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Biomedical subjects

D W Grieve

Publications and source records attributed to D W Grieve.

At least 19 recordsLinked to original sources
PubMed1997

Hydro-resistive measurement of dynamic lifting strength.

A device is described for measuring strength and power outputs of dynamic vertical lifts between heights of 0.4 and 2.2 m. The device is safe, robust, and easily transportable. It consists of a water-filled tube 2 m high and 200 mm internal diameter. The subject pulls vertically on a handle which is connected with flexible wire rope via a series of pulleys to a piston suspended inside the tube. The piston has holes which can be closed with bungs. The drag force is proportional to the square of the velocity. The constant of proportionality can be chosen over a more than 100-fold range and is independent of temperature. Manual force is measured using a strain gauged cantilever over which the rope passes. Rope movement is monitored with a shaft encoder. These devices are sampled synchronously by an interfaced computer. Velocity and power are derived from the measurements of displacement, time and force. The device is highly accurate. Power measurements are not significantly different on two separate days although repetitions on one day show a warming-up effect. This device allows the study of dynamic lifts ranging from slow, high force, quasi-isokinetic lifts to lifts where high velocities and accelerations occur.

Biomechanical Phenomena↗
PubMed1996

The influence of task resistance on the characteristics of maximal one- and two-handed lifting exertions in men and women.

Dynamic lifting strength was assessed at lift velocities ranging from 0 to 1 m.s-1 using a hydrodynamometer in which the viscous resistance to motion could be preset. Nine men and nine women performed one- and two-handed dynamic exertions against low, medium, and high resistances. The subjects were required to lift as forcefully and as fast as possible from a height of 400 mm to just above head height. The instantaneous forces recorded at knee, knuckle, hip, shoulder, elbow, and head heights were compared with those obtained during maximal one- and two-handed isometric lifts performed at the same heights. The position of peak force relative to stature was lower for one-handed lifts (35.9% of stature) than for two-handed lifts (38.4% of stature) (P < 0.005), but was unaffected by lift resistance (P > 0.05) and subject sex (P > 0.05). Lifting forces during two-handed exertions were on average 1.5 times greater than for one-handed exertions (P < 0.0001). However, the difference in the strength of one- and two-handed lifts was highly dependent on hand height (P < 0.0001) and task resistance (P < 0.005), and was greater for the men than for the women (P < 0.001). When static lifting strength was measured at heights relative to stature and normalized by dividing by body weight, there was no significant difference in performance between the men and the women [mean normalized female:male: (f:m) strength ratio = 0.76, P > 0.05]. Under dynamic conditions the sex difference in lifting performance was pronounced (mean normalized f:m strength ratio = 0.68, P < 0.01), especially for power output (mean f:m power.unit body weight-1 ratio = 0.52, P < 0.005). The proportion of generality (r2 x 100) between dynamic and static lifting strength was found to range between 63% and 87%. These data suggest that the dynamic and static tests of lifting strength measured a common, intrinsic ability to produce maximal lifting forces. The finding that sex differences in strength are dependent on whether the exertion is static or dynamic has important implications for biomechanical models of human strength.

Adult↗
PubMed1996

The generation of torque in the horizontal plane at the foot-base during laterally directed manual exertions.

Two experiments were carried out to investigate the mechanisms by which both translational forces and a turning moment in the horizontal plane at the foot-base are transmitted by the lower limb during laterally directed manual exertions. The first used a force plate to measure forces and moments exerted by the feet separately or together in order to investigate the contribution of each foot to the moment. The second examined the role of flexors and extensors of the hip, knee and ankle in the transmission of torque. The results suggest that approximately half of the moment is generated by each foot exerting a translational force at a distance from, and in the opposite direction to, the other. The other half is by each foot exerting an individual torque upon the floor. It is suggested that biomechanical models of asymmetric exertion should take these mechanisms into account.

Biomechanical Phenomena↗
PubMed1992

The measurement and prediction of isometric lifting strength in symmetrical and asymmetrical postures.

Static lifting strengths of nine men and nine women were measured at six heights from just above the floor to just above the head, at two horizontal reaches from the mid-ankles (equal to the elbow to grip and acromium to grip distances), in the sagittal plane and also at 45 degrees and 90 degrees to the right for two-handed exertions and at 45 degrees and 90 degrees to each side for one-handed exertions, making a total of 96 postures. A second and different group of 18 subjects (nine men and nine women) were studied in 20 two-handed and 40 one-handed postures intermediate to those of the first group. A third group of 16 subjects (eight men and eight women), with six drawn from the other groups, were used to determine maximum possible reach (at which lifting strength is zero) at the same heights and planes as those for the first group. When strength was expressed as a fraction of body weight and height and reach were expressed as fractions of stature, predictive equations of static lifting strength were obtained which were gender free. The predictive equations may be used to generate isodyne contours for an individual in any chosen planes. Individuals exist whose strengths are consistently greater or less than the prediction. The possibility of identifying such persons in a process of worker selection is discussed.

Adult↗
PubMed1992

Performance of physical tasks in pregnancy.

