The HS300 League should be physically impossible for the human body to endure.

As improvements in spacecraft design pushed pilots to accelerate farther and pull tighter turns, the question of a pilot's endurance was taken into account. There were three G-LOC related crashes in 2770 alone. This became a larger concern as time went on, and in 2773, RSEC engineers, in collaboration with multiple teams, decided to take a step back and decide how this could be dealt with, eventually leading to the implementation of four new technological breakthroughs which would significantly improve a pilot's endurance at high G-forces.

Adrilators
The Adrilator is a medical device connected directly onto the user's head. It is one of the main components of a headbrace following the SUO standard. When plugged into the spacecraft, it acts as a second heart, pumping blood to the brain when G-forces prevents the heart from doing it on its own. This aids greatly in preventing G-LOC and drastically reduces the chances of a stroke, working with the adrenaline to ensure the pilot stays conscious at all times. 

An Adrilator is inserted carefully by a doctor before the race, inserting IVs into the vertebral and carotid arteries. This sits firmly in place for the whole race, only removed by the same doctor.

Macnephrine
Macnephrine is a drug used to prevent internal damage and to maintain pilot alertness during sustained high-g maneuvers.

Macnephrine is a cocktail of blood thinners, blood vessel reinforcers, adrenaline, and focusers. The ratios are variable - different for every pilot based on their weight, height & other factors. In the wrong ratios, Macnephrine can have negative effects on pilots in the long term, leading to premature deaths. 

Macnephrine is injected into pilots before races, and is kept running through their system by IVs and pumps located behind their seat. Dialysis machines are used at the same time to clean the blood of drugs mid-race, as too much Macnephrine can be toxic to the human body.

Smart Suits
Smart Suits are specialized suits able to squeeze certain parts of the human body at the right times to encourage blood flow and breathing. It uses a self-tightening smart fabric called Myrlon which expands and contracts upon electrical impulses. These impulses come directly from the craft’s sensors, able to control Macnephrine flow, encourage hook maneuvers, direct blood flow, etc.

Adaptive Seating
Adaptive Seating works in a similar concept to Smart Suits. Seats with adaptive seating are padded with a thick silica-based gel, usually 60-120mm thick. This will cup around and help to brace the user as they sink into it under high acceleration. Furthermore, the gel is laid over active hydraulic plating, where plates move to slightly turn the user in their seat during tight turns, ensuring that the G-Force is mainly situated linearly.