Validity and between-day reliability of the cervical range of motion (CROM) device.

STUDY DESIGN: Clinical measurement, validity and intrarater reliability study. OBJECTIVES: (1) To confirm the validity and assess between-day test-retest reliability of cervical spine motion measurements made with the cervical range of motion (CROM) device in flexion, extension, bilateral rotation, and bilateral side flexion; (2) to provide meaningful information to clinicians about the standard error of measurement and the minimal detectable change for the CROM device. BACKGROUND: Range of motion is a common outcome measure used in the assessment of the cervical spine. The CROM device is one of the tools used to measure cervical range of motion in the clinical setting. However, its psychometric properties are not well established, especially for measurements taken on separate days. METHODS: Quasi-experimental design with 1 group comparison. Twenty healthy adults (9 men and 11 women) participated in this study. Cervical range of motion was simultaneously recorded with the CROM device and the Fastrak motion analysis system for all 6 cervical movements mentioned above. The CROM device was placed on the participant's head consistent with standard clinical procedures. Two Fastrak sensors were positioned with 1 on the forehead and 1 over the spinous process of the T6 vertebra. Test-retest reliability of measurements made with the CROM device was assessed, as well as its standard error of measurement and minimal detectable change, with measures taken on 2 separate days spaced 48 hours apart. RESULTS: Values obtained by the 2 measuring devices yielded Pearson correlation coefficients ranging between 0.93 and 0.98. Test-retest reliability of measurements of cervical range of motion using the CROM was found to be good, with ICCs ranging between 0.89 and 0.98. The standard errors of measurement across the 6 movements ranged from 1.6 degrees to 2.8 degrees and the minimal detectable changes across the 6 movements ranged from 3.6 degrees to 6.5 degrees . CONCLUSIONS: The measurements made with the CROM were shown to be reliable in all movement directions. J Orthop Sports Phys Ther 2010;40(5):318-323, Epub 12 March 2010. doi:10.2519/jospt.2010.3180.

The coordination of upper and lower limb movements during gait in healthy and stroke individuals.

Human walking involves coordinated movements of all four limbs. The benefits of incorporating arm movements in gait rehabilitation are not known and difficult to investigate in patient populations with poor balance and reduced walking capacity. This study assessed the effect of supported (SUP) versus unsupported (UNSUP) arm movements on the coordination patterns present during walking in individuals with and without a stroke. Ten high functioning stroke subjects and 10 healthy subjects walked on a treadmill while swinging their arms naturally, and while holding onto handles that were either fixed in place or allowed to slide along horizontal handrails. Full-body kinematics were recorded, and arm-leg coordination was quantified using relative phase index, mean relative phase, and cross-correlation of hip and shoulder angle time series. No differences were observed in any measures of coordination between healthy and stroke subjects, indicating that the ability to coordinate arm and leg movements during walking remains preserved in high functioning stroke individuals. Coordination patterns were also unaffected by the use of sliding handrails, suggesting that this paradigm may be a suitable surrogate for natural arm movements if individuals are unable to walk without an external support. Stroke subjects were able to perform arm movements at a faster walking speed when using the handles than they were able to achieve without the handles, indicating that this paradigm may be useful in encouraging arm movements during gait rehabilitation.

Maximal voluntary isometric neck strength deficits in adults with whiplash-associated disorders and association with pain and fear of movement.

