One of the most common things that I see (and change) on a bike fit is saddle height. Most people have their saddle too high, which leads to problems. The widely accepted knee bend range is between 35 and 45 degrees, when measuring the angle of the knee bend in the ‘BDC’ position (your foot/pedal at the 6 o’clock position) on your pedal stroke.
Think of doing a bicep curl – your arm is much stronger in your ‘mid-range’ rather than when your arm is dead straight. The same is true of your legs when pedalling. If your leg is completely straight at the bottom of your pedal stroke (because your saddle is too high), you won't be as powerful through the stroke. The 'correct' saddle height will increase your power, cadence and reduce your aerodynamic drag. Win, win, win!