Exercise and Pregnancy

26 Pages·2011·1.97 MB·English

In This Chapter
Benefits and Risks of Exercise
During Pregnancy
Maternal Fitness
Gestational Diabetes
Preeclampsia
Maternal Obesity
Maternal Exercise and the Fetal
Response
Contraindications and Risk Factors
Physiological Changes During
Pregnancy
Musculoskeletal System
Cardiovascular System
Respiratory System
Thermoregulatory System
Programming Guidelines and
Considerations for Prenatal Exercise
Biomechanical Considerations for
the Pregnant Mother
Low-back and Posterior Pelvic Pain
Pubic Pain
Carpal Tunnel Syndrome
A b o u t T h e A u t h o r
Diastasis Recti
Stress Urinary Incontinence Sabrena Merrill, M.S., has been actively involved in the fitness
Nutritional Considerations
industry since 1987. An ACE-certified Group Fitness Instructor
Psychological Considerations
and Personal Trainer, Merrill teaches group exercise, owns and
Benefits and Risks of Exercise
Following Pregnancy operates her own personal training business, has managed
Physiological Changes Following fitness departments in commercial facilities, and lectured to
Pregnancy
university students and established fitness professionals. She
Programming Guidelines and
Considerations for Postnatal has a bachelor’s degree in exercise science as well as a master’s
Exercise
degree in physical education from the University of Kansas, and
Biomechanical Considerations for
the Lactating Mother has numerous certifications in exercise instruction. Merrill acts
Case Study
as a spokesperson for the American Council on Exercise (ACE)
Summary
and is involved in curriculum development for ACE continuing
education programs. Additionally, Merrill presents lectures and
workshops to fitness professionals nationwide.
C hApTe r 2 3
Pre- and Postnatal Exercise
Sabrena Merrill
An increasing amount of research on exercise in pregnancy has led to a waning
debate over the maternal and fetal risks of regular physical activity during
pregnancy. There is a growing trend of women entering pregnancy with regu-
lar aerobic and strength-conditioning activities as a part of their daily routines. Many
women who are not physically active view pregnancy as a time to modify their lifestyles
to include more health-conscious activities, including exercise.
Traditionally, the medical community has encouraged pregnancy (Zhang & Savits, 1996; Ning et al., 2003). Given
pregnant women to reduce their habitual levels of physical the current epidemic of obesity and its associated comorbidi-
exertion and refrain from starting strenuous exercise pro- ties, as well as the apparent health risks of not exercising,
grams. These restrictive guidelines were based on concerns fitness professionals who are competent to work with this
that exercise could negatively affect pregnancy outcomes population can provide safe and effective exercise program-
by increasing core body temperature, raising the risk of
ming to promote a healthy pregnancy and healthy lifestyle
congenital anomalies, and shifting oxygenated blood and
after the birth.
nutrients to maternal skeletal muscles—and away from the
Benefits and Risks of Exercise
fetus [American College of Obstetricians and Gynecologists
(ACOG), 1985; Shangold, 1989]. More recent investiga- During Pregnancy
tions, however, focusing on both aerobic training and strength
conditioning in pregnancy, have shown no increase in early E
vidence is increasing that regular prenatal exercise
pregnancy loss, late pregnancy complications, abnormal fetal
is an important component of a healthy pregnancy.
growth, or adverse neonatal outcomes, suggesting that previ-
Expectant mothers can maintain or even improve
ous recommendations have been overly conservative (Clapp,
cardiovascular and muscular fitness. Additionally, regular
1989; Klebanoff et al., 1990; Hatch et al., 1993; Kardel et al.,
exercise is associated with a lower incidence of excessive
1998; Sternfeld et al., 1995; O’Neill, 1996).
maternal weight gain, gestational diabetes mellitus (GDM),
While prenatal exercise recommendations from allied
pregnancy-induced hypertension, varicose veins, deep vein
healthcare professionals are becoming more commonplace,
the majority of women do not get the recommended mini- thrombosis, dyspnea, and low-back pain (Davies et al., 2003;
mum amount of daily physical activity. It is estimated that Weissgerber et al., 2006). Furthermore, it has been shown
only 42% of pregnant women exercise 30 minutes or more that women who continue regular, weightbearing exercise
at least three times a week, and 23% of healthy, previously throughout the entire duration of pregnancy tend to have
active women stop exercise or reduce it significantly during easier, shorter, and less complicated deliveries (Clapp, 2002).
