The purpose was to compare 24 participants' acute physiological and affective responses to two aerobic prescriptions in three sessions. Anthropometry, International Physical Activity Questionnaire, and VO2max were recorded. In subsequent visits two aerobic prescriptions were randomly applied: one based on VO2max (PBVO2max) and another based on physical activity level (PBPA). Physiological and affective variables were measured in each session. The PBVO2max showed lower risk for dropout than the PBPA. An effect size analysis showed higher ratings on the Feeling Scale in the PBVO2max session at the end of exercise. After categorizing participants by fitness (High, Medium, and Low) according to VO2max, significant differences were observed for the training impulse between Low and High fitness categories, indicating PBVO2Max were sensitive in distinguishing levels of fitness. The PBVO2max, compared to PBPA, seems to provide better physiological and affective responses. VO2max (even if estimated) is recommended as the basis for aerobic prescriptions.