Exercise Dose Equalization in High-Intensity Interval Training: A Scoping Review.

Area of Science:

• Exercise Physiology
• Sports Science
• Methodology in Exercise Research

Background:

• High-intensity interval training (HIIT) is a growing global trend in physical exercise.
• Comparing HIIT to moderate-intensity continuous training (MICT) necessitates methodological rigor, particularly in equalizing exercise dose.
• Existing literature reveals inconsistencies in how exercise protocols are equalized for comparative studies.

Purpose of the Study:

• To conduct a scoping review identifying evidence for exercise protocol equalization in HIIT vs. MICT comparisons.
• To assess the soundness and consensus of methods used for exercise dose equalization in the literature.
• To explore the implications of different equalization strategies on the interpretation of exercise training effects.

Main Methods:

• Searched PubMed and Scopus databases for original investigations comparing HIIT and MICT.
• Included 169 articles from an initial pool of 2041 identified studies.
• Analyzed 98 articles that employed energy-based methods or exercise volume for protocol equalization.

Main Results:

• No clear consensus on protocol equalization methods has emerged in recent years.
• Many studies equalize exercise dose using absolute energy expenditure or volume, neglecting its nonlinear relationship with duration.
• These methods often result in maximal exertion for HIIT but low exertion for MICT, questioning the validity of comparisons.

Conclusions:

• Current exercise dose equalization methods in HIIT vs. MICT research are often inadequate.
• Considering exercise dose relative to individual maximums, rather than absolute values, may yield more accurate comparisons.
• Future research should prioritize relative quantification of exercise dose to enhance the methodological soundness of training intervention studies.