RESUMEN
Red blood cell hypervolaemia has been used for diagnosis of overtraining in racehorses, and has been suggested as a mechanism of this cause of loss of racing performance. The effects of overload training (OLT) on the plasma, blood and red cell volumes were investigated in a prospective study in 12 Standardbred horses. Measurements of blood volumes were made after eight and 32 weeks of an exercise training study. Horses were randomly allocated to OLT and control groups (n=6) after 16 weeks of training. Training duration and intensity were increased more rapidly for the OLT group from week 16, until overtraining was diagnosed in week 32. There were no significant effects of OLT on plasma, blood or total red cell volumes between weeks eight and 32. These volumes significantly decreased with time. Maximal haematocrit after exercise was lower (P<0.05) in the OT group in week 32 (0.57+/-0.003% L/L) than in week eight (0.59+/-0.004 L/L). It was concluded that red cell hypervolaemia was not a mechanism for the decrease in capacity for exercise that occurs with overtraining.
Asunto(s)
Volumen Sanguíneo , Eritrocitos/fisiología , Enfermedades de los Caballos/fisiopatología , Condicionamiento Físico Animal , Animales , Hematócrito/veterinaria , Enfermedades de los Caballos/etiología , Caballos , Masculino , Resistencia FísicaRESUMEN
Thirteen Standardbred horses trained intensively for 34 weeks and detrained for 12 weeks to investigate the effects of training, overtraining and detraining on muscle metabolites, buffering capacity and enzyme activities (CS, HAD and LDH). After a standardised exercise test to fatigue at 10 m/s (approximately 100% VO2max), there was significant depletion of [ATP], [PCr] and muscle [glycogen] and accumulation of muscle and plasma [lactate], [NH3] and elevated muscle temperature. After training, associated with increased run time to fatigue (148%), there was reduced depletion of muscle [glycogen] and increased [NH3] and muscle temperature at fatigue. Training resulted in increased muscle buffering capacity (19%) and activities of CS (29%) and HAD (32%) and reduced glycogen utilisation (1.32 mmol/s in week 1 to 0.58 mmol/s in week 32). Plasma [lactate] at fatigue increased with training as opposed to muscle [lactate] implying enhanced ability to remove lactate from muscle. Overtraining resulted in reduced run time and associated effects in overtrained horses. While muscle [glycogen] prior to exercise was lower in overtrained horses, glycogen utilisation/s was not reduced and it may not, therefore, have caused the reduced run time. Prolonged high intensity training caused primarily aerobic adaptations and poor performance associated with overtraining may not be due to metabolic disturbances.
Asunto(s)
Adaptación Fisiológica/fisiología , Caballos/fisiología , Músculo Esquelético/metabolismo , Condicionamiento Físico Animal/fisiología , Esfuerzo Físico/fisiología , 3-Hidroxiacil-CoA Deshidrogenasas/metabolismo , Adenosina Trifosfato/metabolismo , Amoníaco/metabolismo , Animales , Citrato (si)-Sintasa/metabolismo , Creatina/metabolismo , Glucosa-6-Fosfato/metabolismo , Glucógeno/metabolismo , Caballos/metabolismo , L-Lactato Deshidrogenasa/metabolismo , Lactatos/sangre , Masculino , Fatiga Muscular/fisiología , Músculo Esquelético/enzimología , Consumo de Oxígeno/fisiología , Factores de TiempoRESUMEN
Basal concentrations of cortisol (CORT), beta-endorphin (beta EP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600-1000 and 1500-1900 h, and hourly between 1000-1500 h on 3 consecutive days. Treadmill exercise tests comprising 2 min intervals at 30, 50, and 70% VO2max then to fatigue at 100% VO2max were conducted between 1020-1130 h on Day 2. Blood was collected before, during and 15, 30, 60 and 90 min after exercise. Mean (Cav), peak (Cmax) and total (i.e. integrated) (Ctot) concentrations were calculated for CORT, beta EP and GH during the 20 min sampling sessions, and for CORT, beta EP, GH and T between 1000-1300 h on Days 1-3 (incorporating the samples during exercise on Day 2) and 1300-1900 h on Days 1-3. Cav, Cmax and Ctot for CORT, beta EP, GH and T were greater during exercise and recovery than in the same period on Day 1. Cav and Ctot values for plasma T during the 1300-1900 h period were significantly elevated on Day 2 and compared to Day 1 (P < 0.05), but there were no differences between Days 1 and 3 values for these variables. We concluded that plasma T concentration increases in response to maximal exercise in geldings, as does plasma CORT, beta EP and GH. Furthermore, maximal exercise disrupts basal plasma concentrations of CORT, beta EP and GH for up to 24 h and T for 26-32 h post exercise in geldings, therefore reflecting the minimum recovery periods required before evaluating normal, resting levels of these hormones in horses undergoing training.
