Oxygen consumption in adult and aged C57BL/6J mice during acute treadmill exercise of different intensity

Submaximal and maximal oxygen consumption was determined in untrained adult and aged male C57BL/6J mice during treadmill running. Each of 12-month-old (ADULT) and 24-month-old (AGED) male mice was tested on a motor-driven treadmill once at different speeds. VO2 was measured before, during, and after exercise by means of indirect calorimetry in metabolic treadmill chambers. The resting VO2 averaged 3064.67 +/- 87.71 mL/kg/h for ADULT mice and 2472.95 +/- 69.41 mL/kg/h for AGED mice. During exercise, VO2 increased linearly with work intensity (running speed): ADULT mice--from 5908.06 +/- 422.35 mL/kg/h at 3 m/min to 10861.99 +/- 174.03 mL/kg/h at 25 m/min; AGED mice--from 5217.25 +/- 263.26 mL/kg/h at 3 m/min to 7817.32 +/- 290.28 mL/kg/h at 20 m/min. Further increase of the running speed resulted in a decline of VO2 in ADULT and refusal to run in AGED mice. The results of this study demonstrated that in untrained C57BL/6J mice VO2max and maximal exercise capacity declined with age. At the same absolute and relative workloads, VO2 was lower in AGED mice.