576 Chapter twenty-three Pre- and Postnatal Exercise
Maternal Fitness considered an adjunct therapy for women with
Healthy women who consistently exercise GDM. Preliminary studies have found that women
throughout pregnancy show a marked reduction who participated in any type of recreational activ-
in weight gain, fat accumulation, and fat reten- ity within the first 20 weeks of gestation decreased
tion. In one study, pregnant exercisers had average their risk of GDM by almost half (Dempsey et al.,
increases in weight (29 pounds; 13 kg) and skin- 2004). Research has shown that even mild exercise
•
fold thicknesses (10 mm) well within the normal (30% of v Omax, regardless of modality) com-
2
range, but their body-fat mass averaged 3% lower bined with nutritional control can help prevent
than the control subjects who performed no exer- GDM and excessive weight gain during pregnancy
cise during pregnancy (Clapp & little, 1995). In (Batada et al., 2003).
other words, the women who performed regular
weightbearing exercise throughout their pregnan- Preeclampsia
cies maintained a leaner body composition than A serious maternal-fetal disease called pre-
their sedentary counterparts. eclampsia is diagnosed after 20 weeks of gestation
Due to the many physiological adaptations that and characterized by persistent hypertension
occur during pregnancy, women who continue (>140/90 mm/Hg) and proteinuria (24-hour
moderate-to-high levels of endurance exercise can urinary protein level ≥0.3 g) (ACOG, 2002a).
experience an increase in their maximal aerobic Complications associated with preeclampsia
capacity by up to 10% postpartum, even though include preterm birth, abruptio placentae, renal
exercise volume is typically reduced by the added failure, pulmonary edema, cerebral hemorrhage,
responsibility of childcare (Clapp & Capeless, circulatory collapse, eclampsia, and the necessity
1991). Furthermore, improvements in aerobic for immediate delivery regardless of gestational
•
efficiency, but not necessarily V Omax, are seen in age. Risk factors for preeclampsia include abnor-
2
women who begin a low-volume exercise program mal placental development, predisposing maternal
(moderate intensity for 20 minutes, three to five constitutional factors, oxidative stress, immune
days per week) during pregnancy (Clapp, 2002). maladaptation, and genetic susceptibility.
A review of the literature examining physi-
Gestational Diabetes cal activity and preeclampsia risk reveals several
Glucose intolerance that is first recognized or epidemiological studies that indicate that regular
diagnosed during pregnancy is called gestational leisure-time physical activity in early pregnancy
diabetes. Maternal muscular insulin resistance is associated with a reduced incidence of pre-
during mid-pregnancy is a normal response to hor- eclampsia (Weissgerber et al., 2004). Although
monal adaptations that occur to ensure adequate not proven, several protective mechanisms associ-
glucose regulation for fetal growth and develop- ated with exercise are thought to play a role in
ment. In women with GDM, this insulin increase is preeclampsia prevention, including enhanced
exacerbated, resulting in maternal hyperglycemia. placental growth and vascularity, enhanced anti-
Women with GDM are more likely to have com- oxidant defense systems, reduction of the systemic
plications such as a difficult labor and delivery, as inflammatory response, and improved endothelial
well as delivery by Caesarean section (C-section). function (Weissgerber et al., 2006).
Risk factors for GDM include a family history Traditional treatment of gestational hyperten-
of diabetes, previous diagnosis of GDM, belonging sion and mild preeclampsia has focused on bed
to a high-risk ethnic group (Aboriginal, Hispanic, rest to prevent blood pressure increases associated
South Asian, Asian, or African descent), age ≥35 with daily activity. However, up to one-third of
years, overweight [body mass index (BMI) ≥25], women fail to comply with bed rest recommenda-
obesity (BMI ≥30), or a history of insulin resistance tions, and compliance does not affect pregnancy
(ACOG, 2001). Once diagnosed, GDM patients outcome in women who develop mild preeclamp-
are primarily treated through nutritional manage- sia in the latter part of gestation (Magee, Ornstein,
ment by a registered dietician (R.D.). Exercise is & von Dadelszen, 1999). More recent treatment
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Pre- and Postnatal Exercise Chapter twenty-three 557777
guidelines for hypertension and mild preeclampsia delivery. Exercise performed before conception
have shifted toward ambulatory management and during pregnancy may help to prevent these
with careful patient monitoring (lenfant, 2001; obesity-related complications by decreasing
Moutquin et al., 1997). Exercise intervention BMI to a healthy range, preventing GDM and
studies in women with gestational hypertension preeclampsia, and reducing the likelihood of
and preeclampsia are inconclusive, and it remains excessive gestational weight gain. Prenatal exercise
unclear whether a program of regular exercise also has been associated with a timely return to
can positively affect this population. Exercise in pre-pregnancy weight after delivery (Rooney &
women with high-risk pregnancy conditions, such Schauberger, 2002).
