This is a very common question and it’s not a fun one to answer. The truth is genetics do play a significant role in the vertical jump and athletic ability in general. Look at 12-year old kids. Some are athletic. Some are not. Obviously their varying genetic gifts make a difference. This is a painful realization, because those who are naturally gifted have to admit they did not have to work as much as other people for their abilities, and those who are not gifted have to accept that they can never be the best leaper or sprinter in the world.

There are a number of physical traits that contribute to athletic ability and are influenced by genetics. I’ll discuss them in no particular order.

1. Body type. A long, thin body with long limbs is great for jumping and running. Because the tallest people are often not the most athletic, people tend to be unaware of this advantage. When a longer body segment is rotated with the same speed as a shorter segment, the end of that segment covers more distance, meaning that more velocity is generated. In a jump or a sprint, this means that more height is achieved or more ground is covered. As for a thin body, that’s just a matter of weight. The less weight on your body per inch of height, the better off you are, at least from a physics standpoint. Obviously, you need muscle mass to be able to generate powerful movements, so you don’t want to be as thin as a rail. Unfortunately, your body’s build is not something you can do anything about. You can be muscular and lean, but you may still be short and stocky.

2. Strength. Some people are just naturally strong, and they also get stronger easily. This is the reason why tall people are not usually the most athletic. Their strength relative to their body weight is usually much lower, and they have a much harder time making improvements in this area, which more than compensates for the advantage of height. When you combine height with some decent strength levels, you get athletes like LeBron James and Usain Bolt. Strength is a very trainable ability. A well-trained person can definitely get as strong as an untrained person who is naturally strong. But the gifted person has far more potential if he or she does strength train.

3. Explosiveness. I define explosiveness as the speed at which muscle tension can be generated. This is determined by the nervous system and the fiber type makeup of muscle fibers. Some people are born with great explosiveness. Others are not. Again, this is a trainable quality, and a non-gifted athlete can still develop a high level of explosiveness by improving the nervous system and shifting muscle fibers toward the fast-twitch end of the spectrum. However, once again the gifted person has more potential with training. This is why almost all elite sprinters have west African genetics. The explosiveness needed for elite sprinting is not something that can be developed without tremendous natural talent.

4. Reflexive contributions. We can all recognize the naturally springy people. They seem to effortlessly glide when they move, just playfully bounding around the court or the field and then suddenly bouncing high up into the air as if gravity wasn’t even a factor. This is a highly coveted and elusive trait, which comes largely from a dramatic myotatic stretch reflex. Unfortunately the reflexive response is only mildly trainable, so those not gifted with it cannot train themselves to become like the gifted in this department.

To sum it up, yes, athletic ability is significantly influenced by genetics. The ceiling is higher for the naturally gifted, and not everyone can be a world class athlete. However, everyone is capable of being flexible and coordinated and developing strength and explosiveness over time. That means everyone can make improvements in the athletic pursuit of their choice. And the potential for most athletes is higher than what many think. I believe that the typical high school athlete in America can approach jump at least half of his or her height with proper training.