Two hundred women in the third trimester of a first pregnancy were interviewed, and 50 of them were interviewed again at 4 months post partum. They were asked whether they experienced greater current difficulty in performing 46 common tasks than they did before pregnancy and were asked to grade their responses. Additional information concerning specific factors affecting each activity, such as discomfort and fatigue, was obtained, together with data concerning socioeconomic status and stress perception. The data were analysed to identify the activities whose performance was most and least affected by pregnancy, indicating that the pregnant condition affects perceived difficulty of performance in many activities. Although some activities are not amenable to ergonomic intervention, the study highlighted some in which equipment design and selection could improve the match between a task and the pregnant.

Environment Design↗
PubMed1992

Short-stepping gait in severe heart failure.

BACKGROUND: Patients with severe chronic heart failure seem to take shorter steps than healthy controls when walking on a treadmill and when walking freely along a corridor. In healthy individuals the pattern of walking affects the oxygen cost of exercise, and so this observation might be relevant to the limitation of exercise in heart failure. METHOD: Length of stride was analysed as stride/stature index in 15 controls, 10 patients with moderate heart failure, 10 patients with severe heart failure, and 10 patients with angina, walking at a constant speed/stature index. RESULTS: The stride/stature index was 0.64 in the controls in patients with New York Heart Association (NYHA) class II heart failure, and in patients with angina. It was 0.49 in patients with NYHA class III heart failure. In the patients with heart failure the stride/stature index correlated with exercise capacity determined as peak oxygen consumption VO2max (R = +0.62, p < 0.005). When healthy controls walked in time to a metronome adjusted to decrease their stride/stature index to approximately that seen in severe heart failure steady-state oxygen consumption increased by a mean of 15%. CONCLUSIONS: The length of stride is reduced in severe heart failure, and when healthy controls adopt this gait the oxygen cost of walking is increased. A short-stepping gait may contribute to the limitation of exercise capacity in heart failure.

Aged↗
PubMed1991

Human strength capabilities during one-handed maximum voluntary exertions in the fore and aft plane.

Maximal static strengths were determined for one-handed exertions in all directions in the fore and aft plane. Data from 12 males and 10 females (mean age 30.7 yrs, standard deviation (SD) = 8.9 yrs, n = 22) were obtained with handle heights of 1.0 and 1.75 m. Twelve of the subjects also performed two-handed exertions at the same handle heights. The ratio of mean strengths of females to that of males ranged from 0.50 to 0.83 (for absolute forces) and from 0.63 to 1.00 for forces normalized to body weight. The ratios of one-handed to two-handed strengths ranged from 0.64 to 1.04. Two-handed strengths commonly exceeded one-handed strengths at the lower handle height, but showed fewer significant strength differences (p less than 0.05) according to direction at 1.75 m. Both female/male and one-handed/two-handed strength ratios were found to be dependent on direction of exertion and handle height. The observed strength dependencies upon number of hands (one or two-handed), direction of exertion, handle height and sex are discussed. The strength data have implications for use in biomechanical models and task analysis.

Adult↗
PubMed1986

Force, speed and power output of the human upper limb during horizontal pulls.

The purpose of the experiment was to examine how force, speed and power output of horizontal pulling with the upper limb was affected by the height of pull. Fourteen seated male subjects made horizontal pulls with maximal effort at eye, shoulder and elbow level from their positions of full reach when the trunk and shoulder girdle were rigidly constrained. Dynamic pulls were performed against a water-filled viscous dynamometer in which the resistance, proportional to the square of the velocity, could be varied. The height of pull had no significant effect on either static or dynamic performance. A force-velocity-position surface is presented which describes the conditions at the handle during the pulls. It confirms the importance of degree of reach upon the dynamic performance, and over a greater range of velocities than has been studied previously. A simple model shows that the similarity of performance at eye, shoulder and elbow heights is remarkable because they occur under very different biomechanical circumstances. The total work done in a complete pull increases with resistance. Peak power output is obtained against the same resistance (50 kg m-1) that was reported for elbow flexion and standing pulls.

Arm↗
PubMed1980

Monitoring gait.

Explore the source record for details and available documents.

Biomechanical Phenomena↗
PubMed1978

The analysis of normal stepping movements as a possible basis for locomotor assessment of the lower limbs.

Sagittal plane rotations of the thigh and shank when leading or trailing during forward or backward and during upward or downward stepping manoeuvres (one step, starting and finishing with erect stance) were recorded by polarized light goniometry in the form of thigh-knee angle diagrams. Angles and limb projections corresponding to key features of the diagrams were measured for 21 normal subjects and at three step heights. Correlations of the measurements with the height of step relative to stature were examined and predicted norms presented for a step equal to 10% of stature. The eight possible movements on a given step consist of four conjugate pairs; the members of a pair have reversed time-sequences and gravity assists one while opposing the other. The similarities of the conjugate manoeuvres were analysed statistically. A test of locomotor function is suggested on the premise that disturbances of function would be revealed by within-subject comparisons of conjugate manoeuvres. The suitability of 10% step tests for clinical use and the problems of selecting data of manageable proportions are discussed.

Adolescent↗