Biomechanics of the Basketball Jump Shot

Sunday, June 19th 2016

What are the optimum biomechanics of the basketball jump shot?

Author: Danielle Rose, Flinders University

Introduction

The jump shot is one of the most common shots used in the game of basketball and the ability to shoot an effective jump shot is critical to a player’s success. It is effective because it give added power to the shot for range and also allows the player to elevate their body above their opponents, making the shot harder to defend and block (Elliot & White, 1989; Knudson, 1993; Darst et al, 2012). The jump shot is described by 2016 Collins Online English Dictionary as, ‘a shot at the basket made by a player releasing the ball at the highest point of a leap’.

Professional basketballers are able to successfully execute a jump shot with high consistency through practiced and optimised biomechanical techniques in relation to their jump shot. This blog will break the jump shot down into 3 phases - the preparation phase, the production of power phase and the release and follow through phase. It will discuss and apply the biomechanical principles within each phase ultimately answering the larger question “What are the optimum biomechanical principles for accuracy in scoring a goal in basketball using the jump shot?”

The Preparation Phase

Producing Force

A correct setup of the basketball jump shot is one of the most important elements to achieving a successful outcome. Coaching literature is consistent with directing players to square up to the basket and jump in a vertical direction as much as possible.

Flexion of the Hips, Knees and Ankles

Bringing the body’s centre of gravity low by having the feet should width apart will provide balance, the creation of power and for enhancement of propulsion. Okazaki, Rodacki & Satern (2015), promote this additionally suggesting placing the shooting side foot slightly in front of the body to increase vertical stability for the jump and also for reduced shoulder, trunk and pelvic rotation during the release phase. As the joints of the ankle, knee and hip begin to flex, the player should have a slight forward inclination of the trunk which further allows for the lowering of the centre of gravity, more power from the jump and more stability for vertical displacement (Miller and Bartlett, 1996; Knudson 1993; Okazaki et al, 2015; see image 1). 

Image 1: Stephen Curry's jump shot preparation stance showing
hip, knee and ankle flexion (Author: Unknown).

Once in this crouched position, the player can create a force against the ground to propel themselves vertically enough to produce vertical velocity on the ball for the shot and to be able to take the shot over their opponent. The higher the force put into the jump preparation, the higher the jump outcome will be.

Newtons 2^nd and 3^rd Laws of Motion

For a higher jump in the jump shot we need to apply Newton’s 2^nd and 3^rd laws of motion. 

Newton’s 2^nd law states that:

“The acceleration of an object (in this case the player’s body in a vertical motion) is proportional to the net force acting on it and inversely proportional to the mass of the object” (Blazevich, 2007). 

To jump higher, we need to apply more force to the ground which is where Newton’s 3^rd law of motion comes into play also: 

“For every action, there is an equal and opposite reaction” (Blazevich, 2007). 

When the player jumps, a downward vertical force is applied where the feet contact the ground, and the ground exerts an equal and opposite reaction force, the ground reaction force (GRF). To create a higher jump, the player must apply a greater force into the ground during the jump phase (Blazevich, 2007). The adoption of the greater flexion of the ankles, knees and hips in the crouch position generates an increase GRF for the jump and ultimately can increase the ball release velocity (Elliot & White, 1989). 

The force in which the player must exert into the ground to jump is measured in newtons (N) and can be calculated with the formula: F (force) = m (mass) a (acceleration). Acceleration on earth is 9.81 m·s, due to gravity, so therefore a player with a mass of 90kg would calculate their needed minimum force to leave the ground as:

                      F = ma

                      F = 90kg x 9.81m·s

                      F = 882.9 N

This shows that in order for a 90kg player to propel themselves into the air for a jump shot, they would need to exert more than 882.9 N of force into the ground to jump. 

Flexion of the Shoulder, Elbow and Wrist - (also see image 1).

Many authors report the importance of the influence and contribution of shoulder, elbow and wrist flexion in the preparation of the jump shot (Okazaki et al, 2015; Knudson, 1993; Miller and Bartlett, 1996). 

The shoulder lifts the ball in preparation phase by flexing to an angle where the humerus is approximately parallel to the ground, with the shoulder angle at 90 degrees. For shooting further away from the basket, some players will have a later and smaller flexion in the shoulder angle, which allows more force to be extended through to the ball (Miller and Bartlett, 1993; 1996). 

