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Science of Motion Captuer

Motion Capture

Definition: Recording of motion for immediate or delayed analysis and playback.
Developed to record animal and human locomotion.
- Still photography
- Video to High speed
- Motion capture marker systems.

2D STANDARD VIDEO:

PAL 50 hz (25 frames per second)
NTSC 60 hz (30 frames per second)

Standard video limitations:

- capturing of fast or critical events in movement often require faster capture rate of 25 frames (50hz).
- Human movement occurs in 3 planes.
- Cannot make decisions about motion from one view.
- cannot measure rotational movements.

3D Motion Analysis:

VICON Motion Analysis System:
- 2 or more cameras to reconstruct image into 3D.

Used by:
- Sports biomechanists
- Clinical Biomechanists
( Cereberal palsy, ACL injuries, osteoarthritis, amputees)
- Animal biologists
- Industry
- Film, TV & animation

Projectile Motion

Projectile Motion:

Projectile motion: form of linear kinematics (curvilinear), shows changes in velocity and acceleration are going to occur once the object leaves the ground, hand, foot etc.
Linear motion that here are X & Y components, vertical and horizontal components.

Gravity:

Gravity results in constant vertical acceleration which is 9.8 m/s/s.
this does not affect horizontal velocity. Gravity and air resistance act on an object in air (air resistance is negligible).

Projectile Horizontal velocity component:

Horizontal velocity is constant (you end with what you start with).
Gravity plays no role in horizontal motion (ie. no acceleration)
Only displacement, velocity and time are the variables in horizontal velocity.
Acceleration only works vertically (ie. gravity -9.8m/s/s)

Projectile Vertical Velocity Component:

Vertical factor decreases as ball goes up and increases with ball coming down.
vertical velocity = 0 at peak.
The horizontal velocity remains that same (ignoring air resistance and no gravity/acceleration).
Vf (peak) = 0
time it takes for the ball to go up and down is the same as the time it takes for the ball to fly to the other side.
(Time of ball up and down = time of flight)


Projectile Vertical Velocity Component: 

Above diagram shows that there is no change in horizontal velocity.
There is an increase in vertical velocity as the ball comes down because it is affected by gravity/acceleration (-9.8m/s/s).
vertical component decreases as the bal goes up and increases as it comes down.
the gravity parabola occurs.

Key Concepts:

A projectile is any object upon which the only force is gravity.
Projectiles travel with a parabolic trajectory due to the influence of gravity.
There are no horizontal forces acting upon projectiles and thus no horizontal acceleration.
The horizontal velocity of  projectile is constant (a never changing in value).
There is a vertical acceleration caused by gravity, its value is 9.8m/s/s, down (negative).
The vertical velocity of a projectile changes by 9.8 m/s each second.
The horizontal motion of a projectile is independent of its vertical motion.
Centre of mass (CM) of projectile will travel in a parabolic path - regardless of the motion of the individual body segments.
Vertical velocity at the peak of the projectile's flight will b exactly zero.
Total Time up = Total time down (for same release and landing)

Factors influencing trajectory:

Release velocity.
Release angle.
Release height.

* air resistance is ignored.

Three factors (velocity, height, angle) determines how fast, high, long and far a projectile travels.


Release Velocity:

Most important factor in projectile motion.
Increase in speed of release (release velocity) increases two release parameters.
Increase in Vh increases distance Sh = Vh x t total.
Increase in Vv increases time of flight t total = 2 x Vv/g


Release Height:

Height only affects the time down.
Only a portion of one parameter is affected:
t total = t up + t down  - only t down is affected.

Release Angle:

Determines shape of trajectory. Trade off between Vv & Vh.
If 0 degrees = latter half of parabola. (if above landing height)

Release angle, height and speed interactions:

For any constant height: increase in speed results in optimum angle approaching 45 degrees.

For any constant speed, increase in release height results in decrease in optimum angle.

Velocity is Important! 

