Physical fitness differences between rural and urban children from western Kenya.

OBJECTIVES: To study the effects of urbanization on physical fitness (PF), we compare PF between urban and rural children from western Kenya. We hypothesize that active rural children are stronger, more flexible, and have greater endurance, and that PF differences are predictive of endurance running performance. METHODS: We recruited an age-matched, cross-sectional sample of participants (55 males, 60 females; 6-17 years) from schools near Eldoret, Kenya. PF and anthropometrics were assessed using the FITNESSGRAM®. General linear mixed models (GLMM) and path analyses tested for age, sex, and activity group differences in PF, as well as the effects of PF variables on mile run time. RESULTS: On average, urban participants had greater body mass (36.8 ± 15.9 vs. 31.9 ± 10.9 kg) but were not taller than rural participants (1.4 ± 0.2 vs. 1.4 ± 0.2 cm). Greater urban body mass appears driven by higher body fat (28.2 ± 9.4 vs. 16.8 ± 4.4%), which increased with age in urban but not rural participants. GLMM analyses showed age effects on strength variables (P<0.05) and sex differences in hip flexibility, sit-ups, and mile run (P<0.05). There were few differences in PF between groups except rural participants had stronger back muscles (18.2 ± 4.5 vs. 14.18 ± 4.3 cm) and faster mile times (6.3 ± 0.7 vs. 7.9 ± 2.0 min). Body composition and abdominal strength were predictive of mile time (P < 0.06), but the path analysis revealed a network of interacting direct and indirect effects that influenced endurance performance. CONCLUSIONS: Although differences in endurance and body composition are marked between urban and rural groups, strength and flexibility are not always correlated with overall activity levels. Am. J. Hum. Biol. 28:514-523, 2016. © 2015 Wiley Periodicals, Inc.

Variation in Foot Strike Patterns among Habitually Barefoot and Shod Runners in Kenya.

Runners are often categorized as forefoot, midfoot or rearfoot strikers, but how much and why do individuals vary in foot strike patterns when running on level terrain? This study used general linear mixed-effects models to explore both intra- and inter-individual variations in foot strike pattern among 48 Kalenjin-speaking participants from Kenya who varied in age, sex, body mass, height, running history, and habitual use of footwear. High speed video was used to measure lower extremity kinematics at ground contact in the sagittal plane while participants ran down 13 meter-long tracks with three variables independently controlled: speed, track stiffness, and step frequency. 72% of the habitually barefoot and 32% of the habitually shod participants used multiple strike types, with significantly higher levels of foot strike variation among individuals who ran less frequently and who used lower step frequencies. There was no effect of sex, age, height or weight on foot strike angle, but individuals were more likely to midfoot or forefoot strike when they ran on a stiff surface, had a high preferred stride frequency, were habitually barefoot, and had more experience running. It is hypothesized that strike type variation during running, including a more frequent use of forefoot and midfoot strikes, used to be greater before the introduction of cushioned shoes and paved surfaces.