Effects of frequency, intensity, duration and volume of walking interventions on CVD risk factors: a systematic review and meta-regression analysis of randomised controlled trials among inactive healthy adults.

OBJECTIVE: Walking interventions in healthy populations show clinically relevant improvements for many cardiovascular disease (CVD) risk factors. We aimed to assess the changes in CVD risk factors and the dose-response relationship between frequency, intensity, duration and volume of walking and cardiovascular risk factors based on randomised controlled trials (RCTs).

DESIGN: A systematic review with meta-analysis and meta-regression.

DATA SOURCES: Four electronic databases searched from January 1971 to April 2017.

ELIGIBILITY CRITERIA: Walking RCTs reporting one or more CVD risk factor outcomes; trials including at least one group with walking intervention and a no-walking control group; duration ≥8 weeks; participants ≥18 years old, inactive but healthy; risk factors assessed preintervention and postintervention; English-language articles in peer-reviewed journals.

RESULTS: Thirty-seven RCTs, involving 2001 participants (81% women) and assessing 13 CVD risk factors, were identified. Pooled meta-analysis showed favourable effects (P≤0.05) of walking intervention for seven CVD risk factors (body mass, body mass index, body fat, systolic and diastolic blood pressure, fasting glucose and VO2 max). T here were no significant effects (P>0.05) for waist circumference, waist-to-hip ratio and four blood lipid variables.Despite testing 91 possible dose-response relationships, linear meta-regression analysis adjusted for age indicated just 7 (or 7.7%) statistically significant findings.

SUMMARY/CONCLUSION: Walking interventions benefit a number of CVD risk factors. Despite multiple studies and tested metrics, only a few dose-response relationships were identified and the possibility of chance findings cannot be ruled out. There is insufficient evidence to quantify the frequency, length, bout duration, intensity and volume of the walking required to improve CVD risk factors.

PROSPERO REGISTRATION NUMBER: CRD42016039409.