Kinematic Performance of an Olympic Event - Research Paper Example

KINEMATIC PERFORMANCE OF AN OLYMPIC EVENT INTRODUCTION Olympic events encompass various sports in which thousands of athletes from all over the world compete to be recorded as the fastest, highest or furthest in the entire planet. Running events are the oldest in Olympics history. Besides long distance marathons, one of the categories in the Olympics is sprint running, which include distances of 100 metres, 200 metres, 400 metres, and 800 metres, as well as relay races that require sprinting at the highest speeds possible. Physical analysis of the runner’s actions are vital for improving performance and to identify the appropriate biomechanics to prevent sport injuries. According to Arampatzis et al (1999), kinematics relates to the dynamics of the motion: the distance moved, the stride length, the speed, the consistency, and the acceleration. The biomechanics of the action pertain to the foot position, the leg flexion, the angle of the body and various other factors that constitute the running/ sprinting gait of the athlete. On the other hand, kinetics relate to the forces that cause movement according to Newton’s Law, and the forces that act on the runner’s body, such as friction, power, impulse and torque. Thesis Statement: The purpose of this paper is to investigate both the kinematical performance of sprint running at the Olympic Games and the kinetics, in relation to Newton’s Laws of Motion, and to identify the biomechanics of the whole action. DISCUSSION Newton’s three Laws of Motion form the basis for explaining the relationship between kinetics and kinematics in movements such as sprint running. Kinetics in Relation to the Kinematical Performance of Sprint Runners Newton’s First Law of Motion states all objects have the inherent property to resist a change in their state of motion. An increase in the mass creates inertia, and decrease in the speed of the body. Newton’s first law forms the foundation for the inertia principle in biomechanics. Newton’s Second Law of Motion is considered to be the most important law of motion because it describes how the forces that create motion (kinetics) are associated with motion (kinematics) (Knudson 2003). The second law is known as the law of momentum or the law of acceleration. Newton’s Second Law states that the rate of change of momentum of an object, that is the acceleration is proportional to the force causing it, and takes place in the direction in which the force acts. That is, acceleration = mass x velocity (mv). Increasing the mass creates inertia, hence athletes lighter in weight are believed to be capable of greater speeds. Thus, increasing force or decreasing mass are both important for increasing the speed of the body (Knudson 2003). Newton’s Third Law of Motion is called the law of reaction because it states that for every action there is an equal and opposite reaction. An important implication of this law is that reaction forces can change the direction of motion opposite to the applied force, when the force is applied on objects with higher force or inertia. This is illustrated in the following way: at the moment of push off during running, the athlete exerts a downward and backward push with the foot. This action creates “a ground reaction force which propels the body upward and forward” (Knudson 2003, p.135). The extreme mass of the earth easily overcomes inertia and the ground reaction force accelerates our body in the opposite direction of force applied to the ground. Another illustration is the action of the eccentric muscles, where the muscles are used as brakes which push in the opposite direction to another force. Research conducted by Mero et al (1992) found that running speed is the result of stride length, stride frequency, force production or decrease in ground contact. At faster running speeds of more than 7 metres per second, stride frequency increases more than stride length for up to 2.6 metres stride length and 5 Hz frequency. Further, with increase in running speed, force production increased by up to 4.7 times body weight. In the case of a heel striker, the force would be 5.5 times body weight at 9.5 metres per second. The maximum speed ground contact was 0.08-0.1seconds. Pertaining to the kinetics involved in sprint running the concept of Impulse is related to Newton’s Second Law. This states that the change in momentum of an object is equal to the impulse of the resultant force in that direction. Thus “Impulse is the effect of force acting over time” (Knudson 2003, p.145). This is measured as: force x time applied = impulse to an object. In sprint running, the force of impact of the foot with the ground along with the duration of impact creates impulse, which is related to momentum. Momentum is the vector quantity which according to Newton describes the quantity of motion of an object, and it is calculated as the product of mass and velocity. The impulse-momentum relationship is the same mechanical law that forms the basis of the force-time principle. Hence, if a person applies force for a longer period of time: a larger impulse, they “would be able to achieve a greater speed or change in momentum