Guest column by Brian Stonelake
Are you an NFL fan? Of course you are. OK, think of your favorite team. Other than your quarterback, name the player who most influences your team's success. What if I told you that the NFL created a rule mandating four arbitrary road-game suspensions for this player? Houston fans: no J.J. Watt. Patriots fans: prepare to be Gronkless. Worse yet, this rule only applies to a handful of teams.
Recently the league released its 2016 schedule and (of course) they implemented no such rule. Unfortunately, they did quantifiably worse.
To understand the NFL's blatant error, allow me to provide a crash course in the pertinent area of chronobiology. To oversimplify: many aspects of exercise performance suffer in the morning. I don't mean the morning after a night with a teething toddler, or following a Super Bowl party with too much whiskey, I mean when fully awake and well rested. Numerous biological functions relevant to sport follow the core body temperature cycle, which is at its lowest early in the morning, and highest in the early evening.
This circadian rhythm does not adjust quickly, so while Week 14's 1 p.m. (EST) kickoff will feel like 1 p.m. for the host Panthers, it will feel much earlier for the visiting Chargers, whose body clocks are still synchronized with West Coast time. During such games, dubbed "morning body clock games," the West Coast visitors' circadian rhythms present a chronobiological disadvantage. Do not confuse this with being "tired;" this is a physiologically determined handicap directly affecting many aspects of exercise performance. For example, every 0.1℉ decrease in core body temperature results in a nerve conduction velocity decrease of 0.432 m/sec, directly reducing reaction time. These players aren't sluggish and tired; they're biologically mandated to react more slowly.
One might assume that at worst the physiological handicap provides a marginal advantage for the East Coast home team, an impact that would have little practical implication. But the impact is actually quite significant.
From 2001 to 2015, there were 374 NFL games where the road team faced a "morning body clock" start time. All 374 involved a Central or East Coast team hosting a team from the West or Mountain time zones (hereafter aggregated as "West" due to the scarcity of Mountain teams). The home team won 64.4 percent of these games; far in excess of the 57.2 percent win rate for home teams in general.
This statistically significant difference in win percentage (P = 0.002) did not happen by accident. You can cut the data however you want, controlling for any factor that you wish, and still come to the same indisputable conclusion: teams playing a morning body clock start time face a significant competitive disadvantage.
This shocking result makes more sense when you consider the numerous aspects of performance that oscillate daily with core body temperature. An incomplete list includes respiratory efficiency, blood flow, joint flexibility, reaction time, and muscle strength. Further, at suboptimal body clock times, athletes record lower mean and peak power outputs, lesser peaks of lactate production, decreased high intensity work rates, and lessened stamina. Conversely in the late afternoon/early evening hours, not only are athletes' self-chosen work rates higher, but these efforts are not accompanied by an increase in perceived exertion.
Given the above, it's not surprising that nearly every Olympic world record was set in the late afternoon or early evening. While scheduling considerations may explain some of this, tests isolating body clock time reveal up to a 10 percent decrease in aspects of athletic performance in the morning. For comparison, a 10 percent decrement in performance is also seen when consuming the legal limit of alcohol, or after three consecutive nights of only three hours of sleep. Are the Niners playing like they're horribly sleep-deprived? Do the Chargers look drunk out there? Essentially, they are.
With a better understanding of the chronobiological detriments faced by morning body clock teams, we can look for the expected results in specific areas of play. Playing a morning body clock start increases the frequency of penalties accepted by the opponent (henceforth "penalties"), turnovers per game, and dropped passes. Importantly, from the league's perspective, this serves not only as justification for the competitive imbalance, but also as evidence that these games do not represent the best product that the NFL can put forward.
Both penalty and turnover prevalence are greater in general for road teams than for home teams. Controlling for this fact by comparing morning body clock teams' penalties and turnovers to those of other road teams, we see the physiologically expected increases. From 2003 to 2014 (the available data) visiting teams averaged 6.49 penalties and 1.71 turnovers per game. Teams playing a morning body clock game amassed 7.16 penalties and turned the ball over on average 1.83 times per game; increases of 10.3 and 7.1 percent respectively. These increases are both statistically significant. Due in part to a smaller (relative) variance in penalties, the increase in penalties is statistically significant at a higher level (P < 0.0001) than for turnovers (P = 0.0435).
Further supporting the narrative of sloppy play is the physiologically expected increase in pass drop rate for morning body clock teams. To avoid the possible bias of trailing teams throwing more frequently, pass drop rates are examined in lieu of pass drop totals. (This data was only available from 2006 to 2014.)
