[sometimeshuman]

Or buy one 30lb kettle bell. No running shoes, low cost, no finding space in your home, no buyer's remorse.

A swing with good form works your entire body. 100 reps once or twice a day literally takes 2-4 minutes. Do it after hitting start on the microwave.

[aqme28]

An exercise that takes 2-4 minutes is not the same as a HIIT exercise where you exhaust yourself in 30 seconds.

[encoderer]

Swing it faster.

[1letterunixname]

That's high-impact exercise a sizable fraction of people cannot do and has inherent risks of serious injury.

HIIT isn't necessarily high-impact.