Honestly, I'd consider such a thing to be minutia.
I might be inclined to take a hot shower, though.
If I wanted to, non-pharmacologically, prevent atrophy (apart from using training and diet), I'd probably employ the shower thing, and right after, follow it with STRONG EMS usage, and then end it with a rough massage.
Pharmacologically, I'd pick Clenbuterol.
I am fascinated by HSPs, and a pet interest is held in regards to HSP90. However, the means by which to activate them tend to cause great drain upon systems. If I am in a situation where atrophy is an issue, I would likely consider such drain undesirable.
Besides, like I asserted, I think it's minutia. I doubt it will save one pound of your muscle, relative to not doing the sauna jazz.
The EMS may or may not fall into a similar category, in terms of effect on maintaining hypertrophy (although I have personally had success with a particular protcol), but I KNOW it is, at the very least, quite effective at maintaining neural pathways and drive to muscles, and can serve as a substitute (on occasion) for "extra" workouts. Of course, many of you may not care about that aspect.