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Exercise and Pregnancy
 Exercise
and pregnancy?
I'm approached regularly by clients who are pregnant or trying to
become pregnant, but are concerned that they'll have to curtail their
gym or exercise program as they get larger. They ask me "Will
exercises harm the baby?", "Can exercise possibly induce
premature labour?", "Could I injury myself?", "Which exercises should I
do?" Every woman and every pregnancy is completely different.
It is therefore critical that you consult your obstetrician before
embarking on an exercise program. Exercise and pregnancy can coexist.
Studies have shown
that exercising, besides giving the benefits of maintaining fitness,
can also attenuate the symptoms of nausea, fatigue, and back pain. The
American College of Obstetrics and Gynecology is now emphasizing
the importance of exercise before, during and after pregnancy. Years
ago doctors restricted the type of exercise that was safe; today the
emphasis is on promoting exercise and pregnancy so long as certain
precautions are followed.
The exercise you do on the exercise ball can gently work the
muscles
that help support your back during pregnancy. Also advertised as
the "birthing ball", the exercise ball is helpful for easing labour and
delivery. Once the baby is born, you can get back into exercising
easily using the ball again.
Benefits
of Exercise
The rationale of exercise and
pregnancy includes relief of
low back pain, preparation for labour and delivery by
increasing
strength, endurance, and tolerance for the physical and mental stress.
Posture may be improved and postpartum recovery may be easier
and
faster.
 CAUTION:
Prenatal and
postnatal
women must get clearance from
their physicians before participating in an exercise program.
They must be screened for conditions that would
limit
their
medical, cardiovascular, musculoskeletal, or pregnancy related
complications. |
Guidelines for Exercise During
Pregnancy
The
American College of Obstetricians and
Gynecologists has the
following recommendations regarding exercise and pregnancy -
discontinuing exercise under the following circumstances:
- Risk factors
for preterm labour
- Vaginal bleeding
- Premature
rupture of membranes
- incompetent cervix
- intrauterine growth retardation
- multiple
gestation
Pregnant women are best to
consult their physician for advice regarding
exercise and pregnancy if they have conditions such as
- hypertension
- gestational
diabetes
- heart or respiratory condition
- history of premature labor
- placenta
previa
- preclampsia
_________________________________________________________________________________________
Most experts suggest that you
adhere to the guidelines suggested by the acronym FITT:
Frequency:
3 to 5 times per week
Intensity:
Moderate intensity
Time:
Maximum
of 40 minutes per session
Type:
Low
impact aerobic type exercise (swimming, walking, bicycling)
Months 1 to
3
If
you are were
active several months prior to the pregnancy you should
remain active but adhere to the FITT guidelines. If you were inactive
prior to your pregnancy, hold off exercising for the first three
months.
Your
usual routine is safe. Listen to your body. Nausea and
fatigue may limit your endurance so shorten your routine, reduce its
frequency, or change the time of day you exercise. During this period
it
is still safe to lie on your back. Take this opportunity to strengthen
your abdominal musculature as this will weaken very quickly once your
abdomen starts to expand. Women with strong abdominal muscles will
return to their pre-pregnant figures faster after giving birth, and
will
suffer less back pain.
Months 4 to
9
Previously
active women are able to increase their exercise intensity during the
second trimester by 10-15% but within the target zone established by
your health care professional. Previously inactive women may begin low
impact aerobic activity such as walking, swimming, or cycling.
Changes occur in your
body during pregnancy that can affect your ability to exercise while
pregnant:
Ligaments: The hormones
produced during pregnancy, especially the last trimester, cause the
ligaments that support your joints to become more elastic. This causes
your joints to lose stability and are therefore at risk for injury. You
should avoid sudden bouncing, jerking, or high impact
activities. Be careful when exercising if you notice loose or unstable
joints.
Balance:
As you gain weight,
your centre of gravity changes and therefore your posture changes,
putting
strain on new muscles and ligaments. This can result in altered balance
and increased risk of falls. Most exercise ball exercises require some
degree of balance so be aware of this and adapt your movements
accordingly.
Cardiac
Output:
Your heart
needs to work harder at rest due to the increase in weight, and
therefore works even harder when your muscles are demanding increased
oxygen. Increases of up to 50% in cardiac output, 15 beats per minute
in resting heart rate, and 45% increase in blood volume can occur by
the third trimester. The body may divert blood flow from some parts of
your body in
order to meet the needs of the muscles. It is therefore important not
to overdo it. Standing for long periods can reduce placental blood flow
so keep changing positions.
Metabolic Rate
Both pregnancy and exercise increase your metabolic rate and therefore
core body temperature. It is also know that core temperatures in excess
of 102.60F are potentially teratogenic in the
first three months. While adaptive changes that occur to the woman's
body during pregnancy help dissipate this extra heat, it is still
prudent to maintain adequate hydration and avoid exercising in hot or
humid environments. To avoid compromising fetal growth, caloric intake
should be adequate to offset the combined needs of pregnancy and
exercise (typically an extra 300 calories a day).
