Article

A Risk-Benefit Analysis of Maintaining an Aerobic-Endurance Triathlon Training Program During Pregnancy: A Review

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Abstract

Objectives Possible risks and benefits of an endurance-based triathlon training program during pregnancy were assessed. News Vigorous exercise throughout the third trimester can lower birth weight by 400 g, but other indices of fetal well-being are unaffected. Fetal heart rate increases during exercise, remaining within the normal range (120–160 beats min⁻¹). Swimming, cycling and running do not affect fetal morbidity or mortality. Performance indices such as aerobic capacity can be maintained through continuation of training. Prospects and projects Will aid the counselling of women during pregnancy. To date, no research exists regarding triathlon training during pregnancy, future studies could investigate multi-sport training whilst pregnant. Conclusion Pregnancy does not require complete cessation of triathlon training and can include each of the three sports. However, maternal heart rate (MHR) should not exceed 90% of maximal.

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... That there is still much to learn about the energetics of pregnancy is further demonstrated by the fact that some women in the third trimester of pregnancy are able to engage in rigorous endurance exercise, including training for and running marathons competitively. In fact, rigorous physical activity was even found to decrease the risk of prematurity and slightly increase gestational length (Holt & Holden, 2018;Beetham et al., 2019). There are also compensatory mechanisms that modify energy allocation in times of metabolic stress (see Dufour & Sauther, 2002). ...
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... • Uteroplasental vaskuler yetmezlik olması halinde submaksimal egzersiz bile geçici zararlı etkilere ve erken başlangıçlı İUGR'ye yol açabilir 55,56 . ...
... Notably, only one of these studies provided exercise descriptions that were considered adequate to be defined as vigorous intensity exercise. Reduced birth weight without diagnosis of SGA was also found in two other reviews [60,61]. The lower birth weight that is shown in some studies is thought to be due to reduced fetal fat deposition, rather than a reduction in lean mass [22]. ...
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Maternal-fetal effects of cycle ergometer conditioning (heart rate of 145 beats/min at 25 min/day for 3 days/wk) were studied during the second and third pregnancy trimesters. Subjects were 22 previously sedentary women and 16 nonexercising pregnant control women. Fetal heart rate (FHR) characteristics were studied before, during, and after 15 min of upright cycling at a maternal heart rate target of 145 beats/min at the end of both the second and third trimesters. Despite higher cycling power outputs in the exercised group, mean FHR responses were similar in both groups and conformed to 1) gradual increase in FHR baseline during exercise, 2) normal variability, and 3) normal reactivity. Fetal bradycardia was observed during (n = 1) and after (n = 2) exercise in three isolated tests. The timing of these events suggested that the likelihood of significant fetal hypoxia is highest in the immediate postexercise period. These results also support the hypothesis that physically conditioned women can perform at higher exercise power outputs than sedentary women without inducing fetal hypoxic stress. Further study is recommended to examine possible fetal and placental adaptations to maternal aerobic conditioning.
Article
We hypothesized that aerobically fit women who continued to exercise throughout pregnancy would have enhanced cardiorespiratory responses to exercise. Physically active (N = 10) and sedentary (N = 6) subjects were compared during steady-state (15 min) semi-recumbent cycle exercise performed at a given heart rate (HR; 140 b.min-1) twice during pregnancy (25 wk, 36 wk) and 12 wk postpartum. Indirect calorimetry was used to measure volumes and fractional concentrations of expired gases. Cardiac output was estimated via CO2 rebreathing. Data were analyzed with repeated measures ANOVA. Caloric expenditure during exercise was significantly (P < 0.001) greater in the physically active (7.2 kcal.min-1) compared with sedentary (4.7 kcal.min-1) subjects. Alveolar ventilation and cardiac output responses to exercise were proportionally greater (P < 0.001) in the aerobically fit subjects. Ventilatory equivalents for O2 and physiological dead space/tidal volume ratios were significantly (P < 0.01) lower in the physically active subjects during exercise. In contrast, ratings of perceived exertion during exercise did not differ between subject groups. It appears that a physically active woman's enhanced cardiorespiratory responses to acute exercise are maintained during pregnancy if she continues her aerobic fitness program throughout gestation.
