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Biomedical subjects

G J Gouw

Publications and source records attributed to G J Gouw.

16 recordsLinked to original sources
PubMed1996

Development of a grip force dependent hand-arm vibration model.

The driving-point mechanical impedance of the human hand-arm system is strongly dependent on the grip force and excitation frequency. In this study, the biodynamic response of the human hand-arm is characterized by three and four degree-of-freedom (DOF) linear and nonlinear mass excited model incorporating grip force dependence of the restoring and dissipative properties. The model parameters are identified by minimizing a constrained objective function compromising impedence magnitude and phase errors between the computed and measured target driving-point mechanical impedance characteristics. The target impedance values are established in the 10 to 1000 Hz frequency range from the measurements performed in the three orthogonal directions (Xh, Yh and Zh) using 2 x g peak acceleration sinusoidal excitation and different magnitudes of constant grip force ranging from 10 to 50 N. The linear and nonlinear models are analyzed to determine the driving-point mechanical impedance characteristics for different levels of grip force. The computed response characteristics are compared to the target values to demonstrate the validity of the proposed models. The results of the study revealed that the four-DOF nonlinear grip force dependent model yields good correlation with the measured response in all three directions, for the range of grip forces considered.

Arm↗
PubMed1995

Influence of power tool-related parameters on the response of finger flexor muscles.

Surface electromyography (EMG) and statistical analysis techniques were applied to investigate the response of finger flexor muscles to hand-transmitted vibration in all the three orthogonal directions. The trends in measured data were examined to derive the influence of variations in the tool-related parameters. Single-factor and multi-factor statistical analyses were performed to establish the significance of influence of different individual and coupled power tool-related parameters. The analysis of variance (ANOVA) results indicated that the vibration direction, acceleration and grip force influence the EMG of finger flexor muscles in a significant manner (P < 0.001), while the effect of vibration frequency was observed to be insignificant (P > 0.9). The electrical activity measured under different vibratory test conditions was observed to be 1.5-6.0 times higher than that measured under the static loads. The increase in electrical activity of the finger flexor muscles with an increase in the grip force was observed to be most significant under static as well as dynamic loading conditions.

Analysis of Variance↗
PubMed1995

A study of hand grip pressure distribution and EMG of finger flexor muscles under dynamic loads.

A matrix of miniature and flexible pressure sensors is proposed to measure the grip pressure distribution (GPD) at the hand-handle interface of a vibrating handle. The GPD was acquired under static and dynamic loads for various levels of grip forces and magnitudes of vibration at different discrete frequencies in the 20-1000 Hz range. The EMG of finger flexor muscles was acquired using the silver-silver chloride surface electrodes under different static and dynamic loads. The measured data was analysed to study the influence of grip force, and magnitude and frequency characteristics of handle vibration on: (i) the local concentration of forces at the hand-handle interface; and (ii) the electrical activity of the finger flexor muscles. The results of the study revealed high interface pressure near the tips of index and middle fingers, and base of the thumb under static grip conditions. This concentration of high pressure shifted towards the middle of the fingers under dynamic loads, irrespective of the grip force, excitation frequency, and acceleration levels. The electrical activity of the finger flexor muscles increased considerably with the grip force under static as well as dynamic loads. The electrical activity under dynamic loads was observed to be 1.5-6.0 times higher than that under the static loads.

Computer Simulation↗
PubMed1994

Athletic footwear affects balance in men.

Stable equilibrium during locomotion is required for both superior performance of sports and prevention of injuries from falls. A recent report indicated that currently available athletic footwear impairs stability in older men. Since this discovery, if confirmed, seems important to both competitive athletes and the physically active general public, we performed an experiment using similar methods on a younger population. We tested the hypothesis that midsole thickness is negatively, and hardness positively related to dynamic equilibrium, in 17 healthy adult men (mean(s.d.) age 33(11.13) years) via a balance beam method. Subjects walked along a 9-m long beam at 0.5 m s-1 once barefoot and six times wearing identical pairs of experimental shoes which differed only in midsole hardness and thickness which spanned the respective ranges currently available in footwear. Falls from the beam (balance failures) were quantified. Balance failures varied significantly in relation to midsole hardness and thickness, and there was a strong trend toward interaction of these variables (P = 0.09). Midsole hardness was positively related to stability, and midsole thickness was negatively related, which confirms the previous report. Hence, shoes with thick-soft soles, similar to modern athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability. The pair with the poorest stability (A 15-thick; 12.34 balance failures per 100 m) produced 217% more balance failures than those associated with the best stability (A 50-thin; 3.89 balance failures per 100 m). Since most types of athletic footwear and many other shoes incorporate midsoles with hardness and thickness associated with poor stability, we conclude that both athletic performance and public safety could be enhanced through stability optimized footwear.

