Dixon, CB and Andreacci, JL. Effect of resistance exercise on percent body fat using leg-to-leg and segmental bioelectrical impedance analysis in adults. J Strength Cond Res 23(7): 2025-2032, 2009-The purpose of this study was to examine the effect of a resistance exercise bout on percent body fat (%BF) measured by leg-to-leg and segmental bioelectrical impedance analysis (LBIA; SBIA) in adults. Eighty-six volunteers (45 women; 41 men) reported to the weight training facility on 2 separate occasions. After an initial LBIA and SBIA assessment, subjects performed 60 minutes of continuous resistance exercise, or did nothing, which served as the control. During the resistance exercise trial, subjects completed an 8-exercise circuit protocol consisting of 3 sets of 10 to 12 repetitions at 65-75% of 1 repetition maximum for each exercise. Subjects were provided with a bottle of water for consumption during both trials. Body composition was reassessed 60 minutes after baseline for comparison. For the resistance exercise trial, significant reductions (p < 0.05) in SBIA-measured %BF (women = 0.9 ± 1.0%; men = 1.4 ± 0.8%) and impedance (women = 22.2 ± 17.0 Ω; men = 22.3 ± 10.0 Ω) were observed, whereas LBIA body composition measurements remained unchanged. After the control trial, significant increases (p < 0.05) in SBIA-measured %BF (women = 0.6 ± 0.8%; men = 0.5 ± 0.7%) and impedance (women = 7.8 ± 12.6 Ω; men = 4.7 ± 8.3 Ω) and LBIA-measured %BF (women = 0.4 ± 0.7%; men = 0.4 ± 0.5%) were observed because of the body mass gain (approximately 300-400 g) after drinking. When using SBIA, assessments should be performed before resistance exercise to eliminate exercise-induced alterations in %BF. Conversely, resistance exercise had no effect on the LBIA measurements, and, therefore, following pretest exercise guidelines may not be necessary when this technology is used for the body composition assessment.