as preeclampsia, should be closely monitored and
supervised by their physicians in a clinical setting, Maternal Exercise and
as these situations are outside the scope of prac- the Fetal Response
tice for an ACE-certified Advanced Health & In uncomplicated pregnancies, fetal injuries are
Fitness Specialist (ACE-AHFS). highly unlikely, as most of the potential fetal risks
are hypothetical. However, there are several areas
Maternal Obesity of theoretical concern surrounding maternal exer-
In the u.S., the percentage of women of child- cise and its effects on the fetus. First, the selective
bearing age (20 to 39 years) who are overweight redistribution of blood flow away from the fetus
has climbed to 49% among white women and during regular or prolonged exercise in pregnancy
70% among African-American women (Okosun may interfere with the transplacental transport of
et al., 2004). Obesity-related reproductive com- oxygen, carbon dioxide, and nutrients. To address
plications that occur before, during, and after this concern, many experts recommend aquatic
pregnancy may be reduced through lifestyle inter- exercise as an excellent choice of aerobic training
ventions such as regular aerobic exercise. during pregnancy. During immersion, women
Ovulatory infertility increases progressively with experience a smaller decrease in plasma volume as
increasing BMI, as do the risks for polycystic ovar- compared to exercising on land. In addition, as a
ian syndrome and menstrual irregularities. The result of the hydrostatic pressure in aquatic exer-
effectiveness of regular aerobic exercise (three hours cise, maintenance of blood flow around the central
per week) and educational seminars (one hour per organs may provide better maintenance of uterine
week on weight-related topics) on restoring fertility and placental blood flow (Watson et al., 1991).
in obese women was demonstrated by a six-month A second concern is that during exercise, tran-
lifestyle intervention study (Clark et al., 1998). The sient hypoxia could result in fetal tachycardia
subjects who completed the intervention lost an and an increase in fetal blood pressure. These
average of 10.2 4.3 kg (22.4 9.5 lb). Prior to the fetal responses are protective mechanisms that
study, all subjects had been infertile for at least two occur during obstetric events and allow the fetus
years; however, 77% of the subjects conceived suc- to facilitate the transfer of oxygen and decrease
cessfully during or after the lifestyle intervention. the carbon dioxide tension across the placenta.
The authors hypothesized that improved fertility However, there are no reports to link such adverse
resulted from the beneficial effects of reduced insu- events with maternal exercise. A majority of
lin resistance and lower insulin concentrations on studies examining fetal responses to exercise moni-
reproductive hormone profiles. tored fetal heart rate as an indicator of fetal stress
During pregnancy, the risk of maternal and fetal (Collings, Curet, & Mullin, 1983; Clapp, 1985;
complications increases with the degree of obesity. Artal, 1990; Carpenter et al., 1988; Wolfe et al.,
The incidence of preeclampsia and GDM increase 1988). Most of these studies show a minimum
progressively in overweight and obese women. or moderate increase in fetal heart rate by 10 to
Additionally, overweight and obese women are 30 beats per minute over baseline during or after
more likely to deliver large-for-gestational-age maternal exercise. Fetal heart rate decelerations
infants and require C-section and instrumental and bradycardia, with a frequency of 8.9%, have
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578 Chapter twenty-three Pre- and Postnatal Exercise
also been reported to occur during maternal 2003). However, it is recommended that women
exercise. The causes of the alterations in fetal with complicated pregnancies be discouraged
heart rate during maternal exercise are still from participating in exercise activities for fear of
unclear, and no associated lasting effects on the impacting the underlying disorder or maternal or
fetus have been reported. fetal outcomes.
