SUPERFICIAL NECK MUSCLE SYNERGY DURING HEAD RAISE EXERCISES IN INDIVIDUALS WITH CHRONIC NECK PAIN OF A TRAUMATIC AND NON-TRAUMATIC ONSET Curtis S.A. 1, Kallenberg L.A.C. 2 , Burridge J.H. 1 1 University of Southampton, Southampton, UK 2 Roessingh Research and Development, Enschede, The Netherlands E-mail: S.A.Curtis@southampton.ac.uk INTRODUCTION Chronic neck pain is the second most common musculoskeletal complaint following chronic back pain and poses a major problem for the healthcare sector1. It is accepted that pain can cause alterations to muscle control strategies, which are possibly employed to minimise the use of painful muscles2. Such alterations could be detrimental to the muscles that become under-used and to those where their use is increased in compensation. The use of superficial muscles could increase as a compensatory mechanism to avoid using painful, deeper structures. It is possible that overuse of superficial muscles could itself result in pain. Fatigue could also be a consequence of underuse and overuse of muscles. During a head raise activity the sternocleidomastoid muscles (SCMs) would be directly recruited whereas, the upper trapezius muscles (UTRPs) could be recruited to stabilise the head raise position when muscles directly involved become fatigued. Figure 3. RMS activity of the right sternocleidomastoid over 5 epochs Figure 4. RMS activity of the left sternocleidomastoid over 5 epochs METHOD Subjects with chronic neck pain of a traumatic onset (TO, n = 4), of a non-traumatic onset (NTO, n =13), and healthy controls (HC, n = 18) performed a head raise from a supine position, with cervical flexion, to a height of 1 – 1.25 cm (Figures 1 & 2) and maintained the position until fatigue resulted in the head dropping below the required height. Simultaneous recordings of the UTRPs and SCMs were obtained using 4-channel linear array electrodes. Root-mean-square (RMS) was estimated and changes over time, as well as differences between the groups, were investigated. Green light indicating that the head raise position is within the correct height range Figure 1. Head raise position within the 1.0 – 1.25 cm range Figure 5. RMS activity of the right upper trapezius over 5 epochs Figure 6. RMS activity of the left upper trapezius over 5 epochs CONCLUSIONS SCM activity did not differ significantly during the sustained head raise exercise between the groups. Increasing UTRP activity was seen in the HC and NTO groups, possibly to help stabilise the head raise position when the muscles directly involved became fatigued. These results could indicate that the recruited motor units in the UTRPs of the TO group were more fatigue resistant than those in the HC and NTO groups. The lower RMS values and reduced increase in these values in the right UTRP suggest that the TO group did not employ this muscle as much as the HC and NTO groups, possibly due to the muscle being painful or an increased reliance upon the flexor muscles in maintaining this position. The small TO group size mean the results should be interpreted with caution. Red light without the green light indicating that the head raise position has exceeded the correct height range Figure 2. Head raise position exceeding the 1.0 – 1.25 cm range RESULTS All groups showed increasing RMS values over time in the SCMs, with no significant differences or observable trends between the groups (Figures 3 & 4). The HC and NTO groups showed increasing activity of the UTRPs during the exercise (Figures 5 & 6). The TO group showed a trend for less of an increase in RMS values in the right UTRP (p<0.285) compared to the HC and NTO groups REFERENCES 1 Ferrari, R. & Russell, A. S. 2003, Neck Pain., Best Practice and Clinical Rheumatology, vol. 17, no. 1, pp. 57-70. 2 Falla, D.L., Jull, G.A. & Hodges, P.W. 2004, Patients with neck pain demonstrate reduced electromyographic activity of the deep cervical flexor muscles during performance of the craniocervical flexion test., Spine vol.29, pp. 2108–2114.