Motion Capture

BIOMECHANICS

T – trunk, El – elbow, SH – shoulder,

Fl – flexionEX extention

MUSCLE GROUP

X [Nm] Wojtek

Lucia Li-Ting Samuel

Andrew

FL T M 260 241

F 180

EX T M 590 504

F 420

FL SH M 145 L 143/R 133

L 93,5 /R 105

F 70

EX SH M 110 L 81 / R 76

L 93,5 / R 78,6

F 56

FL El M 90 L 92,7 / R 88,5

L 58 / R 77

F 50 L 44,2/ R 48,6

L 38,2/ R 37

EX El M 60 L 57,5 / R 59,2

F 30

The mean values of max moment of force

HAND GRIP

X [N] Wojtek

Maria Lucia Karolina

M

endurance

600 L 616 / R 639(20 sec)

F

endurance

350 L 322/ R 346

R 380

(145 sec)

R 380

(96 sec)

The mean values of hand grip

Endurance = fatigue resistance

Conclusions

To prevent from loose of your strength try to avoid extreme joint angles! (muscle will be close to its limit – see figure).

For the slow movements of large amplitudes use arm, while the fast ones of small amplitudes are best suited for the fingers!

Practice should focus on complete repetitions of the whole skill performed at submaximal speeds – improvement should occur with many repetitions, while gradually increasing speed (segmental interaction – acceleration of proximal segment (arm) -> acceleration of the distal segment appears (hand with sticks).

Listen to your body – there is a lot of signals coming from it (receptors in the skin, muscles, joints, tendons), don’t ignore them!

Muscle force vs. lenght of muscle

daily activities

Optimal length of the muscle

PROPRIOCEPTIVE SYSTEM

is responsible for collecting information about the body itself: from within the body, largely from the muscles and joints.

Muscle spindles

Golgi Tendon Organs

Skin receptors

Kopar

4 degrees of freedom

240 degrees of freedom240 degrees of freedom

Degree of freedom –movement in a plane.

Human body = a system of body links which form one or more kinematic chains.

First PHOTOGRAPHY second part of XIX century = a turning point in refers to human body movements.

Photos of running horse (1872), E. MUYBRIDGE applied the techique of sequential photography.

The next step was to take lots of pictures The next step was to take lots of pictures by means of 1 camera - by means of 1 camera - E.J.MAREYE.J.MAREY, , that initaited cinematographythat initaited cinematography..

3D registration of movement by Braune & Fisher (XIX/XX cent.)

Motion tracking or motion capture started as a photogrametric analysis tool in biomechanics research in the 1970s and 1980s, and expanded into education, training, sports and recently computer animation for cinema and video games as the technology matured.

VICON

A performer wears markers near each joint to identify the motion by the positions or angles between the markers.

passive marker

Vicon System

Vicon automatically records 3D location

of markers as points and in very precise

way determines their position in

space based on the data achieved from

2D video picture.

JOINT ANGULAR CHANGES/ MUSCLES LENGHT CHANGES

Motion capture

To register the movement - markers should be located in the essential (from animating point of view) places on the actor’s body.

 

Spatial trajectory of foot movement in the sequency of high legs techniques and stability evaluation based on COM

Archer Archer

Race walkerRace walker

Hoovering Hoovering

-> Gollum’s body - about 300 muscles.-> normal skeleton and system of the muscles;-> motion capture recordings were done - Andy was wearing

suit covered with small points. He behaved then as if he was Gollum.

Andy Serkis - Gollum

The biggest challenge was Gollum’s face. Side by side shots were shown with Andy and Gollum showing exactly the same facial expressions and speech expressions.

- Gollum is probably the most similar to the real actor digital creature, that ever appeared in the film – said Jackson - the film director.

skull caps fitted with a tiny camera

Electromyography (EMG)

EMG is a very valuable tool in measuring skeletal muscle electrical output during physical activities.

Electromyography = bioelectric activity of the muscles

Skin surface electrodes

Due to their non- invasive character in most cases surface electrodes are used in kinesiological studies.

For deeper muscles (covered by surface muscles or bones) fine-wire or needle electrodes are inevitable. A free selection of any electrode type is supported by an EMG – (pre-) amplifier. The selection of an electrode type strongly depends on the given investigation and condition.

General considerations The quality of an EMG measurement strongly depends on a

proper skin preparation and electrode positioning.

The recommendations for skin preparation: to shave the patient if the skin surface at which the electrodes

have to be placed is covered with hair. to clean the skin with alcohol and allow the alcohol to vaporise

so that the skin will be dry before the electrodes will be placed.

The Motor Unit

The smallest functional unit to describe the neural control of the muscular contraction process is called a Motor Unit.

Single motorneuron & muscle fibers it innervates

Raw EMG signal

The relationship between EMG input and force output

EMG activation is the preliminary condition for any force development and one can expect a very close relationship between both measures. Indeed, there is a very high correlation between both parameters.

Muscle Fatigue The surface EMG can also be used as measure of

muscle fatigue and recovery.

A major point of interest is the measure of muscle fatigue along with the electromyography.

The change in median frequency of power spectrum density is one of the factors that can be used as an indicator of muscle fatigue (De Luca, 1993).

Force platform =? weight scale

Ground Reaction Force

Reaction force

Force platform is used to measure ground reaction force on the base of Newton’s third law: law of

reciprocal actions.

‘to every action there is always an opposed equal

reaction’

What does it mean?

the ground is coming back up to you and supporting you with a force equal to that of gravity.