Prior to recent medical studies it was advised that limited exercise periods of no more than 15 minutes at one time and a maternal heart rate of no more than 140 beats per minute be maintained.
Newer guidelines now affirm the safety of moderate exercise during pregnancy in the absence of medical complications.
There is an abundance of data now backing the fact that women’s bodies have a natural ability to maintain the health of the growing fetus while undergoing strenuous exercise.
Research also shows that active pregnant women are in better shape than those that are sedentary, gaining less weight from fat, having better muscle tone and are aerobically far better off.

Individual levels for exercise should be set and should be predetermined according to the standard of fitness at the time.

Exercising and body temperature was a legitimate medical concern and research was done in this regard. The results were amazing to say the least. one of the foremost researchers in the field Dr James Clapp 111,md, was able to show that heat stress on pregnant women during endurance exercise is reduced by 30% in early pregnancy and up to 70% in later pregnancy.
There are physiological changes that take place to the muscoskeletal, cardiovascular, respiratory and metabolic systems, enabling the body to cope with the demands placed on it in a more efficient manner.

In a study done at Baylor College of medicine and Texas children’s hospital, researchers found that aerobically fit women had a greater volume of blood per pump than that of inactive women. Their bodies also used greater volumes of oxygen from that blood. Earlier studies showed decreased blood flow to the baby during exercise and even using this information the research demonstrated that the increase in oxygen kept fetal oxygenation constant.

Common sense must prevail and attainable fitness goals should be set that will not compromise the health of the baby.
Cardiovascular fitness, improved posture, increased flexibility and enhanced muscular strength are all realistic goals that prepare the mother for childbirth while enhancing her self esteem.
The exercise intensity, frequency and duration should be adjusted not only in accordance to existing fitness levels, but relative to the stage reached in the pregnancy.

A certain degree of regression will be experienced in the first trimester where the pregnancy causes the need for more effort to be exerted in order to accomplish a given amount of work. As this is a critical stage to the development of the fetus, an easing up on the work rate would be well advised.

In the second trimester exercise intensity can be moderately increased and in the third trimester, once again a slight decrease of intensity is advised and shift from weight bearing exercise to non-weight bearing would also be more suitable but not essential.
Workouts should be kept at about 60% of maximum functional capacity although in seasoned athletes this could be a bit higher and would only be advised to do so under the guidance of her obstetrician or gynaecologist in conjunction with a specially trained instructor.

Pregnant women should under exercise rather than over exercise and there are specific modifications that would need to be made in order to accommodate the significant physiological changes taking place in the body.

Joint laxity caused by the production of relaxin, a pregnancy hormone, can result in becoming more prone to injury therefore thorough warm ups and stretching should be done, with the view to the specific muscles required for the exercise program.
Pregnant women have a starting body temperature of 1-2 degrees higher and although heat stress is reduced by between 30 and 70 % in pregnancy, one would be foolish not to adhere to all the necessary precautions relating to temperature regulation.
Most important is the fact that exercising in the supine position is contra-indicated after the 4th month of pregnancy. When a women lies on her back the weight of the fetus on the vena cava may obstruct the blood flowing back to the heart and head causing light- headedness.

Before exercising, be sure to be well informed of the warning signs to stop exercising during pregnancy; in order to avoid any unforeseen situations.
Exercise during the coolest part of the day and wear loose cotton clothing, drink sufficient amount of water, never exercise to exhaustion and stay away from caffeine based products. Do not do any form of exercise or sport that could cause trauma to the stomach through a knock or fall.

Finally, if you are going to exercise while pregnant, then do it regularly. sporadic exercise can be counter productive and the risk /benefit ratio becomes more a risk than if a disciplined sensible exercise regime is followed.

Michael Mcloughlin

Ref: Fitness for mothers to be.
By Deborah Kallen, m.s.

A clinical approach to exercise during pregnancy.
Clinics in sports medicine
By JF Clapp.

Exercise science
By Health and Fitness Professionals Association.