A third concern is intrauterine growth restric- ACOG has established that there are some
tion due to strenuous physical activity. Studies women for whom exercise during pregnancy is
on the effect of exercise during pregnancy absolutely contraindicated (Table 23-1), while
and resultant birth weights are inconclusive. for other women the potential benefits of exer-
Epidemiological studies have shown a link cising may outweigh the risks (Table 23-2).
between strenuous physical activity, poor diet, Furthermore, fitness professionals and preg-
and low birth weight. It has also been reported nant exercisers should familiarize themselves
that mothers who perform strenuous physical with specific signs or symptoms that may indi-
work in their occupations, such as repetitive lift- cate a problem, including those items listed in
ing, have a tendency to deliver earlier and have Tables 23-3 and 23-4. It is imperative that an
small-for-gestational-age infants (Naeye & Peters, ACE-AHFS perform routine health screenings
1982; launer et al., 1990; McDonald et al., 1988). on all clients and require a physician’s clearance
However, other studies have provided conflicting before initiating an exercise program with a
data suggesting that other variables, such as inef- pregnant or postpartum woman.
ficient nutrition, have to be present for strenuous In general, participation in a wide range of rec-
activities to affect fetal growth (Saurel-Cubizolles reational activities appears safe during and after
& Kaminski, 1987; Ahlborg Bodin, & Hogstedt, pregnancy. Overly vigorous activity in the third
1990). Overall, it appears that birth weight is not trimester, activities that have a high potential for
affected by exercise in women who have adequate contact, and activities with a high risk of falling
energy intake. should be avoided (Table 23-5). Additionally,
women should refrain from activities with a
Contraindications and Risk Factors risk of abdominal trauma, exertion at altitude
Research from the past several decades has greater than 6000 feet (1829 m), and scuba diving
produced valid and reliable evidence that supports (ACOG, 2002b).
participation in a regular exercise program during
Table 23-1
pregnancy because of the important maternal-
Absolute Contraindications to
fetal benefits it provides. In fact, the available Aerobic Exercise During Pregnancy
studies show that adverse pregnancy or neonatal
outcomes are not increased for exercising women • Hemodynamically significant heart disease
• Restrictive lung disease
(Clapp, 1989; Hall & Kaufmann, 1987; Hatch et
• Incompetent cervix/cerclage
al., 1993; Klebanoff et al., 1990; Kulpa, White, &
• Multiple gestation at risk for premature labor
visscher, 1987). ACOG, the American College
• Persistent second- or third-trimester
of Sports Medicine (ACSM), the Canadian bleeding
Society for Exercise Physiology (CSEP), and the • Placenta previa after 26 weeks of gestation
Society of Obstetricians and Gynaecologists of • Premature labor during the current
pregnancy
Canada (SOGC) all provided guidelines and
• Ruptured membranes
recommendations for exercise during pregnancy
• Preeclampsia/pregnancy-induced
and the postpartum period that indicate that,
hypertension
in uncomplicated pregnancies, women with or

without a previously sedentary lifestyle should be Source: American College of Obstetricians and
encouraged to participate in aerobic and strength- Gynecologists (2002). Exercise during pregnancy and the
postpartum period. ACOG Committee Opinion No. 267.
conditioning exercises as part of a healthy lifestyle
Obstetrics and Gynecology, 99, 171–173.
(ACSM, 2010; ACOG, 2002b; SOGC & CSEP,
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Pre- and Postnatal Exercise Chapter twenty-three
Table 23-2 Table 23-4
Relative Contraindications to Warning Signs to Cease
Aerobic Exercise During Pregnancy Exercise While Pregnant
• Vaginal bleeding
• Severe anemia
• Dyspnea prior to exertion
• Unevaluated maternal cardiac arrhythmia • Dizziness
• Chronic bronchitis • Headache
• Chest pain
• Poorly controlled type 1 diabetes
• Muscle weakness
• Extreme morbid obesity
• Calf pain or swelling (need to rule out
• Extreme underweight (BMI <12) thrombophlebitis)
• Preterm labor
• History of extremely sedentary lifestyle
• Decreased fetal movement
• Intrauterine growth restriction in current
• Amniotic fluid leakage
pregnancy

• Poorly controlled hypertension Source: American College of Obstetricians and
Gynecologists (2002). Exercise during pregnancy and the
• Orthopedic limitations
postpartum period. ACOG Committee Opinion No. 267.
• Poorly controlled seizure disorder Obstetrics and Gynecology, 99, 171–173.
