ArticleLiterature Review

Ligaments: A source of musculoskeletal disorders

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

The mechanical and neurological properties of ligaments are reviewed and updated with recent development from the perspective which evaluates their role as a source of neuromusculoskeletal disorders resulting from exposure to sports and occupational activities. Creep, tension-relaxation, hysteresis, sensitivity to strain rate and strain/load frequency were shown to result not only in mechanical functional degradation but also in the development of sensory-motor disorders with short- and long-term implication on function and disability. The recently exposed relationships between collagen fibers, applied mechanical stimuli, tissue micro-damage, acute and chronic inflammation and neuromuscular disorders are delineated with special reference to sports and occupational stressors such as load duration, rest duration, work/rest ratio, number of repetitions of activity and velocity of movement.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... Ligaments exhibit viscoelastic properties, which influence passive joint stiffness and are important contributors to joint stability . Viscoelasticity is a time-dependent mechanical behaviour, and the non-linear relationship between stress and strain depends on the time of displacement or load (Kelc et al., 2013;Solomonow, 2009). Injury may alter these properties, with morphologic changes resulting from improper ligament healing or healing in an elongated state (Malmir et al., 2014). ...
... When a viscoelastic tissue is loaded and unloaded, the unloading curve has a different shape than the loading curve, and the amount of energy dissipated, or lost, is represented by the difference in the area under the curves (Kelc et al., 2013). Hysteresis may occur over a single stretch-release cycle, or be progressive over repeated loading, decreasing joint stability and potentially increasing the risk of injury (Solomonow, 2009). Hysteresis over repeated loading may be particularly relevant in those with a history of chronic episodes of spraining and giving way at the lateral ankle complex. ...
... These viscoelastic properties are likely to be highly variable across patients and may reflect symptom clustering (Hertel & Corbett, 2019). Few studies to date have investigated stiffness and hysteresis in the lateral ankle complex, but they may be relevant to tissue properties and the ability to withstand repeated loading without suffering injury (Malmir et al., 2014;Solomonow, 2009). ...
Article
The role of mechanical laxity and viscoelastic tissue properties in chronic ankle instability (CAI) is unclear, but may influence repeated injury. The purpose was to determine if lateral ankle complex stiffness and hysteresis was altered in CAI individuals with and without mechanical laxity, compared to copers and uninjured controls. Thirty-five recreational athletes (19 females, 22.1 ± 2.7 years, 69.7 ± 15.7 kg, 168.4 ± 10.7 cm) were assessed for ankle injury history and self-reported instability. An instrumented arthrometer was applied and laxity, stiffness and hysteresis values were captured. Results from ANOVA tests indicated the CAI with laxity group had lower beginning- (3.2 ± 0.6 N/mm) and end-range stiffness (4.5 ± 0.4 N/mm) than the CAI without laxity group (4.7 ± 0.6; 6.0 ± 0.6 N/mm) and uninjured controls (4.6 ± 1.1; 5.8 ± 0.8 N/mm, p < 0.003). Hysteresis was greater in the CAI with laxity group than without laxity (91.0 ± 17.3 vs 62.8 ± 12.0 dN•mm; p = 0.03). Altered tissue properties in a CAI with laxity group likely indicate diminished ability of the lateral ankle complex to respond to loading. Accurately assessing, then avoiding or restoring tissue impairments after injury, may encourage better patient outcomes.
... The interaction of intrinsic and extrinsic factors is key to the aetiology of soft-tissue injuries, where the characteristics of one soft-tissue may influence the risk of injury to another. For example, muscular weakness may reduce the stability around a joint, thus increasing ligament injury risk (Solomonow, 2009), and a stiffer tendon could increase the risk of strain injury to the adjoining muscle during eccentric actions (Hawkins and Bey, 1997). As most soft-tissue injuries are non-contact (Price et al., 2004;Read et al., 2018b), understanding their intrinsic (e.g. ...
... The findings of this study are supported by previous research that has identified muscle and ligament injuries as the most prevalent types of injury in YSP, with a considerable proportion of muscle injuries to the thigh (Price et al., 2004;Renshaw and Goodwin, 2016). In the present study, ligament and tendon injuries were combined due to relatively few injuries involving each tissue type, and because of similarities in tissue structure and injury aetiology (Tozer and Duprez, 2005;Solomonow, 2009). Nevertheless, the contribution of ligament and tendon injuries is similar to previous literature in youth (Price et al., 2004) and professional players (Ekstrand, Hägglund and Waldén, 2009). ...
... As well as the possible contribution of recurrent injuries in soft-tissues, it is possible that a greater frequency of training and matches in chronologically older players (Le Gall et al., 2006) influences the occurrence of muscle and ligament/tendon injuries in post-PHV players. Furthermore, ligaments and tendons have slow healing rates, and the fact that chronic inflammation leads to weakness and functional impairment and arises from insufficient rest and recovery (Yeung et al., 1994;Tozer and Duprez, 2005;Solomonow, 2009) leads us to suggest that inadequate recovery from soccer activity might contribute to the relatively high prevalence of muscle and ligament/tendon injuries amongst post-PHV players. ...
... The first propriety is the creep, i.e. its capacity to increase deformation under constant load. This relationship between stress and strain is not constant but depends on the time of displacement or load [38]. ...
... Ligaments and tendons can be damaged by either constant (creep) or cyclic (fatigue) loads, and both ef-fects may have a synergic effect with fatigue overlapped with damage accumulation, and an inflammatory response is initiated whenever the tissue is subjected to stresses which exceed its limits at a given time, without an adequate recovery time [38]. Mechanical stimuli, as a result of sports and occupational stressors such as load duration, rest duration, work/rest ratio, number of repetitions of activity and velocity of movement, can result in tissue micro-damage, with acute and chronic neuromuscular inflammation. ...
... Mechanical stimuli, as a result of sports and occupational stressors such as load duration, rest duration, work/rest ratio, number of repetitions of activity and velocity of movement, can result in tissue micro-damage, with acute and chronic neuromuscular inflammation. Fast stretch of ligaments such as in high-frequency repetitive motion is known to result in incidents with high damage or ligamentous rupture [38]. ...
Article
Background: Musculoskeletal disorders are one of the most common work-related diseases. Frequently this association is thought to have a temporal cause-effect relation. The absence of accessible diagnostic criteria and ethological cause-effect demonstration are probably important reasons for the lack of good evidence data on these pathologies. Objective: For these reasons, the authors aim to present a systematic review on prevalence and incidence of the upper limb WRMSD. Methods: The survey was conducted for papers published between January 1st, 2000 and July 2012, according to the PRISMA statement (2009) guidelines. Results: From the 2016 papers obtained, 94 met the qualitative selection criteria. From these 27 address upper-limb WRMSD, and 17 present data on prevalence or incidence on upper-limb musculoskeletal diseases, six of them with a control group. Annual incidence ranges from 0.08 to 6.3, and prevalence from 0.14 to 14.9. Rotator cuff syndrome among shoe industry workers, present the highest incidence, and cubital, radial or ulnar nerve entrapment, the highest prevalence among a miscellaneous group of workers. Conclusions: More studies are needed to clarify the relation between work and WRMSD's, especially prospective investigations from different economic sectors and work activities, but with similar, reproducible and comparable methodologies.
... Estimating external workload in baseball pitchers is important for training and rehabilitation. To build strength and resilience in musculoskeletal tissues, it is necessary to overload the tissue using a magnitude that promotes positive adaptation [1]. However, if the magnitude of loading exceeds tissue tolerance, it can cause injury. ...
... However, if the magnitude of loading exceeds tissue tolerance, it can cause injury. Repetitive cycles of loading without adequate recovery time can also negatively impact soft tissue structures and increase susceptibility to injury, particularly for high-velocity movements [1]. ...
Article
Full-text available
Estimating external workload in baseball pitchers is important for training and rehabilitation. Since current methods of estimating workload through pitch counts and rest days have only been marginally successful, clubs are looking for more sophisticated methods to quantify the mechanical loads experienced by pitchers. Among these are the use of wearable systems. While wearables offer a promising solution, there remains a lack of standards or guidelines for how best to employ these devices. As a result, sensor location and workload calculation methods vary from system to system. This can influence workload estimates and blur their interpretation and utility when making decisions about training or returning to sport. The primary purpose of this study was to determine the extent to which sensor location influences workload estimate. A secondary purpose was to compare estimates using different workload calculations. Acceleration data from three sensor locations—trunk, throwing upper arm, and throwing forearm—were collected from ten collegiate pitchers as they threw a series of pitches during a single bullpen session. The effect of sensor location and pitch type was assessed in relation to four different workload estimates. Sensor location significantly influenced workload estimates. Workload estimates calculated from the forearm sensor were significantly different across pitch types. Whole-body workload measured from a trunk-mounted sensor may not adequately reflect the mechanical loads experienced at throwing arm segments. A sensor on the forearm was the most sensitive to differences in workloads across pitch types, regardless of the calculation method.
... The involved mechanical forces (tension, compression, shear) applied to the spine, once surpassing thresholds, can trigger nociceptive signals via mechanical nociceptors embedded in these tissues. Since many spinal structures (eg, joint capsule, the peripheral third of intervertebral discs, tendons, muscles, and ligaments [13][14][15] ) have these nociceptors, there are mechanical scenarios that could theoretically provoke a pain experience in sitting. Studies have confirmed the biological plausibility of these pathways to pain: that stretching of the posterior passive tissues of the spine (ligaments, tendons, and joint capsules) instigates inflammatory and cytokine responses, 15 that pain is perceived at lower thresholds when inflammation is present, 16 that spine flexion results in stress at the peripheral third of the intervertebral disc (secondary to the posterior migration of the nucleus 17 ), and that sustained low-level activation of the erector spinae muscles, as occurs in seated postures, results in capillary compression and reduced oxygenation. ...
... Since many spinal structures (eg, joint capsule, the peripheral third of intervertebral discs, tendons, muscles, and ligaments [13][14][15] ) have these nociceptors, there are mechanical scenarios that could theoretically provoke a pain experience in sitting. Studies have confirmed the biological plausibility of these pathways to pain: that stretching of the posterior passive tissues of the spine (ligaments, tendons, and joint capsules) instigates inflammatory and cytokine responses, 15 that pain is perceived at lower thresholds when inflammation is present, 16 that spine flexion results in stress at the peripheral third of the intervertebral disc (secondary to the posterior migration of the nucleus 17 ), and that sustained low-level activation of the erector spinae muscles, as occurs in seated postures, results in capillary compression and reduced oxygenation. 18 Further, a pain response is also evident in experimental studies, where increased reports of perceived pain have been observed in young, healthy populations in response to sitting durations greater than 1 hour. ...
Article
Objective: The purpose of this study was to conduct a systematic review of studies to determine whether sitting time measured objectively (by laboratory controlled time trial, direct observation, or wearable sensor) is associated with the immediate increase in low back pain (LBP) (determined by pain scale rating) in people >18 years of age. Methods: Four databases (PubMed, EMBASE, SPORTDiscus, and Cumulative Index to Nursing and Allied Health Literature) were searched from inception to September 1, 2018. Randomized controlled trials and cohort and cross-sectional studies, where objectively measured sitting time was temporally matched with a measure of LBP in adults, were included. Studies without a control session conducted on a separate day were excluded. Screening, full-text review, data extraction, and risk of bias assessment (Quality In Prognosis Studies) of included papers were performed independently by 2 reviewers, with a third available to resolve disagreements. Results: In total, 609 articles were identified, 361 titles/abstracts were screened,75 full-text articles were assessed for eligibility, and 10 met the inclusion criteria. All but 1 reported sitting time to be associated with an immediate increase in LBP. Six of these reported clinically relevant pain levels (n = 330). Half of the included studies were rated as having a low risk of bias and the remaining were rated as having a moderate risk of bias. Conclusion: Prolonged sitting increases immediate reporting of LBP in adults; however, no conclusion between sitting and clinical episodes of LBP can be made. Based upon these findings, we recommend that future prospective studies should match objectively measured sitting with temporally related pain measurements to determine whether prolonged sitting can trigger a clinical episode of LBP.
... The magnitude of the effects depends on duration of exposure (and rest), type of loading (creep loading or stress-relaxation, static or cyclic loading), load magnitude (e.g. flexion angle, flexion rate, external load), temperature and ligamentous material characteristics (Solomonow, 2009). ...
