High-intensity Interval Training, Affect, And Enjoyment: Critical Systematic Review

High-Intensity Interval Training (HIIT) has been included as an option in exercise prescription guidelines and physical activity recommendations. In part, this inclusion is based on conclusions from systematic reviews and meta-analyses that HIIT is a “viable alternative” to the traditional modality of continuous activity in terms of affective (e.g., pleasure-displeasure) and enjoyment responses. These conclusions, however, stand in contrast to a voluminous literature demonstrating that exercise intensity approaching maximal capacity (e.g., 80-100% of maximal heart rate or oxygen uptake) is universally experienced as unpleasant and unenjoyable. We hypothesized that this apparent contrast could be due to specific methodological limitations. PURPOSE: To critically appraise the methodological features of studies comparing affective and enjoyment responses to HIIT and moderate-intensity continuous exercise sessions, using a systematic approach. METHODS: Medline and PsycINFO were searched using PRISMA 2020 procedures. A 12-item risk-of-bias tool was developed based on previously established methodological guidelines for the study of affective and enjoyment responses to exercise. RESULTS: Of 249 articles initially identified through computer searches, 39 met the inclusion and exclusion criteria. Nearly all studies were characterized by high risk of methodological bias. CONCLUSIONS: Conclusions from previous systematic reviews and meta-analyses that HIIT and its variants, including Sprint Interval Training, represent a “viable alternative” or are more pleasant and/or more enjoyable than moderate-intensity continuous exercise, should be viewed cautiously due to methodological limitations. Some of the sources of bias are general (e.g., sample-selection bias, low statistical power) but some are specific to this line of research and their detection may require multidisciplinary expertise (e.g., intensity manipulations, psychometrics of affect, timing of measure administration). Therefore, the purpose-designed risk-of-bias tool may be useful in assisting peer reviewers, journal editors, and other critical readers in the evaluation of the methodological rigor of future studies.