Pregnancy and exercise both increase the bodies need for
oxygen. Oxygen
requirements during pregnancy are greater therefore limiting
your ability to perform high intensity activities. You need to heed
signs of fatigue and stop workouts short of exhaustion to reduce the
potential risk of hypoglycemia. Sessions for recreational athletes are
best limited to 45 minutes.
Increasing
abdominal size:
The weight of the growing fetus will compress the inferior vena cava
and hence affect blood return to the heart possibly causing your blood
pressure to drop when lying in the supine position. This can disrupt
the oxygen supply to the fetus.It is obvious then to avoid the exercise
ball exercises that require you to be in the supine position. Prone
abdominal hollowing, and pelvic tilts in standing can be used
to
activate the abdominal muscles.
The increase in
abdominal size puts extra strain on
the supporting back muscles so
avoid
those more
advanced exercises such as
- push
ups
- double leg raises
- full
sit ups
- jumping, hopping or skipping
- quick
dance moves
Supportive bras and back braces are now available to assist you with
these changes as you exercise.
Exercise and pregnancy can go hand in hand.
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|
The Physiology of Exercise and
PregnancyBecause
multiple organ systems are involved in creating the optimal environment
for the fetus, the physiology of gestation is complex. The impact of
exercise on pregnancy and its physiologic variables has been studied,
but there is no
agreement about some aspects of cardiopulmonary and metabolic
response. Studies involving human subjects have been
inconsistent,
partly because of differences in study design, exercise regimens, and
the fitness level of the participants. Prospective, adequately
controlled studies of humans are few, so animal models have been used
to elucidate the interaction of pregnancy and exercise.
The
energy cost of pregnancy is higher than that of the non pregnant state
by an average of 300 k.calories per day, exercise also increases
caloric
expenditure. So pregnant women who exercise need to consume enough
calories to meet these increased needs. Physically active pregnant
women should eat enough to satisfy their appetite, preferable a diet
rich in complex carbohydrates. Weight should be monitored to be sure
that gains are steady and adequate.
Hyperthermia
during
pregnancy is a potential teratogenic risk to the fetus. Some experts
are concerned that pregnant women who exercise may increase their body
temperatures to dangerous levels. However, studies show that exercise
does not cause the same level of increase in body temperature in
pregnant women as it does in non-pregnant women. This may be because
the work intensity achieved by pregnant women is not high enough to
cause such a rise. Pregnant women also may be better able to cool
themselves with changes in regional blood flow.
Women
who choose
to exercise during pregnancy must drink adequate fluids. They should
drink up to a pint of liquid before exercising, and a cup of liquid
every 20 minutes during exercise. Even if they are not thirsty after
exercise, they should drink enough to replenish lost fluids( 1-2 litres
of fluids per hour may be lost through sweating)
Pregnant
women
also should be cautioned against exercising when the weather is hot
and/or humid, or when they have a fever. In general, the higher the air
temperature, the lower the humidity, the concern with exercise and
pregnancy must be to avoid heat injury. For
example, if the air temperature is above 80 degrees Fahrenheit,
humidity
should be no higher than 50%. Also, it's safer to exercise before 8 am
and after 6 pm.
The weight of the growing fetus
increases lumbar
lordosis, moving the centre of gravity to the pelvis and causing a
compensatory increase in cervical spine flexion. Balance may become
precarious as movements are modified to accommodate these changes.
Pregnant
women should be told that exercises involving sudden changes in body
position carry a greater risk of falls. Sports with the potential for
abdominal trauma, such as surfing, horseback riding, or trampoline
exercise, should be avoided.
Ligaments relax as
connective tissue
softens in response to hormone changes early in pregnancy. This
increased joint mobility may facilitate delivery of the baby, but it
also may make women more vulnerable to sports induced injury during
exercise and pregnancy. Softening
of connective tissue and increased lordosis is also related
to the
back pain that often occurs in pregnancy. | Adequate
warm up is important to avoid sprains. Pregnant women who do resistance
exercise should use light weights so that joints are not excessively
loaded.
Water retention in the third trimester may
reduce mobility
at the wrists and ankles and lead to carpal tunnel syndrome, causing
sensory changes and muscle weakness. Activities involving strength and
agility of the hands such as tennis and skiing may make pregnant women
more injury prone during exercise and pregnancy.
