Mail Bag Follow-Up (Guest Post)
Reader Marc Singer shared the following with us regarding a question from Friday’s Mail Bag.
I’m the reader who asked a question for your Weekly Mailbag” regarding the uncertain benefits of resting an MLB regular on his performance. I wanted to thank you for your response. I disagree somewhat with the evidence you provided on the need for periodic rest.
I agree that MLB is an unique sport due to the length of the season and interrelationship between physical, cognitive, and emotional skills and that logically the ongoing demands on these traits would be draining. I also agree that the data on Brett Gardner shows a clear performance decline over the course of a season, however, since he also receives scheduled rest when he plays regularly, I would think there would not be the statistical decline if rest was an effective intervention. In the years where he functioned more as the 4th outfielder, he still declined during the season’s second half despite not playing every day. I do not think your Sabathia example is relevant to this discussion, as he clearly has structural knee damage and his Injured List pattern is meant to manage a medical issue rather than being preventative in nature. I don’t think you can conclude “rest of position players is necessary” based on your examples in the response.
I am semi-retired, so I took up your invitation from your Mailbag response to look for some longitudinal data instead of my afternoon nap . Here is a sample of what I found based on a Google search with the query “benefits of rest on baseball performance”
* Fatigue Science (9/23/15, updated 5/7/19) has an article “5 Areas Sleep has the Greatest Impact on Athletic Performance”
* The American Academy of Sleep Medicine has a meta-analysis of studies that link fatigue and sleep to MLB performance and career longevity. Some of the analysis suggests a decline in plate discipline over the course of the season.
* The Guardian (12/13/17) has an article “The Bench Myth-Why Resting Athletes May Not be as Helpful as Teams Believe”. This is an analysis across the NFL, NBA, and MLB. One point made in the article is that from 2006-2017, teams that won the LCS first, therefore having the most rest, lost the World Series 10/11 years. The feeling is that rest, particularly if it’s prolonged, hurts baseball performance rhythm.
It appears to me that the issue is not rest, but rather sleep management. These studies are a few years old, so it’s hard to say if they’re relevant as the game has changed in the last couple of years to one of strikeouts, walks, and home runs.
I have no idea how MLB teams work with their player to encourage data driven use of the day off, but if you review the literature it looks like my suspicion that merely giving a player a day off has limited value. I can’t think of a time that a player had a day off and then had a statistical uptick that seemed related to the rest. I think it helps if the player is injured, but otherwise has no statistical value if they just follow their typical routine (or worse).
Hope this interests your “inner nerd”.