In the case of both strength and flexibility the important factor is symmetry. Unequal development of either strength or flexibility can pull the body out of alignment and so cause postural faults – both with the static posture and the dynamic posture – Muscle imbalance such as this needs to be corrected under the direction of a physio.
The lower back should have a slight hollow called the lumbar lordosis. This is affected by the tilt ot the pelvis. The pelvis is balanced like a see-saw on the hip joints and is controlled by the abdominal, spinal and hip muscles as well as by the ligaments in these areas.
The abdos and hams will tilt the pelvis backwards and flatten the lower spine. The hip flexors and spinal extensors tilt it forward and increase the tilt. Most of us have weak abdos and tight hip flexors causing and increasing tilt.
The traditional ‘sit-up’ is the most well known abdo exercise but this strengthens the upper abdominals and also the hip flexors (as most of us cheat!)
In order to strengthen the deep abdominals or the corset muscles as they are called, we have to be more precise and exercises need to be taught under supervision.
We are not concerned with how strongly we can flex our trunk forward as in a sit-up but more the ability of the muscles to support our backs over a long period of time – like a corset – the way they are designed to.
This strength provides a ‘core stability’ which is a very fashionable phrase in physiotherapy. It is the basis of Alexander technique, Pilates etc.
This core stability provides a solid base from which to work the limbs hard. (eg crane on soft sand).
This muscle balance is very important for swimmers that require a good dynamic posture through the water. In order to achieve this, good spinal stability needs to be looked at. Weak abdominals or tight hip flexor muscles often allow the pelvis to drop and tilt too far – increasing the lumbar curve – this can cause back pain in swimmers particularly doing breast stroke.
You can see that this is a great advantage to a swimmer. Better posture through the water, good core stability and stronger limbs = a faster swimmer with less injuries, and less wasted energy.