You've heard of overtraining. Overtraining can be defined as a decline in athletic performance caused by subjecting the body to more training stress than it can properly adapt to in a given period of time.
In extreme cases, overtraining becomes overtraining syndrome, a severe disorder of the nervous, endocrine and immune systems that requires many weeks of rest to fully recover from.
Even moderate cases of overtraining can seriously disrupt the training process and thus must be scrupulously avoided. There is, however, a sort of gray zone between training progressively, well within one's adaptive limits, and overtraining—a middle zone that is well worth visiting on rare occasions in the training process.
I'm talking about overreaching, which is a short period of training stress that slightly exceeds the body's adaptive limits but is terminated before it causes the performance decline associated with overtraining.
There is no universally agreed-upon definition of overreaching in endurance sports training. Some coaches actually use the word "overreaching" as a synonym for "overtraining." Others say that you are overreaching anytime you are training hard enough to generate fatigue and a need for recovery.
My definition of overreaching splits the difference. I say you are overreaching when you are training hard enough so that, after seven to 10 days, your performance begins to decline due to accumulating fatigue. But the art of overreaching lies in cutting back your training as soon as you reach that threshold of performance decline in order to give your body a chance to adapt to all of that hard work.
What is the rationale for overreaching? It certainly is not a necessary feature of triathlon training. You can get fit enough to race well by merely training progressively—that is, by increasing your training load very slightly from week to week for many weeks, with the occasional reduced-training recovery period thrown in. But effective use of overreaching will raise your fitness to even higher levels.
The greater the amount of specific training you do without exceeding your body's limits, the fitter you will become. Overreaching is simply a way to pack a little extra training into your program through controlled risk-taking. That's why it is widely practiced by elite endurance athletes.
To gain a better understanding of the rationale for overreaching, it is helpful to consider the difference between acute and chronic training stimuli. An acute training stimulus is a single workout that is challenging enough to stimulate improved fitness. A chronic training stimulus is a sequence of workouts in which perhaps no single workout tests your limits, but the sum of them does because your burden of fatigue increases as you go.
Endurance training always relies more on chronic than acute training stimuli because it's the total volume of training that has the greatest effect on fitness. Volume is necessarily limited when individual workouts are extremely challenging.
Strength athletes are often heard bellowing about the need to give 100 percent in every workout and to leave the gym crawling and trailing vomit. Endurance athletes can't do that. Rather, they need to train in a way that gradually reduces them to crawling at the end of each week or training block.
Overreaching is simply a training strategy that puts even more emphasis than normal on chronic versus acute training stimuli. There are hard individual workouts, to be sure, but the real challenge comes from the sheer volume of training that an athlete takes on.
Not for Beginners
Because of their genetic gifts and experience, elite athletes are able to make more liberal use of overreaching than you or I could without risking serious injury. A pro might overreach for three straight weeks on two separate occasions during focused training for a major competition.
Everyday athletes like us should begin with just one week of overreaching in the final weeks of preparation for an upcoming race. If that goes well, you may advance to two and eventually three or four non-consecutive weeks of overreaching when training for future events.