We again see the expected increase in pass drop rate among teams playing morning body clock games (5.41 percent compared to the 4.97 percent rate of all other visiting teams), but this time not conclusively (P = 0.0719). The relatively small sample size and factors such as prevent defenses employed late in games by teams with large leads may have masked this correlation.
Looking at every game for the past 15 years, we see that on average scheduling a morning body clock game costs the visitor slightly more than 3 points. Not surprisingly, these results are anticipated by bookmakers who show similar shifts in point spreads for such games. When the league decided to schedule the kickoff for the Rams' Week 13 trip to New England at 1:05 EST instead of, say, 4:05 EST, they handed the Patriots 3 points in addition to the normal home-field advantage. The magnitude of this advantage is hard to overstate.
In August 2013, R.J. Bell wrote an informative piece for Grantland where he found a Las Vegas consensus for the value of NFL players, as measured by a hypothetical point spread change if they were hurt. The highest non-quarterback was Adrian Peterson, who was coming off a 2,097-yard MVP season where he averaged an astounding 6.0 yards per carry. He was estimated to be worth 2.5 points. In other words, Las Vegas measures the competitive disadvantage faced by morning body clock teams to be slightly greater than that associated with losing one of the most dominant offensive players in NFL history. Welcome back to L.A., Rams. We regret to inform you that you will now face an unavoidable handicap far more important than a hypothetical injury to Todd Gurley in half of your 2016 road games.
The next highest valued non-QB in Bell's piece was Calvin Johnson, who led the league in receptions and yards the year prior, and was valued at 1.5 points. The only defensive player worth more than half a point was J.J. Watt, estimated to be worth 1 point. Quarterbacks were worth as much as 7 points (Peyton Manning), with Russell Wilson, Andrew Luck, Tony Romo, and Sam Bradford all being worth 3 points. In other words, when the Seahawks played at Indianapolis in Week 5 that year (a game in which Seattle suffered its first loss), they should have been indifferent between playing the game at 1 p.m. EST as scheduled, and agreeing to play Tarvaris Jackson instead of Russell Wilson behind center in exchange for moving the game to 4 p.m. EST. With all due respect to the former Alabama State quarterback, that is astounding.
Conveniently, last year's playoffs provide a wonderful application of Bell's piece. Two days prior to Seattle's wild-card playoff game in Minnesota, the Seahawks announced that star tailback Marshawn Lynch, who was deemed by Coach Carroll to be "ready to rock" on Monday and a "full go" at practice Wednesday, would not play Sunday. This news sent shockwaves around the football universe and was a top story on many sports news outlets.
The unexpected nature of the Lynch announcement made it easy to quantify, as the betting line quickly adjusted 1.5 points. Losing their pro bowl tailback, in frigid conditions where a running game is paramount, with only a practice squad player as a backup (Thomas Rawls had already been ruled out with a broken ankle), was roughly half as important as the largely overlooked morning body clock start time.
But wait, you counter, didn't Seattle win that game? Yes, they did. The chronobiological disadvantage, like any disadvantage, is not impossible to overcome. Seattle was a far superior team, having the best DVOA in football (Minnesota was 11th), and at 6:1 the best Super Bowl odds of all teams playing wild-card weekend (Minnesota was 35:1). That, and a little bit of luck (like Blair Walsh missing a 27-yard field goal to take the lead with less than a minute to go) can overcome most any disadvantage. But that does not change the fact that Seattle faced a completely unfair disadvantage in the first place.
Well OK, you admit, but maybe Seattle should have gotten a higher seed to avoid playoff road games all together. Yes, a higher seed would have prevented the unfair situation from occurring in this instance, but why should certain teams have to overcome a systematic disadvantage in the regular season just to avoid possibly facing that same disadvantage in the playoffs? Why should Seattle face a disadvantage that East Coast teams with a No. 5 seed would not face?
The very next week Seattle was scheduled to play another morning body clock game, this time in Carolina. In the first half of this game, when the Seahawks were at their largest chronobiological disadvantage, they were outscored 31-0. They eventually lost 31-24.
The staggering effect of the morning body clock disadvantage is nothing new to Seattle. In the Pete Carroll era, they have been outscored 75-0 in the first half of morning body clock playoff games. Dating back to 2003, they have faced six such games in the postseason, their lone win coming in the aforementioned case of Blair Walsh's missed chip-shot field goal.