... There is also an important consideration of time-dependent recovery of viscoelastic creep and sensorimotor control. In the first hour after 20 to 50 min of tensile stress of the spinal ligaments, there is about 50% of the initial mechanical characteristics of the ligaments (Solomonow, 2009), while deterioration in balance (when sitting on unstable surface) due 10 min of full lumbar flexion, is evident just in the first 10 min after exposure (Hendershot et al., 2013). Additionally, a few minutes of rest after prolonged sitting (before engaging in demanding physical work) was often proposed in order to reduce the risk of bending injury. ...
Article
Full-text available
Introduction: Prolonged sitting is often proposed as a risk factor for low back pain development. The purpose of this study was to evaluate the acute effect of full time office work on sensorimotor trunk functions. Methods: Seventeen healthy office workers participated in the study. Maximal lumbar flexion range of motion, anticipatory postural adjustments and postural reflex reactions were tested before and after full time office work in a real life environment. Results: There were longer onset latencies of postural reflexive reactions and decreased response amplitudes of anticipatory postural adjustments after full time office work, but these were significant only for the obliquus externus abdominis muscle. No changes in lumbar range of motion was found. Conclusion: To our knowledge this is the first study that evaluates the effect of full time office work on postural actions and lumbar RoM. We found an absence of normal human circadian flexibility in the lumbar spine and some changes in postural actions. We propose that active trunk stiffness increase to compensate for decreased passive stiffness after prolonged seated work. Further studies are needed to confirm this assumption.
... Sitters habitually assume slumped sitting postures with varying degrees of lumbar flexion (Callaghan and McGill, 2001a;O'Sullivan et al., 2010) because it increases discomfort to maintain a neutral sitting posture due to the sustained isometric muscular exertions (Vergara and Page, 2002a); 2 The large intervertebral discs that provide cushioning and flexibility between the vertebrae are squeezed at their forward edge (during slumped sitting), causing bulging on the posterior surface (Alexander et al., 2007;Nazari et al., 2012). Sustained static compression decreases fluid exchange and nutrition in the discs (Holm and Nachemson 1983), resulting in reduced load carrying capacity of the spinal segment (Owens et al., 2009) and degeneration of the lumbar disc (Huang et al., 2016;Kos et al., 2019); 3 In a flexed or slumped sitting posture, the posterior spinal ligaments and fascia are stretched to capacity (Snijders et al., 2004), leaving the sacro-iliac joints and lumbar spine unstable (O'Sullivan et al., 2006); 4 Prolonged sitting in a flexed posture causes creep and laxity, leading to inflammation in the ligaments surrounding the spine, leaving the back vulnerable to injury the following day (Solomonow, 2009); 5 When office workers maintain a static lumbar flexion position (kyphotic) for hours, it adds strain on the spine caused by the sustained posture (Le et al., 2009). The discs, ligaments and supporting muscles of the spine need to constantly cycle through exertion and recovery, compression and decompression, in order to absorb nutrition and discharge metabolites (McMillan et al., 1996). ...
... El comúnmente usado terminó "relajación o liberación tisular", en relación al resultado del tratamiento de los desequilibrios musculares, es típicamente razonado desde una perspectiva estructural y mecánica (154). El tejido conectivo es conocido por estirarse tras una carga estática debido a sus propiedades viscoelásticas innatas; sin embargo, este efecto es transitorio y dependiente de la duración y el modo de estiramiento (155). El fenómeno palpable de liberación descrito por profesionales, puede ser explicado por una modificación de la sensación nociceptiva o de cambios reflejos (156,157). ...
Thesis
Effects of diaphragm muscle treatment in shoulder pain and mobility in subjects with rotator cuff injuries. Introduction: The rotator cuff inflammatory or degenerative pathology is the main cause of shoulder pain. The shoulder and diaphragm muscle have a clear relation through innervation and the connection through myofascial tissue. In the case of nervous system, according to several studies the phrenic nerve has communicating branches to the brachial plexus with connections to shoulder key nerves including the suprascapular, lateral pectoral, musculocutaneous, and axillary nerves, besides, the vagal innervation that receives the diaphragm and their connections with the sympathetic system could make this muscle treatment a remarkable way of pain modulation in patients with rotator cuff pathology. To these should be added a possible common embryological origin in some type of vertebrates. Considering the connection through myofascial system, the improving of chest wall mobility via diaphragm manual therapy could achieve a better function of shoulder girdle muscles with insertion or origin at ribs and those that are influenced by the fascia such as the pectoralis major muscle, latissimus dorsi and subscapularis. Objectives: • Main objective: To compare the immediate effect of diaphragm physical therapy in the symptoms of patients with rotator cuff pathology regarding a manual treatment over shoulder muscles. • Specific objectives: 1. To evaluate the immediate effectiveness of each of the three groups in shoulder pain using a numerical pain rating scale (NPRS) and compare between them. 27 2. To evaluate the immediate effectiveness of each of the three groups in shoulder range of motion (ROM) using an inclinometer and compare between them. 3. To evaluate the immediate effectiveness of each of the three groups in pressure pain threshold (PPT) using an algometer and compare between them. Material and method: A prospective, randomized, controlled, single-blind (assessor) trial with a previous pilot study in which a final sample size of 45 subjects was determined to people diagnosed with rotator cuff injuries and with clinical diagnosis of myofascial pain syndrome at shoulder. The sample were divided into 3 groups of treatment (15 subjects per group): 1. A direct treatment over the shoulder by ischemic compression of myofascial trigger points (MTP) (control / rotator cuff group). 2. Diaphragm manual therapy techniques (diaphragm group). 3. Active diaphragm mobilization by hipopressive gymnastic (hipopressive group). The pain and range of shoulder motion were assessed before and after treatment in all the participants by inclinometry, NPRS of pain in shoulder movements and algometry. The data obtained were analyzed by an independent (blinded) statistician, who compared the effects of each one of the treatments using the Student’s t-test for paired samples or the Wilcoxon signed rank test, and calculated the post -intervention percentage of change in every variable. An analysis of variance (ANOVA) followed by the post-hoc test or a non-parametric Kruskal-Wallis test for non-parametric multiple-groups comparisons were performed to compare pre- to post-intervention outcomes between groups. Effect-size estimates of each intervention and between groups were calculated to allow interpretation of results in a more functional and meaningful way. Results: Both the control group and diaphragm group showed a statistically (p< 0.005) and clinically significant improvement, as well as a significant effect size (moderate to strong), on the NPRS in shoulder flexion and abduction movements. Regarding NPRS in shoulder external rotation, only the control group obtained a significant effect size. There was a significant increase in shoulder abduction and external rotation ROM (p< Efectos del tratamiento del músculo diafragma en el dolor y la movilidad del hombro en sujetos con patología del manguito rotador. 28 0.001) with a significant effect size in the control group. The PPT at the xiphoid process of the sternum showed a statistically (p< 0.001) and clinically significant improvement in the diaphragm group. The hipopressive gymnastic treatment was found to be no clinically effective in the shoulder pain and mobility, and showed a less efficacy than the other two groups. Conclusion: Both the shoulder non-direct treatment by a protocol of diaphragm manual therapy techniques and the rotator cuff MTP intervention showed been clinically effective in reducing pain (NPRS) immediately in shoulder flexion and abduction movements. The ROM assessment improvements obtained post- intervention by the diaphragm group have not been enough to consider them as clinically significant. The control group has obtained a significant effect size in shoulder abduction and external rotation ROM improvement. Both the control group and the diaphragm group treatments have been more effective in improving shoulder pain and mobility than the hipopressive group. The control group intervention has been the most effective in improving shoulder external rotation pain and mobility. The diaphragm group intervention was more effective in improving PPT at the xiphoid process than the other groups. Neither the effect size nor clinical significance proves the short-term benefit of the hipopressive gymnastic treatment in shoulder pain and mobility. Future studies are necessary to show the effectiveness of the diaphragm manual therapy applied in several sessions to determine its long-term effects in shoulder pain and mobility.
... Contudo, existe uma carência de modelos topográficos e histológicos que expliquem as interações entre o alongamento e as repercussões funcionais que ocorrem nos tecidos adjacentes, tais como tendões, nervos, ligamentos e fáscia (77). A comparação dos resultados da terapia com exercícios de alongamento em artigos clínicos apresenta limitações devido à falta de padronização, decorrente de protocolos diferentes que variam quanto à intensidade, à duração, à frequência dos movimentos e ao tempo que deveria ser despendido com o alongamento terapêutico, a fim de provocar os efeitos fisiológicos desejados (78,79). ...
... Contudo, existe uma carência de modelos topográficos e histológicos que expliquem as interações entre o alongamento e as repercussões funcionais que ocorrem nos tecidos adjacentes, tais como tendões, nervos, ligamentos e fáscia (77). A comparação dos resultados da terapia com exercícios de alongamento em artigos clínicos apresenta limitações devido à falta de padronização, decorrente de protocolos diferentes que variam quanto à intensidade, à duração, à frequência dos movimentos e ao tempo que deveria ser despendido com o alongamento terapêutico, a fim de provocar os efeitos fisiológicos desejados (78,79). ...
... If a constant (or a repetitive) longstanding stress is applied to collagenous tissue, the tissue slowly starts to lengthen through this force. After several hours of loading, the recovery of the collagenous fibres is not immediate and the structures remain elongated (hysteresis) (Bogduk 2008, King et al. 2009, LaBry et al. 2004, Solomonow 2009). With animal models, it has been shown that 7 hours of creep causes a hysteresis that lasts for about same 7 hours in relaxation (King et al. 2009, DʹAmbrosia et al. 2010. ...
... important proprioceptive role. 40 General knee joint stability and function are typically impaired after ACL rupture, 15 and many patients who have ACL deficiency are not able to recover sufficient knee stability without significant functional deficits. 15 Consequently, a majority of patients with ACL-deficient knees undergo ACL reconstruction (ACLR) to recover mechanical knee joint stability. ...
Article
Background Anterior cruciate ligament (ACL) rupture is a serious injury with a high prevalence worldwide, and subsequent ACL reconstructions (ACLR) appear to be most commonly performed using hamstring-derived (semitendinosus tendon) autografts. Recovery of maximal muscle strength to ≥90% of the healthy contralateral limb is considered an important criterion for safe return to sports. However, the speed of developing muscular force (ie, the rate of force development [RFD]) is also important for the performance of many types of activities in sports and daily living, yet RFD of the knee extensor and flexor muscles has apparently never been examined in patients who undergo ACLR with hamstring autograft (HA). Purpose To examine potential deficits in RFD, maximal muscle strength (ie, maximal voluntary isometric contraction [MVIC]), and functional capacity of ACLR-HA limbs in comparison with the healthy contralateral leg and matched healthy controls 3 to 9 months after surgery. Study Design Cross-sectional study; Level of evidence: 3. Methods A total of 23 young patients who had undergone ACLR-HA 3 to 9 months earlier were matched by age to 14 healthy controls; both groups underwent neuromuscular screening. Knee extensor and flexor MVIC and RFD, as well as functional capacity (single-leg hop for distance [SLHD] test, timed single-leg sit-to-stand [STS] test), were assessed on both limbs. Furthermore, patient-reported knee function (Knee injury and Osteoarthritis Outcome Score) was assessed. Results Knee extensor and flexor MVIC and RFD were markedly compromised in ACLR-HA limbs compared with healthy contralateral limbs (MVIC for extensor and flexor, 13% and 26%, respectively; RFD, 14%-17% and 32%-39%) and controls (MVIC, 16% and 31%; RFD, 14%-19% and 30%-41%) ( P < .05-.001). Further, ACLR-HA limbs showed reduced functional capacity (reduced SLHD and STS performance) compared with contralateral limbs (SLHD, 11%; STS, 14%) and controls (SLHD, 20%; STS, 31%) ( P < .01-.001). Strength (MVIC) and functional (SLHD) parameters were positively related to the duration of time after surgery ( P < .05), although this relationship was not observed for RFD and STS. Conclusion Knee extensor and flexor RFD and maximal strength, as well as functional single-leg performance, remained substantially reduced in ACLR-HA limbs compared with noninjured contralateral limbs and healthy controls 3 to 9 months after reconstructive surgery.