Elbow flexion is another way of creating force behind the ball. The optimum flexion angle of the elbow for preparation is approximately 75-90 degrees, however this changes from player to player with some adding more flexion for more power to the shot, though this can produce a higher degree of freedom which can alter the shot line and therefore not equate to a successful shot (Knudson, 1993). To reduce the amount of degrees of freedom, players should keep their elbow in line with their eyes and pointed towards the basket (Knudson, 1993).  

Wrist flexion is also optimal for a faster and more accurate shot. The flexion of the wrist in preparation phase not only creates a safe spot for the ball to be held, but creates potential energy for the release of the basketball (Knudson, 1993).

The Production of Power Phase

Ball and Body Elevation

Summation of Forces

From the crouch position, where the player exerts the downward force and the GFR exerts a reaction back, they must then coordinate the body segments in a proficient manner as to produce a summation of these forces through the body to achieve not only the desired position at the release point but also for the desire release height and velocity of the ball at release (Okazaki et al, 2015; Elliot & White, 1989). Wuest and Bucher (2011), specified that the forces applied by the muscle groups must be directed in the same path and in proper sequence order for the release of the greatest force. In order to produce the greatest summation of forces, the player must crouch low and exert a force from their legs against the ground, which when they jump, moves upward through their body right to the fingertips where the ball is released (Martin, 1981; Okazaki et al, 2015; see image 2). Optimum bending angles vary from player to player depending on mass and height of the player as well as the opponent’s stature. The amount of flexion at the hips, knees and ankles during the crouch will depend of the amount of height the player is trying to achieve for their jump shot.

Image 2:The direction of the summation of forces produces through the body during a jump shot.
(Author: Unknown). 

The Kinetic Chain – Acceleration from push-like and throw-like patterns

This summation of forces through the body’s muscular link system whilst producing the jump shot is classified as an open kinetic chain (Elliot & White, 1989). The kinetic chain is the ‘chain of events’ of movement which the segments in the body have on each other as the jump shot is in motion (see image 3). There is much debate in whether the jump shot utilizes a push-like pattern or a throw-like pattern (Miller & Bartlett, 1996; 2007; Knudson, 1993; Elliot & White 1989). The preparation and jump in the jump shot has been likened to that of a push-like movement pattern where we “extend all the joints in our kinetic chain simultaneously in a single movement” (Blazevich, 2007; Knudson, 1993). This simultaneous push movement off the ground from the legs, cumulates a flow of forces (torques) through the joints and muscles in one single motion. 

Though the jump is a push-like pattern, and often the free-throw shot is a push-like pattern (due to the need for less force and trajectory and more accuracy to be accomplished), the upper body parts of the kinetic chain in the jump shot are more likely to be performed in a throw-like motion (Knudson, 1993; Elliot & White, 1989). This is because in a throw-like movement pattern, the shoulder, elbow and wrist joints “extend sequentially, one after another” (Blazevich, 2007). However, as the distance of the jump shot increases, Miller & Bartlett (2007), argue that the shot becomes more push-like, due to a decrease in the shoulder angle and motion. This push-like motion exerted when shooting from a further distance for increased force to be extended to the ball, requires simultaneous shoulder flexion and elbow extension, with the ball release being more rectilinear rather than curvilinear, as seen in the release from a closer distance. With either shooting style, if the order of the kinetic chain is disrupted, shot accuracy will not be ideal as the optimum order of the kinetic chain will be broken. Image 3 shows the segments of the kinetic chain in optimum order as the summation of force flows through the body in the jump shot. 

Image 3: The sequential order of the kinetic chain segments of the jump shot.
(Author: Unknown)

Mechanical Energy - Potential and Kinetic Energy

The kinetic chain of the jump shot, can further be broken down into the concept of mechanical energy which consists of potential and kinetic energy.

Potential energy (PE), is a form of mechanical energy which is associated with the stationary position of an object before motion (Blazevich, 2007). It is called potential energy as it has the potential to gain velocity where it would have kinetic energy (KE). Kinetic energy is the energy related with motion. The greater the PE the greater it’s KE would be during the movement of the object (Blazevich, 2007).

In the basketball jump shot, there are two sets of potential and kinetic energy. The flexion of the lower body joints, resulting in a crouch, holds the potential to be released into kinetic energy when the body moves upward on the jump. The setup phase where the player is preparing to jump is the potential energy. The production of greater power in the jump gives a higher vertical velocity to the player’s body, which means it has a higher kinetic energy (Blazevich, 2007).