than if they used similar forces in a shorter time interval” (Knudson 2003, p.147). An illustration for the force-time principle is the maximum velocity phase of a sprint run, in which elite sprinters’ foot contact times are approximately 100 ms, hence requiring the application of large forces in a relatively short time. As a result, training methods that facilitate the development of force-time profiles with an initial rate of force development and force and total impulse at 100 ms, are found to be superior as compared to athletes who may have a greater maximal force capability. Hence, the force-time principle can be used to improve sprint running speed (Ackland et al 2009). The linear speed of a sprinter or the athlete’s limb “is a function of the angular velocity of the joints” (Ackland et al 2009, p.186), which is dependent on angular acceleration. Athletes can increase movement velocity by increasing joint torque which is the moment of force, or reducing limb inertia. The Biomechanics of Sprint Running Kumagai (et al 2000) have found from their research study that individual muscles as well as groups of synergist muscles adapt in a regionally particular manner, according to the type of exercise performed. An example is that well trained sprinters have more of their muscle mass located in the upper thighs, as compared to the non-athletic control group. Resistance training for sprinters to develop most of the muscle mass distributed close to the axis of rotation as in the hip joint, would be advantageous. Stride length is measured as the sum of take-off distance, flight distance and landing distance. Take-off distance is the horizontal distance that Centre of Gravity is forward of the take off foot at the instant the foot leaves the ground. Flight distance is the horizontal distance that the Centre of Gravity travels while the runner is in the air. Landing distance is the horizontal distance that the toe of the lead foot is forward of the Centre of Gravity at the instant the sprinter lands (Ackland et al 2009). Similarly, there are other important criteria impacting the speed of the sprinter. Fig.1. Picture Exhibiting Minimum Hip Angle (Bushnell 2004, p.22) Fig.2. Picture Exhibiting Minimum Knee Angle (Bushnell 2004, p.23) Fig.3. Picture Exhibiting Knee Extension at Toe-Off (Bushnell 2004, p.24) In figures 1, 2 and 3 above, the sprinter’s minimum hip angle, the minimum knee angle and the knee extension at toe-off are illustrated. Evidence from research conducted by Bushnell (2004) reveals that stride length is directly connected to the hip and knee angles, and the speed at the start is impacted by the knee extension at that time. At maximal speed, the sprint group in the study recorded a significantly longer stride length than their distance counterparts, while at touch down they exhibited an equal shank angle. According to Challis (2001), an increased stride length is usually associated with a larger shank angle. Bushnell (2001, p.15) points out that “as the runner overstrides, the lower leg reaches out further in front of the body, leading to a heel strike and a high braking effect”. However the study found that sprint technique allows the runner to produce a longer stride as well as position the shank nearly vertical at touchdown. This is attributed to more time for grip at ground contact due to a more powerful push-off, a quicker leg recovery, and higher thigh amplitude. Other factors such as foot position, coordination of arms and legs and body angle also determine the athlete’s speed. CONCLUSION This paper has highlighted the kinematical performance of an Olympic event: Sprint Running. The association of the kinetics of sprint running with the kinematics of the action have been investigated in relation to Newton’s Laws of Motion. The biomechanics of the whole action in relation to stride length, hip angle, knee angle, knee extension and other factors with respect to speed have been discussed. Thus, it is clear that kinematical and biomechanical analyses of sprinting can help improve performance and also prevent the occurrence of sport injuries. REFERENCES Ackland, T.R., Elliot, B. and Bloomfield, J. (2009). Applied anatomy and biomechanics in sport. Edition 2. The United Kingdom: Human Kinetics. Arampatzis, A., Bruggemann, G.P. and Metzler, V. (1999). The effect of speed on leg stiffness and joint kinetics in human running. Journal of Biomechanics, 32 (12): pp.1349-1353. Bushnell, T.D. (2004). A biomechanical analysis of sprinters versus distance runners at equal and maximum speeds. Thesis submitted to Brigham Young University. Retrieved on 12th February, 2009 from: http://contentdm.lib.byu.edu/ETD/image/etd634.pdf Challis, J.H. (2001). The variability in running gait caused by force plate targeting. Journal of Applied Biomechanics, 17 (1): pp.47-54. Knudson, D.V. (2003). Fundamentals of biomechanics. New York: Springer. Kumagai, K., Abe, T., Brechue, W.F., Ryushi, T., Takano, S. et al. (2000). Sprint performance is related to muscle fascicle length in male 100-m sprinters. Journal of Applied Physiology, 88: pp.811-816. Mero, A., Komi, P.V. and Gregor, R.J. (1992). Biomechanics of sprint running. Sports Medicine, 13: pp.266-274. Read More