Physiological Changes During Pregnancy
When you become pregnant your body goes through a series of changes, most of which will have an effect on how you exercise. Here are some of the key changes:
- Reduced joint stability - during pregnancy a hormone called relaxin is produced. Its job is to relax the ligaments of the joints in the pelvis to facilitate childbirth. Unfortunately it doesn't just affect this area, it affects all joints making them more flexible and so less stable. So when exercising, it best to do so on flat, even surfaces and to avoid activities that require lots of balance or sudden changes of direction, and when stretching, keep them light for a maximum of 10 seconds.
- Stretched ab muscles - relaxin also relaxes fibrous muscle tissue. This enables the abdominal muscles to stretch to accommodate the growing baby. This puts the muscles under a lot of stress, so from the 2nd trimester onwards, when you start to show, you should avoid doing core exercises where you flex or rotate - e.g. sit-ups, ab crunches, side bends and oblique twists. Instead do static core exercises such as abdominal hollowing or reverse bridging.
- Stretched pelvic floor muscles - relaxin also affects the pelvic floor muscles enabling them to stretch and allow the baby to pass during childbirth. To ensure that they do not become overstretched and weak under the weight of the baby during pregnancy and to help towards a quicker recovery following the trauma of childbirth, it is best to avoid high impact activities and to do pelvic floor exercises (slow and fast contractions).
- Reduced venous return - a hormone called progesterone relaxes the walls in the veins, which can affect the return of blood back up the body. This can cause dizziness if you stand still for too long or get up too quickly.
Venous return can also be reduced by the weight of the growing baby when lying down, so from the second trimester onwards it is best to avoid exercises that involve lying down on your back.