Frequency and duration of interval training programs and changes in aerobic power.

This study was designed to ascertain whether 7- and 13-wk interval training programs with training frequencies of 2 days/wk would produce improvement in maximal aerobic power (VO2max) comparable to that obtained from 7- and 13-wk programs of the same intensity consisting of 4 training days/wk. Sixty-nine young healthy college males were used as subjects. After training, there was a significant increase in VO2max (bicycle ergometer, open-circuit spirometry) that was independent of both training frequency and duration. However, there was a trend for greater gains after 13 wk. Maximal heart rate (direct lead ECG) was significantly decreased following training, being independent of both training frequency and duration. Submaximal VO2 did not change with training but submaximal heart rate decreased significantly with greater decreases the more frequent and longer the training. Within the limitations of this study, these results indicate that: 1) maximal stroke volume and/or maximal avO2 difference, principle determinants of VO2max, are not dependent on training frequency nor training duration, and 2) one benefit of more frequent and longer duration interval training is less circulatory stress as evidenced by decreased heart rate, during submaximal exercise.