Introduction to American Football
American football has origins within England through the 19th
century, where a soccer player decided he was sick of be constrained to only
using his feet in the game, he then proceeded to pick up the ball and run it
down the field. Obviously this was against the rules in soccer, but this made
way to the development in the game of rugby (Embassy, US. 2010). This new sport become a worldwide success
and reached America during the 1800’s, it was mainly popular in north-eastern
colleges, but then found it’s way across the countries other main universities.
Over time the round ball changed form to an 'egg shape', at this time the game of
football was very different to the game played now. During the 1800’s rules
were changed and manipulated until a final verdict was reached. In 1920 there were
more than 10 professional football teams across the United States, and in just
over 10 years later, the first National Football League (NFL) championship game
was played (Embassy, US.2010).
The position of the ‘quarterback’ is derived from the
positions in the game of rugby, where positions of half and full back existed.
This is where NFL manipulated the rules of their game to allow for a forward
pass, which the quarterback is responsible. The quarterback has one of, if not
the most important job within the team and game of NFL. The quarter back receives
the ball, and in a split decision must make an accurate pass to another receiving
player. The quarterback must absorb a number of changing variables, make a decision,
and make the pass. With millions of viewers, fans, and economic parties across
the globe the quarter back must make their decisions and passes, or risk their
multi-million dollar contracts. An example of this is Ben Roethlisberger a quarterback for the Pittsburgh Steelers, he is the eleventh highest paid athlete for 2015, earning $48.9 million a season (Badenhausen, K. et. al. 2015).This illustrates the importance of good
technical form within the skill and a technical comprehension of the game play.
What are the optimal biomechanics of the quarterback throw, in American Football?
There are a number of variable factors that can influence
the play within the game of NFL from defensive, offensive, or special plays. The
coaches offensive play tactic will influence what the quarterback is to do from
the ‘snap’ (beginning each play), the quarterback will usually then proceed
with a passing or running play. Depending on the defensive play chosen from
opposing team will influence the decision of the quarterback in the offensive
play. It is important for the quarterback to receive and release the ball as
quick as possible so as to not get sacked (tackled before releasing the ball)
as this can result in negative yards or a ball turnover, which can alter the
overall result of the game. From the snap the quarterback must then analyse the
changing conditions on the field and make the pass to one of their receivers in
order to gain yards in order to get into the end zone.
The answer through the biomechanics
The step and gather
The
step and gather is the first stage of the quarterback throw, this is an
important stage of the skill as it provides the quarterback the opportunity to
read the play and make a decision on what to do in that moment of the game (Fleisig,
G. et. Al. 1996). The quarterback will take a number of steps back away from
the line of scrimmage, stopping with a wide footing providing a stable centre
of mass (Blazevich, A. J. 2013). The quarterback will hold the ball near the
chest, with the leading shoulder facing the direction of play. This helps to maintain the control of the
ball, while maintaining high eyesight over the field of play thus helping
gather the information of the play. Image 1, Tim Tebow demonstrates the biomechanical
aspects within the step and gather in the quarterback throw. His eyes are looking down the field analysing
the field of play (indicated in yellow), his leading shoulder is facing down
the field toward the target options (indicated in blue), the ball held close to
the chest (indicated in red), ready to deliver the ball to one of his receivers.
The position of the body in this stage of the throw allows the player to
generate torque (Blazevich, A. J. 2013).
Image 1, Tim Tebow in the step and gather, shoulder and eyes facing down field, with the ball close to the chest (Authorityfootball.com 2015).
The leading arm
Image 2, Tim Tebow ready to throw the ball with the leading arm pushing away from the body, with an equal and opposite reaction of the throwing arm (Authorityfootball.com 2015).
The throwing/cocking arm
The cocking arm is in direct relation to the leading arm
velocity and Newton’s third law of motion, as they are an opposite reaction of one
another (Fleisig, G. et. Al. 1996). The key phase of the cocking arm it reach a
90 degree angle from the arm pit to the hand (image 3, indicated in yellow), the forearm
and hand should be parallel to the mid-line of the body (image 3, indicated by
yellow). This produces torque through angular velocity, where the magnitude of
the force produced causing rotation of the body is known as the moment of force
(Blazevich, A. J. 2013). Newton’s third law states that “The acceleration of an object is proportional to the net force acting
on it and inversely proportional to the mass of the object”, this is
directly related to the force produced by the quarterback. Increasing the force
production to overcome the inertia can be altered by technical changes. Tucking
the arms and ball in close to the body can help generate the power in the
earlier stages of the skill, as they are closer to the primary source of power,
which in this case is the trunk and shoulders (Blazevich, A. J. 2013). The throw can utilise linear velocity as well,
although it is usually reliant on the angular velocity, as the quarterback
doesn’t always get the chance to accelerate along a flat straight line. The
acceleration of the arm is the rate of change in velocity from the cocked
position to the ball release; the acceleration is a vital aspect of the throw
as it indicates how fast the ball will leave the hand (Blazevich, A. J. 2013).