STUDY DESIGN: Controlled laboratory study using a cross-sectional, repeated-measures design. OBJECTIVES: To quantify maximal voluntary isometric neck forces in healthy subjects and individuals with whiplash-associated disorder (WAD), using an objective measurement system to evaluate the test-retest properties of these strength measurements and to assess the links between neck strength, pain, kinesiophobia, and catastrophizing in patients with WAD. BACKGROUND: The prognosis of WAD is difficult to predict due to a lack of objective measurement methods and to our limited understanding of the role of psychological factors in the development of chronic WAD symptoms. METHODS AND MEASURES: Fourteen subjects with chronic WAD grade I or II and an age-matched, healthy group (n = 28) participated in this study. Cervical strength was measured with the Multi-Cervical Unit (MCU) in 6 directions, and pain was measured with a visual analog scale. Individuals in the WAD group completed the Neck Disability Index (NDI), the Tampa Scale for Kinesiophobia (TSK), and the Pain Catastrophizing Scale (PCS). RESULTS: Significant deficits in strength were observed for the individuals in the WAD group compared to the healthy group, particularly in extension, retraction, and left lateral flexion (P<.05). The MCU demonstrated good intratester reliability for the healthy group (ICC = 0.80-0.92) and the WAD group (ICC = 0.85-0.98), and small standard errors of measurement for both groups. No significant association was found between neck strength and NDI, TSK, and PCS. CONCLUSION: The MCU demonstrated good test-retest properties for healthy subjects and individuals with WAD. Cervical strength was lower in individuals with WAD; however, the strength deficits were not clearly linked with psychological factors.

Threshold position control of arm movement with anticipatory increase in grip force.

The grip force holding an object between fingers usually increases before or simultaneously with arm movement thus preventing the object from sliding. We experimentally analyzed and simulated this anticipatory behavior based on the following notions. (1) To move the arm to a new position, the nervous system shifts the threshold position at which arm muscles begin to be recruited. Deviated from their activation thresholds, arm muscles generate activity and forces that tend to minimize this deviation by bringing the arm to a new position. (2) To produce a grip force, with or without arm motion, the nervous system changes the threshold configuration of the hand. This process defines a threshold (referent) aperture (R(a)) of appropriate fingers. The actual aperture (Q(a)) is constrained by the size of the object held between the fingers whereas, in referent position R(a), the fingers virtually penetrate the object. Deviated by the object from their thresholds of activation, hand muscles generate activity and grip forces in proportion to the gap between the Q(a) and R(a). Thus, grip force emerges since the object prevents the fingers from reaching the referent position. (3) From previous experiences, the system knows that objects tend to slide off the fingers when arm movements are made and, to prevent sliding, it starts narrowing the referent aperture simultaneously with or somewhat before the onset of changes in the referent arm position. (4) The interaction between the fingers and the object is accomplished via the elastic pads on the tips of fingers. The pads are compressed not only due to the grip force but also due to the tangential inertial force ("load") acting from the object on the pads along the arm trajectory. Compressed by the load force, the pads move back and forth in the gap between the finger bones and object, thus inevitably changing the normal component of the grip force, in synchrony with and in proportion to the load force. Based on these notions, we simulated experimental elbow movements and grip forces when subjects rapidly changed the elbow angle while holding an object between the index finger and the thumb. It is concluded that the anticipatory increase in the grip force with or without correlation with the tangential load during arm motion can be explained in neurophysiological and biomechanical terms without relying on programming of grip force based on an internal model.

Stroke affects the coordination and stabilization of head, thorax and pelvis during voluntary horizontal head motions performed in walking.

OBJECTIVE: This study was conducted to investigate and compare the coordination and stabilization of axial segments during walking with and without horizontal voluntary head turns, in healthy (n=5) and hemiparetic (n=10) subjects. METHODS: Subjects were instructed to turn the head as fast and as soon as possible in the direction indicated by an illuminated arrow signal (right, left or none) that was triggered at initial contact of the right (healthy) or paretic (hemiparetic) foot. Head, thorax, and pelvis motions were obtained from a 9-segment model using retro-reflective markers and a Vicon-512 system with 6 high-resolution cameras. Coordination of axial segments in the horizontal plane was characterized using cyclographs and cross-correlation analyses. Stabilization of the segments was quantified using root mean square (RMS) values of the segment's normalized acceleration profile. RESULTS: The healthy subjects showed a direction-dependent modulation of axial segment coordination, with head turns toward and away from the stance limb favoring and hindering, respectively, the contra-rotational pattern of the thorax with respect to the pelvis during locomotion. Meanwhile, pelvis motions remained unaltered. This direction-specific modulation pattern was disrupted in the hemiparetic subjects, both in the spatial and temporal domains. Moreover, larger RMS values for head and thorax segments were observed in the hemiparetic groups, both with and without the superimposition of voluntary head motions. CONCLUSIONS: The findings suggest that: (1) head rotations during walking modify axial segment coordination in a direction-specific manner, (2) the pelvic rotations associated with locomotion remained unaffected by head rotations and (3) stroke alters this coordination behavior, which may contribute to balance dysfunctions during locomotion.

