Is intermittent exposure to hypobaric hypoxia a reliable method to enhance aerobic capacity in rats?

Objective

To verify that intermittent hypobaric hypoxia (IHH) exposure in rats can elicit an enhancement in aerobic exercise capacity.

Materials and methods

25 male rats were randomly divided in 2 groups: Control (n=12) maintained at sea level and Acclimated (n=13) exposed to IHH program (5000m simulated altitude at Pb=54 KPa for 4 hours/day, 5 days/week along 22 days). Rats were previously habituated to exercise in a treadmill. An incremental maximal test was performed at the beginning (Pre), the end (Post), and ten (10dPost) and twenty (20dPost) days after the end of the acclimation program in both control and hypoxic groups. These were performed in a metabolic treadmill (initial speed 16cm/s and tilt 15º). Slope was constant along the test but speed was increased in 2 cm/s every 2 minutes until exhaustion of the animal. VO2 was monitored during exercise and recovery.

Results and conclusions

No significant differences were found in VO2max between acclimated and control animals. However, a lower VO2 for a same workload was observed (17-27%), with a significant right shift in the VO2/workload curve in acclimated animals as compared to control. Exercise time significantly increased in Post (11.20%), 10dPost (22.10%) y 20dPost (15.20%), whereas no change were observed in control animals. Recovery time as indicated by VO2 only significantly decreased (about 6 minutes) in Post 10d. These data can be interpreted as a clear increase in the aerobic capacity of acclimated animals. Further studies must been developed to confirm our hypothesis, and also to test the combination of exercise training and IHH.