To maximize longevity, you might think it's best to play it safe and stay cozy. But some scientists believe we should do the opposite, as exposure to extreme temperatures can trigger our bodies' own defenses against the killer diseases of old age. Chris heads for the freezing Arctic with his brothers Liam and Luke to take on the ultimate cold therapy.

As Chris bulks up for "Thor: Love and Thunder", he needs to build a body that looks right for an immortal god. But, he also wants the kind of muscles that are scientifically proven to help him stay strong and healthy as he grows older in real life. Teaming up with extreme sports guru Ross Edgley, he trains for a grueling 100-foot rope climb challenge, changing him from an ornament into an instrument.