Sports Training Science

by Daniel Back

The best way to increase your vertical leap seems to have become a sort of mystery these days; athletes wonder why the guy with really skinny legs can jump high, as well as the really muscular one with thick legs; they wonder why jumping off one leg is so much easier for some and more difficult for others; they wonder why so many workouts can yield so little results. Unknowing athletes are vulnerable to poor information supplied by the ease of publication on the internet. One kid had using a stair climber as part of his jump training; another wanted to know how long it would be before he could dunk if he jumped rope every day; a 5'7" 13 year old girl wanted to dunk before high school; the list of the poorly informed goes on and on. This mystery status of vertical jump training has led to a tendency to seek out new, revolutionary exercises and products; a mystery has to have a crazy answer, right? Thus, we see bizarre products like calf isolators, jumpsoles, and vertimax, and there are plenty of programs offering "revolutionary training" from "vertical jump experts." There is also a gravitation towards less familiar, less traditional exercises. Many athletes learn about plyometrics and think that this different type of training which is specific to jumping must be the answer. It makes so much sense when a person first hears about fast and slow muscle contraction to only train with plyometric drills. Or there is the opposite opinion that squats and power lifts are the only thing needed for an exceptional vertical. Supporters of this opinion base it on the fact that world class olympic lifters often have verticals of 36 inches or more. My goal is to eliminate the confusion with simple, factual information.The truth is that every athlete is different and will need to do training that fits his or her individual abilities. Many people are looking for one magical workout or even one exercise that will make them a superstar. That's not the way it works; things are a little more complicated than that. However, if you understand some things about the human body, it can be easy to create an intelligent and effective training plan. I began sharing what I've learned with whoever I can, because I am yet to find a complete, accurate source of information available for all. Everyone wants money for their "secret breakthrough formula." Quality jump training is not a secret or a mystery, and I do not believe an athlete should have to pay $40 for a list of exercises and a chart of numbers. I hope to equip you with knowledge that will help you train intelligently for the rest of your life. Yes, I do have vertical jump training programs and exercise videos available, but I also want you to understand the science behind the training.

The height a projectile flies is determined by the velocity of the center of mass as it leaves the ground. The faster the initial upward velocity, the longer it will take for gravity to decelerate the projectile, and the higher it will travel. In the case of a human jumping, the projectile is the body, and the initial velocity is determined by the acceleration of the center of mass due to the force generated by the body. If you want to increase your vertical leap, the goal is to increase the force that your body can generate. Simple enough right? Just lift weights, and your muscles will grow; your legs will be stronger, and you'll jump higher. This is true to an extent, but you will likely discover at some point that jump training is not quite that easy.The truth is that there are three different muscle, tendon, and nerve abilities that contribute to jumping, or most athletic movements for that matter. The first ability is maximum strength; this is the largest amount of force that a muscle can exert. This is the most familiar muscle quality and the most commonly trained. It is increased by common resistance training, which most people are familiar with. The back squat is an example of a resistance training exercise used in jump training. The second ability is rate of force development, more simply stated as explosiveness. Muscles cannot instantly exert their maximum force; it takes a little bit of time to activate all the muscle fibers. That time is small, but it is still longer than the time it takes to jump, meaning that all the force a muscle can exert cannot be utilized in a jump. This is the reason for the gap between strength and jumping ability.Consider this scenario... Let's say Timmy weighs 150 pounds and can exert a maximum of 500 pounds of force on his center of mass (COM) in the range of the jumping motion. As Timmy begins the jumping motion, his body is not generating that 500 pounds of force yet. 2/100 of a second after his muscles began to develop force, he is putting out 150 pounds, and his COM begins to accelerate upwards. At 1/10 of a second, his legs are putting out 215 pounds of force, and his COM is accelerating faster. By 2/10 of a second, the force on his COM has grown to 350 pounds, but unfortunately his legs and back are fully extended; he's done jumping. Timmy never got to use all his force. These force numbers are purely hypothetical, but 2/10 of a second is a common duration of the jumping motion. The maximum force an athlete's muscles can exert cannot be generated in that time. The goal for athletes is to train to increase the percentage of their maximum force that can be generated quickly enough for use in jumping and all athletic maneuvers. This ability is improved by exercises that require fast muscle contraction; Olympic lifts (clean, snatch, jerk) and plyometric drills are the most common. Note though, that exercises that use fast movement do very little to increase the maximum strength of the muscle. Rather it is the ability of the nervous system to quickly stimulate muscle fibers that is the focus of this training.The third ability that contributes to jumping is elastic strength. This is the ability of muscles and tendons to store energy in a stretch and utilize it in the following contraction. This process, called the stretch-shortening cycle (SSC), is what causes a higher jump from an approach than from a standstill. (Quick note: Lengthening muscle contraction is called eccentric, shortening is concentric, static is isometric. The SSC uses all three in quick succession) The human body naturally uses a countermovement before powerful motions in order to take advantage of this elastic strength. When you squat down to jump or pull your arm back to throw, you are using elastic strength to add force to the motion. The trick is that the desired motion must immediately follow the stretch to prevent the energy from dissipating. To demonstrate this, perform a natural jump from a standstill and take note of how high you get. Then do a jump but pause for a second in the crouched position before exploding upward. The second jump should not be as high, because the energy from the drop into the crouched position dissipates during the pause. The term for the muscle contraction involving a stretch followed by fast shortening is plyometric. Exercises that use this type of contraction have been labeled "plyometrics." This type of training is what increases elastic strength.Vertical jump training needs to be tailored to the individual strengths and weaknesses of an athlete in the areas that have been mentioned. Therefore, it is incorrect to offer a single program and guarantee a certain result to anybody who tries it. A basketball player who cannot squat his own bodyweight will hardly benefit from a plyometric program, and a bodybuilder who squats twice his bodyweight will experience little gain from adding 20 pounds to his max squat. An effective training plan must take into consideration all the facets of vertical jumping. That is why on my site, I provide methods for evaluating yourself, so you know which areas you most need to work on. This is far superior to just giving you common exercises and assuming they will be effective.



