When observing someone run, we can easily see their body’s posture, leg alignment and range of motion. What we cannot see are the forces acting on and within their body. In injured runners, these forces can be significantly higher. For example, the ground forces acting on the hip can reach up to 10 times a persons body weight!

High impact forces have been associated with running injuries. Measuring these forces can require highly technical and expensive equipment. Most clinicians do not have this equipment or skill set. Given the strong association between landing forces and injuries, it is important to have a system to detect larger ground reaction forces. Here are three key signs of high ground reaction forces:

1. Low Cadence:

This is the total number of steps taken in a minute. A 2016 study on 68 high school cross country athletes found those who took less than 164 steps per minute were more likely to experience shin splints or patellofemoral pain. Whereas, those runners with a cadence greater than 174 were much less likely to develop shin or knee pain.

Changing the number of steps a runners takes can yield great benefits. A 5% increase in cadence reduces force on the knee by 24%. However, it is not a perfect metric to identify excessive forces. A lower step rate when combined with the next two variables influences my decision making in advising a runner on their form.

2. Noise

Let’s try an experiment. Stand up and jump. When you land, do not let your knees bend. Listen to the noise and feel the shock you make when you land. Then repeat the same jump, but this time upon landing let you knees bend.

Which felt better?

Bending the knees!

Which was noisier?

Keeping the knees straight!

If I were to tell a runner, “Bend your knees more while you land.” They would look at me perplexed then likely get frustrated at the difficulty of the task. However, If I tell a runner, “land quieter,” then their noise gives them immediate feedback of success or failure in changing their running form. In a study of 14 experienced runners, a reduction in noise led to a 20% reduction in ground reaction forces.

3. Bounce

Running is differentiated from walking by phases of flight. Essentially, running consists of mini jumps. The height of the jump is proportionately related to the landing force. This can simply be measured by taking a video then noting the highest and lowest heights of the head.

A simple cue of “keep your body as low to the ground without slouching” has been shown to reduce the average forces of landing by >33%.

All runners just want to run. As a PT specializing in running, I want my clients to be able to continue to run. The three factors noted above- cadence, noise and bounce- can all be easily modified to reduce a runners pain and keep them participating in the activity they love.

Combining a gait analysis along with strength and conditioning exercises and a running plan are apart of my approach to treating injured runners. Have you been dealing with a running injury that won’t go away?