Shoe technology has advanced over the years to extraordinary heights, and up until now, there was a balance
between the advancement of shoes and runners still using their natural ability to perform. A runner purchases a
shoe that is going to support the foot and provide a certain level of cushioning, so that there is protection against the road,
and a fair amount of energy return to deal with running long distances on hard surfaces.
Now , the key word is energy return, which is supposed to be a science that returns the energy and force back to the runner. The force comes from the runner's body( effort and weight) and gravity acting on the body. It sounds fair and seems fair, and that is what running shoes have been doing and focusing on since forever. From the birth of EVA to the current Boost foam tech, the majority of shoes on the market have been fair in the practice of energy return.
However, things fall apart, meaning they change, and Nike has created a shoe that not only provides energy return, but provides extra energy that goes beyond the realm of fair play.
Lets say you hop on grass or on the street, and depending on the strength in your leg muscles, you're going to go so far up in the air. You're not going to reach an astronomical height, or leap like Bruce Banner when he is in his green skin. There is going to be a natural limit based on your natural ability.
Now, lets try that leaping thing again, but lets do it off a trampoline or mattress. Well, then, your leaping is going to be double that of your natural leaping ability. We see it all the time in gymnastics , and we see it with street tumbling teams.
It's called the spring effect, and that same effect lives in Nike's 4 % shoe, so runners who use the shoe are getting an artificial energy return that is no longer fair. There are posts all over the internet of runners PRing and dropping their times by 4-5 mins, which is unheard of, even for a runner who takes his/her training to intense levels to improve performance.
( Note: A trampoline provides energy return that is 160x greater than that of a running shoe)
Case in point, Amy Cragg. I'm a huge Cragg fan, because she is one hell of a runner. However, she is 34 years old, and before running the Tokyo Marathon, her pr was 2:27. So she was a 2:27 gal. But now she is a 2:21 gal, because she ran 2:21 in the Tokyo marathon. That is a 6 min improvement for a runner who is on the tail end of her prime. That is not normal or usual, and one would suspect that the runner was doped to the gills while running the race. But Amy is not a drug doper, and has never been suspected of drug doping, so where did the artificial help come from? The shoes, it came from the shoes. She wore the Nike 4%, and produced a time that no one expected her to produce. Basically, she did dope. She shoe doped.
If you wear those shoes during a race, you are shoe doping, too. Energy return is one thing, but to cheat the field and time is another.