Cardiac
output increases by 30-50% during
pregnancy, peaking in the second trimester. It is variable in the third
trimester but decreases when the woman is in the seated or supine
position because of decreased venous return. Both components of cardiac
output -heart rate and stroke volume - increase. The stroke volume is
greatly affected by an increase in heart size, with left ventricular
volume enlarging considerably by term. The responses to exercise of
both stroke volume and cardiac output are significantly increased
during pregnancy. An increase in blood volume parallels the increase in
cardiac output to some degree. The volume of plasma component of blood
increases up to 50%, but red cell volume increases only up to 20%,
resulting in the relative anemia of pregnancy, with hematocrit dropping
from a normal of 40% to about 35%. This is similar to the pseudo anemia
seen in endurance athletes and may be more significant in pregnant
endurance athletes. Oxygen distribution to tissues is not affected by
this drop in hematocrit as seen by the decreased arteriovenous oxygen
difference.
The resting heart rate rises in the
first weeks of
pregnancy by about 7 beats per minute and plateaus after 32 weeks at a
rate approximately 16 beats per minute faster than the prepregnancy
rate. Studies of fetal growth and development show that increases or
decreases in fetal heart rate during exercise are transient and produce
no deleterious effects.
The mean arterial blood
pressure of a
pregnant woman drops reaching its lowest value at mid pregnancy and
returning to near prepregnancy levels at term. Systolic blood pressure
changes very little, so women have an increased pulse pressure and
throbbing pulse. Peripheral resistance also decreases, allowing an
increased cardiac output with a drop in blood pressure.
Cardiac
output and blood pressure may vary with changes in body position. When
a pregnant woman is in the spine position, the uterus rests on the
vertebral column and can compress the inferior vena cava and abdominal
aorta, causing a drop in cardiac output and resultant hypotension.
The
decreased venous return raises the concern of whether certain positions
assumed during exercise compromise blood flow to the fetus. Exercises
performed when a woman in in the supine position are not recommended
after the first trimester. Motionless standing can cause an even
greater drop in cardiac output and should be avoided when possible.
Blood to skeletal muscles and the fetus is in parallel circulation, and
a potential problem is that blood may be shunted toward exercising
muscles and away from the fetus. Animal studies show that although
uterine blood flow transiently decreases during exercise, uterine
oxygen extraction increases markedly during pregnancy, and fetal and
placental oxygen levels are maintained. Hemoconcentration during
exercise occurs to a greater degree in pregnancy than in the
nonpregnant state, enhancing oxygen delivery. | Basal
oxygen consumption increases during pregnancy by about 40 ml/min, with
the fetus, placenta, heart, and kidneys consuming the most oxygen.
Pregnant women increase ventilation by breathing more deeply rather
than more frequently. Although the diaphragm rises with the increasing
size of the uterus, the total lung capacity and vital capacity change
very little. Tidal volume increases up to 40% as the woman
breathes
more deeply, and residual volume and expiratory reserve volume become
smaller to compensate. This results in a smaller oxygen reserve in the
lungs at the end of a quiet expiration, and less ability to withstand
apnea. For this reason, scuba diving and sprinting are not recommended
during pregnancy.
Pregnant women respond
differently to
physical exercise than do nonpregnant women. They also show greater
variability in response to the physiologic challenge of exercise. The
increase in body weight and reduced efficiency of oxygen utilization
requires a greater oxygen cost for any given weight bearing exercise.
The reasons for this greater oxygen cost are not entirely understood.
Some studies indicate that women who exercise during pregnancy may have
a training effect, increasing their aerobic capacity.
Many
women
experience a decline in exercise performance during pregnancy and are
unable to maintain high levels of aerobic exercise. This decrease in
exercise tolerance is due in part to a lower cardiopulmonary reserve,
but factors such as fatigue, nausea and vomiting and changes in body
configuration may also contribute. There is some indication that non
weight-bearing exercises such as swimming and cycling are better
tolerated by pregnant women.
Exercise during
pregnancy maintains
muscle tone, strength, and endurance and it may protect against back
pain and other discomforts. Subjective benefits such as improved mood,
energy level and self-image have been reported. Women who exercise
regularly at a moderate intensity can maintain cardiorespiratory
fitness during pregnancy and reduce the risk of postpartum obesity.
Most evidence suggests that moderate exercise during normal pregnancy
has no adverse or beneficial effects on maternal weight gain, length of
gestation, length of labour, infant birth weight or APGAR scores. One
must be wary when exercising while pregnant because there are flaws in
the studies available about the effects of exercise on pregnancy and a
lack of studies using human subjects.
All pregnant
women need a medical
and obstetric examination before they begin an exercise program.
Contraindications to exercise should be ruled out, and women with
conditions such as chronic hypertension or active thyroid, cardiac,
vascular or pulmonary disease need a careful evaluation to determine if
they are candidates for regular exercise.
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The Exercise Ball is Otherwise
Known as the Birthing Ball
For information on the birthing ball click
here!
For the American
College of Obstetricians and Gynecologists'
Educational Brochure click on the following link:
http://www.acog.org/publications/patient_education/bp119.cfm
For Guidelines of the American
College of Obstetricians and Gynecologists for exercise and
pregnancy and the postpartum period click on the following link:
http://bjsm.bmj.com/cgi/content/full/37/1/6
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