CHAPTER 19 - Program Design and Technique for Speed Flashcards
RFD (Rate of Force Development)
the development of maximal force in minimal time, typically used as an index of explosive strength
change in force by chance in time
Impulse
the product of the generated force and the time required for its production.
measure under the force-time curve
change in momentum
speed
rate at which an object covers a distance
Velocity
how fast and which direction an object is traveling
Acceleration
rate in which the velocity changes in time
Most Important Factor Of Sprinting Success
RFD
Nervous System
Strength training enhances neural drive
Increases in Neural Drive
related to increases in both muscular force production and the rate of force production
SSC (Stretch-Shortening Cycle)
Eccentric-Concentric coupling phenomenon
Criteria to improve SSC
- Skillful, multijoint movements
- Brief work bouts (Plyo + Heavy Resistance)
Spring-Mass Model
Mathematical model that depicts sprinting’s a type of human locomotion in which displacement of a body mass is the aftereffect from energy produced and is delivered through the collective coiling and extension of spring-like actions
Running Speed
Sprint speed is an interaction of stride frequency and stride length
Differences between elite and novice sprinters
- Amount of vertical force applied to the ground during the stance phase
- Greater forces must be applied in shortest time (RDF)
- Elite sprinters achieve longer stride lengths compared to novice
- Elite sprinters achieve higher stride rates
Increase in Speed
It can be achieved by increase of stride length or stride frequency, or both.
Ground Contact Time
The total time allotted for a single stance phase
Step Length
Distance between the toe and heel of two consecutive footsteps.
Example: cm between the heel of right foot and the heel of left.
Stride Length
Distance between the heel in two consecutive steps of the same foot.
Example: meters between the heel of the right foot and the heel of the next ground contact made by the right foot.
Flight time
Duration of time that an athlete is not in contact with the ground.
Stride angle
The angle at which the foot leaves the track
Monitoring Speed Development
- Ground Conctact Time
- Step Length
- Stride Length
- Stride angle
- Flight time
- Speed
- Acceleration
How long does it take for maximal contraction force to occur?
300ms
What should be emphasized when prescribing exercises to improve speed ability?
Increase in neural drive
Overload muscles in hips/knees with SSC
Braking Impulse
braking forces over certain periods of time - related to acceleration
Stance Phase
Eccentric braking period
Concentric propulsive period
Flight Phase
Recovery
Ground Preparation
START
Front leg: 90 degrees / Rear leg : 133degrees
Vertical velocity is greatest during block clearance and the subsequent two steps due to the need for appropriate rise in the body’s COG
Exit angle: 160degrees
Optimal length of touchdown of first step is 0.5m
Initial Velocity: 5m/s
ACCELERATION
Stride length is shorter in elite sprinters due to the need for less flight time so that horizontal velocity is increased through more frequent ground contact time during ACC
By ~20m, the bodys has been raised nearly upright. head is relaxed, neutral position, rising at the same rate as the torso
MAXIMUM VELOCITY
Shoulders appearing to sit directly above the hips, which sit above the foot during stance phase
Head relaxed, neutral position with the eyes focused ahead
Shoulders stay down and relaxed, leg and arms cycle together
~12.55m/s elite / 11.25m/s novice
top sprinters display higher stride at maximum velocity
Early Flight
Eccentric Hip Flexion: decelerates the backward rotation of the thigh
Eccentric Knee Extension: decelerates backward rotation of lef/foot
Midflight
Concentric hip flexion: accelerates thigh forward
Eccentric knee extension —> eccentric knee flexion
Late Flight
Concentric hip extension: rotates thigh backward in preparation for foot contact
Eccentric knee flexion: accelerates leg backward, limiting knee extesnion; stops before foot strike
Late Flight
Concentric hip extension: rotates thigh backward in preparation for foot contact
Eccentric knee flexion: accelerates leg backward, limiting knee extension; stops before foot strikes
Early Support
Continued Concentric Hip Extension: minimize the braking effect of foot strike
Brief concentric knee flexion followed by eccentric hip extension: resists the tendency of hip/ankle extension to a hyperextended knee
Eccentric plantarflexion: help absorb shock
Late Support
Eccentric hip flexion: decelerates backward thigh rotation; rotates trunk in preparation for forward takeoff
Concentric knee extension: propels COG forward
Concentric plantarflexion: aids in propulsion
Improve in COD and Agility
COD: ground contact time and ground reaction force during plant phase
Agility: perceptual-cognitive factors
Eccentric strength and maximal strength alongside the concentric explosiveness during reacceleration
Guidelines Coaching COD/Agility
Visual Focus
Body position during braking ad reacceleration
Leg Action
Arm action
Monitoring Agility Development
- Changed of direction deficit
Ground Contact time
Exit velocity
Entry velocity
Decision making time
