Assuming no topical creams or moisturizers are involved, can human skin be tough one day and pliant the next?
Yes, if you are talking about so-called ‘skin turgor’.
To see what skin turgor is referring to, simply pinch up a wad of skin from your forearm (say, 1/2 way between the hand and elbow). When you let it go, it probably springs back so fast that you can’t even see it in ‘transit’. On the other hand, if you were profoundly dehydrated (so your skin would also be dehydrated), the lifted wad of skin would tend to come down very slowly upon letting it go, or maybe even stay up where you lifted/stretched to.
In children and young people, this is a reliable way of checking for dehydration. In older individuals, the skin tends to stay tented up after you let it go even if they’re not dehydrated. This is said to reflect “loss of elasticity” of the skin as a result of aging. This also reminds us that hydration status is only one of a number of factors influencing skin elasticity.
Here is an excellent image of decreased skin turgor (in a patient profoundly dehydrated because of a diarrhea-inducing tumor). Apparently, the editors of the Journal think the sign is still useful even in older people.
Yeah, I sometimes get that after a long bike ride. Pinch the skin of my hand and it stays pinched. A good indication that I need food and water, lots of it.