WILMORE, JACK H., JAMES A. DAVIS, ROXANA S. O'BRIEN, PAUL A. VODAK, GLEN R. WALDER, and EZRA A. AMSTERDAM. Physiological alterations consequent to 20-week conditioning programs of bicycling, tennis, and jogging.Med. Set. Sports Exercise, Vol. 12, No. 1, pp. 1–8, 1980. This study investigated the efficacy of free-wheel bicycling and tennis as endurance conditioning activities. The subjects were 38 sedentary, middle-aged male volunteers, who were randomly assigned to one of four groups: bicycling (N=9); tennis (N = 10); jogging (N = 9); and control (N = 10). Each subject was tested twice at the beginning and once at the conclusion of the 20-week study. Each training group exercised 3 days/week for 30 min/day, following 15 minutes of formal warm-up. The bicycling, tennis and jogging groups had an average attendance of 3.0, 2.7, and 2.8 days/week, and maintained their exercise intensity at 83, 65, and 85% of HR max respectively. Using analysis of covariance, only the bicycle and jogging groups significantly increased treadmill Vo2max (14.8 and 13.3% respectively) even though there was a 5.7% improvement for the tennis group. The control group did not change. Vo2max was also assessed on a cycle ergometer for the bicycle and jogging groups, and increased significantly by 17.4 and 14.0% respectively, thus, specificity of the training response was not identified. VEmax increased significantly in the bicycling and jogging groups, while resting blood pressure did not change for any of the four groups. Relative to body composition, only the bicycle group increased lean body weight. The bicycle and jogging groups had substantial decreases in relative and absolute body fat, but these changes were not statistically significant due to changes in the control group. In conclusion, bicycling and jogging appear to provide comparable physiological benefits. Tennis produced only modest increases in endurance capacity but, since the duration of each training session was only 30 to 50% of a typical time period for playing tennis, the results of the present study may, in fact, be underestimating changes in Vo2max due to the interaction of intensity and duration in facilitating change.