Archives of Physical Medicine and Rehabilitation journal homepage: www.archives-pmr.org Archives of Physical Medicine and Rehabilitation 2014;95:1006-8
DEPARTMENTS Letters to the Editor Trunk Muscle Activation in the Low BackeInjured Population We observed with interest the recent publication by Moreside et al.1 The authors examined muscle activation using surface electromyography to compare patients with and without a history of low back injury. They consider in their conclusion the potential application of these measures to objectively determine healing in the clinical population. Although the authors clearly have used this statistical model in previous publications to compare their electromyographic findings between groups, there are factors impeding the application of this data to clinical populations. First, although surface electromyography is well studied as a research tool, it has a number of drawbacks that may preclude widespread clinical application. For example, surface electromyography cannot reliably target the activity of specific muscles, such as the multifidus.2 Furthermore, there is a lack of consistent and standardized electromyographic protocols, which make comparison of studies difficult. It has also been shown that the interoperator and between-session reproducibility of surface electromyographic data is contentious.3 Second, the authors’ description of low back injury is poorly defined. Based on the methodologic description, it appears the patients had some version of a lumbar sprain/strain, which could include a wide variety of diagnoses and pain generators whether it is bone, ligament, or muscle injury. It is a widely held concept that soft tissues generally follow a predictable time course of healing, which forms the basis for the treatment and rehabilitation of most soft tissue injuries. Moreover, the physiological mechanisms within injured muscle after disuse can certainly affect the results of the surface electromyographic findings.4 Importantly, the authors highlight the difference in age between the groups compared and speculate on the role of the passive tissue structural properties. Furthermore, the potential role of low back pain on muscle activation in the injury group cannot be excluded as the authors have noted in their discussion. Third, the patient’s perception of recovery can be affected by a multitude of factors. Specifically, it is not mentioned whether the patients in the low back injury group suffered their injury at work or during leisure activity. It is also not clear whether the low back injury group had physiotherapy or returned to normative activity in 12 weeks after the injury. Despite the authors’ contention that the subjects in this study may not be fully healed, objectively they make no mention of their function. Therefore, notwithstanding the authors’ electromyographic findings of altered trunk muscle
activation, which may represent impairment, the translation to disability or risk for reinjury is not straightforward.5 Indeed, there is no disability conferred on these patients who are returning to work despite what the surface electromyography demonstrates. We commend the authors for their hard work in data collection; however, in the future, more consideration needs to be given to the inclusion criteria of patients with low back injury to create a homogeneous sample. Furthermore, the consideration of this method as a clinical tool has implications for the occupational medicine and rehabilitation communities and the use of this concept to predict an impairment that translates to disability needs to be established. W. Shane Journeay, MD, PhD Dinesh Kumbhare, MD, MSc, FRCPC Division of Physical Medicine and Rehabilitation Department of Medicine University of Toronto Toronto, ON, Canada Disclosure: No commercial party having a direct financial interest in the results of the research supporting this letter has conferred or will confer a benefit on the authors or on any organization with which the authors are associated.
