Seat/Saddle. Be sure the seat, or saddle, is level. If you are sliding too far forward from a forward-tilting saddle then too much weight is being placed on your hands, arms, and low back. If the seat is tilted backwards then you may place undue strain on your lower back and possibly experience saddle-related pain. A physical therapist can measure proper saddle height by measuring knee angle at the most extended position of the knee in common pedaling.
The saddle should also be a comfortable distance from the handlebars. If it is too close then extra weight will be placed on the mid-back and arms; too far away and extra strain will be placed on the lower back and neck.
Handlebars. Handlebar position will affect hand, shoulder, neck, and back comfort. The higher the handlebars, the more weight will be placed on the saddle. Generally, taller riders should have lower handlebars in relation to the height of the saddle. Proper handlebar position allows for shoulders to make a 90 degree angle between the humerus, or arm bone, and trunk. Trunk angle for the road bike cyclist is 25-35 degrees and for comfort/recreational riding is 35-90 degrees. A physical therapist can assist in determining these measurements.
Knee to Pedal. The closer the angle is to 35 degrees, the better function the cyclist will have and with less stress on the knee. For the road cyclist, the angle should be 30-35 degrees. The recreational cyclist should have a 35-45 degree angle. Check out the link below for helpful diagrams.
Foot to Pedal. The ball of the foot should be positioned over the pedal spindle for the best leverage, comfort, and efficiency. A stiff-soled shoe is best for comfort and performance.
A physical therapist can be helpful in fitting your bike properly, and ensuring you have the necessary strength and flexibility to enjoy your ride!