Skill: Sprint Running
The biomechanical principles of running contain various technical concepts which explain why the movement of running is exerted to its optimal level of speed and how to improve the speed of a runner at a certain distance.
The blog will outline what principles are involved that underpin a fast running technique for sprint running as well as displaying and discussing through the use of pictures and diagrams to support my claim.
Inquiry Question:
What are the biomechanical principles that underpin an efficient fast running technique for sprint running?
Identifying the biomechanics of the activity:
Force:
Newtons Third Law: For every action, there is an equal and opposite reaction.
'We need to exert a force to cause an object to change its velocity and to overcome its inertia. During running we apply a force with vertical and horizontal components. The ground exerts an equal and opposite GRF, which can accelerate us forwards if the force is large enough to overcome its inertia' (Blazevich, A.J. 2012).
Angular Momentum:
Product of the moment of inertia and angular of velocity; angular analogue of linear momentum.
Moment of Inertia: (I)
Because of inertia, objects tend to remain in whatever state of motion they are in unless acted upon by an external force (Newtons first law). 'To move the leg backwards from the front of the body (called the 'swing phase' of running) we need to overcome the inertia of the leg. Since the leg swings with the hip as the centre of rotation (pivot point) we use the term moment of inertia' Blazevich, A.J. 2012).
It is also stated that 'elite sprinters and endurance runners for that matter, are able to bend their leg very effectively so that their moment of inertia is minimised and the angular velocity increased' (Blazevich, A.J. 2012).
Braking Impulse:
It is stated braking impulse involves the 'product of the applied force and the time over which it is applied acting to slow an object (often occurs at foot-strike in running)' (Blazevich, A.J. 2012).
Angular Velocity:
'Angular velocity is the rate of change in angle or rate of change in its angular displacement; equal to angular displacement per unit time' (Blazevich, A.J. 2012).
Acceleration:
Acceleration involves the rate of change of velocity. It is pointed out that 'in many sports, the calculation of acceleration is very important: for example, sports in which chasing-catching is important, the athlete who can most quickly change direction and accelerate will usually win' (Blazevich, A.J. 2012). Acceleration is an important biomechanical principle in determining the best possible sprint running for a person as well as keeping in mind a strong technique for optimal performance.
The Recovery Phase:
'The motion of moving the leg from in front, to behind the body is the 'swing phase' and the motion of moving it to the front again is the 'recovery phase'. It is important to complete each phase quickly when sprint running' (Blazevich, A.J. 2012).
Speed and Velocity:
= distance/time (s=d/t)
This can be best achieved by improving maximum technique. Within the principles of speed and velocity, these two principles are mainly focused on determining how quickly did the runner run and how to tell the speed with which someone moved. The connection between the two is scalar (speed) and vector (velocity).
Identifying secondary questions to guide research:
1. What would be the first biomechanical principle to begin with applying a sprint technique?
2. What would be the first biomechanical principle to begin with applying a fast running speed?
3. What would be the best starting position for a sprint runner?
4. What would be a simple biomechanical model to determine the important biomechanical principles of a race?
5. How can we modify an athletes performance of sprint running?
6. What would be the best recovery phase for a sprint runner?
7. How can these biomechanical principles of sprint running benefit an athlete for further physical activity?
The Answer:
Since the biomechanical principles have been briefly discussed within the context of an efficient sprint technique and applying a fast sprint, the answer lies within how to apply these as well as looking at the secondary questions to support this.
Firstly, as the physical education teacher it will be important to apply effective teaching strategies in achieving the best sprint and technique. Firstly, it is stated that ‘sprinting has previously been described as consisting of a series of phases: an acceleration phase from 0 to 10 m, a transition phase, and then a maximum velocity phase from 36 to 100 m during a 100-m sprint’ (Cronin, J. and Hansen, K.T. 2006)
To reach an improvement for the athletes running technique and speed, incorporating trials to record their times will display the athletes acceleration time, maximum speed time (top-speed phase) and the deceleration time in the recovery phase. It is explained that 'we can then see how running time might differ if we ran each section a little more quickly or slowly. This area of improving sprint running in altering part of their performance is called modelling' (Blazevich, A.J. 2012).
