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Biomedical subjects

J F Clapp

Publications and source records attributed to J F Clapp.

At least 55 records · Page 3Linked to original sources
PubMed1991

The VO2max of recreational athletes before and after pregnancy.

This study was designed to test the hypothesis that pregnancy has an added training effect (increases "absolute" VO2max) in well-conditioned, recreational athletes. VO2max was measured serially in 20 nonpregnant recreational athletes who maintained their exercise within +/- 10% of initial levels over a 15-month period and 20 similar women who conceived and continued exercise at a reduced level during pregnancy with a return to within 20% of initial levels by 12 wk postpartum. Initially the two groups were similar in terms of age (30 +/- 1 vs 30 +/- 2 yr), weight 57.6 +/- 7.2 vs 59.7 +/- 7.5 kg), max pulse rate (189 +/- 8 vs 187 +/- 10 bpm), and absolute (3083 +/- 469 vs 3138 +/- 464 ml.min-1) VO2max. In the nonpregnant group the values obtained 15 months later were unchanged (weight = 57.8 +/- 6.6 kg, max pulse = 191 +/- 7 bpm, VO2max = 2977 +/- 397 ml.min-1) while those who conceived had a significant increase in absolute VO2max that was evident 12-20 wk postpartum and was maintained at the time of final testing 36-44 wk postpartum (3368 +/- 435 ml.min-1). Both weight (60.1 +/- 8.1 kg) and maximum pulse rate (185 +/- 12 bpm) were unchanged. These data indicate that pregnancy is followed by a small but significant increase in VO2max in recreational athletes who maintain a moderate to high level of exercise performance during and after pregnancy.

Adult↗
PubMed1991

Exercise and fetal health.

This is a brief review of current information dealing with the impact of maternal exercise on the well-being of the human embryo and fetus. It discusses the theoretical concerns and exercise variables involved in the interaction between exercise and fetal health and focuses on five areas of fetal health where some information is available describing the interaction in the human. These include embryonic development, fetoplacental growth, prematurity, indices of fetal stress/distress, and condition during labor and at birth. It concludes that well-conditioned women who continue a regular running or aerobics regimen in the peri-conceptual period and throughout pregnancy at levels that exceed current guidelines do not experience an increase in the incidence of failure to conceive, abortion, congenital abnormalities, abnormal placentation, premature rupture of the membranes or preterm labor. Although all their fetuses demonstrate a brisk elevation in heart rate post-exercise throughout pregnancy, they have a significant reduction in the incidence of 4 clinical markers of fetal stress/distress during labor. In addition, at the time of delivery, their % body fat is less than that of the control offspring (11 vs 16%) which accounts for over 70% of the observed 300 g reduction in birthweight. Finally, there is little evidence to suggest that the other exercise regimens studied to date have an adverse effect on fetal health.

Embryo Implantation↗
PubMed1990

The course of labor after endurance exercise during pregnancy.

This study was designed to test the hypothesis that continuation of a regular running or aerobics program, or both, during the latter half of pregnancy would have a negative effect on the course and outcome of labor. The onset, course, and outcome of labor were independently monitored in 131 well-conditioned recreational athletes who had an uneventful first half of pregnancy. Daily exercise performance was quantitated before conception and throughout pregnancy. Comparisons were made between the 87 women who continued to exercise regularly at or above 50% of their preconceptional level throughout pregnancy and the 44 who discontinued their regular exercise regimen before the end of the first trimester. The incidence of preterm labor was similar in the two groups (9%). Labor began significantly earlier in the exercise group (277 +/- 6 vs 282 +/- 6 days). The women who continued to exercise had a lower incidence of abdominal (6% vs 30%) and vaginal (6% vs 20%) operative delivery, and active labor was shorter (264 +/- 149 vs 382 +/- 275 min) in those who were delivered vaginally. Finally, clinical evidence of acute fetal stress (meconium, fetal heart pattern, and Apgar score) was less frequent in the exercise group (50% vs 26%), although birth weight was reduced (3369 +/- 318 vs 3776 +/- 401 gm). These data negate the initial hypothesis and indicate that, in well-conditioned women who regularly perform aerobics or run, continuation of these exercise regimens has a beneficial effect on the course and outcome of labor.

