Considerations of anthropometric, tissue volume, and tissue mass scaling for improved patient specificity of skeletal S values.

It is generally acknowledged that reference man (70 kg in mass and 170 cm in height) does not adequately represent the stature and physical dimensions of many patients undergoing radionuclide therapy, and thus scaling of radionuclide S values is required for patient specificity. For electron and beta sources uniformly distributed within internal organs, the mean dose from self-irradiation is noted to scale inversely with organ mass, provided no escape of electron energy occurs at the organ boundaries. In the skeleton, this same scaling approach is further assumed to be correct for marrow dosimetry; nevertheless, difficulties in quantitative assessments of marrow mass in specific skeletal regions of the patient make this approach difficult to implement clinically. Instead, scaling of marrow dose is achieved using various anthropometric parameters that presumably scale in the same proportion. In this study, recently developed three-dimensional macrostructural transport models of the femoral head and humeral epiphysis in three individuals (51-year male, 82-year female, and 86-year female) are used to test the abilities of different anthropometric parameters (total body mass, body surface area, etc.) to properly scale radionuclide S values from reference man models. The radionuclides considered are 33P, 177Lu, 153Sm, 186Re, 89Sr, 166Ho, 32P, 188Re, and 90Y localized in either the active marrow or endosteal tissues of the bone trabeculae. S value scaling is additionally conducted in which the 51-year male subject is assigned as the reference individual; scaling parameters are then expanded to include tissue volumes and masses for both active marrow and skeletal spongiosa. The study concludes that, while no single anthropometric parameter emerges as a consistent scaler of reference man S values, lean body mass is indicated as an optimal scaler when the reference S values are based on 3D transport techniques. Furthermore, very exact patient-specific scaling of radionuclide S values can be achieved if measurements of spongiosa volume and marrow volume fraction (high-resolution CT with image segmentation) are known in both the patient and the reference individual at skeletal sites for which dose estimates are sought. However, the study indicates that measurements of the spongiosa volume alone may be sufficient for reasonable patient-specific scaling of S values for the majority of radionuclides of interest in internal-emitter therapy.

Using perceived exertion to prescribe and monitor exercise training heart rate.

We examined whether feedback of heart rate (HR) or HR combined with ratings of perceived exertion (RPE and HR) during a graded exercise test (GXT) and during early trials of field training would reduce the errors commonly seen when training heart rate range (THR) is self-monitored by participants. Asymptomatic males (n = 24) were tested on a Balke treadmill protocol in a randomized, between-groups design under control conditions or conditions where feedback about HR or HR combined with RPE were given as age-predicted THR was approximated. This was followed on alternating days by three field trials of an 800-m jog where errors between prescribed and attained THR were fed back to each subject. A priori 95% confidence intervals for the first field trial showed that signed (algebraic) error for the HR combined with RPE condition (+3 bts/min) was less than for controls (+23.5 bts/min). Feedback of HR alone was no different from the control condition. All groups showed increased accuracy (P less than .05) by the third field trial [absolute error: T1 (18 bts/min) to T3 (9.6 bts/min); signed error: T1 (+14 bts/min) to T3 (+4 bts/min)]. Our results suggest feedback of HR combined with RPE during a GXT may reduce an overshoot in THR during the first of subsequent exercise sessions. Feedback of HR alone appeared sufficient to further reduce THR errors after a third exercise session in the field. The procedures used may have practical importance for sedentary, unfit, or diseased individuals where conservative HR prescriptions are desirable but electronic monitoring is not feasible or cost effective.

Comparison of heart rate measurement protocols used during autonomic function tests.

The five most used cold pressor test heart rate protocols were compared to the true R-R interval responses recorded during a cold hand test. Forty-one nonsmoking male volunteers between 18 and 55 yr were given a cold hand pressor test. Heart rate was evaluated by averaging the R-R interval within 2-, 5-, 6-, 10-, and 30-s time intervals and by the true R-R interval measurement. No significant physiological differences existed at rest; however, during stress the maximum values obtained were successively diminished the greater the time utilized to average the heart rate pressure (P less than 0.05). During recovery an underestimation of the true response was observed that increased as the averaging time increased (P less than 0.05). Comparison between the R-R interval measure and the 6-s average data indicated a 18% decrease in the time of peak response. Therefore, the responses recorded with the 6-s averaged data were less sensitive and obscured the rapidity of autonomic changes. Hence, when sensitivity and absolute response are a primary concern in determining autonomic function, measurements should include R-R interval measures of heart rate or the average of the number of R-R intervals in 2-s time blocks.

A factor analysis of twelve selected maximal isotonic strength performances on the universal gym.

This study sought to isolate and identify the underlying structure of the isotonic strength domain as exhibited on the Universal Gym. Maximal isotonic contractions were elicited from 88 college male subjects involved in a weight training program on 12 selected exercises. Factor analysis was applied to the data to delineate the underlying structure. Analysis of the raw data revealed an unclear nonrobust factor structure. However, when the variance of the anthropometric vaiables of height and weight were statistically held constant from the raw data, subsequent factor analysis of the statiscally controlled data yielded a robust three factor structure. Factor 1 was related to upper extremity and trunk isotonic strength; Factor II, lower extremity isotonic strength; Factor III, trunk and upper extremity isotonic strength. Thus, when evaluating isotonic strength responses on the Universal Gym, upper, lower extremity and trunk measures as body segments should be utilized; also, anthropometric measures of height and weight should be considered.

Fatigue curves of isokinetic contractions.

Sixteen men and 16 women volunteer college students were tested for elbow flexion fatigue curve production on the Orthotron, an isokinetic testing device. Maximal voluntary contractions were obtained repeatedly, each contraction taking approximately 2 seconds to complete, with minimal (500 msec) intertrial rest, to exhaustion. To provide a basis for plotting the isokinetic fatigue curve, the degradation of torque values from initial to final contractions, was expressed as percentage of contraction time. Results obtained following statistical analysis of the data indicated that the isokinetic fatigue curve is: (1) curvilinear; (2) independent of sex differences; and (3) a function of initial strength. Moreover, it was found that the use of 50% of initial strength to denote fatigue in repetitive rhythmic isokinetic work has merit as a conservative estimate.