Abstract
BACKGROUND: Urban environments can increase risk for development of obesity, insulin resistance (IR), and type 2 diabetes mellitus (T2DM) by limiting physical activity. This study examined, in a cohort of urban Hispanic youth, the relationship between daily physical activity (PA) measured by GPS, insulin resistance and cardiovascular fitness. METHODS: Hispanic middle school children (n = 141) were assessed for body mass index (BMI), IR (homeostasis model [HOMA-IR]), cardiovascular fitness (progressive aerobic cardiovascular endurance run [PACER]). PA was measured (GPS-PA) and energy expenditure estimated (GPS-EE) utilizing a global positioning mapping device worn for up to 7 days. RESULTS: Students (mean age 12.7 ± 1.2 years, 52% female) spent 98% of waking time in sedentary activities, 1.7% in moderate intensity PA, and 0.3% in vigorous intensity. GPS analysis revealed extremely low amounts of physical movement during waking hours. The degree of low PA confounded correlation analysis with PACER or HOMA-IR. CONCLUSIONS: Levels of moderate and vigorous intensity PA, measured by GPS, were extremely low in these urban Hispanic youth, possibly contributing to high rates of obesity and IR. Physical movement patterns suggest barriers to PA in play options near home, transportation to school, and in school recess time. GPS technology can objectively and accurately evaluate initiatives designed to reduce obesity and its morbidities by increasing PA.