Performance in the cranio-cervical flexion test is altered in elderly subjects
From: Man Ther. 2009 Jan 24. [Epub ahead of print]
The cranio-cervical flexion test tests the coordination of the deep and superficial cervical flexor muscles during a cranio-cervical flexion task. The test has revealed impairments in muscle function in younger/middle aged patients with various neck pain disorders. Neck pain and headache are common in elders but it is unknown if age alone affects performance in the cranio-cervical flexion test. This study compared performance in the cranio-cervical flexion test between healthy asymptomatic elderly and younger subjects. Electromyographic (EMG) amplitude in the sternocleidomastoid, angle of cranio-cervical flexion and ability to target the pressure levels of each test stage were examined in 44 elderly and 39 young participants.
The results indicated that the elderly group had higher measures of normalized EMG signal amplitude in the sternocleidomastoid during the test, greater shortfalls from the target pressures of all stages of the test, except for the 22mmHg stage, and larger variability of the cranio-cervical flexion range of motion for the five successive stages of the test (particularly at 26, 28 and 30mmHg stages) compared to young subjects. Clinicians must be aware of this occurrence when assessing performance in the cranio-cervical flexion test in elders with neck pain.
The cranio-cervical flexion test assesses the coordination of the deep and superficial cervical flexor muscles during the staged performance of cranio-cervical flexion under low load conditions in a recumbent supine position. Subjects are guided to the five stages of the test with feedback from an air-filled pressure sensor which is positioned behind the neck. Studies which have compared performance between patients with neck pain disorders and asymptomatic subjects have revealed increased EMG amplitude in the superficial flexors, sternocleidomastoid and anterior scalene muscles in neck pain patients. This increased EMG activity is associated with reduced activation of the deep cervical flexors, the longus capitis and its synergist the longus colli. This change in motor strategy is accompanied by a change in the pattern of movement. In asymptomatic subjects, it has been shown that there is a linear relationship between the increasing pressure targets of cranio-cervical flexion test and the range of cranio-cervical flexion used in each test stage. However neck pain patients have been shown to use less range of cranio-cervical flexion motion to perform the task. The recognition of the dysfunction in the cranio-cervical flexors in patients with various neck disorders has assisted in the diagnosis of neck related disorders such as cervicogenic headache. It has also led to the inclusion of specific training for these muscles in therapeutic exercise regimes and the exercise has been shown to be an effective management strategy.
Neck pain and headache are common complaints in elders and the low load nature of the exercise regime would appear to have potential for management for this age group. However baseline performances in the cranio-cervical flexion test on which to judge dysfunction have been derived principally from younger to middle aged asymptomatic populations. It is unknown if such data are applicable to the more elderly population. There is evidence to suggest that there could be differences in performance. For example changes in neuromuscular function in the back muscles have been demonstrated in elders compared to younger subjects and there is evidence of age-related changes in neuromuscular morphology. The performance of the cranio-cervical flexion test which requires precision may also be influenced by cognitive factors, learning and motor skill acquisition in the elderly.
The results of this study demonstrated a linear relationship between the magnitude of the superficial muscle activity and the range of the cranio-cervical flexion ROM used in the five incremental stages of the cranio-cervical flexion test, which is in accordance with the findings of previous studies. Nevertheless, healthy elderly subjects displayed significantly higher EMG RMS activity in the sternocleidomastoid muscles compared to healthy younger subjects and were less able to reach the target pressures of the stages of the cranio-cervical flexion test, indicating that older age does influence performance in the cranio-cervical flexion test. The lesser activity in the sternocleidomastoid, coupled with the pressure shortfall at the 30mmHg stage of the cranio-cervical flexion test, suggests that many elders could not perform this final stage of the test.
The higher levels of EMG RMS activity in the sternocleidomastoid muscles demonstrated by our elders in the cranio-cervical flexion test may reflect the effects of the aging process on the neuromuscular system. Age changes have been observed at the level of the muscle spindle. There is high muscle spindle density in the deep neck muscles which is important for movement detection. Nevertheless, Boyd-Clark et al. observed no change with age in spindle distribution and density in the longus colli and multifidus muscles at C5-7 segments. However differences in the neuromotor control have been shown in other studies of elders. For example, Laursen et al. studied performance and muscle activity during computer mouse tasks and, similar to their observations, found that elderly compared to young adults had higher levels of EMG activity in forearm, shoulder and neck muscles during the task. There is evidence, with increasing age, of a decrease in number and discharge of motor units, less force steadiness and different compositions of muscle fibre types which might be reflected in our findings of elder’s performance in the cranio-cervical flexion test. Additionally, the strength of anti-gravity muscles has been shown to be lower in elderly compared to young persons. The deep cervical flexor muscles have an important anti-gravity role in support of the cervical posture and segments. It is possible that the increased activity in the sternocleidomastoid muscles in the cranio-cervical flexion test in their elders reflected declining function of the deep cervical flexors in this age group, akin to the changed pattern of muscle activity between the deep and superficial flexors measured in younger populations with neck pain.
Even though a linear relationship was evident between the progressive stages of the cranio-cervical flexion test and the range of cranio-cervical flexion used for each test stage, there was a large variability in the range used by the elderly group (as evident in the larger SE at the 26, 28 and 30mmHg test stages for this group). Often they could not reach the target pressures (pressure shortfalls). The variability in elders may reflect changes in the biomechanical response of the cervical segments associated with cervical degeneration and the loss of segmental mobility with age. The variability may also have reflected age-related changes in central processing. Motor planning and learning are less efficient in elderly subjects with a decline in coarse and fine motor performance with increasing age. The cranio-cervical flexion test requires both fine motor and cognitive skills which might be challenging for an elderly population. This could have encouraged some elders to use more gross motor strategies during the test, for example head retraction, which might account for the variability in range and pressure targeting measured as well as the increased EMG activity found in this study.
Anxiety is another factor to consider in relation to the differences in the cranio-cervical flexion test results between the younger and older groups. Relationships have been found between higher levels of anxiety, poorer motor performance and increased EMG activity as well as a greater decline in performance in the elderly compared to young adults when anxiety levels are higher. The cranio-cervical flexion test was designed to place a high demand on motor control but not on mental stress. Hence, a measure of an association between anxiety and the cranio-cervical flexion test was not considered in this study. However, it was noted that performance of the cranio-cervical flexion test was challenging in the elderly subjects and they often provided feedback on the difficulty of the cranio-cervical flexion test task. Thus some level of anxiety may have contributed to the increased sternocleidomastoid muscle activity observed in their elderly subjects.
