Background

Exercise causes significant alterations in rectal temperature and heart rate. Previous studies have investigated such changes in Labradors at rest and following exercise. However, to the best of the authors' knowledge, these parameters have not been evaluated during exercise. The aim of this study was to develop a standardised maximal exercise test that will take into account the level of fitness of individual dogs and will provide reference data for heart rate (HR), vasovagal tonus index (VVTI) and rectal temperature in healthy Labradors during maximal exercise.

Methods and Materials

Thirteen healthy Labrador retrievers were enrolled in the study; 6 dogs (3 males and six females) were classified as "athletic" (A) and 7 (3 males and 4 females) as "non-athletic" (N). All subjects underwent a multi-stage exercise test (6-minute steps at incremental speeds from 5 m/h to either 10 m/h or until exhaustion) graded for level of fitness (A=15% slope; N=5% slope). Subjects' ECGs were recorded via radio-telemetry throughout the entire test and rectal temperature was measured at rest and at the end of each step of exercise. HR and VVTI during the resting period and in the first and last 20 seconds of each step were measured retrospectively. Data were analysed by one-way ANOVA for repeated measures and Bonferroni test. Correlations between HR and VVTI and between intensity of exercise and rectal temperature were assessed using the Spearman test.

Results

The measure of reliability showed a good reproducibility of the test (CV% for HR = 8.1; VVTI = 5.5; rectal temperature = 0.7). Results of mean HR, VVTI and rectal temperature during exercise are reported in table 1. HR and VVTI showed a strong negative correlation (r= -0.81; 95% CI -0.88 to -0.72). A strong positive correlation was also found between intensity of exercise and rectal temperature (r= 0.77; 95% CI -0.66 to -0.84).

Conclusions

The proposed exercise test shows high repeatability for all the measured parameters (HR, VVTI, rectal temperature) and provides a practical method for precise evaluation of important physiologic parameters during maximal exercise in Labradors.

Table 1. Mean HR, VVTI and rectal temperature measured in athletic (A) and non-athletic (N) Labradors during exercise.

"a" indicates significant difference when compared with the same phase of the preceding exercise step (p<0.05); "b" indicates significant difference when compared with the preceding measurement (p<0.05).