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Biomedical subjects

D A Brodie

Publications and source records attributed to D A Brodie.

At least 19 recordsLinked to original sources
PubMed1992

Effect of very low calorie diet on body composition and exercise response in sedentary women.

The effect of very low calorie diet (VLCD) on fat-free mass (FFM) and physiological response to exercise is a topic of current interest. Ten moderately obese women (aged 23-57 years) received VLCD (1695 kJ.day-1) for 6 weeks. FFM, estimated by four conventional techniques, and heart rate (fc), blood lactate (la(b)), mean arterial pressure (MAP), respiratory exchange ratio (R) and rating of perceived exertion (RPE) were measured during a submaximal cycle ergometry test 1 week before, in the 2nd and 6th week, and 1 week after VLCD treatment. Strength and muscular endurance of the quadriceps and hamstrings were tested by isokinetic dynamometry. The 11.5-kg reduction in body mass was approximately 63% fat and 37% FFM. The latter was attributed largely to the loss of water associated with glycogen. Whilst exercise fc increased by 9-14 beats.min-1 (P < 0.01), there were substantial decreases (P < 0.01) in submaximal MAP (1.07-1.73 kPa), la(b) (0.75-1.00 mmol.l-1 and R (0.07-0.09) during VLCD. R and fc returned to normal levels after VLCD. Gross strength decreased (P < 0.01) by 9 and 13% at 1.05 rad.s-1 and 3.14 rad.s-1, respectively. Strength expressed relative to body mass (Nm.kg-1) increased (P < 0.01) at the lower contraction velocity, but there was no change at the faster velocity. Muscular endurance also decreased (P < 0.01) by 62 and 82% for the hamstrings and quadriceps, respectively. We concluded that the strength decrease was a natural adaptation to the reduction in body mass as the ratio of strength to FFM was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Body fat estimations by electrical impedance and infra-red interactance.

The purpose of this study was to examine body fat estimation using three methods of electrical impedance (the BIA-103 Body Composition Analyser--RJL Systems, Detroit; the BMR 2000 Body Composition Analyzer--Berkeley Medical Research, San Leandro; the BC300 Body Composition Analyzer--Spacelabs, Dallas) and an infra-red interactance method (Futrex 5000 Analyzer--Futrex Inc. Gaithersburg) as an alternative to hydrodensitometry. Five different groups were examined using at least one of the electrical systems and in all cases utilising hydrodensitometry as the criterion method. The results produced highly significant correlations between all methods, but caution is recommended due to the limited common variance in some cases. The individual electrical methods differed from hydrodensitometry by a maximum of 1.1% in obese women, by 21.6% in athletic adults, by 6.2% in the slightly obese group, by 8.1% in normal women and by 56.0% in normal children. Significant mean differences between one of the impedance methods and hydrodensitometry were only noted in two of the groups tested. This suggests, allowing for the limitations of hydrodensitometry itself, that the other three electrical methods appear to be reasonably valid alternatives to underwater weighing, especially for field work of an epidemiological nature.

Adipose Tissue↗
PubMed1991

A comparison of selected health-related data from surveys of a general population and a sporting population.

This paper presents a comparison of health-related data from two surveys of British adults. Respondents from one survey formed a representative sample of the British population, whilst respondents from the other were characterised by their participation in sport. Statistical analysis revealed that sports participants had significantly lower body mass index values, lower blood pressures and lower resting pulse rates (P less than 0.05). In addition, sports participants possessed better self-perceived health and perceived themselves overall to be more active than members of the general population. When controls were introduced for gender and age, many of these differences remained, particularly among females. It is concluded that despite the cross-sectional nature of these data, evidence is provided that supports the health-promoting case for sport.

Adolescent↗
PubMed1991

Leisure-time physical activity as an estimate of physical fitness: a validation study.

This paper describes a new interview questionnaire for the assessment of leisure-time physical activity (LTPA), and its validation as an alternative estimate of physical fitness. British subjects (77 males, 41 females) provided details of their LTPA over a period of a "typical" 2 weeks, enabling the estimation of the energy expended. Physical fitness was assessed with a battery of measures, the optimal single measure being sub-maximal physical work capacity (PWC). The questionnaire showed LTPA to be stable following test-retest administration (r = 0.86; p less than 0.0001) for total LTPA energy expenditure. Total LTPA was found to be significantly related to PWC (r = 0.48, p less than 0.0001), as were very hard (r = 0.55; p less than 0.0001) and hard LTPA (r = 0.38; p less than 0.0001). Multiple regression analysis with PWC as the dependent variable yielded a multiple correlation of r = 0.87, with significant contributions from very hard and hard LTPA. It is concluded that whilst this questionnaire is both reliable and a valid estimate of physical fitness amongst a population consistent in their leisure-time physical activities, there is scope for its further use within larger populations, allowing for an analysis of the effects of age and gender on the associations so far observed.

