D. A. Brodie

Isokinetic dynamometry. Applications and limitations.

SummaryIsokinetic 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.

Body Composition Measurement: A Review of Hydrodensitometry, Anthropometry, and Impedance Methods

Human body composition is an expression of genetic and nutritional factors. It can change as a consequence of exogenous influences such as training, disease, or diet and is therefore of particular interest to nutrition professionals. Two of the main methods of estimating body composition in this review (hydrodensitometry and anthropometry) have been in use for decades, but the third method (bioelectrical impedance) is more recent. The procedure, theoretical basis, assumptions, standard error of estimates, and comparisons with other techniques are presented for each of the three methods. References to general and specific populations are presented that illustrate regression equations for different ages, ethnic groups, and gender. The advantages and disadvantages of the three methods are reviewed with reference made to the alternative compartment models. Other methods (DEXA, infrared interactance) are briefly reviewed.

DEVELOPMENT AND PRELIMINARY VALIDATION OF THE BODY SATISFACTION SCALE (BSS)

Abstract This paper describes the development of a simple paper-and-pencil test designed to measure satisfaction/dissatisfaction with 16 body parts. It is based on the body-cathexis scale of Secord and Jourard (1953) but takes only 2–3 minutes to complete. The factorial structure of the scale is described together with the three summative scales (“general,” “head parts” and “body parts” dissatisfaction) which are derived. The internal consistency of the scales was found to be acceptable. Significant positive correlations are also reported with the Body Shape Questionnaire (Cooper et al., 1987). The paper reports data for female comparison groups (college students, nursing students and female volunteers) and for samples of eating disorder patients and overweight subjects. The latter two groups report significantly higher body dissatisfaction than the comparison groups. Finally, it is argued that the scale is useful for work in health related fields and some current applications are briefly described.

Dental erosion, oral hygiene, and nutrition in eating disorders

OBJECTIVE To determine the influence of oral hygiene practices and additional fluoride on erosive tooth wear in eating disorders. The proportional dietary intake of carbohydrates, fats, and proteins was also investigated. METHOD Tooth wear was measured with the use of the tooth wear index (TWI). All subjects completed a questionnaire on past dental history as well as a 1-week diet sheet. A total of 33 subjects participated in the study, 20 of whom were follow-ups, allowing the progress of dental erosion to be made. All subjects were referred from the Department of Clinical Psychology. RESULTS Oral hygiene practices between subjects with and without severe erosion were not significantly different. Only 8 bulimics spent more time brushing after vomiting than at other times. The pH of vomitus from 6 subjects ranged between 2.9 and 5.0, with a mean of 3.8, well below the critical pH for enamel demineralization to occur. Of the 20 follow-up subjects, 12 (60%) exhibited worsening tooth wear. The mean values for daily carbohydrate, protein, and fat intake were not significantly different at baseline and at recall, and the proportional dietary intake was similar to recommended energy provision at 47%, 40%, and 13%, respectively. DISCUSSION The contribution by toothbrush abrasion to the overall wear in the eroded dentition of bulimics is not significant. Therefore, immediate post-vomiting oral hygiene practices can be recommended. The proportional nutritional intake values of carbohydrates, fats, and proteins in this group of bulimics are acceptable.

Responses to arm and leg ergometry.

Arm (A), leg (L) and combined arm and leg (A + L) ergometry modes were compared at power outputs of 49, 73.5 and 98 W. Selected cardiorespiratory variables and a rating of perceived exertion (RPE) were measured for 19 males of mean age 25.7 (+/- 5.5) years. Oxygen uptake (VO2), heart rate (HR), minute ventilation and rating of perceived exertion (RPE) were all higher (p less than 0.01) in A compared with L and A + L. Gross mechanical efficiency was significantly lower in A (p less than 0.01) than in L or A + L. No differences were observed in any measurements between L and A + L. the correlations between RPE and cardiorespiratory variables were higher for A (RPE:VO2, r = 0.87, p less than 0.01; RPE:HR, r = 0.78 p less than 0.01) than for L and A + L.

Estimation of body composition in muscular dystrophy by MRI and stereology

We have applied the Cavalieri method of modern design stereology with magnetic resonance imaging for estimating the volume of whole‐body muscle and fat compartments in four patients with muscular dystrophy, a patient with myopathy, five controls, an anorexic subject, and a body builder. Detailed systematic series (ie, 50) of axial MR images (T1‐weighted, TR/TE 400/10 msec) were obtained throughout the whole body of each subject. The results showed that 15, 20, and 35 axial sections through the body are sufficient to secure coefficients of error (CEs) on the estimates of total muscle and fat volume of around 10%, 5%, and 3% respectively in muscular dystrophy patients and controls. The mean normalized volumes of muscle in four muscular dystrophy patients were decreased by 27% (t‐test: P < 0.05), and those of total fat were increased by 12% (t‐test: P > 0.05) relative to controls. The Cavalieri method provides a direct, efficient, and mathematically unbiased approach for studying human body compartments and may have application in assessing treatment efficacy in patients with muscular dystrophy. J. Magn. Reson. Imaging 2000;12:467–475.

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.

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

SummaryThe 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 (lab), mean arterial pressure (MAP), respiratory exchange ratio (R) and rating of perceived exertion (RPE) were measured during a submaximal cycle ergometry test 1 week bevore, 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), lab (0.75–1.00 mmol·1−1 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·ss−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. Despite the physiological alterations, subjects could tolerate short-term, steady-state exercise during VLCD, with only slight increases in RPE. However, greater fatigue is associated with long duration strength training exercises during VLCD.

Sporting Lives: A Case Study of Leisure Careers

Abstract This article analyses the sport biographies, and current levels and patterns of participation among a sample of 1679 adults from six United Kingdom cities, of whom 1387 were initially contacted through user surveys at sports facilities, plus a more representative sample of 606 residents in inner-Belfast. The authors argue that lifetime patterns of sport participation and non-participation are shaped by much the same influences, and exhibit similar features to careers in other leisure activities. Moreover, the processes that lock-in long-term sport participants and exclude others are similar to those that operate in occupational careers. The findings show that sport participation declines with age, but so does the give-up rate, so loyalty among those who continue to be sports active actually increases. There is evidence in the United Kingdom of an increase in sport activity in the 50-plus age group among individuals who remain sports-active into this life-phase. Social class inequalities in sport ...

Dietary versus healthy life style interventions in the treatment of obesity: Resultant changes and the prediction of outcome

Abstract This study compares both weight and fat loss in overweight women exposed to two styles of programme and two levels of intervention. Body image and other psychological changes were examined including an eating disorder scale, motivational variables and depressive symptoms. The results showed that weight loss is influenced by different styles of intervention but this does not apply to the fat measurements. During the overall treatment period certain psychological changes were observed but no significant differences were exhibited between the treatment groups. The significant change in the “perfectionist” scores on the SCANS test suggests that dieters may reset their weight reduction targets inappropriately, resulting in eventual failure. A number of correlations were significant when these measures were compared with weight loss after the treatment. It appeared that motivational differences are only important in determining involvement not outcome. Psychological differences appear not to precede we...