Strength training has been dismissed by many when it comes to increasing jumping ability. Many people say that squats will only slow you down, weigh you down, and decrease your flexibility. This is simply wrong. How does one explain that Olympic sprinters can squat at least twice their own body weight? What most people do not realize is that there are different goals one can shoot for using different principles within strength training. There are lifters who can squat a ton but are not very good athletes, but this is because they do not train for athleticism. For athletes, especially those who wish to jump higher, the goal needs to be to get stronger and more explosive. The key to effective lifting is to apply that philosophy on every rep. This means applying as much force as possible from the beginning of your muscle contraction to the end, even if it is not at all necessary to move the weight. This will result in faster, more explosive movement. On every rep you complete in a workout, you should focus on being explosive. Try to throw the weight through the ceiling. Slow movement in lifting is for bodybuilders. They train for size and definition. The strength that bodybuilders gain is far less employable in sports. Take a look at the World's Strongest Man competitions. The guys who compete in those may be big, but they're nowhere near as big or chiseled as some of the professional bodybuilders. They train for practical strength, because they are athletes, not just masses of muscle. In my training programs, you will do some reps that are slow, but they will be slow because you literally cannot move the weight any quicker. You should never choose to move slowly.The smart first step in vertical training is to develop a base of strength. Squats and deadlift are the most fundamental lower body lifts. Strength training itself can yield wonderful results and will also maximize the effectiveness and safety of explosive and plyometric training.

