Warning: contains spoilers for Captain America #0!
Marvel's new Captain America, Sam Wilson, famously has no powers of his own, but that doesn't stop him from charging into battle exactly like Steve Rogers, and the company finally revealed exactly what keeps Wilson going as of Captain America #0. This eye-opening issue is packed with plenty of action as both Rogers and Wilson team up to stop an old threat from terrorizing New York City and inflicting horrendous harm on the populace. Aside from the former Falcon foiling a fiendish and fearsome foe, the issue reveals Sam's unique backstory is the key to his survival.
Sam Wilson cannot fly on his own, but is outfitted with a pair of wings that resemble those of his old suit during his days as the Falcon. While he technically does have a very limited ability to telepathically communicate with birds on Earth, this power is rarely used in the modern era (and the powers is completely absent in the Marvel Cinematic Universe). Still, Wilson is not nearly as strong or as fast as Rogers in both the comics and the films - so how does the new Captain America manage to survive his many battles?
In Captain America #0, Armin Zola has developed a rocket (hidden inside a skyscraper, no less) that will launch into the atmosphere and detonate above the Earth, causing humans to mutant into "Zolasauruses" of his own design. Steve Rogers and Sam Wilson team up to stop Zola and eventually board the rocket as it launches. The craft accelerates to over three gs of force, and while Steve Rogers is still standing thanks to the Super-Soldier Serum in his veins, Wilson is on his feet because "...the only reason I'm standing is the flight hours I've logged."
In his history, Wilson's flight harness was a gift from T'Challa the Black Panther, and he continued to use it for many years. In the 70s and 80s, he became Captain America's trusted partner, often acting as the eye in the sky on mission that required reconnaissance (and eventually combat in the air). Wilson has spent most missions in the air, climbing, diving, and surviving multiple high-g maneuvers while wearing nothing but a pair of wings. Wilson must have considerable control over his body (and especially tremendous strength in his core) to be able to stand up on an accelerating rocket.
This ability is not the result of chemical concoction but rather decades of experience as a crimefighter. Contrary to what those in the other branches of the American military may believe, a fighter pilot in the Air Force must be physically strong to endure numerous flights, and Sam Wilson is no exception (and he doesn't even have a plane to protect him). The new Captain America isn't necessarily super, but that doesn't mean Sam Wilson isn't a hero.