Week 8 Flashcards
Force-velocity Spectrum
HIGH FORCE, LOW VELOCITY
- Strength
- Strength-speed
- Power
- Speed-Strength
- Speed
LOW FORCE, HIGH VELOCITY
Def: Power
- The ability to do work in a short period of time
- High rate of force development
- Speed-strength
Def: Static Power
The ability to produce power from a static position
Def: Reactive Power
The ability to produce power during a stretch-shortening cycle
Def: Power-endurance
The ability to maintain power over a prolonged period
Force-Velocity Curve
- Time on x axis
- Force on y axis
Plyometric time range
200-250 ms
Impulse
- Change in momentum
- Product of force and time
- Goal = increase rate of force development
Power in sport
- Rate of doing work, measured as the product of force and velocity
- High power outputs are required to rapidly accelerate, decelerate or achieve high velocities
- Maximal force exerted in the least amount of time
How is power produced
MECHANICAL MODEL
- Series Elastic Component (SEC) and Parallel Elastic Component (PEC
NEUROPHYSIOLOGICAL MODEL
- Potentiation through Stretch Shortening Cycle (SSC)
Mechanical Model
Elastic energy in musculotendinous units are increased with a rapid stretch and then briefly stored
- If a CON follows immediately, the stored energy is released, contributing to the total force production, if not it is released as heat
Series Elastic Component
When stretched, stores elastic energy that increases the force produced
Contractile Component
The primary source of muscle force during concentric muscle action
- Actin, myosin, cross-bridge
Parallel Elastic Component
Exerts a passive force with unstimulated muscle stretch
- Epimysium, perimysium, endomysium, and sarcolemma
Neurophysiological Model
The potentiation of the concentric muscle action by use of the stretch reflex
Stretch Reflex
The body’s involuntary response to an external stimulus that stretches the muscles
- When muscle spindles are stimulated, the stretch reflex is stimulated, sending input to the spinal cord via Type Ia afferent nerve fibers
- After synapsing with the alpha motor neurons in the spinal cord, impulses travel to agonist extrafusal fibers, causing a reflexive muscle action
Stretch-Shortening Cycle
- Employs both the energy storage of the SEC and stimulation of the stretch reflex to facilitate maximal increase in muscle recruitment over a minimal amount of time
- A fast rate of musculotendinous stretch is vital to muscle recruitment and activity resulting from the SSC
Phases of SSC
- ECC
- Stretch of the agonist
- Elastic energy is stored in the series elastic component
- Muscle spindles are stimulated - Amortization
- Pause between phases I and III
- Type Ia afferent nerves synapse with alpha motor neurons
- Alpha motor neurons transmit signals to agonist muscle group - Concentric
- Shortening of agonist muscle fibers
- Elastic energy is released from the series elastic component
- Alpha motor neurons stimulate the agonist muscle group
Power Categorization
Divided into Jumps, upper body and throws
Jumping power
- Knee, hip or ankle
- Multi or single response
- Bi-lateral or unilateral
- Plane of motion
Upper body power
- Multi-joint
- Push or pull
- Horizonal or vertical
- Bilateral or unilateral
- Stance/Position
Throwing power
Creating movement
- Rotation
- Flexion
- Extension
Individual Differences
- Innate Skills
- Nature vs Nurture
Innate Skills
Movements rehearsed over and over again until they appear effortless when performed
Nature
Some athletes benefit or suffer from the DNA and hard-wiring received via genetics from parents and relatives
Nurture
Some athletes benefits or suffer from the environment to which they are exposed during optimal windows of development
Individual differences resulting in injury
- Majority of Female and some men with lack of foot/knee/hip stability leading to valgus force on knee joints
- Females - delayed co-contraction of hamstring may lead to anterior shift of tibia relative to femur and increased risk of ACL injury
Age Related Differences
- Individuals or groups - technical coaching and safety are a priority
- Age-plyometric exercise is for all ages, but is age and strength specific
- Adolescent: Run and jump, double dutch/hopscotch
- Masters athletes: need to be aware of history of injury and pre-existing orthopedic conditions
Impact influence on intensity
Low - Water, sand
medium - grass or turf field
High - synthetic track
Factors to consider with power
- Strength Deficit
- Lower/upper limb injury
- Valgus mechanics
- Questionable surface
- Fatigue is present
- Age
- Overtraining
- Intensity
- 1-2 days recovery
- # of foot contacts too high for time of year or age
Training Strength vs Speed
SSC potentiation/ Elasticity Calculation (CMJ/SJ)
- <10% = athlete needs to train plyometrics
- >10% = athlete need to increase strength
Frequency for power training
- 1-3 sessions per week
- 48-72 hours rest between dedicated session
- dependent on intensity, fitness level, cycle of periodization
- Incorporate into warm up or complex set on a more regular basis instead of dedicated session
Intensity
Stress/impact
- Start>Finish
- 1 vs 2 foot
Amplitude
- relative
- absolute
Load
- Bodyweight
- external loading
Recovery
- 5-10 seconds between max plyometrics
- 2-4 minutes between sets
- 48-72 hours rest between dedicated sessions
Programming Plyometrics
- Plane of motion
- Speed
- Surfaces
- Progressions
- Training Considerations
- Pre-training Screen
