“Billions of neurons pass electrical messages down the spinal cord, which feeds the information to the body’s nervous system. Triggering the muscle cells to contract, the signal in turn becomes a gesture. The colossal task of coordination falls to the cerebellum. Containing more than 50 percent of the brain’s neurons, the cerebellum is the seat of synchronized motion. It provides us with the means to do everything from staying on a bicycle to swinging a golf club. Without it, muscles can’t function in time with one another.” – The Motor Cycle Diaries by Victoria Schlesinger, from THE BRAIN — An Owner’s Manual
(Biomechanics)
Photograph by Natalie Harding
A muscle is like a spoke on a bicycle wheel. When it is contracting optimally it is pulling (contracting) to maintain the balance at a joint, e.g., Centration.
When one spoke on the wheel is loose (weak), you no longer have the ideal balance *and* other muscles have to over-work (tighten up).
It is a guarantee: Your muscles will always tighten up to compensate for the weak muscle at a joint(s).
*Your* brain is very deliberate. It is doing anything within its power to protect your joint(s) from an injury.
Telling a different story.
(Leverage)
A muscle that is not pulling its weight at one joint will place more stress on a joint above *or* below, e.g., Runners Knee.
The most important muscle for a runner is conveniently located very close to the ground.
(Proprioception)
When the tibialis anterior *or* any other muscle is not receiving all of the neurological input it is considered to be weak.
The frequency of the neurological input is distorted, and the muscle(s) is not receiving enough input to contract when called upon.
*The* muscle can not generate a sufficient amount of internal force to reach the magnitude that is considered normal.
Tibialis anterior is a great example of how a single muscle with all of its complexity can (and will!) wreak havoc on the entire chain.
Here is that lazy word again…compensation.
*That* explains why your calves are always tight, and you feel the need to stretch them every single day without fail.
The truth is, they will continue to tighten up until you address the opposing muscle(s).
Here is a list of all of the things your tibialis anterior is responsible for:
- Accelerates the foot into a position(s) of inversion and dorsiflexion to prepare the foot and the chain for a successful single leg landing
- The combination of dorsiflexion and inversion of the foot drive the lower leg medially. The tibialis anterior accelerates transverse plane motion (rotation) of the lower leg in the open-chain.
- Decelerates the foot as it meets the ground. This is the case for both midfoot/forefoot contact and heel contact (not recommended since it takes so long to get to the big toe.)
- Controls the medial longitudinal arch to prevent over-pronation
- Pulls the lower leg over the foot, e.g., Dorsiflexion of the leg at the ankle joint
Your brain will not allow a joint to go into a position(s) where the body does not feel (sense!) stability.
When the tibialis anterior is not receiving optimal input the lower leg can not rotate in which is a component of pronation *or* a collapsing of the chain after the foot initially meets the ground, e.g., Flexion.
The short head (and long head) of the biceps femoris (hamstrings) will tighten up to compensate for the lack of neurological input to the tibialis anterior.
*Your* lateral hamstring will tighten up to prevent the lower leg from rotating in.
A tight lateral hamstring will have an impact on how your foot meets the ground which probably does not sound like much, but it is.
This is one of the biggest reasons why people who transition to a minimal shoe (or barefoot) end up with a stress fracture early on.
