Effects of age and gender on maximum voluntary range of motion of the upper body joints

The maximum voluntary range of motion (ROM) of the major joints of the upper body was studied in a seated position and compared between young and elderly subjects. A total of 41 subjects (22 young male and female subjects aged 25 to 35 years, 19 elderly male and female subjects aged 65 to 80 years) took part in the experiment. In total, 13 maximum voluntary joint motions were performed by each subject. Age was found to have a non-uniform effect on the ROM of the joints investigated in this study. Its effect on ROM was joint specific and motion specific. The highest loss in ROM was observed in the neck and trunk, especially for neck extension, lateral flexion and axial rotation as well as for trunk lateral flexion and axial rotation. No significant age differences were observed in the elbow and wrist joint ROMs. The effect of gender on joint ROM was much weaker than that of age. Only four among the 26 joint ROMs investigated in this study were significantly different between the two gender groups.     

Analysis of isometric cervical strength with a nonlinear musculoskeletal model with 48 degrees of freedom

Background: Musculoskeletal models served to analyze head–neck motion and injury during automotive impact. Although muscle activation is known to affect the kinematic response, a model with properly validated muscle contributions does not exist to date. The goal of this study was to enhance a musculoskeletal neck model and to validate passive properties, muscle moment arms, maximum isometric strength, and muscle activity. Methods: A dynamic nonlinear musculoskeletal model of the cervical spine with 48 degrees of freedom was extended with 129 bilateral muscle segments. The stiffness of the passive ligamentous spine was validated in flexion/extension, lateral bending, and axial rotation. Instantaneous joint centers of rotation were validated in flexion/extension, and muscle moment arms were validated in flexion/extension and lateral bending. A linearized static model was derived to predict isometric strength and muscle activation in horizontal head force and axial rotation tasks. Results: The ligamentous spine stiffness, instantaneous joint centers of rotation, muscle moment arms, cervical isometric strength, and muscle activation patterns were in general agreement with biomechanical data. Taking into account equilibrium of all neck joints, isometric strength was strongly reduced in flexion (46 %) and axial rotation (81 %) compared to a simplified solution only considering equilibrium around T1–C7, while effects were marginal in extension (3 %). Conclusions: For the first time, isometric strength and muscle activation patterns were accurately predicted using a neck model with full joint motion freedom. This study demonstrates that model strength will be overestimated particularly in flexion and axial rotation if only muscular moment generation at T1–C7 is taken into account and equilibrium in other neck joints is disregarded.     

Effects of fire fighter protective ensembles on mobility and performance

Many studies have shown that fire fighter turnout gear and equipment may restrict mobility. The restriction of movement is usually due to a decrease in range of motion (ROM). It is important to know how much the decrease in ROM affects performance. The aim of this study was to determine the effects of fire fighter protective ensembles on mobility and performance by measuring static and dynamic range of motion (ROM) and job-related tasks. Eight healthy adults (5 males, 3 females), aged 20-40 years, participated in this study. The study consisted of measuring a battery of motions and fire fighter specific tasks while wearing a standard fire fighter ensemble (SE) or regular light clothing (baseline or BL). Several BL ROM tests were significantly (p < 0.05) different from the SE test, including a decrease in shoulder flexion, cervical rotation and flexion, trunk lateral flexion, and stand and reach. There was a significant decrease in time from SE to baseline performing the one-arm search task and object lift. These overall findings support the need for a comprehensive ergonomic evaluation of protective clothing systems to ascertain human factors issues. The development of a Standard Ergonomics Test Practice for further use in laboratories that conduct personal protective systems evaluations using human test subjects is recommended.     

