eli5, why is it harder to do jumping jacks on a concrete floor than on a shock absorbent floor in the gym


Is it a similar concept to running on a treadmill is easier than running outside? I understand that weather and inclination do play a role, but other than these external factors, what’s the role of energy?

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Squishy floors and dirt are not completely solid, they have small air pockets that get compressed when stepped on. This energy is then pushed back making it slightly easier. Think about a trampoline. There are shoes that do this too such as the Nike vaporfly which the majority of world record runners have [used](https://www.wired.co.uk/article/nike-alphafly-eliud-kipchoge)