vendex and Musculoskeletal-Diseases

The present article examines the hypothesis that each individual has unique muscle coordination strategies (or signatures) that will have specific mechanical effects on their musculoskeletal system. As such, some strategies would make some people more at risk of developing musculoskeletal disorders than others. Identification of individual coordination strategies might provide insight into the development of musculoskeletal disorders.

Topics: Biological Variation, Individual; Electromyography; Humans; Muscle Strength; Muscle, Skeletal; Musculoskeletal Diseases; Torque

The purpose of this study is to investigate the relationships between subjective measures of discomfort and objective measures related to the assessment of postural stresses based on literature survey. Objective measures included posture holding time, maximum holding time (MHT), torque at joints, lifting index (LI) and compressive force (CF) at L5/S1. The major relationships identified in this literature survey were the following: 1) postural discomfort linearly increased with increasing holding time, and holding force, 2) whole body discomfort was inversely linearly proportional to the MHT, 3) body-part discomfort was related to objective measures such as torque at the relevant joint, 4) discomfort was strongly linearly related to LIs and CFs, and 5) the discomfort measured with the magnitude estimation was linearly related to that measured with Borg CR10. Thus, it is thought that discomfort might be used as a measure for quantifying postural stresses.

Topics: Ergonomics; Humans; Male; Musculoskeletal Diseases; Pain; Posture; Torque; Weight-Bearing

Females present more neck/shoulder musculoskeletal disorders and have different activation strategies of the shoulder girdle muscles than males. However, the sensorimotor performance and potential sex differences are still largely unexplored. The aim of this study was to investigate sex differences in torque steadiness and accuracy during isometric shoulder scaption. We also examined the amplitude and variability of the activation of the trapezius, serratus anterior (SA), and anterior deltoid muscles during torque output evaluation. Thirty-four asymptomatic adults (17 females) participated. Torque steadiness and accuracy were evaluated during submaximal contractions at 20 % and 35 % of peak torque (PT). There was no sex difference in torque coefficient of variation, but females had significantly lower torque standard deviation (SD) values than males at the two intensities evaluated (p < 0.001) and lower torque median frequency values compared to males, regardless of intensity (p < 0.01). Females had significantly lower absolute error values than males for torque output at 35 %PT (p < 0.01) and lower constant error values compared to males, regardless of intensity (p = 0.01). Females had significantly higher muscle amplitude values than males, except for SA (p = 0.10) and in general, females showed higher muscle activation SD values compared to males (p < 0.05). Females may require more complex muscle activation patterns to achieve a more stable and accurate torque output. Therefore, these sex differences may reflect control mechanisms that may also be at play when explaining the greater risk of neck/shoulder musculoskeletal disorders in females than males.

Topics: Adult; Electromyography; Female; Humans; Isometric Contraction; Male; Muscle, Skeletal; Musculoskeletal Diseases; Shoulder; Shoulder Joint; Superficial Back Muscles; Torque

Repetitive movements that involve a significant shift of the body's center of mass can lead to shoulder and elbow fatigue, which are linked to injury and musculoskeletal disorders if not addressed in time. Research has been conducted on the joint torque individuals can produce, a quantity that indicates the ability of the person to carry out such repetitive movements. Most of the studies surround gait analysis, rehabilitation, the assessment of athletic performance, and robotics. The aim of this study is to develop a model that estimates the maximum shoulder and elbow joint torque an individual can produce based on anthropometrics and demographics without taking a manual measurement with a force gauge (dynamometer). Nineteen subjects took part in the study which recorded maximum shoulder and elbow joint torques using a dynamometer. Sex, age, body composition parameters, and anthropometric data were recorded, and relevant parameters which significantly contributed to joint torque were identified using regression techniques. Of the parameters measured, body mass index and upper forearm volume predominantly contribute to maximum torque for shoulder and elbow joints; coefficient of determination values were between 0.6 and 0.7 for the independent variables and were significant for maximum shoulder joint torque (P<0.001) and maximum elbow joint torque (P<0.005) models. Two expressions illustrated the impact of the relevant independent variables on maximum shoulder joint torque and maximum elbow joint torque, using multiple linear regression. Coefficient of determination values for the models were between 0.6 and 0.7. The models developed enable joint torque estimation for individuals using measurements that are quick and easy to acquire, without the use of a dynamometer. This information is useful for those employing joint torque data in biomechanics in the areas of health, rehabilitation, ergonomics, occupational safety, and robotics. Clinical Relevance- The rapid estimation of arm joint torque without the direct force measurement can help occupational safety with the prevention of injury and musculoskeletal disorders in several working scenarios.