Article
The potential risks and benefits of regular exercise during lactation have not been adequately evaluated. We investigated whether regular aerobic exercise had any effects on the volume or composition of breast milk. Six to eight weeks post partum, 33 sedentary women whose infants were being exclusively breast-fed were randomly assigned to an exercise group (18 women) or a control group (15 women). The exercise program consisted of supervised aerobic exercise (at a level of 60 to 70 percent of the heart-rate reserve) for 45 minutes per day, 5 days per week, for 12 weeks. Energy expenditure, dietary intake, body composition, and the volume and composition of breast milk were assessed at 6 to 8, 12 to 14, and 18 to 20 weeks post partum. Maximal oxygen uptake and the plasma prolactin response to nursing were assessed at 6 to 8 and 18 to 20 weeks. The women in the exercise group expended about 400 kcal per day during the exercise sessions but compensated for this energy expenditure with a higher energy intake than that recorded by the control women (mean [+/- SD], intake, 2497 +/- 436 vs. 2168 +/- 328 kcal per day at 18 to 20 weeks; P < 0.05). Maximal oxygen uptake increased by 25 percent in the exercising women but by only 5 percent in the control women (P < 0.001). There were no significant differences between the two groups in maternal body weight or fat loss, the volume or composition of the breast milk, the infant weight gain, or maternal prolactin levels during the 12-week study. In this study, aerobic exercise performed four or five times per week beginning six to eight weeks post partum had no adverse effect on lactation and significantly improved the cardiovascular fitness of the mothers.
Article
This study monitored a 34-yr-old distance runner for 16 wk immediately postparturition, as she trained for the 1992 United States Olympic Marathon Trials. Weight (WT), percent fat (%FAT), aerobic power (VO2max), and energy intake/expenditure were evaluated 4, 8, 12, and 16 wk post-parturition. WT declined steadily throughout the investigation, while %FAT decreased through the first 12 wk. Minimal changes in VO2max (4 wk; 52.2 ml.kg-1.min-1 to 16 wk: 55.3 ml.kg-1.min-1) occurred; however, there were substantial changes in oxygen uptake at the lactate threshold (VO2-LT) and at the onset of blood lactate accumulation (VO2-OBLA). VO2-LT increased from 35.6 ml.kg-1.min-1 at 4 wk to 43.5 ml.kg-1.min-1 at 8 wk. VO2-OBLA increased from 40.1 ml.kg-1.min-1 at 4 wk to 51.2 ml.kg-1.min-1 at 8 wk. VO2-LT and VO2-OBLA did not change during the final 8 wk of training. Energy intake was consistently below energy expenditure. No physical or medical complications were encountered during training. This subject was able to improve VO2-LT and VO2-OBLA through high-intensity training without compromising her health. The evidence indicates that well-trained female athletes, while under physician care, may participate in rigorous physical activity soon after pregnancy.
Article
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. 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. 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). We concluded that the hypothesis is correct and speculate that these changes represent a maturing fetal response to a reduction in Po2.
Article
To assess maternal rectal temperature and fetal heart rate responses to dynamic exercise. 11 healthy women with low risk pregnancies completed three separate upright cycling tests at 34 to 37 weeks gestation: 15 min at 62.5 W (mean maternal heart rate [MHR] 138 beats.min-1 (test A); 15 min at 87.5 W (MHR 156 beats.min-1) (test B); and 30 min at 62.5 W (MHR 142 beats.min-1) (test C). Rectal temperature and fetal heart rate were measured. Mean temperature increase after tests B and C [by 0.4(SD 0.1) degrees C] was greater than after test A [0.2(0.1) degrees C] (P < 0.001). Fetal heart rate, measured in the recovery period immediately after exercise, increased significantly only after tests B and C (P < 0.01). Exercise related changes in temperature and fetal heart rate weakly correlated in tests B (P < 0.02) and C (P < 0.01). Temperature and fetal heart rate changes were more marked after higher intensity (test B) or longer duration exercise (test C) compared with moderate exercise, but none of the tests caused adverse fetal heart rate changes (decrease in accelerations, bradycardia, or decelerations) or individual temperatures above 38 degrees C.
Article
This study was designed to assess glucose homeostasis in pregnant women in their third trimester of gestation in response to exercise. Specifically, this study was designed to (1) compare the extend and rate at which blood glucose levels decrease in pregnant (22 to 33 weeks of gestation) versus that which occurs in nonpregnant women; and (2) determine the pattern of changes of the substrates (glucose, lactate, beta-hydroxybutyrate, and free fatty acids, and hormones (insulin), that contribute to the glucose homeostasis of pregnant (N = 10), and nonpregnant (N = 10) women in response to 1-hour prolonged moderate intensity exercise (at 55% of their VO2max). Each subject was tested for the determination of their maximal oxygen consumption (VO2max) and, based on their VO2max, they performed 60 minutes of prolonged moderate intensity exercise. Blood was collected before, during, and after the exercise bout. The results indicated that blood glucose levels of pregnant women decrease at a faster rate and to a significantly lower level post exercise (P < .05). Insulin levels of pregnant women also decreased to a significantly lower level post exercise, and lactate levels were maintained at a lower level 15 minutes after exercise. beta-hydroxybutyrate level was not different between the two groups, but demonstrated a different pattern of changes during exercise (P < .05). Furthermore, the results suggest that blood glucose levels of the late pregnant women decrease lower than those of nonpregnant women; also, there are differences in the rate and kinetics of blood glucose between pregnant and nonpregnant women. The results also indicate significant differences in the level of circulating substrates and hormones between pregnant and nonpregnant women in response to exercise.
