NMES
The application of an electrical current (usually over the motor point) to elicit a muscle contraction
General uses of NMES
Muscle reeducation/strengthening Increasing Joint ROM Improving Function (stance/hand grip)
Muscle Adaptations to NMES
Increases in Strength
increased content of muscle contractile proteins
Increases in Endurance
-increase in amount on enzymes used in aerobic pathways
-increased mitochondrial size and number
-increase capillary density
Can electrical stimulation really help to increase muscle mass in healthy people?
Is it as effective as weight-training?
Not in healthy people that are 5/5 will have to increase it too much.
Why NMES versus voluntary contraction
- Reflex Inhibition
- Selective contraction of one muscle (eg. middle deltoid, VMO)
- Muscle reeducation
- Compliance with HEP (home exercise program)
- Strength less than 3+/5 (can get a stronger contraction with e-stem and build strength of contraction)
- Form/Adjunctive of Biofeedback
- when contracting with stim may increase total fiber recruitment
Reflex Inhibition
Reflex Inhibition (RI): stimulation in which sensory stimuli impede the voluntary action of the muscle
- -Major causes of quadriceps RI are pain, joint effusion, immobilization and trauma.
- –Pain is the most commonly described cause of quadriceps RI
Measurement methods: direct measurement via EMG, muscle biopsy, girth measurements
- –EMG is the most common, useful tool for investigating RI.
- –Based on EMG studies of RI, vastus medialis is most commonly affected in the quadriceps group.
Disuse Atrophy
- Refers to changes in the muscle after a period of immobilization or reduced activity.
- Most obvious change is a decrease in crosssectional area.
- Type I fibers affected to a greater degree
Optimization of NMES
How do we get the best contraction with the greatest amount of force, while minimizing discomfort?
with the greatest amount of force, while minimizing discomfort.
Location of Motor Point
- Apply gel to skin
- Apply electrode with firm contact to the general location of the motor point (may use 1hz)
- With the unit on, move electrode around until a good contraction is achieved.
- Use an indelible marking pen to draw a circle around the electrode; this allows the electrode to be placed in the same area.
- Optimization of NMES waveform
- Waveform
- -control is not always possible
- -symmetrical biphasic has shown some evidence of being the most comfortable with other parameters held constant
- -Biphasic tends to be preferred by most individuals over monophasic
Typical Patient preference
Symm Biphasic (low frequency> Russian) >asym biphasic> Hi volt pulsed DC
Russian Current
Compared the effects of low frequency biphasic current and “Russian” current on isometric muscular torque production of knee extensors as recorded by Biodex
Conclusions: There is no difference in the effectiveness of low frequency biphasic and Russian Currents when they are used to elicit forceful muscular contractions.
In each burst there are
CHART!
there are 25 cycles(per 10 milliseconds)
Carrier frequency there are 2500 hz/2500 cycles per sec if not interrupted…because 50% it is really only 1250 hz delivered per sec.
Compared the effects of 2500 HZ, 3750HZ, and 5000Hz on Quadriceps torque
Conclusions: 2500 Hz produced significantly greater torque tan 3750 or 5000Hz
Optimization of NMES
2. pulse duration
- Pulse Duration
- -control is not always possible (may be fixed in portable NMES devices, and is fixed in HVPDC(fixed 150) and russian)
- -Portable devices are fixed at 300-400msec
- -100-600 usec generally used for a strong contraction while minimizing pain
- -keep as low as possible to minimize chance of stimulating A delta’s
3.Optimization of NMES–Frequency
- almost always can control this
- typically a strong, tetanic contraction can be achieved between 30-50 pps. Greater than this may cause undue fatigue
- for Russian, this means 30-50 BURSTS/second (bps)
4.Optimization of NMES CYCLE time
Cycle Time
-limited choices
-for muscle strengthening 1:3-1:5 ratio (eg, 10 on 30 off)
For muscle Endurance 1:1 -1:2 ratio (eg 10 on 10 off)
Cycle Time
Considerations for adjusting this:
Purpose of stimulation(endurance, strengthening, muscle re-education, etc.)
Degree of atrophy
Individual responses
5.Ramp Optimization
Limited choices
sometimes built in
may or may not be built in to on/off time
increased ramp=increased comfort
6.Electrode/Size Placement
Optimization of NEMS
The larger the electrode, the greater the comfort
Electrodes that are too large may stimulate unwanted muscles, too small may be painful
The closer to the motor point the greater the comfort
When, How long
2X/week-daily depending upon strength of contraction
10-20 minutes common
NMES post total Knee Aethroplasty
Purpose:
Examined the effect of adding high intensity NMES to a volitional strengthening program following TKA
Methods: 8 pts with bilateral TKA’s
Treatments: 3 times per week for 6 wks
2 intervention groups
1)exercise legs group –bilateral voluntary exercise programs for strengthening
2)NMES LEGS group-assignments were split
a)stronger leg at initial evaluation participated in a voluntarty exercise program
b) the weaker leg received NMES in addition to the voluntary exercise program
TKA cont.
Intervention:
NMES group
10 sec, isometric contractions with 80 sec rest between contractions
-10 NMES quadriceps contractions added to each treatment session
CONCLUSION:
1. the case series does support the use of NMES to improve quadriceps strength gains following TKA surgery
2. Gains were observed during the first 3 weeks of NMES treatment that led to an increase in voluntary muscle activation
3. With the use of NMES, deficits in quadriceps strength and activation resolved quickly, and the results were maintained over a 6 moth follow-up period.
–these gains were observed in the NMES “weaker leg” group
–The “weaker leg” surpassed the strength of the contralateral “stronger” leg
4. Larger sample sizes are needed as well as the examination of carry-over quadriceps with strength gains with the use of NMES/
