The association between daily steps and health, and the mediating role of body composition: a pedometer-based, cross-sectional study in an employed South African population

Pillay, Julian D. and van der Ploeg, Hidde P. and Kolbe-Alexander, Tracy L. and Proper, Karin I. and van Stralen, Maartjie and Tomaz, Simone A. and van Mechelen, Willem and Lambert, Eztelle V. (2015) The association between daily steps and health, and the mediating role of body composition: a pedometer-based, cross-sectional study in an employed South African population. BMC Public Health , 15 (174). pp. 1-12.

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Background: Walking is recognised as an easily accessible mode of physical activity and is therefore supported as a strategy to promote health and well-being. To complement walking, pedometers have been identified as a useful tool for monitoring ambulatory physical activity, typically measuring total steps/day. There is, however, little information concerning dose-response for health outcomes, in relation to intensity or duration of sustained steps. We aimed to examine this relationship, along with factors that mediate it, among employed adults.

Methods: A convenience sample, recruited from work-site health risk screening (N=312, 37±9yrs), wore a pedometer for at least 3 consecutive days. Steps were classified as “aerobic” (≥100 steps/minute and ≥10 consecutive minutes) or 'non-aerobic' (<100 steps/minute and/or <10 consecutive minutes). The data were sub-grouped according to intensity-based categories i.e. 'no aerobic activity', 'low aerobic activity' (1-20 minutes/day of aerobic activity) and 'high aerobic activity' (≥21 minutes/day of aerobic activity), the latter used as a proxy for current PA guidelines (150-minutes of moderate-intensity physical activity per week). Health outcomes included blood pressure, body mass index, percentage body fat, waist circumference, blood cholesterol and blood glucose. Analyses of co-variance, adjusting for age, gender and total steps/day were used to compare groups according to volume and intensity-based steps categories. A further analysis compared the mediation effect of body fat estimates (percentage body fat, body mass index and waist circumference) independently on the association between steps and health outcomes.

Results: Average steps/day were ,574±3,541; Total steps/day were inversely associated with most health outcomes in the expected direction (p<0.05). The 'no aerobic activity' group was significantly different from the 'low aerobic activity' and 'high aerobic activity' in percentage body fat and diastolic blood pressure only (P>0.05). Percentage body fat emerged as the strongest mediator of the relationship between steps and outcomes; body mass index showed the least mediation effect.

Conclusion: The study provides a presentation of cross-sectional pedometer data that relate to a combination of intensity and volume-based steps/day and its relationship to current guidelines. The integration of volume, intensity and duration of ambulatory physical activity in pedometer-based messages is of emerging relevance.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version made available under open access.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Health and Wellbeing
Date Deposited: 27 Mar 2017 02:31
Last Modified: 01 Dec 2017 06:02
Uncontrolled Keywords: physical activity; steps; body composition
Fields of Research : 11 Medical and Health Sciences > 1117 Public Health and Health Services > 111706 Epidemiology
11 Medical and Health Sciences > 1106 Human Movement and Sports Science > 110699 Human Movement and Sports Science not elsewhere classified
Socio-Economic Objective: C Society > 92 Health > 9204 Public Health (excl. Specific Population Health) > 920401 Behaviour and Health
C Society > 92 Health > 9205 Specific Population Health (excl. Indigenous Health) > 920505 Occupational Health
Identification Number or DOI: 10.1186/s12889-015-1381-6

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