It's a growing football buzzword and philosophy that has and will continue to become commonplace at Penn State because of the massive scholarship reductions.
Football players love hitting each other, delivering bone-crunching body blows, primarily to the opposition and even to their own teammates in practice. However, with only 66 scholarship players on the roster this year and a limit of 65 the next four years, the Nittany Lions simply cannot afford to take too many chances overhitting in practice and risk losing players to injury.
"It's a contact sport. It's a collision sport. And it's played by guys that are tough guys and physically tough and like to hit each other," PSU coach Bill O'Brien said.
O'Brien's No. 1 concern, though, is making sure he keeps his players healthy because of significant depth issues, so Penn State is adopting a different mentality to the way it practices.
The Lions are going to more thud drills, which are simple in theory but do pose some questions. Thud is basically the defenders hitting the offensive player - creating a thud - but not following through with the tackle all the way to the ground and not leaving their feet.
"We've come up with different drills that practice tackling without tackling, if that makes sense," O'Brien said. "[We work on] angles and we call it tagging off and being in proper position. Hit, face guy up, be in proper position, let them go."
Thud drills have become standard procedure in the NFL, where there's so much money at stake that players can't afford to get hurt in practice. But as O'Brien pointed out, "It's very difficult for college kids" to practice that way because they can't always tone down their aggressiveness.
Penn State worked on thud drills a lot during the spring, and it will be a big part of how they practice going forward.
"We're still hitting in practice," linebacker Glenn Carson said. "Thud gets pretty physical, and basically you're doing everything, just not taking the running back to the ground."
The upside of that is easy - fewer injuries.
Still, as all athletes know, you practice how you play, and in football that has always meant hitting and hitting and more hitting. By taking away some of the players' ability to practice all out, the fear is it doesn't prepare them as well for the physical rigors of an entire game.
"We still have scrimmages, and we still take guys to the ground and things like that," Carson said. "But thud is probably the majority of time that we're doing and practicing. I think we all get a lot out of it. I really don't think it's necessary tackling."
To help keep his players fresh, O'Brien plans to limit hitting primarily to one day a week during the season, on Tuesdays. He realizes that's not ideal.
"If I had 85 kids on scholarship," he said, "I'd probably knock them around on Tuesday and Wednesday and Thursday. But I can't do that."
O'Brien's experience dealing with smaller rosters in the NFL can help in these circumstances as he's already familiar with ways to limit contact and still get the most out of practice. It just comes down to thinking outside the box.
"Maybe it's a night walkthrough instead of having a night practice, things like that," O'Brien said. "Maybe it's a little bit less 9-on-7 and maybe another 7-on-7 that's no contact."
Staying on top of every injury - big or small - also will be of great importance with only 65 scholarships.
"What you have to do is every single day, every minute of the day as a head football coach, you have to make sure you're in tune with the health of your football team," O'Brien said.
If a player comes to him saying he's hurting a little bit, the coach noted, "Then you taper it down a little bit for that individual kid. And then maybe you do it for the whole team."
One area O'Brien does plan to push players a little harder is on Mondays with the younger, developmental guys on the team, such as the scout teamers and run-ons. He plans to treat it like a practice squad in the NFL, letting those players who didn't appear in the game the previous Saturday go out and scrimmage and see how much they can improve.
If there's an enormous dropoff in talent on the bottom third of the roster, then those players will never be able to push the team's best players to get even better in practice.
And, with only 65 scholarships, Penn State ultimately figures to have to count on a good number of the run-ons to help out in game situations.
"The years ahead aren't going to be easy," O'Brien said of the depth concerns, "but we have a better handle on things."