title: Electromyographic activity of the trunk stabilizers during stable and unstable bench press.
abstract: The purpose of this study was to investigate the effectiveness of instability training in the recruitment of core stabilizing muscles during dynamic multijoint movement. Surface electromyography (EMG) was measured from 6 muscles (latissimus dorsi, rectus abdominus, internal obliques, erector spinae, and soleus) while subjects performed a 9.1-kg bench press on stable and unstable surfaces. There were 4 exercises in total: (a) stable surfaces for shoulders and feet, (b) upper-body instability, (c) lower-body instability, and (d) dual instability. Five seconds of EMG were recorded during each bench press and were subsequently smoothed with root mean squares calculated for the entire time-series. A repeated-measures analysis of variance (ANOVA) was used to test overall differences between exercise conditions for each muscle. Paired equal variance t-tests with a stepwise Bonferroni correction for multiple contrasts (alpha = 0.05/total number of contrasts) were performed for muscles with significant repeated-measures ANOVA results. The results show significant increases in EMG with increasing instability. Specifically, the dual instability bench press resulted in the greatest mean muscle activation of the 3 stability conditions, with single instability conditions being significantly greater than the stable condition. This pattern of results is consistent with the position that performing the bench press in a progressively unstable environment may be an effective method to increase activation of the core stabilizing musculature, while the upper- and lower-body stabilizers can be activated differentially depending on the mode of instability.
authors.affiliation: University College of the Fraser Valley, Abbotsford, British Columbia, Canada.
authors.forename: Jeff T
authors.initials: JT
authors.lastname: Norwood
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Anderson
authors.forename: Michael B
authors.initials: MB
authors.lastname: Gaetz
authors.forename: Peter W
authors.initials: PW
authors.lastname: Twist
mesh_terms: D000009:Abdominal Muscles / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D013909:Thorax / Q000502:physiology*; D014891:Weight Lifting / Q000502:physiology*