Theoretical Vs Optimal angles in Long Jump

Conversion of Vh to Vv

Running Sumersalt: Maintains the horizontal velocity while developing vertical velocity.

General Principles in throwing and hitting

Basketball and high jump.
Theory is 60 degrees but a practical angle is 50 degrees.


Basketball:

Velocity is the best variable to change for best results.

Equations of constant acceleration:

Outcomes:

Problems:

A baseball ball leaves the bat at 32.6m/s at an angle of 54 degrees. If the boundary fence is 8m from impact will the ball clear the fence?

Angular Kinematics

Angular Kinematics

Describing angular motion or displacement?

Angular Distance and Displacement:

Units of measurement: radians (1 rad=57,3 degrees), degree, revolutions (revs)

Angular Velocity ( w ) - Time rate of change of angular displacement (rad/s, deg/s, rev/s)
Linear velocity = change in displacement over time.
Angular velocity = change in angle over time.

Angular Acceleration:

Linear acceleration = a = change in velocity over time.
Angular equivalent = a = change in angular velocity over time.

Linear Velocity Endpoint (Implement) = Angular Velocity (w) x Radius of Rotation (r)
* Must only work in radians.

Object's COM which has a linear velocity it must be added to the equation.
Vball = V shoulder + (W x r)

Lecture Outcomes:

- Vball = Vankle + (W (angular velocity) x r (radius of rotation))

Real World Problem:
A Softballer rotates the bat horizontally at 10rad/s. If her shoulder is moving forward at 2m/s and the distance of the point of impact with the ball and her shoulder is 1m, what is the forward velocity of the end of the bat at the point of impact?

Equation that needs to be used:
Vball = Vshoulder + (W x r)
Vball = 2 + (10 x 1)
- Vshoulder = expressed in linear velocity (m/s)
- W = is angular velocity
- r = the shoulder radius of rotation

* Vball = 12m/s

Muscles of the Foot and Ankle

Dorsal Venous arch:
Gives rise to saphenous vein medially and
gives rise to lesser saphenous vein laterally.

The saphenous vein is located in front of the medial malleoli.

Deep Fascia of the dorsum of the Foot

Deep Fascia of the dorsum of the foot is continuous with the fascia cruris via extensor retinacula.
Deep fascia blends in with the plantar fascia medially and laterally.
Deep fascia is the roof of the first fascial space of the dorsum of the foot.
Three layers on dorsum of the foot.

First layer of the dorsum of the foot

First layer lies between the superficial part of the dorsalis pedis.
Contains AT, EHL, EDL and Peroneus tertius.
All these tendons are in synovial sheaths which are three in number.
AT and EHL have seperate tendon sheaths and EDL & Peroneus Tertius have their own.

click above for full image.

click above for full image.

click above for full image.

2nd Layer of the dorsum of the foot

Contains one intrinsic muscle of the foot Extensor digitorum brevis and fascial coverings.
Fascial coverings are the deep layer of the dorsalis pedis fascia.
Extensor digitorum Brevis from the anterior aspect of the dorsum of the calcaneus divides into four tendons and passes into medial 4 toes.
* There is no extensor digitorum brevis on the 5th toe.


Extensor Digitorum Brevis:

Origin: Superior aspect of the calcaneus anterior to the sinus tarsai, partially from the interosseous talocalcaneal ligament.
Insertion: splits into 4 slips, most medial one the EHB inserts on the dorsal aspect of the base of the proximal phalanx of the hallux, other 4 slips on the lateral side of the EDL (extensor digitorum longus) of 2nd, 3rd and 4th toes - contributes to extensor expansion.
Action: Extend phalanges of 2nd/3rd/4th toes, helps with MPJ (metatarsophalangeal joints) extension.
Nerve: Deep peroneal nerve, lateral branch; dorsalis pedis artery via lateral branch.

Layers of the Foot:

 

 

Compartments of the plantar surface of the foot:

Dorsally there are 3 compartments.
Plantarly there are 4 compartments.
The dorsal and plantar compartments are seperated by:
dorsal interossei, aponeurosis and metatarsals.

