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Anatomy
Joint Sagittal plane Frontal plane
Hip Flexor : lliopsoasExtenxor : Gluteus
maximus, Hamstrings
Abductor : Gluteusmedius/minimus
Adductor : Adductorlongus/magnus
Knee Flexor : HamstringsExtenxor : Quadriceps
(Vasti+Rectus femoris)
Ankle Dorsiflexor : Tibialis anteriorPlantarflexor : Triceps surae
(gastrocnemius+soleus)
Inverter : Tibialis anterior,Tibialis posterior
Everter : Peronei
Table 8.1 Main muscle groups involved in gait
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Polyarticular Muscles
Some muscles span two or more joints.
- Energy transfer between joints- Two-joint muscles may be better at
generating shear forces at the foot than
monoarticular muscles (Hof 2001)
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Polyarticular Muscles
Action at a distanceThe instantaneous interaction of two objects which are separated in space
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Neuroanatomy
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Neuroanatomy
CNS have little capacity for repair foronce damaged, while PNS willregenerate at a rate of about 1mm/day.
UMN Lesions
- UMN syndrome(spastic paralysis) LMN Lesions
- flaccid weakness, muscle atrophy
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Excitation-contraction coupling1. Action Potential spreads
along the membrane Na+spreads into the T-Tubulesystem.
2. Na+ causes Ca++ to be
released from SR.3. Ca++ binds with Troponin
pulling Tropomyosinaway from its blocking
position over the Actinbinding site.4. Myosin forms a X-bridge
with Actin on the bindingsite.
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Fibre types
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Muscle architecture
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Dynamic electromyography
Electromyogram : summation of manyMUAPs from all the motor units active ata given time results in electrical activity.
Differential Amplifire
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Crosstalk
Detected EMG produced by neighboringmuscles or ECG
Solution : double differential technique
fine-wire electrodes
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Mortion artefact
Movement artifact noise
- Movement of electrode with respect to
the skin(induced by force transients ormovement of skin)
- This the most obstreperous noise
* Redusce by effective skin preparationand filtering
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Anti-aliasing
Nyquist theorem- The Nyquist theorem states that a signal
must be sampled at least twice as fast asthe bandwidth of the signal to accuratelyreconstruct the waveform
For EMG almost all of the signal power is locatedbetween 10 and 250 Hz and scientificrecommendations (SENIAM, ISEK) require anamplifier band setting of 10 to 500 Hz.This would result in a sampling frequency of atleast 1000 Hz (double band of EMG) or even1500 Hz to avoid signal loss.
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EMG Signal Processing
Rectification
Digital filtering - Scientific recommendations(SENIAM,ISEK) deny
any narrower band setting in the full band lengthof 10 to 500Hz
Smoothing
- Root Mean Square(RMS)
Amplitude normalization
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Footswitches
In order to determine therelationshi[ of the EMG to the gait
cycle, some means of detecting initialcontact and toe-off is required
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Factors governing the relationshipbetween EMG and muslce force
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Normative EMG
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Moment vs EMG
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Effect of fatigue
Modern PC technology makes it very easy to use Fast Fourier Transformations(FFT) to analyze and estimate the frequency contents of EMG signals.As the muscle fatigues, the mean power frequenct of median frequency of EMG falls.
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Passive connective tissue properties
- The passive force Fp of the parallel element is always present, but the amountof active tension in the contractile element at any given length is undervoluntary control
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Muscle length estimation
