Measurement of Voluntary Muscle Action Flashcards
What can we attain from sEMG studies?
- On/Off (consider onset thresholds)
- Timing of excitation but consider delays
- Relative Muscle Excitation
What neural factors influence force generation?
- Number of factors activated (recruitment)
- Size of activated motor neurons
- Rate of action potential discharge (rate coding)
What is the the full waveform of a muscle contraction called?
Muscle action potential (MAP)
What is the summation of MAPs called?
Motor unit action potential (MUAP)
What is a repetitive train of MAPs called?
Motor unit action potential train (MUAPT)
What was the hamstring electromechanical delay compared to quads?
95% greater
Why does analysed signal not reflect original firing characteristics?
Skin acts as a low pass filter
Why is it impossible to record single action potentials?
- Muscle fibres overlap
- We can measure MUAP using invasive measures
Name 5 physiological causative intrinsic EMG factors
- Blood flow
- Number of active MUs
- MU firing rate
- Fibre type
- Metabolic factors
Name 3 anatomical causative intrinsic EMG factors
- Fibre diameter
- Depth & location of fibres
- Subcutaneous tissue
Name extrinsic controllable EMG factors
- Impedance
- Orientation of electrodes
- Location of electrodes
- Reference electrode
How can we manipulate neural factors during training?
- Cadence
- Intensity
- Rep range
What is a key EMG consideration? and why?
- Movement velocity as different speeds leads to different fibre activation
What is usual cross talk range and how is it detected? and reduced?
- 3-10% but up to 17%
- Cross-correlation
- Double differential
What does fatigue do to EMG and why?
- Compression of spectrum to lower freq.
- Fatigue of higher threshold MU’s
- Decreased conduction velocity – metabolite accumulation
- MU synchronisation
