E-Stim for Treating Muscle Flashcards
Neuromuscular electrical stimulation (NMES)
E-stim for muscle depolarization
- AP of muscle developed by electrically stimulated motor nerve is similar to that produced physiologically
- but there is a difference in order of recruitment of motor units
E-stim for muscle depolarization
voluntary muscle contraction
- progressive recruitment of small, slow motor units to large, fast motor units
E-stim process is reversed
- large diameter axons (lower resistance to current) innervate larger, fast twitch muscle fibers, fast fatiguing
-increased fatigue with E-stim vs voluntary contraction
- longer rest times needed between contractions
Factors that influence the force-frequency relation
- muscle length
- muscle temp
- fatigue state
- degree of potentiation of the muscle
Muscle contraction innervated muscle
- to excite a tissue, stimulation must be long enough, strong enough, and rise quickly enough ( shultz law)
- low frequency 1-2 stimuli per second= twitch contraction
- higher frequencies 15 pps APs will begin to summate= unfused tetanus
- at progressively higher frequencies (>30pps) a sustained contraction will occur this is caused by a succession of stimuli= tetanus
Spatial motor unit recruitment
- electrically evoked: large to small
- voluntary: small to large
temporal motor unit recruitment
- electrically evoked: synchronous
- voluntary: asynchronous
Muscle loading
- electrically evoked: against resistance
- voluntary: against resistance
Strengthening
- electrically evoked: increased motor unit recruitment, increased muscle hypertrophy
- voluntary: increased motor unit recruitment, increased muscle hypertrophy
E-stim to increase strength in healthy muscle
- stimulated contraction needs to be at least 50% of max voluntary isometric contraction (MVIC)
E-stim to increase strength in injured muscle
- stimulated contraction needs to be only 10% of MVIC
- stronger contractions will produce greater gains
Strength training via E-stim: overload theory
- the larger the load placed on a muscle the greater force of contraction the muscle will produce, thus strength will be greater than if smaller loads are applied
- applies to E-stim and voluntary muscle contractions when the same force is applied
Strength training via E-stim: Specificity theory
- E-stim stimulates large fast twitch type II muscle fibers (motor units) before small slow twitch type I muscle fibers
- should produce greater strength gains than exercise alone with the same force contractions
patient comfort dependent on
- Pt coping style
- did stimulus cause muscle contraction
- pt judging unpleasantness of stimulation
Smoothness of onset of contraction
- E-stim: rapid and more jerky onset of contraction, all motor units of a given size contract simultaneously
- physiological stimulation of muscle is smooth due to asynchronous recruitment of motor units in size as needed
E-stim to support or assist with joint positioning (study)
-E-stim reduced shoulder subluxations in pts with hemiplegia better than controls even when arm was supported
E-Stim to increase blood flow (study)
- high frequency electrical stim promoted blood flow in extremities in both healthy subjects and patients
E-stim to treat urinary incontinence secondary to pelvic flood dysfunction (study)
-Reduced stress incontinence due to transcutaneous electrical stim
Muscle contraction: denervated muscle
- does not recieve input from motor nerve
- cannot be stimulated by E-stim used for NMES
- if electrical current has a pulse duration greater than 10 ms, then muscle will contract
- continuous DC stimulation is usually used for this purpose
- contraction due to stim of muscle cell membrane and not muscle motor nerve
- muscle cell membrane does not accommodate- slow rising stimulus can be used
Muscle contraction denervated muscle study
- studied rat denervated muscle
- E-stim may retard motor nerve sprouting and regeneration
E-stim for denervated muscle today
- Bell’s palsy
- may be no better than placebo
Muscle strengthening parameters
- Pulse frequency: 35-80 pps
- Pulse duration: 150-200 us for small muscles; 200-350pps for large muscles
- amp: to >10% of MVIC in injured; >50% healthy
- on/off times ratio: 6-10 sec on, 50-120 sec off; ratio of 1:5 to start
- ramp time: @ least 2 sec
- tx time: 10-20 mins
- times/day: every 2-3 hours when awake
Muscle re-education (FES) parameters
- pulse frequency: 35-50 pps
- pulse duration: 150-200 us for small muscles; 200-350pps for large muscles
- amplitude: sufficient for functional activity
- on/off ratio: depends on activity
- ramp time: at least 2 secs
- tx time: depends on activity
Muscle spasm reduction parameters
- pulse frequency: 35-50 pps
- pulse duration: 150-200 us for small muscles; 200-350pps for large muscles
- amp: to visible contraction
- on/off ratio: 2-5 sec on, 2-5 sec off; equal on/off times
- ramp time: at least 1 sec
- tx time: 10-30 mins
- times/day: every 2-3 hours until spasm relieved
Edema reduction using muscle pump parameterss
- pulse frequency: 35-50pps
- pulse duration: 150-200 us for small muscles; 200-350pps for large muscles
- amp: to visible contraction
- on/off ratio: 2-5 secs on, 2-5 secs off; equal on/off times
- ramp time: at least 1 sec
- tx time: 30 mins
- times/day: twice daily
Russian current history
Russian physiologist – Yakov Kots
- 1977 – Russian – Canadian exchange symposium
- Revolutionary claims
- **An electrically produced human muscle contraction, using this new type of stimulation, could generate up to 30% more force then that generated by a MVC
- **Application of such current is painless
- **Short-term training could produce lasting gains in mm strength of up to 40% in healthy subjects
