Introduction

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

·         Follow through

Figure 1

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

 

Figure 4

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.

The Backswing of Kicking Leg

Figure 5

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

Acceleration of the Kicking Leg and Foot

Figure 7

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

Extended Follow Through

Figure 9

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: 

Answer

Figure 10

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

Ball, K. (2011). Biomechanics of punt style kicks in football codes. In Proceedings of the 7th world congress on science and football. Nagoya. Retrieved from http://www.shobix.co.jp/jssf/contents/supplement.

Blazevich, A., Sports Biomechanics the Basics: Optimising Human Performance, Bloomsbury, 2012.

Brancazio, P. J. (1985). The physics of kicking a football. The Physics Teacher, 23(7), 403-407.

Fowler, I. (2005). How Rugby Can Benefit from Improved Kicking Technique: A breakdown of AFL kicking technique and its portability to rugby.

Haines, T. L., Erickson, T. M., & McBride, J. M. (2012). Kicking power. Strength & Conditioning Journal, 34(6), 52-56.

Kellis, E., & Katis, A. (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of sports science & medicine, 6(2), 154.

Lephart, S. M., & Henry, T. J. (1996). The physiological basis for open and closed kinetic chain rehabilitation for the upper extremity. Journal of Sport Rehabilitation, 5, 71-87.

National Football League. (2011). Official Playing Rules and Casebook of the National Football League. 

Orchard, J., Walt, S., McIntosh, A., & Garlick, D. (2002). Muscle activity during the drop punt kick. Science and football IV, 32-43.

Youlian, H. (1992). What is Sports Biomechanics?. Olympic Review, 30, 620-626.