• Poorly controlled hyperthyroidism
Table 23-5
• Heavy smoker
High-risk Exercises
Source: American College of Obstetricians and
Gynecologists (2002). Exercise during pregnancy and the • Snow- and waterskiing
postpartum period. ACOG Committee Opinion No. 267. • Rock climbing
Obstetrics and Gynecology, 99, 171–173.
• Snowboarding
• Diving
• Scuba diving
• Bungee jumping
Table 23-3
Reasons to Discontinue • Horseback riding
Exercise and Seek Medical Advice • Ice skating/hockey
• Road or mountain cycling
• Any sign of bloody discharge from the vagina • Vigorous exercise at altitude
(non-acclimated women)
• Any “gush” of fluid from the vagina
(premature rupture of membranes)
Note: Risk of activities requiring balance is relative to
maternal weight gain and morphologic changes; some
• Sudden swelling of the ankles, hands, or face
activities may be acceptable early in pregnancy but risky
(possible preeclampsia)
later on.
• Persistent, severe headaches and/or visual
disturbances (possible hypertension) Physiological Changes
• Unexplained spell of faintness or dizziness
During Pregnancy
• Swelling, pain, and redness in the calf of one
leg (possible phlebitis) During pregnancy, a woman’s endocrine
• Excessive fatigue, palpitations, or chest pain system signals changes in virtually every
part of her body to prepare her and the
• Persistent contractions (more than six to
eight per hour) that may suggest onset of fetus for gestation, delivery, and lactation. This
premature labor section covers the adaptations related to exercise
performance. understanding these factors and
Source: American College of Sports Medicine (2010).
how they impact a woman’s ability to engage in
ACSM’s Guidelines for Exercise Testing and Prescription
(8th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams prenatal physical activity is essential for safe and
& Wilkins. effective exercise programming.
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580 Chapter twenty-three Pre- and Postnatal Exercise
Musculoskeletal System nausea, fatigue, cravings, constipation, bloating,
With the average weight gain during preg- and frequent urination), these hormonal changes
nancy in the range of 25 to 40 pounds (11 to result in an increase in the elasticity and volume
18 kg) (15 to 25% of pre-pregnancy weight), of the entire circulatory system (i.e., a decrease in
forces across joints are significantly increased. systemic vascular resistance). Initially, this creates
Such large forces may cause discomfort to a vascular “underfill” problem where the amount
normal joints and increase damage to arthritic of blood returning to the heart decreases. To
or previously unstable joints. A woman’s enlarg- correct the underfill, the body triggers the release
ing abdomen increases the mechanical stress of several hormones, which cause a decrease in
on the joints of the back, pelvis, hips, and legs the excretion of salt and water by the kidneys.
as her center of gravity moves upward and out. ultimately, the retained extra salt and water
Because of these anatomical changes, pregnant expand plasma volume, allowing more venous
women report a high incidence of low-back pain return to the heart, thereby increasing cardiac
(up to 76%). (Brynhildsen, 1998; Kristiansson, output and improving arterial pressure and
Svardsudd, & von Schoultz, 1996). blood flow to the organs. Eventually, hormonal
During the first trimester, increased amounts signals cause increases in heart volumes (cham-
of the hormones relaxin and progesterone are ber volume and stroke volume), blood volume,
released to expand the uterine cavity. These hor- heart rate, and cardiac output.
mones allow expansion by softening the ligaments By mid-pregnancy, cardiac outputs are 30 to 50%
surrounding the joints of the pelvis (hips and lum- greater than before pregnancy (Morton, 1991).
bosacral spine), thereby increasing mobility and Additionally, maternal stroke volume increases
joint laxity. Whether or not joint laxity occurs in by 10% by the end of the first trimester, and is
other joints, such as the neck, shoulder, or periph- followed by a 20% increase in heart rate during
ery, is unclear. Theoretically, increased mechanical the second and third trimesters (Pivaranik, 1996;
stress combined with joint laxity would predispose Morton et al., 1985). Maternal resting heart rate
pregnant women to increased incidence of strains can be up to 15 beats per minute higher than pre-
and sprains. However, with the exception of the pregnancy rates near the third trimester. Mean
reporting of low-back pain, data on the effects arterial pressure decreases 5 to 10 mmHg by the
of increased weight of pregnancy on joint injury middle of the second trimester before gradually
and pathology are lacking. While an increased increasing back to pre-pregnancy levels. These
incidence of falling during pregnancy has not been hemodynamic changes appear to establish a circu-
reported, a woman’s balance may be affected by latory reserve necessary to provide nutrients and
changes in posture, predisposing her to loss of bal- oxygen to both mother and fetus at rest and during
ance and increased risk of falling. Despite a lack moderate exercise. Since heart-rate response among
of clear evidence that musculoskeletal injuries are pregnant exercisers is variable, ratings of perceived
increased during pregnancy, these possibilities exertion (RPE) should be used to assess intensity
should be considered when designing prenatal instead of traditional heart rate–based methods.
