A descriptive analysis of elite-level racquetball.

The results of the three experiments provide insight into the time/motion characteristics of racquetball and the physiological responses of elite-level racquetball players during competition. The maximum oxygen uptakes of the male and female athletes tested were relatively low in comparison to those of other elite-level sports, suggesting that aerobic demand, although necessary, is probably not a limiting factor at this level of racquetball play. Racquetball games at the elite level last from 10 to 15 min, and the distance covered by each player during this time is minimal. Even though the rest periods between rallies are from one to two times as long as the work intervals, the work intensity during the rallies is sufficient to produce an average heart rate of between 75 and 95% of maximum throughout most of a game. Although some lactic acid accumulates in the blood, the concentration remains at a steady state during a game (10 to 30% of maximum).

Maternal physiologic adaptations to early human pregnancy.

This study was designed to test the hypothesis that significant maternal physiologic adaptations to pregnancy take place in multiple systems long before they are functionally necessary (during the embryonic period). To test this hypothesis, 20 women were studied serially before pregnancy and in the seventh and fifteenth postconceptional week of an accurately dated, clinically normal, singleton pregnancy. By the seventh week, significant changes were noted in body composition and cardiopulmonary and metabolic functions. Body fat and plasma volume increased 2% and 11%, respectively, accounting for all of the observed 2 kg weight gain. With the patient standing at rest after eating, heart rate increased 13 beats/min (16%) while mean arterial pressure fell 8 mm Hg (9%). Minute ventilation rose 24% and oxygen consumption increased by 27 ml/min, or 10%. The postprandial respiratory exchange ratio also increased, from 0.78 to 0.83; the whole blood glucose level was unchanged at rest, although there was a 15% decrease in whole blood lactate levels. We conclude that our hypothesis is correct, which suggests these adaptations are preparative and may have diagnostic value.