The road ahead of you is aglow with thousands of tiny sparkling snowflakes, like diamonds in the distance. The air on your face is brisk and refreshing, but it harmonizes with the warm sun. There is bliss in these moments of winter, experienced in the solitude of a long run, where your only purpose is to continue to put one foot in front of the other.
But what if you could no longer run?
Running is one of life's most simple pleasures. For most people—young, old, heavy, thin—all you need is a little time and some inspiration. Throw on a pair of shoes and you are ready to head out the door.
That is, unless you are afflicted with an overuse injury. Overuse injuries involve damage to the tissues and bones of the lower leg and foot and include shin splints, stress fractures and plantar fasciitis. They cause not just debilitating pain but can result in broken bones and long-lasting damage. Runners afflicted by these injuries can be sidelined for months.
Doctor Bryan Heiderscheit, professor of physical therapy, and colleagues at the University of Wisconsin-Madison want to make sure this no longer happens. They are conducting research to better understand the causes of overuse injuries, and have focused on reducing the impact forces associated with running.
Every time a runner's foot strikes the ground, the ""foot-ground collision,"" the runner's feet and lower legs must absorb the impact of that collision. The force of impact can be equal to five times the body weight of the runner and may be the cause of overuse injuries. Somehow weakening these impact forces may ultimately prevent injuries.
Research has focused on how to reduce these forces. Some studies show that regularly replacing running shoes can decrease running-related impact and injury. But another study recently found that running barefoot decreases impact forces and may reduce injuries. Heiderscheit has taken a more practical approach.
In 2008, his group published a study in the Journal of the American Podiatric Medical Association examining whether cushioned insoles—foam and polyurethane inserts that are fit into running shoes to help provide cushion, support and shock absorption—reduce the impact forces associated with running.
""Trying to convince someone to run barefoot in winter in Wisconsin is tough,"" said Heiderscheit. ""If you change your shoes, OK, but throw in some insoles and extend the life of your shoes. That's $10-15 well-spent, as opposed to $100 for new shoes.""
But the scientific evidence regarding insole use is conflicted. While some studies have shown that insoles decrease impact, other studies have shown no effect. Part of the trouble in reaching a consensus owes to the many variables at work when people run. For instance, a runner who simply increases the number of steps they take while running also unconsciously changes their posture, the length of each step, and the way their feet strike the ground.
""Insoles are machine-tested for their ability to absorb impact, and of course they do,"" Heiderscheit said. ""But you have to account for the human element of running. Do the insoles change the way a person runs, does their posture change, or do the insoles work by doing what they are supposed to do: absorb impact?""
Heiderscheit and his colleagues looked at just this in their study. They first tested whether cushioned insoles reduced running-related impact forces. Sixteen healthy male and female runners with no history of overuse injury participated in the study. They were given running shoes and cushioned insoles to wear and the researchers took measurements when the runners ran in the shoes alone or in both the shoes and the insoles.
The researchers were able to measure the strength of the impact of foot-ground collisions by having runners run over a plate on the ground that measured the force of the impact. The plate also recorded the amount of time between when a runner's foot first touched the plate and when the highest force was reached. This time directly corresponds to the impact on the runner's feet and legs. Shorter times require the force of impact to be absorbed faster and put more stress on the runner's feet and legs. The researchers also used a second method to measure force, called tibial acceleration. The tibia is one of the two major bones in the lower leg and it is thrust forward each time a runner's foot collides with the ground. By measuring how quickly it moves forward, scientists can estimate the impact to the leg.
Heiderscheit and colleagues found that cushioned insoles did reduce the impact. When running in insoles, runners experienced weaker impact forces that were absorbed by their feet and legs over a longer period of time. They also experienced less tibial acceleration.
Runners wearing insoles may change their posture because of the increased comfort of insoles. Some studies have shown that if a runner changes his or her posture upon foot-ground collision, the impact of the collision is lower. So Heiderscheit then looked at whether the cushioned insoles were actually absorbing the impact or if runners were changing their posture.
A change in the angle of the knee indicates a change in posture. Heiderscheit observed that runners did not change the angle of their knees upon foot-ground collision when running in cushioned insoles. The researchers concluded that cushioned insoles reduce the forces associated with running by absorbing the impact.
While using insoles is an inexpensive solution for reducing the impact on our legs while running, Heiderscheit was quick to point out this was not an injury study.
""That is the next leap,"" he said. ""This is the key piece we need. There are not a lot of injury studies but we are headed that way now. There are a lot of challenges.""
What are these challenges? Funding, for one thing. People are running well into later life and one of the fastest-growing groups of runners is the baby boomer generation according to Heiderscheit. But researchers doing injury studies in people within this age group must compete for funding with researchers studying cancer and heart disease. Other challenges include identifying all of the risk factors that lead to running injury and controlling all of the things that can affect how a person runs, including their diet, how much sleep they have had and what shoes they wear.
If researchers can overcome these challenges, there is hope on the horizon for injured runners. Heiderscheit's group is now studying whether people can change the way they run, to reduce their risk of injury and help them recover from injury. His lab has been able to help people modify their running stride, or the steps they take while running. For people who once ran with pain, these modifications have provided some relief and many are now able to run pain free.
By taking the impact out of running, Heiderscheit and his lab are having a lot of impact on the lives of runners.
