Fig. 1. Cost of transport during locomotion. Using an open flow metabolic system, _O2 was measured as a function of running speed on a motorized treadmill. The cold-acclimated animals had significantly higher O₂ utilization as a function of speed such that on average 15% more oxygen was consumed while running at the same speed as thermoneutral controls. Values are means ± S.E.M. at each speed. CS, cold, sedentary; CT, cold, trained; TnS, thermoneutral, sedentary; TnT, thermoneutral, trained.