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Author Response

Cynthia Holzman Weppler
DOI: 10.2522/ptj.2010.90.6.962.2 Published 1 June 2010
Cynthia Holzman Weppler
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I am pleased that you have taken the time to read our perspective article1 thoughtfully, and I appreciate your comments and question regarding contract/relax stretching.

The primary intent of our perspective article was to introduce the concept that increases in muscle extensibility observed after stretching can be due to modified sensation. This concept alone has profound implications regarding assessment of muscle extensibility and in understanding the biomechanical effects of stretching. While researching this topic, I found that there are a number of theories regarding muscle extensibility and stretching that are widely accepted as conventional wisdom but that are not supported by experimental evidence. Therefore, another underlying purpose of our article was to show how little basic research has been performed regarding these topics. What is presented in the perspective article is, to the best of my knowledge, accurate at this point in time. As with any scientific endeavor, as research continues, more evidence will likely come to light that will refine the ideas presented. I consider our article to be successful if it: (1) causes practitioners to question prevailing conventional wisdom, (2) encourages debate, and (3) inspires more research that helps to further understanding of these phenomena.

The neuromuscular relaxation section was written to show that increases in muscle extensibility can occur without any evidence of neuromuscular relaxation. We did not attempt to explain the biomechanical effect of contract/relax stretching in detail because this was not the focus of the article. However, we also did not intend to give the impression that all increases in muscle extensibility observed during contract/relax stretching are solely due to modified sensation.

I agree that, during performance of contract/relax stretching, a decreased resistance to stretch is palpable shortly after the isometric contraction is released. This decreased resistance has most often been attributed to neuromuscular relaxation. The experimental evidence available at this point in time, however, suggests instead that the decreased resistance is due to viscoelastic rather than neuromuscular relaxation.2,3

There are a number of studies that monitored electromyographic activity during contract/relax stretching and showed no evidence that neuromuscular relaxation was responsible for the observed increases in muscle extensibility.4–8 These studies evaluated several different stretching methods, and some authors6–8 observed that the greatest increases in muscle extensibility occurred with the stretching techniques that induced the greatest increases in electromyographic activity. All of these studies4–8 questioned the traditional explanation that increases in muscle extensibility observed during contract/relax stretching (as well as stretches involving contraction of antagonist muscles) are due to neuromuscular relaxation induced by neuromuscular reflexes.

To my knowledge, there is only one study that additionally monitored passive torque during application of contract/relax stretching.2 That study was cited in our perspective article, and its results suggest that increases in extensibility (using subjects’ perception of pain onset as an endpoint) observed during contract/relax stretching can be attributed to both (1) temporary increases in muscle length (as illustrated in Fig. 1 of our article) due to viscoelastic deformation and (2) modified sensation (as illustrated in Fig. 2 of our article). The intent of the study by Magnusson et al2 was to examine the differences in electromyographic activity, passive torque, and stretch perception between a static stretch and a contract/relax stretch. During both the static stretch and contract/relax stretch conditions, muscles demonstrated: (1) viscoelastic stress relaxation of similar magnitude while being held in the initial stretched position and (2) a similar right shift of the torque/angle curves observed during the subsequent stretch application. Greater increases in muscle extensibility, however, were observed when subjects performed the contract/relax stretch versus the static stretch. The increases in extensibility that occurred in excess of those demonstrated with the static stretch could be attributed to modified sensation.

In clinical practice, the contract/relax stretch usually is repeated 3 to 5 times, allowing increasing end-range joint angles with each repetition. Magnusson and colleagues’ experiment2 was conducted using a single contract/relax stretch, and it would be valuable to see what occurs biomechanically when this technique is applied multiple times, as in clinical practice.

Magnusson and colleagues’ study2 was performed using hamstring muscles of male subjects who were healthy and asymptomatic. The biomechanical effect may vary in different muscles and subject groups. It is possible that neuromuscular relaxation may play a role in increasing the efficacy of contract/relax stretching in subjects diagnosed with neurological impairments or in subjects who are symptomatic, but, to my knowledge, this has not been shown experimentally. The isometric contraction itself may help to decrease pain in symptomatic muscles, further enhancing the increases in extensibility and reducing muscle guarding.

Thank you for your interest, comments, and question. I appreciate this opportunity to discuss the biomechanical effect of contract/relax stretching in some detail. Dr Magnusson and I chose to submit a correction, in part, to present this topic with more precision in the perspective article. The correction appears in the April issue of PTJ and can be found at: http://ptjournal.apta.org/cgi/content/full/90/4/647.

Footnotes

  • This letter was posted as a Rapid Response on April 13, 2010, at ptjournal.apta.org.