Asunto(s)
Hormonas/sangre , Caballos/sangre , Condicionamiento Físico Animal , Animales , Prueba de Esfuerzo/veterinaria , Hormona del Crecimiento/sangre , Hidrocortisona/sangre , Masculino , Consumo de Oxígeno , Testosterona/sangre , betaendorfina/sangreRESUMEN
We sought a physiological marker of overtraining in horses, using commonly practised field and laboratory tests to allow early prediction and treatment of the syndrome. Thirteen Standardbred horses were trained as follows: phase 1 (endurance, 7 weeks), phase 2 (high intensity, 9 weeks) and phase 3 (overload, 18 weeks). In phase 3 the horses were divided into 2 groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies and durations than the C group. Overtraining occurred after 31 weeks and was defined as a significant decrease in treadmill run time to fatigue (RT) in response to a standardised exercise test (SET). Variables measured included: feed intake, bodyweight (BWT), resting haematology and plasma biochemistry and treadmill SETs to measure RT. The OLT group had a decrease in BWT after week 28 (P < 0.05) without a reduction in feed intake and a reduction in RT during the SET after 31 weeks. Signs persisted after 2 weeks of a reduced training load confirming overtraining. Haematology and biochemistry failed to detect any markers of overtraining. Although no physiological markers of overtraining were identified, empirical observations revealed that the behaviour of horses in the OLT group was different from those in the C group during the period of overtraining. This study reflects that a model of overtraining has been developed based on measurement of a reduction in performance; however, there were no consistent changes in haematology or serum biochemical values in association with the decrement in performance capacity.
Asunto(s)
Caballos/fisiología , Condicionamiento Físico Animal/fisiología , Animales , Peso Corporal , Ingestión de Energía , Prueba de Esfuerzo/veterinaria , Caballos/sangre , Masculino , Fatiga Muscular , Consumo de Oxígeno , Resistencia FísicaRESUMEN
The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body weight and treadmill run-time-to-fatigue in an incremental velocity test, occurred in the OT group after 32 weeks of training exercise. Peak cortisol concentrations after exercise decreased significantly in the OT group from 320+/-15.6 at week 8 to 245+/-17.0 nmol l(-1) at week 32, and mean cortisol concentrations over a 120-min period after exercise decreased from 258+/-11.7 to 192+/-16.6 nmol l(-1) (P<0.05). Mean and total cortisol and betaEP concentrations in resting horses were not significantly different after over-training. Peak cortisol concentrations after adrenocorticotropin (ACTH) administration were not significantly different in the over-trained group. Dysfunction of the hypothalamo-pituitary-adrenocortical axis occurs in over-trained horses, but this adaptation is not associated with a change in the adrenocortical responsiveness to ACTH.
Asunto(s)
Caballos/fisiología , Hidrocortisona/sangre , Condicionamiento Físico Animal/fisiología , betaendorfina/sangre , Glándulas Suprarrenales/efectos de los fármacos , Glándulas Suprarrenales/fisiología , Hormona Adrenocorticotrópica/farmacología , Animales , Prueba de Esfuerzo , Femenino , Factores de TiempoRESUMEN
Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in response to a standardised exercise test (P<0.05). Relationships between peripheral (skeletal muscle) and whole body (maximum O2 uptake, V.O2, max, treadmill run time) adaptations to training were determined. Prolonged training resulted in significant adaptations in morphological characteristics of skeletal muscle but the adaptations were limited and largely completed by 16 weeks of training. Fibre area increased in all fibres while the number of capillaries per fibre increased and the diffusional index (area per capillary) decreased. Mitochondrial volume density continued to increase throughout 34 weeks of training and paralleled increases in V.O2,max and treadmill run time. Significant correlations were noted between mitochondrial volume and V.O2,max (R=0.71), run time and V.O2,max (R=0.83) and mitochondrial volume and run time (R=0.57). We conclude that many of adaptive responses of muscle fibre area and capillarity occur in the initial training period but that markers of oxidative capacity of muscle indicate progressive increases in aerobic capacity with increases in training load. The lack of differences between C and OLT groups indicated that there may be an upper limit to the ability of training stimulus to evoke skeletal muscle adaptive responses. There was no effect of overtraining or detraining on any of the adaptive responses measured.
Asunto(s)
Adaptación Fisiológica/fisiología , Caballos/fisiología , Músculo Esquelético/fisiología , Condicionamiento Físico Animal , Animales , Masculino , Mitocondrias Musculares/ultraestructura , Fibras Musculares de Contracción Rápida/ultraestructura , Fibras Musculares de Contracción Lenta/ultraestructura , Músculo Esquelético/ultraestructura , Consumo de Oxígeno , Factores de TiempoRESUMEN
Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight (P < 0.05). From pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1, maximal O2 uptake (VO2max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group, VO2max was 29% higher (151 +/- 2 ml.kg-1.min-1 in both C and OLT groups) than pretraining values. There was no significant reduction in VO2max until after 6 wk detraining when VO2max was 137 +/- 2 ml.kg-1.min-1. By 12 wk detraining, mean VO2max was 134 +/- 2 ml.kg-1.min-1, still 15% above pretraining values. When overtraining developed, VO2max was not different between C and OLT groups, but maximal values for CO2 production (147 vs. 159 ml.kg-1.min-1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease in VO2max and, after prolonged training, decreases in VO2max occurred slowly during detraining.
