Browsing by Subject "Acute exercise"

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    Dual X-Ray Absorptiometry May Not Be Sensitive Enough To Measure Changes In Regional Fat After Acute Exercise
    (2017-06) Brayton, Seth
    ABSTRACT Objective: We sought to determine if an acute bout of running accounts for measurable changes in total and regional body fat using Dual X-ray Absorptiometry (DXA). There is limited research about the change in body fat after an acute bout of physical activity. Knowing how body composition changes as a result of exercise is important for populations with symptoms of metabolic syndrome, such as overweight/obesity, increased waist circumference, high triglycerides, low levels of high density lipoprotein (HDL), increased total cholesterol, increased systolic and diastolic blood pressure, increased blood glucose and physical inactivity that can eventually lead to conditions like heart disease and diabetes (1). As the amount of visceral fat a subject has increases, so does their risk for metabolic syndrome. In addition, knowledge of body composition changes is useful in athletic populations for injury prevention and performance in athletes (2). Methods: Subjects that were between the age of 18 – 40, that reported a history of regular running exercise (approximately 45 minutes, 5 times a week), were otherwise healthy and could commit to running 90 minutes on a treadmill were recruited. All subjects completed a 90-minute run on a treadmill at 60% heart rate reserve (HRR). Body composition was measured before and immediately after the run to determine if DXA was sensitive enough to measure potential changes in body fat following acute exercise. For the present study, total and regional body fat was compared to show if particular regions had a greater change in fat during endurance exercise. The difference in pre-run to post run total and regional body fat was compared using paired t tests. Comparisons between normal weight, overweight/obese, and overall groups were made using nonpaired t tests. Statistical significance was accepted using P-value > 0.05 Changes to total and regional body fat were also compared to the least significant change (LSC) for DXA found in the literature for athletic populations. Results: A total of 16 lean (female = 7; male = 9; age = 28.1 ± 5.6 yrs; BMI = 22.0 ± 1.6 kg/m2) and 11 overweight or obese (female = 7; male = 4; age = 32.0 ± 5.2 yrs; BMI = 30.5 ± 4.8 kg/m2) were recruited and completed both study visits. Weight, VO2max, Body Mass Index (BMI), and baseline percent body fat were significantly different between the normal and overweight/obese groups. Height and age were not significantly different between the groups. No significant differences were found in the absolute change in normal and overweight/obese group. Absolute fat mass decreased slightly overall (-184.5 ± 443.6 g). There was no significant change in BF from arms or legs within the overall group. A significant loss of fat came from the trunk (-195.1 ± 488.3 g). Android/gynoid ratio change shows significant decrease (-0.02 ± 0.04), in the overall group. Although significant absolute fat loss from the trunk and the android/gynoid ratio, the difference in fat for the regions was not more than LSC using test-retest technique found in the literature. Conclusion: Significant differences in fat mass were observed from the trunk and the android/gynoid ratio regions after a 90-minute run at 60% HRR. However, when comparing these changes to the published research on least significant difference of DXA, the change in fat mass observed in this study is less than least significant difference of DXA. This means that the changes in fat measured by DXA in this study may not be accurate.