Adult↗
PubMed1993

Development of linear and nonlinear hand-arm vibration models using optimization and linearization techniques.

Hand-arm vibration (HAV) models serve as an effective tool to assess the vibration characteristics of the hand-tool system and to evaluate the attenuation performance of vibration isolation mechanisms. This paper describes a methodology to identify the parameters of HAV models, whether linear or nonlinear, using mechanical impedance data and a nonlinear programming based optimization technique. Three- and four-degrees-of-freedom (DOF) linear, piecewise linear and nonlinear HAV models are formulated and analyzed to yield impedance characteristics in the 5-1000 Hz frequency range. A local equivalent linearization algorithm, based upon the principle of energy similarity, is implemented to simulate the nonlinear HAV models. Optimization methods are employed to identify the model parameters, such that the magnitude and phase errors between the computed and measured impedance characteristics are minimum in the entire frequency range. The effectiveness of the proposed method is demonstrated through derivations of models that correlate with the measured X-axis impedance characteristics of the hand-arm system, proposed by ISO. The results of the study show that a linear model cannot predict the impedance characteristics in the entire frequency range, while a piecewise linear model yields an accurate estimation.

Arm↗
PubMed1993

Examining motion in the cervical spine. I: Imaging systems and measurement techniques.

Instruments for measuring mobility in the cervical spine range from plumb-lines and inclinometers to sophisticated optoelectronic systems. In order to investigate the need and possible uses for an enhancement to a new diagnostic instrument, we examine some of the available diagnostic systems suitable for cervical motion analysis. These should be of practical use in a clinical setting for the diagnosis of soft tissue injuries. We begin by evaluating the respective roles of plain radiographs, cineradiography, computer tomography, and magnetic resonance imaging in examining the cervical spine. Then we consider Moiré photography, inclinometers, and some opto-electronic scanners, as well as the mathematical techniques needed to correlate skin and spine motion with these devices. We find that there does not appear to be an effective non-invasive tool for comprehensive clinical cervical motion analysis; in particular, coupled joint motion is inadequately quantified. Improperly diagnosed cervical spine injuries, such as hyperextension and hyperflexion, may result in chronic long-term effects. Therefore, instrumentation that would permit objective, routine clinical evaluation of patients could help to avoid such situations.

Biomechanical Phenomena↗
PubMed1993

Examining motion in the cervical spine. II: Characterization of coupled joint motion using an opto-electronic device to track skin markers.

Analysis of coupled motion in the cervical spine may be useful in helping to identify injuries. In order to investigate this possibility, the nature of coupled motion in the spine and previous investigations on this subject are reviewed here. An enhanced set of displays are developed for an existing opto-electronic device employed for the non-invasive measurement of movement in the upper spine. This instrument consists of a high resolution motion analysis system which tracks small infrared emitting diodes (IREDs). Kinematic data for the motion of the markers is processed and absolute coordinates for the location of each IRED at any time are tabulated; coupled motion with respect to a fixed calibration frame, as well as for vertebrae relative to each other, is deduced from these. Overall analysis provided by the original device includes assessment of cervical lordosis, thoracic kyphosis, and inter-segmental mobility. Characterization of coupled motion, in particular, involves a series of plots showing principal versus secondary motion. Principal movements include flexion-extension, lateral bending, and axial rotation, corresponding to motion in the sagittal, transverse, and horizontal planes, respectively. Mobility is represented in terms of the direction angles made by virtual vectors orthogonal to the planes made by markers on the head, neck, and shoulders. Development of the enhanced displays and the required refinements are described. Precision of the deduced angles is found to be approximately 1 degree. This representation of coupled motion is expected to be valuable in improving the accuracy of attempts to identify normal versus pathological motion in the cervical spine.

