Author + information
Exercise fatigue is a common phenomenon in athletics and a key factor that restricts an athlete’s performance level. The term “exercise fatigue” refers to a state in which the physiological processes of the body systems cannot continue at a certain level or the organism cannot maintain a predetermined exercise intensity. In exercise physiology, heart rate is an important index used to evaluate exercise load and ethological changes and can accurately reflect the immediate response of physical function to changes in exercise load. There is an important correlation between heart rate and ethological performance. Therefore, in this study, we used changes of ethological indexes and heart rate to classify the exercise stages and set up a fitting formula of exercise fatigue based on the rats’ treadmill exercise data.
The rat exercise fatigue model was established using treadmill exercise with three progressively increasing loads (light to heavy). The rats were subjected to 5-day adaptive treadmill training after being fed for 3 days in the laboratory. A modified Bedford treadmill exercise with a progressively increasing load was used for the exercise fatigue model. There were three total load levels: level I, 8.2 m/min, lasting for 15 min; level II, 15 m/min, lasting for 15 min; level III: 20 m/min, lasting until exhaustion. Changes in ethological indexes and heart rate were observed and recorded by video and heart rate telemetry and statistical methods were used to analyze and test the data.
As expected, during the exercise fatigue process, the relative velocity of the rats decreased; their relative positions gradually shifted backwards; the proportions of sound and electrical stimulation time as well as slippage time gradually increased; and the heart rate increased twice and was then maintained within a certain range. According to the above data, we divided the process into four stages. We also established a fitting formula as follows:
Y = 15.2548 + 0.4346∙xa - 0.1154∙xb + 0.6826∙xc + 0.0044∙xa∙xb - 0.0021∙xb∙xc - 0.0013∙xc∙xa - 0.0023∙xa2 - 0.0016∙xb2 (r2 = 0.906); (xa, xb, and xc represent the cumulative time of sound stimulation, electrical stimulation, and slippage time within 600 s (in seconds); y represents a fatigue score within the 600 s that indicates the degree of exercise fatigue).
We quantified the ethological and heart rate changes in rats during the exercise fatigue process, and determined the proportion of time in its process of the whole practice. In addition, based on the ethological changes and heart rate changes of rats, we divided the exercise fatigue phenomenon into the spontaneous exercise, transition, early fatigue, and later fatigue stages, which laid a foundation for the quantitative evaluation of the ethology in the rat model of exercise fatigue with a progressively increasing load. Meanwhile, the effective ethological indexes were screened and we successfully established a simple nonlinear regression formula to evaluate the fatigue degree of rats with ethological indexes using a mathematical modeling method of polynomial fitting. Hopefully the results shown above will provide an effective reference for the formulation of evaluation standard of exercise fatigue degree to a certain extent(31401018).