The Science Of “ramping Up”: Why Aaron Glenn Playing Starters Is A Calculated Risk Worth Taking

For years, the conventional wisdom in NFL training camps was simple: wrap the starters in bubble wrap, hold them out of preseason games, save them for Week 1. And every September, like clockwork, the league watches soft-tissue injuries pile up anyway – hamstrings, calves, Achilles, all the non contact stuff that has nothing to do with getting hit and everything to do with a body that wasn’t ready to go full speed.

There’s actually a real world test of this. In 2020, the NFL canceled the entire preseason because of COVID. No joint practices, no exhibition games, nothing. Researchers compared that season’s regular season injury numbers to 2018-19 and found soft-tissue injuries jumped hard. Hamstring, groin, calf, and quad injury rates all rose, several of them by statistically significant margins. Take away the ramp up period entirely, and the injuries didn’t drop. They got worse. That’s not a theory. That happened.

The sports science explanation for why is the acute-to-chronic workload ratio, or ACWR basically a measure of how much a player’s workload in the last week compares to what his body has adapted to over the past month. Spike that ratio too fast, especially cutting straight from walkthroughs to live NFL speed, and soft tissue injury risk goes up. It’s worth saying: ACWR has real critics in the research world. Some have picked apart the math behind it, arguing it manufactures false correlations. So it’s not gospel. But the general principle underneath it bodies need a ramp, not a light switch, has more going for it than not, and the 2020 natural experiment is the strongest evidence for it we’re going to get without literally rerunning an NFL season twice.

That’s the backdrop for what Aaron Glenn is doing with the Jets right now. He said Tuesday that all of Gang Green’s starters will play in Friday’s preseason opener against Tampa Bay, with the goal of getting each starter 25-30 combined reps across the three preseason games, probably averaging somewhere around 8-10 snaps a game, not a token appearance. He did the same thing last summer against Green Bay.

Fans wince at this. Nobody wants to see a star player go down in a game that doesn’t count. But the idea that sitting starters out of preseason “protects” them doesn’t hold up well once you actually look at what happens to workload shielded players once the real season starts. Training camp practice, no matter how physical, still isn’t the same as live game speed, and there’s no way to fake that transition the body either gets exposed to it in August or it gets exposed to it in Week 1, and Week 1 is when it actually matters.

This has extra weight for the Jets specifically. New play callers on both sides Aaron Glenn’s staff on defense, Frank Reich running the offense means starters need live reps in these systems that install periods and scripted practice can’t fully replicate. Geno Smith and the new look passing game are getting their first real look Friday night, and there’s value in that beyond just health.

None of this means preseason snaps are risk-free. They’re not. Four Jets rookies have already gotten hurt during camp, before a single preseason game has been played, which is its own reminder that there’s no injury proof path through an NFL summer. Camp itself banged up plenty of players who never got near a preseason game, mostly guys on the roster bubble grinding for a job, which is a different risk profile than a starter getting a scripted 8-10 snaps. Whether it’s a joint practice in Florham Park or the lights at MetLife on Friday, the risk exists. The question was never whether to eliminate it. It’s whether ramping starters up gradually now is safer than throwing them into Week 1 cold. The data on the 2020 season says it probably is.

At some point the Jets have to just play football. Better to shake off the rust in August, with two new coordinators still figuring out their calls, than in September when the wins start counting.