Sensory – Motor control of ligaments and associated neuromuscular disorders

The effect of spinal curvature on the photogrammetric assessment on static balance in elderly women

BACKGROUND

Involutional changes to the body in elderly patients affect the shape of the spine and the activity of postural muscles. The purpose of this study was to assess the influence of age-related changes in spinal curvature on postural balance in elderly women.

METHODS

The study population consisted of 90 women, with a mean age of 70 ± 8.01 years. Static balance assessments were conducted on a tensometric platform, and posturographic assessments of body posture were performed using a photogrammetric method based on the Projection Moiré method.

RESULTS

The results obtained were analysed using the Spearman's rank correlation coefficient test. We found a statistically significant correlation between body posture and the quality of the balance system response based on the corrective function of the visual system. The shape of the spinal curvature influenced postural stability, as measured by static posturography. Improvement in the quality of the balance system response depended on corrective information from the visual system and proprioceptive information from the paraspinal muscles.

CONCLUSIONS

The sensitivity of the balance system to the change of centre of pressure location was influenced by the direction of the change in rotation of the shoulder girdle and spine. Development of spinal curvature in the sagittal plane and maintenance of symmetry in the coronal and transverse planes are essential for correct balance control, which in turn is essential for the development of a properly proportioned locomotor system.

Motor coordination during gait after anterior cruciate ligament injury: a systematic review of the literature

To investigate the state of art about motor coordination during gait in patients with anterior cruciate ligament (ACL) injury. Searches were carried out, limited from 1980 to 2010, in various databases with keywords related to motor coordination, gait and ACL injury. From the analysis of titles and applying the inclusion/exclusion criteria 24 studies were initially selected and, after reading the abstract, eight studies remained in the final analysis. ACL deficient patients tend to have a more rigid and less variable gait, while injured patients with ACL reconstruction have less rigid and more variable gait with respect to healthy individuals. The overall results suggest the existence of differences in motor coordination between the segments with intact and those with injured knee, regardless of ligament reconstruction. ACL injured patients present aspects related to the impairment of the capability to adapt the gait pattern to different environmental conditions, possibly leading to premature knee degeneration. However, the techniques used for biomechanical gait data processing are limited with respect to obtaining information that leads to the development of intervention strategies aimed at the rehabilitation of that injury, since it is not possible to identify the location within the gait cycle where the differences could be explained.

Evaluation of the mechanical efficiency of knee braces based on computational modeling

Knee orthotic devices are commonly prescribed by physicians and medical practitioners for preventive or therapeutic purposes on account of their claimed effect: joint stabilisation and proprioceptive input. However, the force transfer mechanisms of these devices and their level of action remain controversial. The objectives of this work are to characterise the mechanical performance of conventional knee braces regarding their anti-drawer effect using a finite element model of a braced lower limb. A design of experiment approach was used to quantify meaningful mechanical parameters related to the efficiency and discomfort tolerance of braces. Results show that the best tradeoff between efficiency and discomfort tolerance is obtained by adjusting the brace length or the strap tightening. Thanks to this computational analysis, novel brace designs can be evaluated for an optimal mechanical efficiency and a better compliance of the patient with the treatment.

Classification-guided versus generalized postural intervention in subgroups of nonspecific chronic low back pain: a pragmatic randomized controlled study

STUDY DESIGN

Pragmatic randomized controlled single-blinded study.

OBJECTIVE

To compare the effects of the classification system guided postural intervention (CSPI) with generalized postural intervention (GPI) in subgroups of nonspecific chronic low back pain (NSCLBP).

SUMMARY OF BACKGROUND DATA

Spinal motor control impairments and the associated alterations in spinal postures adopted by patients with NSCLBP are highly variable. Research evaluating the effect of interventions that target the specific movement/posture impairments in NSCLBP subgroups is therefore warranted.

METHODS

A total of 49 patients with NSCLBP with a classification of flexion pattern (n = 29) and active extension pattern (n = 20) control impairment were recruited from a large cohort study and randomly assigned into CSPI and GPI. The primary outcome was change in Roland-Morris Disability Questionnaire, secondary outcomes were change in pain visual analogue scale, spinal repositioning sense including thoracic and lumbar absolute error, variable error, constant error, and trunk muscle activity during sitting and standing. The intervention was evaluated at baseline, immediately post one-to-one intervention and post 4-week home-based training.