exercise programs. As pregnancy progresses, a woman’s body posi-
tion can affect her cardiovascular system both at
Cardiovascular System rest and during exercise. After the first trimester,
During pregnancy, the entire cardiovascular the supine position results in relative obstruction
system experiences dramatic changes as hor- of venous return, and therefore decreased cardiac
monal signals initiate relaxation and reduced output. For this reason, supine positions should
responsiveness in most, if not all, of the smooth be avoided as much as possible during rest and
muscle cells in a woman’s blood vessels. In addi- exercise. In addition, motionless standing is associ-
tion to causing many of the unpleasant early ated with a significant decrease in cardiac output.
symptoms of pregnancy (e.g., lightheadedness, Therefore, this position should be avoided.
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Pre- and Postnatal Exercise Chapter twenty-three
Respiratory System of 1.5° C during the first 30 minutes of exercise,
The delivery of oxygen to the mother and and then reaches a plateau if exercise is continued
fetus is enhanced through improvements in lung for an additional 30 minutes (Soultanakis, Artal,
function during pregnancy. At rest, an increase & Wiswell, 1996). If heat production exceeds
in the depth of each breath increases the amount heat dissipation capacity, as is commonly the
of air inhaled by up to 50% or more (Prowse & case during exercise in hot, humid conditions or
Gaensler, 1965; Artal et al., 1986). This increase is during very high-intensity exercise, a woman’s
the result of elevated levels of progesterone, which core temperature will continue to rise. During
stimulates “overbreathing” by increasing the prolonged exercise, loss of fluid as sweat may
brain’s sensitivity to carbon dioxide. As a result, compromise heat dissipation. Given that fetal
oxygen tension is increased and carbon dioxide body core temperatures are naturally about 1° C
tension is decreased in the alveoli. ultimately, higher than maternal temperatures, maintenance
these directional changes in breathing gases widen of proper hydration, and therefore blood volume,
the pressure gradients, which improve the effi- is critical to heat balance. Research examining
ciency of oxygen uptake from the lungs and the the effects of exercise on core temperature during
elimination of carbon dioxide from maternal and pregnancy is limited. The results of some human
fetal blood and tissues. studies suggest that hyperthermia in excess of
Prenatal adaptations of the respiratory system 39° C (100° F) during the first 45 to 60 days
cause women to experience an associated increase of gestation may be teratogenic in humans
in oxygen uptake and a 10 to 20% increase in base- (Milunsky et al., 1992; Edwards, 1986). However,
line oxygen consumption (Pivarnik et al., 1992; there have been no reports that hyperthermia
Sady et al., 1989). Peak ventilation and maximal associated with exercise causes malformations of
aerobic capacity are maintained during pregnancy. the embryo or fetus in humans.
As a result of this maintained function and the
pregnancy-induced increase in alveolar ventila-
Programming Guidelines
tion, gas transfer at the tissue level may improve.
and Considerations for
This causes a “training effect” of pregnancy in
women who maintain moderate-to-intense exer- Prenatal Exercise
cise programs throughout gestation, and may
E
explain anecdotal reports of women who experi- xercise programming guidelines for pre-
ence an improvement in competitive endurance natal activity include the same elements
performance after giving birth. as guidelines for non-pregnant women.
Aerobic exercise consisting of any activity that
Thermoregulatory System uses large muscle groups in a continuous rhythmic
A woman’s ability to dissipate heat improves manner (e.g., walking, hiking, jogging/running,
during pregnancy. The improved ability to elimi- aerobic dance, swimming, cycling, rowing, danc-
nate body heat is most likely due to a decrease ing, and rope skipping) may be appropriate. Some
of the body’s set point for normal temperature activities, such as scuba diving and prolonged exer-
in early pregnancy and a significant increase in tion in the supine position, should be avoided due
blood flow to the skin, which increases the rate to the potential for fetal hypoxia. Activities that
of heat loss directly into the air. Additionally, increase the risk of falls, such as skiing, or those
a 40 to 50% increase in tidal volume allows a that may result in excessive joint stress, such as
pregnant woman to increase heat loss through jogging and tennis, should be engaged in only after
exhalation by 40 to 50%. evaluation and consultation with a physician.
