What are the Biomechanical Principles that underpin the Basketball
Jump Shot?
Introduction
In basketball, the main aim of the game is to pass the ball
through the ring to score a goal. This can be achieved in a variety of
different shooting forms. These forms include the free throw, lay-up and the
jump shot. One of the most common shooting techniques is the jump shot, even
though jump shots in competition are difficult because of the small margin for
error and the uncertainty of defensive pressure
The Basic Jump Shot Technique
Before an analysis of the biomechanics of the jump shot can
be undertaken, the procedure and technique first needs to be understood.
The jump shot technique can be broken down into three very
distinct phases. The preparation phase, the execution phase and the follow
through phase. Each of these phases plays a crucial role in the likelihood
of a successful result.
The Preparation Phase
The preparation phase is the beginning of the shot and is
crucial to the execution. In order to begin the shot, the player needs to be
balanced. In a typical game scenario, the players will usually be moving
forward prior to starting the shot and therefore, the need to be balanced in a
dynamic sense
The Execution Phase
The execution phase comes next in the jump shot sequence. It
is within this phase that the player jumps and shoots the ball. The players aim
is to jump vertically only; this is to ensure that upon landing they remain in
a balanced position
The Follow Through
Phase
The follow through phase is the last phase of the jump shot
and it begins with how the player lands from the jump. It is important that the
player lands back in a balanced position as this will allow them to prepare
immediately for the next action that they need to execute
The Biomechanics of the Jump Shot
Technique
The biomechanical principles that will be examined in the
jump shot context are projectile motion, Newton’s laws, impulse momentum, centre
of mass and ball rotation/spin.
Projectile Motion
Projectile motion refers to the motion of an object
projected at an angle into the air, its trajectory is influenced by the
projection speed, the projection angle and the relative height of projection
Projection Speed
The distance, both horizontally and vertically, is
influenced by its projection speed
In the jump shot there are two projectiles, the ball and the
player in the jump motion. The projectile speed of the ball needs to be both
horizontally and vertically, whereas, the speed of projection for the player in
motion needs to be only moving vertically. When the player shoots, their aim is
to release the ball as close as possible to the peak of the jump. This is when
there is virtually no forward or upward/downward speed which could affect the
players’ judgment of how much force to exert on the ball, as this forward
motion would then be transferred onto the ball (Sport NZ,
2010) .
The vertical velocity of the body contributes to the balls vertical velocity,
which can then propel the ball higher than the optimal angle of release (Knudson,
1993) .
Projection Angle
The angle of projection is an important factor affecting the
projectile range. If an object is projected vertically, it will land back at
its starting point. So its range is zero. Objects can be projected at angles
between 0
There has been much debate about what the
angle of release should be for the jump shot technique. Research has found that
it is difficult to pinpoint an exact angle due to factors like court position,
height of release, shoulder angle and trunk angle all affecting the angle of
release (Brancazio, 1981) (Knudson,
1993) .
However, research has found that release
angles between 45
“Balls
shot with these trajectories have a better chance of passing through the basket
than shots with a flatter release angle. Shots closer to the basket or shots
from shorter performers will require release angle in the upper range of
desirable angles.” (Hudson, 1985)
Figure 1: Illustrates
the trajectory path of a basketball released at a 45
angle (Hudson, J.L., 1982)
Relative
Height of Projection
The angle that the player releases the
ball is greatly determined by the height that the ball is released. An
optimized height of release decreases the distance the ball must travel and
decreases the ball velocity needed to provide an optimal angle of entry. (Knudson,
1993)
Studies have found that if the ball is released at a height below the basket,
the angle will have to be greater than 45
, the lower the player is, the greater
angle is needed (Sport NZ, 2010) . If a jump shot was to be attempted at midrange
to the ring, an angle of 52
would provide the ball with minimum speeds and
allow for a clean entry through the ring (Knudson, 1993) .
Newton’s Laws
Newtons Laws of Motion are three physical
laws that form the basis for classical mechanics. They describe the
relationship between the forces action on a body and its motion due to those
forces (The American Heritage Dictionary, 2009) .
Newton’s
First Law
“Newton’s
First Law states: An object will remain at rest or continue to move with
constant velocity as long as the net force equals zero.” (Blazevich,
2010) .
This law is also known as Newtons Law of
inertia. All objects with a mass have inertia and the larger the mass, the more
difficult it is to change the objects’ state of motion/inertia (Blazevich,
2010) .
This applies to the jump in the jump shot
technique as well as the movement of the ball. As the player wants to jump off
the ground, they must change their inertia to a vertical motion. This law also
comes into effect as once the player has left the ground for the jump, they
will initially move upwards and only begin to descend when acted on by the
force of gravity (Ville, 2011) . This also applies
to the ball. Once the player has shot the ball, it will continue to move
horizontally through the air until the effect of gravity pulls it back down. To
be able to change the state of motion of both the player and the ball, Newton’s
second law will apply.
