Ch 19: Sprints Flashcards
(55 cards)
Acceleration
Rate at which an object changes velocity over time
Agility
The skills and abilities needed to change direction, velocity, or mode in response to a stimulus
Force
Mass x Acceleration
Rate of Force Development
The development of max force in a minimal amount of time
Speed
Acceleration + Max velocity
Spring-Mass Model
Muscles act like spring that coils and stores energy and extends to release energy
Sprinting
An attempt to displace the body at max velocity or acceleration through strides
Impulse
The area under the force-velocity curve
Momentum
Relationship between mass and velocity
Ground Contact Time
Length of athlete’s stance phase
Velocity
Speed with a direction
Goals of sprinting
Emphasize brief ground contact times as a means of achieving a rapid stride rate
Emphasize developments of SSC to increase the amplitude of impulse
What is COD determined by?
Ability to decelerate + Ability to reorient body towards directed travel + Ability to explosively reaccelerate
How do you increase sprinting?
Increasing stride rate and/or frequency
Training effects of SSC
Acute: Increase mechanical efficiency due to elastic energy recovery
Chronic: Upregulate muscle stiffness and enhance neuromuscular activation
Acceleration phase vs max velocity phases
Acceleration: Longer ground contact times, more vertical forces
Max Velocity: Decrease in ground contact time, increases in forces
Fundamental Movements Occurring in Max-Velocity sprinting
Early flight : Eccentric hip flexion and eccentric knee extension
Mid-flight: Concentric hip flexion and eccentric knee extension
Late flight: Concentric hip extension, eccentric knee flexion
Early support: Continued concentric hip extension, brief concentric knee flexion followed by eccentric hip extension, eccentric plantar flexion
Late support: Eccentric hip flexion, concentric knee extension, concentric plantar flexion
Technique in Acceleration
Recovery of swing leg low where toes barely off ground
By 20 meters COG raised to point where nearly upright
Technique in Max Velocity
Shoulders directly above hips
Head neutral and relaxed with eyes straight ahead
Common Errors for start and acceleration with cues
- Hips to high —> space feet 1.5-2 feet and lower into start by dropping shin of back leg to be more parallel
- Stepping out laterally during initial drive —-> Push or drive through ground
- Arm movement abnormally short and tight —–> drive elbow down and back OR pull hands down and back as pulling rope with invisible line from nose to navel for either
- Unneccessary tension in dorsal muscles and neck hyperextension —-> keep head in line with spine and torso with head rising at the same rate
- Athlete “jumps” first stride or steps over knee of stance leg —–> drive through ground and let swing leg horizontally cut through the stance leg shin and keep swing leg close to the ground
- Premature upright posture —> push through the ground while maintaining a natural trunk lean and keep head in line
What causes athlete to step out laterally during the initial drive phase?
Improper distribution of forces
What causes the athlete to “jump” the first stride?
A push-off angle that is to high and an upward thrust that is to deep
What causes a premature upright posture?
Inadequate push-off force and improper carnage of head
Common errors at maximum velocity and their cues
- Attempting to maintain acceleration phase when shins vertical —> As shins and hips go vertical so should head and torso
- Not displaying optimal front side mechanics with regard to the height of the swing leg knee —> Do NOT instruct to lift knees higher as swing leg is just display of ground reaction forces
- Overstriding —> “run in lane” and maintain natural gait
- Chronic hamstring injury or pain —-> mobility and soft tissue therapy prior
- Cycling leg that causes an increased time to complete swing phase —-> drive the foot down and back and not “paw”
- Erroneous arm movement in transverse plane ——> Drive arms down and back while maintaining upright torso
