hig4s

On the average person the knuckles and the hand's grip are at approximately 15* off from the angle of the wrist bone. On a bar with 6* or less of sweep you have to turn your wrist in to accommodate the angle. With your wrist turned in, the angle of the pressure from the forearm naturally pushes more to the outside of the hand, this is so the force transmitted to you from the bar goes more down the middle of the arm not just to the thumb. If you shift your weight off the outside of the hand it puts unnatural pressure on the thumb joint.

When I ride my bike, or when I tested a number of bikes this year, I put my weight on the outside of my hands and the wider I went the more uncomfortable it became, but when I tested a Salsa with 11* sweep, it was more comfortable and I felt less pressure on my wrists. More like the sweep on motocross bikes.