Dose–response relationship of cardiorespiratory fitness adaptation to controlled endurance training in sedentary older adults

The purpose of this investigation was to identify a quantitative dose–response relationship for enhancing maximal oxygen consumption (VO_2max) in healthy sedentary older adults after controlled endurance training.

This meta-analysis of controlled clinical trials included 1257 exercisers and 845 controls with a mean age of 67.45 ± 5.25 years. Effect sizes were calculated for training-induced VO_2max changes. Different training regimens were analyzed and compared. The weighted net change of the mean VO_2max values showed a significant increase of 3.78 ml/kg per min (95% confidence interval = 3.29 to 4.27; p < 0.0001) in response to aerobic training. Interstudy differences in VO_2max changes were significantly related to exercise intensity, and explained approximately 11% of the variance of the VO_2max responses. VO_2max improved significantly at 35%–50% heart rate reserve (HRR) and continued improving at a greater rate with increasing “dose”. The largest VO_2max-improvement adaptation was achieved with a mean intensity of 66%–73% HRR. The magnitudes of the VO_2max adaptation are identical to exercise at 57%–65% HRR and at 75%–80% HRR. Higher intensity doses more than 75–80% HRR did not lead to greater enhancement of VO_2max improvements but, conversely, resulted in large declines.

Our data provide quantitative insight into the magnitude of VO_2max alterations as affected by exercise intensity, duration, frequency, and program length. The shapes of the dose–response curves are not simply linear, but with many similar trends and noteworthy characteristics. Aerobic training at a mean intensity of 66%–73% HRR with 40–50 min per session for 3–4 day/week for 30–40 weeks appears to be effective and optimal for maximum cardiorespiratory benefits in healthy sedentary older adults.