Adult↗
PubMed1990

Neonatal morphometrics after endurance exercise during pregnancy.

This study was designed to test the hypothesis that continuation of a regular running and/or aerobics program during late pregnancy at or above 50% of preconceptional levels limits fetal growth. Accordingly, detailed neonatal morphometric data were gathered in the offspring of two groups: 77 well-conditioned recreational runners and aerobic dancers who were delivered at term after continuing their exercise regimen at or above 50% of the preconceptional level throughout pregnancy and 55 matched controls. Daily exercise performance was quantitated before conception and throughout pregnancy. Significant reductions in birth weight (-310 gm), birth weight percentile (-20), ponderal index (-0.24), its percentile (-30), and the fetoplacental weight ratio (-0.7) were seen in the offspring of the exercise group whereas crown-heel length (51.4 cm) and head circumference (35.0) were similar in the two groups. Reductions in two-site skin-fold thickness (-1.5 mm), skin-fold percentile (-30), calculated percent body fat (-5.0%), and fat mass (-220 gm) in the offspring of the exercise group confirmed the asymmetric pattern of growth restriction and indicated that approximately 70% of the difference in birth weight could be explained by the difference in neonatal fat mass. In runners, the relative level of exercise performance in the last 5 months of pregnancy explained 40% of the variability in birth weight over an 1100 gm birth weight range. We conclude that continuation of a regular aerobic or running program at or above a minimal training level during late pregnancy results in an asymmetric pattern of growth restriction that primarily impacts on neonatal fat mass.

Adult↗
PubMed1989

Cardiovascular changes in early phase of pregnancy.

To assess the magnitude and timing of cardiovascular changes in pregnancy, eight subjects were serially studied before conception and at 8, 16, and 24 weeks' gestation. With the use of M-mode echocardiography, cardiac output, ejection fraction, stroke volume, and end-diastolic volume were calculated from left ventricular dimensions with subjects in the left lateral position. Systemic vascular resistance was calculated with the use of cardiac output and simultaneously obtained measurements of arterial pressure. Cardiac output increased 1 L/min at 8 weeks' gestation, which represented greater than 50% of the total change seen. Cardiac output increased primarily because of stroke volume rather than heart rate. By 8 weeks' gestation, systemic vascular resistance had fallen to 70% of its preconceptional value. Thus when subjects are studied before conception and during the early phase of pregnancy, the majority of the pregnancy-induced changes in these parameters occur during the embryonic period.

Adult↗
PubMed1989

The effects of maternal exercise on early pregnancy outcome.

This study was designed to test the hypothesis that vigorous aerobic exercise during both the periconceptional period and early pregnancy increases the incidence of abnormal early pregnancy outcome. Exercise performance was prospectively monitored before and during pregnancy in 47 recreational runners, 40 aerobic dancers, and 28 physically active, fit controls. Pregnancy was diagnosed by an early test for beta-subunit human chorionic gonadotropin and viability was confirmed by ultrasonography at 40 days' conceptional age. Spontaneous abortion occurred in 19% of the pregnancies. The incidence was 17% in the runners, 18% in the aerobic dancers, and 25% in the controls. At term, one congenital abnormality was detected in each of the three groups. Late pregnancy events, potentially related to abnormalities of placentation, were limited to two cases of mild pregnancy-induced hypertension. We conclude that, in physically fit women, continuation of these types of aerobic activity at intensities between 50% and 85% of maximum during the periconceptional period and early pregnancy does not appreciably alter early pregnancy outcome.

