Cyber Cyclist , an online magazine, features cycling news and events, product reviews, and bike tests. Cybercycle provides detailed information on equipment, repairs, trails, mountain biking, nutrition, and much more. Frame size, seat height, and reach each have an effect on basic body position and comfort on the mountain bike. Your bike should not be too big. The optimal saddle height depends on whether you are pedaling normally or descending a steep hill.
Some riders lower their seat a few inches on tough descents for safety and stability.
Because most mountain bikes are equipped with quick-release seat posts, you can quickly slide your saddle up or down as the terrain dictates. Sit on the seat. Loosen the seat post and slide it up until your leg is outstretched with your heel on the pedal. Make sure that your leg is slightly bent when the ball of your foot is centered on the pedal. Proper reach will put you in a comfortable, powerful position, neither too outstretched nor too upright, with arms slightly bent, not locked.