Article
Our purpose was to test the hypothesis that continuing regular exercise throughout pregnancy alters morphometric and neurodevelopmental outcome at 1 year. The offspring of 52 women who exercised were compared with those of 52 control subjects who were similar in terms of multiple prenatal and postnatal variables known to influence outcome. All women were enrolled before pregnancy and had clinically normal antenatal and postnatal courses. Neurodevelopment was assessed by blinded examiners at 1 year of age, and morphometrics were obtained at birth and at 1 year of age. At birth, the offspring of the exercising women weighed less (3.38 +/- 0.06 kg vs 3.58 +/- 0.07 kg) and had less body fat (9.5% +/- 0.8% vs 12.6% +/- 0.6%). However, at 1 year, all morphometric parameters were similar, and no clinically significant between-group differences were observed in performance on either the Bayley psychomotor (108 +/- 1 vs 101 +/- 2) or mental (120 +/- 1 vs 118 +/- 1) scales. These data indicate that the offspring of exercising mothers have normal growth and development during the first year of life.
Article
This case study reports the clinical and physiological changes of a 33 year old elite marathoner undertaking intensive endurance training during and following a twin pregnancy. Prior to conception, the subject ran 155 km x week(-1) at an intensity equivalent to 140-180 b x min(-1) which following consultation decreased to 107 +/- 19 km x week(-1) at an intensity equivalent to 130-140 b x min(-1) during pregnancy. Physical exercise ceased 3 days prior to an elective Caesarean section following a 36 week gestation period and recommenced 8 days following the birth of healthy twins. Medical assessments conducted ante/post partum indicated that both the twins and mother were healthy. A field based test demonstrated that running velocity at a steady state HR of 140 b x min(-1), 150 b x min(-1) and 160 b x min(-1) decreased by 20%, 15% and 13% respectively between weeks 1 and 32 antepartum. Whole blood lactate ([La-]B), oxygen uptake (VO2), ventilatory equivalent for oxygen (V(E)/VO2), HR and Borg rating of perceived exertion (RPE) increased during a laboratory-based submaximal treadmill test at 29 weeks antepartum in comparison to a test conducted 10 weeks post partum. These data clearly demonstrate that it is possible for an elite endurance athlete to maintain a high level of cardiovascular fitness during pregnancy with no apparent adverse effects on maternal or foetal health. This will facilitate an earlier return to international competition.
Article
Maternal training during pregnancy has been the subject for numerous investigations lately, which are presented in this survey. No studies in human beings have shown any negative effect of training on the embryogenesis. During physical training a small rise in foetal heart rate of 5-25 bpm is a common finding. This could be due to a reduction in oxygen delivery or more likely stimulation from maternal vasoactive hormones or training-induced uterine contractions. Foetal growth seems to be influenced by maternal activity, as some investigations have found significantly bigger babies born by moderately trained females compared to non-trained or heavily trained women. In the latter group the reduction could be explained by a reduced neonatal fat mass. Increased maternal temperature during training has not been found to lead to any foetal abnormalities. The results indicate that moderate training during pregnancy can be recommended with observance of simple directives.
Article
Four days after competing in an Olympic-distance National Triathlon Championship (1500-m swim, 40-km cycle, 10-km run), five male and five female triathletes underwent comprehensive physiological testing in an attempt to determine which physiological variables accurately predict triathlon race time. All triathletes underwent maximal swimming tests over 25 and 400 m, the determination of peak sustained power output (PPO) and peak oxygen uptake (VO2peak) during an incremental cycle test to exhaustion, and a maximal treadmill running test to assess peak running velocity and VO2peak. In addition, submaximal steady-state measures of oxygen uptake (VO2), blood [lactate], and heart rate (HR) were determined during the cycling and running tests. The five most significant (P < 0.01) predictors of triathlon performance were blood lactate measured during steady-state cycling at a workload of 4 W x kg(-1) body mass (BM) (r = 0.92), blood lactate while running at 15 km x h(-1) (r = 0.89), PPO (r = 0.86), peak treadmill running velocity (r = 0.85), and VO2peak during cycling (r = 0.85). Stepwise multiple regression analysis revealed a highly significant (r = 0.90, P < 0.001) relationship between predicted race time (from laboratory measures) and actual race time, from the following calculation: race time (s) = - 129 (peak treadmill velocity [km x h(-1)]) + 122 ([lactate] at 4 W x kg(-1) BM) + 9456. The results of this study show that race time for top triathletes competing over the Olympic distance can be accurately predicted from the results of maximal and submaximal laboratory measures.
