What would be need to be modified to let a human handle more G forces?

Question

I watched a video or read some article recently on the reality of Attack on Titan's 3D maneuvering gear (very sorry, but I can't find it) and how it would kill the user easily.

Basically, even with the harnesses that the survey corps use to redistribute weight to the legs and torso, any movement that sent the user vertically (relative to their own body, not gravity) at high speeds would easily kill them due to the Gs, and the incredible centrifugal force of taking a turn at speed would likely snap the leg(s) of the user.

Assuming here that the bones and muscles were already strengthened to handle the crushing and pulling forces on the body, what modifications to the human body (genetic or cybernetic) would need to be made to let a human withstand other issues caused by high G forces and centrifugal force? For example, the increasing weight of the blood in your body as you accelerate.

Answer 1

It looks like most of the major issues once you've taken care of the basic strength and toughness (and you've mentioned muscles and bones, but don't forget tendons and ligaments and skin too!) are blood pressure ones.

• The heart would need to be stronger to be able to continue pumping blood against sustained high g-forces.
• A mechananism would be require to limit blood pooling in the extremities... a biological and internal equivalent of the G-suit. Thin layers of additional muscle around the major blood vessels in the limbs, perhaps additional valves to restrict periphal blood flow (if only briefly), reflexive muscle tensing to restrict blood flow, etc etc.
• More robust blood vessels all round but most especially the eyes and brain where small blood vessels rupturing can cause blindness, brain damage and death. This might have secondary benefits in the form of resistance or even immunity to things like haemorrhagic strokes.
• Greater resilience to transient blood pressure spikes in various organs and internal structures, because it would be sad to remain conscious and in-control throughout an awesome 25G slingshot manoevre to find that your kidneys have turned to mush and you spend the next few days peeing blood and dying unpleasantly.
• Much improve toleranced to shock loading of the body. You don't want the aforementioned 25G manoevre to result in a traumatic aortic rupture, for example (here's a fun real life example of aortic trauma caused by a roller coaster ride). Similarly, you'll be wanting your retinas to be more firmly attached. You might also want better padding and toughening inside the brain to reduce the risk and seriousbess of concussion (also a useful thing for any risky high-speed sports, or striking and throwing martial arts).
• Greater resistance to cerebral hypoxia, where restricting or even temporarily cutting off oxygen supply to bits of the brain doesn't present a serious risk of permanent brain damage. This requires some fairly complex biochemical changes and might in fact be the toughest thing to arrange. Obviously this too has some major benefits when breathing is difficult or impossible for reasons other than g-forces. These people would be harder to drown, strangle or suffocate.

What you might end up with is something like the effects of adrenaline, but with additional things like some kinds of precise physical control and complex thought become hard or maybe even impossible as blood supply is temporarily restricted to prevent damage during high-g activities.

The most difficult issue might just be the need for increased information processing and reaction speeds in the human brain and nervous system in order to operate the 3D manoeuvring gear, which would pose a formidable challenge even for someone with a body that wouldn't just fall apart like a badly made puppet at the first transition. Maintaining situational awareness during periods of restricted blood supply to the eyes is going to be a) very difficult and b) very important.

What you're ending up with is something that is potentially quite different from a vanilla human, both in how they're put together but also in how they think and react to the world around them... the foundation for something post-human rather than merely a bit superhuman.