Why do people wear forearm bands? Does it make your arm not hurt after a round? Is to avoid injury? Or because someone is recovering from an injury? Are they just really sweaty and they want to keep their hand drier?
Tennis Elbow (lateral epicondylitis) is a form of tendonitis that occurs due to overuse of the elbow.
Although tennis is a leading cause of tennis elbow, there are many other causes that include playing sports (like squash, handball, bowling and disc golfing), painting, performing manual labor or playing musical instruments.
If you are talking about the sweat band around the wrist or the band around the area about 2 inches below the elbow.
The sweat bands around the wrist is for the coolness, like a NBA player. Or someone who is injured and wearing the band to relieve Epicondylitis.
My personal experience is that Tennis Elbow braces work great. Back in my younger, more energetic days I played recquetball. It seemed that most tournament racquetball players at some point developed Tennis Elbow. There was a basic therapy routine we did that eventually fixed the condition. That routine included using a Tennis Elbow brace. The brace didn't fix the problem but it prevented the condition from getting worse while the rest of the therapy did its job.
A few months ago I tweaked my elbow lifting weights. It was getting worse until I started using a brace while lifting weights. I have continued to wear one for preventative purposes (just while lifting weights). The elbow hasn't been bad enough to bother my disc golf throws but I know that Tennis Elbow sometimes continues to get worse if you don't treat it properly.
Braces are great. They are cheap ($10). They allow you to continue playing or working out-far better than taking weeks or months off. And they prevent the problem from getting worse. I don't have any idea how they work on gangrene.