Genetic influence on daily wheel running activity level

This project was designed to determine the genetic (between-strain) and environmental (within-strain) variance in daily running wheel activity level in inbred mice. Five male and five female mice, 9.7 - 15.3 wk old, from each of 13 strains (A/J, AKR/J, BALB/cJ, C3H/HeJ, C57Bl/6J, C57L/J, C3Heb/FeJ, CBA/J, DBA/2J, SWR/J, MRL/MpJ, SPRET/Ei, and CAST/Ei) as well as five female NZB/ BinJ mice were housed individually. A running wheel in each cage was interfaced with a magnetic sensor to measure total daily distance and exercise time for each animal every 24 h for 21 consecutive days ( 3 wk). Average daily distance ( km), duration (min), and velocity (m/min) for each strain was then calculated. Significant interstrain differences in average daily distance ( P < 0.001), average daily exercise duration ( P < 0.0001), and average daily exercise velocity ( P < 0.0001) were found, with C57L/J mice running farther and faster than the other strains. Sex was a significant factor in daily running wheel activity, with female mice running an average of 20% farther ( P = 0.01) and 38% faster ( P < 0.0001) than male mice. The male mice ran 15% longer duration on a daily basis ( P = 0.0091). Weight was only associated with exercise velocity in the female mice, but this relationship was not significant when subdivided by strain. Broadsense heritability estimates on the physical activity differed by sex ( for distance, male 31 - 48% and female 12 - 22%; for duration, male 44 - 61% and female 12 - 21%; for velocity, male 49 - 66% and female 44 - 61%). In conclusion, these data indicate that daily running wheel activity level in mice is significantly affected by genetic background and sex.