Plyometrics are easily the most prescribed form of training for increasing jumping ability. They utilize the stored energy in an elastic stretch to add force to joint movement. This promotes increases in speed of force development and elasticity of the muscle-tendon complex, both of which are crucial to jumping. Therefore, plyometrics are excellent for increasing jumping ability. So why is it that many athletes see little to no gains from performing this type of training? The answer is that both speed of force development and elastic strength are limited by maximum strength. Think about this... Let's say Timmy's muscles can utilize 70% of their maximum force in a jump. Timmy does a successful plyometric program and increases that number to 75%. If he can only squat 100 pounds, will he see much improvement in his jump? No; he is utilizing a larger portion of his max strength, but his max strength is too small for that additional portion to mean much. Now consider elasticity. Think about a rubber band. Is a stronger rubber band made of more highly elastic material, or is it just thicker? It's thicker. In the same way, muscles and tendons cannot just keep growing more and more elastic. But if they get stronger, (just like a rubber band gets thicker) and the level of elasticity is maintained, their elastic strength will increase.Therefore, developing maximum strength should be the first step in jump training. Almost all vertical programs available today focus on plyometrics; many completely eliminate strength training. A person who severely lacks speed of force development and elastic strength may see some results from this type of program, but you cannot reach your full potential without gaining strength. Also, it is far more common for young athletes to lack strength than lack plyometric ability. The muscle action used in sports and games during sprinting, cutting, and jumping is plyometric. Young athletes are constantly training elastic strength. On the other hand, how many middle school kids are in the weight room doing squats? A typical young athlete will see limited results from plyometric training, because there is very little strength reserve to draw from. The best approach to increasing vertical leap ability for a young athlete is to first develop maximum strength while continuing to engage in athletics to promote the transfer of strength to athletic performance. As a 13 year old, I added 12 inches to my vertical in about 7 months using only strength training. It's possible that I could have also made gains using only plyometrics, but then I would have had no strength to use when I did more training in high school. Instead, I did have strength, and I increased my vertical another 8 inches when I was 15, with very little of the knowledge I have now.Exercises of all levels of intensity have been thrown into the plyometric category with little explanation of their differences. There are lighter intensity exercises like ankle bounces and line hops. These are drills that most athletes can do effectively without risk of injury. Drills like jump squats and bounding are of medium intensity. The two original plyometric drills, depth jumps and depth drops, are of the highest intensity. These exercises and their variations utilize the stretch reflex. Built into human muscles are devices called muscle spindles that detect the rate of change in length of a muscle. The stretch reflex occurs when the muscle spindle triggers a contraction of the associated muscle in order to return it to a given length. This is an involuntary neurological function demonstrated by the familiar doctor's office procedure of tapping the knee to invoke a kick. The tap on the patellar tendon stretches the quadriceps muscle fast enough to activate a contraction. The faster that muscle length is changed, the greater a contraction the stretch reflex will cause. High intensity plyometric drills involve rapid lengthening of muscles that provoke strong reflexive contractions. When this involuntary neurological action is combined with voluntary muscle contraction, the force output is extremely high. Also, tendons contain a built-in device called a golgi tendon organ, which senses tension and sends an inhibitory signal to the associated muscle and triggers a contraction in the antagonist muscle, reducing the net force in the direction of joint movement. This helps precise motor control and also protects the joint. High intensity plyometrics lower the sensitivity of the GTO to allow a larger net force in one direction. It is common opinion that an athlete should be able to squat 1.5 times bodyweight before performing these high intensity exercises; muscles and tendons need to be well developed to support the extra force exertion. The key to a successful program is determining what combination of strength training and plyometric training will be the most effective. Again, this will vary between athletes, so it is necessary to evaluate strengths and weaknesses before creating a training program. Many products fall short in customization.

Flexibility is a crucial factor in developing athletic ability, because it allows joints to be placed in the proper positions for athletic movements and training movements. Tight muscles limit the amount of force that can be developed at a joint. First, there is obvious structural interference. If a muscle is lengthened during a movement, it will slow that movement down if it's tight. Second, there is neurological interference. Recall the golgi tendon organ mentioned earlier; it prevents high tension in the muscle-tendon complex that could cause injury. Muscles and tendons that are inflexible are more susceptible to injury, so the sensitivity of the GTO is higher. Increased flexibility leads to less interference in force development by the GTO.An example. A sprinter who does not have good range of motion (ROM) in the hips cannot flex and extend the hip far and fast enough to maximize stride length. That same sprinter is likely to not be able to do a full squat with proper form, again because mobility of the hips is lacking.Bottom line, inflexibility limits ROM and limits speed of motion. If your body segments can't move quickly, you cannot be athletic. It's that simple. Now think, is high speed movement allowed at the edges of a joint's ROM? No. At the end of the ROM, muscles are uncomfortable and weak. Therefore, the flexibility at a joint needs to exceed the ROM required for athletic movements, so that the joints can move quickly with no resistance.In addition to improving athletic movements flexibility is also crucial in injury prevention. First, tighter muscles and tendons receive more stress and are more likely to become inflamed, stretch in a bad way, or tear. Two, poor joint mobility leads to improper movement. Improper movement leads to higher stress on body structures. Higher stress leads to injury.
Flexibility is absolutely critical to becoming a great athlete. Developing it should be first priority, along with developing strength.

