AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 3 July 1990
NONWEIGHTBEARING EXERCISE DURING PREGNANCY ON LAND AND DURING IMMERSION: A COMPARATIVE STUDY Vern L. Katz, M.D., Robert McMurray, Ph.D., WE. Goodwin, M.A., and Robert C. Cefalo, M.D., Ph.D.
ABSTRACT
This report describes an investigation comparing similar aerobic nonweightbearing exercise on land with the same exercise at the same intensity in the water. We were interested in contrasting the effects of similar exercise in the two environments on the mother and the fetus. Exercise in the water, such as water aerobics and swimming, may have several potential advantages over land exercise for pregnant women.1"3 Water supports the mother's weight so that immersion is nonweightbearing.2'3 Nonweightbearing exercise may be physiologically less demanding to the pregnant woman.45 Buoyancy creates a feeling of comfort and eliminates the clumsiness many pregnant women experience when exercising on land. The hydrostatic force of the water causes redistribution of interstitial fluid resulting in an increase in maternal plasma volume.1'67 During pregnancy, the increase in plasma volume compensates for the exercise-induced hemoconcentration.8 Water also improves heat dissipation compared with air.2>8>9 Since temperature elevation and hyperthermia may be detrimental to the developing fetus,4-10-11 any reduction in maternal heat accumulation is desirable. Thus, there is ample reason to examine the effects of exercise in a water environment. A discussion of the differences in the thermoregulation between water and land exercise
Downloaded by: Universite Laval. Copyrighted material.
Seven women at 25 weeks' gestation exercised on land and in the water at 70% maximum oxygen capacity (VO2max) on a bicycle ergometer. Women had significantly lower heart rates and lower systolic blood pressures during immersion exercise. Women had a mean diuresis of 207 ml (6.5 ml/min) during water exercise compared with 98 ml. (2.4 ml/min) during land exercise. Fetal heart rates showed a tendency toward being higher after land exercise compared with water exercise. Six of seven fetuses displayed tachycardia after land exercise compared to one of seven after water exercise. Exercise on land and during immersion at 70% VO2max was well tolerated. However, exercise during immersion offers several physiologic advantages during pregnancy.
has been described elsewhere and is included here for completeness.12 MATERIALS AND METHODS
This investigation was performed at the Exercise Physiology Laboratory of the University of North Carolina at Chapel Hill. The investigation was approved by the Committee for Research with Human Subjects. Pregnant volunteers were recruited by advertisements in the obstetric offices of the University of North Carolina School of Medicine. After a screening history and physical examination, the subjects were familiarized with the procedure and protocol and trained in the use of the bicycle ergometer and breathing mechanism. Subjects were excluded if there were any obstetric or medical contraindications to exercise. Subjects were tested between 25 and 26 weeks' gestation. Testing was performed 2 hours postprandial, in the midafternoon. All subjects completed the experiment without difficulty. The experimental protocol consisted of three sessions separated by 3 to 7 days. During the first visit, an estimation of the subjects' maximum oxygen capacity (VO2max) was obtained through incremental submaximal testing.13 Subjects performed graded
The Department of Obstetrics and Gynecology, The School of Medicine, and The Department of Physical Education, University of North Carolina, Chapel Hill, North Carolina Reprint requests: Dr. Katz, 214 MacNider Building, CB #7570, The Department of Obstetrics and Gynecology, The University of North Carolina, Chapel Hill, NC 27599-7570 Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
