If you are like many runners, you have probably been told not to run downhill because, "running downhill will hurt your knees." Contrary to this myth, running downhill is not "bad" for your knees. In fact, your knees need to run downhill in order to get stronger. Running downhill will also help increase your speed and improve your running form. The key to running downhill is to do it correctly, otherwise you could potentially hurt your knees or back.
Downhill Improves Turnover
Running downhill improves your turnover, which improves your speed. If you run cross country and/or run trail races, you will need the ability to accelerate and decelerate quickly. This is also true if you are a sprinter. Running downhill will help you to achieve this quickness, because you will naturally move your feet more quickly when you are going downhill and you will get used to taking more strides per minute. You should aim for approximately 180 strides per minute, which will give you maximum running efficiency.
Running downhill can strengthen your stabilizer muscles, which will help your downhill form as well as your general running form. Running downhill will especially strengthen your quadriceps. This will make you faster and improve your "running economy" whether you are running downhill or on flat surface. When you have weak quadriceps, it is more difficult to take more strides and longer strides (which is what makes you faster). Performing strides or running downhill increases the neuro-muscular connection between your brain and body (also known as proprioception) which will add to your speed as well.
It is true that if you run downhill incorrectly, you will probably hurt your knees. When you are running downhill, don't lean back. Even though it goes against your natural reflexes, lean slightly forward. Your body should be centered over your knees. Your midfoot (not heel) should strike the ground first. If you are making a stomping sound, like a herd of elephants, you are probably running downhill incorrectly. It is also true that if you run downhill every single day, you will probably hurt your knees. Your muscles need time to repair and rebuild. You need to vary your running exercises and surfaces to achieve the best results.Warm-Up
In most cases, you should warm-up before you start running downhill, just like you would before any other speed work out. Warm up for 10 to 15 minutes by running at an easy pace on a flat surface. Depending on whether you are doing an actual workout by running downhill or if you are just running downhill, you might also include some strides. Warming up properly will prevent injury to your knees from running downhill.