Biomedical subjects

L A Rozendaal

Publications and source records attributed to L A Rozendaal.

9 recordsLinked to original sources

PubMed2003

Optical acceleration cancellation: a viable interception strategy?

Interception of fly balls requires active locomotion toward the point where catching can take place; as a result, the visual information guiding interception is affected by the catcher's own movement. The only interception theory currently available for a catcher standing in the plane of motion of the ball is Optical Acceleration Cancellation (OAC); in this strategy, the pseudo-optical variable "optical acceleration" (OA), if nonzero, specifies how the catcher should adjust his current velocity. We formulate a precise implementation of OAC where the catcher strives to maintain OA zero at all times and analyze its implications in terms of the catcher's interception behavior for different ball trajectories under air-friction-free, low-friction, and friction-dominated conditions. We conclude that the point in the ball trajectory where first visual contact (FVC) takes place determines to a large extent the ensuing interception behavior of the catcher. Conventional trajectories (FVC slightly above eye level, ball coming toward the catcher) result in fast acceleration to a constant velocity and successful interception. Trajectories with FVC below eye level typically result in unsatisfactory behavior of the catcher, who runs away from rather than toward the point of interception. In addition, ball trajectories are identified for which the OA equals zero even though the catcher is not on an interception course.

Acceleration↗

PubMed2003

The push force pattern in manual wheelchair propulsion as a balance between cost and effect.

We investigate the hypothesis that the direction of the propulsion force in manual wheelchair propulsion can be interpreted as a result of the balance between the mechanical task requirements and the driver's biomechanical possibilities. We quantify the balance at the joint level in the form of an effect-cost criterion, from which we predict the force direction that results in an optimal compromise. Kinematic and dynamic data were collected from nine habitual wheelchair users driving at four velocities (0.83, 1.11, 1.39, 1.67 m/s) and three external power levels (10, 20, 30 W). Experimental data and predictions are in good agreement in the middle and final part of the push; the effect-cost value in this region approximates the achievable maximum. Early in the push the effect-cost criterion predicts an upwards propulsion force whereas the experimental force is downwards, the difference probably being mainly attributable to the force generation dynamics of the muscles. As a result of the geometric features of large-rim manual wheelchairs, the mechanically required and biomechanically preferred force directions are not in accordance during a substantial part of the push, making even the best compromise a poor one. This may contribute to the low mechanical efficiency of manual wheelchair propulsion and the high incidence of shoulder complaints.

Adult↗

PubMed2002

Load on the shoulder in low intensity wheelchair propulsion.

OBJECTIVE: To assess the mechanical load on the glenohumeral joint and on shoulder muscles during wheelchair propulsion at everyday intensities. DESIGN: Model simulations based on experimental input dataBackground. Virtually nothing is known about the mechanical load on the upper extremity during wheelchair propulsion. Hand rim wheelchair propulsion is a significant risk factor for shoulder pain and injury among wheelchair users. A musculoskeletal model of the upper extremity during wheelchair propulsion will quantify the stresses placed on anatomic structures and may provide insight into the source of symptoms and injuries. METHODS: Three experienced wheelchair users underwent wheelchair exercise tests at combinations of two load levels (10 and 20 W) and two velocities (0.83 and 1.39m.s(-1)) during which input data were collected for a musculoskeletal model of the upper extremity. The model was then used for the estimation of the glenohumeral contact force, as well as individual muscle forces. RESULTS: Peak glenohumeral contact forces were between 800 and 1400 N (100-165% body weight) and differed significantly between load levels. Averaged over the push phase, these forces were 500-850 N. In absolute terms the m. deltoideus and rotator cuff muscles were highly active (>100N). In relative terms the load on the m. supraspinatus was high, with peak values of over 50% of its maximum attainable force. CONCLUSIONS: Low intensity wheelchair propulsion does not appear to lead to high contact forces. The muscle forces in the rotator cuff and especially in the m. supraspinatus are high. This might indicate a risk for muscle damage and the subsequent development of shoulder complaints, such as rotator cuff tears. RELEVANCE: Within the wheelchair user population, there is a high prevalence of upper extremity complaints. Not much is known about the causes of those complaints. Wheelchair propulsion is likely to be a major risk factor. If the (nature of this) mechanical load can be identified, specific exercise programs and/or design changes can be better tuned to prevent overuse injuries.

Adult↗

PubMed2001

Biomechanics and physiology in active manual wheelchair propulsion.

Manual wheelchair propulsion in daily life and sports is increasingly being studied. Initially, an engineering and physiological perspective was taken. More recently a concomitant biomechanics interest is seen. Themes of biomechanical and physiological studies today are performance enhancing aspects of wheelchair use and the ergonomics of wheelchair design. Apart from the propulsion technique the focus of biomechanics research of manual wheelchair propulsion is mainly towards injury mechanisms, especially phenomena of overuse to the upper extremity. Obviously, the vehicle mechanics of wheelchairs must be included within this biological framework. Scientific research is progressing, but is still hampered by methodological limitations, such as the heterogeneity and small numbers of the population at study as well as the inconsistency of employed technologies and methodologies. There is a need for consensus regarding methodology and research strategy, and a strong need for collaboration to improve the homogeneity and size of subject groups and thus the power of the experimental results. Thus a sufficiently strong knowledge database will emerge, leading to an evidence-base of performance enhancing factors and the understanding of the risks of wheelchair sports and long-term wheelchair use. In the light of the current biomechanical and physiological knowledge of manual wheelchair propulsion there seems to be a need for the stimulation of other than hand rim propelled manual wheelchairs.