Topics: Demography; Elbow Joint; Humans; Movement; Musculoskeletal Diseases; Shoulder; Torque

A new adaptive impedance, augmented with backstepping control, time-delay estimation, and a disturbance observer, was designed to perform passive-assistive rehabilitation motion. This was done using a rehabilitation robot whereby humans' musculoskeletal conditions were considered. This control scheme aimed to mimic the movement behavior of the user and to provide an accurate compensation for uncertainties and torque disturbances. Such disturbances were excited by constraints of input saturation of the robot's actuators, friction forces and backlash, several payloads of the attached upper-limb of each patient, and time delay errors. The designed impedance control algorithm would transfer the stiffness of the human upper limb to the developed impedance model via the measured user force. In the proposed control scheme, active rejection of disturbances would be achieved through the direct connection between such disturbances from the observer's output and the control input via the feedforward loop of the system. Furthermore, the computed control input does not require any precise knowledge of the robot's dynamic model or any knowledge of built-in torque-sensing units to provide the desirable physiotherapy treatment. Experimental investigations performed by two subjects were exhibited to support the benefits of the designed approach.

Topics: Adult; Algorithms; Artificial Limbs; Biomechanical Phenomena; Equipment Design; Exoskeleton Device; Female; Humans; Male; Mechanical Phenomena; Musculoskeletal Diseases; Nonlinear Dynamics; Rehabilitation; Robotics; Torque; Upper Extremity; Young Adult

Neuromuscular electrical stimulation (NMES) is often used by clinicians as a therapeutic adjunct to improve quadriceps strength deficits following orthopedic knee conditions. The efficacy of NMES treatments is primarily dependent on the NMES training intensity, which is a direct result of NMES-induced torque production. The importance of NMES training intensity is well known, yet adequate NMES training intensities are often difficult to achieve due to a variety of limitations associated with NMES (eg, fatigue and patient discomfort). This article provides recommendations that a clinician can use to increase NMES training intensity when strengthening the quadriceps with NMES for orthopedic knee conditions. These recommendations should allow forceful contractions that can be sustained over a treatment with multiple repetitions without the rapid decline in force that is typically seen when NMES is used.

Topics: Electric Stimulation; Humans; Knee Joint; Musculoskeletal Diseases; Quadriceps Muscle; Torque

Though biomechanically determined guidelines exist for lifting, existing recommendations for pushing and pulling were developed using a psychophysical approach. The current study aimed to establish objective hand force limits based on the results of a biomechanical assessment of the forces on the lumbar spine during occupational pushing and pulling activities. Sixty-two subjects performed pushing and pulling tasks in a laboratory setting. An electromyography-assisted biomechanical model estimated spinal loads, while hand force and turning torque were measured via hand transducers. Mixed modelling techniques correlated spinal load with hand force or torque throughout a wide range of exposures in order to develop biomechanically determined hand force and torque limits. Exertion type, exertion direction, handle height and their interactions significantly influenced dependent measures of spinal load, hand force and turning torque. The biomechanically determined guidelines presented herein are up to 30% lower than comparable psychophysically derived limits and particularly more protective for straight pushing. Practitioner Summary: This study utilises a biomechanical model to develop objective biomechanically determined push/pull risk limits assessed via hand forces and turning torque. These limits can be up to 30% lower than existing psychophysically determined pushing and pulling recommendations. Practitioners should consider implementing these guidelines in both risk assessment and workplace design moving forward.

Topics: Adult; Biomechanical Phenomena; Electromyography; Female; Hand; Humans; Lumbar Vertebrae; Lumbosacral Region; Male; Muscle, Skeletal; Musculoskeletal Diseases; Occupational Diseases; Physical Exertion; Protective Factors; Task Performance and Analysis; Torque; Weight-Bearing; Work; Young Adult

Injuries due to manual valve handwheel operations are a major concern in the chemical process industry. Manual valves are used to start, stop, and control flow in process lines. The torque required to operate handwheels after the initial "breaking" can vary due to the size, design, and condition of the valve. This study tested four methods of turning the handwheel on a medium-sized gate valve at two different torque requirements (25 Nm and 50 Nm). The methods were compared to each other, in terms of efficiency, subjective ratings of perceived exertion, and electromyography activity of the upper extremity and trunk muscles. The results indicate that different methods and torque requirements are compensated for by the use of different muscles. Also, this use of different muscles, along with the increased mechanical advantage of the wrench, can affect the operator's actual and perceived comfort and efficiency while operating a valve handwheel.

