Ch 19: Sprints Flashcards
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
What causes the athlete to display non-optimal front side mechanics with regard to the height of the swing leg knee?
Inadequate force production
What causes overstriding?
A misunderstanding of application when attempting to increase speed through ground reaction times
What causes chronic hamstring injury and pain?
Insufficenct mobility and improper pelvis positioning
What causes the athlete to use a cycling motion?
Improper force application
Test that measure change of direction speed
Reactive agility tests
505
Pro agility
T-test
Tests that measure maneuverability
T-test
Illinois agility
L-run
Tests that measure perceptual-cognitive ability
Reactive agility tests
Test with shortest versus highest metabolic requirement
Shortest ( < 3 s) : reactive agility and 505
Longest ( < 12 s) : T-test, Illinois agility
How to improve change of direction ability?
Increase eccentric strength and concentric explosives
Have a low COG
Increase braking impulse and propulsive impulse
Rate Coding
Incomplete relaxations of skeletal muscles that results in more forceful contractions and larger RFD due to increases in intramuscular synchronization and increases in action potential frequencies
Technique when changing direction
- Focus on shoulders, trunk, and hips
- Look in the direction plan on changing to to assist in reorienting body
- Decrease large amounts of trunk motion leading into deceleration
- Enter and exit changes in direction with lower COG
- Avoid a stiff-legged braking style and emphasize pushing the ground away
- Have a powerful arm action to facilitate leg drive
What is dynamic strength required for?
Drills?
Base strength
Drills: body weight exercises, body awareness drills, squats and pulls, COD drills
What is concentric explosive strength required for?
Drills?
Reaccerlation after braking or maintaining strong position
Drills: Box jumps, acceleration drills, olympic lifts
What is eccentric strength required for?
Drills?
Develop ability to effectively absorb load required during braking phase
Drills: drop landing, deceleration drills,
What is reactive strength required for?
Increase the ability to transfer from high eccentric load to concentric explosiveness, olympic lifts
What is multidirectional strength required for?
Drills?
Hold body position
Drills: beginner plyometrics, loaded jumps, complex training, advanced plyometrics
What is perceptual-cognitive abilities required for?
Drills?
Scanning, anticipation, and decision making
Drills: Reaction drills
2 ways to interpret increases in flight time?
- Higher vertical forces being produced in shorter amount of time which results in proper horizontal displacement
- Producing higher forces over longer amount of time that causes unnecceasry vertical amplitude of center of mass
Exit velocity
Horizontal velocity of athlete during the initial step out of the plant phase of the COD
First step of reaccerlation from toe-off of plant foot to foot strike of other foot
Entry Velocity
Velocity of athlete prior to the plant phase
A-Skip purpose
Simulate upright sprinting mechanics and vertical force production
Fast feet purpose
Enhance stride frequency
Sprint resistance purpose
Improvements in acceleration phase
Deceleration drill purpose
Improve braking ability and assist in transfer of training from eccentric strength exercises to a more sport specific exercise
Z-drill purpose
Develop proficiency in side shuffling, accelerating out of COD, and decelerating
Y-shaped agility purpose
Incorporating perceputal-cognitive requirement in conjunction with a COD
What occurs in early flight?
Eccentric hip flexion, eccentric knee extension
What occurs in midflight?
Concentric hip flexion, eccentric knee extension
What occurs in late flight?
Concentric hip extension, eccentric knee flexion
What occurs in early support?
Concentric hip extension, concentric knee flexion, eccentric plantar flexion
What occurs in late support?
Eccentric hip flexion, concentric knee extension, concentric plantar flexion
