The sweatiest part of the human body

If I'm carrying a pack, yeah, it's the the middle or lower part of my back that gets and stays the sweatiest.

Without a pack, I believe the region is now called the "taint" =the perineum, the region of the human anatomy between the genitals and the anus as in "taint an asshole and taint a pussy." (from Urban Dictionary).

Wicking fabrics help you stay dry in both regions. Polypro, nylon, etc. On my back, that works really well. But on my taint, cotton consistently is less funky than synthetics. YMMV.

Above about 25 pounds, this is a big reason why I use a framed pack. I hike so much cooler, that it is worth the 2-pound extra weight compared to an internal-frame pack.

"But on my taint,"

????? ;0)

Dave, have you tried using wool underwear? My wool underwear keeps my private area very happy.

How about those Mountain Hardwear hiking kilts. I'd imagine they would breath quite nicely! ;)

I don't think it is an accident that guys in the hottest parts of the world traditionally wear things that look like dresses.

I wonder why we don't see more western women wearing hiking skirts or dresses? Hmmm.

Justin,

I suspect that Smartwool and some of the other vendors of Merlino wool garments would work well as undies – certainly more functional than cotton and not scratchy like old-fashioned wool. But I've got a mild wool allergy to the point where I don't wear wool socks around town, so they are more of an option on hiking days. Itchy feet are annoying but itchy privates, I suspect, are worse.

When I've got access to laundry options (that could be a business trip with a hotel sink, a road trip in a rental car, or a BPing trip in a dry climate), I'll go for wicking UW with two pair in rotation – I'm wearing one while the washed one is drying out.

As a desert hiker, suspended panels aren't going to make that much difference. I have external packs, a Dueter, and a REI Venturi. The last two involve other trade-offs. Get a pack that carries well and just live with a sweaty back. Hike a lot and you'll get used to and eventually not notice or think about it.

Regarding the taint… Wear Patagonia Baggies with the mesh liner cut out. 5" inch inseams.

For the science behind the shorts, research Fletcher's 3rd Law of Thermodynamics.