Algorithms↗
PubMed1992

Shoe sole thickness and hardness influence balance in older men.

OBJECTIVE: To test the hypothesis that shoes with thick, soft midsoles, such as modern running shoes, provide better stability in older individuals than those with thin-hard midsoles. In addition, we examined the relation between footwear comfort and stability and stability when barefoot. DESIGN: Randomized-order, cross-over, controlled comparison. SETTING: Subjects were drawn from an internal medicine practice. PARTICIPANTS: A random sample of 25 healthy men, minimum age 60 years. Additional selection criteria were absence of disabilities influencing ability to walk and lack of history of frequent falls. MEASUREMENTS: Balance failure frequency, which was defined as falls from the beam per 100 meters of beam walking when 10 passes were made down a 9 M long balance beam. Comfort rating was based on an ordinal scale. RESULTS: Contrary to the hypothesis: (1) midsole softness was associated with poor stability (F(2,48) = 17.9, P < 0.0001); (2) thick midsoles also provided poor stability (F(1,24) = 7.36, P < 0.01). When barefoot, subjects showed 19% higher balance failure frequency than with the poorest shoe and 171% greater than the best shoe (t = 5.33, P < 0.0001). Higher comfort was generally found in shoe types associated with higher balance failure frequency. CONCLUSIONS: For optimal stability, shoes with thin, hard soles are preferable for older individuals. Health professionals should exercise caution when recommending shoes with thick, yielding midsoles, such as running shoes, to unstable elderly individuals. Older men and women with a history of falls or who are obviously unstable, should avoid barefoot locomotion.

Accidental Falls↗
PubMed1991

Athletic footwear: unsafe due to perceptual illusions.

Modern athletic footwear provides remarkable plantar comfort when walking, running, or jumping. However, when injurious plantar loads elicit negligible perceived plantar discomfort, a perceptual illusion is created whereby perceived impact is lower than actual impact, which results in inadequate impact-moderating behavior and consequent injury. The objective of this study was to examine how plantar tactile (mechanical) events affect perceived plantar discomfort. Also, we evaluated the feasibility of a footwear safety standard we propose, which requires elimination of the above illusion. Twenty subjects gave numerical estimates of plantar discomfort produced by simulated locomotion (concurrent vertical (0.1-0.7 kg.cm-2) and horizontal (0.1-0.9 kg.cm-2) plantar loads), with the foot supported by either a smooth rigid surface or a rigid surface with 2 mm high rigid irregularities. Vertical or horizontal load alone evoked no discomfort (P greater than 0.05), whereas together, discomfort emanated from loads as low as 0.4 kg.cm-2. Irregularities heightened discomfort by a factor of 1.89. This suggests that the proposed safety standard is feasible, since compliance could be achieved simply by adding surface irregularities to insoles and by other changes that heighten localized plantar loads. However, until this standard is adhered to, it might be more appropriate to classify athletic footwear as "safety hazards" rather than "protective devices".

Adult↗
PubMed1989

Running-related injury prevention through innate impact-moderating behavior.

The purpose of these experiments was to test the Robbins and Hanna hypothesis, which relates differences in discomfort from localized deformation at certain positions on the plantar surface to protective behavior (intrinsic foot shock absorption). A penetrometer was used to quantify the relations between localized load and pain and between load and depth of deformation. The magnitude of load required to elicit pain varied significantly (P less than 0.005) in relation to position on the plantar surface. With a load of 9 kg and a 10 mm spherical end on the penetrometer, 6% of the sample reported pain at the heelpad, 32% at the distal first digit, and 66% at the first metatarsal-phalangeal joint. This pattern was predicted by the Robbins and Hanna thesis. Two deformation patterns were observed which were best explained by deformation constraint by tight trabecular tethering of the epithelial membrane at the heelpad and distal first digit and unrestricted deformation due to loose trabecular tethering of the epithelial membrane at the first metatarsal-phalangeal joint. These data provide insight into how, when barefoot, the plantar surface resists perforation yet provides protection to local bony structures. These data further support the notion that plantar sensory feedback plays a central role in safe and effective locomotion.

