31. List electrically excitable and nonexcitable tissues.
Excitable Tissues Nonexcitable Tissues
Abdominal organ cells Bone
Autonomic motor fibers Blood cells
Cardiac muscle fibers Cartilage
Cells that produce glandular secretion Collagen
Nerve axons of all types Extracellular fluid
Nerve cells of all types Ligaments
Voluntary motor fibers Tendon
32. Discuss Pflüger’s law and its implications in the stimulation of human tissues.
According to Pflüger’s law, healthy muscle contracts with less current if stimulated by the cathode compared with stimulation by the anode. When stimulating a muscle with a direct current, the cathode should be the active electrode because the amount of current required to acquire a muscle contraction is less with the active cathode than with the anode:
CCC > ACC > AOC > COC
where CCC = cathode closing current, ACC = anode closing current, AOC = anode opening current, COC = cathode opening current, closing = starting the current, and opening = stopping the current.
33. What is accommodation?
Accommodation is the increased threshold of excitable tissue when a slowly rising stimulus is used.
Both nerve and muscle tissues are capable of accommodating to an electrical stimulus; nerve tissue accommodates more rapidly than muscle tissue. Understanding the process of accommodation is
Closing Opening COC
ACC AOC
CCC
important when stimulating healthy muscle by the motor axon because the electrical stimulus must be applied somewhat rapidly to avoid accommodation.
34. What is the strength-duration curve?
The strength-duration curve describes the relationship between the strength of the stimulus (intensity) and the duration of the stimulus (on time) required to reach a specified level of activation.
By varying the intensity and duration of an electrical stimulus, it is possible to plot a strength- duration curve. The strength-duration curve gives a graphic representation of the excitability of nerve and muscle tissues. Although the strength-duration curves are comparable for healthy nerve and muscle tissues, they are different from denervated nerve and muscle tissues. As a result, we are clinically able to stimulate healthy, innervated muscles with a stimulus of adequate amplitude and of short duration. It also is shown by this curve that greater amplitudes of stimulus and longer durations are necessary to stimulate denervated muscles effectively.
35. What are identified contraindications and precautions for electrotherapy application?
CONTRAINDICATIONS (ABSOLUTE AND RELATIVE)
• Cardiac pacemaker of synchronous or demand type
• Patients prone to seizures
• Placement of electrodes across or around the heart
• Placement of electrodes over a pregnant uterus, especially during the first trimester (this is controversial, and delivery itself presents with relative precautions)
• Placement of electrodes over an area suspected of arterial or venous thrombosis or thrombophlebitis
• Placement of electrodes over the pharyngeal area
• Placement of electrodes over protruding metal
• Placement of electrodes over the carotid sinus PRECAUTIONS
• Allergies to tapes and gels
• Areas of absent or decreased sensation
• Electrically sensitive patients
• Patients with advanced cardiac disease
• Patients with severe hypotension or hypertension
• Placement of the electrode over area with significant adipose tissue
• Placement of the electrode over damaged skin (with the exception of tissue healing protocols)
• Placement of the electrode over or near the stellate ganglion
• Placement of the electrode over the temporal and orbital region
• Patients who are unable to communicate clearly TEST
Chronaxie < 1 msec Strength
Duration Curve Reaction of de- generation Nerve Conduction
40 to 60 m/sec
No conduction after 3 days
No conduction
Conduction increses
WNL AC = DC DC > AC DC only AC begins AC = DC
begins to rise 30 to 50 msec begins to decrease approaches normal NORMAL DENERVATING DENERVATED REINNERVATING REINNERVATED
36. Electrical stimulation has been reported in the literature to be useful in what conditions?
• Edema management
• Endurance training
• Improvement of muscle contractures
• Maintaining and improving range of motion
• Management of spasticity and spasm
• Muscle strengthening
• Neuromuscular facilitation and reeducation
• Orthotic substitution
37. Is there a difference between use of NMES or voluntary exercise or use of combined NMES and voluntary exercise in terms of muscle strength?
Yes. Recent evidence suggests that NMES combined with voluntary exercise may accelerate gains in quadriceps muscle strength and activation greater than voluntary exercise alone following total knee arthroplasty. For example, Stevens and colleagues showed that the addition of ten 10-second NMES-elicited quadriceps contractions to treatment sessions significantly improved quadriceps strength, with the most dramatic improvement noted in the first 3 weeks of treatment.
