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The need for SPEED Sprinting is a basic requirement for many athletics events. Ron Parker summarises the basics of the discipline SPRINT speed is all about power. The greater the power applied on each stride, the greater will be the acceleration and, subsequently, the faster the final speed will be. But how is that power applied? There are three phases in a sprint race – the start, the acceleration phase and the speed maintenance phase.
► The start
The objective in the sprint start is to generate as much force as possible as quickly as possible, backwards and downwards against the starting blocks to propel the athlete away from the starting line. The sprinter does not really run out of the blocks. The action is more of a “leap” out of the blocks. The biomechanics of the sprint start are fairly simple:
1 Move the arms first. The arms are
shorter and lighter than the legs and therefore can be moved faster. 2 Opposite limbs move in opposition to each other. During the sprinting action, if the right arm moves forward, the right leg will move backwards. Similarly, if the left arm moves down, the right leg moves down. 3 Use as many muscles as possible to generate accelerative force. Drive back against the blocks with both legs (Leap out of the blocks.) As the back foot leaves the blocks, the front leg continues to extend, producing force against the blocks. The reactive force against the blocks begins the acceleration away from the starting line. Therefore, the greater the force that can be exerted against the blocks, the greater will be the acceleration away from the blocks.
As many muscles as possible must be used
to create as much acceleration as possible. This includes the back
extensors as The sprinter’s back straightens to add even greater force against the blocks in the start. Note that, if the head is forced down, keeping the back curved, there will be less force exerted against the blocks in the start.
► Acceleration Acceleration is greatest at the start and decreases as speed increases. At maximum speed, the sprinter ceases to accelerate. During the acceleration phase: 1 The body lean of the sprinter decreases as the speed of the sprinter increases. 2 The lifting action of the knees (with respect to the torso) also decreases as speed increases.
3 The magnitude of the range of motion
of the arms also decreases 4 Hip flexion increases as the speed of the sprinter increases until maximum speed is reached.
► Speed maintenance Cadence, or rate of stride action, is the most important component of maintaining maximum sprinting velocity. The length of the stride is the second most important component of maintaining maximum sprinting velocity. In short, it can be explained by the formula velocity = distance (stride length)/time. Cadence can be expressed as the number of strides per second. Speed (velocity) is equal to cadence times stride length and is expressed in metres per second. The fastest sprinters in the world achieve speeds in excess of 12 metres per second. The knees, rather than being lifted in each stride, are pulled forward into sprinting position using the hip flexors. This pulling action is so fast that, as the foot of the front leg strikes the track under the body of the sprinter, the knee of the back leg is even with and passing the knee of the front leg. Also, this pulling action occurs so fast that the knee of the leg pushing off does not fully extend for 100m and 200m races as it does in races of 400m and longer. At maximum speed, the flexion of the supporting leg is minimal (staying tall). If the supporting leg flexes too much, the duration of the support phase increases and the speed of the sprinter decreases. To maintain maximum speed, not only is the ankle extended, but the toes are actually thrust backwards against the track.
► The sprint stride
► The thrust phase
► The recovery phase
► The support phase
► Arm action At the maximum rearward position at the end of the thrust phase, the arm should be extended no more than 90 degrees. At the maximum forward position, again at the end of the thrust phase (opposite arm), the arm should bend no less than 50 degrees. The hand should reach the centre line of the body (viewed from the front) in the maximum forward position. While the arm is moving rearward during the support phase, it should extend no more than 110 degrees. In order for the arm action to be at maximal speed, the hands should be held in a relaxed, cupped position with the palm of the hand facing inward. The fingers of the hands should not be extended as it will tighten the muscles in the arms.
► Sprint training The sprinter, in training, must both increase the number and strength of fast-twitch muscle fibres and also increase the speed of firing of these muscle fibres. To increase the strength and number of fast-twitch muscle fibres, the sprinter must do resistance training:
To increase the speed of firing (neural system) of these fast-twitch muscle fibres, the sprinter can:
To increase the capacity of the phosphagen energy system to enable rapid muscle firing, the sprinter can do sprint training using short sprints (20m to 40m) with full three-minute static rest intervals. The sprinters must also increase their speed endurance to be able to maintain speed after five seconds by: Training the glycolitic power energy system with interval training of repeated sprints with a 1:6 to 1:4 work:rest ratio (100m to 200m races) with walk/jog rests. Training the glycoltic capacity energy system with interval training of repeated long sprints with a 1:3 to 1:2 work:rest ratio (400m race) with walk/jog rests. Not to be overlooked, flexibility is an important component in all athletics events and should be an integral part of sprint training so that the sprinter can move effortlessly through a full range of motion. A properly planned training programme should cover all areas of training: skill, strength, stamina, flexibility, nutrition, recovery strategies and mental training.
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