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been previously reported.1-2 Essentially, the subjects breathed through a Hans Rudolph valve attached to a Parkinson Cowan gasometer to quantify minute ventilation. Expired air was collected in a mixing chamber and gases analyzed with an applied electrochemistry S-3A oxygen analyzer and a Beckman LB-2 carbon dioxide analyzer. Urine specific gravity was obtained by refractometry. Oxygen uptake, blood pressure, fetal heart rate, and maternal heart rate were analyzed using a within subjects ANOVA, comparing land and water trials across times that these variables were measured. If significance was found, p < 0.05, a post hoc Newman-Keuls test was used to assess which values created the differences. Urine volumes and specific gravity were evaluated by a dependent t test. RESULTS
The levels of exertion in the land and water trials were similar. A mean VO2 of 1.38 liters/m was obtained during immersion, compared to a mean of 1.40 liter s/m during land exercise. Maternal heart rates were greater on land than in the water (p < 0.005). Systolic blood pressures were also greater during land exercise than water exercise (p < 0.05), and diastolic blood pressures were similar. The resting values of rectal temperatures were equal, 37.2°C. After 20 minutes of exercise, the mean rectal temperature after land exercise was 37.7°C versus 37.4°C after water exercise, p < 0.05. Although statistically significant, the clinical relevance of this difference is speculative. Rectal temperatures decreased from 37.8° to 37.4°C over the 20-minute recovery period after land exercise. Temperatures after immersion exercise decreased from 37.5° to 37.2°C.There was no significant difference in rectal temperatures between land and immersion exercise during recovery, and no subject had a temperature greater than 38.0°C. Oxygen uptake, heart rate, and systolic blood pressure are listed in Table 1. Urine volumes during land and water trials were very different. The mean urine output during the land trial was 98 cc versus 261 cc during the water trial, p < 0.005. Changes in specific gravity were also quite different, p < 0.008. Subjects in the water had a mean dilution of 1.012 to 1.006 compared to a small urinary concentration from 1.013 to 1.015 during land exercise. Fetal heart rate data are listed in Table 2. Resting fetal heart rates and immediate postexercise fetal heart rates were similar between land and water trials. However, the change from rest to 5 minutes into recovery was different between the two trials (p < 0.025). The rise in fetal heart rate was 12 beats/ min on the land versus a 1 beat/min rise after the water trial. The fetal heart rates at 10, 15, and 20 minutes showed a tendency to be greater after land exercise than after water exercise (p
NONWEIGHTBEARING EXERCISE DURING PREGNANCY ON LAND AND DURING IMMERSION: A COMPARATIVE STUDY Vern L. Katz, M.D., Robert McMurray, Ph.D., WE. Goodwin, M.A., and Robert C. Cefalo, M.D., Ph.D.
ABSTRACT
This report describes an investigation comparing similar aerobic nonweightbearing exercise on land with the same exercise at the same intensity in the water. We were interested in contrasting the effects of similar exercise in the two environments on the mother and the fetus. Exercise in the water, such as water aerobics and swimming, may have several potential advantages over land exercise for pregnant women.1"3 Water supports the mother's weight so that immersion is nonweightbearing.2'3 Nonweightbearing exercise may be physiologically less demanding to the pregnant woman.45 Buoyancy creates a feeling of comfort and eliminates the clumsiness many pregnant women experience when exercising on land. The hydrostatic force of the water causes redistribution of interstitial fluid resulting in an increase in maternal plasma volume.1'67 During pregnancy, the increase in plasma volume compensates for the exercise-induced hemoconcentration.8 Water also improves heat dissipation compared with air.2>8>9 Since temperature elevation and hyperthermia may be detrimental to the developing fetus,4-10-11 any reduction in maternal heat accumulation is desirable. Thus, there is ample reason to examine the effects of exercise in a water environment. A discussion of the differences in the thermoregulation between water and land exercise
Downloaded by: Universite Laval. Copyrighted material.