During moderate-intensity aerobic exercise Musculoskeletal conditioning appears to be safe
in thermoneutral conditions, the core tempera- and effective during pregnancy when low weights
ture of non-pregnant women rises an average and multiple repetitions through a dynamic,
ACE ADvANCED HEAlTH & FIT NESS SPECIAlIST MANuAl
582 Chapter twenty-three Pre- and Postnatal Exercise
controlled range of motion are performed. stating that the mode, frequency, duration, and
While research is lacking, it would be prudent overload principles for cardiorespiratory, resis-
to limit repetitive isometric or heavy-resistance tance, and flexibility exercise are the same for
weightlifting, as well as any exercises that result pregnant women as for non-pregnant women.
in a large pressor response (i.e., a dispropor- According to ACSM, pregnancy-specific issues
tionate rise in heart rate during resistance to consider when designing prenatal exercise
training resulting from autonomic nervous programs focus on attaining additional calories
system reflex activity). Additionally, mainte- to maintain homeostasis, avoiding motionless
nance of normal joint range of motion through standing, preventing maternal hyperthermia
individualized stretching exercises is acceptable. and hypoglycemia, and avoiding high-risk
However, pregnant exercisers should be aware exercises (Table 23-6). Furthermore, the sole
of increased ligamentous laxity and strive to use of heart-rate monitoring to assess exercise
limit excessive stretching or ballistic stretching intensity is not recommended for pregnant
movements during pregnancy. exercisers due to the natural physiological
Several national health and medical organiza- influences of the cardiovascular system during
tions have published recommendations and pregnancy. The “category” RPE scale (6–20)
guidelines on exercise and pregnancy (ACOG, or the “category-ratio” Borg scale (0–10) may
2002b; ACSM, 2010; SOCG & CSEP, 2003). be used. Ratings of “fairly light” to “somewhat
Not surprisingly, the content in the guidelines hard” are the recommended intensity ranges for
from the different organizations is similar. prenatal exercise (Pivernak et al., 1991; Clapp,
Specifically, the ACOG Committee Opinion lopez, & Harcar-Sevcik, 1999).
on exercise during pregnancy published in 2002 Another set of guidelines, jointly sponsored
recommends that, barring medical or obstetric by SOGC and CSEP, promote similar recom-
contraindications, pregnant women engage mendations as those set forth by ACSM and
in 30 or more minutes of moderate exercise ACOG, with the addition of a modified ver-
on “most” days of the week (ACOG, 2002b). sion of the conventional age-corrected heart
This recommendation is essentially the same rate target zone for pregnant exercisers (Table
as that made for the general population by the 23-7), and a recommendation for resistance
CDC and ACSM (ACSM, 2010). ACOG exercise and aerobic exercise (SOGC/CSEP,
and ACSM jointly support recommendations 2003). Furthermore, the SOGC/CSEP
Table 23-6
Special Considerations for Prenatal Exercise Programming
• Pregnancy requires an additional 300 calories per day to maintain homeostasis. Therefore,
women should ingest additional calories to meet the needs of exercise and pregnancy.
• Heat dissipation is important throughout pregnancy. Appropriate clothing, environmental
considerations, and adequate hydration should be priorities during the exercise program
to prevent the possibility of hyperthermia and the corresponding risk to the fetus. Pregnant
women should drink ample water to prevent dehydration and avoid brisk exercise in hot,
humid weather or when suffering with a fever.
• Pregnant women should avoid exercise that involves the risk of abdominal trauma, falls, and
excessive joint stress. Sport activities such as softball, basketball, and racquet sports are not
recommended because of the increased risk of abdominal injury. When exercising, pregnant
women should be aware of the signs and symptoms for discontinuing exercise and seeking
medical advice (see Table 23-3).
Source: American College of Sports Medicine (2010). ACSM’s Guidelines for Exercise Testing and Prescription (8th ed.).
Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins.