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What is the contribution of abdominal strength to jumping? Some would say there is none, and they would be wrong. Since the jumping motion does not include flexion of the torso, your abdominal muscles do not actually contribute force to your jump. What they are important for is creating stability.Stability is a very important factor in jumping. You must have stability in your legs and torso for the purpose of transferring force. This is a hard concept to explain, because you can't really picture force transfer, but I'll do my best. When you jump, the force that sends your body upwards comes from the floor. This may sound incorrect. Your body generates force that pushes down on the floor. According to Newton's 3rd law, the floor will push back with the exact same amount of force. Imagine if you ran up to jump, but the place where you planted your feet was a trap door. You would push down, but you would not go up because the trap door would collapse instead of pushing back like the floor would.Now, knowing that the force that propels your body comes from the ground, it makes sense that the force has to be transferred through your legs to your center of mass, which is in your torso. For this to be done effectively, you have to joint and core stability. If your ankles, knees, or hips are wobbly, energy will be lost. This is why an ankle or knee sprain can continue to limit your athleticism even after the pain is gone, and your muscles are back to full strength. Some other examples... try to do a pushup with your hands planted on an exercise ball. The ball creates instability, your arms will wobble, and energy is lost making the pushup quite difficult. Or imagine trying to jump on ice. The ice creates instability, so your jumping ability is limited. If your core is unstable, you will not be able to apply force to it to propel it into the air. Imagine trying to throw a big cube of jello up into the air. You couldn't get it very high, because the jello is unstable. Put that same cube of jello in a pan, and you will be able to throw it much higher despite the extra weight, because the pan makes it stable, allowing you to apply force to it. In the same way, your core must be solid for you to apply to it the high amount of force required to send it high into the air. Try feeling your abs while you jump; they naturally flex quite hard to make your torso rigid.Most athletes will have enough core stability that it won't limit them in a movement like a standing jump. But in sports, you are going to want to be able to maintain that core stability in all kinds of positions, moving in all directions, and with contact from other players. Therefore, it is wise to continue increasing core strength throughout your entire athletic career.

You may have heard about fast and slow twitch muscle fiber. You may have read that only fast twitch fibers are used in jumping and sprinting; you may have read that getting faster or jumping higher is not very possible unless you are one of the people blessed with a high percentage of fast twitch fibers. Do these people have an advantage? Yes. Is that the primary factor affecting athleticism? Absolutely not. Those who are not as gifted genetically surely should not throw in the towel on jump training or becoming a great athlete in general.There is an entire spectrum of muscle fiber twitch speed. People have come up with three classifications (type I slow twitch, type IIB fast twitch, and type IIA, which are fast but not as fast as type IIB) but in fact there is a broad continuum of many more than three types. But the point is that there are faster and slower twitch fibers. The common misconception is that type II fibers are the only ones that are used for explosive movements like jumping. What needs to be understood is that, although type I fibers are not as fast as type II, they still reach full contraction force in less time than it takes to jump and, thus, are fully utilized. The much larger factor in explosiveness is the speed at which groups of fibers called motor units are stimulated by the nervous system. The activation of the motor units is the process that takes longer than the jumping motion and limits the amount of force put into explosive movements. Therefore, it is far more important to train the nervous system to excite more motor units faster than to have those motor units be made of fast twitch fibers. Training explosively is what increases this ability of the nervous system. In addition, although muscle fibers to not completely transform from one end of the speed spectrum to the other, your body does slightly alter the behavior of muscle fibers based on demands. If an athlete trains using slow movements, his or her fast twitch fibers will act more like slow twitch. Likewise, using maximum speed movements causes slow twitch fibers to act faster.Therefore, please do not feel like you have no chance of becoming a great athlete because you are not as genetically gifted as some may be. Take it from me; genetically, I'm fairly average, but I am certainly an above average athlete. Effort and intelligence will get you far in sports training and in life.I believe I have given you enough information to help you make effective training plans on your own. However, I realize that many readers are looking for actual jump workouts, and also many athletes need instruction in the correct execution of exercises. That is why I spent years developing a jump training program.

Daniel Back is an aspiring athlete and vertical jump and strength specialist for Complete Game Athletics. He has achieved a 43-inch vertical leap himself and has had great success training others. For more info check out his sports training articles, instructional exercise videos, and vertical jump programs at

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