38. Outline an appropriate protocol for neuromuscular facilitation and reeducation including purpose, rationale, indications, parameters, and special consider- ations.
1. Purpose—To barrage the central nervous system (CNS) with appropriate sensory information 2. Rationale—By supplying the proper sensory input of what a muscle contraction or limb movement feels like and visual information about the appearance of the action, electrical stimulation can enhance a motor response. It also may prevent decreases in muscle oxidative capacity and provide an artificial drive to inactive synapses in some circumstances.
3. Indications—Any patient for whom a motor- and sensory-augmented muscle response would assist in better performance of his or her own voluntary actions
4. Parameters—Pulse duration, 100 to 200 msec; pulse rate, 35 to 50 Hz; intensity, to a tolerable motor level up to 3+/5; ramp, 1 to 3 sec up/down; on/off, 1:1 ratio set or hand-held switch;
treatment time, 5 to 30 min, 1 to 3 times/day, 3 to 7 days/week, 1 to 2 weeks; polarity, not applicable 5. Special considerations—Facilitation and reeducation require active participation by the patient
and may be limited by patient tolerance, cooperation, and attention span.
39. When is NMES indicated after knee surgery and immobilization?
• Prevention of muscle atrophy associated with prolonged immobilization
• Prevention of decreases in muscle strength
• Prevention of decreases in muscle mass
• Prevention of decreases in muscle oxidative capacity
40. Is there a difference between the use of high-intensity electrical stimulators and low-intensity or battery-powered stimulators with regard to quadriceps femoris muscle force production in the early phases of anterior cruciate ligament (ACL) rehabilitation?
Yes. Studies support the use of high-intensity electrical stimulation but do not consistently support the use of low-intensity or battery-powered stimulators when the desired objective is the recovery
of quadriceps femoris muscle force production. A study by Snyder-Mackler and colleagues indicates that training contraction intensity is positively correlated with quadriceps femoris muscle recovery, with an apparent threshold training contraction intensity of 10% of the maximal voluntary contraction of the uninvolved quadriceps femoris muscle.
41. Outline an appropriate protocol for muscle strengthening in terms of purpose, rationale, indications, parameters, and special considerations.
1. Purpose—To increase muscle strength, encourage muscle hypertrophy, and facilitate normal motor response
2. Rationale—Electrical stimulation can be used to help patients achieve a volitional contraction sufficient to increase strength and prevent disuse atrophy if they are unable to do so on their own.
3. Indications—Any patient in need of increasing girth and strength of an atrophied muscle 4. Parameters—Pulse duration, 200 to 300 msec; pulse rate, 35 to 80 Hz; intensity, motor, 60% ±
maximal voluntary contraction (MVC); ramp, 1 to 5 sec up/down, as tolerated; on/off, 1:5 ratio;
treatment time, activity specific, 10 to 20 repetitions, 3 to 5 days/week, 2 to 3 weeks; polarity, not applicable
5. Special considerations—This program should be used with patients with sufficient innervation to make muscle strengthening practical. It is important to avoid muscle fatigue with this type of stimulation.
42. Can NMES be used to augment ROM and strength of the shoulder musculature?
Yes. Strengthening and muscle girth improve in orthopaedic patients, and shoulder subluxation, in particular, can be prevented or corrected in neurologically involved patients.
43. What are the benefits of NMES after ACL reconstruction?
Reduced postsurgical muscle atrophy, increased muscle torque values, improved quadriceps femoris muscle strength, and improved functional recovery are some of the benefits. For example, in a study by Fitzgerald and colleagues, subjects receiving NMES (2500-Hz alternating current, time modulated to deliver 75 bursts per second, with a 2-second ramp-up and ramp-down time, a 10-second stimulation period at the maximum amplitude, followed by a 50-second rest period) twice a week in treatment sessions of 11 to 12 minutes showed significantly greater maximum voluntary isometric torque of the quadriceps femoris muscle and significantly improved functional status (per patient self-report) at 12 weeks following initiation of treatment than subjects not receiving NMES.