    • © 2010 American Physical Therapy Association

    References

    1. ↵
      1. Weppler CH,
      2. Magnusson SP
      . Increasing muscle extensibility: a matter of increasing length or modifying sensation? Phys Ther. 2010;90:438–449.
      OpenUrlAbstract/FREE Full Text
    2. ↵
      1. Magnusson SP,
      2. Simonsen EB,
      3. Aagaard P,
      4. et al
      . Mechanical and physical responses to stretching with and without preisometric contraction in human skeletal muscle. Arch Phys Med Rehabil. 1996;77:373–378.
      OpenUrlCrossRefPubMedWeb of Science
    3. ↵
      1. Chalmers G
      . Re-examination of the possible role of Golgi tendon organ and muscle spindle reflexes in proprioceptive neuromuscular facilitation muscle stretching. Sports Biomech. 2004;3:159–183.
      OpenUrlCrossRefPubMed
    4. ↵
      1. Condon SM,
      2. Hutton RS
      . Soleus muscle electromyographic activity and ankle dorsiflexion range of motion during four stretching procedures. Phys Ther. 1987;67:24–30.
      OpenUrlAbstract/FREE Full Text
    5. ↵
      1. Mitchell UH,
      2. Myrer JW,
      3. Hopkins JT,
      4. et al
      . Neurophysiological reflex mechanisms’ lack of contribution to the success of PNF stretches. J Sport Rehabil. 2009;18:343–357.
      OpenUrlPubMedWeb of Science
    6. ↵
      1. Moore MA,
      2. Hutton RS
      . Electromyographic investigation of muscle stretching techniques. Med Sci Sports Exerc. 1980;12:322–329.
      OpenUrlPubMedWeb of Science
    7. ↵
      1. Osternig LR,
      2. Robertson R,
      3. Troxel R,
      4. Hansen P
      . Muscle activation during proprioceptive neuromuscular facilitation (PNF) stretching techniques. Am J Phys Med. 1987;66:298–307.
      OpenUrlPubMedWeb of Science
    8. ↵
      1. Osternig LR,
      2. Robertson RN,
      3. Troxel RK,
      4. Hansen P
      . Differential responses to proprioceptive neuromuscular facilitation (PNF) stretch techniques. Med Sci Sports Exerc. 1990;22:106–111.
      OpenUrlPubMedWeb of Science
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    Vol 96 Issue 12 Table of Contents
    Physical Therapy: 96 (12)

    Issue highlights

    • Musculoskeletal Impairments Are Often Unrecognized and Underappreciated Complications From Diabetes
    • Physical Therapist–Led Ambulatory Rehabilitation for Patients Receiving CentriMag Short-Term Ventricular Assist Device Support: Retrospective Case Series
    • Education Research in Physical Therapy: Visions of the Possible
    • Predictors of Reduced Frequency of Physical Activity 3 Months After Injury: Findings From the Prospective Outcomes of Injury Study
    • Use of Perturbation-Based Gait Training in a Virtual Environment to Address Mediolateral Instability in an Individual With Unilateral Transfemoral Amputation
    • Effect of Virtual Reality Training on Balance and Gait Ability in Patients With Stroke: Systematic Review and Meta-Analysis
    • Effects of Locomotor Exercise Intensity on Gait Performance in Individuals With Incomplete Spinal Cord Injury
    • Case Series of a Knowledge Translation Intervention to Increase Upper Limb Exercise in Stroke Rehabilitation
    • Effectiveness of Rehabilitation Interventions to Improve Gait Speed in Children With Cerebral Palsy: Systematic Review and Meta-analysis
    • Reliability and Validity of Force Platform Measures of Balance Impairment in Individuals With Parkinson Disease
    • Measurement Properties of Instruments for Measuring of Lymphedema: Systematic Review
    • myMoves Program: Feasibility and Acceptability Study of a Remotely Delivered Self-Management Program for Increasing Physical Activity Among Adults With Acquired Brain Injury Living in the Community
    • Application of Intervention Mapping to the Development of a Complex Physical Therapist Intervention
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    Cynthia Holzman Weppler
    Physical Therapy Jun 2010, 90 (6) 962-963; DOI: 10.2522/ptj.2010.90.6.962.2

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    Author Response
    Cynthia Holzman Weppler
    Physical Therapy Jun 2010, 90 (6) 962-963; DOI: 10.2522/ptj.2010.90.6.962.2
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    Subjects

    • Intervention
      • Therapeutic Exercise
    • Musculoskeletal System/Orthopedic
      • Kinesiology/Biomechanics
      • Anatomy and Physiology: Musculoskeletal System

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