Document Type


Publication Date




Publication Title

Medicine and Science in Sports and Exercise








Purpose: The American College of Sports Medicine has stated that aerobic: training needs to occur at a minimum threshold intensity of 50% VO2max for most healthy adults and at 40% VO2max for those with a very low initial fitness. Recently, the concept of VO2 reserve (% VO2R, i.e., a percentage of the difference between maximum and resting VO2 has been introduced for prescribing exercise intensity, This analysis was designed to determine the threshold intensity for improving cardiorespiratory fitness expressed as %VO2R units. Methods: Previous studies in healthy subjects (N = 18) that evaluated the result, of training at low-to-moderate intensities (i.e., less than or equal to 60% VO2max) were identified. The original studies described the intensity of exercise variously as %VO2max, %HRR, %HRmax or as a specific HR value. In each case, the intensity was translated into %VO2R units. Results: Exercise training intensities below approximately 45% VO2R were consistently ineffective at increasing VO2max in studies that used subjects with mean initial VO2max values > 40 mL.min-1 kg-1. In studies using subjects with mean initial VO2max values < 40, no intensity A as found to be ineffective. For this latter group of subjects, the lowest intensities examined A ere approximately 30% VO2R. Conclusion: Although evidence for a threshold intensity was not strong, this analysis of training studies support the use of 45% VO2R as a minimal effective training intensity for higher fit subjects and 30% VO2R for lower fit subjects.


Web of Science: "Free full-text from publisher -- gold open access."

Copyright © 2002 by the American College of Sports Medicine

Original Publication Citation

Swain, D. P., & Franklin, B. A. (2002). VO2 reserve and the minimal intensity for improving cardiorespiratory fitness. Medicine and Science in Sports and Exercise, 34(1), 152-157. doi:10.1097/00005768-200201000-00023