References 1. Moreside JM, Quirk DA, Hubley-Kozey CL. Temporal patterns of the trunk muscles remain altered in a low back-injured population despite subjective reports of recovery. Arch Phys Med Rehabil 2014;95:686-98. 2. Stokes IA, Henry SM, Single RM. Surface EMG electrodes do not accurately record from lumbar multifidus muscles. Clin Biomech 2003;18:9-13. 3. Danneels LA, Cagnie BJ, Cools AM, et al. Intra-operator and interoperator reliability of surface electromyography in the clinical evaluation of back muscles. Man Ther 2001;6:145-53. 4. Mannion AF, Dumas GA, Stevenson JM, Cooper RG. The influence of muscle fiber size and type distribution on electromyographic measures of back muscle fatigability. Spine (Phila Pa 1976) 1998;23:576-84. 5. Katz M. Impairment and disability rating in low back pain. Phys Med Rehabil Clin N Am 2001;12:681-94. http://dx.doi.org/10.1016/j.apmr.2014.01.032
The Author Responds We thank Drs. Journeay and Kumbhare for their comments and for the opportunity to clarify the points they raise in their letter to the
0003-9993/14/$36 - see front matter Ó 2014 by the American Congress of Rehabilitation Medicine
DEPARTMENTS Letters to the Editor Trunk Muscle Activation in the Low BackeInjured Population We observed with interest the recent publication by Moreside et al.1 The authors examined muscle activation using surface electromyography to compare patients with and without a history of low back injury. They consider in their conclusion the potential application of these measures to objectively determine healing in the clinical population. Although the authors clearly have used this statistical model in previous publications to compare their electromyographic findings between groups, there are factors impeding the application of this data to clinical populations. First, although surface electromyography is well studied as a research tool, it has a number of drawbacks that may preclude widespread clinical application. For example, surface electromyography cannot reliably target the activity of specific muscles, such as the multifidus.2 Furthermore, there is a lack of consistent and standardized electromyographic protocols, which make comparison of studies difficult. It has also been shown that the interoperator and between-session reproducibility of surface electromyographic data is contentious.3 Second, the authors’ description of low back injury is poorly defined. Based on the methodologic description, it appears the patients had some version of a lumbar sprain/strain, which could include a wide variety of diagnoses and pain generators whether it is bone, ligament, or muscle injury. It is a widely held concept that soft tissues generally follow a predictable time course of healing, which forms the basis for the treatment and rehabilitation of most soft tissue injuries. Moreover, the physiological mechanisms within injured muscle after disuse can certainly affect the results of the surface electromyographic findings.4 Importantly, the authors highlight the difference in age between the groups compared and speculate on the role of the passive tissue structural properties. Furthermore, the potential role of low back pain on muscle activation in the injury group cannot be excluded as the authors have noted in their discussion. Third, the patient’s perception of recovery can be affected by a multitude of factors. Specifically, it is not mentioned whether the patients in the low back injury group suffered their injury at work or during leisure activity. It is also not clear whether the low back injury group had physiotherapy or returned to normative activity in 12 weeks after the injury. Despite the authors’ contention that the subjects in this study may not be fully healed, objectively they make no mention of their function. Therefore, notwithstanding the authors’ electromyographic findings of altered trunk muscle
activation, which may represent impairment, the translation to disability or risk for reinjury is not straightforward.5 Indeed, there is no disability conferred on these patients who are returning to work despite what the surface electromyography demonstrates. We commend the authors for their hard work in data collection; however, in the future, more consideration needs to be given to the inclusion criteria of patients with low back injury to create a homogeneous sample. Furthermore, the consideration of this method as a clinical tool has implications for the occupational medicine and rehabilitation communities and the use of this concept to predict an impairment that translates to disability needs to be established. W. Shane Journeay, MD, PhD Dinesh Kumbhare, MD, MSc, FRCPC Division of Physical Medicine and Rehabilitation Department of Medicine University of Toronto Toronto, ON, Canada Disclosure: No commercial party having a direct financial interest in the results of the research supporting this letter has conferred or will confer a benefit on the authors or on any organization with which the authors are associated.
References 1. Moreside JM, Quirk DA, Hubley-Kozey CL. Temporal patterns of the trunk muscles remain altered in a low back-injured population despite subjective reports of recovery. Arch Phys Med Rehabil 2014;95:686-98. 2. Stokes IA, Henry SM, Single RM. Surface EMG electrodes do not accurately record from lumbar multifidus muscles. Clin Biomech 2003;18:9-13. 3. Danneels LA, Cagnie BJ, Cools AM, et al. Intra-operator and interoperator reliability of surface electromyography in the clinical evaluation of back muscles. Man Ther 2001;6:145-53. 4. Mannion AF, Dumas GA, Stevenson JM, Cooper RG. The influence of muscle fiber size and type distribution on electromyographic measures of back muscle fatigability. Spine (Phila Pa 1976) 1998;23:576-84. 5. Katz M. Impairment and disability rating in low back pain. Phys Med Rehabil Clin N Am 2001;12:681-94. http://dx.doi.org/10.1016/j.apmr.2014.01.032
The Author Responds We thank Drs. Journeay and Kumbhare for their comments and for the opportunity to clarify the points they raise in their letter to the
0003-9993/14/$36 - see front matter Ó 2014 by the American Congress of Rehabilitation Medicine