RESULTS

The CSPI produced statistically and clinically significant reduction in disability (4.2 [95% CI, 2.9-5.3]) and pain (2, [95% CI, 1.3-2.6]) compared with minimal change in the GPI disability (0.4, [95% CI, -0.8 to 1.6]) and pain (-0.2, [95% CI, -0.5 to 0.9]). Repeated measures analysis of variance revealed that CSPI significantly reduced absolute error in thoracic (sitting) and lumbar spine (standing) and constant error in lumbar spine (standing) post one-to-one phase, although this was no longer significant at 4 weeks. Neither intervention had an effect on trunk muscle activity.

CONCLUSION

Compared with minimal change in the GPI group, the CSPI produced statistically and clinically significant improvements in disability and pain outcomes and short-term improvements in some parameters of spinal repositioning sense in NSCLBP subgroups.

Reducing anterior tibial translation by applying functional electrical stimulation in dynamic knee extension exercises: quantitative results acquired via marker tracking

BACKGROUND

Pain that accompanies anterior cruciate ligament deficiency during dynamic knee extension exercises is usually caused by excessive anterior tibial translation, which can be restricted if the anterior cruciate ligament was intact.

METHODS

A functional electrical stimulator is incorporated with a training device to induce hamstring contractions during certain degrees of knee extension to replicate effects similar to those generated by an intact anterior cruciate ligament and to reduce anterior tibial translation. By using a camera that tracks markers placed on bony prominences of the femur and tibia, the anterior tibial translations corresponding to various settings were determined by customized image processing procedures.

FINDINGS

In the electrical stimulation sessions, the knee extensions with electrical stimulation feedback induced significantly (n=6, P<.05) less anterior tibial translation over the range of 20 to 50° when compared to those using the standard isokinetic shank restraint. Likewise, the knee extensions with an anti-shear device that blocks tibia displacement mechanically also induced significantly (n=6, P<.05) less anterior tibial translation, but over a different range of knee extension (30 to 70°).

INTERPRETATION

Despite the fact that both the electrical stimulator and the anti-shear device assisted in reducing anterior tibial translation, the tendency of the curves generated with the functional electrical stimulation was generally more similar to those generated when using the standard isokinetic shank restraint.

Macroscopic and microscopic analysis of the thumb carpometacarpal ligaments: a cadaveric study of ligament anatomy and histology

BACKGROUND

Stability and mobility represent the paradoxical demands of the human thumb carpometacarpal joint, yet the structural origin of each functional demand is poorly defined. As many as sixteen and as few as four ligaments have been described as primary stabilizers, but controversy exists as to which ligaments are most important. We hypothesized that a comparative macroscopic and microscopic analysis of the ligaments of the thumb carpometacarpal joint would further define their role in joint stability.

METHODS

Thirty cadaveric hands (ten fresh-frozen and twenty embalmed) from nineteen cadavers (eight female and eleven male; average age at the time of death, seventy-six years) were dissected, and the supporting ligaments of the thumb carpometacarpal joint were identified. Ligament width, length, and thickness were recorded for morphometric analysis and were compared with use of the Student t test. The dorsal and volar ligaments were excised from the fresh-frozen specimens and were stained with use of a triple-staining immunofluorescent technique and underwent semiquantitative analysis of sensory innervation; half of these specimens were additionally analyzed for histomorphometric data. Mixed-effects linear regression was used to estimate differences between ligaments.

RESULTS

Seven principal ligaments of the thumb carpometacarpal joint were identified: three dorsal deltoid-shaped ligaments (dorsal radial, dorsal central, posterior oblique), two volar ligaments (anterior oblique and ulnar collateral), and two ulnar ligaments (dorsal trapeziometacarpal and intermetacarpal). The dorsal ligaments were significantly thicker (p < 0.001) than the volar ligaments, with a significantly greater cellularity and greater sensory innervation compared with the anterior oblique ligament (p < 0.001). The anterior oblique ligament was consistently a thin structure with a histologic appearance of capsular tissue with low cellularity.

