ORIGINAL RESEARCH Effect of static neck flexion in cervical flexion-relaxation phenomenon in healthy males and females Roghayeh Mousavi-Khatir, PT PhD (candidate) a , Saeed Talebian, PT PhD a, *, Nader Maroufi, PT PhD b , Gholam Reza Olyaei, PT PhD a a Department of Physical Therapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran b Department of Physical Therapy, School of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran Received 15 February 2015; received in revised form 23 June 2015; accepted 22 July 2015 KEYWORDS Flexion-relaxation phenomenon; Neck pain; Cervical spine; Electromyography Summary Introduction: Neck pain is a common musculoskeletal disorder, especially among skilled workers who must keep their necks in a flexed position frequently during the day. The present study investigated changes in cervical flexion-relaxation phenomenon parameters after sustained neck flexion. Methods: The participants were 40 healthy subjects grouped by gender (20 females, 20 males). They were exposed to static neck flexion at the full angle of cervical flexion for 10 min. Each sub- ject underwent three trials of cervical flexion and re-extension before and after this period. Dif- ferences in onset and cessation angle of flexion-relaxation phenomenon, maximum neck flexion angle, amplitude of neck muscle activation and flexion-relaxation ratio were evaluated. Results: The maximum neck flexion angle significantly increased after sustained flexion. The onset of flexion-relaxation was significantly delayed during flexion, but cessation angle re- mained unchanged. Myoelectric activity of the cervical erector spinae muscles increased signif- icantly after maintaining flexion, especially in female subjects. The flexion-relaxation ratio also decreased significantly. Conclusion: It was concluded that 10 min of static flexion results in a delay in flexion-relaxation phenomenon and a shortened silence period. Also the cervical erector spinae muscles are * Corresponding author. Department of Physical Therapy, Rehabilitation faculty, Tehran University of Medical Sciences, Pich Shemiran, Tehran, Po Box: 1148965141, Iran. Tel.: þ98 21 77685088. E-mail addresses: r-mousavi@razi.tums.ac.ir (R. Mousavi-Khatir), talebian@sina.tums.ac.ir (S. Talebian), maroufi.n@iums.ac.ir (N. Maroufi), olyaeigh@sina.tums.ac.ir (G.R. Olyaei). + MODEL Please cite this article in press as: Mousavi-Khatir, R., et al., Effect of static neck flexion in cervical flexion-relaxation phenomenon in healthy males and females, Journal of Bodywork & Movement Therapies (2015), http://dx.doi.org/10.1016/j.jbmt.2015.07.039 http://dx.doi.org/10.1016/j.jbmt.2015.07.039 1360-8592/ª 2015 Elsevier Ltd. All rights reserved. Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/jbmt Journal of Bodywork & Movement Therapies (2015) xx,1e8