What the NFL’s thousands of players are allowed to participate in during their non-football lives isn’t totally clear.

The collective bargaining agreement prohibits them from participating in “any activity other than football which may involve a significant risk of personal injury” without consent from their club – a rule that leaves plenty of room for interpretation.

New England Patriots tight end Rob Gronkowski displayed the latest example of blurring the lines Sunday, when he got involved in some WrestleMania 33 action to help out his WWE friend, Mojo Rawley.

The Patriots reportedly signed off on Gronkowski’s participation, and the star tight end said he was medically cleared before getting in the ring, so no harm, no foul. But Gronk isn’t the first to take a risk with his offseason free time, and others haven’t been as fortunate to walk away unscathed.

A pair of 2004 top-11 draft picks, Pittsburgh Steelers quarterback Ben Roethlisberger and former Cleveland Browns tight end Kellen Winslow, suffered major injuries from motorcycle crashes in back-to-back offseasons more than a decade ago.

After his rookie season, Winslow was thrown from his motorcycle in May 2005 and suffered a torn ACL, as well as a staff infection stemming from the injury. He spent the entire 2005 season on the physically unable to perform list, but went on to have the best two-season span of his 10-year career from 2006-07.

Roethlisberger didn’t miss any time, but his situation was much more dire and received a lot more attention, as the Steelers were just months removed from a Super Bowl win in June 2006.

Big Ben wasn’t wearing a helmet when he went over his handlebars and shattered a windshield with his head. He suffered no neck, spine, or brain injuries, though he admitted that had it not been for paramedics, he would have died on site.

Despite two breaks to his jaw and a broken nose, Roethlisberger played 15 games the next season and is still the Steelers’ quarterback.

While “no motorcycles” may be an easy rule to institute for the Steelers and Browns now, Baltimore Ravens linebacker Terrell Suggs tore his Achilles allegedly doing something much less risky, playing basketball, in June 2012.

Suggs missed only eight games due to his alleged hoops accident, and played a big role in helping the Ravens win their second franchise Super Bowl.

Banning players from playing pickup basketball in the offseason is like saying you can’t go golfing or play in a charity softball game – you can say it if you want, but no one is going to listen. There are some more extreme examples, however, that teams might want to consider taking a closer look at.

Coming off a second-team All-Pro performance in 2014, Detroit Lions linebacker DeAndre Levy likely scared the crap out of his fans, coaches, teammates, and owner when he decided to go on a “wing walk” during his down time.

Seattle Seahawks tight end Jimmy Graham also likes to get some air in the offseason, though he generally stays inside the aircraft, doubling as a stunt plane pilot. He got his licence in 2012 and owns a small fleet of single-engine planes. Not only does his team approve of the aerobatics, they’ve promoted his adventures through their team website.

Going back to Gronkowski’s WWE appearance, there have been plenty of other NFLers to dabble in pro wrestling.

One member of the famous ’85 Chicago Bears team, William “The Refrigerator” Perry, took part in WrestleMania 2 just months after winning Super Bowl XX, and Adam “Pacman” Jones ventured into wrasslin’ more recently.

While Perry was under a different set of contractual language, Jones, who was suspended for all of 2007 due to his off-field conduct, spent about two months with the production, but didn’t actually wrestle due to the CBA. The cornerback managed to win the company’s tag-team title and lose it without ever being tagged in.

There doesn’t seem to be one type of non-football activity that’s more safe than the others, as seemingly normal endeavors like riding a motorcycle or playing basketball can result in injury, while wrestling and doing planes stunts can be perfectly fine.

One thing is for sure: players never stop getting creative with their time off.

Copyright © 2017 Score Media Ventures Inc. All rights reserved. Certain content reproduced under license.