CONCLUSIONS

The dorsal deltoid ligament complex is uniformly stout and robust; this ligament complex is the thickest morphometrically, has the highest cellularity histologically, and shows the greatest degree of sensory nerve endings. The hypocellular anterior oblique ligament is thin, is variable in its location, and is more structurally consistent with a capsular structure than a proper ligament.

The lumbar supraspinous ligament demonstrates increased material stiffness and strength on its ventral aspect

The present work represents the first reported quantified anisotropic, inhomogeneous material constitutive data for the human supraspinous ligament (SSL). Multi-axial material data from 30 human cadaveric SSL samples was collected from distinct locations (dorsal, midsection, and ventral). A structurally motivated strain-energy based continuum model was employed to characterize anisotropic constitutive parameters for each sample. The anisotropic constitutive response correlated well with the reported experimental data (R2>0.97). Results show that in the lumbar spine both the material stiffness and stress at failure were significantly higher in the ventral region of the SSL as compared with the dorsal region (p<0.05). In the along fiber direction a higher stiffness and stress at failure were observed when compared to the transverse direction. These results indicate that modeling spinal ligaments using the hyperelastic line elements that have typically been used may be insufficient to capture their complex material response.

Mechanisms of chronic pain from whiplash injury

This article is to provide insights into the mechanisms underlying chronic pain from whiplash injury. Studies show that injury produces plasticity changes of different neuronal structures that are responsible for amplification of nociception and exaggerated pain responses. There is consistent evidence for hypersensitivity of the central nervous system to sensory stimulation in chronic pain after whiplash injury. Tissue damage, detected or not by the available diagnostic methods, is probably the main determinant of central hypersensitivity. Different mechanisms underlie and co-exist in the chronic whiplash condition. Spinal cord hyperexcitability in patients with chronic pain after whiplash injury can cause exaggerated pain following low intensity nociceptive or innocuous peripheral stimulation. Spinal hypersensitivity may explain pain in the absence of detectable tissue damage. Whiplash is a heterogeneous condition with some individuals showing features suggestive of neuropathic pain. A predominantly neuropathic pain component is related to a higher pain/disability level.

Spinal position sense and trunk muscle activity during sitting and standing in nonspecific chronic low back pain: classification analysis

STUDY DESIGN

A cross-sectional study between subgroups of nonspecific chronic low back pain (NSCLBP) and asymptomatic controls.

OBJECTIVE

To investigate NSCLBP subgroup differences in spinal position sense and trunk muscle activity when repositioning thoracic and lumbar spine into neutral (midrange) spinal position during sitting and standing.

SUMMARY OF BACKGROUND DATA

Patients with NSCLBP report aggravation of symptoms during sitting and standing. Impaired motor control in NSCLBP, associated with sitting and standing postures nearer the end range of spinal motion, may be a contributing factor. Rehabilitation improving neutral (midrange) spinal position control is advocated. Postural and motor control alterations vary in different NSCLBP subgroups, potentially requiring specific postural interventions. There is limited evidence on whether subgroup differences exist when performing neutral spine position tasks.

METHODS

Ninety patients with NSCLBP and 35 asymptomatic controls were recruited. Two blinded practitioners classified NSCLBP into subgroups of active extension pattern and flexion pattern. Participants were assisted into neutral spine position and asked to reproduce this position 4 times. Absolute, variable, and constant errors were calculated. Three-dimensional thoracic and lumbar kinematics quantified the repositioning accuracy and surface electromyography assessed back and abdominal muscles activity bilaterally.

RESULTS

Irrespective of subclassification, patients with NSCLBP produced significantly greater error magnitude and variability than the asymptomatic controls, but subgroup differences were detected in the error direction. Subgroup differences in the trunk muscle activity were not consistently identified. Although both subgroups produced significantly higher abdominal activity, subclassification revealed difference in superficial multifidus activity during standing, with flexion pattern producing significantly greater activity than the asymptomatic controls.

CONCLUSION

Subgroups of NSCLBP had similar neutral spinal position deficits regarding error magnitude and variability, but subclassification revealed clear subgroup differences in the direction of the deficit. The trunk muscle activation was shown to be largely nondiscriminatory between subgroups, with the exception of superficial lumbar multifidus.

