What is stamina efficiency?

Some cards have powerful effect but are balanced with a malus "-20% stamina efficiency".
As there are effects as "+XX% stamina" and "+XX% stamina regen", I suppose effiency means any action that costs stamina will cost 20% more. But I could not find any confirmation, and it's a bit hard to test in game...

Does anyone knows what does it means exactly ?

Solution 1:

As healing efficiency increases the actual amount of health you recover, it's reasonable to think that stamina efficiency affects the stamina consumption, as you wrote.

Unfortunately, I've searched a lot and watched several video guides without finding any explanation about that.