... 3,4 Joint and ligamentous hypomobility may inhibit the activation of surrounding muscles or muscle synergists. 5,6 Hypomobile spinal joints may also inhibit muscle function within the specific myotome. 7 An early randomized controlled trial found quadriceps strength was significantly increased after manipulation to the L3-L4 lumbar segments. ...
Article
Clinical Scenario : Many people with lower quarter musculoskeletal dysfunction present with muscle weakness. Strength training hypertrophies muscle and increases strength, but often requires periods over 6 weeks, which can exceed the episode of care. Weakness can persist despite muscle hypertrophy, particularly in the early stages of joint pathology or in the presence of limb or spinal joint hypomobility, which may inhibit muscle activation. Emerging evidence suggests spinal manipulation can increase short-term strength. Screening for specific muscle weakness that could benefit from manipulation to particular spinal segments could facilitate efficient clinical intervention. Although the neuromuscular mechanisms through which manipulation can increase strength remains a topic of investigation, immediate gains can benefit patients by jump-starting an exercise program to train new muscle function gained and enhancing the motivation to continue strengthening. Evidence from randomized controlled trials would provide support for using manipulation to increase muscle strength, while studying healthy people would eliminate confounding factors, such as pain and pathology. Clinical Question : Does randomized controlled trial-level evidence support the concept that a single lumbar spine manipulation session can increase lower-limb strength in healthy individuals? Summary of Key Findings : Level 1b evidence of moderate quality from 3 randomized controlled trials showed immediate small to large effect size muscle strength increases immediately after lumbar spine manipulation. Clinical Bottom Line : Lumbar spine manipulation can result in immediate lower-limb isometric strength increases. While healthy people with normal muscle strength may improve minimally, joint manipulation for people with knee and hip weakness who are otherwise healthy can result in large effect size strength gains. Strength of Recommendation : Moderate quality level 1b evidence from randomized controlled trials with small samples support the use of spinal manipulation to immediately increase lower-limb strength. Additional studies investigating impact on strength and function immediately in people with musculoskeletal pathology are warranted.
... Furthermore, Hendershot et al. [37] found that prolonged exposure to trunk flexion resulted in lower stiffness of passive vertebral structures during trunk sudden loading applied in standing position (neutral spine alignment). Consequently, the reflexive onset of activity of back muscles could be delayed because of an excessive ligamental laxity [38,39]. In the latter case, high RER among kayakers/canoeists could represent a compensatory mechanism of decreased stiffness of passive tissues. ...
Article
Full-text available
Trunk stability functions play an important role in sport and everyday movements. The aim of this study was to analyze trunk strength, trunk muscles onset of activity, and rate of electromyographic rise (RER) in the case of self-inflicted and unexpected trunk loading. Thirty-two healthy young adults (16 elite kayakers/canoeists and 16 non-athletes) were measured with a multi-purpose diagnostic machine. Trunk strength was assessed in standing position. Trunk muscles onset of activity and RER were assessed through unexpected loading over the hands and rapid shoulder flexion, respectively. In comparison with non-athletes, kayakers/canoeists did not significantly differ in trunk strength and showed lower trunk extension/flexion strength ratio (p = 0.008). In general, trunk muscles onset of activity did not significantly differ between the groups. On the contrary, kayakers/canoeists showed higher RER mean values in all the observed muscles (p < 0.041), except in multifidus muscle during self-inflicted movements. Similarly, higher RER variability was observed in the majority of the observed muscles among kayakers/canoeists. Higher RER among kayakers/canoeists could represent a protective mechanism that ensures spine stability and prevents low back pain.
... Sufficient stretching of passive structures within the elastic zone will trigger mechanoreceptor responses generating proprioceptive information, potentially improving sensory-motor control via appropriate and coordinated motor responses (Holm et al. 2002;Panjabi 1992a). It has been often proposed that increasing length and tension in the passive structures is associated with an increase in muscular activation to maintain joint stability (ligamento-muscular reflex; Solomonow 2006Solomonow , 2009. ...
Article
Preview Abstract Introduction: In complex anatomical systems, such as the trunk, motor control theories suggest that many motor solutions can be implemented to achieve a similar goal. While reflex mechanisms act as a stabilizer of the spine, how the central nervous system uses the trunk redundancy to adapt the neuromuscular responses under the influence of external perturbations, such as experimental pain or spinal tissue creep is still unclear. The aim of this study was to identify and characterize trunk neuromuscular adaptations in response to unexpected trunk perturbations under the influence of spinal tissue creep and experimental back pain. Methods: Healthy participants experienced a repetition of sudden external trunk perturbations in two protocols: [1] 15 perturbations before and after a spinal tissue creep protocol, [2] 15 perturbations with and without experimental back pain. Trunk neuromuscular adaptations were measured using high-density electromyography to record erector spinae muscle activity recruitment patterns and using a motion analysis system. Results: Muscle activity reflex attenuation was found across unexpected trunk perturbation trials under the influence of creep and pain. A similar area of muscle activity distribution was observed with or without back pain, as well as before and after creep. No change of trunk kinematics was observed. Conclusion: While under normal circumstances muscle activity adaptation occurs throughout the same perturbations, a reset of the adaptation process is present when experiencing a new perturbation such as experimental pain or creep. However, participants are still able to attenuate reflex responses under these conditions using variable recruitment pattern of back muscles.
... As a result of creep deformation and load-relaxation in soft tissues, the sensitivity of ligament mechanoreceptors (Granata et al., 2005;Rogers and Granata, 2006;Solomonow et al., 2000) and muscle spindle excitability can change (Avela et al., 1999;Granata et al., 2005). Accordingly, prolonged flexion have been associated with impaired reflexive responses and a decrease in the excitability of the ligamento-muscular reflex arc (Cholewicki et al., 2005;Hendershot et al., 2011;Solomonow, 2009). Afferents of both muscle spindles and mechanoreceptors in the ligamento-capsular structures provide essential information for optimal spinal motor control to maintain appropriate postures and identify errors during postural changes (Korakakis et al., 2017;Panjabi, 2003;Tong et al., 2017). ...
... Propolis has enormous medical and economic importance, being marketed in several pharmaceutical and cosmetic preparations such as toothpastes, lotions, facial creams, tinctures, ointments, and others [27,28]. It has been observed a significant increase in the public interest for this product, in the number of bee breeders who invests in improving the production of propolis and in processing companies of this material [29]. ...
Article
Full-text available
Propolis is a resinous substance obtained by bees, whose antibacterial, anti-inflammatory, antiviral, antifungal, immune stimulant, and local anesthetic wound healing properties have been considered for clinical practice. In particular, its anti-inflammatory and antibacterial characteristic seems to be a novel target for infectious process from dental origin. This work aimed to evaluate the propolis antibacterial potential against a bacterial endotoxin on dental alveoli. First, some properties of green propolis extract were analyzed (in vitro): 1) physicochemical profile 2) Minimum Inhibitory Concentration (MIC) against endotoxin from Gram negative Escherichia coli, and 3) its immunoregulatory activity on leukocytes from the spleen of rats. Then, an inflammatory process was induced in rats by a contamination with lipopolysaccharide (LPS) that is recognized as an endotoxin. For this purpose, rats were subjected to extractions of maxillary first molars, right and left, which immediately had the right dental socket contaminated with 0.1L of LPS (100 μg/kg). After 14 days from exodontia, these individuals were divided in groups treated with Pure Propolis Extract (EPP) and groups without therapy. The contaminated alveolar bone or the same area from animals without inflammation-induced were removed for histological and immunohistochemical processing. Our data reveal an important therapeutic action from green propolis. In vitro tests indicated low cytotoxicity for this compound. By a hematoxilin and eosin analysis, the group infected and treated with propolis presented the alveoli with more new bone tissue, characterized by bony trabeculae circling small cavities filled by a loose connective tissue containing blood vessels. Additionally, a histochemical marker of osteoclasts, tartrateresistant acid phosphatase (TRAP), was used to determine the new bone formation rate. The propolis induced more TRAP formation on alveolar bone infected by LPS. Our findings highlight the potential of propolis to be applied in dental material.
... Previous studies of the impact of exposure to flexed postures on the lumbar spine attributed changes in its mechanical properties, including increases in the lumbar flexion range of motion (ROM) (McGill and Brown, 1992;Sánchez-Zuriaga et al., 2010;Shin and Mirka, 2007; and reductions in trunk stiffness , to creep deformation and loadrelaxation of posterior passive tissues. In addition, passive stretch of posterior soft tissues during prolonged flexion was shown to affect the muscle spindle excitability and the sensitivity of ligaments mechanoreceptors, thereby leading to impaired ligamentmuscle reflexive responses (Cholewicki et al., 2005;Hendershot et al., 2011;Rogers and Granata, 2006;Solomonow, 2009;2011;Solomonow et al., 2000). Accordingly, a spinal flexed posture and subsequent disturbance of reflexive behavior may increase the risk of injury due to spinal instability Hendershot et al., 2011 Interactions between three systems are responsible for the maintenance of spinal stability: an active muscle system, a passive soft tissue system, and a neural control system, which coordinates the interaction between the active and passive systems (Panjabi, 1992). ...
Article
Occupations that involve sustained or repetitive neck flexion are associated with a higher incidence of neck pain. Little in vivo information is available on the impact of static neck flexion on cervical spinal tissue. The aim of this study was to assess changes in mechanical and neuromuscular behaviors to sustained neck flexion in healthy adults. Sixty healthy subjects aged 20-35 years participated in this study. The participants were exposed to static neck flexion at a fixed angle of full flexion for 10 min. Mechanical and neuromuscular responses of the cervical spine to sudden perturbations were measured pre- and post-exposure. Magnitude of load-relaxation during flexion exposure, stiffness, peak head angular velocity, and reflexive activities of cervical muscles were recorded. Effective neck stiffness decreased significantly, especially in female participants (P = 0.0001). The reflexive response of the cervical erector spinae muscles to head perturbation delayed significantly (P = 0.0001). Peak head angular velocity was significantly increased after exposure to neck flexion for 10 min, especially in female participants (P = 0.001). In the present study, static flexion resulted in changes in mechanical and neuromuscular behavior of the cervical spine, potentially leading to decreased stiffness of the cervical spine. The results confirm the importance of maintaining a correct head and neck position during work and improving the work environment to reduce the cervical spinal load and work-related neck pain.
... We use routinely the pegboard for treating rigidities with application times of at least 20 min. The choice at this duration is based on previous studies showing that it allows elongation of the connective tissue in the supraspinose ligament [18]. ...
Article
Full-text available
Background The stiff hand is a still common, severe complication of hand injuries. Case presentationWe report here the case of a 56 year-old woman, professional goldsmith, who suffered a distal radius fracture of her right hand. The patient was treated with surgery followed by four weeks of immobilization, and developed a stiff hand. Physical examination showed mild inflammatory signs, pain and a major limitation in the extension and supination of the wrist, and in the mobility of the II, III, IV and V metacarpophalangeal (-5° and 32° of average passive extension and flexion, respectively) and interphalangeal (-35° and 73° of average passive extension and flexion, respectively) joints. There was a lack of slip of the flexor tendons. The diagnosis of complex regional pain syndrome was considered although it could not be definitely established. After five months of adverse evolution the patient was referred to our center where a combined intervention with paraffin, manual therapy, prolonged active and passive stretch on a pegboard, and splinting was applied. After initiation of this therapy, a marked change in the evolution of the pain, the mobility and functionality of the hand was observed. At the end of the rehabilitation program the patient was able to fully resume her job. Conclusion The present case illustrates the need of intensive treatment for post-traumatic hand stiffness, and describes, as an original contribution, a combined intervention therapy including paraffin, manual therapy, pegboard and splinting.
... As a result of stress relaxation, when a constant flexed posture is required, stress in the passive tissues gradually decreases, requiring a shift in force distribution from passive to active structures. Both creep and relaxation involve timedependent changes in the mechanical properties of the passive viscoelastic tissues [14,16,17]. In line with this, Olson, Li and Solomonow [18] showed that passive trunk flexion induces sustained deformation of the passive tissues. ...
