Wednesday, March 4, 2009

Don't Run to Get Fit, Get Fit to Run: Running Mechanics

The bipedal, human body is designed to move efficiently with the running motion. The natural, rhythmic movement is a coordinated effort of the whole body to propel itself with ground reaction forces, while conserving and creating inertia to reposition itself properly for each step. No other motion allows one to travel significant distances or at as great velocities as running does.

While most people can run if they had to, the majority have poor, inefficient running mechanics that result in inferior performance and considerable muscular-skeletal strain. While adequate cardio-respiratory function is essential for running, the muscular function will determine how the body handles the stresses placed upon it. Like a hammer striking a nail, control of the reaction force transfer is essential. Suboptimal joint stability and the inability to dissipate, or redirect forces because of weak and tight muscles will lead to tissue failure of the lower body.

Let’s review the basics of running. Each leg alternates between a ‘stance’ phase and a ‘swing’ phase. The stance phase is when one foot hits the ground, bears weight, and pushes off. The swing phase immediately follows the ‘stance’ phase. It includes the time when the leg is off the ground and moving from behind the body to in front of the body.

The arms and torso play a significant role in running, especially as speed increases. The arms act as ‘drivers’ and develop inertia, which is transferred through the torso to the hips. This energy assists the hips to move the legs with more power.

Common fitness deficits that lead to poor running mechanics:

  1. Lack of Hip Mobility- The legs need to move through a large range of motion, but can be restricted by tight or weak hip muscles. Notice the range of motion the elite runners moved their legs through while still maintaining an upright posture.
  2. Weak Single-Leg Stance Stabilizer Muscles- The muscles of the lateral (outside) hip control the position of the entire leg and foot. Weakness and/or fatigue can lead collapsing (thigh rotating inward upon contact with the ground) of the stance leg. This not only puts more stress on the knees, but the foot, too. A symptom of this is 'fallen arches'. Females, because their hips are wider than their knees, are more likely to be affected by this issue.
  3. Weak Leg Muscles- Passive tissues like cartilage, ligaments, and tendons absorb more force when active tissue, muscles, aren’t strong enough. Strength training will not only strengthen the muscles, but also the passive tissues.
  4. Poor Muscle Elasticity- Muscles and tendons of the lower body absorb and release energy back to the ground (like springs) when you run and jump. Your 'running efficiency' is an index of how fast you can run while burning a certain level of energy (exercise physiologists call this VO2, or oxygen uptake). The greater the elasticity of your muscles and tendons, the less force the actual muscle cells have to develop and the greater your 'running efficiency' will be. Disuse and aging contribute to decreased muscle elasticity.
  5. High Body Weight- Obviously, the more you weigh, the greater the ground-reaction forces on all of your tissues.
  6. Weak torso muscles- The torso muscles transfer forces from the upper extremities to the lower extremities; this is even more important at higher speeds and sprinting.

1 comment:

Janet said...

Dan -- Thanks for the excellent info! I'll be sure to share it with my daughter (middle school cross country/track runner) and husband (recreational runner). The technical details you provided make the info very concrete.

Are you going to continue this topic and tell us how to correct our inefficient running mechanics?