Introduction
The Free-Throw shot is perhaps the most underrated
shot in the game of basketball. Taken after an offensive player is fouled
whilst in shooting motion, from approximately 4 and a half metres away from the
hoop with no defensive pressure, the player has the opportunity to redeem the
points that may have been gained but were inhibited due to being fouled. It has
been reported that as many as 20-25% of all points in a game are gained at the
Free-Throw line (Hays & Krause, 1987; Merskey, 1987). Furthermore, research
has shown that in 80% of close games (NCAA Division 1 games) the team with the
higher free-throw percentage won the game (Kozar, Vaughn, Lord & Whitfield,
1995). It’s been found that free-throws determine the outcome of as many as
one-half of NCAA division 1 games played in a season (Kozar, et. al. 1995). The
importance of executing this skill correctly then, is indeed significant to
overall team success within the game of basketball.
The aim of this blog is to represent the skill of
basketball free-throw shooting using biomechanical principles in order to
answer a number of questions. the main question being;
Using Biomechanical Principles, What is the Optimum
Free-Throw Shooting Technique in the Game of Basketball?
To answer this question, different biomechanical
principles will be discussed and relevant skill cues will be suggested.
Shooting the Traditional Free-Throw
To execute the traditional free-throw efficiently, we can
break the skill down into easily manageable skill components. For the
traditional approach, it can be broken down into 5 movement phases, they are;
Skill Cue: Trunk extension, hands spread. The next and most important step to the free- throw comes in an important sequence: the knees extend first, followed by shoulder flexion, then elbow extension and wrist flexion (performed at the same time). Skill Cue: Extend knees, raise ball, extend elbow and ‘snap’ wrist. (See video from: http://www.youtube.com/watch?v=D1YsAYPF4yQ)
Law Number 3: “For every action,
there is an equal and opposite reaction.” (Blazevich, 2010, p. 45).
Essentially, every action that we do in life, walk, run, push, jump, the will
have an equal and opposite effect allowing us to move in the direction we push
from. The way this is important in the free-throw comes back to the stance of
the shooter, if the feet are evenly spaced facing toward the basket, when the knees
are bent and then extended, the opposite reaction will be upwards, towards the
basket. If a poor stance is adopted, a lateral component will be added, meaning
the opposite reaction will be counter-productive in terms of an effective
free-throw. See Figure 2 for a visual representation of Newton’s Third Law.
- Preparation
- Backswing
- Force Production
- Shot Release
- Follow Through
Preparation
In the preparation phase, players may adopt a personal
routine that is consistent and repetitive; generally this involves a few
dribbles and is a helpful way of reducing anxiety, helping to focus attention,
eliminate distractions and enhance confidence prior to the shot, as well as
allowing for the player to visualise the upcoming movements in sequence (Czech,
Ploszay & Burke, 2004). The player should then adopt a stable shooting
stance where the legs are approximately shoulder width apart, the shoulders are
facing the basket and the foot corresponding the shooting hand is either
slightly in front of (toes overlapping), or parallel to the other, in order to
create an even base of support (Hudson, 1982). A stance that is more than
slightly staggered (one foot too far in front of the other) can result in the
players placing too much weight on the front foot, resulting in poor weight
transfer throughout the rest of the shot. Foot placement that is too wide in
nature (feet further than shoulder width apart) will introduce a lateral
component to the pushing of the feet against the floor as the shot is being
released, this can be related to Newton’s Third Law of Motion where every
action has an equal and opposite reaction (this will be discussed further in later
posts) (Brown & Clement, 1987). A stance that has the feet too close
together will have a narrow base of support, therefore leaving a greater
opportunity for an unbalanced release and overall shot (demonstrated in figure
1).
After the player
has been through their personal routine, they should pick up the ball with both
hands, spreading the fingers of the shooting hand to create greater control of
the ball and fingers should be directly behind the ball, rather than to the
side (Hartley & Fulton, 1971). Skill Cue: Routine dribbles; Feet shoulder-width
apart, slightly staggered, eyes on the basket.
The player should then hold the ball stationary at waist level, ready for release. The shoulder of the shooting hand should be parallel with the body, with the upper arm held against the trunk. The elbow of the shooting hand is tucked in just above the waist, and the shooting hand placed behind and slightly under the horizontal mid-line of the ball, leaving the wrist extended (bent backwards) to allow for the optimal release angle and provide propelling force for the shot. Skill Cue: Shooting arm against trunk, elbow in. The opposite hand should be placed on the side of the ball, not gripping the ball too hard, but simply supporting it and guiding the ball for the optimal flight path. Skill Cue: Shooting hand behind ball, other hand supporting the ball.