Article
To evaluate the effect of immersion in water on maternal haemodynamic measures and fetal heart rate patterns in healthy nulliparous women. A randomised cross-over study. Twenty pregnant women were studied between 26-29 weeks and between 34-37 weeks of gestation. The women were either immersed in water for 35 minutes or rested on a bed for a similar period of time. Maternal blood pressure, thoracic electrical bioimpedance, urine and blood samples, and fetal heart rate patterns were obtained before and after immersion or bedrest. Compared with bedrest and pre-immersion values, immersion resulted in a significant decrease in blood pressure, which returned to baseline values within 1.5 hour. Urine production increased for a short period after immersion, but 24 hour samples showed no difference compared with bedrest. Sodium, potassium and creatinine levels in urine remained constant. No significant changes were found for the other haemodynamic measures. There were no effects on fetal heart rate nor on its variation. In healthy pregnant women immersion for 35 minutes has a clear effect on blood pressure and urine production. However, these effects are short lasting.
Article
To determine the fetal response to and safety of maximal maternal exercise in the third trimester. Twenty-three active women with uncomplicated pregnancies (singleton gestations) underwent maximal exercise testing in late gestation using a progressive maximal cycle ergometer protocol. Fetal heart rate (FHR) responses were monitored and classified using National Institute of Child Health and Human Development guidelines. Statistical analyses involved use of the Student t test, repeated measures analysis of variance with Tukey-Kramer multiple comparisons posttest, and the chi(2) test. There was an increase in baseline FHR in the 20-minute posttest period compared with the 20-minute pretest period. There were significantly fewer accelerations in the second posttest 10-minute segment compared with the second pretest 10-minute segment. Variability was reduced in both posttest periods compared with the first 10-minute pretest period. Time to reactivity increased after testing. Mild tachycardia was noted in two tracings and bradycardia occurred in a fetus with previously undiagnosed growth restriction. There were no abnormal neonatal outcomes. Maximal exercise testing in late gestation led to minimal changes in FHR. Fetal bradycardiac responses were not seen in appropriate for gestational age fetuses, suggesting that brief maximal maternal exertion for research or diagnostic purposes is safe in this group.
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Article
Many studies have documented that placental development is altered by a variety of environmental factors which alter placental bed blood flow and/or oxygen delivery. One of these is sustained weight-bearing exercise. The purpose of this investigation was to examine the effects of running throughout pregnancy on villous vascular development and cell proliferation by testing the null hypothesis that continuing a regular running regimen throughout pregnancy has no effect on villous vascular volume or cell proliferation at term. Accordingly, placentae of 11 healthy runners with uncomplicated pregnancies were matched by placental weight, maternal diet and birth weight with those of 11 healthy controls and examined using systematic random sampling and point counting of placental tissues stained immunohistochemically with either an endothelial (CD 31, PECAM-1, endoCam) or a proliferative (Ki-67, MIB-1) marker. The placentae of the runners had greater villous vascular volumes in both absolute (77 +/- 20 cm(3) versus 47 +/- 18 cm(3), p < 0.02) and relative (% of total villous volume: 29 +/- 5% versus 20 +/- 6%, p < 0.003) terms. Likewise, they had a greater proliferation index (45 +/- 14 mitoses/1000 nuclei versus 29 +/- 10 mitoses/1000 nuclei, p < 0.008). We conclude that continuing to run regularly throughout pregnancy increases both absolute and relative villous vascular volume and cell proliferation at term. We also speculate that this exercise effect may have clinical value in cases at risk for anomalous feto-placental growth as increased villous vascular volume should improve feto-placental growth by enhancing placental transfer of oxygen and diffusible substrate.
