The purpose of this study was to identify differences in flexion-relaxation outcomes in asymptomatic participants, with respect to both flexion-relaxation phenomenon (FRP) occurrence and spinal onset angles, as a function of posture and choice of muscle being examined.
This was a cross-sectional study in a laboratory setting. Thirty asymptomatic participants performed standing full trunk flexion and slumped sitting postures while activation levels of the lumbar erector spinae and superficial lumbar multifidus were monitored. Two thresholds were used to define whether FRP was present in each muscle and, if present, at what trunk flexion angle it occurred. These outcomes were compared descriptively between muscles and between postures.
Most participants displayed FRP in both muscles during standing full flexion; occurrences were more variable in slumped sitting. On average, FRP during standing full flexion and slumped sitting occurred at approximately 80% and 52% of participants' maximum flexion value, respectively. Variability in the slumped sitting onset angles was greater than that in standing full flexion.
Outcomes for FRP during standing full flexion in asymptomatic participants appeared to be more robust and were not affected by the choice of either lumbar erector spinae or superficial lumbar multifidus. Conversely, during slumped sitting, FRP occurrence varied substantially depending on choice of muscle, although onset angles were relatively consistent between muscles. Although the choice of one muscle over the other may be warranted, it may be prudent to examine both muscles during FRP investigations in sitting postures, in order to fully characterize the behavior and activation patterns of the lumbar musculature.
Key Indexing Terms
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Journal of Manipulative & Physiological Therapeutics
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- The function of erector spinae muscles in certain movements and postures in man.J Physiol. 1955; 129: 184-203
- Altered patterns of superficial trunk muscle activation during sitting in nonspecific chronic low back pain patients.Spine. 2006; 31: 2017-2023
- A meta-analytic review of surface electromyography among persons with low back pain and normal, healthy controls.J Pain. 2005; 6: 711-726
- Surface electromyography in the identification of chronic low back pain patients: the development of the flexion relaxation ratio.Clin Biomech. 1997; 12: 165-171
- The biomechanical and clinical significance of the lumbar erector spinae flexion-relaxation phenomenon: a review of literature.J Manipulative Physiol Ther. 2005; 28: 623-631
- Evaluation of methods for the quantification of the flexion-relaxation phenomenon in the lumbar erector spinae muscles.J Manipulative Physiol Ther. 2013; 36: 349-358
- Posture related to myoelectric silence of erectors spinae during trunk flexion.Spine. 1984; 9: 740-745
- Quantitative studies of the flexion-relaxation phenomenon in the back muscles.J Orthop Res. 1985; 3: 189-197
- Analyses of myo-electrical silence of erectors spinae.J Biomech. 2001; 34: 491-496
- Flexion-relaxation phenomenon in the back muscles. A comparative study between healthy subjects and patients with chronic low back pain.Am J Phys Med Rehabil. 1995; 74: 139-144
- Quantifying the lumbar flexion-relaxation phenomenon: theory, normative data, and clinical applications.Spine. 2003; 28: 1435-1446
- Comparison of lumbar paravertebral EMG patterns in chronic low back pain patients and non-patient controls.Pain. 1988; 34: 153-160
- Flexion-relaxation and clinical features associated with chronic low back pain: a comparison of different methods of quantifying flexion-relaxation.Clin J Pain. 2009; 25: 760-766
- Examination of the flexion relaxation phenomenon in erector spinae muscles during short duration slumped sitting.Clin Biomech. 2002; 17: 353-360
- Flexion-relaxation ratio in sitting: application in low back pain rehabilitation.Spine. 2010; 35: 1532-1538
- Paraspinal muscle function assessed with the flexion-relaxation ratio at baseline in a population of patients with back-related leg pain.J Manipulative Physiol Ther. 2011; 34: 594-601
- Modulation of the flexion-relaxation response by spinal manipulative therapy: a control group study.J Manipulative Physiol Ther. 2009; 32: 203-209
- Sitting postures and trunk muscle activity in adolescents with and without nonspecific chronic low back pain.Spine. 2010; 35: 1387-1395
- The effect of different standing and sitting postures on trunk muscle activity in a pain-free population.Spine. 2002; 27: 1238-1244
- Evaluation of the flexion relaxation phenomenon of the trunk muscles in sitting.Spine. 2006; 31: 2009-2016
- What is slumped sitting? A kinematic and electromyographical evaluation.Man Ther. 2013; 18: 498-505
- Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population.Spine. 2006; 31: E707-E712
- A myoelectrically based dynamic three-dimensional model to predict loads on lumbar spine tissues during lateral bending.J Biomech. 1992; 25: 395-414
- Repeated spinal flexion modulates the flexion-relaxation phenomenon.Clin Biomech. 2003; 18: 783-789
- Elimination of electrocardiogram contamination from electromyogram signals: an evaluation of currently used removal techniques.J Electromyogr Kinesiol. 2006; 16: 175-187
- Frequency response of spine extensors during rapid isometric contractions: effects of muscle length and tension.J Electromyogr Kinesiol. 1998; 8: 227-232
- Biomechanics and motor control of human movement.4th ed. John Wiley & Sons Inc., Hoboken2009
Published online: August 07, 2014
Accepted: January 17, 2014
Received in revised form: January 15, 2014
Received: January 25, 2013
© 2014 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.