How did Bucky not age?

Bucky Barnes did not age due to a combination of factors, primarily his exposure to the Super Soldier Serum and his time in cryogenic stasis. Here’s a breakdown of how each of these contributed to his lack of aging:

1. The Super Soldier Serum

• Bucky Barnes, like Steve Rogers (Captain America), was injected with the Super Soldier Serum during World War II. The serum was designed to enhance physical abilities—strength, agility, stamina—while also slowing the aging process.
• The serum didn’t just make Bucky stronger; it gave him a form of near-perfect health, preventing his body from aging as quickly as a normal human’s. While Captain America’s aging was noticeably slowed due to the serum, the effects were even more pronounced for Bucky.
• After receiving the serum, Bucky’s physical age was effectively frozen. Even though decades passed, his body remained in the same physical state it was in during the 1940s.

2. Cryogenic Stasis (Frozen in Time)

• After Bucky fell from the train in Captain America: The First Avenger (2011) and was presumed dead, he was rescued by Hydra. They experimented on him, and during this period, he was placed in cryogenic stasis (a form of suspended animation).
• In this state, Bucky's body was effectively preserved, halting any aging. Cryogenic freezing kept him in a state of biological preservation while he was "asleep," being reprogrammed and turned into the Winter Soldier.
• Whenever Hydra needed him, they would wake him up and put him into action as their brainwashed assassin. After each mission, he was placed back into stasis, maintaining his physical appearance and preventing any aging.

3. Time in Cryostasis and the Winter Soldier Program

• Cryostasis combined with the Super Soldier Serum meant that Bucky didn’t experience the effects of time the same way others did. While he was in stasis for decades (after his fall in the 1940s), his body didn’t age during this period.
• He was effectively frozen in time—physically, he remained the same, even though decades passed. He had no opportunity to age in the traditional sense, as he was being revived and put back into stasis multiple times.

4. Bucky’s Preservation by Hydra

• Hydra’s involvement in Bucky’s life played a significant role in his lack of aging. They kept him alive and preserved through their experimentation, and it wasn’t until the events of Captain America: The Winter Soldier that Bucky is awakened from this long period of stasis and reintroduced to the world.

5. The Result: No Visible Aging

• By the time Bucky is reintroduced in Captain America: The Winter Soldier (2014), he hasn’t aged since his fall from the train during World War II. He still looks like a man in his 20s or 30s, despite the fact that over 70 years have passed.
• His lack of aging is explained by the combination of the Super Soldier Serum, which slowed down his aging, and the cryogenic stasis, which prevented any physical change while he was in suspended animation.

Conclusion:

Bucky did not age due to the Super Soldier Serum, which slowed his aging process, and the cryogenic stasis used by Hydra to preserve his body during his time as the Winter Soldier. These factors combined to keep him physically the same age for decades, despite the passage of time.