Article
Full-text available
The goal of the present study was to determine the effects of prolonged, intermittent flexion on trunk neuromuscular control. Furthermore, the potential beneficial effects of passive upper body support during flexion were investigated. Twenty one healthy young volunteers participated during two separate visits in which they performed 1 hour of intermittent 60 seconds flexion and 30 seconds rest cycles. Flexion was set at 80% lumbar flexion and was performed with or without upper body support. Before and after intermittent flexion exposure, lumbar range of motion was measured using inertial measurement units and trunk stability was assessed during perturbations applied in the forward direction with a force controlled actuator. Closed-loop system identification was used to determine the trunk translational admittance and reflexes as frequency response functions. The admittance describes the actuator displacement as a function of contact force and to assess reflexes muscle activation was related to actuator displacement. Trunk admittance gain decreased after unsupported flexion, while reflex gain and lumbar range of motion increased after both conditions. Significant interaction effects confirmed a larger increase in lumbar range of motion and reflex gains at most frequencies analysed following unsupported flexion in comparison to supported flexion, probably compensating for decreased passive tissue stiffness. In contrast with some previous studies we found that prolonged intermittent flexion decreased trunk admittance, which implies an increase of the lumped intrinsic and reflexive stiffness. This would compensate for decreased stiffness at the cost of an increase in cumulative low back load. Taking into account the differences between conditions it would be preferable to offer upper body support during activities that require prolonged trunk flexion.
... The commonly used term 'Tissue Release' in relation to treatment outcomes of muscular imbalances is typically approached from a mechanistic and structural perspective ( Schleip, 2003). Connective tissue is known to lengthen under static load due to its innate viscoelastic properties; however, this effect is transient and dependent upon duration and mode of stretch ( Chaudhry et al., 2007;Solomonow, 2009). The palpable phenomenon of a 'Release' that is described by clinicians can be explained by a modification of nociceptive sensation or reflexive changes ( Chaudhry et al., 2008;Konrad and Tilp, 2014;Weppler and Magnusson, 2010). ...
Article
In clinical practice, Osteopaths and Manual Therapists commonly direct treatment towards the diaphragm by the use of a ‘Diaphragm Release’. Currently, there is paucity within the literature to support the use of this technique, specifically in pain outcomes. This research aims to support a neurophysiological mechanism based upon the osteopathic principle “The body is a unit”. Demonstrating that directing treatment to distal tissue which is neurologically related can reduce pain in the originating spinal segments. This study investigated the immediate hypoalgesic effects of a ‘Diaphragm Release’ on pain pressure thresholds in the cervical spine. A single-blind, randomised, sham-controlled, repeated measures within subject, crossover design was conducted on 17 asymptomatic subjects. Pain pressure thresholds were measured bilaterally in the C4 paraspinal musculature, lateral end of the clavicle and upper third of the tibialis anterior before and after a ‘Diaphragm Release’. Results demonstrated a statistically significant hypoalgesic effect was only found in the spinal segment C4 in both the right (p= 0.016) and left (p= 0.004) sides. Averaging the hypoalgesic effect from both sides equates to a 17.17% change which is considered clinically significant, the effect magnitude was calculated to be small but educationally significant for the right (d= 0.26) and left (d= 0.40) sides. This study supports a novel neurophysiological mechanism, Regional Interdependent Inhibition, to induce a hypoalgesic state at segmentally related spinal segments, specifically C4. Suggesting that directing treatment towards the diaphragm, using a ‘Diaphragm Release’, could induce an immediate clinically and statistically significant hypoalgesic effect local to the fourth cervical segment due to its relationship with the phrenic nerve.
... As a matter of fact, the exposition to ergonomic risk results in injuries to the musculoskeletal system by causing an excessive stress on the viscoelastic tissue (SOLOMONOW, 2009). The main ergonomic risk factors include repeatability, use of excessive force, vibration, forced positions, contact stress, exposition to extreme temperatures, and static overload. ...
Article
Full-text available
The ergonomic risk resulted by the footwear assembly has contributed towards the occurrence of Work-related Musculoskeletal Disorders (WMSDs) in this branch of industry. The main goal is to assess the ergonomic risk for WMSDs in upper limbs in activities of footwear assembly, ascertaining the intersectoral differences. 63 activities were assessed in the three biggest assembly sectors of a footwear factory: Sector 1 (S1) – cemented sports footwear, Sector 2 (S2) – vulcanized sports footwear, and Sector 3 (S3) – waterproof footwear. To assess the ergonomic risk for WMSDs, it was used the Occupational Repetitive Actions (OCRA) method. Measures of central tendency and non-parametric tests considering α<0,05 were used to ascertain the existence of discrepancies between the sectors. It was verified significant differences between S1 and S3 and between S2 and S3 both for the right and left upper limb. Nevertheless, these discrepancies were not observed between S1 and S2.
... Further, viscoelastic changes in the mechanical behavior of spinal ligaments can lead to sensory motor disturbances. 42 Creep deformation of spinal ligaments has been recognized to be associated with delayed and reduced stretch-reflex response of trunk muscles, which plays an important role in providing spinal stability. 32 Therefore, it is also important to investigate age-related differences in disturbances to reflexive behavior of trunk neuromuscular system following viscoelastic changes in the mechanical behavior of spinal ligaments. ...
Article
Low back pain is a leading cause of disability in the elderly. The potential role of spinal instability in increasing risk of low back pain with aging was indirectly investigated via assessment of age-related differences in viscoelastic response of lower back to passive deformation. The passive deformation tests were conducted in upright standing posture to account for the effects of gravity load and corresponding internal tissues responses on the lower back viscoelastic response. Average bending stiffness, viscoelastic relaxation, and dissipated energy were quantified to characterize viscoelastic response of the lower back. Larger average bending stiffness, viscoelastic relaxation and dissipated energy were observed among older vs. younger participants. Furthermore, average bending stiffness of the lower back was found to be the highest around the neutral standing posture and to decrease with increasing the lower back flexion angle. Larger bending stiffness of the lower back at flexion angles where passive contribution of lower back tissues to its bending stiffness was minimal (i.e., around neutral standing posture) highlighted the important role of active vs. passive contribution of tissues to lower back bending stiffness and spinal stability. As a whole our results suggested that a diminishing contribution of passive and volitional active subsystems to spinal stability may not be a reason for higher severity of low back pain in older population. The role of other contributing elements to spinal stability (e.g., active reflexive) as well as equilibrium-based parameters (e.g., compression and shear forces under various activities) in increasing severity of low back pain with aging should be investigated in future.
... On bipedal posture, the gravity distribution on the spine works in balance with the muscular forces that are directly proportional to the spine direction and pelvic tilt [19]. Solomonow [21], describes that the muscles associated with the joints have an important role as limiters of the movement and therefore as joint stabilizers, and in some joints, such as intervertebral, the muscle function as stabilizer is amplified. Based on this assumption, on all fours posture, there is no unidirectional gravitational action with the muscle fibers of the trunk, neither unloading of this weight compatible with the spinal direction. ...
Article
Objectives: Osteopenia and osteoporosis are quite prevalent in children with Cerebral Palsy and the percentage of these children with a history of fractures is high. In the past decade there have been methods and protocols within the suit therapy characterized by garments with adjustable elastic bands and the possibility of applying load on the human skeleton for improved bone mineral density. The aim of this study was to analyze the histomorphometric bone of dorsal and lumbar vertebrae, and to quantify serum levels of osteocalcin, after using an experimental model of suit therapy in Wistar rats. Methods: The sample included 30 male Wistar rats. It was made for animals, an experimental model of the “suit”, adapted and arranged in two elastic “X” to approach the spine by means of traction load resulting in 50% of the weight of the animal. They remained two hours daily with the suit, 5 consecutive days and four weeks of trial, a total of 40 hours. Results: There was no statistical result for cortical thickness, and osteocytes counts and percentages of the trabecular porous area in the dorsal and lumbar vertebrae. Conclusion: There was no change in bone tissue of the dorsal and lumbar vertebrae with the spinal compression performed by the traction bands of the suit in this experimental model.
Article
Recently, scientists have utilized a range of techniques in the attempt to model ligamentous structures, which play a vital role in the functioning of the human body. Therefore, our objective is to conduct a systematic scoping review that evaluates the scope of 163 journals pertaining to computational modeling of ligaments, while also assessing the limitations associated with each method. These limitations encompass various aspects, including anatomical considerations, subject specificity, viscoelasticity, mechanical properties, model-specific factors, and limitations related to medical imaging. The guiding question for this review is: What are the existing limitations in the surveyed literature regarding ligament modeling and methods, specifically with regard to time variance and environmental hazards? A search of PubMed/MEDLINE, Web of Science (WoS), and ScienceDirect was conducted following the scoping review methodology recommended by the Joanna Briggs Institute (JBI) for evidence-based healthcare. After applying the inclusion and exclusion criteria, 74 full-text articles were analyzed, revealing that each method possesses its own set of limitations and may not comprehensively encompass all aspects of ligament properties. Nevertheless, despite these limitations, the majority of these methods exhibit the ability to produce reliable outcomes.
Article
Objective: To present and evaluate a method to objectively quantify the functional regions of joint lumped passive stiffness. Background: Joint passive stiffness has an important clinical role in constraining the degrees of freedom at a given joint. Links between passive stiffness and injury, pathology and function may be better understood if joint passive stiffness can be accurately quantified. Thus, a technique was developed to objectively partition passive stiffness curves into 3 linear regions (low, transition and high stiffness). Methods: The passive stiffness of the lumbar spine is presented as an example. Simulated data was used to determine the sensitivity of the method to Gaussian white noise in force measurements. An experimentally determined lumbar passive flexion curve was used to demonstrate the technique on human data. Breakpoint analysis was employed on the resulting moment-angle cures to partition the curve into low, transition and high stiffness zones. Results: The proposed method was successful at discriminating between the three stiffness zones and quantifying the passive stiffness within each zone. The algorithm had difficulty determining parameters in the low-stiffness zone in the presence of noise. Conclusions: The proposed method can be used as an objective method to investigate passive stiffness. Breakpoint Analysis can identify the three functional linear zones of passive stiffness. The slopes of these linear regions are then used as a measure of passive stiffness, which have applications in clinical populations and research studies, to assess time varying responses, or changes in stiffness following an intervention.
Article
The objective of this study was to build a scale of musculoskeletal discomfort for the upper body of footwear industry workers. The self-reported symptoms of 1821 workers were analyzed via exploratory factor analysis and item response theory. The anatomical regions located in the upper body showed ability to discriminate workers with different levels of musculoskeletal discomfort. A scale with six levels was built, ranging from minimal discomfort to maximum discomfort, with greater precision of discomfort scores between 0 and 3. The region of least discomfort on the scale only indicates rare symptoms in the left shoulder. In the region of maximum discomfort, workers experience symptoms in all regions analyzed on a daily basis, with emphasis on the elbows, neck, trapezius, and middle and upper back. The scale has satisfactory psychometric properties to assess musculoskeletal symptoms in footwear industry workers and can be useful in ergonomic studies.
Article
In the nineteenth century the Staffordshire pottery industry was in its heyday. Despite global interest in the Staffordshire potteries and associated collieries, very little research has explored the lives of children that worked in these industries. This research aims to redress the balance. Testimonies of workers, teachers, doctors and government officials, alongside clinical and census data will be used to gain an insight into juvenile well-being. This research has found that children worked in perilous environments which consequently affected their health and development. Furthermore, juveniles were at risk of physical abuse from their carers at home and in the workplace. Long working hours, poverty and domestic responsibilities prevented children from attending school and enjoying leisurely pursuits. However, the well-being of children gradually improved over the course of the century due to the implementation of new legislation.
