Monitoring exercise intensity during long‐term endurance exercise training in aging rats

Chronic exercise is known to counter a number of deleterious effects of aging. There are a number of difficulties associated with long term exercise training in aged animals, such as matching appropriate training intensities to the declining exercise capacity as animals age. But there is little quantitative information available regarding exercise capacity in very old rats. We conducted a 1 year endurance exercise study in male FBN rats, starting with rats at age 24 mo and continuing daily until 36 mo of age. Rats were divided into 3 groups; high intensity (H), and moderate intensity treadmill exercise (M), and sedentary (S). M and H animals trained at 13 m/min for 30 min/day, with the H group at 5% incline. We monitored exercise capacity and its response to training by measurements of VO 2 max and blood lactate threshold (LT) every 3 mo throughout the training. The relative training intensity for the M animals, expressed by training speed as a percent of the running speed at LT, rose significantly as the animals aged (88% at 27 mo, 104% at 30 mo, 142% at 33 mo, and 325% at 36 mo). Similar results were seen with the H animals and when using VO 2 max as a measure of exercise capacity. These results indicate that even in trained animals exercise capacity declines significantly in advanced age and stress the importance of measuring exercise ability at various time points throughout a prolonged training program. Supported by: NIH AG030423