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A computational elbow joint model was developed with a main goal of providing complimentary data to experimental results. The computational model was developed and validated using an experimental elbow joint phantom consisting of a linked total joint replacement. An established in-vitro motion simulator was used to actively flex/extend the experimental elbow in multiple orientations. Muscle forces predicted by the computational model were similar to the experimental model in 4 out of the 5 orientations with errors less than 7.5 N. Valgus angle kinematics were in agreement with differences less than 2.3°. In addition, changes in radial head length, a clinically relevant condition following elbow reconstruction, were simulated in both models and compared. Both lengthening and shortening of the radial head prosthesis altered muscle forces by less than 3.5 N in both models, and valgus angles agreed within 1°. The computational model proved valuable in cross validation with the experimental model, elucidating important limitations in the in-vitro motion simulator’s controller. With continued development, the computational model can be a complimentary tool to experimental studies by providing additional noninvasive outcome measurements.

Seafaring occupations have been shown to place operators at an increased risk for injury. The purpose of this study was to understand better the demands of a moving environment on the ability of a person to perform specific lifting tasks. Subjects lifted a 15-kg load under four different lifting conditions. A 6-degree-of-freedom ship motion simulator imposed repeatable deck motions under foot while subjects executed the lifting tasks. Subjects were oriented in three different positions on the simulator floor to inflict different motion profiles. Electromyographic records of four muscles were collected bilaterally, and thoracolumbar kinematics were measured. A repeated-measures ANOVA was employed to assess trunk motions and muscle activities across lifting and motion conditions. The erector spinae muscles showed a trend toward significant differences for motion effects. Maximal sagittal velocities were significantly smaller for all motion states in comparison with the stable condition (p ≤ .01), whereas maximum twisting and lateral bending velocities were higher (p ≤ .05). Results suggest working in a moving environment will likely increase the operator’s risk for overexertion injuries, particularly to the trunk region.

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater knee loading in the frontal plane has been related to severity and rate of progression in knee osteoarthritis. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. However, little is known about specific effects that prosthetic foot damping may have on uninvolved limb loading. We hypothesized that uninvolved limb peak knee internal abduction moment (IAM) and loading rates would be greater when using a high-damping foot compared with a low-damping foot, across walking speeds. Eight healthy, young subjects walked in a prosthesis simulator boot using the experimental feet. Greater uninvolved limb first peak IAM (+16% in fast speed, P = .002; +11% in slow speed, P = .001) and loading rates (+11% in fast speed, P = .003) were observed when using the high-damping foot compared with low-damping foot. Within each foot, uninvolved limb first peak IAM and loading rates had a trend to increase with increased walking speed. These findings suggest that damping properties of prosthetic feet are related to uninvolved limb peak knee IAM and loading rates.

Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (R ranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent with the direction and amount of force applied, the time peak force was reached, push angle, and their stroke frequency between conditions.

We have developed a mathematical model and computer simulation of three-dimensional bobsled turning. It is based on accurate descriptions of existing or hypothetical tracks and on dynamic equations of motion including gravitational, normal, lift, drag, ice friction, and steering forces. The three-dimensional track surface model uses cubic spline geometric modeling and approximation techniques. The position of the sled on the track is specified by the two variables α and β in the along-track and cross-track directions, differential equations for which govern the possible motions of the sled. The model can be used for studies involving (a) track design, (b) calculation of optimal driver control strategies, and (c) as the basis for a real-time bobsled simulator. It can provide detailed quantitative information (e.g., splits for individual turns) that is not available in runs at actual tracks. The model also allows for comparison of driver performance with the numerically computed optimum performance, and for safe experimentation with risky driving strategies.

This study evaluates the action of 20 selected arm and torso muscles. The subjects were 19 windsurfers of different skill levels. Muscular activity was recorded electromyographically, using surface electrodes. The subjects were standing on a specially devised windsurf simulator in order to keep the different surf postures as standardized as possible. Through two-way ANOVA techniques, the electromyographic activity relative to its maximal isometric value was compared for different muscles, surf postures, and skill levels. Also, differences between the left and right sides of the body were investigated. From the results, the following may be concluded: (a) As all muscles display rather low activity (an average of less than 20% of their maximal isometric values), windsurfing does not seem very demanding of muscular force. (b) The M. flexor carpi radialis, together with the M. erector spinae, tend to exhibit higher levels of activity for beginners, which suggests, respectively, a more rigid grip on the wishbone and stronger low back muscle activation in order to keep a correct posture, (c) Left–right asymmetries mainly occur for symmetrical body postures, especially for the M. flexor carpi radialis and the M. erector spinae. As for the M. trapezius (pars superior), experienced surfers tend to display a dominant right asymmetry, (d) Muscle activity does not exhibit significantly different values for various surf postures. However, typical deviating postures, as observed in beginners, may induce higher levels of muscle activation.

Six trained male cyclists and triathletes participated in a double blind study to determine the effects of phosphate loading on maximal and endurance exercise performance. Subjects ingested either 1 gm of tribasic sodium phosphate or a glucose placebo four times daily for 3 days prior to performing either an incremental maximal cycling test or a simulated 40-km time trial on a computerized race simulator. They continued the supplementation protocol for an additional day and then performed the remaining maximal or performance exercise test. Subjects observed a 17-day washout period between testing sessions and repeated the experiment with the alternate supplement regimen in identical fashion. Metabolic data were collected at 15-sec intervals while venous blood samples and 2D-echocardiographic data were collected during each stage of exercise during the maximal exercise test and at 8-km intervals during the 404cm time trial. Results indicate that phosphate loading attenuated anaerobic threshold, increased myocardial ejection fraction and fractional shortening, increased maximal oxidative capacity, and enhanced endurance performance in competitive cyclists and triathletes.