Lecture 6 Flashcards
How does ecitation-contraction/electro-mechanical coupling work?
- Electrical stimulus
- Electrical signal (action potential) above the threshold.
- Releases a neurotransmitter and activation f a muscle fiber action potential
- Myosin head binds to actin myofilaments and folds off => sarcomere (and muscle) shortening
What constitutes a motor unit/”functional unit”?
alpha-motor neuron (including branches/dendrites) + muscle fibers that are innervated
What is electromyography (EMG)
The study of muscle electrical signals including the development, recording and analysis of those myoelectric signals
What are the types of EMGs?
- Neurological EMG
- Kinesiological EMG
What is a neurological EMG?
Muscle response to external electrical stimulation in static conditions
What is a Kinesiological EMG?
Neuromuscular activation of muscles during postural tasks, functional movements, working conditions and treatment/training
What are the types of EMG electrodes?
Surface EMGs (sEMG)
Fine-wire or needle EMG
What are some characteristics of a surface EMG?
- Non-invasive
- Analysis of surface muscles (can’t observe deeper muscles)
- Summated action potentials
What are some characteristics of fine-wire or needle EMGs?
- Invasive
- Analysis of deeper muscles
- Analysis of single muscle (fiber) is possible
Human Biomechanics often uses surfaces EMG
What type of surface EMG (sEMG) is most commonly used in Human biomechanics?
Wireless EMG
What needs to be done to prepare for sEMG data capture?
The hair on the skin needs to be removed (only at places that sensors are placed)
Skin must be cleaned with special paste or alcohol
[This is to reduce the electrical impedance between electrode and skin surface. Also to improve signal quality]
How is the placement orientation of the electrode on the muscle determined?
Electrode placement is typically oriented along the direction of the muscle fibers
What factors can influence sEMG signal? (8 answers)
Skin preparation
Electrode placement
Environmental conditions (e.g. temp. and humidity)
Tissue characteristics
Electrode-tissue motion
Electrodes and amplifiers
Sampling frequency
Noise & artefacts
Which type of filter is commonly used for sEMG processing?
Band-pass filters
Why would you do amplitude normalisation?
- To reduce the impact of differences in physiological and anatomical characteristics of muscles and surrounding tissues
- to enable comparisons between participants , muscles, measurement sessions or electrode positions
- to enable interpretation of muscles activation (relative to a reference value)
In what fields can sEMG be used/applied? (5 A’s)
- Medical research
- Rehabilitation
- Ergonomics
- Sports science
- Biofeedback (can be used to create awareness of active/inactive muscles)