Chapter
Tendons and ligaments are very similar collagenous connective tissues that are involved in musculoskeletal function. Both structures have similar hierarchical architecture and composition. Their composition generally consists of collagen, elastin, proteoglycans, water, and an abundant extracellular matrix. Despite the structural similarities, they have different functions. Tendons connect muscle to bone and translate the force produced from muscle contraction into joint translation. Ligaments connect bones to bones and provide joint stability and also work as a sensory organ. However, their responses to mechanical loading, injury or pathology are similar. Because of their critical role during locomotion, tendons and ligaments are vulnerable to injuries caused by overuse, trauma, or diseases. Tendon injuries may be categorized as chronic degenerative tendinopathies or acute ruptures. Ligament injuries classified into three degrees of sprain from mild fibril involvement to complete ruptures. Tendons and ligaments have adaptation ability to the changes in the mechanical environment relating to loading, injury or disease. During adaptation, the cells convert mechanical stimuli into biochemical responses which is called mechanotransduction. The entire body uses tensegrity architecture via mechanotransduction to stabilize the shape, structure, and function. Tendons and ligaments heal in the same manner following injury with three phases including inflammatory, proliferation, and remodeling. Although the healing occurs after an injury, the process may proceed slowly. The key concept for the healing is optimal loading via exercise-based rehabilitation which may maximize physiological adaptation while minimizing detrimental effects of immobilization, disuse or overload. The factors such as aging, gender, hormones, exercise, obesity, comorbidities, pharmacological agents and reconstruction or tissue engineering have impacts on tendon and ligament architecture and adaptation.
Article
Full-text available
Background: Low back pain (LBP) is a common condition with large burden worldwide. Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBP. No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain, despite this being a suggested risk factor for LBP. Aim: To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBP. Methods: This is a an observational before and after study of 26 participants (13 men, 13 women) between 20-35 years old. Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5. Pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back (Borg CR10 = 7/10). Wilcoxon signed-rank test was used for analyze values from the before and after test conditions. Mann-Whitney U test was used to investigate potential gender difference. Results: Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%. For all pain pressure threshold locations tested, there was a significant difference for the study population with moderate-large decreased (r = -0.56) pressure pain threshold after exposure to prolonged flexed sitting posture (P < 0.01). Comparisons between gender did not show any significant difference. Conclusion: The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBP and significantly reduced lumbar interspinous pressure pain thresholds. No gender-based differences were observed.
Chapter
High‐quality high‐volume spay–neuter (HQHVSN) and shelter surgery can be rewarding, but at times it can also be physically, emotionally, and mentally challenging. Health and wellbeing are important not only for surgeons’ quality of life, but also for their longevity in the field of HQHVSN, and the quality of patient care that they can provide. This chapter discusses general safety, physical ergonomics, and mental health, stress, and wellbeing, and provides information on how to minimize associated risks for surgeons and staff. There are numerous hazards associated with animal care and surgical workplaces, and excellent resources are available that describe these hazards and provide precautionary measures to minimize their harm. These hazards may be chemical (waste anesthetic gases, disinfectants), biologic (zoonoses, allergies), or physical (patient handling concerns, equipment malfunction, sharps injuries). Because of the ready availability of these resources, discussion of general safety in the chapter is limited to waste anesthetic gas exposure and animal handling safety.
Article
Full-text available
Objectives To establish quantitative values of stiffness for the gastrocnemius muscle in patients diagnosed with Achilles tendinopathy. Design Case–control study with a single (cross sectional) time point of patients diagnosed with unilateral Achilles tendinopathy and an asymptomatic group. Methods Sample of 50 participants: 25 participants with symptomatic unilateral Achilles tendinopathy (symptomatic group) with the asymptomatic side of this group used as a control (control group 1). A third group of 25 participants with asymptomatic Achilles tendons (control group 2). Mechanical stiffness parameters, including natural oscillation frequency (F), dynamic stiffness (S), mechanical stress relaxation time (R), logarithmic decrement (D) and creep (C), were assessed using the MyotonPRO. Measurements at the medial and lateral gastrocnemii were taken as non-weight bearing (NWB) and weight bearing (WB). Results Significant (p<0.05) differences were observed between the mean symptomatic group and control groups 1 and 2 in the WB and NWB conditions for natural oscillation frequency (F), dynamic stiffness (S), and creep (C). There was a significant reduction in S WB and conversely a significant increase in S of the symptomatic group NWB. Creep (C) and mechanical stress relaxation time (R) were significantly (p<0.05) less in the symptomatic group NWB. Significant differences were observed between the NWB and WB data sets for logarithmic decrement (D). NWB D demonstrated significantly (p<0.05) higher scores than the WB condition. Conclusion This study demonstrated that there was a significant reduction in stiffness of the gastrocnemius muscle in participants with Achilles tendinopathy compared with the two control groups. The WB MyotonPRO measures for the symptomatic groups of F and S were significantly lower, indicating a decrease in the tonal properties (F) and dynamic stiffness (S) of the muscle. The application of MyotonPRO technology to measure changes in stiffness in the gastrocnemius muscle may be useful to measure as part of a rehabilitation programme where specific attention could be placed to increase the tonal properties of the muscle. Further studies are required to develop a robust clinical application of this technology, particularly with regard to Achilles tendinopathy.
Article
Full-text available
Background: After acute injury, traumatized tissues respond following the healing process characterized by the inflammation response, fibroblastic repair response and remodeling response. This paper aims at analyzing the effect potential of the osteopathic manipulative treatment (OMT) which is capable of facilitating the healing process Method: A 28-­‐year-­‐old female volleyball player diagnosed with a grade III acute ankle sprain injury, a walking plaster cast for 20 days and no weight load on her foot, requested OMT. The osteopath scheduled and administered five OMT direct, indirect techniques sessions Results: The patient had her first differentiated training on the 27th day after the injury and her first official competition on the 51st day Conclusions: The outcomes of this single case are linked to the removal of the somatic dysfunctions which seem to promote the healing process responses therefore justifying future clinical studies dealing with the OMT mode of action Keywords: Osteopathic manipulative treatment; sports injury; somatic dysfunction; ankle sprain
Article
Full-text available
Background: Achilles Tendon (AT) midportion tendinopathy is a chronic condition which often health and well-being. Since it uses the Osteopathic Manipulative Treatment (OMT) as therapy, osteopathy is recommended as potentially beneficial in managing pain. The aim of this study was directed at observing the OMT effects on the variation in the intensity of pain and the AT functional disability observed pre-post OMT with the aid of the Sports Assestment-Achilles Questionnaire (VISA-A) Methods: The medical records (MR) of athletes, active during a time frame (January 2012-January 2013) who requested and received OMT sessions, were examined retrospectively. After selecting 20 potential recrutable MRs, (16,80%) were excluded, and (4,20%) which fulfilled the inclusion criteria, 1 female and 3 males, were recruited Results: At the primary end point 4 right AT and 1 left, after administration of 3 OMT sessions distributed in 1 month, showed: a variation in the average score of the intensity and of the functional disability of the VISA-A pre (50,5%) post (74%),a reduction in the duration of pain and stiffness when awakening equal to 32,5 minutes, an average drop in acute-strong pain of 41 points in the 4 cases Conclusions: The observation data of the 4 cases in relation to pain and functional disability of the AT midportion suggest that the OMT can be considered as a conservative approach that induce medical improvements, but further experimental studies need to be ensured to better investigate the OMT potential in active athletes (C. Civitillo Effects of Osteopathic
Conference Paper
Full-text available
Objetivou-se analisar a demanda, o controle e o suporte laboral na produção de calçados. Utilizou-se a versão portuguesa e resumida da Job Stress Scale. Participaram 179 trabalhadores de células de produção de calçados. Verificou-se que: (1) A demanda física relacionou-se à alta rapidez e intensidade pela qual as atividades devem ser desempenhadas; (2) A demanda psicológica, a pouca liberdade de iniciativas pelos trabalhadores; (3) O controle do trabalho, à reduzida autonomia para desempenhar diferentes atividades; e (4) O suporte laboral obteve avaliações positivas quando comparado às demais dimensões, interligando-se, a condições ambientais salubres e ao bom relacionamento interpessoal entre operários, líderes e supervisores bem como ao apoio, compreensão e afinidade entre os operários. Assim, as atividades analisadas depreendem uma importante demanda física e psicológica, sobretudo, pela repetitividade, segmentação do trabalho e pouca margem de manobra. Porém, estes fatores parecem não afetar o suporte laboral.
Conference Paper
Objetivou-se analisar a demanda, o controle e o suporte laboral na produção de calçados. Utilizou-se a versão portuguesa e resumida da Job Stress Scale. Participaram 179 trabalhadores de células de produção de calçados. Verificou-se que: (1) A demanda física relacionou-se à alta rapidez e intensidade pela qual as atividades devem ser desempenhadas; (2) A demanda psicológica, a pouca liberdade de iniciativas pelos trabalhadores; (3) O controle do trabalho, à reduzida autonomia para desempenhar diferentes atividades; e (4) O suporte laboral obteve avaliações positivas quando comparado às demais dimensões, interligando-se, a condições ambientais salubres e ao bom relacionamento interpessoal entre operários, líderes e supervisores bem como ao apoio, compreensão e afinidade entre os operários. Assim, as atividades analisadas depreendem uma importante demanda física e psicológica, sobretudo, pela repetitividade, segmentação do trabalho e pouca margem de manobra. Porém, estes fatores parecem não afetar o suporte laboral.
Article
Elbow pain syndromes are common upper extremity musculoskeletal disorders, and they are usually associated with repetitive occupational exposure. Ligaments are often one of the sources of musculoskeletal disorders because of their mechanical and neurological properties. The wrist ligaments are some of the ligaments most vulnerable to occupational exposure. Since most occupational tasks require wrist extension for handling tools and loading, the scapholunate interosseous ligament (SLIL) bears greater strain during loading, which results in creep deformation and hysteresis. Ligamentous creep may result in diminished ability to detect signal changes during joint movements, which impairs neuromuscular control established by ligamentomuscular reflex arcs elicited from mechanoreceptors in the ligaments. Changes in muscle activation patterns of forearm muscles due to diminished ligamentomuscular reflexes may initiate a positive feedback loop, leading to musculoskeletal pain syndromes. The relationship between elbow pain syndromes and SLIL injury will be presented through two hypotheses and relevant pain mechanisms: 1. Repetitive tasks may cause creep deformation of the SLIL, which then impairs ligamentomuscular reflexes, leading to elbow pain disorders. 2. Lateral epicondylalgia may increase the risk of SLIL injury through the compensation of the lower extensor carpi radialis muscle activity by higher extensor carpi ulnaris muscle activity, which may alter carpal kinematics, leading to SLIL degeneration over time. The differential diagnosis is usually complicated in musculoskeletal pain disorders. The failure of treatment methods is one of the issues of concern for many researchers. A key element in developing treatment strategies is to understand the source of the disorder and the nature of the injury. We proposed that the differential diagnosis include SLIL injuries when describing elbow pain syndromes, particularly, lateral epicondylalgia.
Article
Full-text available
Occupational kneeling is associated with an increased risk for tibiofemoral knee osteoarthritis. Forces on the knee in the kneeling posture, as well as the greater incidence of meniscus tears among workers likely contribute to the increased risk. We hypothesize that an additional mechanism may contribute – altered neuromuscular control due to prolonged high knee flexion. Forty participants (20 male, 20 female) completed an evaluation of gait and squatting before, immediately following, and 30 minutes following a 30-minute simulated occupational kneeling exposure. An increase in the peak external knee adduction moment and a delay in vastus medialis activation onset during walking was observed post-kneeling, as well as increased frontal plane knee motion during squatting. This was the first investigation to find changes in high flexion transitions as a result of kneeling. Greater frontal plane knee motion may increase the risk for meniscal tears, and subsequently, knee osteoarthritis. Practitioner Summary A 30-minute simulated occupational kneeling exposure resulted in small but significant gait changes. The greatest effect was on frontal plane knee movement during squatting, which is especially relevant to occupations requiring frequent kneeling/squatting. This increased motion may indicate an increased risk of injury, which supports a link to knee osteoarthritis. This article is available to access at the University of Waterloo's Institutional Repository, UWspace https://uwspace.uwaterloo.ca/handle/10012/12972
Article
Full-text available
Ligaments adapt according to the intensity of physical activity and mechanical load to which they are subjected. In the last decade there have been methods and protocols in the field of infant neurofunctional physiotherapy, which have the term "suit" in common, to characterize the existence of suits with adjustable elastic bands and the possibility of applying load on the human skeleton. Since the mechanical load can produce fibrocartilaginous changes on the ligaments and also that no studies evaluating the effect of suit therapy on ligaments of the spine were found, research with experimental methods of load are justified. The aim of this study was to analyze thickness and morphology of longitudinal ligaments of the spine of Wistar rats when subjected to mechanical load by vertebral compression. Thirty animals were separated into five groups (G1 - control; G2 - simulation of the use of suit; G3, G4, and G5 - maintenance of the suit). The suit experimental model, in G4 and G5, were adapted weights or elastic bands arranged in "X" for 50% of spinal overload of the weight of the animal, who remained with the suit for 40 hours over four weeks of experiment, five days a week. There were no significant differences for thickness, and morphological changes of longitudinal ligaments were also not observed. We concluded that there were no changes in longitudinal ligaments of the spine in animals subjected to the experimental model of suit therapy.
