To control injuries, you need to understand their root causes. The root cause is usually predictable-the system is pushed too hard and the weakest link gives out. Running injuries can usually be prevented, therefore, by increasing the ability of your tissues to tolerate a force repeatedly, or by decreasing the cumulative amount of impact shock your tissues must withstand. In the last Pfitzinger Lab Report, we looked at how to prevent injuries by correcting muscle imbalances. This month we look at the other side of the injury equation- minimizing the amount of shock your body must absorb.
You can reduce the cumulative amount of shock imposed on your body in several ways. One solution, of course, is simply to stop running, and this advice is frequently doled out to injured runners. Fortunately, there are other less drastic solutions, such as adjusting your running surface and terrain, shoes, and mileage. In a 1993 review in Sports Medicine, Dr. Michael Gross of Orthopaedic and Sports Medicine Associates of Emerson, New Jersey explained, "Most overuse syndromes will respond to rest, training modification, and a change in the running surface or shoe."
Running surface and terrain
The total force absorbed by your body during running can be calculated as the amount of force per step times the number of steps you take. Adjusting either of these factors will reduce your risk of injury. Let's look at the amount of force per step first. The surface that you run on can make a substantial difference in the amount of pounding absorbed by your body. This difference may determine whether or not you cross your threshold for injury.
Concrete is the least forgiving surface for running. Unfortunately, many runners are forced to do a portion of their mileage on concrete, particularly the lunchtime running crowd. Shin splints and stress fractures incurred on concrete may be prevented by running on a softer surface. Blacktop or asphalt, while slightly softer than concrete, is far from an ideal running surface. Our bodies did not evolve while running on a uniform hard surface. Your joints, muscles, tendons, ligaments and bones are not designed to withstand hundreds of miles of running on roads. Search for natural surfaces-dirt paths, grass fields, golf courses, trails-anywhere that will allow you to run with less shock and less chance of injury. The higher the percentage of your training that you do off-road, the lower your likelihood of developing overuse injuries.
A 1997 study by Dr. Carmelo Bosco and colleagues at the University of Rome, published in Ergonomics investigated the effect of the hardness of the surface on the efficiency of jumping. The investigators concluded that "soft surfaces may favor a very low rate of running injuries."
If you feel as though you are on the verge of an injury, avoid downhill running. The impact forces of downhill running are significantly greater than for level running, so by avoiding downhills you may prevent an injury from occurring.
Are your shoes dead?
Keeping your shoes in good condition can make a big difference in the amount of shock that your body absorbs. As of this writing, the cushioning properties of all running shoes on the market break down substantially after less than 800 miles of running. For those training 20 miles per week, this represents 40 weeks of use. For the 100 mile a week crowd, 800 miles are reached in only 8 weeks. Depending on your size, running mechanics, and what model shoe you wear, you may need to replace your running shoes after as little as 400 miles.
It is also a good idea to use different pairs of running shoes on different days. The forces your body must deal with are altered somewhat by different pairs of shoes. By switching shoes, you make the shock that your feet, legs and back receive somewhat less repetitive. This reduction in the repetitiveness of the forces may thwart the development of an injury. And, although you have to buy an extra pair of shoes now, each pair will last longer. In addition, research has shown that it takes time for the resiliency of your shoes to completely return after running. For this reason, if you train twice a day (committed), rotating shoes is even more important for injury prevention.
The total amount of shock your body must deal with is also determined by how far you run. A 1992 study published in Sports Medicine observed that although running experience was associated with a decreased injury rate, that weekly mileage was the strongest predictor of a future running injury. The challenge is to maintain an outstanding fitness level by replacing some of your running mileage. Replacement mileage doesn't mean cutting back on training. After all, this is the magazine for the serious runner. Those miles just get replaced with other forms of aerobic training. Cross-training allows you to maintain your cardiovascular fitness without adding to the number of times that your feet strike the ground. Cross-training is a particularly good option for recovery training. You improve the recovery process by pumping blood to the muscles, and do not add to the cumulative pounding on tissues.
Cycling, rowing, swimming, running in water, in-line skating, cross country skiing, stair climbing, slideboarding, elliptical training, arm cranking, and other options are available for working out without the impact of running. Unfortunately, there is no foolproof way to equate cross-training to running mileage. Running is running, cycling is cycling, etc. Because your muscles adapt specifically to the type of training you do, the closest substitute to running is running in water with a flotation vest. Because there is no contact with the ground, however, even water running does not replicate the muscular demands of running on land.
Finally, if you feel an injury coming on, take a day or two off now to allow your muscles and connective tissue to recover, and resiliency to improve. In this way, you will miss a couple of days now and then rather than several weeks with a serious injury. Many injuries can be prevented. By developing a strategy to prevent injuries, you can take more control over your running.
(This column originally appeared in Running Times Magazine.)