Marshall, PWM, Desai, I, and Robbins, DW. Core stability exercises in individuals with and without chronic nonspecific low back pain. J Strength Cond Res 25(12): 3404–3411, 2011—The aim of this study was to measure trunk muscle activity during several commonly used exercises in individuals with and without low back pain (LBP). Abdominal bracing was investigated as an exercise modification that may increase the acute training stimulus. After an initial familiarization session, 10 patients with LBP and 10 matched controls performed 5 different exercises (quadruped, side bridge, modified push-up, squat, shoulder flexion) with and without abdominal bracing. Trunk muscle activity and lumbar range of motion (LROM) were measured during all exercises. Muscle activity was measured bilaterally during each exercise from rectus abdominis (RA), external obliques (EO), and lumbar erector spinae (ES) with pairs of surface electrodes. Recorded signals were normalized to a percentage of maximal voluntary contractions performed for each muscle. The ES activity was lower for the LBP group during the quadruped (p < 0.05) and higher for RA and EO during the side bridge (p < 0.001), compared to for the healthy controls. Higher muscle activity was observed across exercises in an inconsistent pattern when abdominal bracing was used during exercise. The LROM was no different between groups for any exercise. The lack of worsening of symptoms in the LBP group and similar LROM observed between groups suggest that all exercises investigated in this study are of use in rehabilitating LBP patients. The widespread use of abdominal bracing in clinical practice, whether it be for patients with LBP or healthy individuals, may not be justified unless symptoms of spinal instability are identified.