Insulin resistance, physical activity and physical fitness in adults residing in a northern suburb of Cape Town
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Insulin resistance has shown to be a precursor to a number of lifestylerelated chronic diseases and abnormalities in adults and is affected by a number of factors including genetics, age, physical activity and acute exercise, diet, obesity, body fat distribution and medication. Physical activity has shown to have marked effects on improving sensitivity to insulin though various physiological mechanisms, and numerous correlation studies have identified a relationship between these two variables, suggesting the beneficial role of exercise on insulin resistance. This study aimed to identify a relationship between current levels of physical activity, physical fitness and insulin resistance in adults between the ages of 35 and 65 years of age residing in a northern suburb community in Cape Town. A total of 186 volunteers participated in this study ranging from healthy individuals to those with diagnosed chronic conditions. Insulin resistance (determined by the homeostasis model assessment of insulin resistance), physical activity (measured by the Global Physical Activity Questionnaire) and five health-related physical fitness tests were measured. The five components included body composition, determined by body mass index and waist circumference, the 3-minute cardiorespiratory step test, the handgrip muscle strength test, one-minute crunches for muscle endurance and the sit-and-reach flexibility test. Spearman correlation was used to identify the relationships between the homeostasis model assessment of insulin resistance, age, body composition and physical activity and fitness.Results showed that body mass index and waist circumference were the only two variables which produced significant correlations with the homeostasis model assessment of insulin resistance (p < 0.019). No physical activity or fitness data produced significant scores with the homeostasis model assessment of insulin resistance. Body mass index in men was the only significant predictor of HOMA-IR and explained 37% of the variance in insulin resistance, whereas in women, only waist circumference was related to HOMA-IR, but explained less than 16% of the variance. Associations between reported MET-minutes from the Global Physical Activity Questionnaire and the four fitness tests indicated significance with handgrip strength (ρ = 0.17; p =0.039), one-minute crunches (ρ = 0.18; p = 0.024) and sit-and-reach flexibility (ρ = 0.17; 0.034). This study has shown that body composition is an important component in influencing insulin resistance therefore physical activity interventions should be targeted at increasing physical activity levels and reducing body weight.