Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training.

James Steele,Avery Rosa,Mariella Carrasquillo-Mercado,Brad J Schoenfeld,Derrick Van Every,Jozo Grgic,Hugo Zambrano,Daniel Plotkin,Benjiman Mendelovits

doi:10.3390/sports9110155

James Steele, Avery Rosa + Show 7 more

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https://doi.org/10.3390/sports9110155

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Abstract

Purpose: To conduct a systematic review and multilevel meta-analysis of the current literature as to the effects of interval training (IT) vs moderate intensity continuous training (MICT) on measures of body composition, both on a whole-body and regional level. Methods: We searched English-language papers on PubMed/MEDLINE, Scopus, CINAHL, and sportrxiv for the following inclusion criteria: (a) randomized controlled trials that directly compared IT vs MICT body composition using a validated measure in healthy children and adults; (b) training was carried out a minimum of once per week for at least four weeks; (c) published in a peer-reviewed English language journal or on a pre-print server. Results: The main model for fat mass effects revealed a trivial standardized point estimate with high precision for the interval estimate, with moderate heterogeneity (−0.016 (95%CI −0.07 to 0.04); I2 = 36%). The main model for fat-free mass (FFM) effects revealed a trivial standardized point estimate with high precision for the interval estimate, with negligible heterogeneity (−0.0004 (95%CI −0.05 to 0.05); I2 = 16%). The GRADE summary of findings suggested high certainty for both main model effects. Conclusions: Our findings provide compelling evidence that the pattern of intensity of effort and volume during endurance exercise (i.e., IT vs MICT) has minimal influence on longitudinal changes in fat mass and FFM, which are likely to minimal anyway. Trial registration number: This study was preregistered on the Open Science Framework.

Highlights

The relative components of fat mass and fat-free mass in the body, collectively termed body composition, has important implications for human health
We considered the implications of all results compatible with these data, from the lower limit to the upper limit of the interval estimates, with the greatest interpretive emphasis placed on the point estimate
We analyzed 54 studies that compared the effects of interval training (IT) and moderate intensity continuous training (MICT) on measures of body composition

Summary

Introduction

The relative components of fat mass and fat-free mass in the body, collectively termed body composition, has important implications for human health. Excessive levels of body fat show a high correlation with a panoply of disease states, including cardiovascular diseases, metabolic disorders, certain cancers, osteoarthritis, and respiratory conditions [1]. Low levels of fat-free mass are associated with a loss of strength, functional capacity, and reduced bone mineral density [2,3,4], impairing both the quality and quantity of life [1]. There is an interaction between these two components, whereby the combination of low levels of fat-free mass (FFM) and high levels of body fat potentiate each other, maximizing their impact on disability, morbidity, and mortality [5].

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