Variations in running activity in exercised mice.

<p>Mice were adapted to exercise and solitary living for one week, followed by voluntary wheel running for four weeks. (<b>A</b>) Running distance for individual mice used in the study in the last four weeks. High runners (black) run more than 10.2 km/day, mid-runners (gray), between 7.8–10.2 km/day, and low runners (white), less than 7.8 km/day. Average running distance over the four weeks of exercise was 9.0±0.3 km/day. (<b>B</b>) Time spent on running activity (hrs/day) and (<b>C</b>) speed of running. Running time and speed increased gradually during the adaptation period, then remained steady for four weeks of exercise. Average time was 9.6±0.2 hrs/day and average speed was 0.9±0.0 km/hr. Values are mean ± SEM; n = 55.