A prospective evaluation of non-interval- and interval-based exercise training progressions in rodents.

Non-interval and interval training progressions were used to determine ( i) the mean rate at which treadmill speed could be incremented daily using a non-interval training progression to train rats to run continuously at different intensities and ( ii) the number of training days required for rats to run continuously at different exercise intensities with non-interval- and interval-based training progressions to establish methods of progressive overload for rodent exercise training studies. Rats were randomly assigned to mild-intensity ( n = 5, 20 m·min-1, 5% grade), moderate-intensity ( n = 5, 30 m·min-1, 5% grade), and heavy-intensity non-interval groups ( n = 5, 40 m·min-1, 5% grade) or a heavy-intensity interval ( n = 5, 40 m·min-1, 5% grade) group and ran 5 days·week-1 for 6 weeks. Non-interval training involved a daily increase of treadmill speed, whereas interval training involved a daily increase of interval time, until the animal could run continuously at a prescribed intensity. In mild-, moderate-, and heavy-intensity non-interval-trained rats, treadmill speed was increased by 0.6 ± 0.7 m·min-1·day-1, 0.6 ± 0.2 m·min-1·day-1, and 0.8 ± 0.1 m·min-1·day-1, respectively. Target training intensity and duration were obtained following 0.4 ± 0.5 days, 17 ± 3 days, and 23 ± 3 training days ( p < 0.05) in mild-, moderate-, and heavy-intensity groups, respectively. In contrast, interval-trained rodents required 11 ± 1 training days. These data demonstrate that rodents will tolerate an increase in treadmill speed of ∼0.7 ± 0.1 m·min-1·day-1 and that this progression enables rats to run continuously at moderate and heavy intensities with 3-4 weeks of progressive overload. Interval training significantly reduces the number of training days required to attain a target intensity. [ABSTRACT FROM AUTHOR]