The effect of arm movements on the lower limb during gait after a stroke.

The purpose of this study was to examine the influence of arm movements on lower limb movement and muscle activation during treadmill walking after a stroke. Ten high functioning stroke and 10 healthy subjects walked on a treadmill while swinging their arms naturally, and while holding onto handles that were either fixed in place or allowed to slide along horizontal handrails. Full-body kinematics were recorded, along with bilateral surface electromyography from lower limb muscles. Arm movements influenced lower limb muscle activity but had little effect on movement patterns at the joints. When handrails were present a small amount of weight was borne through the upper limbs, and for stroke subjects this was reduced when the handles were free to slide. Activity of proximal leg muscles during stance was affected by the weight borne through the upper limbs, increasing when arm movements were performed. Soleus activity during stance was greatest with unsupported arm movements. In stroke subjects, early stance tibialis anterior activity in the paretic leg was greatest with no arm movements, and early swing tibialis anterior activity in both legs was greatest with unsupported arm movements. Many of the changes in muscle activation appeared to be due to changes in postural stability that occurred when performing arm movements. Overall, results support further study of the long-term changes associated with the inclusion of arm movements in gait rehabilitation protocols.

The effects of a Pilates training program on arm-trunk posture and movement.

BACKGROUND: Shoulder biomechanics and spine alignment have been found to be related to occasional and/or chronic neck-shoulder pain. Pilates is a physical training approach that focuses on posture, flexibility, segmental alignment and core control, through posture and movement exercises. The objectives of this study were to determine the effect of a Pilates training program on arm-trunk posture, strength, flexibility and biomechanical patterns during a functional shoulder flexion task. METHODS: Nineteen subjects (9 controls, 10 experimental) were assessed twice, 12 weeks apart, during which the experimental group was submitted to a Pilates training program (two 1-h sessions per week). The assessment consisted of trials of seated posture, abdominal strength, shoulder range of motion, and maximal shoulder flexion, during which neck, shoulder and trunk kinematics and the activity of 16 muscles were recorded. FINDINGS: After training, subjects showed smaller static thoracic kyphosis during quiet sitting and greater abdominal strength. The experimental group also showed reduced posterior and mediolateral scapular displacements, upper thoracic extension and lumbar lateral flexion, as well as higher activity of the ipsilateral cervical erector spinae, contralateral rhomboid muscles and lower activity of the ipsilateral lumbar erector spinae during the shoulder flexion task. INTERPRETATION: The Pilates training program was effective in improving abdominal strength and upper spine posture as well as in stabilizing core posture as shoulder flexion movements were performed. Since deficits in these functional aspects have previously been associated with symptoms in the neck-shoulder region, our results support the use of Pilates in the prevention of neck-shoulder disorders.

Relationships between pain thresholds, catastrophizing and gender in acute whiplash injury.

The mechanisms underlying sensory hypersensitivity (SH) in acute whiplash associated disorders (WAD) are not well understood. We examined the extent of the relationships between the sensory measures of pressure pain threshold (PPT) and cold pain threshold (CPT), catastrophizing, pain and disability levels and gender in acute WAD. Thirty-seven subjects reporting neck pain following a motor vehicle accident were examined within five weeks post-injury. Measures of neck pain and disability (Neck Disability Index, NDI) and catastrophizing (Pain Catastrophizing Scale, PCS) were taken. CPT was assessed in the cervical spine and PPTs were assessed in the cervical spine (PPTcx) and at a remote site (PPTdistal). CPT and PCS were moderately correlated (r=0.46; p < 0.01); however there were no significant relationships between PPT (cervical and distal) and PCS. Both CPT (r=0.55, p < 0.01) and PPTcx (r=-0.42, p < 0.01) were significantly correlated with NDI but PPTdistal was not (r=-0.08, p=0.65). Finally, gender modulated the relationships between sensory measures, catastrophizing, and pain and disability levels. In conclusion, subjects with higher levels of catastrophizing presented with sensory hypersensitivity to cold stimuli in the acute phase of whiplash. Differences between genders are in accordance with the growing body of evidence suggesting that the relationships between some psychological factors and injury-related symptoms are modulated by gender.

