The Population, Exposure, Comparison, Outcome, Study design process
| Item | Specification |
| Population or participants and conditions of interest | Humans (any age, any sex and any health condition). |
| Exposure | Metabolites derived from metabolomics or multiomics studies applying metabolomics approaches. |
| Comparisons or control groups | NA |
| Outcomes of interest | CRF measured by means of a cardiopulmonary exercise test (spiroergometry). |
| Study designs | Any study design, only published studies, no editorials, letters, reviews, meta-analyses, case reports or conference abstracts. |
CRF, cardiorespiratory fitness; NA, not available.