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What does science have to say about it? "That you should practice faster the day before the game," answered Kelly, who is often very to the point in his responses.
He didn't want to get into specifics during the season because, really, he doesn't have the time to do so. He indicated that the explanation behind it would take too long and he – hopefully – has more important things to do.
"I know it worked for us in college and it worked for us in the league [with the Philadelphia Eagles]. That's why we do it," Kelly said. "We're always trying to do what's the best for us. We researched it when we were at Oregon and it worked for us. I know a lot of college teams have gone to it too."
One member of the media pointed out that the Green Bay Packers, as well as other teams, have adopted a similar approach. Although, unlike the 49ers, Tuesday's remain the day off for players – which has been typical in the past for NFL teams – and Friday's are used for mandatory player recovery treatments like deep tissue massages. However, like the 49ers, they too practice the day before a game. Kelly is not one to speculate and stated that it might be a better question for them on why they do so.
Kevin Clark of the Wall Street Journal wrote an interesting piece on the topic a couple years ago. At the time, the Green Bay Packers and the Philadelphia Eagles were at the forefront of the practice revolution.
"When Chip Kelly became the Eagles' coach in 2013, he brought with him studies about player training habits," Clark said within his article. "He installed Monday as an off day in order to guarantee rest and recovery. Then he tacked on a Saturday practice to the normal schedule, because, Kelly said, players should 'get the body moving' before a game."

Kelley L Cox-USA TODAY Sports
At the time, the process was a bit unconventional. "In football, an emphasis is put on recovery, so coaches have been keen on letting players lounge around," said Clark regarding the day prior to a game.
"Unconventional" has not been an uncommon word when describing Kelly. He is known for his implementation of science within his weekly structure. And it is a practice that is always evolving for the head coach.
"Then, the player takes a seat and attaches a sensor to his small finger to measure his heart rate variable (HRV)."
Like the fast-tempo practices, that is something new to the 49ers and their players.
Within his article, Clark went on to indicate that there was no scientific evidence that supports a more intense pre-game day workout having a greater benefit for players. It varies from sport to sport. "Cyclists, for instance, are known to push themselves hard the day before a race," said Clark. "Marathoners taper before a race but can jog or do sprints the day before."
In fact, some believe that such a practice may have the opposite effect. "Practicing the day before a game could in fact put a team at a disadvantage," said Shawn Arent, an associate professor in the department of exercise science and sport studies at Rutgers University.
No one seems to mind unconventional practices when you are winning, which is something that the 49ers hope to do more of this season. We'll have to wait and see how Kelly's techniques impact the team, who are attempting to bounce back from a disastrous 5-11 season in 2015.
The 49ers open their regular season on Monday night when they host the Los Angeles Rams at Levi's Stadium.