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Biomedical subjects

J G Hay

Publications and source records attributed to J G Hay.

51 records · Page 3Linked to original sources
PubMed1983

Premedication for fibreoptic bronchoscopy.

A randomised, double-blind trial of atropine, atropine plus papaveretum, and atropine plus diazepam given intramuscularly as premedication for fibreoptic bronchoscopy in 60 patients showed no difference between the three regimens as assessed by bronchoscopist or patient. Bronchoscopists frequently attributed a sedative action to atropine alone and their assessment of tolerance and sedation was more optimistic than that of the patients. In a second study comparing intravenous diazepam (10 mg) with saline, after prior intramuscular atropine (0.6 mg), both the bronchoscopists and the patients noted a significant sedative effect of diazepam, and coughing was reduced by diazepam.

Atropine↗
PubMed1983

Biomechanical considerations in the modeling of muscle function.

The instantaneous functional role of a voluntary muscle in the neighborhood of a joint is often described in clinical terms (e.g. flexor; abductor; external rotator; agonist; contracting concentrically and isokinetically) that seen sufficiently explicit and clear in certain simple situations, but have not yet been carefully defined in precise biomechanical terminology for the general case. In order to describe the functional role of a voluntary muscle as its acts to change and/or maintain the configuration of a joint, it is necessary to make certain modeling assumptions. These include modeling the joint, modeling the muscle force line of action in the joint neighborhood, and establishing the location and orientation of the three joint axes for all possible joint configurations. Modeling the joint as a point leads to simple and sensible definitions which are consistent with clinical practice. The straight line model is most conveniently used to establish the muscle force line of action. A RHO coordinate system embedded in the distal joint segment with origin at the joint center point, and with intersecting axes coincident with the F/E, A/A and I/XR axes when the joint is in the anatomical position, is the joint coordinate system of choice to describe the turning effects of the muscle about the joint. Sensible and simple biomechanical definitions for clinical terms describing muscular contractions (i.e. concentric; eccentric; isometric; isokinetic; isotonic) were presented and appear to be relatively uncontroversial. Alternative biomechanical definitions for agonistic and antagonistic muscular activity were also presented, as were arguments for choosing a simple definition based on using the joint resultant moment as the criterion measure relative to which the individual muscle's moment about J should be compared. Biomechanical definitions for determining when a muscle functions as a joint flexor or extensor, abductor or adductor, and internal or external rotator were also presented. These definitions were based on the classical concept where the muscle's instantaneous turning effect is determined by its moment about the joint center. The algebraic signs and relative magnitudes of the components of the muscle's moment about J were used to determine not only the functional behavior of the muscle (e.g. flexor vs. extensor), but also the relative contributions of the muscle to producing rotations about the three joint axes through J. A detailed critique of the restricted functional classification scheme proposed by Molbech and Carlsöö was also presented.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗
PubMed1982

Closed loop problems in biomechanics. Part I--a classification system.

Biomechanics researchers have relied heavily on the inverse dynamics approach for calculating the forces and torques at human joints. However, implicit in this approach is the assumption that there are sufficient independent equations of motion to uniquely determine these unknown kinetics. There exists a class of problems, commonly referred to as closed loop problems, when there are insufficient equations and indeterminacy arises. The purposes of the present paper are (1) to develop a general classification system of closed loop problems for whole body movements; and (2) to identify the minimum number of force transducing devices necessary to uniquely determine joint kinetics for these problems. The classification system is based on the human subject's interaction with his environment and with himself. Two criteria are considered: first, the number of the subject's extremities in contact with fixed external reference systems, and second, the number of closed loops formed by those extremities not in contact with fixed external systems. Different combinations of these two criteria are examined and grouped into five cases according to the degree to which the equations of motion are over-determined, determined, or under-determined. Examples are given to illustrate the concepts. It is felt that the use of this system should aid in the understanding of joint force and torque calculations, especially with regard to the under-determined cases.