The faster the ball is travelling through the air, in theory means it should
arrive at the target faster and is less likely to be intercepted by an
opponent.
Image 3, Tim Tebow ready to throw the ball with the throwing arm cocked at 90 degrees, parallel to the mid-line of body (Authorityfootball.com 2015).
Follow through
The throwing follow through is derived from momentum, as the
force generated through the throw is transferred into the ball, the throwing arm
will hold the momentum and follow through after the ball is released (image 4, indicated
in orange). The greater the force produced in the throwing movement, the
greater the momentum followed through from the throw. The plant foot is a key
component in reducing and stopping this carry through momentum, this is called
braking impulse (Blazevich, A. J. 2013). This is when the plant foot is placed
in front of the body’s centre of mass, and it relates directly to Newton’s
third rule. As there is a large force placed on the foot as it hits the ground
(image 4, indicated in yellow), there is an equal and opposite reaction force (which is
also called the ground reaction force GRF) which is transferred back toward the
body (image 4, indicated in red) and thus lowering forward momentum and propulsion of
the body (Blazevich, A. J. 2013).
Image 4, Tim Tebow ready to throw the ball with the plant foot ready to stop momentum of the body after the throw (Authorityfootball.com 2015).
Projectile motion
Projectile motion refers to an object (in this case a ball)
projected at an angle into the air. Gravity and air resistance are considered
to be the main aspects that affect the projectile once in the air. The flight
path of the ball is dependent on the trajectory of the ball, this is the angle
and speed of release of the ball (Blazevich, A. J. 2013). The range of the ball
is directly affected by the projection speed. In theory, the faster the
projection speed, the further the ball will go. The angle of projection will
greatly affect the trajectory of the ball also, generally 45 degrees is considered
optimal, but in the case of NFL, the angle may differentiate each throw
depending on the offensive set play. This is where the relative height of
projection becomes a defining factor taken into consideration for the
quarterback. The relative height of projection refers to the vertical point of
release compared to where it lands. If the ball lands (or caught) at a higher
point then release, this is classified as positive. Whereas is the ball lands
below the point of release, this is negative (refer to image 5). This can
make the projection angle a defining aspect when considering accuracy of the
throw, depending on where the ball is to land, or be caught will alter the
trajectory angle (Blazevich, A. J. 2013).
Image 4, Shows the difference in positive and negative relative release height, with reference to release angle (Blazevich, A. 2013).
Fluid Dynamics - Drag
Image 5, Shows the difference of particle flow around different shape objects indicating that the object with longer leading edges, separates the particles a lot better (Blazevich, A. 2013).
Image 6, Shows the difference between laminar and turbulent flow depending on the shape of the object's backside (Blazevich, A. 2013).
How else can we use
this information?
There are a number of biomechanical aspects mentioned within
the blog, these aspects can be implemented into training programs to help develop
an understanding of the optimal biomechanics of the quarterback throw (Wuest, D. et. al. 2009). The
skill can be broken down into small sections to allow the player to develop
their understanding of what they can do to manipulate and refine their ability
in performing the skill (Davids, K. et.al. 2008). These biomechanical aspects
can be applied in a number of other sports, as they are a base of knowledge to
help refine and understand the way the body works when performing select
skills (Wuest, D. et. al. 2009). The biomechanics can allow coaches, teachers, and players the ability
to understand how to improve results through the complex systems theory (Davids,
K. et.al. 2008). This is the process of integrating a number of complex systems
and movements to understand and increase skill level.
References
Authorityfootball.com,.
(2015). The Quarterback Mechanic: 4 Keys to Optimal Throwing Motion | Authority
Football. Retrieved 16 June 2015, from http://www.authorityfootball.com/x-and-o-labs-and-the-quarterback-mechanics
Badenhausen, K., Lawrence,
M., Estevez, D., & Wood, R. et al. (2015). Ben Roethlisberger. Forbes.
Retrieved 18 June 2015, from
http://www.forbes.com/profile/ben-roethlisberger/?list=athletes
Blazevich, A. J. (2013).
Sports biomechanics: the basics: optimising human performance. A&C Black.
Davids, K. W., Button, C.,
& Bennett, S. J. (2008). Dynamics of skill acquisition: A constraints-led
approach: Human Kinetics.
Embassy, U. S. (2010).
History of American Football.
Fleisig, G., Barrentine,
S., Escamilla, R., & Andrews, J. (1996). Biomechanics of Overhand Throwing
with Implications for Injuries. Sports Medicine, 21(6), 421-437.
doi:10.2165/00007256-199621060-00004
Wuest, D. A., & Fisette, J. L. (2009). Foundations of
physical education, exercise science, and sport. McGraw-Hill Higher Education.
