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Biomedical subjects

J F Clapp

Publications and source records attributed to J F Clapp.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cardiovascular function before, during, and after the first and subsequent pregnancies.

This study was designed to test the hypothesis that the vascular remodeling of pregnancy begins early, persists for at least 1 year after delivery, and is accentuated by a second pregnancy. Serial estimates of heart rate, arterial pressure, left ventricular volumes, cardiac output, and calculated peripheral resistance were obtained before pregnancy, every 8 weeks during pregnancy, and 12, 24, and 52 weeks postpartum in 15 nulliparous and 15 parous women using electrocardiography, automated manometry, and M-mode ultrasound. During pregnancy, body weight increased 14.5 +/- 1.8 kg and returned to prepregnancy values 1 year postpartum. Heart rate peaked at term 15 +/- 1 beat/min above prepregnancy levels (57 +/- 1 beat/min). Mean arterial pressure reached its nadir (-6 +/- 1 mm Hg) at 16 weeks, returning to baseline at term. The increases in left ventricular volumes and cardiac output (2.2 +/- 0.2 L/min) peaked at 24 weeks as did the 500 +/- 29 dynes x cm x s(-5) decrease in peripheral resistance, and their magnitude was significantly greater in the parous women. Postpartum they gradually returned toward baseline but remained significantly different from prepregnancy values in both groups at 1 year. We conclude that cardiovascular adaptations to the initial pregnancy begin early, persist postpartum, and appear to be enhanced by a subsequent pregnancy. We speculate that persistence of these changes may lower cardiovascular risk in later life.

Adaptation, Physiological↗
PubMed1996

Morphometric and neurodevelopmental outcome at age five years of the offspring of women who continued to exercise regularly throughout pregnancy.

OBJECTIVE: To test the hypothesis that continuing regular, vigorous, sustained exercise throughout pregnancy adversely affects morphometric and neurodevelopmental outcome in offspring at 5 years of age. STUDY DESIGN: The offspring of 20 women who exercised were compared with those of 20 physically active control subjects. The women and their offspring were matched for multiple prenatal and postnatal variables known to influence outcome. All women were enrolled before the index pregnancy, monitored throughout, and had clinically normal antenatal, intrapartum, and postnatal courses. Morphometric measures were obtained at birth and at 5 years of age by a single, trained observer. Neurodevelopment was assessed by developmental psychologists masked to maternal exercise status. Data were analyzed with an unpaired Student t test. RESULTS: At birth, head circumference and length were similar, but the offspring of the exercising women weighed less (3.40 +/- 0.80 vs 3.64 +/- 0.70 kg) and had less fat (10.5% +/- 0.9% vs 15.1% +/- 0.6%). At 5 years of age, head circumference and height were similar, but the offspring of the women who exercised weighed less (18.0 +/- 0.5 vs 19.5 +/- 0.6 kg) and had a lower sum (sigma) of five site skinfolds (37 +/- 1 vs 44 +/- 2 mm). Motor, integrative, and academic readiness skills were similar. However, the exercise offspring performed significantly better on the Wechsler scales (125 +/- 2 vs 116 +/- 3) and tests of oral language skills (119 +/- 2 vs 109 +/- 3). CONCLUSIONS: These data refute the hypothesis and suggest that exercise during pregnancy reduces the subcutaneous fat mass of the offspring.

Adult↗
PubMed1996

Pregnancy outcome: physical activities inside versus outside the workplace.

There is concern that the thermal, cardiovascular, metabolic, and biophysical changes which accompany physical activity may have detrimental effects on both mother and fetus. Research focused on physical activity in the workplace has identified four specific physical stresses (quiet standing, long hours, protracted ambulation, and heavy lifting) that are associated with an increased incidence of both prematurity and low birth weight. The physiological basis for these is believed to be that these activities cause intermittent but protracted reductions in uterine blood flow. Research focused on recreational physical activity during pregnancy has not identified similar associations. Indeed, these data indicate that the overall impact of regular recreational exercise on pregnancy outcome is positive for both mother and fetus. The physiological basis for these beneficial effects is believed to be that the interaction between the physiological adaptations to both exercise and pregnancy improve maternal cardiovascular reserve, maternal mechanisms for heat dissipation, and placental growth and functional capacity. Finally, there is preliminary evidence suggesting that the vibratory and auditory stimuli associated with regular recreational exercise may enhance functional maturation of the fetal brain.

