Many people ride an ill-fitted bicycle. That is to say, they ride a little hunched, too strained or short at the knees and pedals, or are not pedaling at the optimal revolution per minute (rpm) they should be because a little too much time is spent pulling up your legs from the updraft as the crank goes back up the cycle.
Short of getting a professional bike-fit, there are a few well-established methods you can use as a casual cyclist to adjust your saddle well. This video by Global Mountain Bike Network (GMBN) sets the bar on correct saddle height adjustment. Of course, not every method is tailored to suit you. Feel free to browse other methods that complement your needs.