I think it's more complicated based on the article:

> "...It’s a very specific movement that right now requires wearable technology and experience to optimize the health benefits.”

So it sounds like the performer may have to look at a graph to see that the right motion has been achieved? This video reinforces the notion: https://www.youtube.com/watch?v=yaK6TThRMdE

I went looking at the published paper (https://www.sciencedirect.com/science/article/pii/S258900422...) and it says on pg3: "this specific type of plantarflexion because the relatively high soleus electromyography (EMG) on-time (i.e., soleus activation) coincided with upward angular motion of the ankle". The supplementary materials show EMG and range of motion graphs.

A bit of googling says plantar flexion is the same muscle movement needed for pushing the accelerator pedal while driving or ballet dancers standing on their toes.

My guess (not my field of expertise) is the muscle is activated strongly in isolation (the toe pushing down motion) and inducing a large range of motion. So it's not raising the heel so much as pushing the toe down.

From the article:

> In brief, while seated with feet flat on the floor and muscles relaxed, the heel rises while the front of the foot stays put. When the heel gets to the top of its range of motion, the foot is passively released to come back down.

See this video at t=34 secs: https://www.youtube.com/watch?v=yaK6TThRMdE&t=34s

Seems pretty simple... I guess what is special is (1) you can do it while sitting, and (2) the muscle doesn't seem to get tired so you can do it all day.