Joint mobility and inclusive design challenges

The aim of this research study was to understand and evaluate the effect of different factors including age, gender, disabilities and medical conditions on joint mobility. Joint mobility data from a group of 66 people from a previously existing database has been re-analysed. Twenty four participants had disabilities and 42 participants were considered to be ‘able bodied’ with no recognised disability. For each individual, 18 joint range of motion values were measured and an ANOVA test was employed to demonstrate the influence of the selected factors on joint range of motion. Post Hoc (Tukey) tests were also performed to gain deeper insight into significance levels and correlations between the factors. The results clearly indicate that joint ROM significantly decreases (p < 0.05) with increasing age for arm abduction, arm medial and lateral rotation, wrist flexion and wrist adduction. Moreover, people with disabilities (wheelchair users and arthritis sufferers) showed a considerable decrease in joint mobility for arm flexion, arm abduction, arm lateral rotation, elbow flexion, elbow supination, wrist extension and wrist flexion. The results also highlight that designing products, equipment, services or workplaces against 5th and 95th percentile criteria is unable to provide appropriate and necessary support for achieving the objective of design inclusiveness. Rather designers should have a deep insight of the data variations at a predesign phase so that more appropriate and informed design decisions can be made that are more likely to be acceptable for a broad range of the population.     

Flexion and extension forces generated by wrist-dedicated muscles over the range of motion

An experiment was performed to evaluate the relationships among active range of motion (ROM), gender, wrist position and direction of force exertion in their effects on the magnitude of static force exerted by the wrist-dedicated muscles in wrist flexion and extension. This study employed 60 right-hand-dominant subjects (30 male, 30 female) between 20 and 30 years of age, all reporting no prior wrist injury and good to excellent overall physical condition. The ROM of each subject was used to determine the number of wrist positions evaluated for static maximal voluntary forces generated in wrist flexion and extension while they were instructed to relax their fingers; thus only the six wrist-dedicated muscles were employed in the exertion. The ANOVA procedure showed gender, wrist position, direction of force exertion, and the wrist position interaction with direction to have significant effects upon maximal force exertion. Females averaged 76.3% of the mean male flexion force and 72.4% for extension. On average, extension forces were found to be 83.4% of those generated by flexing the wrist-dedicated muscles.     

Upper quadrant postural changes of school children in response to interaction with different information technologies

The objective of this study was to quantitatively analyse the sitting posture of school children interacting with both old (book) and new (laptop and desktop computers) information technologies to test the hypothesis that posture is effected by the type of information technology (IT) used. A mixed model design was used to test the effect of IT type (within subjects) and age and gender (between subjects). The sitting posture of 32 children aged 4-17 years was measured whilst they read from a book, laptop, and desktop computer at a standard school chair and desk. Video images were captured and then digitized to calculate mean angles for head tilt, neck flexion, trunk flexion, and gaze angle. Posture was found to be influenced by IT type (p < 0.001), age (p < 0.001) and gender (p = 0.024) and significantly correlated to the stature of the participants. Measurement of resting posture and the maximal range of motion of the upper and lower cervical spines in the sagittal plane was also undertaken. The biophysical impact and the suitability of the three different information technologies are discussed.     

A normative database of thumb circumduction in vivo: center of rotation and range of motion

This article reports a systematic research effort aimed at establishing a normative database of thumb circumduction range of motion (ROM) and related kinematic characteristics in vivo while examining the effects of anthropometry, gender, and direction of rotation. Twenty-eight (14 men, 14 women) anthropometrically diverse participants performed maximum voluntary thumb circumductions as the trajectories of the surface markers placed on their thumb landmarks were recorded by an optoelectronic motion capture system. A globographic representation method was employed to model the measured marker trajectories, determining the center of rotation and central reference axes for thumb circumduction. Thumb ROM was quantified using (a) the joint sinuses expressing the thumb orientation change with respect to the reference axes and (b) cone volumes circumscribed by the thumb at the distal phalangeal, interphalangeal, and metacarpophalangeal levels. Data analyses resulted in statistical summaries of the derived kinematic and ROM measures with significant effects identified and regression equations predicting the cone volumes. Potential applications of this research include ergonomic design of hand-operated controls or devices and evaluation of thumb impairments or disorders.     

