Wheelchair propulsion kinematics in beginners and expert users: influence of wheelchair settings.

BACKGROUND: Biomechanical studies have linked the handrim wheelchair propulsion with a prevalence of upper limb musculoskeletal disorders. The purpose of this study was to examine the influence of the wheelchair settings on upper limb kinematics during wheelchair propulsion. Recordings were made under various wheelchair configuration conditions to understand the effect of wheelchair settings on kinematics parameters such shoulder, elbow and wrist angles. METHODS: Ten experts and ten beginners' subjects propelled an experimental wheelchair on a roller ergometer system at a comfortable speed. Twelve wheelchair configurations were tested. Kinematics were recorded for each configuration. Based on the hand position relatively to the handrim, the main kinematic parameters of wheelchair propulsion were investigated on the whole propulsion cycle and a key event such as handrim contact and release. FINDINGS: Compared to the beginner subjects, all the experts' subjects generally present higher joint amplitude and propulsion speeds. Seat height and antero-posterior axle position influence usage of the hand-rim, timing parameters and configurations of upper limb joints. Results seem to confirm that low and backward seat position allow a greater efficiency. Nevertheless, according that proximity of joint limit is a well known factor of musculoskeletal disorders, our results let us think that too low and backward seat position, increasing joints positions and amplitudes, could increase the risk of upper limb injuries in relation with manual wheelchair propulsion. INTERPRETATION: Kinematic differences highlight that future studies on wheelchair propulsion should only be done with impaired experienced subjects. Furthermore, this study provides indications on how wheelchair settings can be used for upper limb injury prevention.

A method for estimating three-dimensional human arm movement with two electromagnetic sensors.

Measurement of upper-limb movements is important in various domains. In this article, an upper-limb three-dimensional movement recording technique is proposed based on only two electromagnetic sensors. Two joints are considered with a total of seven degrees of freedom (DoF; three translations and four rotations). The chosen sequence of joint rotations is compliant with ISB recommendations: the shoulder is modelled with a ball and socket joint with three DoF and the elbow with a one DoF revolute joint. This article is focused on the procedure used to calibrate and sense the upper-limb movements from the raw data coming from the flock of birds sensors. The principle of the method is to define the centre of the wrist, elbow and shoulder joints in the frame of the adequate sensor. This operation is done by performing calibration gestures. Results are proposed and commented.

Surface electromyography activity of upper limb muscle during wheelchair propulsion: Influence of wheelchair configuration.

BACKGROUND: Biomechanical studies have linked handrim wheelchair propulsion with a prevalence of upper limb musculoskeletal disorders. The purpose of this study was to record upper limb muscle recruitment patterns using surface electromyography during wheelchair propulsion. Recordings were made for various wheelchair configurations to understand the effect of wheelchair configuration on muscle recruitment. METHODS: Ten paraplegic and ten able-bodied subjects propelled a test wheelchair on a roller ergometer system at a comfortable speed. Twelve wheelchair configurations were tested. Upper limb surface electromyography and kinematics were recorded for each configuration. Based on the hand position relative to the handrim, the propulsion cycle was divided into three phases to explain the activation patterns. FINDINGS: Compared to the able-bodied subjects, the paraplegic subjects presented higher activation. This is the case for all muscles in the early push phase, for the triceps brachii, pectoralis major and latissimus dorsi in the late push phase and for the trapezius, triceps brachii and latissimus dorsi during recovery. During early push, activation of nearly all muscles was affected by the axle position, where as seat height only affected biceps brachii and pectoralis major activation. During late push, the deltoid anterior was affected by axle position and the biceps brachii by seat height. During recovery, the trapezius was affected by axle position, the deltoid posterior by seat height and the biceps brachii by both. INTERPRETATION: Upper limb muscle recruitment differences highlight that future studies on wheelchair propulsion should only be done with wheelchair experienced paraplegic subjects. Furthermore, this study provides indications on how muscle recruitment is affected by wheelchair configuration.

Influence of the task on hand preference: individual differences among gorillas (Gorilla gorilla gorilla).