Relative importance of expertise, lifting height and weight lifted on posture and lumbar external loading during a transfer task in manual material handling

The objective of this study was to measure the effect size of three important factors in manual material handling, namely expertise, lifting height and weight lifted. The effect of expertise was evaluated by contrasting 15 expert and 15 novice handlers, the effect of the weight lifted with a 15-kg box and a 23-kg box and the effect of lifting height with two different box heights: ground level and a 32 cm height. The task consisted of transferring a series of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables (moments) while expertise had low impact. On the other hand, expertise showed a significant effect of posture variables on the lumbar spine and knees. All three factors are important, but for a reduction of external back loading, the focus should be on the lifting height and weight lifted.

PRACTITIONER SUMMARY

The objective was to measure the effect size of three important factors in a transfer of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables but expertise was a major determinant in back posture.

Effect of partial wrist denervation on wrist kinesthesia: wrist denervation does not impair proprioception

PURPOSE

To evaluate the potential effect of partial wrist denervation on wrist kinesthesia, we hypothesized that anesthetizing the anterior interosseous nerve and the posterior interosseous nerve does not impair the kinesthesia.

METHODS

We performed a double-blinded, prospective, randomized study on 80 healthy volunteers (20-54 y old) to compare the ability to detect active and passive wrist movement in 2 conditions. The test group received an anesthetic block of the anterior and posterior interosseous nerves, and the control group subjects received an injection of saline. The kinesthesia of the 2 groups was then tested in 2 conditions by measuring the error in an active and passive wrist repositioning task. Results were analyzed using a repeated measures analysis of variance.

RESULTS

In both active and passive conditions, there was no difference in the repositioning errors between the test group and the control group.

CONCLUSIONS

Our results show that kinesthesia is not impaired by blocking the anterior and posterior interosseous nerves. These findings are consistent for both active and passive motion. The study gives strong evidence that partial denervation does not impair wrist kinesthesia. However, because only kinesthesia was studied, we cannot conclude that partial denervation is a totally safe procedure for all aspects of proprioception.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic I.

Extension and flexion torque variability in ACL deficiency

PURPOSE

To evaluate possible differences in knee extension and flexion torque variability in the anterior cruciate ligament-deficient (ACLD) leg and their dependence on muscle length and visual feedback (VF). Although a knee extension torque deficit is found in the ACLD leg, there is no evidence that variability in submaximal isometric knee extension and flexion torque is affected in the ACLD leg or that it depends on VF.

METHODS

All tests were performed using 13 untrained men with unilateral ACL rupture. Isometric knee extension torques at 90(o) and 120(o) and knee flexion torques at 90(o), 120(o) and 140(o) were evaluated in healthy and ACLD legs. Isometric torque variability at 20% of maximal force was evaluated with or without VF. The coefficients of variation (CV) and permutation entropies (PE) were used to calculate submaximal isometric torque variability.

RESULTS

Healthy legs had significantly greater isometric torques at 90(o) and 120(o) knee angles during knee extension compared with ACLD legs. There were no differences between healthy and ACLD legs in torque variability in knee extension and flexion with or without VF. The PE of knee extension torque at knee angles of 90(o) and 120(o) was significantly (P < 0.05) greater in healthy legs.

CONCLUSIONS

The effect of ACL deficiency on variability (CV) in submaximal isometric knee extension and flexion torque was not significant. However, PE of knee extension submaximal torque was significantly greater in the healthy leg than in the ACLD leg. When estimating ACL deficit, it is important to measure not only isometric maximal torque but also torque variability and complexity using nonlinear tool during submaximal isometric tasks.

LEVEL OF EVIDENCE

III.