Article
Biologic tissues respond to the biomechanical conditions to which they are exposed by modifying their architecture. Experimental evidence from the literature suggests that the aim of this process is the mechanical optimization of the tissues (functional adaptation). In particular, this process must produce articular surfaces that, in physiological working conditions, optimize the contact load distribution or, equivalently, maximize the joint congruence. It is thus possible to identify the space of adapted joint configurations (or adapted space of motion) starting solely from knowledge of the shape of the articular surfaces, by determining the envelope of the maximum congruence configurations. The aim of this work was to validate this hypothesis by testing its application on 10 human ankle joints. Digitalizations of articular surfaces were acquired in 10 in-vitro experimental sessions, together with the natural passive tibio-talar motion, which may be considered as representative of the adapted space of motion. This latter was predicted numerically by optimizing the joint congruence. The highest mean absolute errors between each component of predicted and experimental motion were 2.07° and 2.29mm respectively for the three rotations and translations. The present kinematic model replicated the experimentally observed motion well, providing a reliable subject-specific representation of the joint motion starting solely from articulating surface shapes. Copyright © 2015 Elsevier Ltd. All rights reserved.
Article
We examined magnitude preference, subjective discomfort, and spine posture during prolonged simulated driving with a self-selected amount of lumbar support. The general use of lumbar supports has been associated with decreased reports of low-back pain during driving exposures; however, minimal data exist regarding occupant magnitude preference. Participants chose between five discrete levels of lumbar support (0-4 cm). Time-varying postural and discomfort responses were then monitored throughout 2 hr of simulated driving. There were no significant effects of gender or time on posture. Women preferred larger amounts of support than men (3.25 cm ± 0.71 and 2.56 cm ± 0.88, respectively, p = .048). All participants exhibited significant increases (p = .003) in pelvic discomfort throughout the 2-hr trial regardless of the level of support chosen. Discomfort related to various aspects of the lumbar support increased significantly over time. Retrospectively, no participants desired a setting beyond 4 cm, and the majority of respondents indicate had they been able to change their initial selection, they would choose a setting between 2 and 3 cm. The results suggest that occupants would prefer increasing the excursion capability of automobile lumbar supports beyond 2 cm. Excursion capability and adjustability of automobile lumbar supports are important features to better meet end-user preference and to reducing lumbar flexion in sitting. © 2015, Human Factors and Ergonomics Society.
Article
This paper offers an extensive review of the main fascia-mediated mechanisms underlying various dysfunctional and pathophysiological processes of clinical relevance for manual therapy. The concept of somatic dysfunction is revisited in light of the diverse fascial influences that may come into play in its genesis and maintenance. A change in perspective is thus proposed: from a nociceptive model that for decades has viewed somatic dysfunction as a neurologically-mediated phenomenon, to a unifying fascial model that integrates neural influences into a multifactorial and multidimensional interpretation of dysfunctional process as being partially, if not entirely, mediated by the fascia. Copyright © 2015 Elsevier Ltd. All rights reserved.
Article
Full-text available
Data from in vivo magnetic resonance (MR) imaging of the human anterior cruciate ligament (ACL) was used to generate three-dimensional computer models for structural analysis. Step one of the solid modelling method involves the identification of the femoral and tibial attachment sites from MR images. Step two involves profiling the skeletal framework of the anteromedial (AM) and posterolateral (PL) bundles. Step three executes the generation of twenty (trial) solid models, for different anatomical attachments, from the skeletal framework. Thereafter, these models were assessed for the ones which best fit the ACL in the MR image. Using finite element (FE) method, the final model was solved for the stress uptake under pre-stress conditions. All models reveal a characteristic anatomical twist—this has only been observed in the knee undergoing surgical operation. FE analysis reveals that high stresses occur at the femoral attachment sites. In particular, in the sagittal view, stresses in the posterior part of the ACL are larger than that in the anterior part. The modelling approach provides a simple analysis of the structure-function properties of ACL, with important implications for model development for studying the response of the anatomical twist to physiological loads, with applications in diseases and ageing.
Article
Full-text available
Study Design. A 3-year prospective cohort study among workers of 34 companies in the Netherlands. Objectives. To investigate the relation between flexion and rotation of the trunk and lifting at work and the occurrence of low back pain. Summary of Background Data. Previous studies on work-related physical risk factors for low back pain either lacked quantification of the physical load or did not take confounding by individual and psychosocial factors into account. Methods. The study population consisted of 861 workers with no low back pain at baseline and complete data on the occurrence of low back pain during the 3-year follow-up period. Physical load at work was assessed by means of analyses of video-recordings. Information on other risk factors and the occurrence of low back pain was obtained by means of self-administered questionnaires. Results. An increased risk of low back pain was observed for workers who worked with the trunk in a minimum of 60° of flexion for more than 5% of the working time (RR 1.5, 95% CI 1.0–2.1), for workers who worked with the trunk in a minimum of 30° of rotation for more than 10% of the working time (RR 1.3, 95% CI 0.9–1.9), and for workers who lifted a load of at least 25 kg more than 15 times per working day (RR 1.6, 95% CI 1.1–2.3). Conclusions. Flexion and rotation of the trunk and lifting at work are moderate risk factors for low back pain, especially at greater levels of exposure.
Article
Full-text available
A total of 574 active workers from six different industrial sites were categorised into four force repetitive exposure groups. Workers in low force-low repetitive jobs served as an internal comparison population for the three other groups. Videotapes and surface electromyography were used to estimate hand force and repetitiveness. The presence of cumulative trauma disorders (CTD) was determined by structured interview and standardised non-invasive physical examination. Only workers who had been working on the study jobs for at least one year at the time of evaluation were eligible for selection. Categorisation of jobs and identification of CTDs were carried out independently by investigators who were appropriately blinded to exposure and outcome. The analysis of associations between CTDs and exposure categories were performed using Mantel-Haenszel plant adjusted odds ratios and unconditional multiple logistic regression. Significant positive associations were observed between hand wrist CTDs and high force-high repetitive jobs. These associations were independent of age, sex, years on the specific job, and plant.
Article
The present study was aimed at investigating whether reflex actions onto fusimotor neurones, caused by increased tension in the posterior cruciate ligament (PCL) of the knee joint, are potent enough to influence the information transmitted by the primary muscle spindle afferents. The experiments were made on 10 α-chloralose anaesthetized cats. Recordings were made simultaneously from 2-4 muscle spindle afferents from the posterior biceps and semitendinosus muscles (PBSt) and/or the triceps-plantaris muscles (GS). The modulation and mean rate of firing of the afferent response to sinusoidal stretching of the PBSt and GS muscles were determined. Control measurements were performed in the absence of any joint stimulation. Test measurements were made during stretching of the PCL with low traction forces (5-40 N). Out of the total sample of 46 primary muscle spindle afferents (29 from GS and 17 from PBSt), 25 (i.e. 54%, 17 from GS and 8 from PBSt) exhibited clear-cut changes in the sinusoidal response. Small but significant effects were also recorded from 2 secondary spindle afferents. The low standard traction forces applied to the PCL, and the fact that it on occasions was possible to settle threshold loads to 5-10 N, indicate that the fusimotor effects observed were caused by mechanoreceptors, most likely Ruffini and/or perhaps Golgi tendon organ-like endings. While the GS primary muscle spindle afferents showed predominantly dynamic reflexes as well as mixed or predominantly static effects, the PBSt afferents exhibited solely mixed or static effects. As no changes in the force development accompanied the effects, it is likely that stretch/tension sensitive receptor afferents from the posterior cruciate ligament acted on γ-rather than on β-fusimotor neurones. The results indicate that the PCL may play a very important 'sensory role' and it is concluded that receptors in the PCL may contribute, via reflex actions on the γ-motor-muscle spindle system, to the regulation of muscular stiffness around the knee joint and thereby also to the control of joint stiffness and joint stability. The mechanisms by which the PCL, via the adjustment of muscle stiffness, may control joint stability are discussed.
Article
The author reviews some of the general principles of articular neurology as they are presently understood, with particular reference to those that are likely to bear on the clinical interests of rheumatologists.
Article
The purpose of this work was to demonstrate whether neural elements are present in the spinal ligaments removed from patients with disc herniation. The tissue samples were stained by an immunohistochemical technique using antibodies to neurofilament protein (NFP) subunits as specific markers. Numerous NFP-immunoreactive nerve fibers and free nerve endings were demonstrated within the ligamentous structures. These findings were discussed relative to the low-back pain of disc herniated patients.
Article
Study Design. Electromyographic responses from the lumbar multifidus muscle of the cat were recorded in vivo during 50 minutes of cyclic loading followed by 2 hours of rest. Objective. To determine the rate of recovery of reflexive muscular stabilizing activity resulting from rest after viscoelastic laxity induced by 50 minutes of cyclic loading. Summary of Background Data. Muscular forces from agonists and antagonists were repeatedly shown to be the most significant stabilizing structures of the lumbar spine. Reflexive muscular coactivation force from the multifidus muscle elicited by mechanoreceptors in the spinal viscoelastic structures were, however, shown to diminish drastically with the onset of laxity in the viscoelastic structures. Data describing the rate of recovery of reflexive muscular coactivation forces resulting from rest after cyclic loading were not found. Methods. Cyclic loading of the lumbar spine at 0.25 Hz was applied to L4–L5 for 50 minutes while electromyograms from the multifidus muscles of L1–L2 to L6–L7 were recorded. A rest period of up to 2 hours was given, during which electromyographic responses and load were measured every 10 minutes to sample recovery of laxity and reflexive muscular activity. Results. Load and electromyographic response demonstrated an exponential decrease during the 50 minutes of cyclic loading. The first 10 minutes of rest allowed a significant recovery in laxity and muscle activity, with additional slow recovery over the next 20 to 30 minutes. The electromyographic response and load were increasing at an extremely slow rate thereafter. Overall, 2 hours of rest yielded only a 20% to 30% recovery in electromyographic response. Full recovery was never observed. A biexponential model was developed to predict loss and recovery of reflexive muscular activity and viscoelastic tension with laxity. Conclusions. Laxity in the viscoelastic structures of the lumbar spine desensitizes the mechanoreceptors within and causes loss of reflexive stabilizing forces from the multifidus muscles. The first 10 minutes of rest after cyclic loading results in fast partial recovery of muscular activity. However, full recovery is not possible even with rest periods twice as long as the loading period, placing the spine at an increased risk of instability, injury, and pain.
Article
The time course of full lumbar flexion under a prolonged flexion moment, lasting 20 min, was documented in 27 male and 20 female subjects. Peak flexion increased by 5.5° over the 20 min. The flexion-creep data was fitted with a first-order step input response having a time constant of 9.4 min. Maximum flexion was also documented over the recovery phase, lasting 30 min, indicating that subjects regained approximately 50% of their resting joint stiffness within 2 min of resuming relaxed lordosis, although full recovery took longer than the flexion-creep, indicating the presence of viscoelastic hysteresis. For this reason it may be prudent to advise those who experience prolonged full flexion postures (as might a seated warehouse shipper/receiver, gardener, or construction worker) to stand and walk for a few minutes prior to performing demanding manual exertions. Indeed, temporary joint flexion laxity, following a bout of full flexion, may increase the risk of hyperflexion injury to certain tissues.
Article
The correlation of the mechanical properties and the morphological behaviour of collagenous tissue during strain was investigated. Relaxed and strained tendons were examined by incidental and transmitted polarized light microscopy and electron microscopy. It was concluded that the wavy pattern seen at the seminicroscopic level of the collagen fibers vanished at relatively low loads. The direction of birefringence in transmitted light microscopy varied in the relaxed preparations but became even in the strained. The electron microscopy showed that the fibrils had the same periodicity as calculated from X-ray diffraction patterns of moist collagen, i.e. 680 , and that straining increased the period lengths of some fibrils. The correlation of these findings to a mechanical analogy of the tissue was discussed.
