Jumping is not just about height: Biosocial becomings as an integrative approach in understanding contextualized jump performance in Maasai society.

Studies focused on jumping performance in humans have so far investigated either its biological or sociocultural significance, with very little attentions paid to the inseparable relations of these two aspects in daily life of people. Integrating both ethnographic and biomechanical methods, this research investigated the biosocial features of the jump performance of Maasai youth in its most well observed context, the wedding ceremony. Ethnographic data were used to explain the social status of participants, the physical movements and singing tempo of performers, and their interactions. Biomechanical methods were applied to assess the heights and frequencies of identified repetitive double-legged vertical jumps (n = 160, from 15 male youths). All youth performers followed a certain posture pattern, paying specific attention to their final landing. Large variations exist in their jumping heights [coefficient of variation (CV) = 0.237]; however, the frequency in jump repetitions were maintained with the least variations (CV = 0.084). Cheering interactions were confirmed, but with no significant difference in height between the cheered and non-cheered groups. These results indicate that the Maasai youths did not compete for jump height during local ceremonies. Rather, they emphasized the rhythmical retention of jumps, corresponding to other youth mates who were singing alongside. In the broader context of human behaviors, the analysis addresses the diverse meanings of motor performances in different daily contexts that reject the generalized sports regime of "higher/faster-the-better".

Segmented physical activity and sedentary behavior patterns among children in Maasai village and Nairobi city.

OBJECTIVES: Urban-rural comparisons between those who maintain traditional lifestyles such as pastoralist Maasai children, and those who live in cities such as Nairobi, provide implications on how urbanization is associated with children's physical activity (PA) and sedentary behavior (SB) patterns. This study compares PA and SB volumes and patterns across different segments of the week among children in Maasai village and Nairobi city in Kenya. METHOD: A total of 261 children (11.4 ± 1.3 years) from Maasai (n = 118) and Nairobi (n = 143) participated in this cross-sectional study. Moderate- to vigorous-intensity PA (MVPA) and SB on weekdays (before, during, and after school) and weekends (morning, afternoon, and evening) were calculated using accelerometers (ActiGraph). Screen time and sleep duration were assessed using questionnaires. RESULTS: Maasai children were more physically active than Nairobi children with MVPA (min/day) of 166.6 and 81.4 for Maasai and Nairobi boys and 116.4 and 77.4 for Maasai and Nairobi girls, respectively. Our week segments analyses suggested that Maasai children were more active both in and out of school than Nairobi children. Additionally, Nairobi children spent more time watching television and playing computer games than Maasai children. There was no significant difference in sleep duration between Maasai and Nairobi children. CONCLUSION: Our findings suggest that urbanization is negatively associated with activity patterns both in and out of school in Kenyan children. This is concerning given that Kenya is currently undergoing rapid urbanization, which may lead to further reductions in PA among Kenyan children.

Physical Activity and Sedentary Behaviour Patterns among Kenyan and Japanese Children: A Comprehensive Cross-Country Comparison.

Health benefits of physical activity are well known, yet available physical activity data is limited from children living in African and Asian countries. The purpose of the cross-sectional study was to evaluate and compare physical activity and sedentary behavior patterns, particularly hourly variations, among children in Kenya and Japan. Participants included 298 primary school students (122 Kenyan, 176 Japanese) aged 9-12 years. Physical activity and sedentary behavior were measured with accelerometers. Domain-specific physical activity, screen time, and proportion of children using active transport to school were measured by questionnaire. A two-way ANOVA (countries × time) was used to examine the differences in the activity patterns between Kenyan and Japanese children. The results from the present study demonstrated that Kenyan children spent more time in moderate-to-vigorous physical activity compared to Japanese children (p < 0.05) with the greatest differences found for weekday evenings (for boys and girls) and weekend afternoons (for girls). This suggests that these were 'critical periods' to differentiate the physical activity levels between Kenyan and Japanese children. However, a higher proportion of the children from Japan used active transport to school and spent less time in television viewing and computer gaming. The results suggest that both countries have successes and challenges that can aid in developing effective and country-specific intervention strategies for promoting physical activity.

Pulmonary mechanics and gas exchange during exercise in Kenyan distance runners.

PURPOSE: The purpose of this study was to determine arterial blood gases, the mechanical limits for generating expiratory flow and the work performed by the respiratory muscles during treadmill exercise in Kenyan runners. METHODS: Kenyan runners (10 men and 4 women; mean ± SD age = 25.2 ± 1.3 yr) were instrumented with a radial artery catheter, an esophageal balloon-tipped catheter, and an esophageal temperature probe for the determination of blood gases, the work of breathing and core temperature, respectively. Testing occurred at 1545 m above sea level. RESULTS: There were significant decreases in the arterial partial pressure of O2 and oxyhemoglobin saturation and a widening of the alveolar-to-arterial difference in O2 from rest to peak exercise. The mechanical work of breathing increased with increasing minute ventilation and was commensurate with values expected for treadmill running in elite athletes. During heavy exercise, significant expiratory flow limitation was present in half of the subjects while the remaining subjects demonstrated impending flow limitation. CONCLUSIONS: Pulmonary system limitations were present in Kenyan runners in the form of exercise-induced arterial hypoxemia, expiratory flow limitation, and high levels of respiratory muscle work. It appears that Kenyan runners do not possess a pulmonary system that confers a physiological advantage.