The first phase of this study sought to determine: (1) the effects of exercise intensity when total work loads were similar; (2) the effects of duration when intensities were controlled; and (3) a possible intensity duration interaction. Subjects were 36 male college students. Frequency of exercise was similar for all subjects. The initial level of fitness was related to endurance changes recorded following the training program. The final phase of the study sought to determine the exercise perceived exertion relationship with special reference to the effects of training. The goal was the ability to determine the relationship between one's perception of exercise and his spontaneous physical activity. The subjects were the 36 young men and 18 older men involved in the training study. Another group of eight young men was also tested. Results showed that: (1) the Vamilmandelic Acid (VMA) values were variable; (2) the T-180 times increased for all subjects; and (3) the perceived exertion scores did not exhibit a strong trend. (Author/EK)