Adolescent↗
PubMed1991

Effect of changes of water and electrolytes on the validity of conventional methods of measuring fat-free mass.

Fat-free mass was measured by hydrodensitometry, electrical impedance and total body potassium before and after water and electrolyte loss induced by (a) the administration of the diuretic frusemide, and (b) sweat loss. All methods of measuring fat-free mass were shown by pilot experiments to have procedural reliability. The diuretic caused a reduction in apparent fat-free mass of 2.63 kg by the impedance method, of 2.33 kg by hydrodensitometry and of 1.8 kg by total body potassium. Water and electrolyte loss from sweating caused a fat-free loss of 2.3 kg, 2.7 kg and 1.3 kg by the same three procedures. Urinary potassium accounted for about one fifth of the observed 40K fat-free mass loss. Each method was thus clearly sensitive to the induced water loss. These data suggest that in evaluating the composition of weight loss, existing methods of measuring body composition do not distinguish between water and other more critical components of fat-free mass. It is thus essential that stable hydration levels are established for any longitudinal comparison of weight loss by these methods.

Adipose Tissue↗
PubMed1990

Self-perceived health among sports participants and non-sports participants.

This paper examines and compares the self-perceived health (SPH) of a sample of sports participants (n = 1385) and a matched sample of non-participants (n = 292). Ratings of health were generally found to be favourable among both samples, but a non-parametric analysis of their distributions revealed that the SPH of sports participants was significantly (P less than 0.0001) better than that of the non-participants. SPH improved with age among both samples, but above the age of 34, the non-participants' perceived health ceased to be inferior to that of participants. Controlling for age and gender revealed no difference in SPH above 24 years among males and 34 years among females. SPH was related to a variety of additional health-related factors. Multiple regression analysis was used to identify the predictors of SPH for both samples, and highlighted marked differences between them in the type and number of contributory factors. It is suggested that participation in active sports may enhance health awareness, especially among the young, and that future studies of this kind among sports populations should take account of the levels of commitment (frequency, duration and intensity) to sport.

Activities of Daily Living↗
PubMed1990

The assessment of physical activity by leisure-time physical activity questionnaires.

The assessment of physical activity by questionnaire is currently the most popular and practical method of quantifying physical activity levels. Many questionnaires, past and present, have considered overall or habitual physical activity, which includes occupational (or nonleisure) activity. Others have focused specifically on leisure-time physical activity (LTPA) owing to the recognition of its dominating contribution to the total physical activity of developed populations. This review covers questionnaires that wholly or in part attend to LTPA levels. Typically, self-complete or interviewer-administered questionnaires record information on the types, frequency and duration of activities performed over a particular period of time. Activity-specific energy cost values, expressed in metabolic equivalents (METS) or kilocalories, are then commonly used to estimate the total energy expenditure from all activities and/or categories of activities. The validation of LTPA questionnaires has had to rely upon indirect methods, such as the assessment of cardiorespiratory fitness, body composition and activity diaries. The reporting of the reliability of questionnaires has frequently been ignored, although in cases where it has been reported, doubt exists as to whether the consistency of the questionnaire or the consistency of subjects' physical activity habits were being examined. LTPA questionnaires first appeared in the literature in the mid-1960s for use among specific, mainly middle-aged male population groups. Though they varied in their modes of scoring, periods of activity recall, and overall complexity, associations were universally observed between physical activity levels and chronic health conditions. However, it became apparent that different questionnaires did not yield the same results. In 1978, a questionnaire to assess only LTPA, the Minnesota LTPA Questionnaire, was published and despite its substantial limitations, has since established itself as the most popular option available. In recent years, shorter and simpler alternatives have been advocated, though most have yet to be adequately scrutinised. Associations have been found between LTPA and fitness levels, prompting the use of LTPA questionnaires in large-scale fitness surveys of both adults and children. Although LTPA has continued to be estimated in terms of energy expenditure, little attempt has been made to extend existing knowledge on the energy cost of physical activities. Existing values do not accommodate for individual intensities and inter-population activity variations. Consequently, standardised questionnaires are not yet viable. There exists considerable scope for further work with LTPA questionnaires, especially since the association between coronary heart disease and physical activity is now well recognised. Efforts ought to be directed at wider social groups for whom leisure-time activity may have distinct implications.

