Biomedical subjects

M A Lauderdale

Publications and source records attributed to M A Lauderdale.

5 recordsLinked to original sources

PubMed2002

High intensity exercise conditioning increases accumulated oxygen deficit of horses.

High intensity exercise is associated with production of energy by both aerobic and anaerobic metabolism. Conditioning by repeated exercise increases the maximal rate of aerobic metabolism, aerobic capacity, of horses, but whether the maximal amount of energy provided by anaerobic metabolism, anaerobic capacity, can be increased by conditioning of horses is unknown. We, therefore, examined the effects of 10 weeks of regular (4-5 days/week) high intensity (92+/-3 % VO2max) exercise on accumulated oxygen deficit of 8 Standardbred horses that had been confined to box stalls for 12 weeks. Exercise conditioning resulted in increases of 17% in VO2max (P<0.001), 11% in the speed at which VO2max was achieved (P = 0.019) and 9% in the speed at 115% of VO2max (P = 0.003). During a high speed exercise test at 115% VO2max, sprint duration was 25% longer (P = 0.047), oxygen demand was 36% greater (P<0.001), oxygen consumption was 38% greater (P<0.001) and accumulated oxygen deficit was 27% higher (P = 0.040) than values before conditioning. VLa4 was 33% higher (P<0.05) after conditioning. There was no effect of conditioning on blood lactate concentration at the speed producing VO2max or at the end of the high speed exercise test. The rate of increase in muscle lactate concentration was greater (P = 0.006) in horses before conditioning. Muscle glycogen concentrations before exercise were 17% higher (P<0.05) after conditioning. Exercise resulted in nearly identical (P = 0.938) reductions in muscle glycogen concentrations before and after conditioning. There was no detectable effect of conditioning on muscle buffering capacity. These results are consistent with a conditioning-induced increase in both aerobic and anaerobic capacity of horses demonstrating that anaerobic capacity of horses can be increased by an appropriate conditioning programme that includes regular, high intensity exercise. Furthermore, increases in anaerobic capacity are not reflected in blood lactate concentrations measured during intense, exhaustive exercise or during recovery from such exercise.

Aerobiosis↗

PubMed1999

Resting rectal temperature of Vietnamese potbellied pigs.

OBJECTIVE: To determine resting rectal temperatures of Vietnamese potbellied pigs. DESIGN: Prospective clinical trial. ANIMALS: 85 potbellied pigs on a single farm and 27 potbellied pigs examined at a veterinary teaching hospital for routine veterinary care. PROCEDURE: Rectal temperatures of the potbellied pigs on a farm were measured during the morning, afternoon, and evening. Rectal temperatures at the time of initial examination were obtained from medical records for the potbellied pigs examined at the hospital. RESULTS: Mean rectal temperatures for both groups of potbellied pigs were the same. Overall unadjusted mean +/- SD rectal temperature was 37.6 +/- 0.8 C (99.7 +/- 1.5 F; range, 35.1 to 39.6 C [95.2 to 103.3 F]). However, diurnal variation in rectal temperature was found among the farm population of potbellied pigs. After adjustment for age and repeated sampling, rectal temperatures recorded during the morning were found to be significantly lower than temperatures recorded during the afternoon and evening (mean difference, 0.5 and 0.9 C [0.9 and 1.6 F], respectively), and rectal temperatures recorded during the afternoon were found to be significantly lower than temperatures recorded during the evening (mean difference, 0.4 C [0.7 F]). There was a significant inverse linear relationship between age and rectal temperature. CONCLUSIONS AND CLINICAL RELEVANCE: Rectal temperatures of Vietnamese potbellied pigs may be lower than the lower limit of the reference range reported for domestic pigs. Because of diurnal variation in rectal temperatures, it is important to compare temperatures obtained at the same time of day when assessing patients.

Age Factors↗

PubMed1999

Exercise that induces substantial muscle glycogen depletion impairs subsequent anaerobic capacity.

The purpose of this study was to develop a model of muscle glycogen depletion and to study the effect of this model on aerobic and anaerobic capacity of horses. The maximal rate of oxygen consumption (VO2max), maximal accumulated oxygen deficit (MAOD), muscle glycogen concentration and blood lactate concentration of 6 fit Standardbred horses were measured on 3 occasions 7 days apart (Trials 1, 2 and 3). Between Trials 2 and 3, strenuous exercise intended to deplete muscle glycogen was performed by exercising horses on the treadmill on 3 consecutive days. Strenuous exercise resulted in reduction of muscle glycogen concentration by at least 55% (from mean +/- s.e. 155.1 +/- 5.6 mmol/kg, wet weight, before Trial 2 to 55.4 +/- 5.5 mmol/kg before Trial 3; P < 0.05). VO2max was similar in Trials 2 and 3 (140.4 +/- 5.4 ml O2/kg bwt and 141.8 ml +/- 6.2 ml O2/kg, respectively). Run time to fatigue during a single high-speed exercise test (253.9 +/- 33.3 s and 153.8 +/- 16.4 s, P < 0.05), accumulated oxygen deficit (95 +/- 13.2 ml O2/kg and 35 +/- 13.9 ml O2/kg, P < 0.05) and blood lactate concentration at the end of the sprint (17 +/- 1.2 mmol/l and 10.5 +/- 1.1 mmol/l, P < 0.05) were less during Trial 3 than Trial 2. These data suggested that repeated strenuous exercise that causes muscle glycogen depletion results in impairment of anaerobic, but not aerobic, metabolism.

Aerobiosis↗

PubMed1999

Hyperbolic relationship between time-to-fatigue and workload.

The power:time-to-fatigue relationship for high-intensity exercise in man is useful in determining anaerobic work capacity. The purpose of this study was to determine the nature of this relationship in horses. Eight Standardbred horses performed 5 or 6 run-to-fatigue trials on a treadmill. Exercise intensities were chosen to induce fatigue in 30 to 240 s. The order of trials was randomised for each horse, but balanced overall for the first 4 trials. The data for power (independent variable) and time-to-fatigue (dependent variable) were tested for goodness of fit to hyperbolic, linear and exponential equations by nonlinear regression. The best fit to the data was obtained using the hyperbolic relationship t = W'(P- phi PA) where t is the time to fatigue, W' is the anaerobic work capacity, P is the power and phi PA is the critical power value. The values for W' and phi PA were 47,000 +/- 500 J and 2490 +/- 150 watts, respectively. We conclude that the power:time-to-fatigue relationship of horses is hyperbolic and that this relationship may be useful in assessing anaerobic capacity of horses.

Animals↗

PubMed1996

The reliability of aerobic capacity (VO2max) testing in adolescent girls.

Despite the fact that our subjects were naive regarding the test procedures, it appears that aerobic fitness testing using an incremental treadmill protocol is extremely reliable in adolescent girls. In addition, day-to-day variability of VO2max in our subjects averaged less than 5%, which is similar to results obtained with adults (Katch, Sady, & Freedson, 1982). Finally, it was most encouraging to find that a single VO2max test trial resulted in high reliability coefficients. This finding should provide a great deal of confidence to investigators who are performing aerobic fitness tests on large numbers of subjects where multiple testing is neither practical nor cost-effective.

Adolescent↗