The player should then hold the ball stationary at waist level, ready for release. The shoulder of the shooting hand should be parallel with the body, with the upper arm held against the trunk. The elbow of the shooting hand is tucked in just above the waist, and the shooting hand placed behind and slightly under the horizontal mid-line of the ball, leaving the wrist extended (bent backwards) to allow for the optimal release angle and provide propelling force for the shot. Skill Cue: Shooting arm against trunk, elbow in. The opposite hand should be placed on the side of the ball, not gripping the ball too hard, but simply supporting it and guiding the ball for the optimal flight path. Skill Cue: Shooting hand behind ball, other hand supporting the ball.
Backswing
The backswing component of the free-throw consists of the
movements that happen in the crouching position prior to the release. Knee and
trunk flexion are both important parts of the backswing. The knees should be flexed
to an angle of roughly 90 degrees, with the trunk flexed close to 50 degrees
from a vertical position.
Skill Cue: Bend the knees. Flexion of these body parts is important at this stage of the shot as they are both key in the summation of forces leading to the release of the shot. Flexion of the knees and trunk transfers weight down through the leg muscles in preparation for the shot where they will be extended. The amount of elastic storage in the muscles is said to increase with increased flexion, however, too much flexion has been found to increase tension on the neck muscles and distract the shooter from the target (Alexander, N.D.).
Skill Cue: Bend the knees. Flexion of these body parts is important at this stage of the shot as they are both key in the summation of forces leading to the release of the shot. Flexion of the knees and trunk transfers weight down through the leg muscles in preparation for the shot where they will be extended. The amount of elastic storage in the muscles is said to increase with increased flexion, however, too much flexion has been found to increase tension on the neck muscles and distract the shooter from the target (Alexander, N.D.).
Force Production
The ball should be raised up towards shoulder level using shoulder flexion and the trunk should begin to extend. This trunk extension will result in the knees becoming slightly more bent, as more weight is placed through them, beginning the summation of forces. The fingers of the shooting hand should be well spread and the ball sitting on the pads and base of the fingers, not directly on the palm. The force producing movements begin when the trunk is fully extended, the ball is just above shoulder level and the knees begin to extend. From here, the knees and hips should be extended and the ball further elevated by shoulder flexion.Skill Cue: Trunk extension, hands spread. The next and most important step to the free- throw comes in an important sequence: the knees extend first, followed by shoulder flexion, then elbow extension and wrist flexion (performed at the same time). Skill Cue: Extend knees, raise ball, extend elbow and ‘snap’ wrist. (See video from: http://www.youtube.com/watch?v=D1YsAYPF4yQ)
Critical Instant
The critical instant is the point of release of the ball,
after this point, there is nothing that the shooter can do to influence the
flight of the ball. At the release, the legs, trunk and arms should all be fully
extended to indicate that the body parts have all made a full contribution to
the shot. A near vertical shooting arm is good sign that optimum vertical
velocity has been conveyed through the ball (Alexander, N.D.). The wrist should
be in mid flexion at the time of release, as this will ensure the hand is
moving at maximum velocity, helping to create more backspin on the ball (Alexander,
N.D.). The non-shooting hand should remain on the ball right until this
critical instant, this way, the shooter has the most time to retain control
over the ball. It is also important that the non-shooting hand remains facing
the ball and not touching it in any way that could produce side-spin on the
ball. In order to create backspin on the ball, the critical instant is the
wrist flexion or ‘snap’ where the elbow is extended and the wrist flexed in a
quick explosive motion, resulting in the ball rolling off the fingertips of the
shooting hand towards the basket. Skill Cue: 'Snap' the wrist.
Follow Through
The final step to the free-throw is the follow through where
all of the joints involved should continue to move through to the full range of
motion after the release of the ball. Once the ball is shot, the legs should be
fully extended, with the trunk vertical. The shooting side hip should be lined
up vertically with the knee. The shooting elbow should be fully extended and
the wrist fully flexed to show that backspin has been applied to the ball. The
shooting arm at this stage could be referred to as a ‘Goose Neck’ or ‘hand in
the cookie jar’. The flight of the ball will be stabilised by this wrist
flexion. (Alexander, N.D.). Skill Cue: upright
position, hand in the cookie jar.
What are the Biomechanical Principles Underpinning the Free-Throw?
Newton's Three Laws
Law Number 1: “An object will remain at rest or
continue to move with constant velocity as long as the net force equals zero”
(Blazevich, 2010, p. 44). The inclination for an object to remain in its
present state is called inertia. If an object has a mass, it also has inertia.
The more mass an object has, the larger the inertia is, making it more
difficult to speed up, slow down or change direction (Blazevich, 2010). In
terms of the free-throw, the player is required to change their state from a
resting position into vertical motion.
