A Short, Quicker Stride May Decrease Injury Risk

As stride length decreased, the runners bounced less, landed closer to their center of mass, and produced lower braking forces against the ground.

A shorter stride allowed the knee to do less work absorbing energy. A 10 percent higher-cadence stride allowed the hips also to do less work.

A shorter stride allowed the knee to bend less during stance, and decreased many hip motions. -peakperformance.runnersworld.com

Primary investigator for this study was Bryan Heidersheit, PT, Ph.D. of the University of Wisconsin's Department of Orthopedics & Rehabilitation and Biomedical Engineering. Effects of Step Rate Manipulation on Joint Mechanics during Running

According to Heidersheit, "If they increase their step rate quite subtly–by about 5 to 10 percent, which reduces their stride length by the same–then they can substantially reduce the forces to their knees. That happens primarily because they're lowering the vertical displacement of their center of gravity [their "bounce"], and hence coming down more gently. They also reduce the distance between their foot landing and their center of gravity. This reduces braking forces. The forces absorbed at the hips are also lower with shorter strides.

Does Running Help or Ruin Knees?

“The biggest predictor of injury is previous injury,” -NY Times article on running and knee problems

...by moving and loading your knee joint, as you do when walking or running, you “condition” your cartilage to the load. It grows accustomed to those particular movements. You can run for miles, decades, a lifetime, without harming it. But if this exquisite balance is disturbed, usually by an injury, the loading mechanisms shift, the moving parts of the knee are no longer in their accustomed alignment and a “degenerative pathway” seems to open.


MY COMMENT: This is good news if you've been running as long as I have (counting high school I ran my first race in 1968!) and have not suffered any significant knee problems.