The physiological changes which occur during pregnancy are largely under the control of the endocrine system. It is the role of the hormones to create the right conditions to maintain the pregnancy and nourish the growing foetus. One of the most influential hormones is Relaxin. The key purpose of Relaxin is to relax the musculoskeletal system by softening ligaments, loosen joints and stretching muscles and tendons. This allows a gentle but effective expansion of the pelvis creating the necessary space for the growing foetus and facilitating its passage during delivery. The effects of Relaxin are not just confined to the pelvic girdle, it increases ligamentous laxity throughout the body decreasing joint stability in the hips, spine, knees, ankles, feet, shoulder and so on.
According to the University Department of Obstetrics & Gynaecology, University of Adelaide, South Australia, a pregnant body is designed to increase the length of ligaments and soft tissue by a maximum of 10% although some women may be more susceptible to the effects of Relaxin. The body will only return the ligaments and soft tissue by 10% after the pregnancy state. This means that if the length of ligaments and soft tissues are increased by more than 10% there is a high risk of instability after pregnancy.
The two areas particularly affected by Relaxin are the sacroiliac joints and the pubis symphysis. The pubis symphysis is the bony junction connected by a tendinous seam. As the growing baby requires more space so the pelvis expands by a widening of the pubis symphysis, facilitated by Relaxin. The pubis symphysis may separate between 4-7 mm but it can widen by as much as 12 mm. The pubis symphysis also relies on the correct alignment of the sacroiliac joints for alignment. The sacroiliac joints function to resist the anterior tilt of the pelvis accentuated by the increased lumbar lordosis due to the growing weight of the baby. As Relaxin loosens the ligaments which support the joints instability and hyper-mobility may occur. This has far-reaching consequences for the stability of the spine and hip. As Pilates instructors it is essential that we consider these consequences. Exercises should be of low intensity, focusing on stability and strengthening work of the pelvic and lumbasacral area. Glut strengthening work is highly beneficial to encourage a more supportive role. In some case where pubis symphysis dysfunction is present, loaded ad/abductor work and prone hip extension should be avoided.
Diastasis Recti is the common, painless partial or complete separation of the rectus abdominus as a result of the widening of the linea alba to allow for the growth of the baby in the final stages of pregnancy . Relaxin allows the connective tissue, the abdominal fascia, to soften and reduces the cohesion of the collagen fibres. Any exercises which put direct pressure on the linea alba either from within by increasing abdominal pressure e.g. curl-ups or from without by gravitational resistance e.g. poorly executed swimming on all fours.
As stated earlier, Relaxin affects all areas of the body so flexibility work needs to be carefully monitored with an emphasis on correct technique, postural awareness and controlled, dynamic movement.
JPilates Pre & Post Natal Manual
Pre-and Post-Natal Fitness- The American College of Exercise
Image form isischiropractic.co.uk