Tara Jo Manal PT, OCS, SCS: Director of Clinical Services Orthopedic Residency Director

1. Electrical Stimulation to Augment Muscle Strengthening: Guidelines for Surgical Procedures, Diagnosis and Co-Morbidities Tara Jo Manal PT, OCS, SCS: Director of Clinical Services Orthopedic Residency Director University of Delaware Physical Therapy Department Tarajo@udel.edu 302-831-8893

2. Properties of Electrical Stimulation Tara Jo Manal PT, OCS, SCS University of Delaware

3. Properties of Electric Stimulation • Voltage • Voltage represents the driving force that repels like charges and attracts opposite charges • Current • Current is the movement of charged particles in response to voltage • Ampere represents an amount of charge moving per unit time • The higher the voltage, the higher the current

4. Magnitude of Charge Flow • Conductance • Relative ease of movement of charged particles in a charged medium • If the ease of movement is high, the resistance to movement is low • Resistance • Opposition to movement of charged particles • Lower resistance provides greater comfort/tolerance by patient for higher intensity stimulation since less charge is needed to penetrate the skin

5. Ohm’s Law • I = V/R • Current increases as the driving force (V) is increased or as the Resistance (R) to movement is decreased • As the skin resistance decreases, more of the current can flow, increasing the response

6. Properties • Impedance • Opposition to alternating currents • Higher frequency stimulation can pass with greater ease • Impedance is the best word to describe resistance to flow in human tissue since it is comprised of the tissue resistance and the insulator (subcutaneous fat) effects of tissue • Greater the impedance, greater the intensity required to achieve therapeutic goal High frequency stimulation is more comfortable because impedance is lower

7. Current Density • Represents the intensity/area under a stimulation pad • At fixed voltage • smaller the electrode the greater the intensity of the stimulation compared to larger electrode • Caution in setting intensity level with smaller electrodes or damaged electrodes • Very high current density can be related to biological damage or burns • Large electrodes • Can the unit produce sufficient current intensity?

8. Current Modulation • Timing • Altering the time characteristics of stimulation • Train • a continuous, repetitive series of pulses at a fixed frequency

9. Current Modulation • Burst • a package of train pulses • delivered at a specified frequency • e.g. 2 bursts per second

10. Carrier Characteristics • Carrier frequency • Pulse duration is 1/f • To increase pulse duration to improve muscle force output you would decrease the train frequency • 2000Hz = 1/2000 or 500second pulse duration • 1000Hz = 1/1000 or 1000second (1 millisecond) pulse duration

11. Frequency and Pulse Duration If the f is 5 Hz or 5 cycles/second The duration is 1/5 or 20milliseconds

12. Pulse Duration • Increases recruitment of motor units • Improves the muscle contraction • Often labeled “width” or “pulse width”

13. How to Achieve High Force • Activate more motor units (recruitment) • Drive the motor units more quickly (Rate coding)

14. NMES – Increasing Recruitment • How to recruit more motor units electrically? • Increase recruitment via ↑ phase charge • How to increase phase charge • Increase amplitude • Increase pulse duration • Or BOTH Phase Charge Mixed Nerve

15. Frequency • Increasing frequency • Tetanic contraction • Force production reaches a plateau maximum between 50-80 pulses per second • For muscle strengthening you want 50-80 pulses/second or 50-80 bursts/second

16. Frequency Controls • Usually labeled “Rate or Pulse Rate” • Set the number of pulses (or AC cycles) delivered through each channel per second • As frequency is increased, impedance is decreased

17. NMES – Increasing frequency • How to achieve high force • Rate Coding • Increase the frequency of stimulation • But… increased frequency  increased fatigue

18. Quality of Contraction • Goal = strong tetanic contraction • Stimulation frequency 50-80 pps

19. Understanding the Manuals • Presets • Advantage’s & Disadvantages • Adjustable Controls • Waveform Selection • Amplitude Controls • AC: generally have a maximum of 100 – 200mA • Independent vs. Shared amplitude control for multiple channels

20. Cycle time controls • On & Off Time • Duration of stimulation and rest • Rest time dependent on goal of treatment • Strengthening- Adequate rest to avoid fatigue

21. Ramp Controls • Controls the rate the amplitude increases • Provide for more comfortable onset and cessation of stimulus when very high levels of stimulation are required • Can adjust if contraction is coming on too quickly or stopping too quickly