Aerobiosis↗

PubMed2000

Force direction in manual wheel chair propulsion: balance between effect and cost.

OBJECTIVE: To evaluate the relationship between mechanical effect and musculoskeletal cost in wheelchair propulsion. DESIGN: Simulation of force direction, based on experimental data from wheelchair users. METHODS: For nine wheelchair users driving at 20 W, 1.39 m/s, the force direction was compared to simulation results based on a criterion defined as the ratio of mechanical effect and musculoskeletal cost. RESULTS: Simulation data compare well to the actual force direction for the middle and final parts of the push. CONCLUSIONS: The musculoskeletal cost of the exerted force must be taken into account to explain the observed propulsion pattern. Experienced users appear to optimize the force pattern by balancing mechanical effect and musculoskeletal cost of the pushing action. RelevanceThe effect-cost ratio may be a useful tool in analysing and improving wheelchair design.

Arm↗

PubMed2000

Relevance of the force-velocity relationship in the activation of mono- and Bi-articular muscles in slow arm movements in humans.

We have investigated whether differences in EMG activity in mono- and bi-articular muscles for concentric and eccentric contractions (van Bolhuis, Gielen, & van Ingen Schenau, 1998) have to be attributed to a specific muscle coordination strategy or whether they are merely a demonstration of adaptations necessary to adjust for muscle contractile properties. Slow, multi-joint arm movements were studied in a horizontal plane with an external force applied at the wrist. Kinematics and electromyography data from 10 subjects were combined with data from a 3-D model of the arm and a Hill-type muscle model. Data for both mono- and bi-articular muscles revealed a higher activation in concentric than in eccentric contractions. The model calculations indicated that the measured difference in activation (20%) was much larger than expected based on the force-velocity relationship (predicting changes of approximately 5%). Although these findings eliminate the force-velocity relationship as the main explanation for changes in EMG, it cannot be ruled out that other muscle contractile properties, such as history dependence of muscle force, determine muscle activation levels in the task that was studied.

Adult↗

PubMed1998

In vivo estimation of the glenohumeral joint rotation center from scapular bony landmarks by linear regression.

In this paper, a method is described for in vivo prediction of the glenohumeral joint rotation center (GH-r), necessary for the construction of a humerus local coordinate system in shoulder kinematic studies. The three-dimensional positions of five scapula bony landmarks as well as a large number of data points on the surface of the glenoid and humeral head were collected at 36 sets of cadaver scapulae and adjacent humeri. The position of GH-r in each scapula was estimated by mathematically fitting spheres to the glenoid and humeral head. GH-r prediction from scapula geometry parameters by linear regression resulted in a RMSE between measured and predicted GH-r of 2.32 mm for the x-coordinate, 2.69 mm for the y-coordinate and 3.04 mm for the z-coordinate. Application in vivo revealed a random humerus orientation error due to measurement inaccuracies of 1.35, 0.29 and 1.26 degrees standard deviation per rotation angle. The estimated total humerus orientation error including the offset error due to the regression model inaccuracy was 2.86, 0.84 and 2.69 degrees standard deviation. As these errors were about 15 and 20% of, respectively, the intra- and inter-subject variability of the humerus orientations measured, it is concluded that the method described in this paper allows for an adequate construction of a humerus local coordinate system.

Cadaver↗

PubMed1996

Influence of glenohumeral prosthesis geometry and placement on shoulder muscle forces.

The authors studied the influence of a changed geometry of the glenohumeral joint on the function of the muscles with the use of a shoulder prosthesis with an anatomic design. The changed geometry is characterized by 4 parameters: orientation of the glenoid, radius of the humeral head, position of the glenohumeral joint's geometric center in relation to the scapula, and position of the glenohumeral joint's geometric center in relation to the humeral shaft. The effect of changes in these 4 parameters was investigated with an inverse dynamic 3-dimensional musculoskeletal model of the shoulder. This was done at 60 degrees and 90 degrees of abduction and flexion. Gravity was the only external force on the arm. The magnitudes of the introduced changes are assumed to be a realistic representation of a changed geometry due to the implantation of a prosthesis. In most situations, the effect of a change in the 4 parameters on the exerted muscle force was small compared with the maximum force of a muscle. However, in relation to the initial reference force in a muscle, changes with an average of 50% occurred. Changes in the geometric center's position relative to the humerus are especially important, because they are closely related to the retroversion angle and can cause changes in force of up to 300%.

Biomechanical Phenomena↗

PubMed1993

Interaction between the joints in the shoulder mechanism: the function of the costoclavicular, conoid and trapezoid ligaments.

By developing a measurement method based on the palpation of bony landmarks, the three-dimensional positions of the scapula and clavicle can be measured at several angles of humerus elevation. An analysis of these measurements shows the interaction between all joints of the shoulder mechanism. With the help of a biomechanical shoulder model the role of some of the extracapsular ligaments in the motion pattern of scapula and clavicle can be derived. In addition, the interaction between the rotations in the acromioclavicular and sternoclavicular joints is shown, and the possible implications for the treatment of joint problems in the shoulder are discussed.

Biomechanical Phenomena↗