Topics: Adolescent; Adult; Chemical Industry; Electromyography; Equipment Design; Ergonomics; Humans; Middle Aged; Musculoskeletal Diseases; Occupational Health; Pain Perception; Risk Assessment; Task Performance and Analysis; Torque; Upper Extremity; Young Adult

Repetitive use of hand-held power tools is associated with work-related upper extremity musculoskeletal disorders. Using a pneumatic nutrunner, 21 men completed twelve 360 repetitive fastener-driving sessions on three joints (hard, soft and control) at slow and fast pace, and two different work:rest patterns. Handgrip force and perceived exertions were collected throughout each session. For the control joint, the mean grip force exerted was 39.6% of maximum voluntary exertion (MVE) whereas during hard and soft joint sessions it was 48.9% MVE and 56.9% MVE, respectively. Throughout each session, the grip force decreased, more while operating soft and hard joints as compared with the control joint (regression slope: -0.022 and -0.023, compared with -0.007 N/drive, respectively), suggesting considerable upper extremity muscular effort by participants during torque buildup. Fast work pace resulted in higher average grip forces by participants but a greater decrease in the force as the session progressed. Providing rest breaks reduced perceived exertions. The findings gain additional knowledge for assembly task design to possibly reduce the hand/arm injury risks for the operator. Practitioner Summary: Powered hand tools are widely used in assembly and manufacturing industries. However, the nature of their repetitive use on human operator biomechanical and perceptual responses is not fully understood. This study examined work-related risk factors such as joint torque, pace and work:rest ratios on powered hand tool performance.

Topics: Adolescent; Adult; Construction Industry; Ergonomics; Fatigue; Humans; Joints; Male; Man-Machine Systems; Middle Aged; Musculoskeletal Diseases; Occupational Exposure; Torque; United States; Upper Extremity; Young Adult

This study assessed the muscular activity during root canal preparation through kinematics, kinetics, and electromyography (EMG).. The operators prepared one canal with RaCe rotary instruments and another with Flexo-files. The kinematics of the major joints was reconstructed using an optoelectronic system and electromyographic responses of the flexor carpi radialis, extensor carpi radialis, brachioradialis, biceps brachii, triceps brachii, middle deltoid, and upper trapezius were recorded. The joint torques of the shoulder, elbow and wrist were calculated using inverse dynamics. In the kinematic analysis, angular movements of the wrist and elbow were classified as low risk factors for work-related musculoskeletal disorders. With respect to the shoulder, the classification was medium-risk.. There was no significant difference revealed by the kinetic reports. The EMG results showed that for the middle deltoid and upper trapezius the rotary instrumentation elicited higher values. The flexor carpi radialis and extensor carpi radialis, as well as the brachioradialis showed a higher value with the manual method.. The muscular recruitment for accomplishment of articular movements for root canal preparation with either the rotary or manual techniques is distinct. Nevertheless, the rotary instrument presented less difficulty in the generation of the joint torque in each articulation, thus, presenting a greater uniformity of joint torques.

Topics: Adult; Biomechanical Phenomena; Electromyography; Endodontics; Female; Humans; Joints; Kinetics; Male; Muscle, Skeletal; Musculoskeletal Diseases; Occupational Diseases; Reference Values; Risk Factors; Root Canal Preparation; Time Factors; Torque

A biomechanical model for the analysis of dancers and their movements is described. The model consisted of 31 segments, 35 joints, and 539 muscles, and was animated using movement data obtained from a three-dimensional optical tracking system that recorded the motion of dancers. The model was used to calculate forces within the muscles and contact forces at the joints of the dancers in this study. Ground reaction forces were measured using force plates mounted in a sprung floor. The analysis procedure is generic and can be applied to any dance form. As an exemplar of the application process an Irish dance step, the rock, was analyzed. The maximum ground reaction force found was 4.5 times the dancer's body weight. The muscles connected to the Achilles tendon experienced a maximum force comparable to their maximal isometric strength. The contact force at the ankle joint was 14 times body weight, of which the majority of the force was due to muscle contraction. It is suggested that as the rock step produces high forces, and therefore the potential to cause injury, its use should be carefully monitored.

