Descriptive Epidemiology of Ambulatory Activity in Rural, Black South Africans

COOK, I., M. ALBERTS, J. S. BRITS, S. R. CHOMA, and S. S. MKHONTO. Descriptive Epidemiology of Ambulatory Activity in Rural, Black South Africans. Med. Sci. Sports Exerc., Vol. 42, No. 7, pp. 1261-1268, 2010. Purpose: We investigated the distribution of objectively measured ambulation levels and the association of ambulation levels to adiposity levels in a convenience sample of adolescent and adult, rural black South Africans. Methods: We analyzed 7-d pedometry data, collected over a period of nine consecutive days, in 789 subjects (women, n = 516; men, n = 273). Adiposity measures included body mass index (BMI) and waist circumference (WC). Obesity was defined as BMI >= 30 kg.m(-2) or WC >= 102 cm for men and WC >= 88 cm for women. Results: The average age-and BMI-adjusted 7-d ambulation level was 12,471 steps per day (95% confidence interval (CI) = 12,107-12,834). Ambulation levels differed between sexes (P = 0.0012), and weekday ambulation differed from weekend ambulation (P = 0.0277). Prevalences, age adjusted to the world population, for sedentarism (SED; <5000 steps per day), low active-somewhat active (5000-9999 steps per day), and active-very active (ACT; >= 10,000 steps per day) were 8.0%, 25.5%, and 66.6%, respectively. In contrast, published self-reported national prevalences for physical inactivity, insufficient physical activity, and physically active have been estimated to be 43%-49%, 20%-27%, and 25%-37%, respectively. After adjusting for sex and age, adiposity measures remained significantly associated with steps per day (BMI, r = -0.08; WC, r = -0.12; P < 0.03). Adjusting for sex, age, village, and season, SED increased the risk of obesity by more than twofold compared with ACT (P < 0.05). Achieving <10,000 steps per day compared with ACT was associated with an increased multivariate-adjusted obesity risk of 86%-89% (P < 0.001). Conclusions: Ambulation levels were high for this rural African sample, and prevalences for SED and ACT differed from published self-reported estimates.