Fine, you concede, you win; It's a disadvantage. But are these teams any worse off than East Coast teams that have to play West Coast prime-time games ("night body clock")? In a word, yes. Look back to the core body temperature cycle chart. The difference in body temperature between 10 a.m. and 1 p.m. is far greater than the difference between, say 8 p.m. and 11 p.m. Also, body clocks adjust more quickly to westward travel (92 min/day) than they do to eastward travel (57 min/day). And while there is an increase in home team win percentage (60.7) in night body clock games compared to normal home field advantage (57.5), it is not of the same magnitude as morning body clock games (64.4). And even if this disadvantage was the same (it's not), it is far less common; there are roughly five times as many morning body clock games as night. Put differently, a West Coast team faces the larger morning clock handicap roughly 20 times for every one time the East Coast team faces the lesser night body clock handicap.
Inexplicably, despite being made aware of this competitive disadvantage, the NFL still schedules morning body clock games with high frequency. In 2008, East Coast teams claiming a competitive disadvantage associated with travel distance successfully lobbied the league to make schedule changes, yet years of discussion on the morning body clock issue from West Coast teams have seemingly fallen upon deaf ears. I am shocked that West Coast fans, especially those as obnoxiously loud as Seattle's, allow their teams to be so severely handicapped. Some foolishly hide behind anecdotal evidence pointing to games where morning body clock teams win. Yeah, the claim is not that playing in the morning is an insurmountable detriment, but rather that it is a significant detriment. I've seen teams block punts with only ten men on the field. Would that make a new rule limiting West Coast teams to ten payers in punt return situations any less fair?
While total eradication of morning body clock games would be difficult given the complexity of the NFL schedule, it seems as though such occurrences should be greatly reduced (and playoff occurrences eliminated). The most logical fix is to shift the majority of these starts from 1 p.m. EST to 4 p.m. EST. While this creates unwanted competition with the NFL's national game, it seems to be a small price to pay for the integrity of the sport.
It is worth noting that for the non-prime time games of the past 15 years, there is a 68-32 percent split between the first and second TV time slots (games starting at approximately 1 p.m. and 4 p.m. EST respectively). Had all 374 morning body clock games been moved to the second TV time slot, in addition to righting one of the worst wrongs in professional sports, it would have amounted to a more equitable 56 to 44 percent split of games: seemingly advantageous to the fan who prefers to watch as much football as possible. The rise in popularity of fantasy sports, for example, would seem to suggest a preference toward a more equal split of games among these time periods.
This topic was brought to the attention of Commissioner Roger Goodell prior to the 2009 season, at which point he was quoted as saying that he "had not seen specific information suggesting early starts [for West Coast teams traveling east] could create a competitive disadvantage for visiting teams."
To Commissioner Goodell's credit, he revisited the subject in October 2012 with a much more sympathetic view of the situation, saying that "Several of our teams on the West Coast have raised that [issue of morning body clock games] and we have been studying it. We have tried to put as many of those games on the East Coast at 4 p.m. You can imagine the thousands of different issues you have to put into the schedule. But the 10 o'clock starts are pretty tough."
Despite this statement, little has actually been done in terms of scheduling. Since 2001, there have been anywhere from 16 to 31 morning body clock games, with an average of 25 per year. This accounts for more than half of all road games for the affected West Coast teams. This year, after months of consideration and millions of dollars dedicated to creating the schedule, the NFL announced 27 more.
Hardest hit are the Raiders, who face five such games, all in the first half of the season. Should San Diego fans find their team in contention in November, they would be wise to temper their postseason expectations as their last three road games are all morning body clock starts. Seahawks fans still reeling from their unfair playoff matchups can take some solace in knowing that they only face two morning clock games this year; however an educated fan would quickly point out that this is two too many.
A combination of public misunderstanding and the league's denial has allowed this travesty to go on for far too long. The NFL has gone to great lengths to maintain a level playing field, yet allows this audacious injustice to continue. It is the duty of every fan of the NFL, whether your team is adversely affected by this competitive disadvantage or not, to educate yourself and your fellow fans on this matter. This great game deserves better.
Note: A more detailed examination of this matter can be found in "Managing the Body Clock," published in the February 2016 issue of the American Society of Exercise Physiologists' Journal of Exercise Physiology.
Brian Stonelake teaches math and statistics at Southern Oregon University; you can contact him at stonelakb-at-sou.edu.