Sports biomechanics is defined as the
science concerned with the motion of internal and external forces acting on a
human body and the effects produced by these forces in sporting activities
(Youlian, 1992, p. 621). Punt kicking is a primary technique used by a specific
positional player known as the “Punter” in American Football. Punting occurs in
American Football when a team kicks the ball to the opposition to relinquish
possession. The aim of the punt is to propel to ball to a particular area of
the field to gain distance for a teammate to ‘run onto’ it (Ball, 2011, p.14). As
field position is one of the key elements to winning a game of NFL football, a
team must have an effective punter which can potentially dictate and change the
game through their specific skill.
The aim of this investigation is to
determine the key biomechanical principles associated with NFL
punting including analysis of Newton’s Three Laws of Motion, angular kinetics, impulse momentum,coefficient
of restitution and projectile motion. Furthermore, an evaluation will be
conducted on how physical educators can implement this information in a
teaching practice.
Major Question
Before unpacking the biomechanical
principles of the punt it is important to understand that kicking is a key
technical skill which leads to a successful punt. Kicking is feature in all
codes of football and is an open-chain kinetic movement involving co-ordination
and movement of the whole body (Haines, Erickson, & McBride, 2012, p. 1). It
is important to note that there are central similar aspects which transfer from
the skill of kicking to punting. However, there are components in the skill of
punting which differ from that of kicking which will be explored in this
investigation.
Components of kicking
·
Preparation
·
Backswing
of kicking leg
·
Limb
cocking
·
Acceleration
of kicking leg and foot
Components of punting
- Preparation and catch
- Backswing of kicking leg
- Limb cocking
- Acceleration of kicking leg and foot
- Extended follow through
Figure 2 |
Understanding that there are two
critical components which differ the kick from the punt.
1.
The
skill of punting implements catching within the preparation stage. This
requires a clean catch and release of the ball before the defensive team blocks
the punt.
2.
The
follow through of the kicking leg extends to the highest possible point as the
punt requires elevation as well as trajectory.
Figure 3 |
The
difference in extended follow through actions is displayed in Figures 3 and 4.
Recognizing
the key components to successfully executing the skill of punting is distance
and elevation, this investigation will now analyse the key biomechanical
components of punting.
For optimal biomechanical performance
the movement phase of the backswing of the kicking leg is crucial to a
successful punt. This requires the dual incorporation of the biomechanical
phase described as Newton’s Second Law of Motion and impulse momentum from the
kicking leg.
Newton’s
Second Law of Motion that the acceleration of an object is proportional to the
net force acting on it and inversely proportional to the mass of the object (Blazevich,
2012, p. 45). This law is governed by the mathematical form: F (force) = m
(mass) a (acceleration). Therefore, to perform a punt successfully in a biomechanical
sense, if the “Punter” increases the force of the backswing of the kicking leg
this increases the mass of the kicking leg which in turn creates faster
acceleration of the kicking leg through the ball. In effect, the state of
motion of the football will change with the application of force from the
backswing of the kicking leg. This application of force will change the
momentum of the kicking leg. Essentially, the greater the impulse, the greater
the change in momentum; this is substantially the impulse momentum relationship
(Blazevich, 2012, p. 53). In effect, the greater force the “Punter” can produce
from the backswing of their kicking leg, this substantial force will generate greater
momentum through the ball. These two biomechanical principles extend on one
another but they must coincide for a successful punt to occur. This phase is
displayed in Figure 5:
Limb Cocking
For optimal biomechanical performance
the hip, knee and ankle of the kicking leg should be cocked at the highest
point of the backswing which should incorporate angular velocity of these
limbs. Angular velocity is the rate of change in angular displacement which is
rotated in a given unit of time (Blazevich, 2012, p. 238). The limb cocking
phase starts when the knees flexes to desired maximal range of motion (Haines, Erickson,
& McBride, 2012, p. 1). The combination of hip extension, back extension,
pelvic rotation and knee flexion stretches these muscle groups creating an
elastic type effect. Therefore, the greater these muscle groups are stretched and
working in synergy, the greater the force will be produced (Fowler, 2005, p.
5). In effect, the angular displacement of the limbs is use will affect the
angular velocity of the body, therefore the faster the kicking leg will
penetrate through the ball (Blazevich, 2012, p. 16). When focussing on this
biomechanical principle, the greatest angular velocity should occur firstly in
the “Punter’s” thigh, then by the shank and finally by the foot to achieve
maximum success (Kellis, & Katis, 2007, p. 154).
