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Biomedical subjects

D Liddell

Publications and source records attributed to D Liddell.

16 recordsLinked to original sources
PubMed2004

Acute effects of static stretching on hip flexor and quadriceps flexibility, range of motion and foot speed in kicking a football.

The purpose of this research was to determine the effect of static stretching in a warm-up on hip flexor and quadriceps flexibility as measured by a modified Thomas test and on range of motion (ROM) of the leg and foot speed at impact in kicking a football with maximum effort. Sixteen Australian Rules (AR) footballers performed two different warm-ups on different days. One warm-up involved five minutes of sub-maximum running followed by seven practice kicks, while the other also included 4.5 minutes static stretching of the hip flexors and quadriceps after the running. A modified Thomas test was conduced before and after each warm-up. Players performed maximum effort drop punt kicks into a net while being videotaped to determine the ROM of the kicking leg and foot speed at impact with the ball. There were no significant changes in flexibility (p > 0.05) as a result of either warm-up and there were no significant differences between the warm-ups in the kicking variables (p > 0.05). It was concluded that the Thomas test may not have been sensitive to possible acute changes in flexibility from the warm-ups, and that stretching had no influence on kicking ROM or foot speed, possibly because of the complexity of the kicking skill.

Adolescent↗
PubMed1994

Cancer mortality in chrysotile mining and milling: exposure-response.

New material was presented from pending publications arising from the follow-up to 1988 of the Quebec cohort of over 10,000 chrysotile miners and millers born 1891-1920. In reviewing these and previous findings, the following conclusions were drawn; they are supported, insofar as this is possible, by the only other relevant information, that from Balangero, in Northern Italy. There is strong evidence that the risk of lung cancer as a result of exposure to chrysotile at concentrations of less than 15 million particles per cubic foot is vanishingly small. At higher concentrations, the relative risk of lung cancer is elevated, but less so in smokers of 20 or more cigarettes a day than in others. The magnitude of this risk cannot be evaluated with any certainty, but this is unimportant as these higher concentrations (above about 50 f ml-1) are well outside the range of experience nowadays. There is no evidence that the risk of laryngeal cancer or of stomach cancer are adversely affected by exposure to chrysotile. Nor is there evidence of increased risks of other abdominal malignancies or of kidney cancer among chrysotile miners and millers. The risk of mesothelioma in chrysotile miners and millers is very low compared with the risks in populations exposed to amphiboles or to mixtures of fibres including even small proportions of amphiboles.

Asbestos, Serpentine↗
PubMed1985

Fitting relationships between exposure and standardized mortality ratios.

Practical methods are described for formal fitting of simple (linear) relationships between exposures in several subgroups and standardized mortality (or morbidity) ratios (SMRs) for these groups, whether derived from a cohort study by the person-years method or otherwise. The observed events are assumed to have Poisson variation about the fitted relationships. Procedures are outlined for obtaining parameter estimates by iterative weighted least squares regression, which is not only equivalent to, but also the simplest form of maximum likelihood estimation. A test of fit is available in a chi 2 statistic for deviations of observed data from "fitted" values. A further test allows one to examine whether the SMR at zero exposure is different from unity. The concept of relative slopes is discussed, and methods are given for obtaining estimates and confidence intervals. Generalizations to more than one exposure, and to quadratic and other relationships, are explained. Steps for computing the basic fits are detailed, and instructions for adapting packaged computer programs given. Illustrations are provided from data of lung cancer SMRs in relation to exposure to asbestos and to smoking.

Asbestosis↗
PubMed1983

Individual susceptibility to inhaled particles. A methodological essay.

Many workers severely exposed to inhaled particles have remained unaffected--what has protected them? Some workers have been affected despite mild exposure--what has rendered them vulnerable? There has been little progress in answering even the first question, and there can be no guarantee that factors rendering the lightly exposed vulnerable are the converse of those protecting the heavily exposed. An answer to the second question would be useful, say, for screening. But it requires study at the low end of the exposure scale, and there are many variables, probably intricately related, to be taken into account. A case/referent design might seem an obvious approach, but in its classical form it incurs essential and perhaps insurmountable difficulties. A longitudinal epidemiologic study would have to be very large, very complex, and very long in duration. Animal experiments also would have to be large and complex, probably embracing most of the animals' life span, but even so they could not take all relevant variables into account. It is recognized that the present paper has emphasized many difficulties and may thus appear negative in approach. Furthermore, although a compromise epidemiologic design is put forward, it is speculative.

Air Pollutants↗
PubMed1979

The initiation of gait.

The initiation of gait was studied utilizing electromyography, force-plate data, measurements of walking velocities, and ranges of motion of joints, all of which demonstrated that gait is initiated by the body becoming unbalanced in such a way as to permit a subject to pick one foot the ground in order to take the first step. The subsequent transition of the body to the steady gait pattern occurs rapidly over a period of appproximately three steps. This transition involves rapid changes in the measured forces and activities of the muscles of the lower extremity and the motion of the joints reflects these changes.

Adult↗
PubMed1975

Radiological changes over 20 years in relation to chrysotile exposure in Quebec.

Radiological changes in 267 male Quebec chrysotile mine and mill workers, each with five chest films spanning an average of 20 years, were related to age, smoking habit, mining area, duration of employment and average dust concentration before and between films. (1) Abnormality in the earliest film was related mainly to the time since first employment. (2) In 45 (30%) of the 150 men completely normal at earliest film, some radiological abnormality developed during the period of observation: incidence was weakly related to age; in Asbestos, the risk of developing small opacities was lower in smokers than in non-smokers. (3) There was an irregular pattern of correlation, more evident in Thetford Mines than in Asbestos, between radiological progression and various stimulus variables. That associations between radiological responses and measures of asbestos exposure were, as always, weak, despite powerful methodology, indicates that effects are obscured by other factors (including susceptibility) uncorrelated with exposure.

Adult↗