This study aims to quantify the effects of high-intensity interval training (HIIT) on cardiorespiratory fitness (CRF) by considering potential moderators and to characterise dose-response relationships of HIIT variables that could maximise CRF improvements in overweight and obese adults. Following a comprehensive search through four electronic databases, 19 studies met eligibility criteria. Random-effects models were applied to weight all included studies and to compute the weighted mean standardised mean differences (SMDwm). Meta-analysis showed that HIIT was a highly effective approach for improving CRF in overweight and obese adults (SMDwm = 1.13). Effects were modified by sex and baseline CRF level. Dose-response relationship analysis provided some preliminary data regarding the training period, training intensity, and session duration. However, it is still not possible to provide accurate recommendations currently. Further studies are still needed to identify the most appropriate training variables to prescribe effective HIIT programmes for improving CRF in overweight and obese adults.
Keywords: Intermittent training; adult obesity; dose–response relationship; physical fitness.