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Biomedical subjects

A M Wing

Publications and source records attributed to A M Wing.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of surface texture and grip force on the discrimination of hand-held loads.

In this paper, we report the results from two experiments in which subjects were required to discriminate horizontal load forces applied to a manipulandum held with a precision grip. The roughness (and hence friction) of the grip surfaces and required grip force were manipulated. In the first experiment, subjects were instructed to judge the load while maintaining hand position and not letting the manipulandum slip. It was found that performance was influenced by surface texture; a given load was judged to be greater when the surface texture was smooth than when it was rough. This result is consistent with a previous study based on lifting objects and indicates that the effect of surface texture applies to loads in general and not just to gravitational loads (i.e., weight). To test whether the load acting on a smooth object is judged to be greater because the grip force required to prevent it from slipping is larger, a second experiment was carried out. Subjects used a visual feedback display to maintain the same grip force for smooth and rough manipulandum surfaces. In this case, there was no effect of surface texture on load perception. These results provide evidence that perceived load depends on the grip force used to resist the load. The implications of these results in terms of central and peripheral factors underlying load discrimination are considered.

Adolescent↗
PubMed1996

Age differences in postural stability are increased by additional cognitive demands.

We report an investigation of postural stability in two groups of volunteers (mean ages of 57 and 77). Participants were required to stand on a force platform while performing five cognitive tasks: (1) random digit generation, (2) Brooks' spatial memory, (3) backward digit recall, (4) silently counting from 1-100, and (5) counting backward in threes (aloud). There was also a control condition in which there was no cognitive task. Postural stability was adversely affected by age in all conditions. Moreover, the difference between the two age groups was significantly greater when performing tasks 2 and 3, in comparison with the age difference in the control condition. Regression analyses revealed that the effect of age on postural stability while performing these particular tasks remained significant even after the following measures were included in the regression: postural stability in the control condition, cognitive performance, intelligence, and speed. We suggest that age differences in postural stability are increased by cognitive tasks requiring use of the visuo-spatial sketchpad component of working memory.

Age Factors↗
PubMed1995

The stability of precision grip forces during cyclic arm movements with a hand-held load.

In this paper we examine the coordination of grip force and load during brisk cyclic arm movements with a hand-held object under a range of conditions. We show that, regardless of the surface texture of the object or movement frequency, grip force is modulated in parallel with load. Thus, the tight coupling between grip force and load observed in short-duration tasks such as lifting or point-to-point movements is also seen in longer-duration cyclic movements. Moreover, the gain of the relation between grip force and load remains essentially constant over time. Across conditions, we find a dissociation between the gain of the relation between grip force and load and the grip force offset. With a more slippery surface texture both the gain and offset increase, whereas increases in frequency lead to an increase in the offset but a decrease in gain. This suggests that these two parameters are under independent high-level control. We also observe that when subjects were instructed to maintain a high-baseline grip force during the movement, grip force was still modulated with load even though an increase in grip was not necessary to prevent slip. This suggests that there is an obligatory coupling between grip force and load. This coupling might be subserved by low-level mechanisms not under high-level control.

Adult↗
PubMed1995

The coordination and consistency of rowers in a racing eight.

Recordings of force developed simultaneously by four rowers in a good club-standard eight over a 20-min training run were analysed in terms of mean and variability. The average force-time profiles showed small but distinctive differences between rowers that were maintained as force declined through the run. The variability was examined further in terms of time-series of features extracted from single force-time profiles, including the peak force, duration and interstroke interval. There were consistent positive correlations between rowers in interstroke intervals even after removal of low-periodicity components (trends) in the time-series.

Adult↗
PubMed1995

Effects of surface texture on weight perception when lifting objects with a precision grip.

In this paper, we show that, when lifting an object using a precision grip with the distal pads of the thumb and index finger at its sides, the perceived weight depends on the object's surface texture. The smoother the surface texture, the greater the perceived weight. We suggest that a smoother object is judged to be heavier because the grip force, normal to the surface, required to prevent it from slipping is greater. The possibility of there being an influence of surface texture per se is excluded by a second experiment that employed a variant of the precision grip in which the thumb supports the weight of the object from underneath. With the grip oriented in this way, there is no need to match grip force to surface texture and, under these conditions, there is no effect of surface texture on weight perception. In the first two experiments, the test and comparison weights were lifted successively by the same hand. In a third experiment, the effect of surface texture was replicated for sequential lifts made with separate hands. Thus, the effect is not restricted to comparisons made with the same hand.