Topics: Achilles Tendon; Ankle Joint; Biomechanical Phenomena; Dancing; Humans; Joints; Models, Biological; Muscle, Skeletal; Musculoskeletal Diseases; Torque; Weight-Bearing

Powered hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders. In this study, subjective ratings of discomfort and acceptability of reaction forces were collected in an attempt to identify their associations with factors such as work location, and response covariates such as grip force and tool handle displacement. Three work configurations using pistol grip and right angle pneumatic nutrunners on horizontal and vertical surfaces were set up in the laboratory. Twenty healthy right-handed male participants operated four tools at nine locations and the corresponding subjective responses were collected. The results indicate that normalized grip force during the torque buildup period was a significant factor for both subjective ratings. For the unacceptable torque reactions across the three tool configurations, the ratio of hand moment impulse over tool torque impulse was significantly greater than for the acceptable reactions. For pistol grip tools used on the vertical surface, as the working height increased 30 cm, the odds of an unacceptable rating over an acceptable rating increased 1.6 times. Prediction models for subjective ratings of discomfort and acceptability provide insight regarding either workstation design or exposure control. These models can further be used to establish exposure limits based on handle displacement and grip force.

Topics: Adult; Biomechanical Phenomena; Cumulative Trauma Disorders; Equipment Design; Equipment Safety; Ergonomics; Hand; Hand Strength; Humans; Male; Models, Statistical; Models, Theoretical; Musculoskeletal Diseases; Musculoskeletal System; Occupational Diseases; Occupational Exposure; Perception; Pilot Projects; Posture; Risk Factors; Torque; Vibration

Powered hand tools produce reaction forces that may be associated with upper extremity musculoskeletal disorders. The handle displacement, grip force and upper limb muscle activity (electromyography (EMG)) due to the effects of operator experience, working height and distance, type of tool and fastener joint hardness were measured in this study with 15 experienced and 15 novice nutrunner users. The results show that when pistol grip handles were used to work on a horizontal surface, experienced users allowed an average handle displacement of 7.9 degrees, while novice users allowed 11.5 degrees. Average EMG scaled by reference voluntary contraction (RVC) at forearm flexors, forearm extensors and biceps were greater for experienced users (318% RVC, 285% RVC, 143% RVC, respectively) than for novice users (246% RVC, 219% RVC, 113% RVC, respectively). Experienced users exerted more grip force than novice users when using right angle handles, but less force when using pistol grip handles. The results suggest that it is possible to minimize tool handle displacement by adapting the workplace layout to permit different working postures for each user group.

Topics: Adolescent; Adult; Aged; Cumulative Trauma Disorders; Electromyography; Hand Strength; Humans; Male; Middle Aged; Muscle Contraction; Muscle, Skeletal; Musculoskeletal Diseases; Occupational Diseases; Pilot Projects; Posture; Torque; Upper Extremity

The objective of this study is to investigate the workstation and tool effects on the responses of the powered hand tool operator reacting against the impulsive reaction forces that may be associated with upper extremity musculoskeletal disorders. The study demonstrated a means of direct measurement of force at the interface between the tool and the operator. Fifteen experienced male operators performed three independent work configurations: pistol grip and right angle tools used on the horizontal surface and pistol grip tools used on the vertical surface, in the laboratory. A full factorial experiment consisting of 36 conditions was designed to examine the effects of working height, distance, tool, and fastener joint hardness on handle displacement and grip forces. The results indicate that operator responses were affected by different factors depending on the work configuration. When pistol grip tools were used on the vertical surface, the mean handle displacement decreased from 9.9 degrees to 7.3 degrees as the working height increased from 30 cm below shoulder to 30 cm above shoulder. When right angle tools were used, the greatest handle displacement (51.1mm) and grip force (84.7% MVC) during torque reactions were measured at 30 cm below elbow and 40% forward reach away from the operator. This study provides quantitative information that can be used for workstation design and tool selection to reduce the torque reaction experienced by powered nutrunner operators.

Topics: Adult; Equipment Design; Equipment Safety; Hand; Hand Strength; Humans; Male; Middle Aged; Musculoskeletal Diseases; Occupational Health; Surveys and Questionnaires; Torque; United States