Impaired performance on the angle board test is induced in a model of painful whiplash injury but is only transient in a model of cervical radiculopathy

Although clinical studies report motor impairment associated with some painful injuries of the neck, assessment of motor function in animal models has been largely limited only to studies of direct trauma to the nervous system. The incline plane test was modified to evaluate motor function in two rodent pain models of facet joint distraction (FJD) and nerve root compression (NRC) injury (n = 5/group). Sham groups were also included as controls. Motor function was measured using the modified inclined plane test with rats facing downward before surgery (baseline) and following surgery on days corresponding to when mechanical sensitivity is established and remains elevated. Mean baseline values of the board angle inducing slip for FJD (45.8 ± 3.1°) was significantly greater (p = 0.014) than that for NRC (43.5 ± 2.5°), but baseline measurements did not vary for either group over time. No changes in motor function were found for shams. Motor function after FJD significantly decreased (p < 0.001) at days 1 and 7 after injury. In contrast, at day 1 after NRC injury, slip occurred at significantly lower (p = 0.0016) incline angles, but returned to baseline levels by day 7. These results show motor function impairment is induced following painful FJD and suggest the incline plane test offers utility to evaluate functional deficits in painful injuries.

Time dependent spine stability: the wise old man and the six blind elephants

Spine stability of the behaving human in health or disorder is a complex, multi-factorial and time variable index. The major components of stability are the properties of the external load, passive viscoelastic tissues (ligaments, discs, facet capsules and dorso-lumbar fascia) combined with the properties of the active tissues (muscles and their sensory-motor control, co-activation and associated intra-abdominal pressure) as well as the pro-inflammatory status of the tissues. Each of the many components' contribution is time variable with dependence on the dose-duration of the work stimulus and the associated rest. Interaction of many variables is also dominant. A call is issued to focus research efforts on the development of a multi-factorial description of spine stability while representing the contribution of all relevant components as time variable functions. An example is provided, using models of four components described as functions of time derived from real data obtained simultaneously from the in-vivo feline. The example elucidates the potential errors made when using single components to assess stability and the insight gained when stability is introduced as a time dependent index. It is expected that such time variable stability assessment will provide uniform and insightful estimation that will have valuable applications in occupational, sports and rehabilitation fields as well as the leisure lifestyles required for maintaining a healthy spine.

Kinaesthesia and Methods for its Assessment: Literature Review

In this review measurement techniques used for kinaesthetic sense assessment are presented. Kinaesthesia is an important part of human movement control and provides us with better understanding of specific movement system adaptations to fatigue, training and injury. Additionally, decreased kinaesthesia can be an injury predisposing factor, which stresses the necessity for its assessment in sports injury prevention programs. First, terminology and functional concept of kinaesthesia is presented in relation to other related concepts like proprioception and sensory-motor function. For better understanding, basic underlying neurological backgrounds are discussed in chapter two, encompassing peripheral sensory fields as well as the basics of the central processing. Additionally, factors affecting kinaesthesia and its adaptations to training are presented. Functional aspects are discussed, supporting the role of assessment of kinaesthesia in sports and rehabilitation. In the third chapter, a proposal for measuring methods classification is given. In the final chapter, different measuring protocols and their modifications are presented. Due to their usefulness in sports and injury prevention, methods for measuring sense of joint position, movement onset and active tracking are discussed in more detail. Possibilities and examples of their application to sports and sports injury rehabilitation settings are presented. Some basic guidelines are given of how to use these methods in training or for screening kinaesthesia.

Understanding stability of the distal radioulnar joint through an understanding of its anatomy

The authors describe the anatomy of the distal radioulnar joint (DRUJ) and delineate the importance of viewing this joint as part of the whole forearm. The osseous congruity and ligamentous integrity is of essence for the stability of the DRUJ, according to the principles of tensegrity. The neuromuscular control and possible proprioceptive function of the DRUJ are also outlined.

Comparison of trunk proprioception between patients with low back pain and healthy controls

OBJECTIVE

To determine whether proprioceptive impairments exist in patients with low back pain (LBP). We hypothesized that patients with LBP would exhibit larger trunk proprioception errors than healthy controls.

DESIGN

Case-control study.

SETTING

University laboratory.

PARTICIPANTS

24 patients with nonspecific LBP and 24 age-matched healthy controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We measured trunk proprioception in all 3 anatomical planes using motion perception threshold, active repositioning, and passive repositioning tests.

