We have already discussed sleep’s crucial role in motor learning, specifically how the last 2 hours of an 8 hour night sleep trigger a key mechanism for plasticity. Plasticity is how the entire nervous system, and the brain itself, can change from experience; and in this case, leads to improved motor skills like running or jumping. But there are instances where your practice or competition just caused such deep exhaustion that any “replays” in your mind overnight will not increase performance anymore, but may actually harm your nervous system. What happens then, will you not learn when you sleep?
A 2008 study out of the University of Houston found that while sleep can increase movement speed and accuracy, it might do so more because of its restorative role, rather than the ability to enhance the learning process. In the study, almost 60 healthy subjects performed a common, simple motor skill test, where the subject taps their index finger as quickly as possible. It was performed in the 99th percentile in 1921 by Babe Ruth, and again in 2006 by Albert Pujols, two of the greatest baseball hitters of all time.
The authors found that small to moderate amounts of training can actually negatively affect performance due to fatigue of the nervous system. Now this is not the endurance induced exhaustion most of us associate with fatigue, but rather the dull or slow result of your nervous system being unable to replicate the same speed and accuracy as before. The study goes on to provide a framework that there are actually two processes occurring once learning of a skill has begun; the first involves facilitating performance and the second process impairs it. The major conclusion from this study is that sleep reduces the effect of the second process to allow the full benefit of the first process to be expressed.
So while the authors are not clear on the mechanisms behind this restorative process, the major theories behind neural fatigue usually include muscle damage causing impaired function (jumping lower in the last game of a tournament), and decreased athlete motivation.
The lesson remain the same; maximize hours 6 through 8 of sleep to enhance both the learning and restoration of motor skills, as you’ll likely need both.
Don’t do it halfway and get 7 hours of sleep, as you can also aim for 6 and skip each benefit.