REAL-TIME MEASUREMENT OF THE CONTRIBUTION OF THE MUSCULAR-ACTIVITY TOTHE METABOLIC-RATE IN FREELY MOVING RATS

A new real-time ergometric system, ERGORAT, for measuring the energy e xpenditure due to muscular activity of small mammals is described. The method is based on measuring the vibrations induced by a freely movin g rat to a platform on which it is living. Six accelerometers placed o n the platform detect all the vibrations produced by the rat. The co-o rdinates of the centre of mass of the animal are located by an optoele ctronic device. This location and the six accelerations are fed to a m icroprocessor-based data acquisition and processing system. Using a La grangian dynamic model, the values of the mechanical energy transferre d to the platform are computed every second. ERGORAT is used as part o f an experimental setup allowing the measurement of the energetic bala nce of lean and obese rats. The results clearly show that the increase in metabolic rate of obese rats during cold exposure can be entirely explained by the cost of their increase in locomotor activity, whereas for lean rats, this cost accounts for only 41.5 per cent of their met abolic increase, the remaining being the contribution of their active brown adipose tissue.