J. LaPlante, T. Nice, A. Esselstrom, T. Reeves, K. Witzke, FACSM

Oregon State University – Cascades, Bend, OR

Body composition determined by skinfold assessment is based on the assumption that about 50% of an individual’s body fat resides subcutaneously. Conventional wisdom states that body composition measurements should not be done immediately post exercise due to the influence of fluid shifts in tissues. However, there is limited evidence supporting this assumption. PURPOSE: This study aims to establish if there is a significant difference in body composition measurements pre- and post-acute exercise. METHODS: Participants were six males aged 18-43 y and two females aged 19-22 y; who participated in recreational exercise at least twice per week for the previous six months, and were classified as “low risk” by ACSM guidelines. All subjects were within a normal BMI range (18-25 kg/m2). Skinfold measurements (7-site), body composition using bioelectrical impedance analysis (BIA), bicep and thigh circumference were measured at rest and immediately following a workout consisting of a warm up (5 min), dynamic stretching (5 min), a run at a pace equal to an RPE of 7 out of 10 (20 min), and calisthenic exercises (2 sets of 20 push-ups, sit-ups, and squats). Paired Sample T-test, mean, and standard deviation, as well as comparative differences in pre- and post-exercise (IBM SPSS v.21). RESULTS: Results showed that only bicep circumference was significantly increased following an acute bout of exercise. No other measurements were influenced by the exercise session. Pre- and post-exercise mean + SD measurements were: 103.56 + 39.24 mm vs 101.56 + 37.91 mm, p > 0.05 for skinfold, 15.6 + 5.17% vs 15.32 + 4.90%, p > 0.05 for BIA (body fat %). Bicep circumference significantly increased (30.23 + 3.91 cm vs 30.84 + 3.86 cm, p = 0.036), however thigh circumference remained unchanged, 48.11 + 7.47 cm vs 48.41 + 6.99 cm, p > 0.05. CONCLUSION: There was no significant difference in skinfold measurements or BIA body fat percentage pre- and post-acute exercise. Our results confirm previous research showing no influence of exercise on BIA measurement. We did however, demonstrate the possible influence of fluid shift to the skin on circumference measures as a result of acute exercise. However, some subjects’ measurements had to be obtained indoors due to very cold weather, which may have influenced our results. Recommendations for future research include a standardized warm up protocol, a larger, more diverse sample, and a controlled environment for testing and measurements.

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