Picture this: You beat yourself up with a massive interval session yesterday, your legs are thrashed, stairs seem like an impossible feat, you wake up with a deep insatiable hunger, and your energy levels are low. What is it time for? One of the best parts of every runner’s week: the active recovery day. Yesterday was 90 minutes of agony, today is a 30 minute shuffle.
The active recovery is something firmly implanted in almost all complete running plans. But what is the true benefit to these sessions? Do they actually help us to recover faster, or is it just a case of carrying on a running tradition?
The impact on lactate
Lactate acid is something all runners know about. When we run at lower intensities, our bodies are equipped to consume enough oxygen to facilitate the run without falling behind. This is running in an aerobic state.
When we start ramping up the intensity, our ability to consume oxygen falls behind the demands of the faster running pace. As a result, aerobic respiration is no longer sufficient, and we start to use anaerobic respiration. This anaerobic system works, but only for a limited time. As we keep running at these high intensities, lactic acid and other by-products accumulate in our muscles and we are forced to slow our pace.
One of the classic reasons coaches tell athletes to go on recovery runs the next day is to “flush out the lactic acid.”
That sounds kind of nice, but does it actually happen? No, and here’s why: As soon as you stop that anaerobic activity, your body shifts back into an aerobic state. Very quickly, once in that aerobic state, you will rid the muscles of the accumulated lactate. In other words, it is LONG gone by the time you get to your active recovery session 24 hours later.
But what about in an acute setting? Does flushing out the legs with some active recovery trump sitting around after a hard bought of running? This study from The Journal of Sports Medicine and Physical Fitness took a look at this issue.
In the study, subjects destroyed themselves for 60s of running at 150% of their V02max. Then, they either did some gentle active recovery for 20 minutes (30% of their V02max) or they did some passive recovery (sat in a chair) for 20 minutes. The researchers found the following:
The rate of lactate disappearance was much quicker in the active recovery group than the passive recovery group.
This makes sense to me. The gentle motion results in increased circulation through the legs without producing more lactate. Venous return from the legs is facilitated by contraction of the muscles in our legs, and that is why gentle movement trumps sitting in this specific measure of recovery.
That being said, even if these acute active recovery sessions CAN help to flush out lactate, is it safe to assume this is a beneficial thing?
Why flush out lactate?
In the above study, they showed that active recovery did facilitate ridding the legs of lactate more effectively than passive recovery. These researchers took it a step further and also measured maximal quad muscle strength, the ability of that muscle to do work and fatigue between the two means of recovery. Despite the enhanced ability to flush out lactate in the active recovery group, this is what they found:
There was NO difference in muscle function between the two groups.
So yes, active recovery acutely helps to ride the muscle of lactate, but there is still controversy on whether it will actually have a positive impact on performance.
Should you use active recovery at all?
I think, without a question, all runners need to use recovery runs- however sometimes I think they just need to be called “easy runs” instead. The key is to keep in mind what it is actually doing for you. If you are going for a light run the day after a hard workout, the lactate is already gone, and there is nothing left to flush out of the legs- so no, you are not flushing out the legs.
That doesn’t mean the recovery run is useless though. There is still a benefit to adding those easy runs for your overall cardiovascular fitness and running economy long-term. Accumulating mileage on a consistent basis is a key component to any successful running program.
In addition to this, some studies have also shown that the benefits of active recovery the day after, while it may not flush out lactate, it still may have a positive impact on performance in an acute way. For instance, take a look at the results from this 2010 study. 10 hours after a hard interval run, the athletes either did some active recovery in the pool OR passive recovery. 24 hours later, their time to exhaustion was measured. To my surprise, those who took the time to swim 10 hours after their interval run had a statistically significant increase in their time to exhaustion test the next day. After 10 hours, the lactate was already gone from the muscles, but for some other reason, the water recovery helped (the authors suggest maybe it has something to do with inflammation modulation).
It is also important to keep in mind that there are MANY other studies out there showing that these types of recovery sessions have no impact on performance 24 hours later, while I do not know of any of a similar design that show a detrimental impact on performance the next day.
So how should you use recovery sessions?
If you are taking part in a multi-event day (like a track meet), those active recovery sessions should never be skipped. You can view these sessions as the classic definition of active recovery: helping to enhance lactate removal and try to have an acute impact on performance (perhaps from the decreased lactate or other reasons).
For single event days or training in general, “active recovery” days should still be used. However, there is definitely controversy on whether there is actually enhanced recovery (as shown in the swimming study). However, if you view these sessions as bonus, low-intensity mileage, you will definitely be getting the benefit you expect. Either way, as long as there are not any injuries on the horizon, I think these added light sessions are time well spent!
Dr. Sean Delanghe, BSc. (Hons), DC is a chiropractor, coach, and a regular contributor to the RunWaterloo blog.
