Friday, March 22, 2013

Notes on Gait Function with Thomas Michaud

These are some of the highlights or things I found of importance in a recent webinar I took given by Thomas Michaud.

Walking, your center of mass (COM) is highest at midstance.  Running the COM is lowest at mid stance.

Inefficiency of the Gastroc is the point where speed goes from walking to running.

Some studies done with forefoot running as a means to prevent injury were flawed as they were done with college runners that had already become midfoot strikers.

Runners that are not elite that transfer to a forefoot or minimalist type shoe show arch inner calf problems if they have a flatter arch, higher arched individuals show with more metatarsal strain/stress fracture.

Most runners are more efficient with heel strike when energy expenditure is looked at.  Around the 6 minute clip is when forefoot running becomes more efficient.

Shape of the heel is perfectly suited to absorb impact.  100lb female has a larger heel bone then a 350lb Gorilla.

Heel expands and contracts like a rubber ball.  Thin outer layer of bone and and extensive blood supply to help repair.

The heel is protected by a well designed 3/4 inch fat pad.  The fat pad is spiral chamber of sealed fat.  Fat pad is several chambers.  Outer layer is a protective cup.  The inner layer is a major shock absorber.      It quickly deforms and reforms.  Retains all its shock absorption even in cold environments.   It is made of polyunsaturated fat.

Barefoot running shows 60% deformation of heel pad.  Shoes it is 35%.  Walking is 40%.  Thinning of the heel pad is a major predictor of foot pain.

With a heel strike the Tibialis Anterior is used to handle the absorption of impact which it is well designed to do.  Midfoot strike the Tibialis Posterior is responsible for slowly lowering the heel.  Forefoot strike the Gastroc is used.  It is not well designed for this as it crosses 2 joints.  2 joint muscles are easier hurt.

Flexor Digitorum muscles are important for dampening the oscillation from bony vibrations.

Lateral Gastroc and Biceps Femoris were important for pre muscle contraction right before impact.  This is why running surface matters very little.

While glute med/min are important for hip stability, the faster you run, the more important the Glute Max becomes.

One myth is that disc act as shock absorbers.  McGill has proved that the endplates of the vertebral bodies are what absorb impact.

IT Band is an energy storer.  Hips are force producers, lower legs act like rubber bands storing and returning energy.  Prosthetic makers have started to take advantage of this key understanding.

Seems counterintuitive, but the calf muscles don't go through big lengthening, more of an isometric with the tendons going through large changes in length.  As we age, tendons get more brittle, hence we have a harder time moving fast.

Flexor Digitorum Brevis is an important muscle for maintaining arch height.  Weakness may be a important cause of plantar fasciitis.

Slow running possibly less stress on the joints then walking.

Flexor Hallucis Longus pulls the fibula head down.  This deepens the ankle mortise and helps to prevent ankle sprains.  So if dealing with an ankle sprain, mobilize fibula and strengthen FHL.

Achilles is unique as it rotates 90 degrees before attachment.  Gastroc/Soleus (GS) primary role is not one of concentric (shortening) but more isometric impulse as and anchor for the Achilles tendon and allow the Achilles to go through large ROM.

Plantaris is located between the GS.  To thin to be used for force production, now known to be loaded with mechanoreceptors.  It provides detailed information to CNS to allow the GS complex to create precise isometric impulse for proper Achilles function.

When Achilles is storing and returning energy efficiently, it reduces the load on the hip flexors.

Looking forward to reading through Thomas Michaud's latest book.  "Human Locomotion."


Danny Adams said...

Brilliant Stuff once again Jason, thank you, just ordered the book :D

Jason Ross said...

Thanks Danny!