Biomedical subjects

J C Woldstad

Publications and source records attributed to J C Woldstad.

4 recordsLinked to original sources

PubMed2000

Multiple two-dimensional displays as an alternative to three-dimensional displays in telerobotic tasks.

In this study a multiple-view two-dimensional (2D) display was compared with a three-dimensional (3D) monocular display and a 3D stereoscopic display using a simulated telerobotic task. As visual aids, three new types of visual enhancement cues were provided and evaluated for each display type. The results showed that the multiple-view 2D display was superior to the 3D monocular and the 3D stereoscopic display in the absence of the visual enhancement depth cues. When participants were provided with the proposed visual enhancement cues, the stereoscopic and monocular displays became equivalent to the multiple-view 2D display. Actual or potential applications of this study include the design of visual displays for teleoperation systems.

Computer Terminals↗

PubMed1998

Torso loading via a harness method activates trunk muscles less than a hand loading method.

There is a need for data comparing muscle activity under equivalent moments at the torso using different loading methods. In torso biomechanics, it is often necessary to apply moments to people and then measure or predict the muscle activity in response to the external load. Alternative methods exist to generate moments including applying forces by a chest harness and loads held in the hands. The limitation of previous research has been to use only one of the loading methods, generally harness loading, assuming it produces muscle activity equal to when loads are held in the hands. The objective of the this study was to test if equivalent moments at L3/L4 applied to subjects through two loading methods resulted in the same muscle activity. Subjects maintained a static posture while attempting a combination of flexion/extension, lateral bending, and torsion to counter the external loads applied via hand and harness loading methods. Hand and harness loading did not result in equal muscle activity as measured by electromyographic techniques. The left and right latissimus dorsi had increases in activity (16-25%) when loads were held with the hands instead of applied via the harness. Increased activity for hand loading was also found for the left and right rectus abdominis (13-17%) and left external oblique (24%). The left and right erector spinae and right external oblique exhibited the same activity for both loading methods. The current findings indicate that studies of torso loading using a shoulder harness to create torso moments may be lowering activity of some torso muscles.

Adult↗

PubMed1996

Posture prediction for static sagittal-plane lifting.

Three separate models are presented to predict the postures of humans performing static sagittal lifting tasks. The models use a common inverse-kinematics characterization to represent mathematically feasible postures, but explore different criteria functions for selecting a final posture. The first criterion assumes that subjects minimize the overall effort associated with a posture. The second criterion expresses effort locally as opposed to globally, and minimizes this value. The third criterion maximizes body stability. The postures predicted by these three models were compared to the postures assumed by 16 subjects performing 4 static sagittal lifting tasks. The results showed that all of the prediction errors were significantly greater than zero, but that the first objective function (minimum total torque) was more accurate than the other two criteria. The models were in general less accurate for postures that had lower hand positions than for those with higher hand positions.

Adult↗

PubMed1992

Floor/shoe slip resistance measurement.

A variety of slip measurement devices exist that provide estimates of both static and dynamic coefficient-of-friction (COF) values between one's shoes and the floor. Unfortunately, different shoe sole/heel materials, floor conditions, and contaminants will affect the tests in ways that result in widely varying COF estimates. This paper reviews the basic physics of such tests and describes a set of experiments to determine the static and dynamic COF values under operating conditions known to exist in different jobs. The results define a set of conditions wherein low (hazardous) COF values would exist (e.g., hard Neolite shoe material in contact with a wet, smooth walking surface). The results also question the use of light-load testing devices and static and slow speed reference COF values in the literature.

Accidental Falls↗