Animals↗
PubMed1995

The interaction between regular exercise and selected aspects of women's health.

The public health initiative to increase women's participation in regular recreational exercise to the 90% level raises multiple theoretic concerns about its impact on the reproductive health of women. However, at all points in a woman's life the overall effect of regular exercise to appetite appears to be beneficial rather than harmful, and in the absence of other stressors, exercise performance must significantly exceed usual recreational levels to have an adverse effect on any aspect of a woman's reproductive life. Therefore even in elite athletes abnormalities of any part of the reproductive process (puberty, menstrual cyclicity, pregnancy, lactation, and menopause) should not be attributed solely to exercise without complete evaluation. While generally beneficial, the interaction between exercise and skeletal integrity is influenced by hormonal status and multiple exercise variables. Thus, whereas regular exercise at all ages appears to provide both short- and long-term benefit, the characteristics of the exercise regimen need to vary at different time points.

Exercise↗
PubMed1995

The effect of regular maternal exercise on erythropoietin in cord blood and amniotic fluid.

OBJECTIVE: Our purpose was to test the hypothesis that continuing regular, high-intensity exercise until the onset of labor produces significant fetal hypoxemia, as evidenced by elevated erythropoietin levels in the fetal compartment. STUDY DESIGN: Erythropoietin levels were measured in samples of amniotic fluid and cord blood obtained from fetuses born to 31 exercising women and 29 matched controls. RESULTS: Erythropoietin levels (mean +/- SEM) in amniotic fluid obtained at the time of membrane rupture (9 +/- 2 vs 11 +/- 2 mU/ml) and in cord blood (38 +/- 6 vs 53 +/- 16 mU/ml) and amniotic fluid at delivery (9 +/- 1 vs 24 +/- 12 mU/ml) were no different in women who exercised regularly until the onset of labor. In both groups the majority of elevated cord blood levels (> 50 mU/ml) could be explained by labor events. Amniotic fluid erythropoietin levels correlated directly (r = 0.52) with cord blood hematocrit and increased slowly during labor. CONCLUSION: We conclude that the initial hypothesis is incorrect and speculate that cord blood erythropoietin reflects fetal oxygenation during labor, whereas amniotic fluid erythropoietin primarily reflects the adequacy of oxygenation before the onset of labor.

Adult↗
PubMed1995

The effects of maternal aerobic exercise on human placental development: placental volumetric composition and surface areas.

The histomorphometry of term placentae from women who exercised regularly throughout either the first half or all of pregnancy was compared to that of placentae from matched controls to determine if regular exercise during pregnancy produced histomorphometric evidence of altered development and transport capacity. Conventional stereological techniques were used to estimate placental volumetric composition, surface areas, and villous and vascular configurations in the three groups. Exercise confined to early pregnancy increased the parenchymal component of the placenta, total vascular volume and site-specific capillary volume and surface area. Exercise throughout pregnancy increased these and multiple other histomorphometric parameters associated with the rate of placental perfusion and transfer function. However, significant changes were confined to villi > 80 microns in diameter. The localization of both the timing of the stimulus and the anatomical sites affected indicates that regular, sustained exercise modifies placental development primarily in early and mid-pregnancy. We speculate that the lack of significant changes in the structure and configuration of the smaller villi indicates that other adaptive mechanisms, such as increased rates of placental blood flow, must be well developed by the latter portion of the mid-trimester and adequately maintain fetal oxygenation and substrate delivery throughout the third trimester.

Adult↗
PubMed1995

Effect of recreational exercise on pregnancy weight gain and subcutaneous fat deposition.

This study was designed to test the hypothesis that continuing a regular regimen of recreational endurance exercise alters the time-specific rate of maternal weight gain and subcutaneous fat deposition during pregnancy. Serial measurements of body mass and 5-site skinfold thickness were obtained from 44 women before and during pregnancy who continued their preconceptional exercise regimen throughout pregnancy and from women who voluntarily stopped their preconceptional exercise regimen either before conception (N = 31) or reduced it below baseline fitness levels in very early pregnancy (N = 4). In the first and second trimester, the rate of weight gain and change in skinfold thicknesses were unrelated to exercise performance. However, those who continued exercise had a reduced rate of weight gain and change in skinfold thickness at specific sites in the last trimester of pregnancy. Overall weight gains were (mean +/- SEM) 13.0 +/- 0.5 kg and 16.3 +/- 0.7 kg in the exercise and control groups, respectively, and the increases in the sum of skinfolds were 22 +/- 2 mm and 31 +/- 2 mm, respectively. We conclude that continuing a regular exercise regimen throughout pregnancy does not influence the rate of early pregnancy weight gain or subcutaneous fat deposition but decreases both in late pregnancy. However, overall pregnancy weight gain remains well within the normal range.