Newton’s
Second Law
“The
Acceleration of an object is proportional to the net force acting on it and
inversely proportional to the mass of the object” (Blazevich,
2010) .
To change an objects’ state of motion, a
force needs to be applied (Blazevich, 2010) . This can be applied
to the jump shot as the player applies a force on the ball to accelerate it out
of the hands, causing the ball to suddenly gain momentum towards the goal. As a
result the ball acts back on the player, Newtons third law (Dr Simonetti,
J., 1994) .
However, the player does not take off with an equal speed in the
opposite direction due to the player having a greater mass than the ball (Dr Simonetti,
J., 1994) .
Therefore, they will not accelerate backwards (Dr Simonetti,
J., 1994) .
Newton’s
Third Law
“For
every action, there is an equal and opposite reaction” (Blazevich, 2010) .
This law is closely linked to Newton’s
second law. When a force is applied, there is an equal and opposite force
applied back. This occurs in the jump shot when the player applies a force onto
the ground to begin the jump, the ground then applies an equal and opposite
reaction force against the player, causing them to accelerate vertically off
the ground (Blazevich, 2010) . This law also
applies to the force that the player applies to the ball when shooting. When force
is applied to the ball, the ball applies an equal and opposite reaction force
against the players hands. The ball will then move forward, while the player
remains in the same position due to their mass being greater than that of the
ball, Newtons second law (Dr Simonetti, J., 1994) .
Impulse Momentum
In a game scenario it is likely that the
player will be running before they attempt a jump shot. For this reason the
impulse momentum should be examined to determine the best possible way the
player can transfer their horizontal momentum into the vertical jump and not
transfer too much momentum onto the ball.
Impulse momentum refers to the
relationship between an objects product of force and time, known as an impulse
and the momentum. The greater the impulse, the greater the change in momentum (Blazevich,
2010) .
An important element of change in impulse momentum is the breaking impulse and
the propulsive impulse. The player needs to be able to apply a quick breaking
impulse followed by a larger vertical impulse to change the direction that they
are travelling (Blazevich, 2010) . The player wants to
have a shot breaking impulse and spend as little time on the ground as possible
before beginning the jump. This is done by ensuring the foot lands further in
front of the body’s centre of gravity toe first (Blazevich,
2010) .
Centre of Mass
Centre of mass plays an important part in the jump shot
technique. Before starting the jump shot, the player must be balanced. This is
achieved by having a stable base of support with the centre of mass above the
base. When the player applies the force to jump, they want to keep the centre
of mass central, so that whole body rotation is not produced, which would cause
an unbalanced landing (Sport NZ, 2010) . Research has found highly
skilled players have less horizontal shift in their centre of mass during the
shot (Knudson, 1993) . This is because the
highly skilled players have the ability to;
“manipulate their body
parts, while the centre of mass of the body rises and falls during the jump,
according to the law of conservation of momentum. First they bring their legs
up under the body, which tends to draw the upper body down relative to the centre
of mass, and then rapidly extend their legs to thrust the upper body upwards as
the body’s centre of mass falls” (Blazevich, 2010) . This creates the
‘hanging’ effect that can be seen in the jump shot technique of experienced
basketball players.
Ball Rotation
The spin that a player applies at release
is critical in creating a “soft” shot that will rebound into the basket, if it
does not pass cleanly through the ring (Knudson, 1993) . If a player does
not apply any spin on the ball upon release, it may hit the backboard or ring
flat. This will cause the ball to spring off in any direction. The spin on the
ball will assist it to deflect downwards back into the ring. Research has found
that backspin applied to the ball in a jump shot serves to decrease the
horizontal velocity of the ball if it strikes the rim, or causes the ball to
deflect downwards if it strikes the backboard (Alexander, 1990) . It increases the
shooter’s margin for error (Alexander, 1990) .
There are two techniques that allow
players to generate backspin on the ball in a jump shot, the action of the
wrist and the angle of the forearm.
Studies have found that “when the ball is held with the correct grip
and the forearm is aligned vertically, the shooter can apply pure backspin on
the ball. The tendency for shooters to let their elbow drift laterally during
the shot takes the arm out of alignment with the basket and causes the ball to
spin with a sideward component that may deflect it off the rim.” (Knudson,
1993)
The flection of the wrist is also
essential in creating backspin on the ball. The flection of the wrist happens
rapidly at the end of the shot upon the release of the ball. Research has found
that highly skilled shooters release the ball with their wrist slightly
hyper-extended and it stays in this state after the ball has completely left
their hands for the follow through (Knudson, 1993) . An incomplete follow-through means
that the wrist flection is already slowing at release, rather than peaking to
create good ball rotation (Knudson, 1993) .
How can we use this Information?
This information can play an important
part in teaching the basketball jump shot or correcting players’ techniques.
Now that the biomechanical principles that underpin the jump shot are
understood, coaches, teachers and players can look at individuals’ techniques
and analyse what they might need to change in order to become more successful
and efficient.
References
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