Chapter 4D - Teach and evaluate Speed/sprint technique Flashcards
Explain Rate of force development and impulse
Rate of force development (RFD) - an index of explosive strength, referring to the development of maximal force in the minimal time interval, while impulse is the generated force multiplied by the time required for its production.
Fundamental training objectives for increasing running speed center on the following.
- Minimizing ground contact breaking forces: this can be accomplished by maximizing the backwards velocity of the foot and leg at touch-down and by working on creating this touchdown moment with the foot firmly under the center of gravity of the body
- Emphasizing the brevity of ground support time: This helps bring about rapid stride rate, which takes explosive strength and can be improved through careful and specific plyo exercise
Prioritizing functional training of the hamstring muscles: These muscles act simultaneously as concentric hip extensors and eccentric knee flexors: as the leg swings forward, the eccentric knee flexor strength has the greatest impact on the leg’s recovery.
Track sprinters use blocks to help them accelerate by rapidly enabling a powerful push-off. What position is per degrees are their legs in and where are there hands
with the leg on the block, it’s a Flexed leg and dorsiflexed foot, to store potential energy in the series and elastic components of tendons and muscles.
Front knee is flexed about 90 degrees and the rear knee is flexed from 110-130 degrees. Hip angle varies with sprinting ability and experience. Front hip is flexed at 40 degrees in elite sprinters and 50 degrees in sub-elite sprinter. Additionally, the rear hip is at 80 degrees in elite sprinters and at 90 degrees in sub-elite sprinters.
Hands are just behind the starting line slightly wider than shoulder width apart and fingers held together. Each thumb should bridge out to the side and should be directly under each shoulder, ready to support bodyweight. Gaze is downward, with the back of the head in straight alignment.
Speed is influence by stride length and stride rate, which one moreso. How many strides per second in elite sprinters.
Speed is influenced by stride length and stride rate, so athletes should focus on quick turnover and powerful steps. Of these factors, stride rate has a greater impact on speed and should be the focus when designing programs for improving sprinting speed.
Elite sprinters can perform 5 strides per second.
As running speed approaches max for a given athlete, stride frequency increases more than stride length to contribute to speed gains.
How much does ground contact time decrease from the acceleration phase to max velocity running.
50%
The single leg support phase of running includes what eccentrically and concentrically.
Eccentric braking component and a concentric propulsion.
Explain the flight phase of running which is comprised of recovery and ground preparation. What happens to stride rate and length? forward lean, gaze and arm positions.
With the flight phase of running, stride rate and stride length typically increase over the first 15-20 meters or 8-10 strides. During this time, forward lean decreases from about a 45-degree angle to fully upright by about 20 meters. G
Gaze should be directly forward, arms forcefully pumping at the sides towards forehead to overcome inertia and increase momentum, with a lightly closed, relaxed fist or open hands.
Knees shoulder drive upwards toward chest.
Core engaged, to limit trunk rotation, support the diaphragm, and keep movement efficient.
Which leg produces a greater force initially? Which leg influence starting velocity more?
Rear leg produces the greater initial force but loses ground contact earlier. Front leg assumes a greater influence on starting velocity and exerts a force for a longer duration.
Peak initial forces can exceed 1500 N and impulses can exceed 230 newton-seconds.