Adipose Tissue↗
PubMed1994

The physiological response of instructors and participants to three aerobics regimens.

This study was designed to test the hypothesis that there are regimen-specific differences in the thermal, metabolic, and cardiovascular responses of nonpregnant women when they perform their chosen type of aerobics at their usual performance level. Thirty-six instructors and 53 participants were studied while performing their chosen aerobics regimen under simulated field conditions using oxygen consumption as the index of exercise intensity. Under these conditions no significant differences were observed in the physiological response to low impact, high impact, or step regimens. However, although their ratings of perceived exertion were lower, the participants worked at a much higher exercise intensity than the instructors (76 +/- 1 vs 62 +/- 2% VO2max). As a result they attained a higher respiratory exchange ratio (0.96 vs 0.90), rectal temperature (38.62 vs 38.12 degrees C), and blood levels of glucose (5.70 vs 4.95 mmol.l-1), lactate (3.65 vs 1.60 mmol.l-1), and norepinephrine (2656 vs 1191 pg.ml-1). We conclude that both intensity and physiological response to aerobics are individual specific not regimen specific and that participants consistently underestimate their level of performance.

Adult↗
PubMed1994

A clinical approach to exercise during pregnancy.

Our knowledge is limited and there are serious theoretic concerns about combining a vigorous exercise regimen with pregnancy. The outcome data available, however, suggest that a healthy woman may begin or maintain a regular exercise regimen during pregnancy with benefit and without adversely affecting the course and outcome of the pregnancy. The data also suggest that the clear difference between theoretic concern and observed outcome is best explained by the hypothesis that the physiologic adaptations to exercise and to pregnancy are complimentary and feto-protective. Although the upper level of safe performance is not established, it appears that the otherwise healthy mother-to-be can obtain the benefits of a regular exercise regimen without undue risk to the embryo and fetus. The exact regimen can be flexible and individualized, provided that both the exercise and the pregnancy are monitored. In February 1994, a new set of guidelines for exercise during pregnancy and the postpartum period was published by the American College of Obstetricians and Gynecologists. These guidelines are more liberal than those mentioned previously. Interested parties should write to the American College of Obstetricians and Gynecologists, 409 12th Street S.W., Washington, DC 20024-2188 and ask for technical bulletin no. 189.

Adult↗
PubMed1993

The effect of sustained exercise on follicular phase levels of 17 beta-estradiol in recreational athletes.

OBJECTIVE: Our purpose was to test the hypothesis that sustained exercise elevates circulating levels of 17 beta-estradiol in an intensity-dependent manner. STUDY DESIGN: Blood samples were obtained in the follicular phase of the menstrual cycle from 75 female recreational athletes before and immediately after 20 minutes of aerobics or running at their usual exercise intensity. RESULTS: The levels of 17 beta-estradiol rose after exercise 97% of the time. At exercise intensities between 50% and 88% of maximum capacity there was a direct linear relationship (r = 0.57) between exercise intensity and magnitude of increase in estradiol levels. A similar relationship was not present for cortisol. CONCLUSION: Sustained exercise produces an intensity-dependent increase in the levels of 17 beta-estradiol that probably reflects decreased hepatic clearance caused by the fall in splanchnic blood flow. Thus the magnitude of the increase in the level of 17 beta-estradiol can be used as a rough index of the exercise-induced decrease in splanchnic blood flow.

Adult↗
PubMed1993

Fetal heart rate response to sustained recreational exercise.

OBJECTIVE: We aimed to test the hypotheses that fetal heart rate increases during and after sustained exercise and that the magnitude of the increases is related to gestational age and the duration, intensity, and type of exercise. STUDY DESIGN: Maternal oxygen uptake and fetal heart rate were monitored in 120 regularly exercising women in association with routine 20-minute workouts between 16 and 39 weeks' gestation. RESULTS: In 97% of the studies fetal heart rate increased during and after exercise. This was significant at all gestational ages and with all forms of exercise with an overall increase of 15 +/- 11 beats.min-1 at 60% +/- 12% of maximal aerobic capacity (mean +/- SD). The magnitude increased with gestational age (10 +/- 8 to 20 +/- 11 beats.min-1), exercise intensity (8 +/- 7 to 21 +/- 13 beats.min-1), and exercise duration (8 +/- 4 to 16 +/- 7 beats.min-1). CONCLUSION: We concluded that the hypothesis is correct and speculate that these changes represent a maturing fetal response to a reduction in Po2.

