Recovery Runs

[allie]

this is an excerpt from an article i came across. i found the study to be quite interesting:


"...In short, recovery runs do not enhance recovery. Nevertheless, recovery runs are almost universally practiced by top runners. That wouldn't be the case if this type of workout weren't beneficial. So what is the real benefit of recovery runs? The real benefit of recovery runs is that they increase your fitness--perhaps almost as much as longer, faster runs do--by challenging you to run in a pre-fatigued state (i.e. a state of lingering fatigue from previous training.)

There is evidence that fitness adaptations occur not so much in proportion to how much time you spend exercising but rather in proportion to how much time you spend exercising beyond the point of initial fatigue in workouts. So-called key workouts (runs that are challenging in their pace or duration) boost fitness by taking your body well beyond the point of initial fatigue.

Recovery workouts, on the other hand, are performed entirely in a fatigued state, and therefore also boost fitness despite being shorter and/or slower than key workouts.

Evidence of the special benefit of pre-fatigued exercise comes from an interesting study out of the University of Copenhagen, Denmark. In this study, subjects exercised one leg once daily and the other leg twice every other day. The total amount of training was equal for both legs, but the leg that was trained twice every other day was forced to train in a pre-fatigued state in the afternoon (recovery) workouts, which occurred just hours after the morning workouts.

After several weeks of training in this split manner, the subjects engaged in an endurance test with both legs. The researchers found that the leg trained twice every other day increased its endurance 90 percent more than the other leg..."

"Additional research has shown that when athletes begin a workout with energy-depleted muscle fibers and lingering muscle damage from previous training, the brain alters the muscle recruitment patterns used to produce movement. Essentially, the brain tries to avoid using the worn-out muscle fibers and instead involves fresher muscle fibers that are less worn out precisely because they are less preferred under normal conditions.

When your brain is forced out of its normal muscle recruitment patterns in this manner, it finds neuromuscular "shortcuts" that enable you to run more efficiently (using less energy at any given speed) in the future. Pre-fatigued running is sort of like a flash flood that forces you to alter your normal morning commute route. The detour seems a setback at first, but in searching for an alternative way to reach the office, you might find a faster way--or at least a way that's faster under conditions that negatively affect your normal route."

[Sasha Pachev]

I found the study itself quite interesting. The full text of the study is available at

http://jap.physiology.org/cgi/content/full/98/1/93#F2

Executive summary of details left out by the article that I think are relevant. They did leg extensions for the training. The Low (glycogen) leg did 1 hour, then no food while resting 2 hours, and another hour. The High leg did 1 hour, then 1 hour the next day while the Low rested. Repeat the cycle. Maximum power increase was the same. However time to failure at 90% of maximum power went up from 5 on either leg untrained to 11 on High and 19 on Low. Also the levels of glycogen after training were higher prior to the start of exercise in Low than in High. What is interesting is that lactate, epinephrine, and norepinephrine levels were  higher in the Low post-exercise after training.

The authors of the study say that since the intensity was high enough in the 90% power to failure test, glycogen levels should not have been a factor in reaching the failure. However, here is what is interesting. It seems that the Low leg did a better job of pushing itself (evidence being higher levels of lactate and epinephrine/norepinephrine). It outperformed the High not because of aerobic superiority or increase in strength, but because it just learned to push itself better.

I am willing to believe that the higher glycogen levels lead to being able to push yourself better. I know from experience that the first sign that you are going to hit the wall in 5 miles is that you lose your ability to surge and start struggling on hills.

As far as recovery runs, the study is rather inconclusive. Leg extension does not quite carry over into running. The aerobic component does not play a factor nearly as much as it does in running. In fact, one interesting thing is that the High leg seems to have developed better aerobically - lower lactate at the same intensity. But it was still failing miserably compared to Low in 90% max power to failure test.

[Jeff Linger]

Brain Training for Runners (Matt Fitzgerald) tends to agree. Here is a post on this exact subject I posted quite some time ago.

http://fastrunningblog.com/forum/index.php/topic,826.0/topicseen.html