Today marks one full week of consistent, fully gravitized, non-cross training. The tendinitis in my right foot reached a breaking point a few weeks ago and I decided to join the YMCA, hit the exercise bike, the elliptical, and any other cross training I could tolerate. My basic approach to cross training is do as little of it as possible and don't hold out hope that I will maintain running fitness. I know what you're thinking, some guys (Meb, Ritz) seem to spend considerable time swimming and biking without losing fitness. My experience couldn't be further from that vision of multi-sport training.
I've tried to emulate my running workouts on the bike or in the pool, often using heart rate monitors to judge my effort level. After a few sessions I end up finding new injuries from biking, or swimming, or aqua running. The crux of the problem (I think) lies in the fact that I, like most runners, have a big, powerful cardiovascular system that needs a lot of stimulus to get a good workout. My leg muscles, while not big, are also powerful and have been specifically developed to handle running workouts. In other words, those two systems (cardiovascular and running muscles) are strong enough to support each other getting a good workout from running.
When I try to ride a bike (or other cross training) for a workout I might use the same leg muscles, but in an entirely different movement. Those muscles are confused, underdeveloped, and weak when it comes to spinning a bike pedal in a circle. Meanwhile, I'm focused on getting my cardiovascular system a good workout so I push my legs to work harder and harder until my heart-rate finally creeps up to respectable level. This might work for one or two sessions, but soon the leg muscles will revolt. Like a freshman on a high school xc team trying to to the workouts of an experienced senior, my legs were doing the bike workout designed for a strong heart and lungs. Everything is out of balance.
I did get to try one cross training method that gets around all this frustration, the Alter-G treadmill. Using an air pressure system to slightly lift the body, it allows you to run on a treadmill at a fraction of your body weight. Running between 75% and 90% of my body weight caused me no pain in my foot and got me a solid, running specific workout. This gets around the cross training problems I mentioned above because you are using running specific muscles, and working the heart and lungs. The folks at Alter-G were nice enough to let me use one of the treadmills at their headquarters in Menlo Park. The only disadvantage I can see is that it took a few days of running on land to readjust to my full body weight. The first run post treadmill was truly miserable as my legs realized I no longer weighed 100 pounds. But, that seems a small price to pay for maintaining some fitness while rehabbing from an injury.
The foot is not 100%, but I did a 9 mile tempo on Sunday and 5x1000 this morning at the track. Next weekend I'm running the Falmouth Road Race as a fitness test and major gut check. Every day the foot improves and should be strong by the time the heavy training begins in September.
