First and foremost, patients and clinicians should understand the purpose of postoperative use of NMES: to reeducate neural pathways (affected by surgery) and to supplement voluntary muscle activation to deliver adequate training doses to the quadriceps muscle. Patients should be educated and familiarized with NMES, ideally before surgery. The first 3-week treatment phase should be initiated within the first few days following surgery, with a formal assessment of treatment response planned after 1 week and 3 weeks of treatment. A second 3-week treatment phase should follow only if the patient shows an adequate response to NMES therapy (as judged from the 2 evaluation sessions). The specific elements of our treatment algorithm are described in the following paragraphs.
Patient independence and comfort with the operation of the NMES device, as well as the quadriceps response to NMES, are key factors in determining the appropriateness of therapy. A short visit for NMES education and a home-based familiarization period (consisting of a few days) might ultimately improve patient tolerance and allow for more precise parameterization and dosing during therapy. Ideally, this should occur prior to surgery, to allow adequate time for familiarization with the NMES device and protocol. Patients should be instructed to properly position the electrodes, to operate the device, and to increase current intensity progressively. While no adverse effects are expected, patients should be informed that some redness is expected at the site of the electrodes following stimulation. However, this reaction should subside within 2 to 3 hours and should disappear thereafter.
NMES treatment protocols and conclusions regarding treatment effectiveness differ across recent clinical trials4,53,55,56. However, for trials demonstrating the benefits of NMES (i.e., when NMES resulted in greater gains in quadriceps strength and physical function compared with control interventions), some common themes emerge57. Key among these themes is a high-volume approach, in which NMES is performed on a daily basis (even multiple times per day), for at least 3 weeks. Therefore, we recommend multiple daily sessions of approximately 10 minutes (15 contractions) to maximize exposure when activation failure is greatest.
Patients should be encouraged to use high-intensity NMES, with stimulation amplitudes set at the highest tolerable level. Because the level of evoked force increases linearly with current amplitude29, this parameter is likely to be particularly critical to achieving therapeutic effectiveness. Clinicians and patients should be aware that amplitude may need to be increased periodically to accommodate for neural adaptations (tolerance) or factors such as adiposity or swelling, which can result in increased impedance, limiting contractile force.
Electrodes should be relatively large to minimize current density and maximize patient comfort and muscle activation, and they should be placed at opposite muscle ends (Fig. 3), ideally over both the vastus medialis (distally) and the vastus lateralis (proximally)58. Relatively long pulse durations (400 to 600 μs) should be used, as wide pulses are more likely to target motor fibers (thus maximizing quadriceps force production), while shorter pulse durations (<200 μs) might preferentially target sensory fibers and contribute to uncomfortable burning sensations during NMES59,60. Clinicians should pay special attention to device specifications to ensure that pulse duration is appropriately indicated on the device settings, as confusion of “pulse duration” and “phase duration” is common and could result in application of pulse durations that are half the intended ones (Fig. 1). Frequencies between 50 and 100 Hz are generally recommended25. Clinicians should choose the lowest frequencies within this range, thereby maximizing force production while limiting early muscle fatigue.
We also recommend an on:off ratio of 10:30 seconds, again to maximize exposure while still providing reasonable rest periods between contractions61. Because NMES stimulates a fixed volume between electrodes, the same muscle fibers may be repeatedly recruited during a session of NMES, which can result in reduced force production and relatively rapid muscle fatigue (see the section on NMES Therapy: Physiological Considerations). Clinicians should attempt to limit this phenomenon via subtle modifications in electrode placement or instruction regarding the frequency of sessions. Some muscle fatigue is likely necessary to induce strength gains, but as with any strengthening intervention, excessive levels of fatigue can result in deleterious effects, including pronounced soreness and muscle damage62. Such events, however, are rare in postoperative applications of NMES, given the dramatic activation failure that is typically present and other factors that limit muscle recruitment and current delivery.
After the first week of treatment, clinicians should assess the response of the quadriceps musculature to NMES therapy. In research settings, the intensity of the NMES-induced muscle contraction is typically measured using dynamometry, as a percentage of the isometric MVC. When a healthy contralateral leg is available for comparison (e.g., in patients after ACL reconstruction), forces of >50% of the contralateral MVC are desired to optimize the strengthening effects63. In practice, however, such assessments are rarely feasible, so a more qualitative approach is preferred. The criteria proposed by Fitzgerald et al.63 serve as a helpful guide: NMES should evoke a full, sustained, tetanic contraction of the quadriceps with visual or palpable evidence of superior patellar glide. If these criteria are not met, NMES may not achieve therapeutic doses, and alternative rehabilitation strategies should be considered.
Quadriceps activation failure may largely resolve in the first month following surgery, especially if NMES therapy proves effective4,53. Patients should be reevaluated after 3 weeks of treatment to determine if a high-volume approach is still warranted. The main risk of continued high-volume therapy is pronounced and chronic muscle fatigue64, which may result in reduced muscle force and a corresponding decline in the training dose delivered to the muscle.
