Steep Uphill Walk
In an interesting study, researchers placed subjects on a treadmill and asked them to walk or run and then gradually increased the incline. They found that at very steep inclines, the biomechanics of walking and running become indistinguishable. Essentially, walking at high intensity on a steep gradient is running, except that the impact forces are much lower than they are in level-ground running. For this reason, steep uphill walking makes a great recovery run. By walking for 20 to 40 minutes at a comfortable intensity on a 12-15 percent treadmill gradient, you get neuromuscular running practice without much impact, so that your muscles and joins can recover from previous running. Try it.