Abortion, Incomplete↗
PubMed1989

Oxygen consumption during treadmill exercise before, during, and after pregnancy.

This study was designed to test the hypothesis that the amount of oxygen required to complete a specific treadmill exercise protocol changes during pregnancy as a function of gestational age, weight gain, and an individual's exercise regimen. The amount of oxygen required to complete a three-step, graded workload treadmill protocol was monitored before, every 6 to 8 weeks during, and after a clinically normal, accurately dated, singleton pregnancy in 18 fit, recreational athletes. Nine subjects continued a moderate- to high-intensity exercise regimen and nine did not. The amount of oxygen required to complete each stage of the protocol decreased significantly (6% to 15%) in both groups in early pregnancy. In the women who continued exercise, the amount of oxygen required remained at or significantly below that required before conception for the remainder of the pregnancy and the initial postpartum period. Conversely, in the women who discontinued regular exercise, the amount of oxygen required for each stage rose progressively throughout the remainder of pregnancy at an average rate of 2% per lunar month. It peaked in the thirty-seventh week and remained significantly elevated 7 weeks post partum. However, when the data were corrected for the additional requirement imposed by pregnancy weight gain, net efficiency was increased in both groups throughout pregnancy. These data support three conclusions. First, the efficacy of low- to moderate-intensity treadmill exercise in physically active women is improved in early pregnancy. Second, this increased efficiency is masked later in pregnancy by the effects of weight gain. Third, the degree of efficiency is enhanced throughout pregnancy in women who continue a regular exercise regimen at or above a basic conditioning level.

Adult↗
PubMed1988

Ovine placental perfusion balance: effect of marijuana smoke.

This study was designed to test the hypothesis that maternal marijuana smoking impairs placental oxygen transfer in late ovine pregnancy by disrupting perfusion balance between the maternal and fetal placental circulations. Placental hemodynamics were assessed in nine chronically prepared ewes 1 hour after exposure to smoke from either a marijuana (n = 5) or a placebo (n = 4) cigarette. When compared with placebo smoke, maternal marijuana smoke exposure resulted in a fall in both uterine and umbilical placental vascular resistance and a 30% improvement in placental perfusion balance at a cotyledonary level. We conclude that maternal marijuana smoking in late ovine pregnancy has a direct relaxant effect on both maternal and fetal placental vascular smooth muscles that decreases the normal heterogeneity of flow and improves macroscopic placental perfusion balance. However, the observed concurrent 6 torr decrease in fetal oxygen tension suggests that perfusion balance is actually disrupted at a microcirculatory level.

Animals↗
PubMed1988

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.

Abortion, Spontaneous↗
PubMed1988

Brain damage after intermittent partial cord occlusion in the chronically instrumented fetal lamb.

The relationship between intermittent partial occlusion of the umbilical circulation and fetal acid base status, brain function, and neuropathologic outcome was assessed in nine control and nine experimental singleton fetal lambs to determine if transient episodes of partial cord occlusion play a role in antenatal brain damage in this species. Intermittent partial occlusion of the umbilical circulation for 1 minute of every 3 minutes for 2 hours was associated with a 89% incidence of histologically confirmed damage confined to the cerebral white matter. This occurred without systemic evidence of progressive acidosis, but both fetal heart rate patterns and electrocortical activity were altered. We conclude that in the late gestation fetal lamb, umbilical cord compromise plays a causal role in a specific type of antenatal central nervous system injury.

Acid-Base Equilibrium↗
PubMed1987

The effects of marijuana smoke on gas exchange in ovine pregnancy.

