Activation of the semispinalis cervicis and splenius capitis with cervical pulley exercises

Highlights

• Neck extensor activation changes with the line of resistance during exercise.

• A more vertical line of action was preferable during cervical extension.

• A declined pulley was superior during cervical rotation.

• The results provide guidance for exercise design for patients with neck disorders.

Abstract

Study design

Quasi-Experimental.

Objective

To assess the activation of semispinalis cervicis (d-SSC) and splenius capitis (s-SC) muscles, and the activation between the two during neck pulley and free weight exercises.

Background

Altered activation of cervical extensors may occur with neck pain, suggesting that exercises should be designed to target these muscles.

Methods

d-SSC and s-SC activity was recorded unilaterally with intramuscular electromyography from healthy volunteers during cervical isometric exercises: 1) extension with a pulley rope angled from incline to vertical, 2) extension with right, left and central forehead hanging weight, and 3) rotation with pulley rope angled from incline to decline.

Results

Extension against a vertical force led to greater activation of d-SSC (P < 0.001) and s-SC (P < 0.001) compared to the inclined, declined and horizontal pulley. With each of these conditions, amplitude of muscle activity was higher for the d-SSC compared to the s-SC muscle (P < 0.0001). Extension with free weight hanging on right, left or central forehead, showed no differences across conditions, although in each condition, the d-SSC amplitude was higher than the s-SC. For cervical rotation, the declined pulley led to the greatest activation of both muscles (P < 0.05). Higher levels of activity were observed for the s-SC compared to the d-SSC (P < 0.01) for all rotation conditions.

Conclusion

A vertical resistance during an extension exercise or a declined resistance during cervical rotation, increased neck extensor activation. The results from this preliminary study provide guidance for future work on the exploration and development of low-load exercise design for patients with neck pain disorders.

Introduction

People with chronic neck pain display changes in the behavior and structure of their neck muscles (Cagnie et al., 2008, Elliott et al., 2006, Elliott et al., 2011, Elliott et al., 2008, O'Leary et al., 2003, Schomacher et al., 2013, Schomacher and Falla, 2013, Schomacher et al., 2012a). Our recent work has revealed reduced activation of the deep cervical extensor muscle, semispinalis cervicis (d-SSC) in people with chronic neck pain disorders (Schomacher et al., 2013, Schomacher and Falla, 2013, Schomacher et al., 2012a). Moreover, atrophy (Elliott et al., 2008, Elliott et al., 2014) and fatty infiltration (Abbott et al., 2015, Elliott et al., 2006, Elliott et al., 2011, Elliott et al., 2015, Karlsson et al., 2016) of the deep cervical extensors have been observed in both non-traumatic and traumatic neck disorders, respectively. Thus, exercise which targets and facilitates the activation of the deep cervical extensors may be relevant for people with neck pain to improve the activation of their neck muscles with the aim of gaining long term pain relief and improved function (O'Leary et al., 2003). A recent clinical trial revealed that participation in a neck-specific exercise program was the only significant factor associated with both neck pain and neck disability reduction at 3 and 12 months in a cohort of patients with whiplash associated disorders (Ludvigsson et al., 2016). Patients who performed a neck-specific exercise program had up to 5.3 times higher odds of disability reduction, and 3.9 times higher odds of pain reduction compared to those in a physical activity group. These findings provide the incentive to identify selective and specific exercises to address neuromuscular impairments in people with neck pain.

Few studies have investigated whether specific exercise can facilitate activation of the deep cervical extensor muscles. One magnetic resonance imaging study showed differing muscle activation when the head was in craniocervical extension compared to a neutral head position (Elliott et al., 2010). An electromyography (EMG) study showed that the activation of d-SSC increased relative to the superficial splenius capitis (s-SC) when manual resistance was applied over the vertebral arch versus the occiput (Schomacher et al., 2012b). However, these exercises are limited in their application, as it is difficult to grade the exercise and apply additional resistance as training progresses.

A pulley apparatus or hanging weights allow for the design of exercises with resistance applied at any angle/direction (Faugli, 1996, Grimsby and Rivard, 2008). It is theorized that specific muscles can be activated during exercises to allow for more targeted muscle activation without the patient having to cognitively participate (Grimsby and Rivard, 2008). This approach may provide a more effective way to facilitate activation of the deeper extensor muscles, especially since the load and direction of resistance can be adjusted. Peolsson et al. (2013) compared cervical extension exercises between a guild board and a pulley using ultrasound measurements of muscle deformation and deformation rate, but did not include varying angles of the pulley or the guild board. Performing the exercise on the guild board produced higher levels of deformation and deformation rates of the cervical extensors, however, differences between superficial and deep muscle deformation were not investigated.

This quasi-experimental study aimed to assess changes in activation of the d-SSC and s-SC, as well as relative activation between the two muscles during neck exercises using a pulley resistance and a free hanging weight. The following hypotheses were tested. 1: as the line of action from the pulley changed from an inclined to a more vertical position during cervical extension, a more declined line of action would increase the relative flexion torque, increasing activation of the d-SSC and s-SC. 2: a non-centrally placed vertical resistance during cervical extension, which would add a lateral flexion torque, and would enhance activation of the contralateral d-SSC and s-SC. 3: activity of the d-SSC and s-SC would be enhanced during a rotation exercise using a more declined line of action from a pulley, creating a flexion torque on the cranium. Finally, these specific approaches would induce a relatively greater activation of the d-SSC given the low load and specific nature of the exercises.