Adolescent↗
PubMed1994

Levels of cadmium, zinc and copper in renal cell carcinoma and normal kidney.

Levels (microgram/g dry weight) of cadmium (Cd), zinc (Zn) and copper (Cu) were determined in kidneys with renal cell carcinoma from 20 male and 11 female patients. Autopsied kidneys from nine males and eight females who had died of nonmalignant diseases were used as controls. The mean levels in cortex of Cd was in cases 103.2 and in controls 79.9 (not significantly different). For non-smoking cases, mean level of Cd in cortex was somewhat lower than in the controls. No significant differences were found between cases and controls for Cd levels in the medulla. Zn in cortex was significantly lower in the cases aged > or = 69 years (mean 182.0) than in the corresponding controls (mean 237.6). Zn in medulla was significantly lower in all cases (mean 103.5) than in controls (mean 162.2). The mean level of Cu in the medulla in cases was 10.7 and in controls 13.0 (P = 0.05). No differences were found for Cu levels in cortex.

Aged↗
PubMed1994

Enhanced intestinal nickel absorption in iron-deficient rats.

The absorption of nickel was studied in isolated perfused jejunal and ileal segments of iron-deficient and iron-sufficient rats. The uptake of nickel in tissues of iron-deficient and iron-sufficient rats given a low oral nickel-dose was also examined. The results showed enhanced nickel absorption in vitro and in vivo in iron-deficient rats. In the in vitro perfusions, increased absorption was observed both in jejunum and ileum. The enhancement was very prominent in jejunum and the nickel concentration in the jejunal absorbate of iron-deficient rats even exceeded the nickel concentration in the perfusate. This indicates that nickel is absorbed actively in the jejunum of iron-deficient animals. Twenty-four hr after an oral dose of nickel the uptake of the metal in various tissues was 1.5-2.5 times higher in iron-deficient rats compared to iron-sufficient rats. Our data indicate that nickel is absorbed at least in part by the active transfer system for iron in intestinal mucosal cells.

Animals↗
PubMed1993

Coupling of grip force and load force during arm movements with grasped objects.

Numerous studies have investigated the kinematics of arm movements; others have examined grip forces during static holding of objects. However, the coordination of grip force and arm movement when moving grasped objects has not been documented. We show that grip force is finely modulated in phase with load force during movements with grasped objects in which load force varies with acceleration. A tight coupling between grip and load force is seen in point-to-point and cyclic movements of varying rate and direction. We conclude that in transporting an object, the programming of grip force is part and parcel of the process of planning the arm movement.

Arm↗
PubMed1993

Modulation of grip force with load force during point-to-point arm movements.

In this paper, we examine grip forces and load forces during point-to-point arm movements with objects grasped with a precision grip. We demonstrate that grip force is finely modulated with load force. Variations in load force arise from inertial forces related to movement; grip force rises as the load force increases and falls as load force decreases. The same finding is observed in vertical and horizontal movements performed at various rates. In vertical movements, maximum grip force coincides in time with maximum load force. The maxima occur early in upward and later in downward movements. In horizontal movements, where peaks in load force are observed during both the acceleratory and deceleratory phases, grip force rises at the beginning of the movement and remains high until the end. The results suggest that when moving an object with the hand the programming of grip force is an integral part of the planning process.

Adolescent↗
PubMed1993

The effects of whole wheat, wheat bran and zinc in the diet on the absorption and accumulation of cadmium in rats.

The purpose of the present study was to determine if the inclusion of whole-grain wheat or wheat bran in the diet or the addition of Zn to the diet affects the absorption and accumulation of Cd. Five groups of six rats each were fed deionized water and one of five diets composed of one part basic diet and one part wheat crispbread for 6 weeks. The accumulation of Cd in the liver and kidneys was measured using atomic absorption spectrometry and estimated by measuring the absorption and retention of 109Cd from a single meal after 3 weeks on the diets. The fractional accumulation of Cd in the liver and kidneys was lower in rats fed on whole-wheat and bran diets than in those fed on wheat-endosperm diets. As adding Zn or Cd to endosperm diets to approximate the bran and whole-wheat diet levels had no effect on the fractional Cd absorption, the reduced absorption from the whole-wheat and bran diets is probably not due to their higher Zn and Cd concentrations but may be due to their higher fibre or phytate concentrations. The amount of Cd accumulated in the liver and kidneys of the rats fed on whole-wheat and bran diets was higher than that in rats fed on the endosperm diet. Thus, the reduction in the fractional Cd accumulation from the whole-wheat and bran diets is not sufficient to compensate for their higher Cd concentrations.