Seven women at 25 weeks' gestation exercised on land and in the water at 70% maximum oxygen capacity (VO2max) on a bicycle ergometer. Women had significantly lower heart rates and lower systolic blood pressures during immersion exercise. Women had a mean diuresis of 207 ml (6.5 ml/min) during water exercise compared with 98 ml. (2.4 ml/min) during land exercise. Fetal heart rates showed a tendency toward being higher after land exercise compared with water exercise. Six of seven fetuses displayed tachycardia after land exercise compared to one of seven after water exercise. Exercise on land and during immersion at 70% VO2max was well tolerated. However, exercise during immersion offers several physiologic advantages during pregnancy.
has been described elsewhere and is included here for completeness.12 MATERIALS AND METHODS
This investigation was performed at the Exercise Physiology Laboratory of the University of North Carolina at Chapel Hill. The investigation was approved by the Committee for Research with Human Subjects. Pregnant volunteers were recruited by advertisements in the obstetric offices of the University of North Carolina School of Medicine. After a screening history and physical examination, the subjects were familiarized with the procedure and protocol and trained in the use of the bicycle ergometer and breathing mechanism. Subjects were excluded if there were any obstetric or medical contraindications to exercise. Subjects were tested between 25 and 26 weeks' gestation. Testing was performed 2 hours postprandial, in the midafternoon. All subjects completed the experiment without difficulty. The experimental protocol consisted of three sessions separated by 3 to 7 days. During the first visit, an estimation of the subjects' maximum oxygen capacity (VO2max) was obtained through incremental submaximal testing.13 Subjects performed graded
The Department of Obstetrics and Gynecology, The School of Medicine, and The Department of Physical Education, University of North Carolina, Chapel Hill, North Carolina Reprint requests: Dr. Katz, 214 MacNider Building, CB #7570, The Department of Obstetrics and Gynecology, The University of North Carolina, Chapel Hill, NC 27599-7570 Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
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been previously reported.1-2 Essentially, the subjects breathed through a Hans Rudolph valve attached to a Parkinson Cowan gasometer to quantify minute ventilation. Expired air was collected in a mixing chamber and gases analyzed with an applied electrochemistry S-3A oxygen analyzer and a Beckman LB-2 carbon dioxide analyzer. Urine specific gravity was obtained by refractometry. Oxygen uptake, blood pressure, fetal heart rate, and maternal heart rate were analyzed using a within subjects ANOVA, comparing land and water trials across times that these variables were measured. If significance was found, p < 0.05, a post hoc Newman-Keuls test was used to assess which values created the differences. Urine volumes and specific gravity were evaluated by a dependent t test. RESULTS
The levels of exertion in the land and water trials were similar. A mean VO2 of 1.38 liters/m was obtained during immersion, compared to a mean of 1.40 liter s/m during land exercise. Maternal heart rates were greater on land than in the water (p < 0.005). Systolic blood pressures were also greater during land exercise than water exercise (p < 0.05), and diastolic blood pressures were similar. The resting values of rectal temperatures were equal, 37.2°C. After 20 minutes of exercise, the mean rectal temperature after land exercise was 37.7°C versus 37.4°C after water exercise, p < 0.05. Although statistically significant, the clinical relevance of this difference is speculative. Rectal temperatures decreased from 37.8° to 37.4°C over the 20-minute recovery period after land exercise. Temperatures after immersion exercise decreased from 37.5° to 37.2°C.There was no significant difference in rectal temperatures between land and immersion exercise during recovery, and no subject had a temperature greater than 38.0°C. Oxygen uptake, heart rate, and systolic blood pressure are listed in Table 1. Urine volumes during land and water trials were very different. The mean urine output during the land trial was 98 cc versus 261 cc during the water trial, p < 0.005. Changes in specific gravity were also quite different, p < 0.008. Subjects in the water had a mean dilution of 1.012 to 1.006 compared to a small urinary concentration from 1.013 to 1.015 during land exercise. Fetal heart rate data are listed in Table 2. Resting fetal heart rates and immediate postexercise fetal heart rates were similar between land and water trials. However, the change from rest to 5 minutes into recovery was different between the two trials (p < 0.025). The rise in fetal heart rate was 12 beats/ min on the land versus a 1 beat/min rise after the water trial. The fetal heart rates at 10, 15, and 20 minutes showed a tendency to be greater after land exercise than after water exercise (p
