Different heights can mean some of us are naturally designed to be better and more efficient in certain exercises. Generally speaking, taller people have more trouble with exercises where you have to lift your legs straight up in the air. Taller people usually have a longer leg-to-rest-of-body ratio than shorter people. These moves are more challenging for taller people because they are likely to have more leg to keep in the air in relationship to the rest of their body. This in turn will put more of a strain on their muscles."
Taller people also may have more difficulty doing squats. One of the reasons for this is thought to be because their legs are probably longer, they have further down to go before they hit the ideal squat position. When the weight is traveling a further distance down, it becomes harder due to the greater distance.
What about the shorter people? Their issue is more about vertical jumps. Any exercises involving big vertical jumps—like box jumps—are usually harder for them. Ultimately, these people end up doing more work than tall people on vertical jumps as they have to exert more force to travel the same distance.
And finally, most fitness machines with adjustable moving parts—i.e., the ones where you get to choose your weight resistance—are harder for people on extreme ends of the height scale (above six feet or below five feet). This is because these machines are generally made for the average Joe, which is around 5'5”So if you are either really tall or really short, some of the moving parts may not be adjustable for your correct height. If you are a super-tall or super-short exerciser, stick with the machines that don't have adjustable parts—like the treadmill or an elliptical without arm handles (since those are created for a standard-sized person, too).