A novel method for neck coordination exercise – a pilot study on persons with chronic non-specific neck pain
From: J Neuroeng Rehabil. 2008 Dec 23;5(1):36. [Epub ahead of print]
Chronic neck pain is a common problem and is often associated with changes in sensorimotor functions, such as reduced proprioceptive acuity of the neck, altered coordination of the cervical muscles, and increased postural sway. In line with these findings there are studies supporting the efficacy of exercises targeting different aspects of sensorimotor function, for example training aimed at improving proprioception and muscle coordination. To further develop this type of exercises we have designed a novel device and method for neck coordination training. The aim of the study was to investigate the clinical applicability of the method and to obtain indications of preliminary effects on sensorimotor functions, symptoms and self-rated characteristics in non-specific chronic neck pain.
Chronic neck pain is a common problem. Since the knowledge on the pathophysiology is scarce, treatment efforts are largely pragmatic, focusing on pain management and restoring functioning and abilities. In order to advance the efficacy of treatment and rehabilitation, new knowledge has to be integrated in clinical practice. One area that has generated much novel results over the last years is the research on sensorimotor functions in chronic neck pain. Thus, a wide range of changes in sensorimotor functions have been identified in these conditions, such as: reduced proprioceptive sensibility of the neck and shoulder; increased jerkiness of cervical rotations; impaired postural control in quiet stance; and altered activation patterns of cervical muscles. Based on such evidence from clinical research, along with data from experimental studies, several models on the pathogenesis of chronic musculoskeletal pain conditions includes mechanisms involving sensorimotor functions.
In line with studies on neck pain patients evaluating the efficacy of exercise regimes targeting cervical sensorimotor functions have shown promising results. Thus, specific exercises for eye-head-neck coordination were shown to reduce pain as well as to improve kinaesthetic sense and cervical range of movement at retests after interventions. To improve the neuromuscular coordination of the deep ventral cervical muscles, a specific cranio-cervical flexion exercise has been developed together with an adherent device. These type of neck exercises are shown to reduce headaches in patients suffering from cervicogenic headache as well as to reduce pain and improve kinaesthetic sense in chronic neck pain patients.
The above mentioned exercises focus on slow movements and closed skills tasks (i.e., the task is highly predictable). Drawing on the literature on motor learning, an opportunity for further development of exercises targeting sensorimotor function of the neck resides in designing an exercise which entails a more open skills task, for example via an unstable dynamic system. Such an exercise is less predictable and demand on-line adjustments of the neuromuscular control system. The exercise should preferably be performed in a functional position and include active problem solving, feedback of results as well as progression of difficulty in order to promote motor learning. To achieve persistence of the exercise effects, as well as transfer to different tasks and task contexts, it is vital to implement components of variation and cognitive effort. These components are partly inherent in open skills tasks.
To be applicable in a clinical setting, the exercise task needs to be easy to understand for the patient, the equipment convenient to use and the level of task difficulty adjustable to suit the individual patient’s skill level. Based on these theoretical and empirical premises we judged that the development of novel methods for neck coordination exercises is important in order to improve the rehabilitation of people suffering from chronic neck pain.
The present paper describes a novel exercise method aiming at improving sensorimotor functioning of the neck, and a pilot study of its clinical applicability and preliminary indications of its efficacy for persons with chronic non-specific neck pain. The specific aims were to study the skill acquisition and to assess the subjects experiences of the exercise. A further aim was to find out preliminary information about changes in sensorimotor functions, pain and self-reported characteristics after a four week exercise period with the novel method.
The results expose positive findings regarding the clinical applicability of the novel neck coordination exercise. Also, indication on possible positive effects were seen in some of the sensorimotor functions and self-rated characteristics.
The exercise regime appeared easy to learn, as all subjects improved their skill to perform the exercise task. This was evident by the progression to the most difficult condition and a successively reduced trial time on each condition during the intervention period. These results confirm that the design of the task and the progression of difficulty were well adapted. Most of the subjects expressed a positive opinion about the exercise, and all subjects reported that the task was easy to understand. The adverse effects due to the exercise that were reported were transient tiredness, discomfort, pain and post-exercise soreness. These side-effects were common and occurred predominantly in the early phase of the intervention period, which can be considered normal reactions due to unaccustomed exercise. Only one person experienced discomfort from wearing the device on the head. Together, these facts support the applicability of the method in a clinical practice, as a conjunction to other interventions, e.g., posture correction, manual therapy, strength and endurance exercises, home exercises etc. Also, a majority of the subjects (8 of 13) mentioned deep concentration on the task when interviewed about exercise strategies. This indicates that the exercise involved substantial cognitive effort, which is argued to be an important factor for retention and transfer of motor skills.
