks and the other used as control. Cortisol data revealed significant increase in the first moment when the intensity of the exercise was higher (15km/h) or with the prolongation of it (30km long), in the second moment to all groups. Glucose data remained constant during 30km ride; however after 20km distance, in 60km ride, it revealed a significant increase in control group, returning to basal levels in the subsequent moment. Electrolyte replenishment has its importance in the maintenance of the hidroelectrolyte and acid-base status and, in this study, may have contributed to the homeostasis of glucose levels.