Exploring the human grip force system: a preliminary study.

It has been postulated that cutaneo-receptors from the digits contribute to the control of manipulatory functions of the hand. However, few studies have examined the dynamics of the human grip force system (HGFS) in terms of the dynamic relationship between the vertical loads, taken as an input and the resulting grip force, taken as the output. This paper describes the experimental procedures we have developed to explore the HGFS and presents some initial experimental results. These demonstrate that the step response of the HGFS is biphasic. The first, short latency phase, likely involves only passive and intrinsic components. The second, longer latency phase is likely related to reflex mechanisms since it is preceded by a strong burst of EMG. Moreover, the HGFS response depended nonlinearly on the amplitude and direction of the load applied. These results indicate that further investigation of HGFS dynamics will require the use of nonlinear identification methods.

The accuracy of perception of a pinch grip force in older adults.

The fact that humans can execute accurate movements and generate precise muscle forces is very important for hand function. Target-tracking tasks or target-matching tasks are often executed under combined visual and somatosensory feedback. When visual feedback is removed, subjects have to depend on their perception of force. The objective of the present study was to estimate the effects of aging on the perception of a pinch force produced by the thumb and index finger. In a first set of trials, young (n = 12, age = 25.3 +/- 2.4 years) and elderly (n = 12, age = 71.5 +/- 3.3 years) healthy individuals were asked to reproduce pinch forces which were equivalent to 5%, 20%, and 40% of their maximal pinch force (MPF). Prior to the execution of these trials, the subjects were familiarized with the force levels by matching targets displayed on a screen. They were then asked to reproduce each of these forces without any visual or verbal feedback. The results showed a larger error in the reproduced force for the elderly subjects when compared with the young adults. However, this larger error was mainly due to an initial overshoot in the force to be reproduced, followed by a gradual decrease towards the appropriate force. This transient overshoot was rarely seen in the performance of the younger subjects. In a second set of trials, the same subjects were asked to produce a pinch force of 5%, 20%, and 40% of MPF with 1 hand using visual feedback. They were also instructed to simultaneously apply a comparable pinch force with the other hand (without any feedback). For both young and older adults, the pinch forces produced by the 2 hands were the same. In addition, in both blocks of trials, hand dominance had no effects on the performance for all subjects. These results suggest that normal aging affects the production of force based on sensorimotor memory rather more than it affects comparative outputs from central descending commands.

Stretch reflex gain in cat triceps surae muscles with compliant loads.

The triceps surae (TS) stretch reflex was measured in decerebrate cats during crossed extensor stimulation (tonic contractions) and after spinalization during rhythmic locomotor activity. The TS reflex force in response to a short pulse stretch measured during tonic contractions at low level of background activity was greater than when more background activity was present at the time of application of stretch. In contrast, the reflex force measured during rhythmic contractions was very small at low level of background force (flexion phase) and increased at moderate and high levels of background activity (extension phase). Thus, even in reduced preparations, a task modulation of the stretch reflex occurs. Throughout the experimental procedure, the torque motor used to stretch the muscles behaved like a spring of a preset compliance (from isometric to very compliant). A reflex model was used to simulate the responses obtained experimentally. The gain of the stretch reflex loop was estimated for each load condition and both behavioural tasks. The reflex loop gain was significantly larger as the compliance of the external load increased for both tonic and rhythmic contractions, although to a lesser extent in the phasically activated muscles. During rhythmic locomotor contractions the gain was less than 1, assuring stability of the system. In contrast, during tonic contractions against a compliant load the gain exceeded 1, consistent with the instability (oscillations, clonus) seen at times under these load conditions. However, the high gain and instability was only transient, since repeated stretch reduced the gain. Thus, non-linearities in the system assured vigorous responses at the onset of perturbations, but then weaker responses to ongoing perturbations to reduce the chance of feedback instability (clonus).