Improvements in sensorimotor functions were indicated by the significant decrease in Tr area (the fast component) of postural sway and jerk index of cervical rotation. This suggests that there may be a transfer effect from the exercise task to other, non-task specific, motor functions, such as increased postural stability and smoothness of cervical movements. Alternatively, these findings may be simple retest effects. However, as presented in the Methods section, former test-retest data on the same variables revealed no retest effects, which speaks against such an interpretation. In accordance with the present finding, improvements in postural sway has been reported in studies on people with neck pain who received physical therapy which included exercises for cervical muscles. A possible explanation to the effects may be improved function of the deep cervical muscles, which are known to contain a high density of muscle spindles, and thereby are important for the postural control. The importance of the proprioceptive input from the neck on the control of posture has been revealed for example in experiments using neck muscle vibration. Moreover, immobilisation of the cervical spine has been associated with unbeneficial effects on sensorimotor functions. Negative effects on eye movements and postural control was reported after a one-week constant use of a cervical collar in a group of healthy people. Since the activity of the deep cervical muscles was not assessed in the present study the possibility of improved proprioceptive input from these muscles remains speculative. The significant repeated measure MANOVA for jerk index, movement time and peak velocity from the cervical rotation test is somewhat ambiguous to interpret since it is the result of three correlated variables. However, the subsequent paired t-tests indicated that jerk index was the main contributor to the effect. Reduced jerkiness after the exercise indicates that the subjects executed the cervical rotation with smoother movements. Less jerkiness is argued to reflect better movement control. The clinical relevance of the effects on postural sway and smoothness of cervical rotations is supported by studies showing increased postural sway during quiet stance in neck pain patients and recent studies showing increased jerk index and irregularities during cervical movements in people with chronic neck pain. In contrast to other studies on proprioceptive and coordination training no effect was seen in cervical repositioning in the present study. The explanation may be that cervical position sense was not influenced by this exercise, while another possible explanation may reside in the difference in methods used for measuring position sense. In the present study position sense was measured with subjects standing, making fast movements as far as possible while in the studies mentioned above the subjects were seated, performing slow movements. Taken together, these results support the use of measurements of postural sway and cervical kinematics as outcome variables in future randomized control trials.
A relevant question is whether the present sample has impaired sensorimotor functions compared to healthy controls. Comparing the present sample with a group of healthy controls (n=21) from an unpublished cross-sectional study did not reveal significant reductions in postural control or cervical movement smoothness. Nevertheless, as mentioned above, disturbances in these sensorimotor functions has been documented in previous studies on people with neck pain. Future studies on this novel neck coordination exercise method should therefore preferably include specifically selected samples of people with postural control and movement smoothness disturbances.
The improvements seen in some of the questionnaire scores at the six-months follow up could be either an effect of the intervention or an effect of natural recovery over time. The improvements of the TSK score may indicate that individually adjusted exercise have positive effect on fear of re-injury due to movement. This reasoning is supported by the results presented by Bunketorp et al., showing that supervised individually adjusted physical exercise improved the TSK score in subjects suffering from whiplash associated disorders.
No significant improvements were found for pain ratings (VAS). The reason may be that this exercise has no effect on pain, or that the dosage of the exercise was too small. Earlier studies which have reported decreased pain ratings after intervention involved more frequent training regimes, suggesting that future studies on this method should involve a more extensive intervention period.
All subjects improved their skill to perform the exercise task. The comprehension of the task was conceived as easy, and a majority expressed a positive opinion about the exercise. Although transient pain and discomfort was common, especially in the early phase of the exercise period, no residual negative side-effects were reported. Taken together, this supports the clinical applicability of the method. The indications on improvements in sensorimotor functions may suggest transfer from the exercise task to other, non-task specific motor functions. The results support a future randomized controlled trial on the exercise effects.
