We’ve seen them. Nike Air shoes.
Is there any advantage to running on air as opposed to regular foam?
Does compressed air provide superior cushioning vs. foam?
I’ve run on both and never noticed a difference. The air soles should last somewhat longer as air doesn’t wear out and harden like foam but it can be punctured.
I was always rather sceptical about whether the “air unit” in the sole actually did anything other than look cool. I remember having a pair of Nike Air trainers as a teenager, and at some point (possibly deliberately) the air bubble in one got punctured. I don’t remember it making any difference to the comfort, because the air bubble is enclosed in a fairly supportive sole unit anyway.
Foam is a bunch of air bubbles. The Air unit is just one big bubble.
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Closed-cell foam is a bunch of air bubbles.
Open-cell foam (e.g. the sponge at your kitchen sink) is not a bunch of air bubbles; elasticity is due solely to the properties of the material comprising the foam, and not due to the compressibility of air.