Biomedical subjects

J A Pawelczyk

Publications and source records attributed to J A Pawelczyk.

21 records · Page 2Linked to original sources

PubMed1988

Cardiovascular responses to head-up tilt after an endurance exercise program.

The cardiovascular responses to 10 min of orthostasis were assessed before and after an aerobic exercise program. Five men and five women (18-25 years old) exercised for 7 weeks, four times per week, for 50 min per session at 70% of maximal heart rate (HR). Before and after the exercise program, maximal aerobic power (VO2max) was determined, and HR, systolic (SBP), diastolic (DBP), and pulse (PP) blood pressures were measured each minute during 5 min of supine rest, 10 min of foot-supported 70 degree head-up tilt (HUT), and 5 min of supine rest. Orthostatic tolerance was not determined. Calf compliance was measured in five of the subjects before and after the program as the change in leg volume at occluding pressures of 20, 40, 60, 80, and 100 mm Hg. Following the program, VO2max increased by 8.7% (p = 0.012), while decreases were noted in resting HR (9.4%, p = 0.041), SBP (5.0%, p less than 0.0005), and DBP (14.2%, p less than 0.0005). Despite a greater HR increase during HUT (7.1 beat.min-1, p = 0.034), SBP decreased by 3.4 mm Hg during HUT after the exercise program (p = 0.008). No differences were noted in the changes in DBP, MAP, or PP upon tilting (p greater than 0.05). After the program, the amount of fluid pooled in the calf at high occluding pressures (80 and 100 mm Hg) increased by 0.96 +/- 0.24 and 1.10 +/- 0.33 ml.100 ml tissue-1 (X +/- S.E.M., p = 0.017 and p = 0.028, respectively). We suggest that control of blood pressure during 10 min of orthostasis may be altered by endurance exercise training.

Adult↗

PubMed1985

Velocity, stroke rate, and distance per stroke during elite swimming competition.

The mean velocity of 9 out of 10 women's events during the U.S. Olympic Swimming Trials was greater in 1984 as compared to 1976. Three of the 10 men's events showed improvement. In 9 out of these 12 events, the increased velocity was accounted for by increased distance per stroke (range, -3 to -13%). In the women's 100-m butterfly and 100-m backstroke, increased velocity was due solely to faster stroke rates. The finalists in each event were compared to those whose velocities were 3-7% slower. In almost all events and stroke styles, the finalists achieved greater distances per stroke than did the slower group. In the men's events increased distance per stroke was associated with decreased stroke rate, except in the backstroke, in which both were increased for the finalists. Although the faster women swimmers generally had greater distances per stroke, they were more dependent than men on faster stroke rates to achieve superiority. The profile of velocity for races of 200 m and longer indicated that as fatigue developed the distance per stroke decreased. The faster swimmers compensated for this change by maintaining or increasing stroke rate more than did their slower competitors. This study indicates that improvements and superiority in stroke mechanics are reflected in the stroke rate and distance per stroke used to swim a race.

Arm↗

PubMedDate not supplied

Cardiorespiratory and phrenic nerve responses to graded muscle stretch in anesthetized cats.

This study examined the cardiovascular, ventilatory, and phrenic nerve responses to graded activation of mechanically sensitive muscle afferents. Using eight alpha-chloralose anesthetized cats, the left and right triceps surae muscles were stretched individually and simultaneously at progressive increments (0.5, 1.0, 1.5, 1.75 cm). Muscle stretch elicited sustained increases in mean arterial blood pressure (MAP) and heart rate (HR). These changes were related to the degree of stretch, as stretching one muscle 0.5 cm increased MAP 15 +/- 2 mmHg and HR 7 +/- 2 beats/min, while stretching both legs (1.75 cm) increases these variables 40 +/- 11 mmHg and 11 +/- 3 beats/min. By contrast, muscle stretch initially decreased ventilation and phrenic nerve activity. After the initial fall, ventilation, but not tidal phrenic activity, increased above baseline. These results show that a divergence exists between the initial cardiovascular and ventilatory responses to activation of mechanically sensitive muscle afferents. Further, the hyperpnea elicited by muscle stretch in spontaneously breathing anesthetized cats appears to be the result of excitation of non-diaphragmatic muscles of ventilation.

Animals↗