ASSESSING BODY-COMPOSITION BEFORE AND AFTER RESISTANCE OR ENDURANCE TRAINING

This study's purpose was to determine the validity of near-infrared in teractance (NIR) and bioelectric impedance (BIA) in tracking changes i n body composition over 12 wk of either a high intensity endurance (ET ) or resistance (RT) training program in nondieting weight-stable untr ained males. Prior to and following the control or training period, ea ch subject completed a series of body composition analyses including h ydrostatic weighing (HW) with a measurement of residual volume; anthro pometric measurements including height, weight, skinfold, and girth; B IA measurement; and NIR measurements. Based on the HW results, there w ere no significant body composition changes in the control group. For the ET group, a significant decline in relative body fat resulted from a reduction in fat weight (FW) with no change in fat-free weight (FFW ). In the RT group, both a significant decline in FW and an increase i n FFW contributed to this group's decline in relative body fat. Tracki ng changes in relative body fat, FW, and FFW, skinfolds agreed reasona bly well with HW in all groups while BIA and NIR did not always track body composition changes well. For example, SF and BIA were significan tly correlated with the changes in FFW (HW = + 4.1%, SF = + 4.5%, BIA = + 3.1%, NIR = - 0.7%) observed in the RT group compared to HW (SF: r -value = 0.45, SEE = 2.5; BIA: r = 0.33, SEE = 3.4) while the NIR meas urements were nonsignificant (r = 0.09, SEE = 5.0). Interestingly, NIR underestimated the gain in FFW in the resistance trained group while BIA underestimated the changes in relative body fat, FW, and FFW in th e endurance trained group. Based on these results. BIA and NIR appear not to be appropriate measurement tools for tracking body composition changes in endurance and resistance training individuals respectively.