Effect of sling exercise therapy on surface electromyography and muscle thickness of superficial cervical muscle groups in female patients with chronic neck pain

Abstract

BACKGROUND:

The persistence of symptoms in patients with chronic neck pain is considered to be associated with variation in the neck muscle structure and associated neuromuscular control. Sling exercise therapy (SET) has been demonstrated to relieve the symptoms of chronic neck pain, whereas it is controversial whether this benefit is correlated to altered neck muscle structure and associated neuromuscular control in the patients.

OBJECTIVE:

To investigate the effect of SET on cervical muscle structure (thickness) and associated neuromuscular control in patients with chronic neck pain.

METHODS:

Twenty-five patients with chronic neck pain were randomly assigned to the SET group ( $n=$ 12) or the control group ( $n=$ 13). The SET group received the SET intervention for 4 weeks, while the control group maintained normal activities of daily living. At baseline and after 4 weeks of intervention, Visual analogue scale and neck disability index were measured in both groups, and changes in the thickness of the superficial cervical muscles were assessed using musculoskeletal ultrasound. Surface electromyography (EMG) was adapted to assess the neuromuscular control of the neck while the participant was performing the cranio-cervical flexion test.

RESULTS:

At 4 weeks, the SET group had a significant reduction of RMS in both UT and SCM of EMG compared to the control group ( $p<$ 0.05). Regarding ultrasound, the SET group had significantly lower muscle thickness compared to the control group in both the rest position and the MVIC position ( $p<$ 0.05). There were no within-group differences in the control group ( $p>$ 0.05), while the SET group showed significant reductions in both RMS and muscle thickness ( $p<$ 0.05).

CONCLUSION:

4-week SET was effective in reducing pain and dysfunction in patients with chronic neck pain, which may be related to improved neck muscle thickness and neuromuscular control of the neck.