44. Is NMES more effective for strength training after ACL reconstruction when performed against isometric resistance?
Yes. Recent evidence suggests that the strength training effect is decreased when NMES is applied without isometric resistance. However, use of NMES without resistance is considered to be an acceptable alternative when clinicians do not have access to a dynamometer or for patients who do not tolerate NMES-induced contractions against isometric resistance.
45. Should the presence or absence of a knee extensor lag be a criterion for using or not using NMES after ACL reconstruction?
No. No relationship has been found between knee extensor lag and treatment outcomes following use of NMES. Data indicate that NMES is beneficial regardless of whether or not an extensor lag is present.
week and strength outcomes?
Yes. Three training sessions per week for 4 weeks have been shown to be effective for strength gains versus two training sessions per week for 4 weeks.
47. Can electrical stimulation protocols developed for a certain muscle group be used for training muscles with a different fiber-type composition?
Yes. Research suggests that variable frequency stimulation can augment the force of skeletal muscle irrespective of fiber type.
48. Is there a relationship between muscle contraction strength or fatigue and type of waveform used with electrical stimulation?
Yes. Recent evidence suggests that monophasic and biphasic waveforms generate greater torque and are less fatiguing than polyphasic waveforms.
49. What are the appropriate parameters and rationale for conventional, low-rate, and brief intense transcutaneous electrical nerve stimulation (TENS)?
50. Does TENS aid in the management of chronic low back pain when adminis- tered in isolation or when combined with an exercise program?
In general, there is no strong support that TENS is any more effective than a placebo in the management of chronic low back pain. TENS offers no apparent benefit to the patient as compared with exercise alone. Follow-through with exercise programs or TENS often is poor in this specific patient population.
51. Discuss appropriate considerations for maintaining range of motion.
Protocols should begin with simple one-plane joint movements, use antigravity starting positions with a rest between movements, and progress to antigravity positions without a rest between movements (i.e., flexion-rest-extension-rest > flexion-extension-flexion) as tolerated. Reasonable
Conventional Low Rate Brief Intense Phase duration 60-100 àsec 200-400 àsec 250 àsec
Pulse rate 80-125 Hz 2-4 Hz 125 Hz
Intensity Sensory just below Muscle fasciculation Sensory just below muscle motor
Treatment duration As needed 30-45 min 10-15 min
Onset of relief 10-20 min 25-30 min 1-5 min
Carryover 30 min to 2 hr Hours to days Short
Indications Acute, superficial Acute to chronic Wound debridement and deep
pain, first time pain fiber massage
application
Theory Gate theory Gate theory Gate theory
Opiate mediated Opiate mediated Opiate mediated
Placebo Placebo Placebo
Other Other
parameters are the following: intensity, to a tolerable motor level up to 3+/5; frequency, 35 to 50 Hz;
phase duration, 100 to 200 msec; ramp, 4 to 5 sec progressing to 3 sec; on/off, as required to achieve desired range of motion; treatment time, 30 min/day, 50 to 100 repetitions, as needed.
52. Discuss appropriate considerations for edema control.
Muscular activity is an important aspect of lymphatic and venous flow. The contraction of skeletal muscles by electrical stimulation can produce a muscle contraction capable of aiding lymphatic and venous flow. The intervention can be enhanced further by combining it with other forms of management, such as elevation, rest, and compression. Muscle pumping protocols are valuable for pain modulation. Reasonable stimulation parameters should focus on producing a nonfatiguing muscle contraction: pulse rate, 4 to 10 Hz; phase duration,±300àsec; waveform, biphasic or high volt; polarity, not applicable with this protocol; intensity, visible contraction of muscles in the area where edema is noted, 1/5 to 3/5; time of treatment, 30 min, 2 to 3 times/day, 1 to 2 weeks; electrode placement, muscle bulk of an involved muscle or an involved joint.
This protocol should be used in conjunction with ice application and elevation of the affected area.
53. Can electromyographic biofeedback aid in the recovery of quadriceps femoris muscle function following ACL reconstruction?
Yes. Findings from studies by Draper and by Draper and Ballard suggest (1) biofeedback is more effective than electrical stimulation in promoting recovery of peak torque, (2) biofeedback and electrical stimulation are comparable in terms of recovery of active knee extension, and (3) biofeedback combined with muscle strengthening exercises facilitates a more rapid recovery of quadriceps femoris peak torque following ACL reconstruction as compared to electrical stimulation alone.
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