Modification of cardiometabolic disease risk factors in overweight children: An exploratory study of different exercise doses

IntroductionThe percentage of overweight primary school children in South Africa increased from 1.2% in 1994 to 13% in 2004 (Armstrong et al., 2011). Although morbidity from obesity-related disorders (e.g. cancer, congestive heart failure, pulmonary embolism, chronic renal failure, and depression) generally manifests during adult years, the pathological processes begin during pediatric years (Guillaume et al., 1997; Shalitin et al., 2009; Gutin & Owens, 2011). The NAHSIT-ESC (Nutrition and Health Survey in Taiwan Elementary School Children) survey reported that obese children have higher blood pressure, triglyceride levels, low-density lipoprotein cholesterol, uric acid, and serum glutamic pyruvic transaminase levels when compared with normal weight children (Chu, 2005; Chu & Pan, 2007). The prevalence of children leading sedentary lifestyles has increased over the years, and a variety of environmental factors have contributed to this problem. Two key environmental factors that have fueled the obesity epidemic are diets rich in fat and processed carbohydrates as well as physical inactivity (Shalitin et al., 2009). Regular physical activity (PA) lowers the prevalence of cardiometabolic disease risk factors (Sattelmair et al., 2011). The progression and associated complications of the disease is best modified during early years (Barbeau et al., 2007). A range of substantial health benefits is associated with accumulating 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity PA per week (ACSM, 2010). Classification of the required amount of PA is possible when considering the metabolic equivalent of activities, though restrictions exist when assigning energy costs in children (Spadano et al., 2003; Warburton, Nicol, & Bredin, 2006; Bushman, 2012). Several studies question the effectiveness of the recommended PA guidelines for children in preventing cardiovascular disease risks (Andersen et al., 2006; Gutin & Owens, 2011). An observational study suggests that 90 minutes of moderate-intensity PA per day is necessary to prevent insulin resistance in children (Andersen et al., 2006). In contrast, meta-analysis revealed that vigorous-intensity PA is more effective in modulating biomarkers and is associated with greater improvements in fitness and fat percentages in youth compared with moderate-intensity PA (Gutin & Owens, 2011). The global obesity epidemic will likely result in the prevalence of cardiometabolic disease risk factors manifesting at younger and younger ages, yet little evidence is available on the particular exercise prescription for reducing cardiometabolic disease risk factors in children. Therefore, the current study sought to investigate the effect of 2 different exercise doses on cardiometabolic disease risk factors in overweight children.Materials & MethodsParticipants A convenience sample of twelve (nine male, three female) 11-13-year-old children were recruited from the Zululand area in South Africa. Nine participants were Caucasian, and 3 were African. Participants were screened prior to the inclusion in the study to ensure that the requirements of being classified as overweight were met (Heber, 2002). Participants taking chronic medications that are known to affect heart rate/pulmonary function were excluded. The study was approved by the Ethics Committee of the Faculty of Science & Agriculture at the University of Zululand, South Africa. Signed informed assent and consent forms were obtained from the participants and parents or guardians of the participants.Instruments and MeasurementsData collection took place over three consecutive days. Post-measurements were taken within a week after the participants completed the exercise programs.Target Heart RateTarget heart rate was measured continuously using a polar heart rate monitor during the exercise programs. This ensured the set target heart rate ranges for the respective exercise groups. …