Pregnancy and Fitness
Notes taken from Aerobic and Fitness Association of America ‘Fitness Theory and Practice’ The comprehensive Resource for Fitness
The Fit Pregnancy
Pregnancy is finally starting to be recognized as a modified state of health rather than a state of illness. Ongoing prenatal care and close
communication with their caregivers on the type, frequency and intensity of exercise is a must for the pregnant student.
Students often place unrealistic expectation on the effect that exercise may have on the outcome of their pregnancies, labors and
deliveries. It has been shown that exercise during pregnancy can enhance energy level, self-esteem, and mood, while reducing some of the
physical discomforts of pregnancy.
Increased levels of hormones relaxin, elastin, estrogen and progesterone soften the connective tissue surrounding the joints. This is to
allow the pelvic joints to expand to accommodate the baby passing through the pelvic inlet during birth, but unfortunately, all the
weight bearing joints are affected too – especially the knees, ankles and hips.
Cardiovascular and Hemodynamic changes
The blood volume may increase as much as 30-50%. Plasma volume increases more than the red blood cells, resulting in a tendency
toward lower hematocrit levels. However, during exercise, plasma volume shifts resulting in hemoconcentration and improved oxygen
carrying capacity in the blood. Exceeding 144 beats per minute is not recommended due to lack of research beyond this range. The
weights of the uterus and the fetus may also compress the inferior vena cava when the mother is in a supine position. This compression
decreases the venous return from the legs to the heart and head. Symptoms usually include dizziness, lightheadedness, nausea and
Fetal oxygen demands may increase a pregnant woman’s resting oxygen consumption as much as 16 – 32%. Pressure on the diaphragm
from the enlarging uterus reduces the height of the pleural cavities as much as 4 centimeters, causing a feeling of dyspnea or difficulty
taking a deep breath. The decreased functional reserve capacity and residual volume is compensated for by an increase in tidal volume
and lateral expansion of the lungs.
The needs of the growing fetus increase the basal metabolic rate of the mother. Body core temperature also increases. Studies done on
pregnant exercisers have shown that exercise in moderation was well tolerated with no resultant hyperthermia. Dehydration during
exercise could have a very harmful effect and is a known cause of premature labor later in pregnancy.
Due to the demands for glucose from the fetus, blood glucose levels particularly fasting blood glucose levels tend to be lower. Pregnant
women also tent to use carbohydrates at a greater rate during exercise.
As the uterus increases in size and weight, it pulls the pelvis into a forward tilt, causing stress on the lumbar sacral ligament and lower
back muscles. The abdominal muscles tend to stretch and weaken while the lower back muscles tend to shorten resulting in a ‘sway back’
or lordotic posture. Due to the natural tendency to assume a lordotic posture, pregnant students need to be constantly reminded to
maintain a neutral pelvic alignment.
The weight of the enlarging breasts tends to pull the shoulders forward resulting in a slouched posture of the upper back. The pectoralis
muscles shorten while the upper back muscles stretch and weaken. Upper body work should focus on strengthening the upper back
muscles in order to avoid a permanent postural imbalance.
Round Ligament Syndrome
The uterus is suspended in the abdominal cavity by ligaments. Two ligaments run diagonally down the pelvis from the hip bones. After a
fetal growth spurt, women may notice a dull, pulling sensation in these ligaments for 2-3 days. Sudden turns or sharp movements may
illicit a spasm in these round ligaments.
Pelvic Floor Muscles
The pelvic floor or pubococcygeal muscles are probably one of the most stressed muscle groups during pregnancy and childbirth. They
are located between the legs and are attached to the pubic bone in front and the coccyx in back. This muscle group is responsible for
supporting the weight of the pelvic organs (uterus, bladder and bowel) and encircles the urinary opening, the outer vagina and the anus.
During pregnancy, the weight of the uterus and growing baby places tremendous stress on these muscles. In order to strengthen these
muscles, students are encouraged to build up to 5 – 10 sessions of 10 repetitions of kegel exercises (rapidly tighten & relax, elevator
exercise with ‘bulging’ at bottom floor).
The linea alba is the fibrous seam which connects the two rectus muscle sheaths in the center of the abdomen. It is important for the
student to exhale on the effort phase to avoid the Valsalva maneuver. The muscle used most in childbirth is the transverse abdominis.