Effects of combined wrist flexion/extension and forearm rotation and two levels of relative force on discomfort

This study investigated perceived discomfort in an isometric wrist flexion task. Independent variables were wrist flexion/extension (55%, 35% flexion, neutral, 35% and 55% extension ranges of motion (ROM)), forearm rotation (60%, 30% prone, neutral, 30% and 60% supine ROM) and two levels of flexion force (10% and 20% maximum voluntary contraction (MVC)). Discomfort was significantly affected by flexion force, forearm rotation and a two-way interaction of force with forearm rotation (each p < 0.05). High force for 60%ROM forearm pronation and supination resulted in increasingly higher discomfort for these combinations. Flexion forces were set relative to the MVC in each wrist posture and this appears to be important in explaining a lack of significant effect (p = 0.34) for flexion/extension on discomfort. Regression equations predicting discomfort were developed and used to generate iso-discomfort contours, which indicate regions where the risk of injury should be low and others where it is likely to be high. Regression equations predicting discomfort and iso-discomfort contours are presented, which indicate combinations of upper limb postures for which discomfort is predicted to be low, and others where it is likely to be high. These are helpful in the study of limits for risk factors associated with upper limb musculoskeletal injury in industry.     

Upper quadrant postural changes of school children in response to interaction with different information technologies

The objective of this study was to quantitatively analyse the sitting posture of school children interacting with both old (book) and new (laptop and desktop computers) information technologies to test the hypothesis that posture is effected by the type of information technology (IT) used. A mixed model design was used to test the effect of IT type (within subjects) and age and gender (between subjects). The sitting posture of 32 children aged 4?–?17 years was measured whilst they read from a book, laptop, and desktop computer at a standard school chair and desk. Video images were captured and then digitized to calculate mean angles for head tilt, neck flexion, trunk flexion, and gaze angle. Posture was found to be influenced by IT type (p?<?0.001), age (p?<?0.001) and gender (p?=?0.024) and significantly correlated to the stature of the participants. Measurement of resting posture and the maximal range of motion of the upper and lower cervical spines in the sagittal plane was also undertaken. The biophysical impact and the suitability of the three different information technologies are discussed.     

Three-dimensional spinal motion and risk of low back injury during sheep shearing

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.     

Manufacture of a mechanical test rig to simulate the movements of forces within the shoulder

The shoulder complex, also known as the glenohumeral joint is the most manoeuvrable and one of the most well used joints of the human body. Over time problems can occur with the glenohumeral joint and surrounding muscles, cartilage, tendons and ligaments caused by ageing or by over stressing the shoulder complex. This work examines the design of a new innovative glenohumeral test rig. The test rig was required to imitate the movement of the humerus in the human body and replicate all the ranges of motion, which it can move in when combined with the relevant bones, muscles, ligaments and tendons in the shoulder complex. A variable force also had to be applied to the glenoid in all ranges of motion. Research had to be undertaken in the ranges of motion of the shoulder complex and the forces acting on the glenoid. Concept designs were initially created to mimic specific ranges of motion; adduction, flexion, internal (medial) and external (lateral) rotation for example. The concepts were evolved and combined to develop a test rig that would replicate any axial movement of the shoulder. Research determined the most appropriate manufacturing processes and materials so that the test rig could be manufactured in the material laboratories.     

The interrelationship of the thorax and pelvis under varying task constraints

The purpose of this study was to investigate the interrelationship between the thorax and pelvis during coupled movement patterns. Fifty-seven participants were assessed using an infrared motion analysis system to track trunk movement during maximal pelvis and thorax rotations over four trunk inclinations and two pelvic constraint conditions. A repeated-measures multivariate analysis of variance investigated the effects of forward trunk inclination and pelvic constraint on thorax and pelvic rotation. Forward trunk inclination from neutral to 45° resulted in a 46% (p < 0.001) decrease in axial pelvic rotation and a 15% (p < 0.001) decrease in axial thorax rotation with an unconstrained pelvis. A constrained pelvis resulted in a 15% (p < 0.001) decrease in axial thorax rotation. An externally constrained pelvis allowed the thorax to achieve an average of 18° (SD = 2°) greater rotational range of motion across all angles. This study reinforced the importance of allowing the pelvis to rotate during whole body axial rotation tasks.