The degree of task complexity and bimanual complementarity have been proposed as factors affecting lateralization strength in humans. However, a large number of studies have demonstrated group-level lateral hand bias for different manual activities in numerous non-human primate species. However, no study has tested the effects that a variety of tasks may have in inducing differences in hand preference. Here, we aim to test if 3 adult gorillas exhibited a greater hand preference bias performing 4 tasks of varying complexity: grasping small versus large foods, proto-tool use task and tool use task involving greater visuospatial requirements. We found that (1) the complexity of the task does not necessarily induce a right-handed bias and (2) a subject can be right-handed for a complex task and left-handed for another one. These results, complemented by many publications on hand preference in non-human primates, reveal a great variability in hand preference, which makes it very difficult to deduce any details of hominin handedness with artefacts.

Reach to grasp kinematics and EMG analysis of C6 quadriplegic subjects.

The aim of the present study was to assess the kinematics and the muscular activity of the upper limb of subjects suffering from a spinal cord injury (SCI) at the C6 level during a grasping task. Data were compared to a control group composed of able-bodied subjects. The electrical activity of six major upper limb muscles and 3D motion of the arm were recorded. Results showed higher relative muscular solicitation for C6 patients especially for deltoïdus posterior and the pectoralis major and modifications of the range of motion of the corresponding joint angles. It appeared that, for C6 SCI subjects, the role of shoulder complex is highly relevant to initiate and control upper extremity movement, and so is important for their autonomy. Such data may be used to help clinician in decision making, e.g. for reconstructive surgery by musculotendinous transfer.

A clarification of Pouydebat et al., 2008, evolution of grasping among anthropoids.

Several statements by Pouydebat et al. (2008) do not adequately represent views of authors cited, in part because they reflect confusion in the literature about terminology regarding precision gripping. We address these problems, by tracing definitions of precision grips through the literature on manipulative behaviour and identifying the grip that is central to the Pouydebat et al. (2008) study. This allows us to offer a clarification of the statements by Pouydebat et al. (2008) regarding the sequence of appearance of human grip capabilities and possible morphological correlates to these capabilities in extant species.

Velocity-dependent changes of rotational axes in the non-visual control of unconstrained 3D arm motions.

We examined the roles of inertial (e(3)), shoulder-centre of mass (SH-CM) and shoulder-elbow articular (SH-EL) rotation axes in the non-visual control of unconstrained 3D arm rotations. Subjects rotated the arm in elbow configurations that yielded either a constant or variable separation between these axes. We hypothesized that increasing the motion frequency and the task complexity would result in the limbs' rotational axis to correspond to e(3) in order to minimize rotational resistances. Results showed two velocity-dependent profiles wherein the rotation axis coincided with the SH-EL axis for S and I velocities and then in the F velocity shifted to either a SH-CM/e(3) trade-off axis for one profile, or to no preferential axis for the other. A third profile was velocity-independent, with the SH-CM/e(3) trade-off axis being adopted. Our results are the first to provide evidence that the rotational axis of a multi-articulated limb may change from a geometrical axis of rotation to a mass or inertia based axis as motion frequency increases. These findings are discussed within the framework of the minimum inertia tensor model (MIT), which shows that rotations about e(3) reduce the amount of joint muscle torque that must be produced by employing the interaction torque to assist movement.

Upper limb muscle forces during a simple reach-to-grasp movement: a comparative study.

Muscle force knowledge during reaching is an important research field and tools development for measuring those forces is a challenging task, especially for clinical routines. The purpose of this study was, during a simple reach-to-grasp movement, to compare forces estimation from a Hill-type model and from the EMG-to-Force Processing (EFP) method. Ten healthy male volunteers were tested. Surface EMG signals were recorded from deltoid scapular, deltoid clavicular, triceps brachii, and biceps brachii. Ten repeated measures of right upper limb kinematics had been recorded. Three reaching distances were tested: 20, 30, and 40 cm. Muscle activations were calculated and forces were estimated by the two methods. Correlations and low RMS error found between the two methods indicate that EFP is a good way to estimate muscle forces for this kind of movement. This knowledge is essential in order to integrate these forces in reaching models developed nowadays in robotic, rehabilitation, and ergonomics field of research.