Bicycling↗
PubMed1992

Effect of recreational exercise on midtrimester placental growth.

OBJECTIVE: The purpose of our study was to test the hypothesis that regular recreational exercise increases the rate of growth in placental volume in the midtrimester of human pregnancy. STUDY DESIGN: Serial measurements of placental volume were obtained between the fourteenth and twenty-sixth gestational week in 18 subjects who exercised regularly throughout the midtrimester and in 16 matched controls with an ultrasonographic system equipped with a fixed-base, articulated-arm, 3.5 MHz B-mode transducer. RESULTS: Placental volumes were significantly greater in the women who maintained a regular exercise regimen throughout the midtrimester. At 16 weeks (mean +/- SD) volumes were 141 +/- 34 cm3 and 106 +/- 18 cm3 in the two groups. This difference increased at 20 weeks (265 +/- 67 cm3 vs 186 +/- 46 cm3) and again at 24 (410 +/- 87 cm3 vs 270 +/- 58 cm3) weeks' gestation because of a significant between-group difference in the rate of growth in placental volume over this time interval (34 +/- 8 cm3/wk vs 21 +/- cm3/wk). CONCLUSION: We conclude that the hypothesis is correct and speculate that the change in growth rate represents an adaptive response to the intermittent stimulus of a reduction in regional blood flow.

Adult↗
PubMed1991

The changing glycemic response to exercise during pregnancy.

This study was designed to test the hypothesis that pregnancy reverses the nonpregnant hyperglycemic response to sustained exercise. Serial data were obtained from 75 exercising women. Before pregnancy, exercise produced an intensity-dependent increase in blood glucose that averaged 1.5 mmol/L at high intensities. By the eighth week this response was blunted and blood glucose increased only when exercise intensity exceeded 80% of maximum. At 15 weeks this progressed and was not associated with a change in either the insulin or catecholamine response. By the twenty-third week exercise produced a decrease in blood glucose that was no longer related to exercise intensity. We conclude that the hypothesis is correct and speculate that the early change in the response is related to decreased hepatic glucose release coupled with increased glucose oxidation. In late pregnancy this is probably accentuated by fetoplacental demands.

Adult↗
PubMed1991

The changing thermal response to endurance exercise during pregnancy.

This study was designed to test the hypothesis that the thermal response to endurance exercise is altered by the thermal adaptations to pregnancy. Accordingly, rectal temperature was monitored in 18 recreational athletes before, during, and after 20 minutes of continuous exercise before conception and every 6 to 8 weeks during pregnancy. Mean exercise intensity was 64% of VO2 max before conception and did not change during pregnancy. However, the peak rectal temperature reached during exercise decreased by 0.3 degrees C at 8 weeks and then fell at a rate of 0.1 degrees C per lunar month through the thirty-seventh week. This appeared to be related to changes in resting temperature, thermal mass, sweating threshold, and venous capacitance that began early in pregnancy. These data suggest that the magnitude of any exercise-associated thermal stress for the embryo and fetus is markedly reduced by the maternal physiologic adaptations to pregnancy.

Adult↗
PubMed1991

When do cardiovascular parameters return to their preconception values?

To determine if the postpartum period is reflective of a woman's cardiovascular status before pregnancy, we performed serial studies of 13 women before conception and at 6 and 12 weeks post partum. All pregnancies were singleton without hypertensive complications. Cardiac output, stroke volume, and end-diastolic volume were calculated with M-mode echocardiography from the left ventricular dimensions with subjects in the left lateral position. Systemic vascular resistance was calculated from cardiac output and simultaneous measurements of blood pressure. Stroke volume and end-diastolic volume remained consistently elevated over preconception values at 6 and 12 weeks. Systemic vascular resistance remained decreased, compared with baseline, at 12 weeks. Thus cardiovascular parameters had not returned to the preconception baseline, and previous studies that have used this time period for comparison have underestimated the contribution of stroke volume to the total change in cardiac output during pregnancy.

Adult↗