Article
Epidemiological data suggest that high loads lifted by workers engaged in static and cyclic daily activities may be a risk factor for low back disorder. Our previous research provided physiological and biomechanical validation of the epidemiological data for static load conditions. The objective of this report was to provide physiological and biomechanical experimental validation to the epidemiological data in cyclic (repetitive) load conditions. Three groups of in vivo feline models were subjected to 3 cyclic load levels in a series of 6 periods of 10 minutes of work spaced by 10 minutes of rest followed by 7 hours of rest. Multifidus electromyography (EMG) and lumbar displacement were statistically analyzed after processing. Delayed muscular hyperexcitability was observed only in moderate (40 N) and high (60 N) loads (P<0.0001) but was absent in low (20 N) loads. The magnitude of the delayed hyperexcitability was found to be higher (P<0.0001) in the high (60 N) loads compared with the moderate (40 N) loads. Exposure to moderate and high loads in cyclic (repetitive) work results in an acute neuromuscular disorder indicative of soft tissue inflammation that may become chronic with further exposure.
Article
A computerized radiographic technique was used to determine the effect of hamstring antagonist co-contraction on the stability of the joint during isometric knee extension. Data collected from 12 cadaver knees showed that significant anterior displacement and internal rotation of the tibia occurred during isolated quadriceps loading, whereas significant reduction in anterior displacement and rotation occurred upon simultaneous low-level loading of the hamstrings in the range of motion of 15°-80° flexion. Hamstrings co-contraction was ineffective in the range of 0°-15° of flexion. Larger hamstrings loads resulted in more pronounced reduction in the anterior displacement and rotation of the tibia. We concluded that hamstring co-contraction has significant effect on maintaining knee stability, providing synergistic action to the anterior cruciate ligament (ACL) by preventing excessive anterior displacement and internal rotation of the tibia. We also concluded that hamstring strength training is essential therapy in conservative treatment of ACL-deficient knees, as an adjunct therapy to ligament repair procedures and as preventive therapy in high-performance athletes subject to potential risk of ligamentous injuries.
Article
Joint position sense has been suggested to be an important factor in the etiology of degenerative joint disease. It is also believed to be important in the rehabilitative process after reconstructive surgery of the knee. Despite this awareness, in many areas of orthopaedic surgery little effort has been devoted to study of this crucial topic. Therefore, we conducted several studies of knee joint position sense by measuring the ability of healthy subjects to reproduce an angle and detect the threshold of motion. Our goal was to evaluate the effects of the following factors: aging; degenerative joint disease; total knee replacement, i.e., both absence of the anterior cruciate ligament (ACL) and sensory loss due to the absence of capsular structures; fatigue; athletic training; disruption and reconstruction of the ACL; and the role of ligament mechanoreceptors. Our results show that normal individuals can actively reproduce an angle with their knee to an average error of 2.5°. Furthermore, normal subjects require passive movement of ∼2.5°-4° to detect a change in position at the speeds used in this study (∼0.5°/s). Muscular training improves the ability to detect motion. On the other hand, muscular training and fatigue appear to decrease the ability to reproduce an angle. Changes in the knee and its associated structures caused by damage (ACL disruption, arthritis, total knee replacement) as well as aging uniformly cause deterioration of joint position sense. Total knee replacement and arthritic change cause the greatest deterioration. Reconstruction of ligamentous structures and/or rehabilitation appears to restore joint position sense to a near normal level.
Article
Four types of receptors have been described in the articular tissues of the knee joint in humans and animals. The first three types are encapsulated; the fourth is unencapsulated: type I, Ruffini endings; type II, Pacinian corpuscles; type III, Golgi tendon organs; and type IV, free nerve endings. Ruffini endings, Pacinian corpuscles, and free nerve endings are most prevalent in the fibrous joint capsule; Golgi tendon organs are most common in the collateral and cruciate ligaments and the menisci. In the anterior and posterior cruciate ligaments (ACL, PCL), receptors are concentrated at the tibial and femoral attachments of the ligaments. In the menisci, neural elements penetrate the horns and the outer and middle thirds of the body. Ruffini mechanoreceptors are believed to contribute mainly to maintenance of muscle tone, Pacinian corpuscles and Golgi tendon organs are stimulated during movement, and free nerve endings are nociceptors. Thus, receptors of the knee joint are able to produce a discriminating afferent inflow to the central nervous system (CNS), thereby contributing to the protection and function of the joint through the musculature.
Article
Thesis (Ph. D.)--University of California, San Diego, Department of Applied Mechanics/Engineering Sciences, 1988. Includes bibliographical references (leaves 152-157). Photocopy.
Article
Article
Twenty-eight male and twenty-one female subjects with no history of previous injury to their knees were examined using a newly developed clinical testing apparatus designed to record anterior-posterior tibial force versus displacement and varus-valgus moment versus angulation during manual manipulation of the knee. Joint stiffness and laxity were measured from test tracings made with the knee muscles relaxed and tensed. Agreement between these measurements and those made previously on thirty-five fresh cadaver knee specimens was very good. Anterior-posterior laxity averaged 3.7 millimeters in full extension, 5.5 in 20 degrees of flexion, and 4.8 millimeters in 90 degrees of flexion, while the mean varus-valgus laxity was 6.7 degrees in full extension. The common clinical assumption that normal right-left differences are negligible was found to be invalid. Individual right-left differences averaged 26 to 35 per cent for laxity and 19 to 24 per cent for stiffness. There was no discernible tendency for one knee to be more stable than the other; random interchanges of relative stability between the right and left knees were observed for each individual at different knee positions. When requested to tense the knee muscles, these subjects were able to increase their knee stiffness an average of two to four times while knee laxity was reduced to 25 to 50 per cent of the normal value.
Article
Thirty-five normal cadaver knees were tested manually in six positions of the knee using apparatus designed to measure the moment-rotation responses for both varus-valgus angulation and torsion of the tibia, as well as the force-displacement responses for anterior-posterior movement of the tibia. The responses of all knees to all modes of loading were non-linear, reflecting increasing stiffness. With the knee at full extension, stiffness was maximum and laxity was minimum. Hence, it was in this position that changes in stability (laxity and stiffness) were best demonstrated when ligament structures were sectioned. Differences in laxity were observed between right and left knees of intact paired specimens. Torsional laxity and internal rotation stiffness were most affected by sectioning the medial collateral ligament, while external rotation stiffness was only affected by division of both the lateral collateral ligament and the posterior capsule. Varus-valgus laxity was relatively unaffected by removal of the menisci or section of the cruciate ligaments but increased greatly when either collateral ligament was cut. The medial collateral ligament was the main contributor to valgus stiffness, whereas the lateral collateral ligament had no measurable effect on varus stiffness. Anterior-posterior stability was affected to some extent by virtually every sectioning procedure. Isolated section of the anterior cruciate ligament produced the greatest increase in anterior-posterior laxity at full extension and section of the posterior cruciate, the greatest increase at 90 degrees of flexion. Large increases in anterior-posterior laxity were also observed when the medial collateral ligament and posterior capsule were sectioned in combination.
Article
The anterior-posterior displacement and rotation of the tibia elicited by isolated loading of the quadriceps muscle was determined as a function of joint angle and muscle load using a computerized radiographic technique. Data collected from 12 fresh-frozen cadaveric knees demonstrated that quadriceps contraction can result in significant (less than 7 mm) anterior displacement of the tibia in the range of 0 degrees to 80 degrees of flexion, and a mild (less than 2 mm) posterior displacement in the range of 80 degrees to 120 degrees of flexion. Peak anterior displacement of 6.3 mm was observed at 30 degrees of flexion under a 12 kg load in the quadriceps, while a constant 1.5 mm posterior displacement was observed throughout flexion angles exceeding 80 degrees. It was further shown that the magnitude of the anterior displacement increased nonlinearly as the quadriceps force increased. Loading of the quadriceps also resulted in internal rotation of the tibia in the range of 0 degrees to 90 degrees of flexion, and in external rotation of the tibia in the range of 90 degrees to 120 degrees. Peak internal rotation of 7 degrees was observed at 15 degrees of flexion and a peak external rotation of 1 degrees was detected at 120 degrees of flexion. Larger quadriceps load resulted in larger rotation. We concluded that quadriceps contraction during knee extension has direct impact on anterior displacement and rotation of the tibia and therefore on anterior cruciate ligament stress, increasing it as the muscle's force is increased during knee extension.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
The purpose of this work was to demonstrate whether neural elements are present in the spinal ligaments removed from patients with disc herniation. The tissue samples were stained by an immunohistochemical technique using antibodies to neurofilament protein (NFP) subunits as specific markers. Numerous NFP-immunoreactive nerve fibers and free nerve endings were demonstrated within the ligamentous structures. These findings were discussed relative to the low-back pain of disc herniated patients.
Article
Morphologic, physiologic, and clinical evidence for the sensory role of the cruciate ligaments is reviewed. The cruciate ligaments accommodate morphologically different sensory nerve endings (Ruffini endings, Pacinian corpuscles, Golgi tendon organlike endings, and free nerve endings) with different capabilities of providing the central nervous system with information not only about noxious and chemical events but also about characteristics of movements and position-related stretches of these ligaments. A survey of available data reveals that low threshold joint-ligament receptor (i.e., mechanoreceptor) afferents evoke only weak and rare effects in skeletomotor neurons (alpha-motor neurons), while they frequently and powerfully influence fusimotor neurons (gamma-motor neurons). The effects on the gamma-muscle-spindle system in the muscles around the knee are so potent that even stretches of the cruciate ligaments at relatively moderate loads (not noxious) may induce major changes in responses of the muscle spindle afferents. As the activity in the primary muscle spindle afferents modifies the stiffness in the muscles, the cruciate ligament receptors, via the gamma-muscle-spindle system, may participate in the regulation and preprogramming of the muscular stiffness around the knee joint and thereby of the knee joint stiffness. Thus, the sensory system of the cruciate ligaments is able to significantly contribute to the functional stability of the knee joint.
Article
This is a brief review of the role of joint receptors in kinaesthesia, the sense of position and movement of the limbs. It is proposed that joint receptors are concerned with signalling joint movement but not . joint position, at least over most of a joint's working range. This view is supported by recent psychophysical experiments which also suggest that the sense of position derives from activity in muscles acting about a joint. There is continuing controversy over interpretation of animal experiments and whether joint receptors are able to signal joint position. One source of confusion has been the fact that some joint nerves contain afferent fibres arising from nearby muscles. It is concluded that on present evidence joint receptors are unlikely to play a major role in the sense of position, although they have important functions, signalling joint movement, acting as joint limit detectors and as nociceptors.
Article
The relationships between the mean rectified EMG from two muscle groups crossing the knee joint and the rotational stiffness and laxity about the longitudinal axis of the lower leg were investigated. The EMG signals from three of the quadricep muscle group and two of the hamstring muscle group were monitored using surface electrodes. Each subject sustained self-induced muscle activity from specific muscle combinations while the foot was twisted internally and externally by the researcher. Joint rotation was measured using an electrogoniometer. Analyses of the data showed increased joint stiffness with increased numbers of active muscles. The stiffness measurements ranged from 0.16 to 2.54 Nm degree-1 depending upon the combination of active muscles. The stiffness measured in different tests were very repeatable with standard deviations ranging from 0.02 to 0.25 Nm degree-1. Increases in joint stiffness of over 400% by activation of these muscles were measured.
Article
The synergistic action of the ACL and the thigh muscles in maintaining joint stability was studied experimentally. The EMG from the quadriceps and hamstring muscle groups was recorded and analyzed in three separate experimental procedures in which the knee was stressed. The test revealed that direct stress of the ACL has a moderate inhibitory effect on the quadriceps, but simultaneously it directly excites the hamstrings. Similar responses were also obtained in patients with ACL damage during loaded knee extension with tibia subluxation, indicating that an alternative reflex arc unrelated to ACL receptors was available to maintain joint integrity. The antagonist muscles (hamstrings) were clearly demonstrated to assume the role of joint stabilizers in the patient who has a deficient ACL. The importance of an appropriate muscle-conditioning rehabilitation program in such a patient is substantiated.