Adipose Tissue↗
PubMed1988

Overload protection: avoidance response to heavy plantar surface loading.

Current footwear which are designed for use in running are examples of intentional biomechanical model integration into device design. The inadequacy of this footwear in protecting against injury is postulated to be due to fixation on inadequate models of locomotory biomechanics that do not provide for feedback control; in particular, an hypothesized plantar surface sensory-mediated feedback control system, which imparts overload protection during locomotion. A heuristic approach was used to identify the hypothesized system. A random series of loads (0 to 164 kg) was applied to the knee flexed at 90 degrees. In this testing system, plantar surface avoidance behavior was the difference between the sum of the leg weight and the load applied to the knee, and the load measured at the plantar surface; this was produced by activation of hip flexors. Significant avoidance behavior was found in all of the subjects (P less than 0.001). On all surfaces tested, including modern athletic footwear (P less than 0.001), its magnitude increased directly in relation to the load applied to the knee (P less than 0.001). There were significant differences in avoidance behavior in relation to the weight-bearing surfaces tested (P less than 0.05). With the identification of a feedback control system which would serve to moderate loading during locomotion, an explanation is provided as to why current athletic footwear do not protect and may be injurious; thus allowing the design of footwear which may be truly protective.

Athletic Injuries↗
PubMed1986

Effect of muscular activity on valgus/varus laxity and stiffness of the knee.

Quantitative changes in valgus/varus knee stability with different levels of muscular activity were determined for five subjects. A specially designed machine was used to measure resistance to angulation in the frontal plane. This device held the thigh stationary, the knee straight, an cycled the leg from side to side at a constant rate between present moment limits. Resistance to this forced valgus/varus motion was measured simultaneously with torque about the knee in the sagittal plane. Muscle activity was monitored by electromyography (EMG). Direct comparison of moment-rotation characteristics allowed changes in stability to be quantified as a function of extension and flexion torque. Extension torques less than 20% of the maximum increased varus stability more than valgus stability. Flexion torques of the same relative magnitude increased valgus stability more than varus stability. Comparison with the literature suggested that prevention of opening of the lateral side of the joint under varus loading was responsible for increased varus stability with increasing torque, both with extension and flexion torques.

Electromyography↗
PubMed1986

Computer corner #13. Computerized examinations in orthopaedics.

Computerized examinations can play an important role in the evaluation and education of trainees in orthopaedics. Several centers in the United States and Canada are currently using these, thus allowing an exchange of examination questions. Once a system is set up, only minimal involvement on the part of the instructor and office staff is required. All participants--trainees and instructors--can benefit from computerized examinations.

Computer-Assisted Instruction↗
PubMedDate not supplied

Protective sensation of the plantar aspect of the foot.

The scientific literature suggests that barefoot activity may be beneficial. There is a current trend in recreational barefoot activity in children and adults, and barefoot running among athletes. Although the type of skin over most of the body (hairy skin) seems to be easily injured by painful abrading loads, little is known about protection provided by plantar sensory feedback against damage from excessive wear during barefoot locomotion. To evaluate this, we administered a volley of 35 painful abrading loads to glabrous and hairy skin sites over a 5-min period, and examined its effects for signs of cutaneous injury in a sample of 12 normally shod healthy male subjects. Compared with hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. Furthermore, painful stimulation produced visible redness and hypersensitivity in all subjects at the hairy skin site 24 hr after stimulation, whereas only 8.3% reported hypersensitivity and none showed erythema at the plantar area 1 day later. We found that plantar skin possesses a higher pain threshold to abrading stimuli than hairy skin. In fact, loading of the plantar area was limited to innocuous levels due to intolerable pain. We conclude that plantar skin is well protected through sensory feedback from abrasive injuries when barefoot. This information combined with previous reports suggests that risk of injury when normally shod individuals perform barefoot locomotion should be low.

Adult↗