RESULTS

LBP patients had significantly greater motion perception threshold than controls (P<.001) (1.3+/-0.9 degrees vs 0.8+/-0.6 degrees ). Furthermore, all subjects had the largest motion perception threshold in the transverse plane (P<.001) (1.2+/-0.7 degrees vs 1.0+/-0.8 degrees for all other planes averaged). There was no significant difference between LBP and healthy control groups in the repositioning tasks. Errors in the active repositioning test were significantly smaller than in the passive repositioning test (P=.032) (1.9+/-1.2 degrees vs 2.3+/-1.4 degrees ).

CONCLUSIONS

These findings suggest that impairments in proprioception may be detected in patients with LBP when assessed with a motion perception threshold measure.

Proprioception of the wrist joint: a review of current concepts and possible implications on the rehabilitation of the wrist

STUDY DESIGN

Narrative review. Recent years have brought new research findings on the subject of wrist joint proprioception, which entails an understanding of the wrist as part of a sensorimotor system where afferent information from nerve endings in the wrist joint affects the neuromuscular control of the joint. An understanding of proprioception is also essential to adequately rehabilitate patients after wrist injuries. The aim of this narrative review was to give the reader a background of proprioception as it relates to neuromuscular control and joint stability, what is presently known in relation to the wrist joint and how these findings may be applied to the field of wrist rehabilitation.

LEVEL OF EVIDENCE

5.

Occupational hazard for pathologists: microscope use and musculoskeletal disorders

The association of prolonged microscope use with the development of chronic pain syndromes has been recognized for nearly 3 decades; yet most pathologists are not well-informed about this hazard until after they develop a problem. The purpose of this article is to make pathologists aware of this risk, discuss current pathogenetic models, and encourage them to proactively integrate prevention strategies into their daily lives.

Management of chronic soft tissue pain

Soft tissue pain is, by default, an entity of most of the other structures in the body besides bone. This includes muscle, fascia, tendons, ligaments, cartilage, synovium, fibrous capsules, organs, and nerves. Soft tissue pain is often overlooked because it is not as easy to diagnose as pain involving bony structures. However, soft tissue pain can be just as debilitating as pain from bony structures. Treatment of soft tissue pain includes a variety of pharmacologic and nonpharmacologic techniques, and these are discussed in this article.

Evidence of wrist proprioceptive reflexes elicited after stimulation of the scapholunate interosseous ligament

PURPOSE

Recent publications on the sensory innervation of wrist ligaments have challenged our understanding of ligaments as mere passive restraints in wrist stability. Mechanoreceptors in ligaments have a role in signaling joint perturbations, in which the afferent information is believed to influence periarticular muscles. The scapholunate interosseous ligament is one of the most richly innervated ligaments in the wrist. The purpose of our study was to investigate the possible existence of a wrist proprioceptive reflex, by which afferent information elicited in the scapholunate interosseous ligament was hypothesized to influence the muscles moving the wrist joint.

METHODS

Nine volunteers (4 women and 5 men; mean age, 26 years; range, 21-28 years) participated in this study. Using ultrasound guidance, a fine-wire electrode was inserted into the dorsal scapholunate interosseous ligament and stimulated with four 1-ms pulses at 200 Hz. Electromyographic activities in extensor carpi radialis brevis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris muscles were recorded using surface electrodes with the wrist actively positioned in isometric extension, flexion, and radial and ulnar deviation. The average EMGs from 30 consecutive stimulations were rectified and analyzed using the Student's t-test to compare the prestimulus (t(1)) and poststimulus (t(2)) EMG activities.

RESULTS

Statistically significant changes in poststimulus EMG activity (t(1)- t(2)) were observed at various time intervals. Within 20 ms, an excitation was seen in the flexor carpi radialis and flexor carpi ulnaris in extension, radial and ulnar deviation, and in extensor carpi radialis brevis in flexion. Co-contractions between agonist and antagonist muscles were observed, with peaks around 150 ms after stimulus.

CONCLUSIONS

We present evidence of wrist ligamento-muscular reactions. The early-onset reactions may serve in a joint-protective manner, and later co-contractions indicate a supraspinal control of wrist neuromuscular stability. These findings contribute new information to the physiologic functions of the wrist joint, which may further our understanding of dynamic wrist stability and serve as a foundation for future studies on proprioceptive dysfunctions after wrist ligament injuries.

