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Youdas, JW, Guck, BR, Hebrink, RC, Rugotzke, JD, Madson, TJ, and Hollman, JH. An electromyographic analysis of the Ab-Slide exercise, abdominal crunch, supine double leg thrust, and side bridge in healthy young adults: implications for rehabilitation professionals. J Strength Cond Res 22(6): 1939-1946, 2008-The purpose of this study was to examine the effectiveness of a commercial abdominal machine (Ab-Slide) and three common abdominal strengthening exercises (abdominal crunch, supine double leg thrust, and side bridge) on activating abdominal and minimizing extraneous (nonabdominal) musculature-namely, the rectus femoris muscle. We recruited 10 males and 12 females whose mean (± SD) percent body fat was 10.7 ± 4 and 20.7% ± 3.2%, respectively. Electromyographic (EMG) data were recorded using surface electrodes for the rectus abdominis, external oblique, internal oblique, and rectus femoris. We recorded peak EMG activity for each muscle during each of the four exercises and normalized the EMG values by maximum muscle contractions (% MVIC). A two-factor repeated-measures analysis of variance assessed differences in normalized EMG activity among the different exercise variations (p < 0.05). Post hoc analyses were performed using the Bonferroni-adjusted α to assess between-exercise pair comparisons (p < 0.002). Gender did not affect performance; hence, data were collapsed across gender. We found a muscle × exercise interaction (F9,189 = 5.2, p < 0.001). Post hoc analyses revealed six pairwise differences. The Ab-Slide elicited the greatest EMG activity for the abdominal muscles and the least for the rectus femoris. The supine double leg thrust could be a problem for patients with low-back pathology due to high rectus femoris muscle activity.