Training is like trying to walk a tightrope. You need to balance putting in grueling workouts and mileage with the ability to let your body recover. Favor one aspect too heavily and you’ll either have a poor performance from lack of training or get injured and overtrained from doing too much.

That’s why learning how to manage fatigue, and understanding the role it plays in endurance training, is critical to improving as a runner.

Why fatigue is neccessary

The basis for all training theory is the what we call the workout and recovery process. Running first breaks down your muscle fibers. The harder you run, the more muscle fibers you damage. Your body then works to rebuild these damaged muscle fibers, and if the recovery process goes well, these muscle fibers are repaired stronger than before. That’s how you become faster and stronger through training.

But, as you may realize, it’s nearly impossible to recover fully from a workout in 24 hours. It might be possible following a very easy day of running, but any type of speed, tempo or long run is going to require anywhere from 2 to 14 days to fully absorb and recover.

That means, unless you want only to run two or three times per week, training while fatigued is a necessary part of training — especially since we know slow, easy mileage is the best way to build aerobic endurance and is the foundation for running performance. The trick is finding that balance between running enough miles to build you aerobic capacity without overdoing the fatigue. Herein lies the “art” of training.

However, there is also a way that we can utilize this fatigue to make your training more effective.

How to use it to run faster

In training vernacular, coaches use a term called “accumulated fatigue”. This theory posits that fatigue from one workout accumulates and transfers to the next run so that you’re always starting a workout or a long run a little tired from your previous training.

This is important for longer distance races like the marathon because it’s nearly impossible to run the full distance of the race in daily training. Furthermore, if you were to start every workout fully recovered and fresh, it would be difficult to simulate how your body feels late into a race.

As such, we can strategically implement the theory of accumulated fatigue to better target the specific demands of your race.

For example, during marathon training, one of my favorite methods for introducing accumulated fatigue is to buttress the long run against a shorter, but steady paced run the day before. As an illustration, you would run six miles at marathon pace on the Saturday before your Sunday long run. Because of the harder running on Saturday, you start Sunday’s long run not at zero miles, but rather at six or eight miles, since that is the level of fatigue and glycogen depletion your body is carrying over from the previous run.

How to strike the balance

Training would be much easier — and runners much happier — if you could just train hard and fatigued all the time. But, you can’t simply continue to accumulate fatigue and run these types of workouts all the time (although some runners certainly do try). There needs to be a balance.

1. First, try to keep the specific accumulated fatigue workouts to once every two weeks and only schedule them during the race- specific portion of your training schedule. This ensures that you don’t overdo it and that you don’t get burnt out long-term.
    
2. Be sure to keep your easy runs slow. One of the most common mistakes runners make is running their easy day mileage too fast. This hinders your ability to recover and doesn’t provide any additional aerobic benefit. Research has shown that the most optimal aerobic pace for an easy run is about 65 percent of 5K pace. For a 20-minute 5K runner (6:25 pace for 5K – 7:20 pace marathoner), this would mean about 8:40 per mile on easy days.
    
3. Finally, don’t be afraid to take a down or rest week every five to six weeks where you reduce mileage by 65 to 75 percent and reduce the intensity of your workouts. These down weeks help you fully recover from and absorb previous weeks and months of training so that fatigue doesn’t build-up too much.

Hopefully, this lesson on fatigue and how you manage it will help you train more intelligently for your upcoming races.