Race Phase
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Actual
Time (s)
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Accel
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Max
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Decel
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Max and Decel
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Acceleration
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Maximum Speed
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Deceleration
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Average Speed (m.s -1)
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Total Time (s)
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So, the answer is if the athlete can improve their running speed, they will more likely have a stronger performance over the distance of 100m.
This answer is supported by effectively explaining that 'angular momentum of the legs increases through the movement and peaks during foot-ground contact. The arms must precisely counter this by producing an equal and opposite angular momentum, which is greatest during food-ground contact' (Blazevich, A.J. 2012). This is where Newtons Third Law is underpinned, For every action, there is an equal and opposite reaction.
We use our arms to counter rotations created by the movement of the legs; therefore, errors in the leg technique can be seen within the variations in the optimum arm swing. Coaches and Physical Education Teachers need to watch the arms closely to make connection of what the athletes legs are doing in the way of momentum and power.
It is also supported through this answer in claiming that 'the downward and backward arm swing should be vigorous because it will result in the body being accelerated forwards and upwards which will increase running speed' (Blazevich, A.J. 2012).
Figures 2 & 3: show the correct arm movement when in the top-speed phase; keeping in mind vigorous and quick movements to keep momentum and maxium speed and acceleration.
Figures 4 & 5: show the correct foot technique in applying a ground reaction force and extending the leg in unison with the arm so that the body remains in a linear motion.
Within determining the moment of inertia of sprint running, the athlete has to swing the leg backwards more quickly, so increasing the torque developed by the hip muscles. Therefore, getting the leg to the front of the body again requires the recovery phase from the swing phase. Also, in connection to angular momentum, it is important that the arms and legs move in unison so that the rotations in the body are cancelled and running efficiency is optimised.
Elite Sprinters drive their arms backwards vigorously but ensure they allow the recovery arm to progress forwards more or less by the product of the muscles and tendons. It is stated that 'driving the arms backwards, not forwards, is important for achieving fast running speeds' (Blazevich, A.J. 2012).
The correct sprinting technique first looks at the starting position; if the athlete can successfully achieve the starting position then they are more likely to achieve a stronger acceleration and power through the body.
Figures 6, 7 & 8: show the acceleration phase and transition phase of the sprint start. *notice the arms and legs are in motion and in unison as well as applying a force and acceleration to reach maximum velocity stage over 100m.
International and professional athlete Jenny Pacey talks to Teach Pe about her sprint start technique; Jenny Pacey explains the step by step process effectively in the video link which has also been addressed in the correct sequence below.
http://www.teachpe.com/track_and_field/sprints/sprint_start.php
- Begin in the blocks in a crouch position with the back knee on the ground and all the weight resting on the fingertips
- In the 'set' bring the hips up so that the body is in the loaded position
- Listen for the BANG and launch out of the blocks at that points. Reaction time is vital
- For the first 10 metres aim to stay low, pumping the legs hard, keeping the eyes down at the ground and accelerating powerfully
- From 20 metres bring the body to more of an upright position
- By 30 metres the athlete should be running at full speed
(Teach PE, 2013).
Also, in determining this question, it is important to use modern day technology if available to underpin an efficient and fast technique of sprinting. Using force sensors in the starting blocks and timing lights on the 100m track can be used to determine an athletes reaction and running time which can help us in improving the technique sprint. It will also determine what the athlete struggles in within the principles discussed as well correctly identifying the speed which will give a time for the athlete to improve on.
It is stated that 'the runner who improves their average running speed the most will the fastest and this can be done by improving the maximum running speed. It is for this reason that modern sprinters use a running technique at the start that allows them to attain a good technique in the top-speed phase' (Blazevich, A.J. 2012). Also, within the understandings of braking impulses, we need to reduce the braking and increase the propulsive forces when running. Figure 9 below shows the horizontal ground reaction force trace for a runner. 'A forward force exerted by the runner elicits a backward or braking reaction force, since the force is applied over time, the area under the curve (force x time) is the braking impulse. As the foot passes under the body, the runner pushes backwards to elicit a forward reaction force' (Blazevich, A.J. 2012).