- 1980 – first “Russian Current Stimulator” Electro-Stim 180 produced in US and Canada
- Clinical Importance
- **If Kot’s claim is correct, could train individuals without need of voluntary contractions
Russian current: biophysical characteristics
- Time modification of continuous sine-wave having carrier frequency of 2,500 pps
- Burst modulated for fixed 10 msec periods (burst duration)
- Fixed IPI of 10 msec (interburst interval)
- Burst frequency of 50 bursts per second (bps)
Russian current: net physiological effects
- Total number of bursts/sec (burst frequency) determines magnitude of effect
- at nn/mm membrane level, each burst is treated as single pulse
- Repeated delivery of these bursts leads to motor nerve depolarization and tetanic contraction
Russian current: physiological and therapeutic effects
- Depolarize both motor and sensory neurons simultaneously
- muscle contraction will be painless
- higher current amplitudes can be used
- will stimulate deeper motor neurons
- motor unit activation
Russian current: motor unit activation
- Preferential activation of type II motor units
- if pt has motor unit deficiency during max voluntary contraction
- unable to recruit large #s of large, type II fast twitch motor units or get them to fire fast enough to develop max muscle force
- with russian stim higher current amps that are painless stimulate larger pool of type II motor units
Russian current studies
- out of at least 20 studies all subjects reported some level of discomfort
- Russian current leads to greater levels of muscle force than those obtained from MVC
- 5 studies reported lasting gains in muscle force through short-term training
- preferential activation of type II fast twitch motor units possible
- Suggested value in treating type II involved patients as seen with the elderly and when activation of both slow and fast twitch motor units is to be avoided, ie early period of bone fracture
Russian current: nerve depolarization (application considerations)
- application of biphasic and polyphasic balanced pulsed currents, both electrodes play same role due to current alternating between electrodes (NO NET CHARGE)
Russian current: electrode orientation (application cosiderations)
-Longitudinally
Russian current: monopolar electrode placement
- one electrode over target with other electrode placed some distance away over nonexcitable tissue
Russian current: bipolar electrode placement
- both electrodes over target tissue
Russian current: quadripolar electrode placement
- four electrodes over target tissue
- parallel
- crisscross
Russian current: key parameters
- current amplitude
- burst frequency
- on:off ratio
- training protocol
Russian current: current amplitude (dosimetry)
- Peak current amplitude: generally set at 100mA
- the higher the peak current amp, the higher the carrier frequency and the higher the root mean square amplitude (Arms)
- Arms=70.7% of Ap; 49.5= 70.7% of 70 mA
- the higher the (Arms) the more heat produced in tissue under electrode
- use minimal current to get desired effect
Russian current: burst frequency (dosimetry)
- 50 bps
- level where fused tetanic muscle contraction is achieved
Russian current: on/off ratio (dosimetry)
- 10:50 sec optimal for muscle strengthening
- need rest time to prevent fatigue
Russian current: duty cycle electrotherapeutics (dosimetry)
- Duty cycle= (on/ on+off)x 100
- on:off ratio of 10:50 produces a duty cycle of 16.7%
- suggest charting both
Russian current: synchronous (dosimetry)
- both channels activated at same time
Russian current: reciprocal ( dosimetry)
- both channels activated alternately
- stimulate antagonists (Ham/quads)
- ramp up/ramp down
Russian current: training protocol
- 10/10/50
- 10 contractions lasting 10 sec with 50 second rest between (original kots protocol)
Russian current stimulation indications
- post knee ligament surgery: increase myofibrilar ATPase
- post arthroscopic knee surgery:increase quad force
- anterior collateral ligament sprain: increase quad force during immobilization
Russian current contraindications
- over anterior cervical region
- over transthoracic region
- over transcranial region
- over lumbar and abdominal area of pregnant women
- over superficial metal implants
- over hemmhage area
- over neoplastic area
- over electronic implants
- over skin where sensation is severely impaired
Russian current contraindications: over anterior cervical area
- possible risk of stimulating key organs, such as vagus nerve, phrenic nerve, and carotid sinuses
Russian current contraindications: over transthoracic region
Possible risk of affecting normal heart function
Russian current contraindications: over transcranial area
Possible risk of affecting normal brain function
Russian current contraindications: over lumbar and abdominal area of pregnant women
Possible risk of affecting normal fetal growth/development
Russian current contraindications: over superficial metal implants
-Passage of electrical current may induce overheating of implants which may in turn cause unnecessary pain
Russian current contraindications: over hemorrhage area
possible risk of enhanced bleeding
Russian current contraindications: over neoplastic area
possible risk of increasing and spreading a tumor
Russian current contraindications: over electronic implants
may interfere with normal functioning of these devices
Russian current contraindications: over skin areas where sensation is severely impaired
Pt’s inability to discriminate sensation of pain during electrically evoked contraction may prevent the clinician from adequately determining the maximum safe current amp
