HLPE3531 Biomechanics NFL Punt

‪How can a punter (NFL/Gridiron) improve on their overall kicking height/distance utilising Biomechanical principles and what other factors surround this skill from a Physical Educators perspective?

By Alex Watkins 

Flinders University Education and health sciences student

Introduction

“Biomechanics has been defined as the study of the movement of living things using the science of mechanics.”(Hatze, 1974) It is through biomechanics that we are able to analyze and justify reasons as to why certain skill ‘inputs’ result in varied outputs or what we see as the end result of a executed skill. As an example, the punt in football has a large number of intricate movements and factors that determine the overall distance that can be achieved by the ball (post impact) from the foot. A punter in the NFL is often considered to have one of the easiest jobs on the football field. This is largely due to the ideology that their sole purpose is to go on the field, conduct a skill that in some cases takes less than two seconds to perform (the punt), and then return to the sideline. It is my understanding that there is much more than meets the eye to the apparently simple punt.

 The following is a detailed analysis of the key elements associated with the ‘Punt,’ including biomechanical principals such as Coefficient of restitution, angular velocity, projectile motion and other factors surrounding the punt. In addition to this the implications that this knowledge has on Physical education teachers and their practices will also be addressed.




(the science of the Punt and its factors overview)

Prior to describing the punt in more detail, it is first necessary to understand what a ‘kick’ is, as this is an essential skill that must be developed prior to learning the punt. "Kicking is imparting force to an object by the foot and the leg. The kicking of a stationary object is the foundation for the kicking of a moving object and for punting.”(Wuest, D. 2009, pp.214)

Components of the kick

the kick, Six step model

• The approach

• Generating foot speed

• The role of the support leg

• Impact

• Follow-through

(Rath, D. 2000)

The Punt, much like the kick has very similar components, however they are utilized in a different manner, as it is a time bound skill that allows for limited approach.

The Punt 

5 step approach to the punt

•    The approach and catch

•    The backswing of the kicking leg

•    TheDrop 

•    The connection of the ball and foot

•    And finally the follow through

Punt follow through

Understanding the basic movements involved in a Punt, we will now look at the biomechanical principles that affect a punter and their ability to achieve maximum distance and height when punting the football

Some of the biomechanics involved Include;

• The coefficient of Restitution
• Angular Velocity
• Projectile Motion

The Coefficient of Restitution

"The ball shall be made up of an inflated (12 1/2 to 13 1/2 pounds) urethane bladder enclosed in a pebble grained, leather case (natural tan color) without corrugations of any kind. It shall have the form of a prolate spheroid and the size and weight shall be: long axis, 11 to 11 1/4 inches; long circumference, 28 to 28 1/2 inches; short circumference, 21 to 21 1/4 inches; weight, 14 to 15 ounces.”(NFL, 2011) This is the case for all of regulation gameplay, however there is a point in the game that this rule is exempt. When a Punt is in progress, a replacement ball is substituted into the game. This ball is pumped up to a greater degree than the other portions of the game. the reason for this is found in the balls coefficient of restitution. "The coefficient of restitution describes the proportion of total energy that remains with the colliding objects after collision." (Blazevich, A. 2010) By increase amount that the ball is inflated they are increasing the footballs restitution and therefore there is less energy being lost within the object. If the ball that is used for Punting was the inflated to the same degree as the ball that Quarterbacks use to throw, the recorded Heights and distances that a punter is able to punt would be far less than they are with the current greater inflated footballs. Understanding that the footballs used when punting have a great restitution insinuates that punters should be aiming to strike the football in the middle (belly) of the football in attempt to transfer as much force from their foot through to the ball.

Angular Velocity

“Angular velocity is the rate of change of angular displacement.”(HyperPhysics, 2000) The greatest angular velocity of a Punters Foot is the main focus when looking at this biomechanical principle. It is however also important to understand how a greater angular velocity can be achieved by a punter. “The most powerful movements originate from the midline of the body, and travel towards the extremities, transferring and adding power as they go.”(Williams, D. 2013) 

This transferal of movement and force is also known as ‘summation of forces’. It is the summation of forces that run from the slight transversal rotation of the torso through to the sagittal rotation of the upper leg (thigh) and finally followed by the added sagittal extension of the knee and lower leg, finishing with the slight flexion of the ankle.

 It has been established that this summation of forces is very reliant on timing and is often the reason that some more skilled punters will be able to achieve greater results in terms of distance and height than less skilled punters.(Miller, S. 2004) It can be noted that the torso is not moving at a very large velocity in this process, it does in fact play a part in distributing velocity through the leg and further onto the foot when attempting a Punt in Football. This improves the Angular Velocity of the distal segments of the leg which have shown to be the primary determinants of the overall distance a football will travel when punted.(Macmillan, 1976)

example of summation of forces and necessary
 timing to produce maximum force.

This produces the maximum amount of momentum being transferred from the upper metatarsals /ankle to the ball.

Projectile Motion

Projectile motion can be defined as simply as it sounds. It describes a projectiles (in this case the projectile is the football) motion that occurs post having a force exerted on it (in this case after point of contact with the foot when punted). “Throughout the path of the projectile, change occurs only in the vertical direction due to the influence of gravity, while the horizontal component of the velocity will not change. (This is not quite true, there will be a very small slowdown in the horizontal direction due to air resistance).” (Top End Sports, 2013) Projectile speed is a large factor determining the distance a projectile is able to travel. This is connected largely to the angular velocity that a punter is able to transfer through the summation of force from his foot to the football.

