Examining Vertical Jump Mechanics - Part 1
The most important science to increase your vertical
By: Neal Wen
Increasing vertical jump height is one of the most coveted abilities by athletes in basketball, volleyball, netball and the likes. Almost every week I receive requests from athletes seeking my assistance to improve their vertical. Understanding the importance of a big jump in sports, it led me to spend over 10 years to extensively research scientific principles underpinning jumping abilities. Along the way I am proud to say the principles I present here have allowed me to consistently improve the jumping performances of my athletes - from juniors all the way across to professional athletes - and we are jumping higher and higher! Don't believe me? Here are the results of some of the athletes I have helped over the past decade.
To understand the mechanisms of a big vertical we must first break down some of the key factors involved in an explosive jump. There are two interrelated components that dictate the outcome of a jump and that is Force and Velocity - which are the main parameters governing power output. Hence this is why vertical jump assessments are often viewed as an expression of total body power capabilities.
The Force end of the spectrum is dictated by: (i) an athlete's ability to recruit a high amount of high threshold motor unit, (ii) neural drive, and (iii) muscle-tendon unit. While you can definitely increase your recruitment of high threshold motor units through strength training, however how much high threshold motor units you have at your disposal is very much genetically predetermined. An additional consideration regarding motor unit recruitment and force generation athletes and coaches also need to take into account of assessing their strength capabilities relative to their body weight; to be able to jump high you must not only be able to generate a large amount of force but it must also be forces you can use functionally. For instance, data from my 40" jumpers have demonstrated that they are able to generate up to 3 times their body weight amount of force output in one single jump!
Another factor influencing force generation is neural drive, while there is still a genetic influence on the intensity of the neurons an individual can fire however an athlete will be able to more readily enhance this capability through sound strength and power training modalities that aims to maximally fire your motor units. The last factor is the muscle-tendon unit, this has to do with an individual's unique muscle-tendon architecture that is also very much genetically-driven. For instance, explosive athletes are known to have long Achilles tendons that allows them to store a large amount of elastic energy to augment power production. Whilst you can't influence your muscle-tendon makeup however with some plyometrics-type training you can maximize your muscle-tendon functions.
On the velocity end of the spectrum the primary determinants are: (i) contractions velocity, (ii) neural drive, and (iii) coordination. An athlete's speed of contraction is ultimately limited by their genetics, however it can be maximized through Explosive Power-type of training and modalities like Shock methods that involves depth jump variations. Neural drive also influences the velocity of your jump, and because of this reason as an athlete you should almost always lift weights with the intent to push the weight (heavy or light) as fast as possible, as your intent will be the primary driver for maximizing neural drive. The last factor influencing velocity is coordination, coordination involves an athlete's jumping technique.This has been the least explored part of contemporary jump training methods and is arguably the most important one. For this reason this article will mainly focus on the biomechanics of sound vertical jump techniques.
Once you commands a firm grasp of these scientific principles and use it to guide your training, as long as an athlete stays consistent and disciplined with their training I believe most male and female athletes can attain a minimum of 30" and 24" vertical jump respectively.
STANDING VERTICAL JUMP: THE FOUNDATIONS OF ALL JUMPS
To understand all the different types of vertical jump variations (i.e. 1-step jump, running jump etc.) and their mechanics we need to start by examining the mechanics of the Standing Vertical Jump. The Standing Vertical is the foundations to all jumps, it shares mechanical commonalities with all the different types of jumping variations. It is classically demonstrated in the video below.
There are 5 phases of the Standing Vertical Jump and they are defined based on their corresponding muscular mechanisms. The muscular actions involved is called the Stretch-Shortening Cycle (SSC). As described in figure blow, the SSC is a mechanism that allows an athlete to store elastic energy in the muscles and tendons during an eccentric loading phase (Sequence 1 and 2), it is followed by a brief transitory period called the amortization phase (Sequence 2) where an athlete reverses the direction they are travelling (from descending to ascending) and subsequently releases the stored energy during the concentric drive phase (Sequence 2 and 3) that launches the body into the air.
Founded on the sequences of SSC mechanisms research regarding vertical jump mechanics have identified 5 key phases in jumping:
Eccentric (load) phase
Amortization (transitory) phase
Concentric (drive) phase*
Flight (time in air)
*Note: Concentric phase can be further divided into drive and explode phases, the explode phase involves the study of moment right before takeoff.
Collectively these 5 phases of vertical jump is illustrated in figure below with corresponding Force-Time graph that shows the precise force output an athlete is exerting against the ground during each phase of the jump. This combination of mechanical illustration and force quantification is key in the understanding of vertical jump mechanics. It allow scientists to identify specific positions influencing jump performances and enables a targeted approach to jump diagnosis and training prescriptions. In the next section we will examine the first three phases of the vertical jump in detail.
Eccentric (Loading) Phase
The eccentric phase is when athletes sequentially bends from the hip, knee and ankle to load the lower body with a large amount of energy. During this phase muscles and tendons lengthen (the reason it is called eccentric contraction; force production as the muscle lengthens) to store elastic energy just like compressing a spring.
