The actor has fronted the show since it debuted in 2010 and now he's hoping for an eighth season pick-up so he can exit the drama with a meaty storyline.

"I have an end date," he tells news show Entertainment Tonight. "I signed two more years, seasons seven and eight, and then I’m done. I got too many injuries to contend with."

Alex, who plays Hawaii top cop Steve MCGarrett on the show, admits a back injury has really slowed him down and he's beginning to regret going full-on with stuntwork, because his injuries aren't healing as quickly as they once did.

"This show is really important to me and I’m pretty sure the world can see that with what I bring," he adds. "I really care about these characters and I’ve never phoned in my performances. Every single day, no matter how tired I am, I give it everything I can to make it as good as it can be but that takes a toll.

"I think if I’d have been an actor who didn’t care, I’d have less grey hair and I’d be a lot less tired. But I’m really tired. I do a lot of heavy lifting on the show... That’s cool, but it has to end.

"My body’s pretty broken up. I got through most of them - the last surgery I had on my elbow, I came to work the next day at 5.30am; I just had them bandage my elbow. I’ve pushed through all of them but I’ve got a back injury now and this one’s really sort of slowed me down. It’s also forced me to look at my future and what I’ve realised is I want to be able to throw a football with my grandkids. I want to be moving my life. A TV show is not worth that."