The effect of acute moderate-intensity exercise on the accuracy of air-displacement plethysmography in young adults

BACKGROUND/OBJECTIVES: Air-displacement plethysmography (ADP) body composition systems utilize a precise pre-test protocol that must be followed for each trial. Previous research has shown that body temperature changes influence the results when using ADP as a measurement. The objective of this study is to determine the effect of post-exercise body temperature changes on body composition results using ADP. SUBJECTS/METHODS: Forty young adults (18-30 years) participated in the study (23 females, 17 males). Resting heart rate was measured to calculate exercise intensity. First, an ADP test was done according to the instructions outlined by the manufacturer. Upon completion of the ADP test, the subject exercised on a treadmill at moderate intensity (similar to 65% heart rate reserve) for 30 min to increase body temperature. Another ADP measurement followed the physical activity. Chamber temperature (CT) was measured during each of the trials using a thermistor to assess changes. Fat mass (FM), fat-free mass (FFM), percentage body fat (%BF) and CT were compared pre- and post exercise. RESULTS: Paired sample t-tests revealed significant differences (P<0.05) between pre-exercise %BF and post-exercise %BF (21.3 +/- 9.8% vs 19.6 +/- 10.2%), pre-exercise CT and post-exercise CT (22.7 +/- 1.2 vs 23.0 +/- 1.1 degrees C), and pre-exercise FM and post-exercise FM (14.9 +/- 7.9 vs 13.8 +/- 8.0 kg). FFM showed no significant difference. CONCLUSION: This investigation demonstrates the importance of following the manufacturer's recommended pre-test protocol as the accuracy of the ADP testing may be compromised, resulting in lower FM and %BF estimations.