Computational NeuroscienceValidation of a method to measure total spontaneous physical activity of sedentary and voluntary running mice

- Novel method for measuring spontaneous activity of mice was developed.
- The system is valid for measuring activity of mice with or without a running wheel.
- Running wheels triple the total spontaneous activity of mice.
- Running wheels increase both the intensity and time of activity.

BackgroundRunning wheels are commonly used to stimulate physical activity of mice. To control the effects of physical activity on study results, it is important to measure the total activity (all movements) of both sedentary and running wheel stimulated mice.New methodBecause there was a lack of a validated system, we built a force-plate based system specifically for this purpose. The validity of the system and its variables (activity index, activity time and distance) were tested in calibration measurements and in situ by measuring the activity of eight mice both with and without running wheels. Four mice served as sedentary controls. Activity index adds changes in vertical reaction forces induced by moving mice. The system records simultaneously all the activity, thus the wheel running is not distinguished from other activity.ResultsThere were very strong associations between measured activity variables and their true values (R2 = 1, p < 0.01). The mean differences to true values were: activity index −9.7% (95% limits of agreement (LOA), −28.7 to 9.4%), activity time +0.9% (LOA, −1.3 to 3.0%) and distance +0.7% (LOA, −4.7 to 6.1%). The running wheels increased activity index 211 ± 40% (mean ± SE), activity time 39 ± 3% and activity intensity 94 ± 16%. Activity index (R2 = 0.982, p < 0.01), activity time (R2 = 0.618, p < 0.01) and intensity (R2 = 0.920, p < 0.01) were positively associated with running distance.Comparison with existing methodsTo our knowledge, this is the first method properly validated for this purpose.ConclusionsThe system is valid for the quantitation of total physical activity of mice housed in cages with or without running wheels.