Rates of compliance and adherence to high-intensity interval training: a systematic review and Meta-analyses

Table 1 Pre-specified PICOs domains for eligibility criteria

Domain	Inclusion Criteria
Population	• 18–65 years of age • Insufficiently active^a • If activity not specified, diagnosed with a co-morbidity • Not an animal study
Intervention	• Supervised or unsupervised HIIT intervention^b
Comparator	• Supervised or unsupervised MICT intervention^c
Outcomes	• Quantifiable measure of compliance to supervised HIIT program^d • Quantifiable measure of adherence to unsupervised exercise following a supervised HIIT program^e
Study Type	• Full-text available • Peer-reviewed • Observational studies or variations thereof • Randomized controlled trials or variations thereof • Not qualitative, secondary research, grey literature, published protocol, or published abstract^f

^a Insufficiently active is defined as not meeting current physical activity guidelines of 75 minutes of vigorous intensity exercise or 150 minutes of moderate intensity exercise per week [1]
^b HIIT high-intensity interval training; defined as alternating short bursts of high-intensity (> 80% maximum/peak heart rate or equivalent) exercise with recovery periods or light exercise [14]
^c MICT moderate-intensity interval training; defined as achieving between ~ 64 and 76% of maximum heart rate or equivalent for a continuous period of at least 10 minutes [13]
^d Compliance measured as the frequency of attendance to supervised exercise sessions, either as number of sessions or percentage of sessions attended
^e Adherence measured as physical activity engagement in unsupervised settings, either as minutes of MVPA, metabolic equivalent values, number/percentage of prescribed sessions completed, or equivalent
^f Acknowledgement that the exclusion of the mentioned study types may increase the chances of publication bias

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