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Effect of Muscle Activity on Neck Pain after Whiplash

It makes sense that patients with neck pain can't relax the muscles around the neck and shoulders. This study shows that it's more than just a problem with relaxation. The muscles have increased activity at rest. There's also increased muscle activity while doing tasks using the arms.

Previous studies have shown changes in muscle activity for the upper trapezius (UT) muscle in subjects with neck pain. The UT muscle goes from the back of the neck down and across to the top of the shoulder.

This study shows that more than just the UT muscle is involved. The sternocleidomastoid (SCM) and anterior scalene (AS) muscles are also affected. These two muscles help bend or flex the head and neck forward.

EMG tests were used to measure the electrical activity of each muscle during a specific task. Three groups of patients were tested: 1) 10 patients with a history of neck pain of unknown cause; 2) 10 patients with a whiplash-associated disorder; and 3) 10 patients with no neck problems or injury (the control group).

The authors report their findings for each group alone. They also compare the results of each group to the other two groups. Overall, the authors found increased EMG activity for the SCM and AS muscles on both sides in the patients with neck pain. Increased activity in the left UT muscle was also found. The control group had the opposite results, with most activity recorded in the right UT muscle.

The authors suggest some reasons for these findings. But they say that further study is needed to understand these changes.

References: Deborah Falla, PT, BPhty (Hons), PhD, et al. Patients with Chronic Neck Pain Demonstrate Altered Patterns of Muscle Activation During Performance of a Functional Upper Limb Task. In Spine. July 1, 2004. Vol. 29. No. 13. Pp. 1436-1440.

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