Law Number 2: “The acceleration of an object is proportional
to the net force acting on it and inversely proportional to the mass of the
object: F = ma” (Blazevich, 2010, p. 45). Force is therefore required to change
a state of motion. From the equation above, we gather that the more
acceleration we want to gain from an object, the more force we must apply to
it. Therefore, the shooter must apply the right amount of force to the
basketball to gain the correct acceleration.
 |
| (Blazevich, 2010, p. 45) |
Law of Gravitation: The
Law of Gravitation says that: “All
bodies are attracted to each other with a force proportional to the product of
the two masses and inversely proportional to the square of the distance between
them.” (Blazevich, 2010, p. 47). Gravity has less influence if the product of
two masses is smaller. Essentially, the lighter we are, the less we are
influenced by gravity. As this gravitational force is trying to keep the
shooter grounded, the shooter must therefore apply a large enough force to
overcome this. As well as this, the shooters inertia is relative to their mass,
and this mass requires a larger force to accelerate when moving vertically (to
combat gravity). So because the shooter is moving vertically in the Free-throw
shot, the force necessary to overcome gravity is greater (Blazevich, 2010).
Momentum
Force is
required for an object to exert velocity in order to overcome inertia, so if
this force is produced in the right direction, the shooter will be accelerated
in the same way (Blazevich, 2010). The free throw requires the shooter to
accelerate vertically and this requires a large force. A force must be applied
to an object in order to change its momentum. As the free-throw requires the
shooter to accelerate vertically, large vertical impulses must be applied. As
impulse is the product of force and time, the shooter will receive a greater momentum
change with greater impulse (Blazevich, 2010). This is exhibited in the
free-throw when the shooter pushes downward on the ground by bending the knees
before propelling themselves upwards.
Summation of Forces
Summation of Forces is the term given to the momentum that propels an object. In the case of the free-throw, the object is the basketball. Maximum momentum is generated through using each segment of the body in a quick sequence, starting from the big muscle groups in the legs (bending/extending knees), working up to the smaller muscles in the arms and hand (shoulder flexion, ‘snap’ of the wrist). It’s the correct timing of this sequence of movements that will generate maximum momentum (Blazevich, 2010). |
| This image represents the summation of forces from the legs to the arms |
Kinetic Chain
The free-throw is an example of a push-like movement, where all
the joints involved are extended simultaneously in one movement. Due to this
simultaneous movement, the torques generated by each joint result in a high
overall force (Blazevich, 2010). Another benefit of the push-like movement is
that all of the joints tend to move towards a straight line motion, which
results in very accurate movements, which is great for the free-throw. The
basketball free-throw is an example of an open kinetic chain, because on end of
the chain is fixed to the ground (the legs), while the other end is open to
move around (the hand) (Blazevich, 2010).
Projectile Motion
Projectile motion refers to the motion of an object (in this
case, the basketball) projected at an angle into the air (Blazevich, 2010). Both
gravity and air resistance can have an effect on the object. A projection can
move anywhere between the angles of 0 and 90 degrees, and the trajectory of the
ball is influenced by the projection speed and angle, as well as the relative
height of projection (Blazevich, 2010). As the distance that the projectile
covers is determined by projection speed, and since the basketball has a
vertical component in the free-throw, the projection speed will determine the
height that the ball reaches before gravity acts upon it, bringing it down
towards the basket. The angle of projection (greater angle = less range, smaller
angle = more range) will affect the angle that the ball (hopefully) enters the
hoop. Theoretically, if the ball is entering the hoop vertically, there is a
greater surface area of the hoop for the ball to fall in, compared to a lower
angled shot that could potentially hit the rim before going in. Gordon and
Reinschmidt (1997) describe the optimum angle of projection as roughly 51
degrees. However, this value would change from person to person, depending on
the shooters height and lever length (arms), as such factors would influence
the optimum release angle.
The Magnus Effect
Simply put, the Magnus effect refers to the role that spin
plays in determining the flight path of an object, in our case, the basketball.
The easiest explanation comes from Blazevich (2010) who says: “a spinning ball ‘grabs’
the air that flows past it because of the friction between the air and the ball...”
(p. 188). Because of this resistance, one side of the ball starts to slow down,
causing the pathway of the ball to drop. Understanding this principle can help
to improve the execution of the free-throw, as the correct amount of backspin
will allow greater opportunity for the ball to enter the basket at the optimal
angle. This backspin is created by the ‘snap’ of the wrist. Another benefit of
backspin is that if the ball hits the back of the rim, it may have more chance
of falling in as it creates friction with the ring. This is something that could be further researched, the effect of backspin on the coefficient of restitution as the ball hits the ring would be another interesting way of gauging the importance of backspin in the basketball free throw.
Reference
List
Alexander, M.
(n.d.) Mechanics of the free throw.
Retrieved from: http://www.flinders.edu.au/slc_files/Documents/Blue%20Guides/APA%20Referencing.pdf
Blazevich, A.
(2010). Sports biomechanics: The basics: optimising human performance
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Body
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Czech, D. R.,
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Brown,
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Hartley,
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