Smiths half-marathon training is the latest feat documented on Will Smiths Bucket List , a Facebook Watch show where the now 50-year-old actor travels the globe, crossing off a series of personal challenges.

Smith in Havana
Smith in Havana

So far, Smith has done everything from skydiving in Dubai to swimming with sharks in the Bahamas to risking embarrassment by performing standup comedy in front of a sold-out crowd. But Smith says his most difficult test is the one he just underwent: running a half marathon in Havana, Cuba, with only 3 weeks to train.

I think of all the Bucket List, this is the one Im most concerned about, he says, admitting that the training made for a spiritual expansion-and an ego check.

Smith in Ali (2001)
Smith in Ali (2001)

Most people might think that's a little hard to believe, given that Smith has never not played some form of solider, athlete, or cut hero. From a detective sprinting after aliens, to a jaded superhero, to Muhammad-freaking-Ali, weve come to expect that Smith will look at least somewhat shredded on the big screen.

But the actor admits hes grown a bit out of shape and that-if he's being honest with himself-he really isn't sure he can run all 13 miles. I really got to be smart about the way I approach this race, Smith says in one training video. I gotta listen to my body. The older I get, the harder it is to shake the rust off.

Shaking the rust off in three weeks required some grueling training-including climbing stairs underwater with dumbbells, and sprinting up dunes. In the past, some film and editing magic have made Smith's impressive physical transformations look as easy as Aladdin snapping his fingers. But on Wednesday, well all get to see the real work that went into the latest challenge of his career.