22. Waveform type • Waveform • Patient dependent • Delitto Rose PT 1986 • UD PT Clinic • Versastim • Empi

23. Stimulation Parameters • What can we modify? • Pulse Duration • Pulse Frequency • Waveform type • Off time (time between contractions) • Ramp time

24. Stimulator Controls • Programmed Stimulation Pattern Controls • Found on various stimulation devices, mostly • Can be limiting, if user is unable to program stimulation patterns for a specific application • Output Channel Selection • Simultaneous • Alternate or reciprocal mode

25. Line vs. Battery Powered

26. Test The Unit Empi 300 PV

27. EMPI 300PV Empi 300PV 1-800-328-2536

28. Dose of NMES • Maximal tolerable current and device dependent- MVIC above blue line

29. Dose of NMES • Be sure your machine is capable of current necessary

30. Test The Electrodes

31. Electrodes • How to improve the lifespan • Proper storage • Keep them moist • Placed properly on plastic • Improves conductivity

32. Another Brand of Electrodes

33. Same Intensity- Different Electrodes

34. Electrodes • Model F216 • Size 3” x 5” • 8 x 13 cm • Rectangle • Qty 2 • 1-800-538-4675

35. Electrodes • Reflex Tantone 624 • Ref# EC89270 • Size 2in x 2in • 5.08cm x 5.08cm • Qty 4 • Tyco/Heathcare • Unipatch • 1-800-328-9454

36. Tens Clean Cote • Uni-Patch • 1-800-328-9454 • Function • Improves conductivity

37. Pad Placement • Typically include motor points of muscle of interest

38. Pad Placement • Relationship between Pad placement and current- Non-tetanic contraction

39. Pad Placement • Increase current, contraction becomes tetanic

40. Treatment Administration • Patient motivation factors • Assist your patient in tolerating treatment • Monitor • set targets, watch output, give article • Blunter • wear headphones, towel over head, body relaxation (Delitto et al PT 1992)

41. Give the Patient Control • Self trigger if possible • Therapist manually resuming stim • Count down to the stim • Explain to the patient the value of the modality

42. General Tens Clean Cote Change the waveform Decrease pulse duration may need to also increase the frequency for comfort Specific Increase ramp time Self trigger Increase rest time Only if you see them fatiguing drastically What we do when things are not going well …

43. Evidence to support the clinical use of electrical stimulation for muscle strengthening

44. Increased Functional Load • For muscle to hypertrophy and/or gain strength the overload principle of high weight at low repetitions is necessary • Currier and Mann • Looked at healthy male college students • Utilized an intensity of at least 60% MVIC paralleling voluntary exercise protocols for functional overload • Conclusion: NMES and volitional exercise were equivalent training stimuli (Delitto,Snyder-Mackler, 1990)

45. Increased Functional Load Kots • Therapeutic efficacy reported for electrical stimulation greater than volitional exercise, when strengthening healthy muscle • Intensity was 10-30% greater than MVC • Strength gains of 30-40% (Delitto,Snyder-Mackler, 1990)

46. Increased Functional Load • Conclusions on Overload • Significant strength gains can be achieved in healthy muscle with an electrically augmented training program • The intensity however needs to be extremely high (>100%MVIC) • Electrical stimulation offers equivalent muscle strengthening effects to voluntary exercise in healthy subjects • If intensity level parallels volitional exercise intensities (Delitto,Snyder-Mackler, 1990)

47. Increased Functional Load • Conclusion on Overload • Lower loads may still help in muscle recovering from injury/surgery • Most studies using subjects other than healthy male college students demonstrated greater strength gains in subjects training with NMES compared to volitional exercise alone (Delitto,Snyder-Mackler, 1990)

48. Electrical Stimulation for Strength Snyder-Mackler et al., 1991 • Purpose: To ascertain the effects of electrically elicited co-contraction of the thigh muscles on several parameters of gait and on isokinetic performance of muscles in patients who had reconstruction of the ACL • 2 groups: NMES + volitional exercise Volitional exercise only • Treatment intervention from 3rd to 6th week post-op

49. Electrical Stimulation for Strength Snyder-Mackler et al., 1991 • Results: • Significantly greater average and peak torque of the quadriceps femoris at both 90°/sec and 120°/sec in the NMES group • No significant difference in performance of the hamstring muscles between groups • Torque produced in the involved hamstrings averaged 80% of the strength in the uninvolved leg

50. Electrical Stimulation for Strength Snyder-Mackler et al., 1991 • Conclusions: • The quadriceps muscles of these patients were stronger in the eighth post-operative week than reported averages for similar patients even years after surgery