Physical activity (PA) practices among South African (SA) school learners are reported to be insufficient to promote health and prevent chronic diseases. [1] SA's 2014 Report Card on Physical Activity for Children and Youth [1] indicates that <50% of learners (6-18 years) meet the recommended amount of 60 minutes of moderate to vigorous PA (MVPA) a day. [1] Low PA levels are partly responsible for the obesity epidemic that threatens the wellness of the SA population and the country's economy. Research indicates that 31.9% of SA learners aged 6-13 years are overweight and 8.1% are obese. [2] A more recent study classified 15-25% of 9-10-year-old SA learners as overweight or obese. [3] Major healthcare challenges are deemed to arise from populations that are physically inactive, and it is reported that physical inactivity is the fourth leading risk factor contributing to global mortality. [4] Physical inactivity may be responsible for 22% of ischaemic heart disease, 14% of type 2 diabetes mellitus, 16% of colon cancer, 11% of ischaemic stroke and 10% of breast cancer. [5] In addition, several studies have shown a positive association between physical inactivity and healthcare costs. [6-7] Objective Establishing profiles of PA is critical for intervention research that will aid in tackling the chronic diseases associated with physical inactivity and avoiding healthcare costs. This study examined the prevalence of PA in SA learners, detailing differences between gender, ethnicity, age and region. Updating PA profiles of SA learners may provide awareness around and contribute towards achieving the health-related Sustainable Development Goals for 2030. [8] Methods Participants Seven thousand, three hundred and forty-eight SA learners (3 867 males and 3 481 females) aged 8-14 years completed the Physical Activity Questionnaire for Older Children (PAQ-C) between August and November 2012. The mean age was 11.14 years (standard deviation (SD) 1.46). School principals in seven provinces (Gauteng, North West, KwaZulu-Natal, Northern Cape, Western Cape, Eastern Cape, Mpumulanga) provided written or verbal consent prior to participation. Learners were categorised by ethnic group as white (Caucasian descent, n=3 634), black (African descent, n=2 857) or other (coloured or Indian descent, n=857). The learners were mainly white (49%) and black (39%) and from NorthWest (29%) and Gauteng (27%) provinces. For the purpose of the study, we defined 'urban area' as a locality characterised by a range of public and private service providers with a population of >15 000 inhabitants. [9,10] The University of Zululand's research ethics committee provided ethical clearance for the study (ref. no. 171110-030). This open-access article is distributed under Creative Commons licence CC-BY-NC 4.0.
Background: Chronic exercise training is associated with improvements in body composition and/aerobic fitness. This presents a challenge to study effects of exercise in isolation. Metabolic effects of short-term exercise training (≤ 12 weeks) are unclear, with studies reporting improvements or no change in insulin sensitivity and/or glucose control. This review systemically examined randomized controlled trials (RCTs) to establish whether short-term exercise training improves insulin resistance and type 2 diabetes (diabetes). Methods: Following the PRISMA guidelines, a systematic review was conducted on nine electronic databases (BMC Endocrine Disorders, Clinical Key, Cochrane Library, EBSChost, PubMed, Scopus, Sabinet_SA Publications, The Lancet and Web of Science) to identify randomized controlled human trials (2005-2018) examining effects of short-term exercise training (≤ 12 weeks) in overweight/obese adults with insulin resistance or diabetes. Search terms included: insulin resistance, type 2 diabetes, short-term, exercise or energy expenditure and randomized controlled trial. Studies were only included if they provided sufficient data on: insulin sensitivity, glycemic control, body composition and aerobic fitness. Results: From 374 articles, three met the inclusion criteria. Of these, two prescribed moderate intensity training (MIT); rate of perceived exertion (RPE) 12-13 and 60% lactic threshold (LT) for four and twelve weeks, respectively while one prescribed vigorous exercise training at 70% VO2max for seven days. Duration of exercise sessions was 40-60 minutes. Twelve weeks of MIT was associated with improved glycemic control vs. no change in the 7-d and four weeks studies. Seven days of vigorous training was associated with greater improvement in insulin sensitivity, 44.4% vs. no change in the four-and twelve-weeks studies. Conclusion: Short-term exercise appears to improve insulin sensitivity and glucose control independent of body fat loss or gains in aerobic fitness. Vigorous exercise training was associated with superior improvements in insulin sensitivity. More RCTs are needed to confirm these findings.
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