Their strength? Well, i could assume he'll be aware of that feat, seeing as Tsuande is a former teammate of his sensei.
If that's not reason enough, from what we've observed from Kimimmaro's previous fights, he's not one to allow anyone to land a blow on him, as Lee wasn't able to. In the process, surely he'll notice neither the chakra focused in their fist or knowing Tsunade/Sakura's history either would punch the ground at some point.
Regeneration? That'll only be observed once a wound in inflicted. He has superior speed, reflexes, unpredictable abilities (kkg), etc. It's likely either would be wounded, whether it's a life threatening or not.