Pseudometric of the Week: MOIST

I made MOIST this week. It has nothing to do with rain, tears, or panties, but everything to do with sweat. Sweat! It’s the stuff that our skin cries, the stuff that stains our t-shirts and burns our eyes as we run on the treadmill (or actually go running in outside places). MOIST, as it was initially proposed, “measures which teams and players sweat the most.” MOIST as it is now falls woefully short of that goal, which you probably could’ve guessed it would. How am I supposed to really figure out who sweats the most without watching hundreds of games to scout for brow-wipes, pit stains, and groin-adjustments? Answer: I’m not. But I tried something, and the results of that attempt are what follows. I’ll begin by detailing the factors I thought might make MOIST somewhat of something.

Heat Index

What’s the hottest you’ve ever felt? For me it’s every time I look in the mirror. But also the one time when I was ten and ran around outside on a hot, humid Minnesota summer day and then spun around six- or seven-thousand times on a tire swing. I perspired a lot. And then I felt super sick and dehydrated and almost threw up all over the carpet of Crystal Evangelical Free Church. Moving on: a decent measure of heat is Heat Index, whose formula is really long but uses only temperature and relative humidity as inputs. Let’s say that MOIST is measuring the sweatiest person on the sweatiest possible day of the year at their home ballpark. I looked up the average high temperature and humidity for every MLB location and calculated the Heat Index for July 15th, which is the hottest day of the year on average. Domes/roofed parks were assumed to be 70 degrees, 50% humidity, which is probably off a little bit but it takes them off the MOIST leaderboards, as it should. This is the obvious one.

Race/Ethnicity/Body Composition/Age

The thought I had was: Will a huge, 33-year-old black man sweat more than a skinny, Dominican rookie? In other words, will CC Sabathia sweat more than Oscar Taveras? In still more words, does general physiology and genetic background affect how much someone sweats? If so, I could assign a score to players based on some weighted factor of their physical attributes and ethnic background. Luckily science shot down this very arduous and time-consuming idea before I could devote hours to racial profiling (of sorts). Turns out there’s absolutely no difference in sweat glands or skin-excretions when race, ethnicity, body composition, or age are considered [1,2]. I think “body composition” sounds funny, since it’s not like Drew Storen is composed of beryllium/obsidian/quartzite, but Nori Aoki is a stable emulsion of cherry blossoms, star jelly, and Legos. Regardless, these demographic factors were not included in MOIST. What this means for us is that this metric is becoming increasingly uninteresting. And yet I’m this far in and refuse to drop it! Onward!

Darkness of Uniform

The darker the uniform, the hotter it will get in the sun, the more a player will sweat. Simple, right? MAYBE! Since we’re assuming the team is at home, most teams wear white or light colors at home. That means we now have to look at the away team for the Heat Index Calculation to work and and and fuck it I don’t wanna figure this one out. It probably doesn’t really affect anything. NOT IN THE FORMULA.

Leverage Index

Teams that put themselves in more high-leverage situations will put more stress on players, which will cause them to sweat more. That’s pretty straightforward, actually. Last year the Marlins had the highest team LI at 1.13, while the Cardinals came in with the lowest at .91. Easy enough. Let’s include it even though last year’s LI probably isn’t predictive of this year’s LI; it’ll still be interesting to see who sweated the most last year.

Extra-Inning Games

Along the same lines as LI, teams that played in more extra-inning games endured more high leverage situations and also pushed their bodies beyond the 9-innings they’re conditioned to. This also isn’t predictive, really, but could be interesting in retrospect.

As far as things that could predict how sweaty a team gets, what else is there? Breeziness at field level? Impossible to measure. Number of blowing fans, towels, etc. in a team’s dugout? Also difficult to measure and impossible to gauge how it might affect sweatiness. There could be a conditioning factor, where southern teams like the Rangers might travel to cooler climates so much that when they return to Arlington their bodies are less acclimated to heat and produce more sweat. But that’s crazy complicated to figure out. So we’re stuck with Heat Index, Leverage Index, and Extra Inning games. Not a ton to go on, but I’ll crunch some numbers and poop out a leaderboard. If you’re interested, here’s the formula for MOIST: LI(2zHeatIndex*(zExtraInningGames/2))

Team	Raw MOIST	Scaled MOIST
Rangers	4.31	9.31
Royals	2.90	7.91
Cardinals	2.30	7.31
White Sox	2.28	7.28
Orioles	1.97	6.97
Reds	1.84	6.85
Nationals	1.53	6.54
Braves	1.48	6.49
Phillies	1.33	6.33
Tigers	1.27	6.28
Rockies	0.95	5.96
Cubs	0.71	5.72
Twins	0.66	5.67
Mets	0.60	5.61
Pirates	0.55	5.55
Dodgers	0.12	5.13
Indians	-0.30	4.70
Red Sox	-0.37	4.64
Yankees	-0.56	4.45
Diamondbacks	-1.16	3.85
Mariners	-1.62	3.39
Angels	-1.65	3.36
Marlins	-2.01	3.00
Giants	-2.19	2.82
Padres	-2.28	2.72
Rays	-2.30	2.71
Blue Jays	-2.31	2.69
Athletics	-2.60	2.41
Brewers	-2.77	2.24
Astros	-2.91	2.10

In the least surprising result imaginable, the Rangers play with the sweatiest conditions and sweatiest leverage in baseball. An open ballpark in Arlington is ridiculously hot and humid. They sweat A LOT there (an average high heat index of 134 on July 15th!). Peppering the top of the leaderboard are southern teams who play in open ballparks, which makes sense. The White Sox are so high because of their 1.08 LI and high number of extra inning games (the Cubs with the same Heat Index come in at #12). The bottom is almost all dome teams, and then the A’s and Giants in the cool Bay Area.

Well that was sort of fun! Now you can watch for how sweaty the Astros get at Minute Maid and think: “Boy, did MOIST get that wrong or what?” and feel a little more powerful. Next week I’ll roll out xBEPHYGROTHHx, which is bound to be super freakin weird. Happy Friday!

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Hey look I did real research:
1. Bates, G., Gazey, C., & Cena, K. (1996). Factors affecting heat illness when working in conditions of thermal stress. Journal Of Human Ergology, 25(1), 13-20.

2. Shetage, S., Traynor, M., Brown, M., Raji, M., Graham-Kalio, D., & Chilcott, R. (2014). Effect of ethnicity, gender and age on the amount and composition of residual skin surface components derived from sebum, sweat and epidermal lipids. Skin Research And Technology: Official Journal Of International Society For Bioengineering And The Skin (ISBS) [And] International Society For Digital Imaging Of Skin (ISDIS) [And] International Society For Skin Imaging (ISSI), 20(1), 97-107. doi:10.1111/srt.12091