Psychological and Behavioral Responses to Interval and Continuous Exercise.

PURPOSE: To compare psychological responses to, and preferences for, moderate-intensity continuous training (MICT), high-intensity interval training (HIIT), and sprint interval training (SIT) among inactive adults; and to investigate the relationships between affect, enjoyment, exercise preferences, and subsequent exercise behavior over a 4-wk follow-up period.

METHODS: Thirty inactive men and women (21.23 ± 3.81 yr), inexperienced with HIIT or SIT, completed three trials of cycle ergometer exercise in random order on separate days: MICT (45 min continuous; approximately 70% to 75% of HR maximum (HRmax)); HIIT (10 × 1 min bouts at approximately 85% to 90% HRmax with 1-min recovery periods); and SIT (3 × 20-s "all-out" sprints with 2-min recovery periods). Perceived exertion (RPE), affect, and arousal were measured throughout the trials and enjoyment was measured postexercise. Participants rank-ordered the protocols (1-3) according to preference and logged their exercise over a 4-wk follow-up.

RESULTS: Despite elevated HR, RPE, and arousal during work periods (P's < 0.05), and negative affect during HIIT and SIT, enjoyment and preferences for MICT, HIIT, and SIT were similar (P's > 0.05). In-task affect was predictive of postexercise enjoyment for each type of exercise (r's = 0.32 to 0.47; P's < 0.05). In-task affect and postexercise enjoyment predicted preferences for HIIT and SIT (rs's = -0.34 to -0.61; P's < 0.05), but not for MICT (P's > 0.05), respectively. Over the follow-up, participants completed more MICT (M = 6.11 ± 4.12) than SIT sessions (M = 1.39 ± 1.85; P < 0.01, d = 1.34). Although participants tended to complete more sessions of MICT than HIIT (M = 3.54 ± 4.23; P = 0.16, d = 0.56), and more sessions of HIIT than SIT (P = 0.07, d = 0.60), differences were not significant. In-task affect predicted the number of sessions of MICT (r = 0.40; P < 0.05), but not HIIT or SIT (P's > 0.05).

CONCLUSIONS: This study provides new evidence that a single session of HIIT and SIT can be as enjoyable and preferable as MICT among inactive individuals and that there may be differences in the exercise affect-behavior relationship between interval and continuous exercise.