Investigators have suggested that opiate peptide hormones released during exercise stress may play an important role in athletic performance or perceived effort. Their enzymatic inactivation in the periphery is of considerable interest since the opiate peptides may be regulated by enkephalin hydrolyzing enzyme (EHA). In this study, the relationship between maximal aerobic capacity (VO_2max) and EHA activity was examined in two distinct fitness groups. When the metabolic capacity was evaluated in whole blood, the unfit subjects metabolized the peptides significantly faster than their fit counterparts. Since the total enzyme activity of the two groups is similar, the difference in metabolism must result from circulating factors in the trained athletes, which slow the rate of peptide inactivation.

The purpose of this study was to examine selected mechanical factors involved in the tennis serve. Special emphasis was placed on identifying factors which distinguish players of different serving abilities. Ten right-handed female tennis players, five ranked, and five unranked, were evaluated, following filming with a high-speed camera, on the basis of five good and five fault serves. The ranked players were seen to differ from the unranked players with respect to (a) serving consistency, (b) initial Y-center of gravity values, (c) certain segment angles at the peak of the ball toss and at ball contact, and (d) certain joint angles at the moment of the ball contact.

Eighteen subjects each performed fifty-five trials which consisted of assuming an initial stance and then in response to a visual stimulus running to either the left or right. For each trial both the foot width spacing and orientation of the feet were varied. Direct and indirect measurements were taken of selected temporal and kinematic parameters. The conclusions were that no interactions or differences exist among foot width spacing, foot orientation, and direction of movement; the jab step start is the preferred initial movement; the preferred foot width spacing is 46.6 centimeters; the preferred angular orientation of both feet is approximately 1.36 radians.

The primary purpose of the study was to determine if measured LBM could be used as a more powerful predictor of BMR than could surface area (SA) as calculated by the formula of DuBois and DuBois (1916). It was also of interest to develop a prediction equation for BMR using multiple regression analysis. Data from 82 women and 76 men were included in the study. Pearson product-moment correlations indicated that LBM was a better predictor for BMR than SA on either of the principal SA prediction equations, those of Aub and DuBois (1917) and Harris and Benedict (1919). Age, sex, and fat weight were not found to contribute significantly to prediction when included by multiple regression analyses. Linear equations for BMR as a function of LBM were developed for each sex. Tables based on these equations were also generated as a quick reference for clinicians.

Sixteen males and sixteen females were recruited for this study; eight of each gender were aerobically trained athletes; the remaining eight were untrained control subjects. Each subject performed a maximal exercise stress test for aerobic capacity (VO2max). On a separate day the blood volume and the cardiovascular responses to progressive (0 to -50 torr) lower body negative pressure (LBNP) were determined. The female subjects were observed to be significantly more tolerant of the LBNP than the male subjects. No differences between groups were observed in changes in leg volume, cardiac index, blood pressure, or heart rate during LBNP. However, the females, in comparison to the males, maintained stroke index at a higher level, and increased regional vasoconstriction more, during the LBNP induced hypotensive stress. These findings suggest that female subjects withstand LBNP to -50 torr better than male subjects.

In this study, the relationship between maximal aerobic capacity (VO₂max) and left ventricular function was examined in two distinct age groups. A young group (20 - 30 years of age) and an elderly group (over 60 years of age) were compared. Left ventricular function was examined over wide variations in preload accomplished by 5º head-down tilt (TILT) for ninety minutes and lower body negative pressure (LBNP) to -40 mm Hg. with two-dimensional echocardiography. A greater response to an increase in preload (TILT) was related to high VO₂max levels in the young subjects but not in the elderly groups of subjects, suggesting that lower VO₂max levels of the elderly population affected the mechanism of response to the increased levels of preload. Additionally, in the elderly, greater reductions in ventricular volume reflected increased peripheral pooling due to decreased venous tone and/or increased venous compliance during LBNP and were related to increased VO₂max. In the young, VO₂max does not appear to affect the response to reduced preload.