EXSC216 Power Testing Study - Week 10 PDF

EXSC216 Power testing 1 Type of test? High force – low velocity E.g., ??? Low force – high velocity E.g., ??? Moderate force – moderate velocity E.g., ??? 2 Validity and Reliability Vital for data interpretation Simple c...

EXSC216 Power testing 1 Type of test? High force – low velocity E.g., ??? Low force – high velocity E.g., ??? Moderate force – moderate velocity E.g., ??? 2 Validity and Reliability Vital for data interpretation Simple concepts, should be clearly understood 3 Measuring Power Power = Force x Velocity Force measurement Distance measurement Accelerometers Video analysis Timing systems 4 Force measurement Measures VGRF directly Used in research and field testing Expensive Valid and Reliable Can combine with other technology 5 Force Measurement to get Power Power = Force x Velocity [P=Fv] Force is measured directly: Force = Mass x Acceleration [F=ma] Velocity derived from Impulse/Momentum relationship Impulse = Force x ΔTime [I = Ft] Momentum = Mass x ΔVelocity [p=mv] Impulse = Momentum – the force acting on the object over time will directly influence the objects momentum 6 Linear Position Transducers Gymaware Fittech LPT 7 Linear Position Transducers Cost effective ~$2000 vs $20000 for a force plate Reliable Measure displacement directly Calculates power/force 8 Position measurement to get Power Power = Force x Velocity [P=Fv] LPT measures velocity directly: Velocity = distance / Δ time [v=d/Δt] Force [F=ma] is derived: Acceleration is calculated from velocity Acceleration = Δ velocity / Δ time [a=Δv/Δt] Mass = system mass (i.e., body mass or body mass + external load) 9 Accelerometers Push Bands, Myotest 10 Accelerometers Measures ‘proper acceleration’ not ‘coordinate acceleration’ Proper acceleration Related to gravity Coordinate acceleration Change in velocity over time Reliable Inexpensive (~$500) Calculate jump height via flight time “proprietary algorithms” 11 Optical sensors FLEX device Uses a light pulse system to determine velocity Time of Flight [ToF] method Process: Laser travels from unit (barbell) to ground (high Hz) Gets reflected back to unit (barbell) Duration of trip gives distance 12 Video Analysis / Timing Mats MyJump App / High Speed Cameras Just Jump System / OptoJump Flight-time calculation Jump Height = 9.81 * (flight time) ^ 2 / 8 13 Video Analysis / Timing Mats Reliable measure Technique may modify result Can be very cheap MyJump app = $15 Output is jump height, but can derive power 14 Various devices: 15 Perez-Castilla et al (PAP) Vertec for power? What are you measuring? Skill based test Arm swing Timing Jump Height Assessment Doesn’t relate to power well Use as an ‘outcome’ 16 Technology Summary Numerous valid and reliable options Don’t compare one method to another E.g., force plate and accelerometer Assess requirements prior to purchasing Equipment can ‘multi-task’ Testing Training Monitoring 17 Part 2 18 Types of Power Testing Power Testing Loaded Unloaded SSC or Concentric only Eccentric Utilisation Ratio Reactive Strength Index 19 Test Movements Common test movements Lower body SQJ CMJ Upper body Bench throw Concentric only bench throw Sport specific 20 Countermovement Jump Phases: Unweighting Braking Propulsive Flight Landing https://www.youtube.com/user/LocomotorLabSMU/videos 21 Countermovement Jump Protocol for a CMJ General warm up Practice jump(s) Self-selected depth Hands on hips 22 Squat Jump Phases: Propulsive Flight Landing 23 Squat Jump Protocol General warm up Practice jump(s) Often performed on the force plate Self-selected depth Some conjecture in the literature Hands on hips *Small amplitude countermovement* Small Amplitude Countermovement Can be defined as a 10% unweighting Can be determined by software (e.g., ForceDecks = >20N unweighting) Suggests SSC contribution 25 CMJ Curves 4000 3.00000 3500 3000 2500 2.00000 2000 1500 1000 500 1.00000 0 ‐500 ‐1000 0.00000 ‐1500 ‐2000 ‐2500 ‐3000 ‐1.00000 ‐3500 ‐4000 ‐4500 ‐2.00000 ‐5000 ‐5500 ‐6000 ‐6500 ‐3.00000 Force Power Velocity Displacement 26 Variables Power Peak & Mean Force Peak & Mean Velocity Peak Impulse Rate of Force Development Jump Height 27 Variables cont… 28 Reliability Sheppard & Cormack et al 2008 29  Half Post 2h 24 h 48 h 72 h 96 h Max voluntary contraction ↓ ↓ ↓ ↓ ‐ ‐ ‐ % Voluntary activation ↓ ↓ ↓ ? ↓ ? ↓ Potentiated twitch ↓ ↓ ↑ ↓ ? ? ↑ Iso mid-thigh pull (N.kg-1) ↓ ↓ ↓ ↓ ‐ ? ? Countermovement jump (cm) ‐ ‐ ‐ ↓ ‐ ‐ ‐ Squat jump (cm) ↓ ↓ ↓ ↓ ↓ ↓ ‐ Creatine kinase ↑ ↑ ↑ ↑ ↑ ↓ Testosterone ↑ ↓ ? ? ? ? Cortisol ↑ ↓ ↓ ↓ ↓ ↓ T:C Ratio ? ? ? ? ? ↑ Uric Acid ↑ ↑ ↑ ↑ ? ‐ Tofari et al., (2018) 30 Part 3 31 Strength & Power and Performance OPTIMAL 32 Harris et al 2006 Bench Throw in Soccer Players Jandacha et al 2011 33 SQJ & CMJ Cormie et al 2001 34 Cycling power Optimal power relationship Important for gear selection Track cycling 35 Cycling Track sprint High peak power > 2000 W Sustained power for short periods Road cycling High average power Key components Hill climb End of stage race Avg during time trial 36 Discriminator of Performance Starters v Non – Starters Elite v Sub-Elite 37 Part 4 38 Eccentric Utilisation Ratio Ratio of CMJ to SQJ (i.e. CMJ/SQJ) Power Height Indication of ability to utilise SSC Sensitive to changes in training Help direct program design 39 Eccentric Utilisation Ratio 40 Reactive Strength Index Maximal height/ground contact time Flanagan et al 2008 41 Training to Improve Power Harris et al 2006 42 Training Strategies High force-Low velocity training ↑ max strength Low force-High velocity training ↑ speed of contraction Load that maximises mechanical power Strength dependant Exercise dependant In Rugby League - ~55% 1RM Training loads may need to be lower (~30-45% 1RM) Other studies suggest Pmax at Body weight 43 Reporting Results If you’re interested in working at the top level Consider your audience Needs to understood by athletes & coaches Many levels of comparison are valuable Pre v post training phase Year to year Squad/position Other norms/targets Charts 2.5 2 1.5 Std. Dev From Target 1 20m Shuttle Run Yo‐Yo IR2 0.5 6 x 30 m Sprint 0 ‐0.5 ‐1 Capacity 45 Tables Use of statistics to determine change Simple interpretation Coupled with clear reporting for coaches 46 Type of test? High force – low velocity E.g., ??? Low force – high velocity E.g., ??? Moderate force – moderate velocity E.g., ??? We should be clear on these now. 47