Strain and load thresholds for cervical muscle recruitment in response to quasi-static tensile stretch of the caprine C5-C6 facet joint capsule

The aim of this study was to investigate the response of cervical muscles to physiologic tensile stretch of cervical facet joint capsule (FJC) at a quasi-static displacement rate of 0.5mm/s. In vivo caprine left C5-C6 FJC preparations were subjected to an incremental tensile displacement paradigm. EMG activity was recorded during FJC stretch from the right trapezius (TR) and multifidus (MF) muscle groups at the C5 and C6 levels and bilaterally from the sternomastoid (SM) and longus colli (LC) muscle groups at the C5-C6 level. Onset of muscular activity was later analyzed using visual and computer-based methods. Capsule load and strain at the time of onset were recorded and compared between the muscle groups. Results indicated capsule load was a better indicator of the tensile stretch thresholds for muscular recruitment than capsule strain. MF responded at significantly smaller capsule loads than TR and LC, while TR and LC activation loads were not significantly different. SM did not respond to physiologic FJC stretch. Muscle group recruitment order reflected the muscles' fiber type compositions and functional roles in the spine. This study provides the first evidence that the cervical ligamento-muscular reflex pathways are activated via tensile FJC stretch and extend to superficial and deep musculature on the anterior and posterior aspects of the neck, ipsilateral and contralateral to the side of FJC stretch.

Can ankle imbalance be a risk factor for tensor fascia lata muscle weakness?

Risk factors that can determine knee and ankle injuries have been investigated and causes are probably multifactorial. A possible explanation could be related by the temporary inhibition of muscular control following an alteration of proprioceptive regulation due to the ankle imbalance pathology. The purpose of our study was to validate a new experimental set up to quantify two kinesiologic procedures (Shock Absorber Test (SAT) and Kendall and Kendall's Procedure (KKP)) to verify if a subtalus stimulus in an ankle with imbalance can induce a non-appropriate response of controlateral tensor fascia lata muscle (TFL). Fifteen male soccer players with ankle imbalance (AIG) and 14 healthy (CG) were tested after (TEST) before (NO-TEST) a manual percussion in subtalus joint (SAT). A new tailor-made device equipped with a load cell was used to quantify TFL's strength activation in standardized positions. Two trials for each subject were performed, separated by at least one 4-min resting interval. In NO-TEST conditions both AIG and CG showed a progressive adaptation of the subject to the force imposed by operator. No reduction in mean force, mean peak force, and muscle force duration (p>0.5). AIG presented significant differences (mean difference 0.92+/-0.46 s; p=0.000) in muscle force duration in TEST conditions. Our results indicated that "wrong" proprioceptive stimuli coming from the subtalus joint in AIG might induce inhibition in terms of duration of TFL muscle altering the knee stability. This kinesiological evaluation might be useful to prevent ankle and knee injuries.

Lumbar position sense and the risk of low back injuries in college athletes: a prospective cohort study

Background

Impaired proprioception in the lumbar spine has often been reported in people with low back pain. However, no prospective studies exist to assert the cause and effect of this association. We hypothesized that athletes with a history of low back injury (LBI) would demonstrate poorer lumbar position sense (PS) than athletes without a history of LBI, and that this deficit would be a risk factor for future LBI.

Methods

This was a prospective cohort study with 2–3 year follow-up. Lumbar spine PS in the transverse plane was evaluated in 292 athletes using three tests: 1) passive and 2) active trunk repositioning, and 3) motion perception threshold. Mean absolute (accuracy) and variable (precision) errors were computed.

Results

There were no significant differences in the repositioning errors or motion perception threshold between athletes with and without a history of LBI or between those who did and did not get injured during the follow-up. Active trunk repositioning resulted in smaller errors than passive repositioning (1.6°± 0.8°) versus 2.1°± 1.0°) and 1.7°± 0.8°) versus 2.3°± 1.1°) for the absolute and relative errors, respectively).

Conclusion

Poor trunk PS in transverse plane is not associated with LBI in athletes, nor does it appear that poor trunk PS predisposes athletes to LBI.