Small-animal ergometer.

A continuous vertical ladder ergometer for small animals has been developed. This device, operating at a (variable) downward velocity, obliges the subject animal to climb continuously, thus imposing a steady quantifiable work rate or power output. The power output of the animal is given simply by P = W X V X 9.80 X 10(-3) sin theta, where P is the power output in watts, W the animals' weight in grams, V the ladder velocity in meters per second, and theta the angle between horizontal and the ladder surface. Wistar rats have been readily taught to climb on the ergometer and demonstrate high levels of physical effort with no injuries. Rats of 350 g body wt are able to climb at 0.25 m/s for period of 15 min. The maximal power output of rats varies between 0.5 and 1.1 W. The ergometer design is compatible with conditioning and exercise programs for small animals as well as with quantitative measurements of power output and physiological parameters such as heart rate and gas exchange.