The ball also has potential energy where it is placed on the hand as it has the potential to be released and acquire a movement velocity, it will have its own kinetic energy as it travels through the air. Once the player jumps into the air, the potential energy turns to kinetic energy which flows up the kinetic chain and into the hand, releasing the potential energy of the ball giving it acceleration through the air and therefore, also kinetic energy.

The Release Phase

Projectile Motion

Ball Trajectory

The ball trajectory has been shown to be affected by the release angle, the velocity and the height of release (Blazevich, 2007).

Release angles can be anywhere from 0 to 90 degrees, where it will travel horizontally and vertically in relation to its speed and height of release (Blazevich, 2007). From the ground, a projection angle of 45 degrees will have maximum range as the object has an equal magnitude or vertical and horizontal velocity (Blazevich, 2007). However, in the game of basketball where the ball is released from a height above the ground the other trajectory factors need to be taken into account.

Players are generally encouraged to shoot the ball at the highest point of the jump though most players are seen to release the ball just slightly before the peak (Knudson, 1993; Okazaki et al, 2015). This allows for greater transfer of the force from the velocity of the vertical displacement of their body to the ball. Releasing the ball just after the highest point of the jump requires a larger generation of force from the upper body for the ball to make the distance to the basket (Okazaki & Rodacki, 2012), however this is often seen from taller players inside the key where they jump higher but release the ball with a lower velocity at a higher angle of release to get the ball over the front of the ring.

Due to this, several optimal angles of release of the ball in a jump shot have been documented and is still debated (Okazaki et al, 2015; see table below).

AUTHOR(S)	RELEASE ANGLE (degrees)
Elliot (1992)	44-47
Miller & Bartlett (1993)	47-52
Miller & Bartlett (1996)	48-55
Hamilton & Reinschmidt (1997)	55-63
Rojas et al (2000)	44-47
Okazaki & Rodaki (2012)	65
Okazaki, Lamas, Okazaki & Rodaki (2013)	63

The release angle of the ball is not only affects the range (Blazevich, 2007), but also is directly related to the angle of entry into the basket (Miller & Bartlett, 1996), therefore a higher release angle results in a larger area for the ball to enter the basket (Miller & Bartlett, 1993; 1996; Okazaki et al, 2015; see image 4). However, the greater the release angle, the greater the release velocity required and a higher energy expenditure used by the player, particularly as the distance increases from the basket (Okazaki & Rodacki, 2012).

Image 4: The angle of release is directly related to the angle of entry. The greater the angle of release the more open the basket will be and therefore will allow more room for error. (Author: Okazaki & Rodaki, 2012).

Blazevich, (2007), states the faster the release velocity, the further the ball will go. In a study by Elliot & White (1989), they discovered that the projection speed of the ball was normally significantly higher for a jump shot further from the basket than the shots taken closer the basket and the projection angle also declining as distance increased. They further found that the shoulder angle at release also decreased as the shot distance increased from the basket, though range of movement through the shoulder increased. This was because the player needs to make the ball travel at a greater distance and energy was spent in creating a greater horizontal velocity on the ball rather than vertical velocity (Okazaki & Rodacki, 2012).

Therefore, the optimum release angle at the time of the shot, is the angle which requires the smallest possible release velocity, yet allows for maximum accuracy (see image 5). This is at a constant change depending on distance from the basket and height of the shooter in relation to the basket (the relative height of projection), hence why there is such a difference in degree optimization (from 44 -65 degrees) between authors (Hamilton & Reinschmidt, 1997; Okazaki & Rodacki, 2012; Miller & Bartlett, 1996; Rojas et al, 2000).

Image 5: The optimal release angle depends on the release height, the projection speed and the distance from the basket.
(Author: Unknown).

Levers – Extension of the upper body flexions

The trajectory of the ball is ultimately determined by the angular and linear velocities of the joints of the shooting arm at the moment of release (Elliot & White, 1989). In biomechanical terms this can be explained through the principal of levers. When shooting a jump shot, the arm and the hand acts as two 3^rd class levers which assist in creating a major propelling force on the ball as it travels through the air to the basket (Elliot & White, 1989). 

The 1^st lever is where the effort (where the triceps muscle connects to the forearm) is applied between the fulcrum (elbow) and the load (ball) [see image 6]. This lever action results in the extension of the elbow where the triceps muscle goes from an eccentric to a concentric contraction. Complete elbow extension, 180 degrees, is seen as a characteristic in professional players jump shot (Okazaki et al, 2015), with further authors considering a quick snapping extension of the elbow on release of the shot to add immense velocity and release height to the ball (Miller & Bartlett, 1996; Knudson, 1993). A high elbow technique alleviates the effect of angular motion in the shoulder which simplifies and stabilizes the shooting arm in a more linear direction (Elliot & White, 1989). Stability in the elbow lever during extension is important as if this shooting arm deviates sideways it may cause misalignment with the basket causing a lateral rotation to be applied at the release of the ball.

