The University of Alabama, Tuscaloosa, AL TIME COURSE TOWARD BASELINE OF HAND-TO-FOOT BIA BODY FAT PERCENTAGE FOLLOWING AN ACUTE BOUT OF AEROBIC EXERCISE Kelsey A. Pezzuti, Brett S. Nickerson, Bailey A. Welborn, Mark T. Richardson, and Michael R. Esco The University of Alabama, Tuscaloosa, AL Table 1. Comparison of BIA-derived BF% PRE and all post-exercise BIA measures (n = 15) Abstract Methods Time Mean ± SD P Cohen’s d CE ± 1.96 SD Upper Lower PRE 22.4 ± 3.6 - IP 20.1 ± 3.5 <0.001 0.65 2.3 ± 1.5 3.8 0.8 10P 20.3 ± 3.4 0.58 2.0 ± 1.7 0.3 20P 21.0 ± 3.6 0.38 1.4 ± 1.7 3.1 -0.4 30P 21.4 ± 3.7 0.002 0.25 0.9 ± 1.8 2.7 -0.9 40P 22.1 ± 3.7 0.337 0.07 0.3 ± 2.0 2.2 -1.7 50P 22.3 ± 3.7 0.906 0.01 0.03 ± 2.1 2.1 -2.1 60P 22.5 ± 3.6 0.530 -0.04 -0.2 ± 2.0 1.9 -2.2 Bioelectrical impedance analysis (BIA) is a common field method used to measure body fat percentage (BF%) in sport and health and fitness settings. Though a bout of exercise may influence the reliability of BIA, limited research exists to examine this possibility. PURPOSE: The purpose of this investigation was to examine the influence of an acute bout of aerobic exercise followed by a 1-hour recovery period on predicted BF% via BIA. METHODS: Fifteen college-aged adult males volunteered to participate in this study (age = 23.73 ± 3.7 years, height = 176.6 ± 6.8 cm, weight = 81.1 ± 10.3). A urine specific gravity (USG) < 1.020 was required by all participants prior to testing to ensure hydration status. Following USG measurements, each participant completed a 30-minute steady state treadmill bout of exercise at an intensity of 60% estimated heart rate reserve. BIA was measured before exercise (PRE), immediately post-exercise (IP), and at 10, 20, 30, 40, 50, and 60-minutes post-exercise. RESULTS: The estimated BF% value via BIA at PRE was 22.35 ± 3.56%. The post-exercise measures were as follows: IP = 20.05 ± 3.49%; 10-min post = 20.32 ± 3.36%; 20-min post = 20.97 ± 3.57%; 30-min post = 21.43 ± 3.68%; 40-min post = 22.09 ± 3.71%; 50-min post = 22.31 ± 3.68%; 60-min post = 22.52 ± 3.63%. Compared to PRE, BIA measures at IP, (p < 0.001, Cohen’s d = 0.65), 10-min post (p < 0.001, Cohen’s d = 0.58), 20-min post (p < 0.001, Cohen’s d = 0.38), and 30-min post (p = 0.002, Cohen’s d = 0.25) were significantly different. However, the remaining post-exercise measures were not significantly different than PRE (p values ranged from 0.34 to 0.91). Intraclass correlations showed that the post-exercise measures provided very large (ICC = 0.89 for IP) to near perfect (ICC = 0.91 to 0.98 for 10 to 60-min post values) relationships with PRE. CONCLUSIONS: The findings from this study suggest that when compared to PRE, BIA estimates of BF% were significantly lower up to 30 minutes following exercise before approaching baseline values thereafter. The very large to near perfect ICCs suggested similar patterns of variation in estimated BF% at each post-exercise time point when compared to PRE. PRACTICAL APPLICATIONS: Practitioners should consider the results of this study before estimating BF% with BIA within a health and fitness setting. When a bout of exercise was recently completed, a time period of least 40 minutes may be required to produce a value that is similar to pre-exercise levels. Though further research is needed, the time requirement following exercise may be less than what manufactures currently recommend for reliable estimates of BF% via BIA. Fifteen college-aged adult males volunteered to participate in this study (age = 23.73 ± 3.7 years, height = 176.6 ± 6.8 cm, weight = 81.1 ± 10.3). Prior to body composition testing, all participants were required to be hydrated and provide a urine specific gravity < 1.020. Once hydration was confirmed, subjects had their height and weight measured. After height and weight measurements, subjects laid on a gurney for 5 min and had BF% determined with a hand-to-foot single-frequency BIA device. Next, subjects were instructed to complete a 30 min bout of aerobic exercise on a treadmill at an estimated 60% heart rate reserve. Immediately after the bout of exercise, subjects provided another body weight measurement to determine weight loss during exercise. Finally, subjects laid supine and had BF% measured in 10 min intervals up until 60 min post-exercise to determine if BF% measures would return to baseline. BIA = bioelectrical impedance analysis; CI = confidence interval; CE = constant error; IP = immediate post; 10P = 10 min post-exercise; 20P = 20 min post-exercise; 30P = 30 min post-exercise; 40P = 40 min post-exercise; 50P = 50 min post-exercise; 60P = 60 min post-exercise Results BF% significantly lower IP – 30P BF% non-significant for 40P – 60P Effect sizes were trivial to to moderate Limits of agreement narrowest for IP and widest for 50p * * * * Conclusions and Practical Applications This study found that BIA values return to baseline values approximately 40 min after an acute bout of moderate exercise. The BIA recommendation of avoiding exercise 12 h prior to testing is arbitrary and no study to date has sought to determine a specific time point needed for values to return to baseline after exercise. Results from the current study suggest that practitioners in the field utilizing can utilize BIA after only 40 min of moderate exercise. Intro & Purpose BIA devices are often used in field settings due to their quick administration time and affordability. Manufacturers recommend avoiding exercise 12 h prior to BIA utilization, which makes the use of these devices less practical in a field setting when adherence to these guidelines can be difficult to follow. The purpose of this investigation was to examine the influence of an acute bout of aerobic exercise followed by a 1-hour recovery period on predicted BF% via BIA. Figure 1. Mean BIA BF% at each time point (n = 15) *Post-exercise BIA values that were significantly different than PRE BIA values (all p < 0.002)