There have been several attempts to explain the purpose of recovery runs. One of the more popular justifications has been the idea that such runs help to clear excess lactic acid from your muscles. Since this idea has been disproved time and again (the fact is your body doesn't produce lactic acid, but clears it on its own within an hour after working out), there is little evidence that recovery runs promote muscle repair or any other healing-related benefits often attributed to these "easy" outings.
So if that's the case, why bother? Why not just take a rest day, or maybe cross-train? While there are programs that promote only focusing on a key few workouts per week and cross-training or resting on other days, most elite runners and most training plans for intermediate or advanced runners incorporate easy runs between the harder workouts. So what's the benefit? Why do such prescriptions exist in the absence of evidence supporting their use for the "usual" reasons?
It's time to define a new motivation for continuing to use recovery runs in your training. So long as you keep them sufficiently short and easy, they can be a productive tool in your training kit. In fact, if you view them as providing some of the benefits below, you'll start thinking of them as "anticipation runs," helping you get ready not only for your next harder workout, but also to toe the starting line of your goal race as ready as possible.
More: 3 Rules for Easy Runs
Here are three reasons to treat your recovery (or anticipation) runs with the respect they deserve.
The key determinant of performance at nearly any race distance above 400m is your aerobic strength. Any workout at nearly any effort or distance is going to help improve your aerobic fitness, and such improvements should be your number one priority. For beginners, the gains can be significant. For experienced runners, the gains may occur more at the margins—but the margins are eventually what matter the most.
Yes, you can achieve aerobic gains through cross-training. But the efficiency of such gains (benefits divided by the time spent) are much greater for running, and the principle of specificity applies, meaning the more time you spend on your primary activity, the better.
More: How Cross-Training Increases Aerobic Fitness
Running While Fatigued
Perhaps one of the most important racing skills you can develop (besides a sense of pacing) is the ability to run through late-race fatigue. Successfully doing so can make the difference between a pleasant race experience with a satisfactory result and a crash-and-burn. There are three skills that help with this capability, all of which can be developed through running on tired legs, which is usually the point of recovery runs:
- Mental toughness. The act of getting out the door and putting one foot in front of the other—regardless of the pace—is a precursor to doing the same thing at a faster pace come race day. If you can't master the former, your confidence in the latter will suffer.
- Recruiting alternate muscles. As your primary running muscles get fatigued through repetition, your body learns to make subtle adjustments in the "balance of strength" it applies to the running process. It thus taps into muscle fibers that may go neglected if you only run when you are completely fresh. If these muscles aren't developed ahead of race day, don't expect them to perform when you need them.
- Maintaining good form: In spite of the need to recruit alternate muscles, it is still important to maintain good running form to keep your running economy (and therefore pace) high late in the race. Learning to do so can also help increase your injury resistance during tougher training runs, and the recovery run provides a more benign environment for doing so.
More: How to Cheat Fatigue