Objective: Shoulder and neck impairments are the most common symptoms in breast cancer survivors. Disturbances in motor control patterns of the cervical musculature may play a relevant role in breast cancer. Our aim was to analyze the differences in cervical muscle behavior between breast cancer survivors and healthy women during a functional upper limb task.
Design: A case-control cohort study was conducted. Electromyographic (EMG) activity from the sternocleidomastoid (SCM), upper trapezius (UT), and deltoid muscles was recorded in 15 breast cancer survivors and 15 matched controls. Root-mean-square EMG amplitude was calculated during a functional upper limb task.
Results: The repeated-measures analysis revealed significant differences between groups for EMG amplitude of the right UT (P < 0.01), left UT (P = 0.047), and right SCM (P < 0.05) muscles but not for the left SCM (P = 0.250) or both deltoid (left, P = 0.195; right, P = 0.401) muscles. Breast cancer survivors exhibited significant greater EMG amplitude for both UT muscles at 10 secs (both sides, P = 0.01), 60 secs (both sides, P < 0.05), and 120 secs (both sides, P < 0.05) and for the right SCM muscle at 10 secs (P = 0.009), 60 secs (P = 0.013), and 120 secs (P = 0.004) compared with controls. The intensity of shoulder pain had a significant effect on EMG amplitude of the affected UT muscle within breast cancer survivors.
Conclusions: The current study shows that breast cancer survivors exhibit greater activation of both UT and SCM muscles during an upper limb task compared with controls, which may contribute to the development of neck and shoulder impairments in this patient population.