Humans↗
PubMed1989

Reliability measures in distorting body-image.

This study is the first to make a direct comparison between the distorting mirror and the distorting videocamera with the same group of nonclinical subjects. It also establishes the internal consistency, the test-retest reliability and the convergent validity of both techniques. Analysis indicates, as with other studies, that perceived image is consistently over-estimated and ideal image is consistently under-estimated by both techniques. With the distorting mirror, the frontal orientation is repeatable over four days and with the video the profile is the more reliable orientation. A comparison between profile and frontal orientations on any single test occasion (internal consistency) indicates that the results correlate well so either orientation is acceptable for experimental purposes. The extent to which both techniques were measuring the same aspect (convergent validity) was more marked for the ideal image. A researcher using the distorting mirror can be confident that the ideal image is reliable over time using either orientation but that the perceived image requires a frontal orientation. The frontal or profile orientation is acceptable for the ideal image using the distorting video, but the profile orientation is advisable if one wishes a reliable perceived image. The researcher should also be cautious in assuming that both techniques are measuring an identical body-image construct.

Anorexia Nervosa↗
PubMed1989

Isokinetic dynamometry. Applications and limitations.

Isokinetic contraction is the muscular contraction that accompanies constant velocity limb movements around a joint. The velocity of movement is maintained constant by a special dynamometer. The resistance of the dynamometer is equal to the muscular forces applied throughout the range of movement. This method allows the measurement of the muscular forces in dynamic conditions and provides optimal loading of the muscles. However, during movements in the vertical plane, the torque registered by the dynamometer is the resultant torque produced by the muscular and gravitational forces. The error depends on the angular position and the torque potential of the tested muscle group. Several methods have been developed for the correction of gravitational errors in isokinetic data. The torque output also contains artefacts that are associated with the inertial forces during acceleration and deceleration periods before the development of the constant preset angular velocity. For an accurate assessment of muscle function, only constant velocity data should be analysed. The most frequently used isokinetic parameters are the maximum torque and the angular position where it was recorded, the torque output at different angular velocities of movement, the torque ratio of reciprocal muscle groups and the torque output during repeated contractions. The unique features of isokinetic dynamometry are optimal loading of the muscles in dynamic conditions and constant preselected velocity of movement. These features provide safety in the rehabilitation of patients with muscular and ligamentous injuries. Isokinetic dynamometry has also been used for the training of various muscle groups in order to improve the muscular performance in dynamic conditions. The movement velocity of different activities can be simulated during training in order to improve the training effect. Data acquisition and analysis have been improved by using computer systems interfaced to isokinetic dynamometers. Recently developed computer systems provide correction for gravitational and inertial errors, accurate computation of isokinetic parameters and real-time display of the torque output.

Biomechanical Phenomena↗
PubMed1988

Sports participation and health status: a preliminary analysis.

This paper presents fresh evidence which examines health in relation to age, sex, socio-economic status, sport type and frequency amongst indoor sports participants. The evidence is from 4441 self-completed questionnaires by representative samples of adult participants in seven indoor sports at 46 separate sports facilities, in six U.K. cities. Six indicators of the respondents' health were inter-related and, for purposes of this analysis, are combined into a six-point scale, Males and females in all age groups who were taking part in the more physically demanding sports recorded the highest health scores. In addition, individuals who were playing these demanding sports more than once per week scored higher than those participating in the same activities less often. Health score was also found to be associated with other health-promoting lifestyle practices, such as never smoking and moderate alcohol consumption. Longitudinal corroboration will be necessary to confirm sport as a causal factor in the health-sport relationship, though the cross-sectional evidence from this enquiry is encouraging. It suggests that all types of physically demanding sport, competitive or not, offer measurable health gains to men and women of all ages and whatever their broader ways of living.

Adolescent↗
PubMed1988

The relationship between body-image and body-fat in adult women.

