You are guilty of enjoying your running too much and ignoring the early warning signs of an injury. Your sentence is 8 weeks off from running. Youíre injured, and itís a big one. The doc says absolutely no running for 8 weeks and then a gradual return. This is the news Scott Douglas received this past October-stress fracture of the tibia.
Scott sent me an SOS by e-mail. He asked for a cross-training plan that would keep him fit and preserve his sanity while his shin recovered. Having endured similar trials myself (and vicariously through my wife) I knew Scott would be frustrated and worried that he would rapidly lose fitness. Just as importantly, his usual form of stress relief would be missing. The challenge was to design a training schedule hard enough to maintain fitness for a well-trained runner, but not so hard that he would become discouraged and quit before the injury was fully healed.
Most of the benefits of training are reversible. Your cardiovascular fitness decreases measurably after 2-3 weeks without training. Studies have shown, however, that with reduced training you can maintain your fitness at almost the same level for several months. The intensity and specificity of cross training workouts are most important in determining how much fitness you lose when you take time off from running. You must do some training above 70% of VO2 max in order to maintain your aerobic fitness and racing performances. Of course, you need to find a method of cross training that will allow your injury to heal.
Why deep water running?
Depending on your specific injury, you may be able to cycle, row, or use a cross country skiing simulator. If you can do these activities without interfering with your recovery, then by all means include them in your cross training program. Unfortunately, a number of running injuries are aggravated by these other types of exercise. Fortunately, with most running injuries, you can safely run in the water. Deep water running with a flotation vest provides an excellent training stimulus, and more closely simulates land running than most other cross training options. Running in the water is a total body exercise that works your legs, trunk, and arms, and positively stresses your cardiovascular system.
Several studies have verified that deep water running can be used by runners to maintain fitness. Investigators from Florida State University coerced a group of trained male runners to run in the water while another group continued regular training. The runners were tested for VO2 max, lactate threshold, and running economy before and after 6 weeks of water running. The water running group fully maintained their aerobic fitness over the 6 weeks. Similarly, a study by Ed Eyestone (yes that Ed Eyestone) and colleagues at Brigham Young University found no change in 2 mile run time after runners trained in the water for 6 weeks. Additional support for the fitness benefits of water running is provided by a study from the exercise physiology lab at the University of Toledo, in which trained runners ran in the water 5 to 6 days per week for 4 weeks. These runners had no change in 5 km performance time, VO2 max, lactate threshold, or running economy after 4 weeks of water running. So, there is little question that water running is an effective method for runners to stay fit.
Water running technique
Water running technique is an area of some debate. Some coaches insist that you try to simulate land running form as closely as possible. While that is a nice ideal, I believe that the most important consideration is to maintain your training intensity to the degree possible, and if your form needs improvement, so be it. Regardless of your running form, your stride rate will be slower during water running due to the increased resistance of moving your legs through water. If you try to simulate land running too closely, your stride rate will be even slower. For that reason, donít worry if your leg isnít brought behind the body to the same degree as in land running-find a happy compromise with decent form and a reasonable rate of leg turnover.
Some athletes move forward while running in the water, and actually do laps during their workouts. Whether you move forward or remain relatively still depends on subtle changes in body position. I recommend a relatively upright posture during water running which will work your trunk muscles and result in only a slight tendency to move forward through the water.
Gauging your effort
You will not be able to achieve as high a heart rate running in the water as running on land. A study from the famed Karolinska Institute in Stockholm found that heart rate is 8-11 beats per minute lower for the same oxygen uptake when running in the water compared to normal running. This study also found maximal heart rate on average to be 16 beats per minute lower during all-out water running compared to land running. Lower heart rates during water running are primarily due to the pressure of water on the body which makes more blood return to the heart so more blood is pumped with each heart beat.
A useful rule of thumb is that heart rates during water running are about 10% lower than during land running. If you get your heart rate up to 140 beats per minute in the water, that is roughly equal to 154 beats per minute during normal running. The temperature of the water affects your heart rate during deep water running. Your heart rate will be lower in cool water and higher in warm water. In addition, two studies have found that women have slightly lower heart rates and oxygen consumption than men during deep water running. This is thought to be due to womenís generally higher bodyfat content and resultant greater buoyancy than men.
The Karolinska study found that perceived exertion is higher during water running for a given heart rate or level of oxygen consumption. So, in order to get a beneficial workout in the water, you will feel that you are working harder than during land running. For this reason, the 9-week schedule emphasizes interval workouts in the water. If you just do steady water running sessions your effort wonít be high enough to maintain your fitness. A study on water running by former 800 meter runner Tim Quinn, Ph.D., and colleagues at the University of New Hampshire concluded that for runners to maintain fitness during water running it is necessary to include intervals, tempo, and/or fartlek training.