Image 6: The lever can be seen as the forearm snaps over the elbow at the release of the ball generating higher release velocity in both vertical and horizontal directions. (Author: Unknown). 

The 2^nd lever, ultimately becomes the 'goose neck' follow through which is highly sought after from coaches at the end of the jump shot. It can be seen where the forearm tendons and muscles (effort) is applied between the wrist (fulcrum) and the ball (the load) [see image 7].

Image 7: The wrist becomes the fulcrum to engage the flick of the wrist which produces back spin on the ball.
(Author: Unknown)

The wrist becomes a fulcrum which the load is projected over upon the extension of the wrist when applied in a snapping motion, which gives the ball backspin and accuracy when it comes off the fingertips. A snapping extension and hyperextension of the wrist is seen as an ideal follow through in order for a faster and more accurate jump shot outcome as it applied a backspin on the ball (see image 8). 

Image 8: The 'goose neck' showing the flexion, extension and hyperextension of the wrist which produces spin of the ball due to the follow through and the ball spinning off the fingers. (Author: Unknown).

Back spin produced by the wrist snapping motion, can produce a higher chance of the ball going into the basket if it happens to hit the ring or the backboard due to the quick deceleration of the ball on contact (Hamilton & Reinschmidt, 1997). It can also create more of a curve on the ball resulting in a (slightly) longer and higher flight path due to the Magnus effect (see image 9).

Image 9: Picture which shows the Magnus effect on a ball when it is propelled through the air.
(Author: Unknown)

When shooting, the follow through entails a snapping of the wrist in a downward direction causing the ball to rotate as it travels through the air in a clockwise direction. The airflow syncs with the rotation, pushing the air up, over the ball and down (as seen in image 9). The side of the ball moving away from the player (the bottom) works against the airflow (which is moving downward), and the side coming toward the player (from the top) works with the airflow (Blazevich, 2007). The air coming toward the ball is halted which causes higher pressure on the forward side of the ball causing it to lift giving it longer flight time (Hamilton & Reinschmidt, 1997). 

When all these biomechanical principles are put together correctly, you will be left with a beautiful looking jump shot which should always result in SCORE!!! See below for a short video a break down of Stephen Curry's dubbed 'perfect jump shot' (Retrieved from: https://www.youtube.com/watch?v=HOiH1eVCggw).

How else can we use this information?

There have been links associated between the basketball jump shot and the netball shot. There is no rule in the game of netball that dictates not being allowed to perform a basketball style jump shot to score. Therefore, any netball shooters wishing to improve their own shooting skills may well be able to use the biomechanical principles in this blog for their own gain. Furthermore, similar principles of kinetic chain and summation of forces during the preparation phase have been likened to that of the preparation for the jump in the tennis serve, and also the jump in  a volleyball spike. Similar principles may be used from this blog in order to extend the height of the jump in the tennis serve, or for the jump in preparation for a volleyball spike. 

In addition, this blog forms a foundation for many other questions which can be explored in biomechanical terms in relation to basketball shooting. The differences between close and further distance shots, along with height of players can be further focussed on as differences in these were only just touched on. Also the difference between the set shot, or free throw and the jump shot could be compared using the information in this blog. 

Word Count: 2789

References

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Cockcroft, G. (2016). In Collins English Dictionary. Retrieved from http://www.collinsdictionary.com/dictionary/english/jump-shot

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Highnessfsk (2013, May 15). Sport science: Stephen Curry Retrieved from https://www.youtube.com/watch?v=HOiH1eVCggw

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Okazaki, V., Rodacki, A., & Satern, M. (2015). A review on the basketball jump shot,. Sports Biomechanics, 14(2), 190–205. doi:10.1080/14763141.2015.1052541

Rojas, F. J., Cepero, M., Ona, A., & Gutierrez, M. (2000). Kinematic adjustments in the basketball jump shot against an opponent. Ergonomics, 43(10), 1651–1660. doi:10.1080/001401300750004069

Wuest, D. A., Fisette, J. L., & Bucher, C. A. (2011). Foundations of physical education, exercise science, and sport - 17th edition (17th ed.). Dubuque, IA: McGraw Hill Higher Education.