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. You’re injured, and it’s 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, don’t worry if your leg isn’t 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 women’s 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 won’t 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.

Nine Weeks to Recovery

(Click here to view the schedule in a new window.)

To get through the doldrums of your non-running days, you need a schedule that provides structure and poses a challenge. With this program, you don’t have to worry about losing fitness- if approached aggressively, you may come out of the water fitter than before your injury. Scott says, “I enjoyed the borderline psychotic challenge of setting duration PR’s, which peaked with a 2-hour interval session on New Year’s Eve.”

This schedule is not for the faint of heart. The program includes 5 days of deep water running per week for 8 weeks. In the 9th week, you start to reintroduce land running to your schedule. One day per week calls for a specific 30-45 minute stretching session. The 7th day calls for another form of cross training (if your injury will allow it), or rest.

When you look at the schedule, you will see a large number of interval workouts. That’s because during steady water running it is very difficult to work at a high enough intensity to maintain your fitness. Interval sessions in the water, however, give you brief breaks (both physical and mental) which allow you to work harder and obtain a superior workout. Another plus is that time passes relatively quickly when doing intervals, whereas steady water running is extremely boring.

Monday’s sessions are repeats of 1 minute 30 seconds hard followed by 30 seconds easy recovery. The first week, you warm-up and then do 2 sets of 5 intervals. After the 5th repetition, you get 2 minutes easy before launching into another 5 reps. At the end of your cooldown, you have completed 32 minutes of water running, with 15 minutes at high intensity. Over the course of the 9 weeks, Monday’s workouts progress to 3 sets of 9 reps for a total workout of 68 minutes with just over 40 minutes at high intensity.

Tuesday’s workouts consist of repeats of 2 minutes and 30 seconds with 30 seconds recovery. This is tougher mentally than Monday’s sessions because you must hold the intensity of each interval longer, while the rest remains the same. This workout is very efficient when you are pressed for time. In the 9th week, you blissfully get to go out for your first run, albeit only 10 easy minutes.

Wednesday’s workout is the toughest of the week mentally. It is the only day of the week you are asked to run in the water continuously. Scott and my wife both mastered this session, but I must admit I found it very difficult mentally. Former New York City Marathon winner, Priscilla Welch, however, had no problem with steady water running. I recall watching the Super Bowl at a New Zealand pub a few years ago with Priscilla, her husband Dave, Dick Quax, and a few others. Shortly after the kickoff, Priscilla excused herself and headed into the adjacent pool for a workout. As the New England Patriots were seriously thrashed, Priscilla kept running and running. She returned over 2 hours later, a testimony to mental tenacity.

There is no water running on Thursday. After 3 successive days in the water, you need a break. This is the perfect opportunity, however, to do the stretching that you usually put off due to a lack of time. A 30 to 45 minute session dedicated specifically to stretching will improve your flexibility, and help prevent future injuries once you are back running. A yoga class is a great alternative for this session.

On Friday, it’s back to the pool for more intervals-this time a ladder. You start with 1 minute hard followed by one minute easy, then hold the recovery at one minute and increase the duration of the hard efforts. This workout feels great on the way back down.

Saturday is very tough mentally-5 minute reps. The first week calls for 4 reps of 5 minutes hard with 1 minute easy between efforts, and you build up to 8 reps of 5 minutes hard, followed by 10 times 45 seconds hard. The challenge is to maintain your mental focus during the 5 minute efforts. During this session, I find it helpful to maintain concentration by visualising running repeat miles on the track (man, you must be hurting when you fantasize about running repeat miles!).

Sunday is either another form of cross-training such as cycling or rowing (if your injury will allow it) or rest. A long walk on Sunday will give you some of the esthetic and mental benefits of a run and will help prepare your legs for your return to land running.

(This column originally appeared in Running Times Magazine.)