A common misconception of the eccentric phase (including myself earlier on in my coaching career) is people confuse it as a phase for 'force absorption'. This is inaccurate as the objective of eccentric phase is actually for force production. If we look at the Force-Time curve above, the forces are actually increasing during the eccentric phase, indicating that increasing amount of forces are been generated and pushed into the ground. Now, if forces are been absorbed then there will be no increases in ground force application. An easy at-home experiment will hopefully help you understand this concept, find yourself a bathroom scale and do a push up with one hand on the scale. As you can see in the video above as you lower eccentrically there is a corresponding increase in the weight you exert into the ground, at the same time you will also feel increasing tension around your chest, shoulder and core musculature.
Specific technical execution of the loading phase starts with the engagement of an active core that allows the torso to move as a compact unit while the lower body undergoes eccentric loading. In the Standing Vertical Jump the arms are actually the body part that initiates the downward movement. Soon after the downward arm swing the lower body begins to bend sequentially starting from the hip - pulling it back and down - to the knee and finally the ankle. At this point athletes should focus on maximal loading through the posterior chain (glutes and hamstring). We should use this opportunity to bust a common myth in vertical jump training regardingf knee- vs hip-dominant jumpers. If you have heard this rationale before the truth is there is no such thing as knee-dominant jumpers, all jumps should be initiated through the hips and any jump that is performed from the knees are simply poor sequencing and faulty movement patterns. Special attention should be paid to athletes with longer limbs, due to their long levers they tend to favour eccentric lowering by bending their knees so training for this population needs to reinforce proper motor patterning.
Amortization (Transitory) Phase
The amortization phase is the lowest part of the squat in the process of jump preparation. It is a transitory phase that bridges the load and drive phase where athletes transition from descending for force accumulation to ascending for take off. This mechanical reversal also requires a change in muscular actions, during the amortization phase muscles switches from eccentric isometric contraction; Isometrics contraction is when muscle produces force while it does not change in length.
The goal of the amortization phase is to maintain the forces that has been generated during the eccentric phase and deliver it into subsequent concentric action. The Force-Time profile below is a measure of Standing Vertical Jump force output collected from one of my elite basketball player, it provides a graphical insight that clearly separates the three distinctive phases of SSC action during the vertical jump. Ironically, in my opinion it is more advantageous for athletes to produce jump signatures that exist more as a continuum that seamlessly conjugate the forces from all three phases of the jump. Hence the present example implies that this athlete have difficulties to perpetuate forces from eccentric to concentric contraction. A special note here, we cannot make conclusive diagnosis that the current athlete lacks isometric strength based on his inefficiency to maintain force output during the transitory period (this is a common mistake made by Sport Scientists and Performance Coaches). This is because the force output in this graph represents the 'outcome' of force generation and not the actual mechanism behind 'how' the forces are been generated or where the 'energy leaks' are coming from. A full examination is beyond the scope of our current discussion.
Technically, the Standing Vertical Jump should see the athlete in a lock-and-loaded position from the ankle, hip and shoulder joints. The shoulders should be leaning forward, positioned over the toes with an active torso that is at about 45-60 degrees angle. Stiffness should be generated from the hip muscles - primarily the glutes and hamstrings - if an athlete fails to produce and maintain stiffness as they transition through these phases then a significant amount of elastic energy will be lost; resulting in a highly inefficient and over-strenuous jump that increases the risks for injury. Two key landmarks that we look for to ensure athletes maintain elastic stiffness during the transition:
(i) posture and torso angle; and
(ii) knee should be between the bottom of the shoe lace and tip of the toes.
If an athlete's knee shifts beyond the tip of their toes (as is the case in the amortization mechanics picture) it indicates that they have lost the elastic energy loaded from the previous phase and they are now trying to reconcile by overexerting the quadriceps to power the jump.
Concentric (Drive) Phase
The concentric phase is when the athlete starts to ascend from the lowest point in the transitory phase to power the body for takeoff. The muscular action during this phase is when the muscles shorten and all the elastic energy that has been accumulated from prior phases are finally released to augments power production. Contrary to popular belief where many programs emphasize on training the concentric portion of the jump but the reality is the majority of the work has already been done by this point in time.
As mentioned previously, the concentric phase can be divided into drive and explode. The drive phase is when the athlete is ascending, exerting as much pressure into the ground as possible and the explode phase is the moment right before toe-off. Assessing the explode phase of a jump is actually critical as the velocity of the body right before it leaves the ground is a Key Performance Indicator that ultimately dictate jump performances; the greater the velocity at toe-off, the bigger the jump. Technically, one of the key performance cues for our athletes during the explode phase is to swing the arms upward as aggressively as possible to generate maximal momentum in the upwards direction.* Once the athlete is in full flight we should see the upper limb-torso-hip-ankle in a streamlined fashion that signifies efficient joint-by-joint energy transfer. Lastly, because we expect the athletes to project themselves ballistically when they are in flight mode we expect to see their feet to shake a little, this indicates a complete relaxation at the ankle joints.
*We have a saying that you drive through your lower body and explode through your upper body
In part 1 of this article we have discussed important biomechanical principles involved in the vertical jump. Understanding this information is key for any training program trying to maximize jumping potential. In part 2 of this article we will look to take this information further and analyze the key mechanics of two jumping variations: 1-foot and 2-foot running jumps, where we will dissect jumping techniques from an actual basketball game.
Laffaye G. (2014). Countermovement jump height: gender and sport-specific differences in the force-time variables. J Strength Cond Res 28 (4): 1096-1105