Biomechanical Phenomena↗
PubMed1982

Closed loop problems in biomechanics. Part II--an optimization approach.

A closed loop problem in biomechanics may be defined as a problem in which there are one or more closed loops formed by the human body in contact with itself or with an external system. Under certain conditions the problem is indeterminate--the unknown forces and torques outnumber the equations. Force transducing devices, which would help solve this problem, have serious drawbacks, and existing methods are inaccurate and non-general. The purposes of the present paper are (1) to develop a general procedure for solving closed loop problems; (2) to illustrate the application of the procedure; and (3) to examine the validity of the procedure. A mathematical optimization approach is applied to the solution of three different closed loop problems--walking up stairs, vertical jumping and cartwheeling. The following conclusions are drawn: (1) the method described is reasonably successful for predicting horizontal and vertical reaction forces at the distal segments although problems exist for predicting the points of application of these forces; (2) the results provide some support for the notion that the human neuromuscular mechanism attempts to minimize the joint torques and thus, to a certain degree, the amount of muscular effort; (3) in the validation procedure it is desirable to have a force device for each of the distal segments in contact with a fixed external system; and (4) the method is sufficiently general to be applied to all classes of closed loop problems.

Biomechanical Phenomena↗
PubMed1982

Selection of body segment parameters by optimization methods.

The selection of body segment parameters (BSPs) is a difficult yet essential task in many biomechanical studies. The methods used to date-cadaver, reaction board, mathematical modeling, gamma scanning, and kinematics-all have a number of drawbacks. The purpose of the present paper is to present an alternative method, based on kinematic data and optimization theory, for selecting BSPs. The design variables are the BSPs and the objective function to be minimized is based on the difference between calculated and measured distal extremity kinetics, while the equality constraints are based on Newtonian principles as well as bilateral symmetry of the BSPs. Three different activities are used to generate "optimal" sets of BSPs and these values are different, but not markedly so, from cadaver values. Further detailed investigation appears warranted.

Anthropometry↗
PubMed1979

Forces exerted during exercises on the uneven bars.

The purposes of this study were (1) to develop a technique to measure the force exerted on uneven bars during a gymnast's performance, and (2) to determine the magnitudes of the maximum forces exerted on the bars during normal use. Strain gages, a UV recorder, and motion-picture cameras were used to record the forces exerted against the bars and the motions with which they were associated. Three college gymnasts were used as subjects. Each performed several repetitions of an exercise sequence judged to result in the maximum loading of the bars she might produce under normal conditions. The maximum forces recorded were 3500 N (low bar) and 2140 N (high bar). These values were recorded during a sharp impact between the subject's thighs and the bar during the passage of the subject beneath the bar in a giant swing, respectively. Making due allowance for possible measurement error and for the estimated effects of the bars being used by gymnasts of greater mass than those in this study, it was concluded that bars should be designed to withstand repeated loads of at least 4205 N.

Adult↗
PubMed1979

Basketball: the mechanics of hanging in the air.

A theoretical technique to permit basketball players to "hang in the air" prior to the release of a shot is presented. The purposes of this study were (a) to determine whether skilled players used such a technique when delaying the release of their shot and (b) to determine whether such players could be readily taught to "hang in the air" using this technique. Six current members of the Iowa basketball team were filmed, executing jump-shots. During each trial the players "faked" or "pumped" to delay the release of the shot. Qualitative analysis of the film revealed that none of the players demonstrated the coordinated limb movement involved in the theoretical technique. Prior to a second filming session, two former Iowa varsity players practiced a predetermined sequence of body movements. Each player performed eight trials and the results were analyzed quantitatively. The vertical displacements and the vertical velocities of the center of gravity, vertex of the head and mid-point of the hips were plotted against time. Results clearly indicated that the players were able to maintain the same vertical position of the head and hips (and thus, the trunk) for about 0.2 sec at or near the peak of the jump. It was concluded that a skilled player could be taught, in a relatively short period of time, to "hang in the air" using the techniques presented.

Arm↗