Measures of body-fat or adiposity, body-image, and other psychological variables were obtained from a sample of 100 female volunteer subjects. The measures of adiposity included surface anthropometry, underwater weighing and a new electrical impedance method. Body-image measures were derived from two experimental techniques, namely the visual-size estimation (or calliper) method and a distorting-mirror, and also from a self-report body-satisfaction scale (BSS). The main findings were that measures of adiposity were positively and significantly related to each other. But, that by contrast, measures of body-image separated out into three distinct sets, namely: (i) 'mirror' accuracy, (2) 'callipers' accuracy, and (3) 'dissatisfaction/desire for change'. The 'accuracy' measures were found to be unrelated to measures of adiposity or other psychological variables: while the 'dissatisfaction' measures were found to relate to both of these. The implications of these findings for future studies of weight and eating disorder groups are discussed.

Adult↗
PubMed1988

Techniques of measurement of body composition. Part I.

The measurement of lean body and fat mass has developed with the increase in sports participation and the prescription of exercise. Quantification of body fat is also related to the treatment of obesity and to assess nutritional status. Different levels of evaluation have been proposed depending on expertise and need. Body density estimation from skinfold measurements has the advantage of simplicity, low cost and reasonable validity with predictions to within 3 to 4% for 70% of the population. The choice of prediction equation will depend on whether a generalised equation or a population-specific equation is appropriate. In all cases tester reliability and standard error of estimation should be established. There is strong evidence that a quadratic equation should be applied and that measures of the lower limb should be included with circumference and diameter measures to strengthen the prediction. Methodological errors need to be reduced by careful training of experimenters. Crossvalidation of regression equation will strengthen their validity, particularly when fat loss is to be quantified. The popularity of skinfold assessment of body fat is enhanced by the use of nomograms to predict body fat, although some accuracy will be lost. Skinfold estimation of body fat will continue to be a useful guide to adiposity for epidemiological studies and for popular usage. The hydrostatic weighing procedure to estimate body density is considered by many to be the criterion method. Under carefully controlled conditions with maximum subject compliance, it is highly reliable, particularly if residual volume can be determined accurately. The conversion of body density to percentage body fat is based on a number of assumptions which need to be considered with respect to the population being studied. Simple methods for adiposity include various weight for height indices, for example, the body mass index of weight (kg) divided by height2 (m) which is often used to define obesity, frame size for the prediction of ideal weight and visual estimation for predicting body fat. Differences in the literature concerning fat cell size and number have their origins in variations of methodology. The choice of site for removal of tissue will influence the size of adipocytes, those obtained from deep sites are generally smaller than subcutaneous fat cells. If total cell number is determined from cell size, there will also be variability of cell number. The correlation between different methods of sizing cells is high for most techniques, but as the validity of the criterion method is not based on statistical evidence, the validity of the other methods cannot be readily accepted.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗
PubMed1986

Isokinetic measurement in preadolescent males.

Eighteen preadolescent males (mean age 11.4 +/- 0.59 years) performed 15 knee flexion-extension repetitions on both legs. Peak torque (T peak) and torque acceleration energy (TAE) were measured using the Cybex II Isokinetic system, which permitted a study of the effect of limb velocity on T peak, TAE, and reciprocal muscle group ratios. The effect of limb dominance was also assessed. The results indicated (Student's t test) that an increase in limb velocity from 1.05 rad/s to 4.2 rad/s produced a significant decrease in the T peak generated (P less than 0.001). A similar increase in limb velocity resulted in a significant increase in the TAE recorded (P less than 0.001). The limb velocity was also shown to influence the T peak and TAE ratios in reciprocal muscle groups. At a limb velocity 1.05 rad/s mean T peak ratios of 0.64 and 0.66 were recorded for the dominant and nondominant limbs, respectively. At 4.2 rad/s, ratios recorded for dominant and non-dominant limbs were 0.79 and 0.80, respectively. The limb velocity of 1.05 rad/s produced TAE ratios of 0.21 (dominant) and 0.14 (nondominant), and at 4.2 rad/s, ratios of 0.28 and 0.24 were recorded for dominant and non-dominant limbs, respectively. No significant difference (P less than 0.001) was observed between T peak and TAE values recorded for the dominant and non-dominant limbs under the same conditions. These results indicate that young boys show velocity-related isokinetic strength characteristics similar to adults. Although they have lower absolute levels, the children showed typical adult reciprocal muscle group ratios. Limb dominance at this age is not reflected in strength differences.

Age Factors↗