Describing
movements using the biomechanical principle angular velocity is illustrated through
the principle planes and axes of the body. This represents the axis about how a
person rotates, moves and is pushed and pulled. Through the analysis of punting
it is established that the transversal rotation of the torso through the sagittal
extension of the upper leg and accompanied with the sagittal extension of the
knee and lower leg, concluding with the flexion of the ankle and foot will
create a successful punting action. This is displayed in Figure 6:
Figure 6 |
The
biomechanical application which should be implemented for optimal performance
in the acceleration of the kicking leg and foot is the throw like movement of
the kinetic chain. Application of this biomechanical phase within the throw
like movement of the kinetic chain will create optimal performance for a
successful. Throw like movements occur when the joints of the kinetic chain
extend sequentially, one after another (Blazevich, 2012, p. 198). In effect,
the angular momentum of the kicking leg is a product of moment of inertia and
angular velocity which creates an elastic like effect for the acceleration of
the foot tendons to recoil at high speed to produce a successful punt. This can
defined as the moment of force, or in biomechanical terms, torque. Torque can
alter the rotation of an object with any given moment of inertia. Increasing the
torque generated by the hip, knee and ankle joints will increase muscle force,
thus creating an increase in angular velocity and linear speed of the leg and
foot during punting (Blazevich, 2012, p. 77). Punt kicking is a throw like motion, with much
work performed eccentrically in the early phases by the proximal muscle groups
and the resulting momentum transferred to distil segments just before ball
contact (Orchard, Walt, McIntosh, & Garlick, 2002, p. 32). The functional mobility
of the kicking leg and foot creates this throw like movement to be an open
kinetic chain movement (Lephart, & Henry, 1996, p. 72-73). This is
displayed in Figure 7:
Foot Contact with the Ball
For optimal biomechanical performance
the “Punter’s” kicking foot at the point of contact with the ball should have
the toes extended forward to ensure the platform on the foot is large and flat.
The foot speed during this phase is critical to a successful punt; this is
dependent on flexibility, sequencing and strength (Fowler, 2005, p. 7). The ball
has a biomechanical influence on this phase of punting. The ball should be made
up of an inflated (12 ½ to 13 ½ pounds) urethane bladder enclosed in a leather
case. The ball shall have the form of a prolate spheroid and the weight should
be 14 to 15 ounces (National Football League, 2011, p. 3). In general gameplay
this is the case, but when a punt is progress a replacement ball with greater
pressure is used, this is known as the coefficient of restitution. In
biomechanical terms this can be described as when the proportion of total
energy that remains with the colliding objects after the collision (Blazevich,
2012, p. 117). In effect, the restitution of a highly inflated football is
greater and therefore creates less energy to be lost during impact causing the
football to travel at distance off the foot. This is displayed in Figure 8:
Figure 8 |
For optimal
biomechanical performance the kicking leg should extend fully after connection
with the football which creates an adequate angle of trajectory or flight path
for the ball to travel. This phase is known as projectile motion. Projectile motion
indicates the motion of an object (in this case a football) projected at an
angle into the air (Blazevich, 2012, p. 25). As it is the “Punter’s” role to kick the
football as far downfield as possible, while keeping the ball inflight as long
as possible, projectile motion plays a pivotal role. The combination of projection
angle and relative height of projection are further important factors in the
skill of punting. The maximum range of the football is determined partly by its
angle of projection, with a greater angle less range will occur and vice versa
when the angle is smaller sufficient range will be attained (Blazevich, 2012,
p. 26). In effect, the “Punter” must launch the football between 45° and 50° angle
of projection to achieve the greatest range and longest flight time to achieve maximum
success for the team (Brancazio, 1985, p. 405). However, if the “Punter” has to
kick the ball a short distance (due to field position) a greater elevation must
be used. This is displayed in Figure 9:
The skill of punting is a complex
biomechanical sequence which must be executed correctly to achieve maximum
success. The “Punter” must receive the snapped ball, take a forward step while
lifting their kicking leg backwards vigorously, then correctly drop the ball
onto their kicking foot through acceleration which creates the ball to have its
maximum moment of inertia. This must be achieved in conjunction with the
biomechanical aspects that will affect the outcome of the punt. Correct sequencing of the biomechanical
aspects results in maximum velocity of the foot at impact. It is the speed of
the foot at contact that is the key factor in successful punting (Fowler, 2005,
p. 3). Furthermore, longer kick distances are associated with greater foot
speed, shank angular velocity and an extended follow through after contact with
the ball (Ball, 2011, p. 45). The full extent of the biomechanical principles
involved with punting are in Figure 10:
How Can We Use This
Information?
Using the knowledge gained from this
investigation can prove to have success in other sporting activities involving
the skill of kicking. Different sports such as Australian Rules Football,
Gaelic football, soccer, and rugby can use the same biomechanical aspects taken
from this investigation to enhance their kicking skills in a school setting, amateur
level or elite standard. In a school setting, educators can teach students
through the method of scaffolding to develop and enhance their kicking skills
in the variety of sports mentioned above. At an amateur level, athlete can
understand and utilize the biomechanical aspects involved within this
investigation. Elite athletes can analyse and study the biomechanical
principles and use the information given to achieve greater advantages over
opposition athletes and teams. The greatest example of a punt which
has great distance and long flight time is NFL star, Marquette King. This is
shown in the video below:
References
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