The effects of marijuana smoke on maternal respiratory rate and gas exchange were examined in nine chronically instrumented, late gestation ewes carrying singletons. The magnitude of exposure was randomly varied producing peak plasma levels of delta-9-tetrahydrocannabinol (delta-9-THC) ranging from 0 to 161 ng/ml. delta-9-THC levels, respiratory rate and arterial blood gas tensions were monitored before and for two hours after inhalational exposure. When compared to placebo, marijuana smoke produced a dose dependent and sustained decrease in maternal respiratory rate and arterial oxygen tension without evidence of either systemic acidosis or carbon dioxide retention. A logarithmic relationship was observed between the blood level of delta-9-THC and the change in respiratory rate. The change plateaued at 30% of control at levels above 80 ng/ml. However, the relationship between the blood level of delta-9-THC and the change in arterial oxygen tension had a linear fit with a maximum decrease of 45% at a blood level of 160 ng/ml. No change was detected in minute ventilation. Fetal oxygen tension fell significantly and remained depressed after maternal values had returned to control levels. We conclude that, in this species, inhalational exposure to marijuana smoke induces a prolonged maternal ventilation/perfusion imbalance and limits fetal oxygen availability by one or more mechanisms.

Animals↗
PubMed1987

Thermoregulatory and metabolic responses to jogging prior to and during pregnancy.

Ten joggers were serially studied prior to and during pregnancy at their individual training intensity levels to estimate their thermal and metabolic response to exercise in the field. Prior to conception, a 20-min run at 74% of VO2max (range = 62 to 90%) increased the respiratory exchange ratio to 0.90 +/- 0.01 (range = 0.87 to 0.96) with a rise in whole blood glucose (5.19 +/- 0.14 to 6.63 +/- 0.23 mM X l-1), lactate (0.61 +/- 0.06 to 2.62 +/- 0.74 mM X l-1), and rectal temperature (37.5 +/- 0.1 to 39.0 +/- 0.1 degree C). Despite a spontaneous decrease in exercise intensity to 57 +/- 5% of VO2max (range = 34 to 79%) at 20 and to 47 +/- 2% of VO2max (range = 36 to 59%) at 32 wk gestation, the rise in respiratory exchange ratio with exercise was maintained at 0.92 +/- 0.02 (range = 0.88 to 0.97) and 0.93 +/- 0.01 (range = 0.88 to 0.97), respectively, suggesting a shift to the left in the relationship between exercise intensity and fractional carbohydrate utilization by muscle during exercise in pregnancy. The concomitant changes in whole blood glucose before and after exercise at 20 (4.46 +/- 0.16 to 4.45 +/- 0.08 mM X l-1) and 32 (5.30 +/- 0.19 to 4.55 +/- 0.15 mM X l-1) wk further strengthen this view. Post-exercise, whole blood lactate levels at 20 (0.53 +/- 0.06 to 1.59 +/- 0.30 mM X l-1) and 32 (0.77 +/- 0.07 to 0.89 +/- 0.11 mM X l-1) wk were lower than those observed prior to pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Maternal heart rate in pregnancy.

Serial morning heart rates were obtained from 10 women runners prior to and during pregnancy. By 8 weeks' menstrual age, maternal heart rate had risen 8 bpm with an overall pregnancy-associated increase of 16 bpm. Potential mechanisms are discussed.

Female↗
PubMed1984

Regional distribution of cerebral blood flow in experimental intrauterine growth retardation.

The regional distribution of cerebral blood flow was assessed in eight control and eight morphometrically growth-retarded fetal lambs to determine whether perfusion patterns within the cerebral circulation are altered in this model of intrauterine growth retardation. Growth retardation was induced by repetitive embolization of the uterine circulation, and flow distribution was assessed by use of microspheres. Distribution to 22 separate areas, expressed as a flow/weight ratio, was virtually identical in the two groups. Cortical gray matter received 56% of total cerebral flow, and cortical white matter received 7%. However, flow X gm-1 in cortical white matter was 85% of that in cortical gray matter. We conclude that perfusion patterns within the cerebral circulation are not altered in this model of intrauterine growth retardation and that, compared to gray matter, cortical white matter has a high flow X gm-1 in fetal life.

Animals↗