This study evaluated the upper limb, dynamic, mechanical response parameters for 14 male assembly workers recruited from selected jobs based on power tool use. It was hypothesized that the type of power tool operation would affect stiffness, effective mass, and damping of the upper extremity; and workers with symptoms and positive physical examination findings would have different mechanical responses than asymptomatic workers without physical examination findings. Participants included operators who regularly used torque reaction power hand tools, such as nutrunners and screwdrivers, and nontorque reaction power hand tools, such as riveters. The mechanical parameters of the upper limb were characterized from the loading response of an apparatus having known dynamic properties while worker grasps an oscillating handle in free vibration. In addition, all workers underwent a physical examination, magnetic resonance imaging, and completed a symptom survey. Workers were categorized as controls or cases based on reported forearm symptoms and physical exam findings. A total of seven workers were categorized as cases and had less average mechanical stiffness (46%, p > 0.01), damping (74%, p > 0.01), and effective mass (59%, p > 0.05) than the seven workers categorized as controls. Magnetic resonance imaging (MRI) findings suggestive of muscle edema were observed for two workers classified as cases and who regularly used torque reaction power tools. No MRI enhancement was observed in the seven subjects who did not regularly use torque reaction power tools. The ergonomic consequences of less stiffness, effective mass, and damping in symptomatic workers may include reduced capacity to react against rapidly building torque reaction forces encountered when operating power hand tools.

Topics: Adult; Biomechanical Phenomena; Ergonomics; Hand Injuries; Humans; Job Description; Magnetic Resonance Imaging; Male; Manufactured Materials; Middle Aged; Musculoskeletal Diseases; Occupational Health; Torque; Vibration

Muscle weakness frequently accompanies conditions with musculoskeletal pain. It is not clear if this attenuation of force is due to peripheral or central processes. The effect of experimental muscle pain on maximal voluntary contraction torque and peripheral contractile properties was therefore assessed. Experimental muscle pain reduced the torque produced by isometric knee extension, but the contractile properties assessed by twitch interpolation were not affected. This indicates that force inhibition by muscle pain is centrally mediated. This has clinical implications for rehabilitation and training of patients with musculoskeletal pain.

Topics: Adult; Afferent Pathways; Female; Humans; Male; Middle Aged; Muscle Contraction; Muscle Weakness; Muscle, Skeletal; Musculoskeletal Diseases; Neural Inhibition; Neurons, Afferent; Nociceptors; Pain; Pain Measurement; Reaction Time; Reflex; Spinal Cord; Torque

Thirty-eight athletes with unilateral patellar tendinopathy (17 with a tendinopathy of the main body of the tendon, and 21 with an insertional tendinopathy) underwent ultrasound-guided multiple percutaneous longitudinal tenotomy under local anaesthetic infiltration after failure of conservative management. Thirty-four patients were reviewed at least 24 months after the operation. Sixteen patients were rated excellent, nine good, eight fair, and five poor. Nine of the 13 patients with a fair or poor result had an insertional tendinopathy, and eight of them underwent a formal exploration of the patellar tendon. Before the operation, there were some areas of altered echogenicity at and around the site of involvement. These were still visible 6 wk after surgery in 70% of the patients. At the latest follow-up, in the patients with an excellent or good result, the tendon was generally isoechogenic but slightly thicker (P = 0.06) than the normal contralateral. In the patients with a fair or poor result, the tendon was significantly thicker than the contralateral (P = 0.03), and showed some areas of mixed echogenicity. In the patients in whom the procedure was successful, the thicker operated tendon did not interfere with physical training. Bilateral isokinetic peak torque (Nm), average work (Joules), and average power (Watts) were tested at 90 degrees x s(-1). Immediately before the operation, there was no significant difference in peak torque, but total work and average power were significantly lower in the limb to be operated (0.01 < P < 0.05). By the end of the study, although peak torque was, on average, within 7% of the unoperated limb, total work and average power were still significantly lower than in the unoperated limb (0.01 < P < 0.04). Percutaneous longitudinal internal tenotomy is simple, can be performed on an outpatient basis, requires minimal follow-up care, does not hinder further surgery should it be unsuccessful, and, in our experience, has produced no significant complications. In our hands, it has become the first line operative intervention in the treatment of chronic patellar tendinopathy after failure of conservative management. However, patients should be advised that, if they suffer from an tendinopathy at the attachment of the patellar tendon at the lower pole of the patella, a formal surgical exploration with stripping of the paratenon is preferable.

Topics: Adolescent; Adult; Ambulatory Surgical Procedures; Anesthesia, Local; Athletic Injuries; Chronic Disease; Ergometry; Female; Follow-Up Studies; Humans; Isometric Contraction; Male; Middle Aged; Minimally Invasive Surgical Procedures; Musculoskeletal Diseases; Patellar Ligament; Prospective Studies; Range of Motion, Articular; Torque; Treatment Outcome; Ultrasonography, Interventional; Weight-Bearing