The twofold purposes of this investigation were: to determine the reliability and validity of two noninvasive methods for determining anaerobic threshold (AT) and; to examine the effect of an aerobic training program on the AT. Twelve sedentary, overweight women participated in an 8 wk walk/jog program 3 dâ ¢wk⁻¹ at 70% VO_2max with a concurrent hypocaloric diet. A computerized polynomial regression and four independent reviewers were used in an attempt to decrease the subjectivity of noninvasive AT estimation from data plots. Duplicate plots allowed determination of intra-reviewer variability for AT_FEO2 and AT_VE/VO2 estimation. All reviewers fell within the 2-10% variability range accepted for research and clinical purposes, respectively.