Excellent, excellent, excellent blog on running downhill from Joanna Zieger. This is something I've struggled with, and finally asked my Chi Running friends what to do. They said shorter stride, faster turnover, sit down a little. Good advice, because I was doing the exact opposite.
Check out Joanna Zieger's blog, there is some great stuff in there!
Running downhill can actually be more taxing than the grind up the hill. The inner quad (i.e. the vastus medialis, the muscle that is HUGE in cyclists) takes the brunt of downhill running, but the hips, ankles and low back are also affected. The eccentric contractions when running downhill are fighting the stretch from gravity; force on the legs is coming from two directions. Downhill running, whether it is extended amounts or just a quick burst down a steep hill, can cause lasting muscle damage.
The key to running downhill quickly without long term repercussions requires good technique and lots of practice. Most people brake when they run down a hill. Approach the hill without fear. Relax and let gravity help you. Always keep your foot plant directly under your center of mass and do not over stride. Glide smoothly down the hill with a shorter stride and higher cadence (get your cadence close to 100, which is a better way to run in general). That will shorten the length of your quadriceps muscles and minimize stress and potential muscle damage.
Incorporate hill repeats into your training, but mix it up. Choose a day where you use the uphill as “recovery” and work the downhill; this is an opportunity to execute good technique and allow you to run faster than normal. If you are running on a “rolling” course, this is also a chance to practice running well downhill. Of course, ease into this type of regimen, with just a few repeats, keep the speed restrained and start with a moderate grade, such as 2%. Over time, as your legs get used to the extra pounding, you can increase not only the length of the repeat but the grade and your pace. Let the downhills become your forte and a place to gain “free” time. Better downhill technique will translate into better overall running performance.
You can ready your body for the rigors of downhill running by doing some specific exercises in the gym or at home. Lunges, with good technique and very light dumb bells, are excellent for stability and strength building. Watch yourself in the mirror to make sure your hips stay level (http://www.exrx.net/WeightExercises/Quadriceps/DBLunge.html ). Plyometric drills, such as box jumps, hops, and bounding are also important for any runner (http://www.runningplanet.com/training/plyometrics.html).
In 2000, I returned to the St. Croix triathlon. I exited the transition to the run with Karen and an even deadlier runner, Carol Montgomery. Having spent 2 months practicing the downhills, I felt confident in my ability to run well on this hilly course. Carol made her move early and pulled ahead in the first few minutes. I trailed behind by a few seconds with Karen a few strides behind me. I knew the course well and decided to attack on an uphill and use the momentum from the downhill to extend any lead I might derive. I made my move with 2 miles to go and won the race by 25 seconds.