More importantly for a Punter is the Projection Angle. This is due to the situational aspects of the game that the punter will face. A punter that is trying to achieve maximum distance should kick the football at an angle of 45 degrees relative to the ground.

results of projection angle on a projectile.

 “At a projection angle of 45 degrees, the object will have an equal magnitude of the vertical and horizontal velocity and its range will be maximized.” (Blazevich, A. 2010 pp.26) In Contradiction to this, a Punter may find the need to kick the ball a shorter distance but still need the ball to stay in the air for a long amount of time. In this case the punter would increase the projection angle to an angle situated somewhere between approximately 60 and 75 degrees but will exert the same amount of force on the ball. This football will travel higher in the air, it wont travel as much distance, however it will still have the same hang time due to the force exerted by the punter will be similar to the distance punt and therefore the acceleration experience in flight by the football due to gravity will take the identical amount of time (neglecting wind and air resistance)  to return to the ground.

Further knowledge - "An ideal punt will involve a tight spiral, in which the long axis of the ball stays aligned to the line of the balls trajectory. This improves both hang-time and range because air drag is minimized." (Gay, T. 2004)

  

Summary of Skill and Biomechanical Principles

As it has been mentioned the so Called simple task that Punters have of Punting a football are much greater in complexity than many believe. Punters have to receive a snapped ball, take a step while winding up their kicking leg, drop the ball correctly so that the flat bottom surface of the ball (the belly) is falling directly to the ground, make contact with the ball and finally follow through the ball promoting maximum transferal forces of inertia. In addition to this we now know that they must conduct this skill with the knowledge of the many biomechanical factors that will effect the outcome of their punt. These include the above-mentioned Coefficient of restitution, angular velocity of their torso, leg and foot and the principles of projectile motion that will have affect on the football while in flight. Still being able to have the ball land in the very close proximity that punters often intend proves the degree of difficulty that is involved with this skill and is an impressive feat to say the least.

With this knowledge, what implications are posed for Physical Educators?

“One of the primary concerns of Physical education, exercise science, and sports professionals is the learning and refinement of motor skills.”(Wuest, D. 2009 pp185) while understanding how to achieve the greatest height and distance is applicable to the Sport of Gridiron (NFL Football) it can also be established to have many other uses. “Though there is no one perfect approach to Integrated Curriculum it is about guiding the students through open ended questions in which the information can be used to scaffold their learning.” (Vanson, M. 2013) through this method student can use many of the techniques, principles and skills surrounding this area and transfer these skills to other sporting skills (soccer kick), but the information surrounding the biomechanical principles can also be a form of cross curricular methods of teaching allowing students to utilize the knowledge learned in this area within other areas of their education (Maths and Physics)

The Answer

A combination of appropriate skill execution, practice, body composition and understanding of some simple biomechanical principles can allow anyone who is attempting to better their ability in the area of punting achievable.

References

-       Blazevich, A. (2010) 'Sports Biomechanics The Basics, Optimizing Human Performance.’ A&C Black Publishers Ltd

-Gay, T. (2004) Football Physics, The Science of The Game' Holtzbrink Publishers

 -  Hatze, H. (1974). The meaning of the term: “Bio- mechanics.” Journal of Biomechanics, 7, pp. 189–190.     

-        HyperPhysics (2000) ‘Angular Velocity’ Department of Physics and Astronomy. Georgia state university View at http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html on 23/04/2013

- Isport (2013) 'How to Punt the Football.' Skill level Intermediate Viewd at http://amfootball.isport.com/amfootball-guides/how-to-punt-the-football on 23/04/2013

-Kermond, J. (1975) 'Biomechanical Parameters of Punt Kicking' Masters Thesis, University of Western Australia.

-       Luhtanen, P. (1984) 'Development of biomechanical model of in-step kicking in football players.' Report of the Finnish F.A. 1/1984. Helsinki, Finland

     

Macmillan, M. B. (1976) 'Kinesiological determinants of the path of the foot during the football kick.' The Research Quarterly, 47 (1), 33 - 40.

    Miller, S. (2004) ‘Kinematics of Drop Punt Kicking in Australian Rules Football- Comparison of Skilled and Less Skilled Kicking.’ Human Movement of the Victoria University, Department of Human Movement, Recreation and Performance, Melbourne, Australia

-       National Football League (2011) ‘Official Playing Rules and Casebook of The National Football League’ accessed at http://www.nfl.com/static/content/public/image/rulebook/pdfs/2011_Rule_Book.pdf on 23/04/2013

-       Rath, D. (2000) 'Biomechanics of kicking. Presentation.' Australian Rules Coaching Course. Amsterdam, Netherlands.

-       Top End Sports (2013) ‘Projectile Motion’ The Sports and Science Resource. Viewed at http://www.topendsports.com/biomechanics/projectile-motion.htm on 23/04/2013

-       Trapa, P. & Sellwood, S. (2012) The science of the punt viewed at http://youtu.be/y0N3YvdwR4w on 23/04/2013

-       Vanson, M. & Carter, A (2013) ‘Intergrated curriculum’ EDUC 3525 student conducted tutorial.

-       Williams, D. (2013) ‘Summation of Velocities to Create Power and Accuracy’ Range of Motion, Viewed at http://www.rangeofmotion.net.au/blog/summation-velocities-create-power-and-accuracy on 23/04/2013

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Wuest, D. & Bucher, C. (2009) 'Foundations of Physical Education, Exercise Science and Sport.' McGraw-Hill, sixteenth edition.