Week 6 Flashcards
Movement Analysis Framework includes…
- Preparation
- Observation
- Evaluation of Performance
- Intervention
The two key elements of successful tennis stroke
- Accuracy increase (intermediate to advanced)
- Shot speed increase (high performance to professional)
Ball Speed is dictated by…
- 25% incoming ball speed
- 75% racket head speed
Determinants of Hitting Mechanics
- Elastic Energy
- Distance of Racquet Swing
- Kinetic Chain
- Linear and Angular Movement
- Equipment Selection
- Physical Development
Elastic Energy
Muscle pre-tension consisting of
1. Concentric = power
2. SSC = more power
Maintain
- Minimal pause time
- stretch magnitutde elastic yet comfortable
- speed of stretch fast
- stable base
Distance of Racquet Swing
Speed = distance / time
How to increase speed
- increased racket swing distance
- decrease time to move same distance
Kinetic Chain
more segments = more speed
more unit synchronization = more accuracy
- work from groud up
- strength and coordination to execute stroke under static and dynamic balance
Linear and Angular Movement
Trunk rotation correlated with raclet speed (open and square)
- Angular velocity
- Linear velocity
- Linear
- Angular
Equipment Selection
- racquet swing (lighter = swing faster and higher speed but less momentum to ball)
- swingweight (mass near racket tip = higher SW but is slower yet more powerful)
- head size (weight where wider faces = more resistance to long-axis twisting)
- racquet stiffness (less energy lost bending racquet)
- stringing tension (lower tension = energy storage generating high ball speed)
Physical Development
- base (good legs and base to inititate kinetic chain)
- funnel (core and cuff - energy transfer from lower body to core to upper body)
- engine (driver muscles and individual muscle contributions)
Movement Characteristics
- joint angular speeds
- movement planes
- kinetic chain optimization
qualitative analysis
- systematic observation and introspective judgement
- simple and minimal equipment
- best suited for coaching
- depends on coaching quality
quantitative analysis
- describe full/partial movement in numerical terms
- specialised equipment and performed in high performance settings
High Speed 2D Video Cameras
- easily deployable
- good camera and high frame rates
- only in one plane
- quick and effective feedback
studies serves of word class players in-competition
Radar Gun
- easily deployable and measurement for speeds
- tracks fastest moving object with quick quantitative feedback
Wearable Sensors
- inertial measurement units (IMUs)
- estimate kinematics throughout performance e.g. Xsens and Babolat Pop
Attachable Sensors (racquet)
- portable and easily deployable for large capture area
- measures number of shots, ball impact location, swing type/speed and ball speed
- real time feedback
not evaulated as gold standard
Force Platforms
- gold standard for GRF
- force magnitude and direction of force by leg drive
- lower limb contributions to kinematic chain
Electromyography
- measure muscle contractions and contributions to technique execution
- criterion standard measure for muscle activity
- assess limb contributions to kinematic chain
- not practical in competition
3D Marker-Based Motion Analysis
- criterion standard for 3D motion analysis
- record over 1000 FPS
- need controlled environment
- expensive and time consuming
3D Marker-Less Motion Analysis
- advances in computer vision tech
- multiple 2D video cameras
- used in-competition
- still needs validation
- 50/60 FPS
Features of Video Recording
- field of view
- shutter speed/exposure time
- frame rate
- depth of field
- lens distortion
How did players improve based on certain feedback?
- receiving augmented feedback such as radar gun speed
Task Modification Decomposition
e.g. ball toss only practiced with 22.5cm higher apex but can be improved with ball toss and serve improving toss trajectory
Task Modification / Exaggeration
e.g. practicing knee serve can increase racquet velocity and ball spin rate while reducing trunk twisting motion and increasing vertical velocity
Task Modification / Game Design
e.g. age appropriate changes to net size and court for children to
- play more rallies
- hit comfy heights
- use variety
- play faster
benefits of shorter racquet lengths
- lower ball compression
- improve swing mechanics (low to high and ball in front or side hits) for 8 years or younger
- reduce shoulder and elbow loading without reducing serve performance for children under ten years old
