www.elsevier.com/locate/math Manual Therapy 9 (2004) 89–94 Original article Impairment in the cervical flexors: a comparison of whiplash and insidious onset neck pain patients G. Jull a, *, E. Kristjansson b , P. Dall’Alba a a Department of Physiotherapy, The University of Queensland, Queensland 4072, Australia b The Faculty of Medicine, The University of Iceland, Reykjav ! ık, Iceland Received 22 August 2002; received in revised form 20 June 2003; accepted 30 June 2003 Abstract There has been little investigation into whether or not differences exist in the nature of physical impairment associated with neck pain of whiplash and insidious origin. This study examined the neck flexor synergy during performance of the cranio-cervical flexion test, a test targeting the action of the deep neck flexors. Seventy-five volunteer subjects participated in this study and were equally divided between Group 1, asymptomatic control subjects, Group 2, subjects with insidious onset neck pain and Group 3, subjects with neck pain following a whiplash injury. The cranio-cervical flexion test was performed in five progressive stages of increasing cranio-cervical flexion range. Subjects’ performance was guided by feedback from a pressure sensor inserted behind the neck which monitored the slight flattening of the cervical lordosis which occurs with the contraction of longus colli. Myoelectric signals (EMG) were detected from the muscles during performance of the test. The results indicated that both the insidious onset neck pain and whiplash groups had higher measures of EMG signal amplitude (normalized root mean square) in the sternocleidomastoid during each stage of the test compared to the control subjects (all Po0.05) and had significantly greater shortfalls from the pressure targets in the test stages (Po0.05). No significant differences were evident between the neck pain groups in either parameter indicating that this physical impairment in the neck flexor synergy is common to neck pain of both whiplash and insidious origin. r 2003 Elsevier Ltd. All rights reserved. Keywords: Neck flexors; Whiplash; Neck pain 1. Introduction Neck pain is a common condition causing substantial personal and financial costs (C # ot ! e et al., 1998; Holm- strom et al., 1992). Broadly, onset may be insidious or may follow trauma. Pain is often persistent or recurrent in nature. Neck pain of traumatic origin following a motor vehicle crash (whiplash) often poses a particular challenge in management. There are several influences that may impact on the perception of neck pain and disability in persons with whiplash associated disorders (WAD) compared to those with an insidious onset of neck pain. These include the magnitude of the injury, psychological responses to injury and pain, social factors and litigation (C # ot ! e et al., 2001; Radanov and Sturzenegger, 1996). There has been little investigation into whether or not differences exist in the nature of physical impairment associated with neck pain of whiplash and insidious origins which may contribute to the greater difficulty often encountered in the rehabilitation of patients with WAD. Changes in cervical flexor muscle function have been investigated in neck disorders of both whiplash and insidious origins. Vernon et al. (1992) in an initial comparative study of neck isometric strength and flexor/ extensor strength ratios, found that subjects with both WAD and insidious onset neck pain had lesser strength than asymptomatic subjects. There was a progressive anterior-to-posterior muscle imbalance in the neck pain subjects, with the cervical flexors becoming relatively weaker as compared to the extensors. This was more apparent in subjects with WAD, suggesting that there could be a difference in the degree of impairment between these subject groups. ARTICLE IN PRESS *Corresponding author. Tel.: +61-7-3365-2275; fax: +61-7-3365- 2775. E-mail address: g.jull@shrs.uq.edu.au (G. Jull). 1356-689X/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S1356-689X(03)00086-9