Table 1 Inclusion and exclusion criteria for screening of search results

• Primary results report on association (or lack of association) between one or more personal and/or interpersonal factor(s) and CRF

• CRF measured through maximal or submaximal ergometry test

• Results reported for adults (18–65 years) in the general population

• CRF considered as an exposure variable (rather than as an outcome variable) in the study design and analysis

• Study conducted in a highly selected population. Examples are:

− Patients with specific disorders or medical conditions (e.g. coronary artery disease, heart failure, schizophrenia, chronic obstructive pulmonary disease)

− Individuals categorized as obese

− Military personnel

− Professional athletes

• Randomized controlled trial or another type of quasi-experimental design where participants receive a fitness or exercise training intervention that increases CRF

• Qualitative study design (focus groups, open-ended interviews, and thematic reviews)

• Editorials, letters to the editor, or commentaries