A novel long term short interval physical activity regime improves body composition in mice

Abstract

Background: Exercise training (ET) and physical activity (PA) offer obvious health benefits in regular participants. In pre-clinical animal models, treadmills and running wheels are the models of choice for intervention studies using ET and PA. However, the frequency and duration necessary for positive effects on health are not completely understood. We investigated the impact of short duration voluntary wheel running on body composition in FVB × C57BL/6 F1 hybrid mice over 22 weeks. Mice were randomized and given access to voluntary wheel running (N = 6) or locked wheels (N = 5) for 1 hour per night during the dark cycle, 5 days per week.

Finding: Average weekly running distance was generally cyclic in nature over the 22 weeks but did not change significantly from week to week, except for a difference between week 3 and week 9 (P = 0.05). Daily running distances ranged from 0.78 km to 1.45 km. Compared with non-runners, runners demonstrated significantly lower relative fat mass (9.98 ± 0.56% vs. 14.91 ± 1.47%, P = 0.0067) and significantly higher relative lean mass (79.18 ± 0.65% vs. 75.41 ± 1.28%, P = 0.019). No differences were observed with respect to glucose metabolism.

Conclusion: Voluntary wheel running for one hour a day five days a week over a five month period improved body composition in young adult mice. This repetitive short interval exercise regime should be a useful model to investigate the effects of structured moderate intensity physical activity on physiological performance and chronic disease conditions in mice.

Figure 1

The average weekly distance ran was generally similar during the course of the study, and body weights between runners and non-runners did not diverge until after 4 months. A. There was no significant variation in mean weekly distance ran, except for the 3rd week, which was significantly greater compared with the 9th week. B. Body weights of both runners and non-runners were measured weekly during the 5 month running period. A trend but non-significant change in body weights between the two groups was first observed during the last week of the fourth month (P = 0.06), followed by a significant change the first week of the fifth month (P = 0.02).

Figure 2

Voluntary wheel running resulted in decreased body weight. A. Baseline body weights of runners and non-runners were measured before the study began and no significant differences were observed (P = 0.34). B. Runners demonstrated decreased body weight at the end of the study, compared with non-runners (P = 0.013).

Figure 3

A Regular physical activity reduced adiposity and enhanced lean body mass. A. After 5 months of running, runners demonstrated reduced relative fat mass, compared with non-runners (P = 0.0067). B. Runners also exhibited increased lean body mass compared with non-runners (P = 0.019).