Running Biomechanics and Injuries

Definitions and Ideas to Consider

Overuse Injury Concepts

The majority of running injuries are classified as “overuse” injuries. These types of injuries are different than sudden traumatic injuries such as a sprained ankle or torn ligaments in a knee. As the name implies, overuse injuries are the result of repetitive micro-trauma and abnormal stress to muscle, tendon, or other soft-tissue. These stresses can also lead to micro-trauma to the bones, resulting in bony stress reactions or stress fractures. The problem is that too much of the focus on treating overuse injuries is dedicated to treating the pain, not the underlying imbalance which is truly the root cause of the problem. Diagnoses such as IT band syndrome, plantar fasciitis, anterior knee pain, shin splints, and hamstring strains all typically have underlying imbalances that are causing the stress to end up where the pain is.

1. The “Bent Car Frame” Analogy: Runners wonder why they are able to run and train consistently at certain distances, yet every time they try to ramp up their mileage they get hurt. Imagine a car with a bent frame. Driving short distances at slower speeds, this car would show no signs of a frame imbalance. However, if driven 90 miles a day at high speeds (like more intense running) there would most certainly be stress to the tires and suspension resulting in a problem like a flat tire. Many runners have imbalances like this that do not get exposed and lead to pain until they increase training.
2. The “No Cell Phone Coverage” Analogy: Every joint has position sensitive receptors that communicate with the surrounding muscles (called joint proprioception). When a hip, knee, or other joint gets forced into a position where there is poor proprioception, the surrounding muscles cannot recognize the position and thus have poor firing capabilities…..i.e. they have no cell phone coverage in that position. The body must compensate in these positions to try and stabilize its center of mass to meet the primary objective of not falling down and to continue running forward.

Kinetic Chains

The concept that muscles and joints do not act as individual units, but rather as connected “chains” that must be coordinated together for human motion.

1. Remember the song…..”The foot bone connected to the, leg bone, the leg bone connected to the, knee bone, the knee bone connected to the, thigh bone………”
2. Deficits at one end of a kinetic chain can create problems elsewhere.

• Example: Poor hip strength can result in foot/heel pain.
• Example: Pelvic mal-alignment can be the root cause of knee pain.
• Example: Abnormal foot motion can cause knee, hip and back pain.

Orthotics, Insoles, or Change the Shoe?

Orthotics, special insoles and stability shoes are strategies to control motion at the feet, and to influence mechanics up the kinetic chain to the knees, hips and pelvis. In some cases this control is absolutely necessary, and in others it is nothing more than a band-aid approach that passes the stress at the feet on to another body part. Physical therapists who have extensive training in biomechanics and running can assist you in determining the best approach when considering these things.

Muscle Inhibition vs. Activation

Muscles are made of many individual “motor units”. When the nervous system sends a neural signal to contract and the motor unit efficiently engages, the muscle is “activated”. Depending on the task at hand (lifting a coffee cup vs. lifting a 20lb. weight), the nervous system activates fewer or more motor units to accomplish the task.

Muscle “inhibition” is a state where there is inefficient recruitment of the motor units of the muscle. This is not a nerve problem but nerve to muscle communication error. Common causes for muscle inhibition are:

• Pain, inflammation or swelling in the area
• Repetitive compensatory muscle recruitment patterns
• Limited joint range of motion putting the muscle in a mechanically disadvantaged length
• Mal-alignment of the joint which that muscle crosses
• Fatigue
• Other systemic stresses

Pronation vs. Supination

Most think of pronation and supination only as it relates to foot alignment; however it is actually a sequence of movements (think kinetic chain) that involve the entire body.

1. Pronation

• Collapsing of body (flexion)
• Works with gravity
• Shock absorption
• Requires eccentric strength/stability (to stop it)
• Creates storage of elastic energy
• Pronation injuries: when the “stop” to pronation comes from the wrong area
• Extension of the body
• Works against gravity
• Propulsion component
• Produces concentric force via elastic energy recoil

1. Supination

How to Evaluate for Running Imbalances and Injuries: What are we looking for?

1. Posture/alignment testing: Pelvic asymmetry; leg length difference; poor posture?
2. Joint range of motion testing: Any asymmetry in flexibility or range of motion?
3. Muscle testing: What muscles are strong vs. weak/inhibited?
4. Functional testing: Is there a side that is less stabile or shows obvious compensation?
5. Gait analysis: How do you move? Stride length, swing phase, and push off.
6. Shoes: Wear pattern; appropriate for your foot-type?

Written By:  Brad Ott, MSPT, Cert MDT

Owner, Rebound Sports & Physical Therapy