Core Stability For Runners
Muscle imbalances across the front and back of the hip
Muscle imbalances are common in distance runners because of the repetitive nature of the sport.
Errors in running form can arise due to existing poor postural habits or previous injury. They can worsen with fatigue and become reinforced with repetition.
Over time, poor running form means that the system learns to rely more on global mobilisers rather than stabilisers to perform the action.
For a more detailed description of mobilisers and stabilisers see my previous article, core stability intro.
A common muscle imbalance with runners arises when instead of using the correct pattern of hip flexion, they drive using TFL and rectus femoris (their superficial hip flexors) rather than the one joint stabiliser, illiacus.
See the picture below which details where the TFL (Tensor Fasciae Latae) and the Rectus Femoris muscles are located.
When these mobilisers across the front of the hip dominate, they create a restriction to hip extension. This means that the deep portion of Gluteus maximus (pictured in the diagram above) becomes elongated, resulting poor force generation in its inner range. For more about Gluteus Maximus see my blog on 'Glut Max Anatomy'
This means that rather than opening out at the hips during each stride, runners with tight flexors and poor inner range gluts will extend using their back extensors, hamstrings or push off more with their calves, which can lead to the potential of injury in those areas.