Article
The delivery of oxygen and substrate to the maternal-fetal interphase is the major maternal environmental stimulus which either up- or down-regulates feto-placental growth. During pregnancy, sustained exercise sessions cause an intermittent reduction in oxygen and substrate delivery to the interphase that may exceed 50% during the exercise but, it is probable that regular bouts of sustained exercise or exercise training may improve oxygen and substrate delivery at rest. The type of maternal carbohydrate intake (low- versus high-glycemic sources) and food intake frequency also influence substrate availability through their effects on maternal blood glucose levels and insulin sensitivity. As a result, different exercise regimens and/or different types of carbohydrate intake modify feto-placental growth. The magnitude and direction of the effect is determined by their average 24-h effect on oxygen and substrate availability at different time-points in pregnancy. In general, exercise in early and mid pregnancy stimulates placental growth while the relative amount of exercise in late pregnancy determines its effect on late fetal growth. Low-glycemic food sources in the diet decrease growth rate and size at birth while high-glycemic food sources increase it. Thus, it may be possible to improve pregnancy outcomes in both healthy, low-risk women and a variety of high-risk populaces by simply modifying maternal physical activity and dietary carbohydrate intake during pregnancy.
Article
Regular aerobic exercise during pregnancy appears to improve physical fitness, but the evidence is insufficient to infer important risks or benefits for the mother or baby. Aerobic exercise is physical activity that stimulates a person's breathing and blood circulation. The review of 14 trials, involving 1014 pregnant women, found that pregnant women who engage in vigorous exercise at least two to three times per week improve (or maintain) their physical fitness, and there is some evidence that these women have pregnancies of the same duration as those who maintain their usual activities. There is too little evidence from trials to show whether there are other effects on the woman and her baby. The trials reviewed included non-contact exercise such as swimming, static cycling and general floor exercise programs. Most of the trials were small and of insufficient methodologic quality, and larger, better trials are needed before confident recommendations can be made about the benefits and risks of aerobic exercise in pregnancy.
Article
This study assessed if upright cycling is preferable to semi-recumbent cycling during pregnancy. Healthy women with low risk singleton pregnancies were tested at 34-38 weeks gestation. They cycled for 12 min, either semi-recumbent (45 degrees, n = 27) or upright (n = 23), at 135-145 beats min(-1). When semi-recumbent, minute ventilation was greater (p<0.03) at rest and systolic blood pressure and pulse pressure were greater during exercise (p<0.05). Exercise maternal heart rate, oxygen consumption, oxygen consumption per kilogram, minute ventilation, cardiac output, stroke volume, mean and diastolic blood pressures and arterio-venous oxygen difference were posture-independent. All increased with exercise (p<0.01), except stroke volume when semi-recumbent (p>0.05). Small post-exercise fetal heart rate increases (by 8 beats min(-1), p<0.05) were similar in both postures (n = 11 in each sub-group), with no adverse changes. Fetal heart rate accelerations and uterine activity (n = 11 in each sub-group) were not influenced by posture or exercise. (1) Neither posture had a distinct advantage. (2) Both postures were safe for short duration cycling. (3) The same target maternal heart rates are suitable for both postures because they resulted in similar oxygen consumptions and fetal heart rates.
Article
Pregnant women usually acknowledge and more or less accept symptoms of urinary frequency, nocturia, and leakage as annoying aspects of pregnancy that are expected to resolve when the pregnancy is over. Studies have shown that urinary symptoms may be more than just "annoying" - the symptoms can markedly reduce quality of life. This article provides an overview of the lower urinary tract during pregnancy, including considerations of symptoms of urinary frequency; nocturia and incontinence; changes in bladder support; and the occurrence of urinary retention, a urologic emergency.
Article
Human pregnancy is characterized by significant increases in ventilatory drive both at rest and during exercise. The increased ventilation and attendant hypocapnia of pregnancy has been attributed primarily to the stimulatory effects of female sex hormones (progesterone and estrogen) on central and peripheral chemoreflex drives to breathe. However, recent research from our laboratory suggests that hormone-mediated increases in neural (or non-chemoreflex) drives to breathe may contribute importantly to the hyperventilation of pregnancy. This review challenges traditional views of ventilatory control, and outlines an alternative hypothesis of the control of breathing during human pregnancy that is currently being tested in our laboratory. Conventional wisdom suggests that pregnancy-induced increases in central respiratory motor output command in combination with progressive thoraco-abdominal distortion may compromise the normal mechanical response of the respiratory system to exercise, increase the perception of exertional breathlessness, and curtail aerobic exercise performance in otherwise healthy pregnant women. The majority of available evidence suggests, however, that neither pregnancy nor advancing gestation are associated with reduced aerobic working capacity or increased breathlessness at any given work rate or ventilation during exhaustive weight-supported exercise.