Practitioner Summary: Results indicated that maximum axial trunk rotation is best achieved in a neutral posture, when the pelvis is allowed to contribute and flexion at the hips should be minimised. For example, if a recumbent task requires rotation of the torso, then the chair seat should be allowed to swivel.     

Biomechanical aspects of occupational neck postures during dental work

A typical occupational risk factor for developing neck symptoms is prolonged flexion of the cervical spine. The present aim was to determine joint moments and muscle activity of the neck during forward flexion of the cervical spine to evaluate the load in the neck region. Three dimensional video (3-D) and surface electromyography (EMG) from the splenius muscles were recorded in two common work postures. Using a 3-D static link segment model, moments at the atlanto-occipital (A-O) joint and the seventh cervical-first thoracal (C7-T1) joint were estimated. Maximal extension moments were estimated from maximal neck extension strength. Extension moments at the C7-T1 joint were significantly higher for a highly flexed position (45% of max) compared to a moderately flexed position (32% of max), but remained unchanged at the A-O joint (40% of max). The mean RMS amplitude was 9% of maximal EMG in both positions (no bilateral differences). This difference between mechanical load and muscle load indicates that EMG may seriously underestimate the total loads of the tissue. Lateral flexion influenced the lateral flexion moment while rotation did not influence the rotation moment. The study demonstrates the importance of quantification of joint loads in occupational risk assessment of the neck.

Relevance to industry

3-D biomechanical calculations provide information on the mechanical load during work. Because EMG may underestimate total tissue load, calculations of joint moments in combination with information on muscle activity and strength are necessary to estimate different tissue loading of significance for overall risk identification.     

Multi-segment trunk kinematics during a loaded lifting task for elderly and young subjects

The trunk is frequently modelled as one fixed segment ignoring possible multi-segmental contributions during manual handling. This study compared segmental trunk motion in a young and older population during a lifting task. Twelve elderly and 19 young subjects repeatedly lifted a 5 kg box from bench to shelf under two stance conditions. Displacement and angular trunk segment kinematics were recorded with an electromagnetic tracker system and then analysed. The elderly subjects displayed significantly increased pelvic and trunk displacement and significantly reduced pelvic and lower thorax (T10–L1) range of motion in both stance conditions. Upper thorax (C7–T10) motion was at times greater than lumbar motion and opposite to the lower segments and was related to the task while the lower segments contributed to both equilibrium and task requirements. Decreased segmental trunk angular kinematics may contribute to increased displacement kinematics and place the elderly at increased risk of injury and falling. The pelvis, lumbar spine, low thorax (T10–L1), upper thorax (C7–10) contributed uniquely and synchronously to trunk (C7–S2) mechanics during a lifting task. Reduced angular kinematics of the pelvis and low thorax contributed to increased displacement kinematics and hence increased the risk of falling in the elderly compared to the young. Investigations of trunk mechanics should include multi-segment analysis.     

The boundaries for joint angles of isocomfort for sitting and standing males based on perceived comfort of static joint postures

This study presents data for the joint angles of isocomfort (JAI) in sitting and standing males based on perceived comfort ratings for static joint postures maintained for 60 s. The JAI value was defined as a boundary indicating joint deviation (an angle) from neutral posture, within which the perceived comfort for different body joint postures is expected to be the same. An experiment for quantifying perceived comfort ratings was conducted using the free modulus method of magnitude estimation. Based on experimental results, regression equations were derived for each joint posture, to represent the relationships between different levels of joint deviation/joint posture and corresponding normalized comfort scores. The JAI values were developed for nine verbal categories of joint comfort. The JAIs with the marginal comfort levels, one of the nine verbal categories used, for most joint postures around the wrist, elbow, neck and ankle were similar to the maximum range of motion (ROM) values for these joints. However, the JAIs with the marginal comfort category for back and hip postures were much smaller than the maximum ROM values for these joints. There were no significant differences in JAI expressed in terms of the percentage of the corresponding maximum ROM values between sitting and standing postures. The relative 'marginal comfort index', defined as the percentage of JAIs for the marginal comfort relative to the corresponding maximum ROM values, for the hip was the smallest among all joints. This was followed, in an increasing order of the marginal comfort index, by the lower back and shoulder, while the marginal comfort index for the elbow joint was the largest. The results of this study suggest that static postures maintained for 60 s cause greater discomfort for the hip joint than for the other joints studied, and less discomfort for the elbow than for the other joints. The data about JAIs can be used as guidelines for enhancing postural comfort when designing a variety of human-machine tasks where static postures cannot be eliminated.     

