By Shannon Carabajal, Army MedicineSeptember 8, 2011
FORT SAM HOUSTON, Texas, Sept. 8, 2011 -- Though the Army allows the wear of most types of minimalist running shoes with the improved physical fitness uniform and when conducting physical training in military formation, officials are urging Soldiers to transition slowly when switching from regular running shoes to those that offer less support.
Only shoes that accommodate all five toes in one compartment are authorized for wear. According to Lt. Col. Timothy Pendergrass, allied health staff officer, Office of the Surgeon General, minimalist running shoes, or MRS, offer minimal support and cushioning.
"There are no true specifications for MRS but most are extremely lightweight, low to the ground, and flexible. They have little to no cushioning in the heels and have a low slope from the heel to the toe -- called the heel-toe drop -- that makes them look more like the old racing flats than traditional running shoes," Pendergrass said.
The design encourages runners to land toward the front of their foot and move naturally through a stride cycle. Sometimes described as forefoot strike, the runner lands near the ball of the foot first, lowers the heel and rolls forward to push off over the toes. This type of stride generates minimal initial impact without sending a shock wave through the runner's body.
For runners used to traditional running shoes in which they land on their heel then roll forward to push off with the toes, transitioning to MRS too quickly can lead to injury so runners should use caution.
"Most runners have been using heel strike in traditional running shoes all their life. When changing to MRS, runners will engage the muscles in their feet, leg, and core differently. They'll need to strengthen muscles that may have played a more secondary role with traditional running shoes. They'll need to stretch muscles and tissues that have been supported in a more rigid shoe structure; and they'll need to become accustomed to the changes in sensory feedback that they'll experience with MRS.
They'll need to let the tissues, including the bones, adapt to the changes from the new shoes and different running posture. This takes time," he said.
He recommends a slow break-in period focused on strengthening the foot and leg muscles. For the first two to three weeks, Pendergrass suggests running no more than 10 percent of your normal running distance. After the initial period, runners should gradually increase their MRS distance by no more than 10 to 20 percent each week, taking at least eight weeks to fully transition to the new shoe. For some, the transition can take up to six months.
For the first four weeks, runners should avoid running two days in a row in MRS. Light jogging is OK for no more than two days in a row.
Running on different surfaces is also encouraged. A firmer surface, such as pavement, helps the foot make the transition from a cushioned environment.
Pendergrass recommends stretching the foot, calf, leg and hamstring muscles regularly during the transition as these muscles will be used more when using MRS. He encourages a functional warm-up that dynamically stretches all muscles prior to any run. After the run, runners should target specific muscles.
Above all, runners shouldn't push themselves to transition more quickly and should immediately stop running if they experience pain.
"The most important aspect to a smooth transition is to listen to your body. It will tell you when you need to slow down, and to stick with the structured transition. Don't get anxious and try to speed things along," Pendergrass said.