Rob Gronkowski has done more 2-minute drills than any tight end in history but he says he still finds it hard to train for

• NFL tight end Rob Gronkowski is known to be one of the most muscular people in sports.
• But nothing in his weightlifting routine compares to a football drill he's very familiar with.

Rob Gronkowski has become very familiar with football's two-minute drill — when an offense is trying to score in the final two minutes of the first or second half — as he's been a part of more of them than any other tight end in NFL history, including eight in Super Bowls.

Still, they haven't gotten any easier on the 32-year-old Pro-Bowler.

Gronkowski said the two-minute drill in practice and games is still, to this day, the hardest workout he's ever done. For him, it's always a hard task, but it's especially tough in the early days of pre-season training camp when he's getting back into gear after a long offseason.

"It's really hard to train for that, and once you hit the two-minute drill the first couple days of practice, and you're running a route back-to-back, and you're blocking someone back-to-back, let me tell you, that's a pretty tough conditioning challenge right there," Gronkowski told Insider. "At some points in my career, I've tapped out on two-minute drills, or I've only run five miles per hour because I was just shot!"

Gronkowski has a particularly difficult challenge during two minute drills as a tight end that combines strength training and cardio.

His position is tasked with blocking other opposing players and running routes to catch passes. He has to do it all with little-to-no rest in between plays as the two-minute drill often requires players to run right back to the line of scrimmage quickly without getting back into a huddle.

"Getting in shape to block and receive is a bit more of a challenge as a football player," Gronkowski said. "At first when you get to training camp, some days I can block really well and my receiving is just terrible, some days I can receive well and my blocking is terrible. It's really hard to fine-tune it, to be able to block and also go out for a pass on the next play."

"It's total different muscle sets, it's a total different conditioning aspect of the game," he added.

The two-minute drill contains similar aspects to high-intensity interval training (HIIT)

Transitioning from blocking to receiving without any breaks in between is similar to high-intensity interval training (HIIT) techniques.

HIIT involves giving full effort to a workout for short bursts of 30 to 60 seconds with little-to-no rest in between. The workouts target multiple muscle groups and require good cardio health and endurance.

Blocking in football is a full-body motion that uses upper-body, lower-body and core muscles. The most important muscles in blocking are the glutes, quadriceps, and hamstrings, but core and upper-body strength will still give a blocker an advantage.

Running routes in football, which requires beating defenders in coverage, comes down to speed and agility to get open, and then using strength and control in the shoulders and arms to reach out for passes and bring them in while running.

These muscles and skills come into all aspects of football, but it's only the two-minute drill that requires it all at once.