mclaug3

Your whole body sweats, I seriously doubt sweat from one part of the body travels all the way down there as it's most likely groin/butt sweat that is the issue. 

 

If you sweat that heavily, talc is probably the best bet.  There is also moisture wicking clothes that can help:

 

 

I find snug boxer/briefs help immensely. 

To each is own. I'm only speaking from personal experience. I do use spandex shorts often but even these have failed for me a good many times.

I've had this problem many times before and Im not a huge guy either. For the most part- the sweat that causes this is from when it runs down your back and into your ass and then down your thighs. When I know I am going to be walking around a lot and its going to be hot out I roll up a paper towel and stick it in the top my my ass crack and have it up so that it collects the sweat from my back and is held up by my underwear/boxers. Its a little uncomfortable at first but it is way better than chaffing.