Animals↗
PubMed1993

Balance evaluation in hemiparetic stroke patients using lateral forces applied to the hip.

A technique for assessing balance that involves applying predictable controlled forces to the hips is described. Impairments in hemiparetic stroke patients' balance were documented by comparing their hip movements during and after a push with those of control subjects of similar age. Stroke patients swayed further and took longer to stabilize hip position than did the control subjects. The disturbance to stroke patients' balance caused by the termination of lateral force caused them more difficulty than did the onset of the force. Differences between stroke patients' involved and noninvolved sides were more pronounced on release from a push than at its onset. The implications of the findings for the assessment and treatment of balance after stroke are discussed.

Aged↗
PubMed1991

Remote responses to perturbation in human prehension.

This experiment investigated how the control of hand transport and of hand aperture are coordinated in reaching and grasping movements. An electric actuator attached to the subject's right arm delivered mechanical perturbations randomly during a quarter of the experimental trials. A remote, compensatory adjustment of hand aperture followed the immediate, mechanical affects of the perturbation of hand transport. The invariant spatial and temporal characteristics of the response suggest how the two systems may be coordinated during prehension.

Adult↗
PubMed1991

A recruitment theory of force-time relations in the production of brief force pulses: the parallel force unit model.

A theory, the parallel force unit model, is advanced in which the buildup and decline of force in rapid responses of short duration are assumed to reflect variability in timing of several parallel force units. Response force is conceived of as being a summation of a large number of force units, each acting independently of one another. Force is controlled by either the number of recruited force units or the duration each unit contributes its force. Several predictions are derived on the basis of this theory and are shown to be in qualitative agreement with empirical findings about both the mean and variability of brief force impulses. The model also has consequences for the temporal properties of a response. For example, under certain circumstances, it predicts a reciprocal relation between reaction time and response force. Although the theory is proposed as a psychological account, relations between the assumptions and basic principles in neurophysiology are considered. Possible future applications and generalizations of the theory are discussed.

Animals↗
PubMed1991

A new challenge--robotics in the rehabilitation of the neurologically motor impaired.

Rehabilitation robotics is a research area, originating in engineering, that has emerged in the last decade. Its broad aim is to use robot technology to assist people with movement dysfunction. The neurologically impaired population might gain considerably from the provision of robots as "assistants" or "therapy aides," but the interface with the machine must match both the physical and intellectual abilities of the user. We therefore consider a multidisciplinary approach, encompassing both behavioral and engineering perspectives, to be essential in achieving this aim. However, to date, published reports have been largely restricted to engineering journals or conference reports, and relatively little has appeared in the therapy literature. This article seeks to introduce physical therapists to robotics, describe possible applications to the rehabilitation of neurologically impaired patients, and suggest issues deserving further investigation.

Evaluation Studies as Topic↗
PubMed1990

Assessing and reporting the accuracy of position measurements made with optical tracking systems.

The use of optical tracking systems to record human movement is now widespread. Although such systems are convenient and potentially very accurate, they must be used carefully to ensure good data. This paper describes the procedures of calibration and reconstruction of position data in cartesian coordinates and suggests steps to maximize their accuracy. Procedures are proposed for characterizing the accuracy of measurement throughout the experimental workspace, and open discussion of the issue by the research community is invited.

Journal Article↗
PubMed1990

Recovery of elbow function in voluntary positioning of the hand following hemiplegia due to stroke.

Elbow movement during voluntary positioning of the hand (with the arm supported against gravity) is described in a longitudinal study of five patients recovering from hemiplegia due to stroke. Over a twelve month period, four of the patients improved their speed of movement, three exhibiting slightly better recovery of elbow extension, one of flexion. In some instances co-contraction of the elbow agonist and antagonist (measured just before the onset of movement) decreased with time after stroke. The effects of contrasting movements at the shoulder on elbow movement were also studied. Estimates of recovery were generally similar whether patients kept the shoulder still or made movements that were synergic or counter-synergic to those of the elbow.

Adult↗