Article: Your posture while cycling is also crucial if you want to avoid back pain. Try to keep your back straight while cycling — not completely erect like sitting in a chair — but rather flat, stable and well supported by squared shoulders. Distribute some of your weight to your arms and hands while keeping your chest and head up. Shift positions and change the angle of your upper body periodically in order to prevent muscle fatigue.  Gently lifting and lowering your head from time to time is helpful for keeping your neck loose and avoiding muscle strains. Approximately 45% of overuse injuries to professional road cyclists involve the low back. When riding your bike, keep your arms slightly bent (10 degrees) while gripping the handlebars. This posture will allow the joints and muscles of your upper body to absorb some of the vibrations and impact instead of your spine, particularly if you tend to ride on rough terrain such as forest or mountain paths.  Grip the handlebar with your whole hand, but not too tightly. Wear padded cycling gloves to help with shock absorption. If your back tends to act up while cycling, break your ride into segments and take more rest stops. When peddling, it's more efficient and best for your hips and low back to have your knee bend at a 90 degree angle at the top of the peddle stroke (when it's farthest from the ground). At 90 degrees, your thigh should be roughly parallel to the saddle, which then allows for a strong push down on the pedal. At the bottom of the stroke (when the peddle is closest to the ground), your knee should be flexed at about 15-20 degrees, which is unlikely to strain the low back muscles, tendons and/or ligaments.  If your legs do not match these angles while you pedal, then adjust the height of your saddle. The front 1/3 of your foot should be in contact with the pedals while peddling.
What is a summary of what this article is about?
Avoid slouching or hunching your shoulders while riding. Keep your arms slightly bent while riding. Keep your leg at a 90 degree angle at the top of the stroke.