Asunto(s)
Consumo de Oxígeno/fisiología , Condicionamiento Físico Animal , Animales , Peso Corporal/fisiología , Prueba de Esfuerzo , Caballos , Cinética , Masculino , Resistencia Física/fisiología , Pruebas de Función Respiratoria , Factores de TiempoRESUMEN
The aim of this study was to investigate correlations between lactate concentrations in equine whole blood and plasma measured with Accusport1 and Yellow Springs Instruments (YSI2) (2300) methods. The effect of packed cell volume (PCV) on the accuracy of Accusport was also investigated. Blood samples were collected from Thoroughbred horses at 5-10 min intervals after a treadmill exercise test. Blood was added to NaEDTA (for PCV measurement) and to 2 tubes containing lithium heparin anticoagulant (for lactate assays). At concentrations greater than 10 mmol/l, Accusport1 greatly underestimated the blood lactate concentration. Accusport1 also underestimated blood lactate concentration when PCV were greater than 53%. Accusport1 accurately measured plasma lactate concentration in the range 0.8-20 mmol/l.
Asunto(s)
Caballos/sangre , Lactatos/sangre , Condicionamiento Físico Animal/fisiología , Animales , Conservación de la Sangre , Prueba de Esfuerzo/veterinaria , Hematócrito/veterinaria , Modelos Lineales , Reproducibilidad de los ResultadosRESUMEN
A retrospective study of 46 horses with retropharyngeal lymph node (RPLN) infection presented to the Rural Veterinary Centre between 1977 and 1992 was undertaken. Horses aged less than one year were most commonly represented (46%). Thirty-nine percent of cases had been exposed to horses with confirmed or suspected strangles (Streptococcus equi subsp equi infection) within the previous 8 weeks. Most frequent signs were unilateral or bilateral swelling of the throat region (65%), respiratory stertor/dyspnoea (35%), purulent nasal discharge (20%), inappetence and signs of depression (15%), and dysphagia (9%). All horses had a soft tissue density in the retropharyngeal region on radiographs. Rhinopharyngoscopy, ultrasonography, haematology as well as cytological and microbial analysis of material aspirated from the soft tissue swelling facilitated diagnosis in some horses. Fifteen horses (33%) were treated with procaine penicillin intramuscularly for 4 to 7 days followed by oral trimethoprim-sulphadimidine for 7 to 14 days. Non-steroidal anti-inflammatory drugs were administered to 6 horses. Four required tracheostomy for severe respiratory distress. The 15 horses treated medically responded to treatment and were discharged from hospital. Three horses (6%) with mild signs received no treatment and recovered uneventfully. Twenty-eight horses (61%) underwent general anaesthesia and surgical drainage of a RPLN abscess. Nineteen received procaine penicillin G for 4 to 7 days. Four of the nine horses that did not receive antibiotic treatment after surgery required further surgical drainage 10 days to 7 weeks after the initial surgery. Limited follow-up information was available for 37 horses.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Enfermedades de los Caballos/terapia , Ganglios Linfáticos/microbiología , Linfadenitis/veterinaria , Absceso Retrofaríngeo/veterinaria , Infecciones Estreptocócicas/veterinaria , Streptococcus equi/aislamiento & purificación , Administración Oral , Animales , Drenaje/veterinaria , Quimioterapia Combinada , Femenino , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/microbiología , Caballos , Inyecciones Intramusculares/veterinaria , Linfadenitis/diagnóstico , Linfadenitis/microbiología , Linfadenitis/terapia , Masculino , Penicilinas/uso terapéutico , Faringe , Absceso Retrofaríngeo/diagnóstico , Absceso Retrofaríngeo/microbiología , Absceso Retrofaríngeo/terapia , Estudios Retrospectivos , Infecciones Estreptocócicas/diagnóstico , Infecciones Estreptocócicas/microbiología , Infecciones Estreptocócicas/terapia , Sulfametazina/uso terapéutico , Trimetoprim/uso terapéuticoRESUMEN
Peritonitis attributable to Actinobacillus equuli was diagnosed in 15 horses examined at the veterinary center between 1982 and 1992. In 13 horses, historical findings included acute onset of mild to severe signs of abdominal pain, lethargy, and inappetence. Two other horses had a history of weight loss for 3 to 6 weeks prior to examination. Diagnosis was based on the physical signs and laboratory findings, including results of peritoneal fluid analysis (gross characteristics, total protein, total and differential nucleated cell counts, and morphologic findings) and culture of A equuli. Actinobacillus equuli was consistently susceptible in vitro to penicillin, trimethoprim/sulfadiazine, and aminoglycosides. All horses in the study had marked clinical improvement within 24 to 48 hours of commencing antibiotic and supportive treatment. Antibiotic treatment was continued for variable periods, depending on the horse, but ranged from 5 to 21 days. In 11 horses for which follow-up information was available, long-term response to treatment was excellent, with horses returning to original activity.