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Figure 9:
(Blazevich, A.J. 2012)
Figure 10 below shows the resulting forward-directed ground reaction force applied over time which provides the propulsive impulse; therefore, this results in minimising the braking impulse and maximising the propulsive impulse are keys to a fast sprint.
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Figure 10:
(Blazevich, A.J. 2012)
Within technique, the answer lies within the arm and length during the running stride. It is understood that ‘ if our arms are extended then their moment of inertia will be greater and their angular velocity will be less even if our forces (torques) are well applied. This will also create a stronger momentum’ (Blazevich, A.J. 2012).
It is also understood that ‘many coaches attempt to improve their athlete's maximum sprint velocity by applying a resistance during sprinting so as to overload the athlete. When using a resisted sprint training device the coach can use the athlete's running velocity as an indirect measure of the overload on the athlete' (Alcaraz, P.E., Palao, J.M., Elvira, J.L.L & Linthorne, N,P. 2008).
It is also stated that ‘the greater the decrease in running velocity, the greater the overload on the athlete. Successful adaptation by the athlete to an overload is believed to allow the athlete to produce a greater force during the ground contact phase of the stride, resulting in a longer stride length and hence a greater running velocity’ (Alcaraz, P.E., Palao, J.M., Elvira, J.L.L & Linthorne, N,P. 2008).
Within technique of the arm and length during the running stride, it is stated 'if our arms are extended then their moment of inertia will be greater and their angular velocity will be less even if our forces (torques) are well applied' (Blazevich, A.J. 2012). This will also create a stronger momentum.
It is mentioned that 'in relation to supporting the answer that we need the knee to flex appropriately during the leg's recovery phase in order to decrease its inertia and increase stride frequency' (Blazevich, A.J. 2012). As the Physical Education Teacher, it will be extremely important to address these principles in relation to the question in order to maintain a successful and powerful sprint for the athlete.
The video clip below shows the acceleration phase, top-speed phase and recovery phase at a distance of around 50m. This distance was purposly conducted so that the video could show these biomechanical principles that have been discussed previously in the blog.
Although this blog is thoroughly focused on the biomechanical principles of sprint running, providing your athletes at a young age with positive feedback is an effective tool so that they can understand how to apply these principles to their sprint technique to their own individual learning.
How else we can use this information:
As a Physical Education Teacher, we can use this information in other areas of learning where children are approaching new skills or a particular sport in the later years of development. For example, in School sports days these principles can be applied in long jump where the same biomechanical principles will be applied in the run up and then a force is exerted at the jump to gain maximum projectile.
Or,
applying a longer distance of running e.g. 400m race, this will use similar biomechanical principles to apply an optimal performance; however, the top-speed phase is a longer duration as well as the recovery phase. This example would involve making changes to implement the athletes optimal performance in running.
References:
- Alcaraz,
P.E., Palao, J.M., Elvira, J.L.L & Linthorne, N.P. (2008). Effects of Three
Types of Resisted Sprint Training Devices on the Kinematics of Sprinting at
Maximum Velocity. Journal of Strength and Conditioning Research, 22(3), pp. 890-7.
- Blazevich, A.J, (2012). Sports Biomechanics the Basics,
Optimising Human Performance. Position, Velocity and Acceleration. Chapter 1,
(2nd ed.). Bedford Square, London, pp. 1-15.
- Cronin,
J. & Hansen, K.T. (2006). Resisted Sprint Training for the Acceleration
Phase of Sprinting. Strength and Conditioning Journal, 22(4), pp. 42-51,38.
- Miller,
R.H., Umberger, B.R. & Caldwell, G.E. (2012). . Limitations to maximum sprinting speed imposed by muscle
mechanical properties. Journal of Biomechanics, 45(6), pp. 1092-7.
- Teach PE (2013). Sprint Start. Video Clip. Retrieved from http://www.teachpe.com/track_and_field/sprints/sprint_start.php
Word Count: 2 250
Word Count: 2 250
