Andersen LL, Kjaer M, Andersen CH, Hansen PB, Zebis MK, Hansen K, Sjogaard G. Muscle activation during selected strength exercises in women with chronic neck muscle pain

Physical Therapy, June, 2008 by Eric K. Robertson

Andersen LL, Kjaer M, Andersen CH, Hansen PB, Zebis MK, Hansen K, Sjogaard G. Muscle Activation During Selected Strength Exercises in Women With Chronic Neck Muscle Pain. Phys Ther. 2008;88:703-711.

What problems did the researchers set out to study, and why?

The researchers investigated the level of activation of neck and shoulder muscles during select upper-extremity strengthening exercises. Specific strength training can be an important intervention in patients with chronic neck pain of muscular origin, and selecting exercises that both target specific muscles and allow patients with pain to perform the task is important.

Who participated in this study?

12 female workers identified as part of a large intervention study. Subjects had a clinical diagnosis of trapezius myalgia and were a subset of the strengthening group in the large intervention study. The subjects had been undergoing rehabilitation, including the exercises examined, for 8 to 10 weeks prior to this analysis.

What new information does this study offer?

The shrug, lateral raises, and upright row all resulted in a high level of trapezius muscle activation, with lateral raises and upright rows requiring smaller training loads during exercise. Most tasks analyzed resulted in high levels of muscle activation.

How did the researchers go about the study?

Measurements of muscle activation using surface electromyography (EMG) (upper trapezius, posterior, middle, and anterior deltoid muscles) were taken and normalized to maximal voluntary contraction. The movements analyzed were those used in the shrug, one-arm row, upright row, reverse fly, and lateral raise. Each task was performed using an 8-repetition maximum load. An analysis of variance was performed to identify any differences in muscle activation among the different tasks.

How might these results be applied to physical therapist practice?

The high levels of trapezius muscle activation observed during lateral raises and upright rows suggest that they may be useful alternative exercises to strengthen the trapezius in women with chronic trapezius myalgia. These tasks require lighter training loads to achieve a training effect and may be preferable to the classic shrug exercise. The high muscle activation noted among all motions indicates their suitability to be used in a strength-training program for chronic neck muscle pain.

What are the limitations of the study, and what further research is needed?

Surface EMG provides a gross estimate of muscle activation level. The subjects in this study were well trained in the tasks, so the impact of this training on muscle activation is not known. Further research is needed to identify muscle activation levels in untrained subjects as well as to determine if performing these alternative movements results in clinical improvements in patients with chronic neck pain.

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EK Robertson, PT, DPT, is Assistant Professor, Department of Physical Therapy, Medical College of Georgia.