Table 1 Criteria list for assessment of the methodological quality of prospective studies

Study population and participation (baseline): The study sample represents the population of interest on key characteristics

1. Participation rate at baseline at least 80%, or if the non-response was not selective (show that baseline study sample does not significantly differ from population of eligible subjects)

Study attrition: Loss to follow-up is not associated with key characteristics (i.e. the study data adequately represent the sample)

2. Response at short-term follow-up (up to 12 months) was at least 80% of the number of participants at baseline and response at long-term follow-up was at least 70% of the number of participants at baseline

3. Not selective non-response during follow-up measurement(s) a '+' is given only if non-selective dropout on key characteristics (age, gender, relevant determinants, and outcome measure) is reported in the text or tables

Data collection:

4. Adequate measurement of PA, EX or PA/EX: objective measurement and not by self-report (self-report = '-', no/insufficient information = '?')

5. Determinants of PA or EX behaviour were measured with a reliable tool

'+' is given only if measures of determinants showed ICC/KAPPA of ≥0.60 (or Pearson correlation above .70) assessed within the appropriate target population. For biological variables, a '+' was given only if a standardised protocol was followed, and trained researchers assessed the determinants. A '+' was also given for age, gender, ethnicity, marital status, socio-economic status, employment status, education, income, intervention condition and objective assessment of environmental characteristics (proximity of parks and weather conditions). Expressed as the number of cases in which the measurement of determinants were scored +, divided by the total number of determinants measured in all studies.

6. Determinants of PA or EX behaviour were measured with a valid tool

'+' is given only if measures of determinants showed correlations of ≥0.40 with other similar constructs measured within the appropriate target population. For PA, EX or PA/EX variables (e.g. past physical activity), a '+' was given only if variables were assessed with an objective measurement instrument (e.g. accelerometer/pedometer). For biological variables, a '+' was given only if a standardised protocol was followed, and trained researchers assessed the determinants. A '+' was also given for age, gender, ethnicity, marital status, socio-economic status, employment status, education, income, intervention condition and objective assessment of environmental characteristics (proximity of parks and weather conditions). Expressed as the number of cases in which the measurement of determinants were scored +, divided by the total number of determinants measured in all studies.

Data analyses:

7. The statistical model used was appropriate

8. The number of cases was at least 10 times the number of the independent variables