Particular attention should be paid to strengthening this muscle group. Pregnant women should be reminded to pull in with their
transverse muscles during all exercises and to use and strengthen this muscle group as much as possible. The hormones secreted during
pregnancy also relax the linea alba. Women may notice a thicker waistline as a result of decreased tone very early in pregnancy. As the
uterus expands, the forces may cause the linea alba to separate (diastisis recti), like a zipper under too much stress. This separation,
considered very normal during pregnancy, is painless and often goes unnoticed.
To check for Diastasis Recti
1. Student lie on her back, knees bent
2. Gently but firmly place 1-2 fingers perpendicular to the linea alba, 1-2 inches below the naval.
3. As the student raises her shoulders, check how many fingers you can insert in the gap.
Physiological and Anatomical Changes during Pregnancy that affect exercise:
Research on humans who exercise during pregnancy is scant.
Hormonal Changes: The body begins to secrete increased levels of progesterone, estrogen, relaxin and elastin which cause relaxation of
the ligaments so the pelvis can loosen and allow the baby to pass through it.
Cardiovascular Changes: The blood volume during pregnancy increases 30 – 50%. Heart rate is elevated at rest, and cardiac output
increases 30-50%. Perceived exertion may be the best indicator of a woman’s tolerance for her workload. Exercising longer than 45
minutes carries a higher risk of hypoglycemia and increased body temperature. Recovery heart rate should be below 50% Maximum heart
Supine hypotensive syndrome is when the enlarged uterus compresses the vena cava in a back-lying position. Symptoms include dizziness,
nausea, rapid heart beat or becoming flushed. Prolonged motionless standing decreases output even more than back-lying.
Respiratory Changes: The diaphragm is displaced upward, but the rib cage expands laterally to compensate (possibly by 2 inches).
Metabolic Changes: The basal metabolic rate increases by 15 – 25%. Pregnant women should avoid saunas and very hot baths.
Dehydration increases core temperature to dangerous levels.
Endocrine Changes: Carbohydrates are utilized at a greater rate during exercise, so women are more prone to hypoglycemia. A pre-
exercise snack is very important.
Lordosis: The enlarged uterus pulls the center of gravity forward, causing a curve of the spine. Strong abdominal muscles and stretching
of the hamstrings, lower back and hip flexor muscles help.
Kyphosis: Kyphosis is a slumped posture with the shoulders and chin jutting forward. Chest strengthening and stretching is important to
support the breasts, and strengthening the trapezius, rhomboids, latissimus dorsi and pectoralis will support proper alignment.
Carpal Tunnel Syndrome: Because of fluid retention in the wrists, the median nerve is compressed, causing numbness in the thumb,
index and middle fingers. Good hydration and watching salt intake and splinting the wrist at night is suggested.
Sciatic Pain: When the fetus puts pressure on the blood vessels and tissues from the buttocks down the back of both legs, causing a sharp,
piercing sensation. Stretching and applying heat may help.
Round Ligament Pain: The round ligaments hold the uterus in place begin to stretch, causing a pain the groin area. Heat, ice and pulling
the knees to the chest may relieve the pain.
Diastasis Recti: The rectus abdominal muscles pull apart as the hormones relax the lina alba, soft tissue holding the two long muscles
together. A separation of more than 2 fingers means that abdominal curl-ups should not be performed.
Pelvic Floor Muscles: The muscles attached to the pubic bone and coccyx hold most of the weight of the uterus. Adequate control over
these muscles is essential to allow smooth progress of the baby’s head through the birth canal. Kegel exercises are excellent for
strengthening these muscles and should be continued throughout life.
Fetal Response to Exercise: Fetal heart rate increases during exercise. The placenta of women who exercise early and mid pregnancy grow
faster and function better by improved vasculature.
SAFETY IN PRENATAL EXERCISE
Pregnant woman should stop exercising if they experience:
- pain of any kind in chest, head, back, pubic or hip
- frequent uterine contractions
- vaginal bleeding
- leaking of amniotic fluid
- dizziness or faintness
- shortness of breath
- decreased fetal activity
NUTRITIONAL NEEDS FOR ACTIVE PREGNANT WOMEN
Good nutrition is critical for proper growth and development of the fetus, and to protect the mother from the damaging loss of iron and calcium stores. It takes about 300 extra calories per day to grow a baby. Protein is needed for fetal growth, about 60 grams per day. Iron is used for blood production.
The following nutrients should be increased and are necessary and should be taken in smaller more frequent meals: sodium, water, potassium, calcium, phosphorous, iodine, magnesium, folic acid (used for protein metabolism), vitamin A, Vitamin D, Vitamin E, Vitamin C, Riboflavin, Thiamine, Vitamin B6, Vitamin B12.