Differences in Feedforward Trunk Muscle Activity in Subgroups of Patients With Mechanical Low Back Pain  Sheri P. Silfies, PT, PhD, Rupal Mehta, PT, MS, Sue S. Smith, PT, PhD, Andrew R. Karduna, PhD  Archives of Physical Medicine and Rehabilitation  Volume 90, Issue 7, Pages 1159-1169 (July 2009) DOI: 10.1016/j.apmr.2008.10.033 Copyright © 2009 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 1 Model of self-perturbation of the upper extremity used to evaluate response of trunk musculature. Archives of Physical Medicine and Rehabilitation 2009 90, 1159-1169DOI: (10.1016/j.apmr.2008.10.033) Copyright © 2009 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 2 Mean ± SD onset of each of trunk muscle relative to the anterior deltoid onset (0ms) for (A) control, (B) MLBP instability, and (C) MLBP noninstability groups. The horizontal line represents the end (50ms) of the feedforward period (−100ms to 50ms relative to anterior deltoid onset). Striped boxes represent muscles groups acting in a feedforward manner. Note the differences between the patterns and onset latency variability between groups. Archives of Physical Medicine and Rehabilitation 2009 90, 1159-1169DOI: (10.1016/j.apmr.2008.10.033) Copyright © 2009 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 3 Group pattern of trunk muscle onset latency (mean) relative to deltoid onset (0ms). Plot demonstrates the latency of the MLBP groups relative to the control group (shaded region). *Significant difference (P≤.007) between control and combined MLBP groups. §Significant difference between the instability and noninstability MLBP subgroups. Archives of Physical Medicine and Rehabilitation 2009 90, 1159-1169DOI: (10.1016/j.apmr.2008.10.033) Copyright © 2009 American Congress of Rehabilitation Medicine Terms and Conditions