Continues online exercise monitoring and assessment system with visual guidance feedback for stroke rehabilitation

Exercise therapy is a conventional intervention for stroke rehabilitation. Performance monitoring and feedback have shown to further improve the outcome of exercise therapy. This paper proposes a vision based system for monitoring exercise therapy which consists of 3 components: online exercise recognition, exercise performance analysis, and automatic visual feedback generation. The Microsoft Kinect was used for data acquisition. The exercise recognition component utilizes Kinect joints to continuously recognize and track the exercises. Upon completion of each exercise, joint flexibility and compensatory trunk motions are extracted for performance analysis. The visual feedback is a virtual skeleton augmented on top of the Kinect skeleton which displays the correct exercise path during execution. The Kinect skeleton and exercise definitions were applied to a motion hierarchy and animated using forward kinematics. Two additional experiments were also conducted to find accurate methods for calculating joint flexibility based on ROM measurement and trunk representation. Several datasets were created for system design and evaluation: 336 exercise sequences for exercise recognition, 25 records for ROM measurement, and 63 records for finding a suitable trunk representation method and compensatory motion detection. System evaluations showed that each component of the system is capable of producing outputs with significant accuracy.

     

Muscle activity and range of motion during active trunk rotation in a sitting posture

Twisted trunk postures during tractor driving are associated with low-back pain. The purposes of this study were to quantify the muscle activity as a function of twisting angle, to quantify the range of motion (ROM) during active trunk rotation and to determine whether there were any differences between tractor drivers and office workers and between twisting direction for these variables. The subjects performed exertions in a seated position, twisting from the neutral position to the end of the ROM. The results showed that external oblique and erector spinae had significantly different activation patterns depending on twisting direction. For the contralateral external oblique and the ipsilateral erector spinae, the muscle effort required to twist the trunk was low up to about 20° twisting angle, then the muscle effort needed to twist the trunk increased progressively. No significant differences due to occupation or twisting direction were found. The result implies that work in twisted trunk postures might be a risk factor for low-back pain.     

Interaction with a smartphone under different task and environmental conditions: Emergence of users’ postural strategies

Nowadays, interactions with smartphones are constantly increasing. These devices are used in a wide variety of situations by performing various tasks. The purpose of this study is to determine whether one or more strategies emerge when subjects freely send message and browse on the web in three environmental conditions: sitting with or without support and standing. Therefore, a hierarchical cluster analysis (HCA) was applied to the angular parameters of the neck and trunk as well as to the distance between the face and the telephone. These 3D motion analysis data were also processed taking into account the ergonomic recommendations from the Rapid Upper Limb Assessment in order to qualify the postural strategies highlighted by the HCA. The findings showed that there are three different postural strategies adopted by the subjects especially in the sagittal plane: a first one involves the neck without implying the trunk; a second one strongly mobilizes the trunk flexion without involving the neck; and a third postural strategy which combines these two behaviors. These three postural strategies depend on the environmental condition. Indeed, the postural strategy involving the trunk is associated with the presence of a support while the one involving the neck only appears in conditions without support. It is also observed that smartphone users mainly adopt harmful postures, whether due to excessive flexion of the neck, trunk or both. Even when subjects place themselves in the least harmful postures, there are always risks of musculoskeletal disorders in the short or long term.