Predicting submaximal oxygen consumption during treadmill running in mice

Abstract

Treadmill exercise is the most common form of exercise used in studies involving laboratory rodents. However, oxygen consumption [Formula: see text] is not usually monitored since the measurement of this parameter is particularly difficult in small, exercising animals. The purpose of this study was to develop a regression equation for predicting submaximal [Formula: see text] in mice during treadmill running. Twenty female mice of three strains were tested, in an Oxyscan metabolic treadmill, on different days at running speeds of 10, 13, 15, 17, and 20 m/min at a 0% grade. Each mouse was placed in the treadmill chamber for a 10-min period before running commenced. Running speed was increased in 2-min intervals by 5 m/min until the assigned speed was reached. Each mouse then ran for 10 min to reach steady state, followed by another 20 min at the steady-state plateau. During this period a 30-s expired gas sample was collected every minute. Gas samples were analyzed for O2 and CO2, using an Oxyscan gas analyzer. Trials were conducted during the nocturnal phase of the animals' photoperiod, and running speeds were assigned randomly to minimize order effects. This approach provided highly reliable measures of oxygen consumption (r = 0.96). By using the running speeds (10–20 m/min) and the animal's body weight it was possible to predict the submaximal oxygen consumption (mL/min) during running with a high degree of accuracy (i.e., R2 = 0.85). In an independent group of animals (n = 14) we compared the predicted [Formula: see text] with the measured [Formula: see text]. This yielded a good correlation coefficient (r = 0.79) and a low prediction error (+2.4 ± 2.9%). This study demonstrated that it is possible to predict the submaximal oxygen consumption of laboratory mice during exercise, with an acceptable prediction error, from relatively simple measures (running speed and body weight). In addition, it was also possible to predict accurately the relative intensity of exercise [Formula: see text] using the animal's running speed on the treadmill (r = 0.999).Key words: submaximal [Formula: see text], treadmill exercise, regression equation, rodents.