Watch Limitless with Chris Hemsworth

So far, Chris has done everything possible to delay the aging process. Now he's facing his most extreme and emotional challenge: three days in a retirement village while wearing an aging suit that turns the simplest activity into a Herculean task. He's testing the theory that the best way to combat aging and fear of mortality might not be to fight it but accept it.

Chris has always worked to keep his body healthy; now it's time to start looking after his brain. Neurologist Dr. Sharon Sha challenges him to go off-grid into the wilderness without a GPS or map. Teaming up with his buddy, First Nations artist Otis Hope Carey, Chris will need to tune into nature to navigate through Otis's remote ancestral homeland. The hike stirs up Chris's most precious memories.

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.

Chris turns to longevity doctor Peter Attia to find out how changing his eating habits can help his quest for longevity. Ironically, the answer is to eat no food at all for four long days. If he can bear the hunger, fasting will unlock his body's own anti-aging powers and give Chris the edge he needs when he tries to hunt for his next meal... by spearfishing off the Great Barrier Reef.

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.

Ever since his teenage years, stress has been part of Chris's life, and he wants to learn how to deal with it better. Psychologist Modupe Akinola challenges him to stay calm during a terrifying walk along a crane that's projecting out from the roof of a skyscraper. Modupe will train Chris in powerful physical and psychological techniques we can use to control the stress in our lives and combat the risk it poses to long-term health.