Medial compartments: abd. hallucis, FHB, FHL (flexor hallucis brevis and flexor hallucis longus)

Central Compartment: Flexor digitorum brevis, flexor accessorius, adductor hallucis.

Lateral compartment: Abductor digiti minimi, flexor digiti minimi brevis.

Interosseus compartment.

First Layer Muscles:
Abductor hallucis, flexor digitorum brevis and abductor digiti minimi.

Abudctor Hallucis:
Origin: medial process of calcaneal tuberosity, flexor retinaculum, medial intermuscular septum.

Insertion: medial plantar aspect of the proximal phalanx of the hallux.

Action: abducts and plantarflexes toes.

Nerve: medial plantar nerve and artery.

Flexor Digitorum Brevis:
Origin: medial process of the calcaneal tuberosity, medial and lateral intermuscular septa.

Insertion: middle phalanges of the toes (except for the hallux)

Action: Flexes toes at PIPJ and MPJ

Nerve: medial plantar artery and nerve.

Abductor digiti minimi:

Origin: Lateral process of calcaneal tuberosity.
Insertion: lateral plantar aspect of the proximal phalange of the 5th toe.
Action: Abduct and flex fifth toe.
Nerve: Lateral plantar nerve and artery.

 

To be continued...

Anatomy of Foot and Ankle

Tibial Tuberosity:

 Important for tendons and a useful surface landmark.


Head of Fibula:

Easily palpated because of the subcutaneous on the posterolateral aspect of the knee.
Division of the common peroneal nerve occurs here.

Lateral Malleolus:

 

Medial Malleolus:

 

Calcaneus:

 

Styloid Process:

can be palpated in the middle of the lateral border of the foot.

Ankle Joint:

Felt between the tendons as a depression at level 1.5cm superior to the tip of the medial malleolus.

Navicular:

Visible/palpable. Anteroinferior to the medial malleolus.

Arterial Supply

Anterior tibial Artery: Supplies the anterior compartment muscles of the leg.

Posterior tibial artery: supplies the posterior compartment muscles of the leg.

Peroneal artery: supplies the lateral compartment muscles of the leg.

The femoral artery becomes the popliteal artery divides into posterior, anterior tibial and peroneal arteries.

 

Pedal Pulses:

 

Dorsalis Pedis Pulse: 1 finger lateral to the exntesor hallucis longus.

Posterior tibial pulse: between medial malleolus and the cancaneal tendon.

Venous Supply:

Nerve Supply:

Tibial Nerve - supplies posterior compartment muscles.

Deep peroneal Nerve - supplies anterior compartment muscles.

Superficial peroneal Nerve - innervates lateral compartment muscles.

Tibial Nerve bifurcates at the level of the medial malleolus.

MUSCLES:

Anterior Group Muscles:

Actions: Dorsiflexes foot (tibialis anterior also inverts, Peroneus tertius also everts, Extensor digitorum longus & Extensor hallucis longus extends the toes)

Blood Supply: Anterior tibialis Artery

Innervation: Deep peroneal Nerve

Lateral Group:

Actions: Everts foot (weak plantarflexion)

Blood Supply; Peroneal Artery

Nerve Innervation: Superficial peroneal Nerve.

Posterior Group:

Actions: Plantarflex (weak inversion) foot.

Arteries: Post tibial Artery

Nerve: tibial nerve.

The posterios muscles include the achilies (gastric and soleus), superficial (gastric and soleus), deep (flexor hallucis digitorum/tibialis posterior), deltoid ligament (Connects tibia, calcaneus and talus)

Medial Ligaments:

Medial/deltoid ligament is strong, it attaches to the medial malleolus and base to the tarsus. Divided into 4 parts: tibionavicular, tibiocalcaneal, posterior tibiotalar, anterior tibiotalar. 

Lateral Ligaments:

3 Ligaments that attach lateral malleolus to the tarsus:

Anterior talofibular, posterior talofibular and calcaneofibular.