Who's going to win Sunday's Super Bowl? It may depend, in part, on which team has the most "night owls," a new study suggests.
The study found that athletes' performance throughout a given day can range widely depending on whether they're naturally early or late risers.
The night owls -- who typically woke up around 10 a.m. -- reached their athletic peak at night, while earlier risers were at their best in the early- to mid-afternoon, the researchers said.
The findings, published Jan. 29 in the journal Current Biology, might sound logical. But past studies, in various sports, have suggested that athletes usually perform best in the evening. What those studies didn't account for, according to the researchers behind the new study, was athletes' "circadian phenotype" -- a fancy term for distinguishing morning larks from night owls.
These new findings could have "many practical implications," said study co-author Roland Brandstaetter, a senior lecturer at the University of Birmingham, in England.
For one, athletes might be able to maximize their competitiveness by changing their sleep habits to fit their training or play schedules, he suggested.
"What athlete would say no, if they were given a way to increase their performance without the need for any pharmaceuticals?" Brandstaetter said. "All athletes have to follow specific regimes for their fitness, health, diet and psychology."
Paying attention to the "body clock," he added, just adds another layer to those regimens.
The study began with 121 young adults involved in competitive-level sports who all kept detailed diaries on their sleep/wake schedules, meals, training times and other daily habits.
From that group, the researchers picked 20 athletes -- average age 20 -- with comparable fitness levels, all in the same sport: field hockey. One-quarter of the study participants were naturally early birds, getting to bed by 11 p.m. and rising at 7 a.m.; one-quarter were more owlish, getting to bed later and rising around 10 a.m.; and half were somewhere in between -- typically waking around 8 a.m.
The athletes then took a series of fitness tests, at six different points over the course of the day. Overall, the researchers found, early risers typically hit their peak around noon. The 8 a.m. crowd, meanwhile, peaked a bit later, in mid-afternoon.
The late risers took the longest to reach their top performance -- not getting there till about 8 p.m. They also had the biggest variation in how well they performed across the day.
"Their whole physiology seems to be 'phase shifted' to a later time, as compared to the other two groups," Brandstaetter said.
That includes a difference in the late risers' cortisol fluctuations, he said. Cortisol is a hormone that, among other things, plays a role in muscle function.
But while the study showed clear differences in the three groups' peak-performance times, it didn't prove that trying to change an athlete's natural sleep/wake tendencies will boost performance.
"You can't infer that from this study," said Dr. Safwan Badr, immediate past president of the American Academy of Sleep Medicine.
To prove that would work, he said, researchers would have to do an "intervention" study where they recruited night owls or early birds and changed their sleep/wake cycles.
Plus, altering one's body clock would be easier said than done, according to Badr. It could also get complicated, he noted, for athletes who have to travel to different time zones to compete.
"If you're an East Coast team playing on the West Coast at night, you're really at a disadvantage," Badr said.
In fact, a 2013 study of National Football League teams found that since 1970, West Coast teams have had a major advantage over East Coast teams during night games.
Sunday's Super Bowl will be played at 6:30 p.m. EST in Glendale, Arizona -- which would seem to put the New England Patriots at a disadvantage against the Seattle Seahawks. Still, based on the new findings, the outcome might partly depend on the proportion of night owls on each team.
Brandstaetter acknowledged that this study does not prove that changing athletes' body clocks improves their performance. But it's a question his team is actively investigating.
For an elite athlete, any change that could enhance performance even a little could make a big difference, since seconds can separate medal winners from losers, Brandstaetter noted.
"The most important thing to consider here," he said, "is that just getting up at a certain time on the day of the competition will not help if this time is different from internal biological time."
Most people, of course, aren't elite athletes. But Badr said it could be worthwhile for everyday exercisers to consider the time of day when they feel they're at their best.
"That might help you enjoy physical activity more," he said.
But when it comes to sleep, Badr said the most important thing -- for all of us -- is to get enough of it.