#step rate

[bodybossteam]

Upping Your Step Rate! Your Knees Will Thank You

(image source: http://blog.saucony.com/wp-content/uploads/2012/10/StrideRate2-610x360.jpg)

“56% of recreational runners and as high as 90% of runners training for a marathon will sustain a running-related injury each year. Approximately 50% of all running-related injuries occur at the knee with nearly half of those involving the patellofemoral joint” [1].

Ah, what a great day it is today in Atlanta (Sunday when I wrote this). It’s 54 degrees, vibrantly gorgeous… this, just days after Snowpocalypse 2.0. It’s probably a great time to also write about one of the greatest physical activities people do on beautiful days like this… run. In this case, my physical therapy friend sent me an article that I was extremely interested in about step rate, and how adjustments to step rate can have a drastic impact on the force on your lower body, specifically. If you’re a runner, you’ll want to read this… and if you aren’t, you’ll want to read this anyways.

The Running Clinic in Canada posted this article from the Medicine & Science in Sports & Exercise: “Effects of Step Rate Manipulation on Joint Mechanics during Running” by a team of writers (check the footnotes below for the authors). The research was done in association with the Departments of Orthopedics and Rehabilitation and Biomedical Engineering of the University of Wisconsin-Madison.

The article delineates the effects of both energy absorption and energy generation through a step cycle on three particular joints – the ankle, knee, and hip. A [full] step cycle in this case will be the take-off and landing of one’s foot. The researchers cited that oftentimes, it’s the lower extremity joints’ inability to sufficiently control the force applied during a take-off as one of the leading causes of injuries.

So let me share with you the tables they provided regarding the Energy Absorbed and Energy Generated…

I’m not going to reproduce all the different graphs since it’s just straight from their article. However, I wanted to point out a several keypoints from the article. To better understand, “Preferred” in the above charts is the “natural” step rate of the test subjects where the -% represents a decrease in step rate, while a +% represents an increase in the step rate. And a change of up to 10% from the preferred step rate did not require a significant change in metabolic processes. As such, variances of more than 10% in either direction of the preferred step rate were not considered.

20% to 34% less energy was absorbed at the knee when the preferred step rate was increased by 5% and 10%, respectively. In fact, a decrease in step rate resulted in a proportionate increase in energy absorption at the knee.

The knee joint experienced the most significant reduction in energy reduction vs. the ankle and hip joints.

The researchers measure the load response of a full cycle – again, energy absorbed (landing) and energy generated (take-off).

The biomechanical changes when step rate was increased are similar to those found when running with barefeet or even with minimalist footwear.

As a means to adjust step rate, the researchers suggested using a metronome.

Increasing step rate can also be used not only for injury prevention, but also to re-introduce injured athletes into a running regimen.

The researchers further found that with an increased step rate, to cover the same distance, as you can imagine, would actually lower the distance between each step. As such, there was an understanding that the total energy absorbed and generated from the total volume of added steps with increased step rates may actually negate some of the benefits of an increased step rate.  However, citing shorter strides can actually reduce the risk of tibial stress fractures, the researchers concluded that the benefits would outweigh the costs.

In the end, the researchers shed light in a number of areas regarding the effects of changes in step rates with more analysis for the hip and ankle joints than I relayed here. They also described some effects and benefits of hip adduction and abduction due to lower leg extremities when increasing step rate. For more great results and analyses, do check out the article linked above.

And of course, the opening of the article discussed the focus on the energy and injury prevention using an increased step rate due to the take-off of runners. However, in many sports other than long-distance running, the landing is actually oftentimes the most injury-prone moments. There should be larger studies in a more specific group of athletes, while also measuring the impacts of the more common start and stop with more abrupt change-of-direction movements.

What are your thoughts of the study? How would you implement a change in step rate?

--------------------------------------------------

[1] Heiderscheit, B. C., Chumanov, E. S., Michalski, M. P., Wille, C. M., & Ryan, M. B. (2010). Effects of step rate manipulation on joint mechanics during running. Medicine & Science in Sports & Exercise. Retrieved from http://www.therunningclinic.ca/medias/mailinglist/2011-heiderscheit-cadence-et-for-2.pdf

[smaatfootwear]

How Leg Muscle Activity Changes as Running Step Rate is Increased

Let’s try to translate these results into a clearer description of what is happening. Imagine an overstriding runner who lands with the foot way out in front of the knee and the foot inclined 45 degrees relative to the ground at contact (like the one in the photo to the left). Generally, this type of stride is associated with a fairly low step rate. Now suppose we have this person increase their cadence by 10%. Previous work has shown that this results in the outcomes discussed above: the foot lands flatter, contact shifts closer to the body, the knee is more flexed at contact, and hip and knee loading are reduced. What’s cool about the Chumanov study is that it shows how these postural changes are accomplished at the level of the muscles. Initial leg swing is sped up by activation of the rectus femoris. At the end of swing, contact is pulled closer to the body by the hamstrings, which slow the forward swing of the lower limb just prior to contact, as well as the glutes, which start to pull the thigh back a bit prior to contact. The calf muscle pre-activates to a greater degree, and the tibialis anterior on the front of the shin reduces its activity, resulting in a flatter foot plant.