Article
The effects of immobilization and remobilization on the biomechanical and morphological properties of the femur-medial collateral ligament-tibia complex and each of its components were investigated in the rabbit. Specimens that had been obtained after periods of unilateral immobilization of the knee and remobilization were evaluated for structural properties. In addition, the mechanical properties of the substance of the medial collateral ligament and the histological characteristics of both the substance of the ligament and its sites of insertion were evaluated. After immobilization, there were significant reductions in the ultimate load and energy-absorbing capabilities of the bone-ligament complex, and an increased number of failures occurred by tibial avulsion. The tissue of the medial collateral ligament also became less stiff as a result of immobilization. Histologically, the femoral and tibial insertion sites showed increased osteoclastic activity, resorption of bone, and disruption of the normal attachment of the bone to the ligament. With remobilization, the ultimate load and energy-absorbing capabilities of the bone-ligament complex improved but did not return to normal. Failure by tibial avulsion became less frequent, and the stress-strain characteristics of the medial collateral ligament returned to normal. Histologically, the sites of insertion of the ligament also showed evidence of recovery.
Article
Responses of spinal cord neurones to excitatory input from myelinated and non-myelinated afferent fibres of the knee joint were investigated in spinalized cats that were anaesthetized with alpha-chloralose. The hind limb was largely denervated except for the knee joint. The action of joint afferent volleys on populations of spinal cord neurones was assessed by recordings of cord dorsum potentials and of field potentials within the substance of the spinal cord. Three different negative cord dorsum potentials (NI, NII and NIII waves) were produced by volleys in progressively smaller sized myelinated afferent fibres of the posterior articular nerve of the knee. Volleys in non-myelinated joint afferent fibres did not evoke a detectable cord dorsum potential. The NII and NIII waves could be recorded at segmental levels L4-S2. Field potentials corresponding to the cord dorsum negative waves were recorded with a tungsten micro-electrode inserted into the substance of the cord. The potentials were negative when the recording electrode was in the dorsal horn, but reversed to become positive in the ventral horn. There were differences in the depths at which the different components of the field potential sequence reversed in sign. Single unit recordings revealed that afferent volleys in the posterior articular nerve could excite neurones in segments L5-S1 and at depths from less than 1 to 4 mm below the dorsal surface of the cord. Most marked recording sites were in laminae I, IV-VI or VIII. Many units were activated just by the A fibre component of the joint afferent volley, but others could also be excited by the C fibre component. None were excited just by C fibres. All units tested had a convergent excitatory input from fibres belonging to cutaneous, muscle and mixed nerves. Neurones excited by joint afferent volleys were tested for a receptive field using several forms of local mechanical stimulation of the knee joint and joint movements. Most cells could be activated by one or more of these stimuli. Although many of the effective mechanical stimuli were innocuous, noxious stimuli could often excite the cells more effectively, and some neurones were only activated by noxious stimuli. A few cells with receptive fields in the knee joint did not respond to joint movements.
Article
The objectives of this study were to measure strain in the ACL during simulated: hamstring activity alone, quadriceps activity alone, and simultaneous quadriceps and hamstring activity. Seven knee specimens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric contractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0 degree to 45 degrees, the quadriceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30 degrees of flexion. The hamstrings are not capable of masking the potentially harmful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30 degrees.
Article
Rat medial collateral ligaments from one group of animals were tensile tested following immobilization. Ligaments from a second group of animals were examined using transmission electron microscopy to determine collagen fibril cross-sectional area and density. Immobilized and contralateral control ligaments were compared to determine the effect of immobilization on these parameters. There was a significant decrease in the linear stress, maximum stress, and stiffness of immobilized ligaments. There was no significant difference in the strain values reported. There was a significant decrease in the proportion of smaller, cross-sectional area fibrils (0-10,000 nm2) following immobilization. There was also a significant increase in the proportion of larger (30,000-40,000 nm2 and 40,000-50,000 nm2) fibrils following immobilization. This finding was attributed to a decreased synthesis and decreased degradation of collagen during immobilization; post-immobilization, the density of collagen fibrils in the ligament decreased. There may be a relationship between ultrastructural and mechanical alterations following immobilization. Significant clinical implications are apparent in the altered mechanical properties following immobilization.
Article
There is still a long way to go to achieve the goals of ligament replacement through modification of normal, intrinsic ligament healing processes. We are learning about the biology of ligamentous tissues, including the problem of regeneration, and that in itself is an all-important first step toward seeking solutions.
Article
Tension-induced molecular rearrangements in wet native fibres of rat-tail tendons and human finger flexor tendons are registered with the help of time-resolved diffraction spectra using synchrotron radiation. The tension-induced increase of the 67 nm D period is combined with changes in the intensities of some orders of the meridional small angle reflection. Both effects are reversible when unloading the fibre, but are preserved when the load is held constant until the fibre tears. The increase in the D period is partly due to a sliding of the triple helices relative to each other and partly due to a stretching of the triple helices themselves. The sliding of the triple helices results in an alteration of the D stagger, leading to a change in the length of the gap and overlap regions, and to a stretching of the cross-linked telopeptides. This interpretation is supported by comparison with the relative intensities derived from a model with varying length of gap and overlap regions, as well as by comparison with model calculations that include the telopeptides.
Article
The ultrastructure of sensory nerve endings in the human knee joint capsule was studied. Three types of nerve endings were found: free nerve endings (FNE), Ruffini corpuscles and Pacini corpuscles. In the joint capsule, FNE are located below the synovial layer and within the fibrous layer near blood vessels. These nerve terminals derive from myelinated Aδ-fibres or from unmyelinated C-fibres. Their structure is almost identical to FNE in human hairy and non-hairy skin. Ruffini corpuscles are present within the fibrous layer and the ligaments of the capsule in three variations: small Ruffini corpuscles without a capsule, small with a connective tissue capsule, and large Ruffini corpuscles with an incomplete perineural capsule. Their afferent axons are myelinated and measure 3–5 μm in diameter. Inside the corpuscle, nerve terminals are anchored in the connective tissue belonging to the fibrous layer or to the ligaments respectively. The presence of an incomplete perineural capsule depends on the structure of the surrounding connective tissue. In ligaments with collagenous fibrils oriented in a parallel fashion, the perineural capsule is well-developed and the Ruffini corpuscle resembles a Golgi tendon organ; in areas where the fibrils show no predominant orientation, Ruffini corpuscles lack a capsule. Small Pacini corpuscles are situated within the fibrous layer near the capsular insertion at the meniscus articularis or at the periost. They consist of one or several inner cores and a perineural capsule of 1–2 layers. Larger Pacini corpuscles with one or several inner cores and a perineural capsule consisting of 20–30 layers are found on the outer surface of the fibrous layer. The ultrastructure of these nerve endings is compared with the ultrastructure of articular receptors of various animals and with the ultrastructure of sensory nerve endings in the skin of several mammalian species including man.
Article
An apparatus that enables simultaneous stress-strain recording and morphological observation in incidental light microscopy of a specimen surface during tensile loading is described. Results from experiments on parallel-fibred collagenous specimens (tendons) are reported and variations between behavior during the first tensile loading cycle and those in the steady-state cycles (when the plasticity and irreversible viscosity are exhausted) are described. It is found that the “toe” part of the stress-strain curve is longer from a morphological point of view than can be mechanically measured, which means that the waviness of the collagenous bundles is diminished before any measurable load is applied. The steady state means an even longer such “toe” part and a better parallel arrangement of the fibers but the waviness in the relaxed specimen cannot be disturbed by repeated loadings. The functional range of a tendon is also discussed as are the phenomenon of spraining and the possibility of pre-stress.
Article
The distal tendons of the tibialis posterior, percnei longus, traius and quartus muscles from fifteen rabbits trained in a running machine were investigated regarding tensile strength properties and compared with the tendons of thirteen control rabbits of the same stock. The maximum and the linear load values were found to be higher in the trained animals. The contents of the peroneu, brevis tendons of these animals were investigated for the weight, water and collagen content and no differences were found. It was concluded that these differences must be accounted for by qualitative and not quantitative changes in the collagenous tissue as a response to the training.
Article
1. The conduction velocities of 278 posterior articular nerve fibres studied in dorsal root filaments ranged from 10 to 110 m/sec. The conduction velocities were distributed similarly to posterior articular nerve fibre diameters determined histologically. 2. Two hundred and nine fibres were slowly adapting. Of these, 140 responded only at both marked flexion and marked extension, forty‐seven responded only during flexion and twelve only during extension. Four slowly adapting fibres were activated specifically at intermediate joint positions. Outward twist of the tibia (abducting the foot) enhanced the discharge of most slowly adapting joint fibres. 3. Two rapidly adapting receptor types were noted. Pacinian corpuscle‐like receptors (fourteen fibres) responded transiently to joint movement in any direction regardless of initial position. Phasic joint receptors (thirty fibres) were rapidly adapting at most joint positions but could give a low rate sustained discharge when strongly stimulated. 4. Six slowly adapting posterior articular nerve fibres responded to succinylcholine, suggesting that they originated from muscle spindles. Spindle‐like receptors were usually tonically active at intermediate joint positions. 5. Eleven slowly conducting myelinated fibres responded only to extreme joint movement, which was probably noxious.
Article
We obtained human cruciate ligaments at the time of total knee replacement and from autopsy and amputation specimens, and examined histological sections of the ligaments for the presence of mechanoreceptors using the Bodian, Bielschowsky, and Ranvier gold-chloride stains for axons and nerve-endings. The cruciate ligaments obtained at the time of total knee replacement were too distorted by disease processes to be of use. The autopsy and amputation specimens, however, contained fusiform mechanoreceptor structures measuring 200 by seventy-five micrometers, with a single axon exiting from the capsule of the receptor. One to three receptors were found at the surface of each ligament beneath the synovial membrane, and were absent from the joint capsules and menisci. Morphologically the receptors resembled Golgi tendon organs, and it seems likely that they provide proprioceptive information and contribute to reflexes inhibiting injurious movements of the knee. This is the first histological demonstration of mechanoreceptors in human cruciate ligaments.
Article
Positive effects on the tensile characteristics of swine digital extensors were found following twelve months of exercise training. Compared to sedentary controls, the tendons from the exercised animals became stronger as a material and exhibited hypertrophy. These biomechanical results were supported by biochemical analyses of tendon composition. Exercise increased the concentration of collagen as well as the total weights of the tendons. For determining stress and strain in tendon material, we used specially designed instruments to measure the tendon cross-sectional area, and a video dimensional analyzer system to measure accurately its "non-contact" tensile strain. With these newly developed apparatus, the mechanical properties of the tendons were accurately determined so that the effects of exercise training could be compared.
Article
This study was designed to gain more detailed morphological information on skeletal tendons in the course of adaptation to physical loading. The effect on collagen fibrils was investigated in 6-week-old mice by means of electron microscopy. Physical loading was performed on a treadmill 5 days a week for 1, 3, 5, 7 and 10 weeks. Morphometric analysis of collagen fibrils revealed the mean diameter, the diameter distribution, the number and the cross-sectional area. The principal observations included:1. After one week of physical loading an increase in mean fibril diameter (30%, p≦0.01), in number (15%, p≦ 0.05), and in cross-sectional area (15%, p≦0.05), as well as a change in mean fibril diameter distribution. 2. From the third to the seventh week a fall under the level of the controls in mean diameter (26%, p≦0.01), in number (26%, p≦0.01), and a reduced cross-sectional area (17%, p≦0.01), accompanied by signs of splitting of individual collagen fibrils. 3. In the long-term study an increase in fibril number (29%, p≦0.01), a fall in mean diameter from 189 nm in the controls to 179 nm (p≦0.05) but no statistically significant change in the relative cross-sectional area (32%) per unit in comparison to unloaded tendons. The possible physiological implications of the findings are discussed in the light of several regulatory mechanisms known to appear during the course of physical loading in connective tissues.
Article
Discretized surface strains for human tendon and fascia were photogrammetrically determined with high-speed cinematography and were displayed topographically using three-dimensional computer graphics. Substantial differences were found between estimates of tissue strain measured from grip motion versus discretized strain estimates from high-speed films. The computer-generated contour maps also provide a useful technique for analyzing the nonhomogeneity of tendon and fascial strains during high rate tests.