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Pre- and Postnatal Exercise Chapter twenty-three
position statement provides a plan for inactive Table 23-7
women to gradually increase their activity level Modified Heart Rate Target Zones for Aerobic Exercise in Pregnancy
(i.e., previously sedentary women should begin
with 15 minutes of continuous exercise three Maternal Age Heart Rate Target Zone Heart Rate Target Zone
(beats/min) (beats/10 seconds)
times a week, increasing gradually to 30-minute
Less than 20 140–155 23–26
sessions four times a week). Table 23-8 pres-
20–29 135–150 22–25
ents the joint recommendations of SOGC and
30–39 130–145 21–24
CSEP for exercise in pregnancy and the post-
40 or greater 125–140 20–23
partum period.
Note: The most appropriate use of these modified heart rate guidelines is in conjunction with
Biomechanical RPE, as blunted, exaggerated, and normal linear responses to exercise have been observed
at different stages during pregnancy.
Considerations for the
Source: Society of Obstetricians and Gynaecologists of Canada (SOGC) & Canadian
Pregnant Mother
Society for Exercise Physiology (CSEP) (2003). Joint SOGC/CSEP clinical practice guideline:
Exercise in pregnancy and the postpartum period. Journal of Obstetrics and Gynaecology
D Canada, 25, 6, 516–522.
ue to the wide range of postural and
physiological adaptations that occur
during pregnancy, the ACE-AHFS must Table 23-8
be proficient at designing exercise programs geared Recommendations for Exercise in Pregnancy and the
Postpartum Period
toward making physical activity more comfort-
able for this population. Physiological adaptations
• All women without contraindications should be encouraged to
include a profound increase in body mass, reten-
participate in aerobic and strength-conditioning exercises as part
tion of fluid, and laxity in supporting structures.
of a healthy lifestyle during their pregnancy.
Postural adaptations correspond with these physi-
• Reasonable goals of aerobic conditioning in pregnancy should
ological changes and usually entail an alteration in
be to maintain a good fitness level throughout pregnancy without
the loading and alignment of, and muscle forces
trying to reach peak fitness or train for an athletic competition.
along, the spine and weightbearing joints. During
• Women should choose activities that will minimize the risk of loss
pregnancy, production of the hormone relaxin
of balance and fetal trauma.
increases tenfold. The hormone creates joint
• Women should be advised that adverse pregnancy or neonatal
laxity, which not only allows the pelvis to accom-
outcomes are not increased for exercising women.
modate the enlarging uterus, but also weakens the
• Initiation of pelvic floor exercises in the immediate postpartum
ability of static supports in the lumbar spine to
period may reduce the risk of future urinary incontinence.
withstand shearing forces. In the pelvis, joint laxity
is most prominent in the symphysis pubis and the • Women should be advised that moderate exercise during lactation
does not affect the quantity or composition of breast milk or
sacroiliac joints.
impact infant growth.
Typically, it is thought that advancing preg-
nancy produces a forward shift in the center of Validation: This guideline has been approved by the Society of Obstetricians and
Gynaecologists of Canada (SOGC) Clinical Practice Obstetrics Committee, the Executive
gravity followed by an anterior pelvic tilt and sub-
and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise
sequent increase in lumbar lordosis and thoracic Physiology (CSEP).
kyphosis. However, research on postural changes Sponsors: This guideline has been jointly sponsored by the SOGC and the CSEP.
associated with prenatal weight gain does not
Source: Society of Obstetricians and Gynaecologists of Canada (SOGC) & Canadian
confirm this line of thinking (Perkins, Hammer, Society for Exercise Physiology (CSEP) (2003). Joint SOGC/CSEP clinical practice
& loubert, 1998; Dumas et al., 1995; Moore, guideline: Exercise in pregnancy and the postpartum period. Journal of Obstetrics and
Gynaecology Canada, 25, 6, 516–522.
Dumas, & Reid, 1990). After the first trimester,
the uterus can no longer be contained within the
pelvis and moves superiorly and anteriorly. As lumbar lordosis; however, studies have shown that
pregnancy progresses, the biomechanical altera- the lordosis remains the same or increases only
tions of increased abdominal girth and weakened slightly (Hummel, 1987). Instead, it appears that
abdominal muscles were thought to increase the entire spine shifts to a more posterior position
ACE ADvANCED HEAlTH & FIT NESS SPECIAlIST MANuAl