Activation failure may persist beyond the initial postoperative period, and high-volume NMES therapy may still be indicated. The challenge lies in detecting persistent activation deficits, because common research methods (e.g., twitch interpolation) are impractical for use in a clinical setting. Clinical observations may help to rule in the presence of persistent activation failure. These observations would include factors such as (1) an inability to consistently perform a quadriceps set (superior translation of the patella during quadriceps contraction in knee extension), (2) an inability to perform a straight leg raise without extensor lag, or (3) subjective reports of difficulty with muscle control or recruitment. The presence of any deficit with any one of these clinical assessments suggests activation failure that would benefit from continued high-volume NMES.
Once a patient has progressed through treatment phase 1 and activation failure is largely resolved, a low-volume approach is recommended. Here, the goal is still to supply the quadriceps muscle with high-intensity NMES therapy, but with longer rest intervals between treatment sessions to allow for adequate recovery. Thus, NMES current characteristics and general settings are unchanged between the 2 treatment phases (Table I), but the duration of each session is increased to approximately 15 minutes and the frequency of treatment sessions is reduced to 4 to 6 sessions per week for treatment phase 2 (e.g., 1 session per day or every other day).
Once a patient has successfully completed treatment phase 2 (3 weeks with at least 12 sessions in total), we recommend discontinuing NMES therapy and focusing exclusively on voluntary strengthening exercise, which is by far more functional than NMES.
NMES is most effective in patients who have voluntary activation failure. These patients most commonly include those who have had knee injury or surgery (e.g., ACL reconstruction or total knee arthroplasty), but they could also include patients with anterior knee pain, knee osteoarthritis, or hip arthroplasty5,6. Regardless of the specific population, there are a few additional considerations that are important for effective NMES applications. First, electrode size is critical because current density (and patient discomfort) is inversely proportional to the electrode size; smaller electrodes result in greater discomfort and, therefore, smaller NMES doses. Electrodes with approximately 200 cm2 of total surface area are recommended (e.g., two 8 × 12-cm rectangular electrodes) (Fig. 3). Second, high intensity is meant to be tolerable, resulting in a tetanic muscle contraction; however, in most patients, it should be uncomfortable to achieve the most effective dose. It is important to push patients toward some discomfort to get the maximum benefit as there is a strong relationship between the level of force evoked by NMES (i.e., the NMES dose) and the resulting strength gains7,8,12. Stimulators that allow for ≥100 mA of intensity are often necessary, especially when postoperative swelling is present. Third, it is helpful to stimulate the muscle near its optimal length-tension relationship to maximize the level of evoked force and thus muscle tension65. For example, for the quadriceps muscle, it may be more effective (and comfortable) to use NMES with the knee between 60° and 75° of flexion rather than at full extension66. As mentioned earlier, modifying electrode placement and the knee (but also hip) flexion angle slightly from session to session may optimize recruitment of the various parts of the muscle. Finally, it is unknown whether using NMES with or without a concomitant voluntary muscle contraction is more effective. However, clinicians may want to consider encouraging patients to simultaneously (and submaximally) contract the stimulated muscle, particularly during the first treatment sessions, as a strategy for minimizing discomfort.
Growing research evidence supports the use of NMES as an adjunct exercise modality enhancing voluntary activation, muscle strength, and functional recovery in patients after orthopaedic surgery4,37,57,67. Furthermore, the advancements in technology leading to readily available and user-friendly stimulators render home self-treatment a viable option. Yet, NMES remains a clinically underutilized modality. This may be attributed to the multiple and often confusing and redundant parameters that must be considered during NMES treatment, as well as to the discomfort and muscle fatigue associated with the stimulation. The present study provides a concise summary of the physiological and methodological considerations guiding the selection of optimal stimulation parameters, as well as evidence-based recommendations for postoperative use of NMES of the quadriceps. The suggested treatment algorithm should help to streamline the clinician’s decision-making process, thus increasing the clinical utility of NMES following knee surgery.
The proposed approach ensures early identification of patients who are more likely to respond to the treatment. Furthermore, the recommendation to initiate familiarization with NMES prior to surgery is expected to improve patients’ tolerance of higher current intensities that are necessary to reach therapeutic levels of contraction68. While the presented protocol limited the preoperative treatment to a short habituation period, research has indicated that NMES-based treatment prior to total knee arthroplasty not only improved strength preoperatively but also contributed to muscle and functional recovery following surgery69. Thus, in the future, clinicians should also consider incorporating NMES as a preoperative treatment modality.
One should keep in mind that, at the current intensities necessary to induce muscle contractions that are strong enough to overcome activation failure, patient discomfort is almost unavoidable. The recommendations in the present article with regard to pulse characteristics, electrode size and location, joint position, and patient instructions are aimed at minimizing the discomfort as well as the muscle fatigue associated with NMES. Current research in the field of NMES is directed at further optimizing parameter settings to reduce these unwanted effects. For example, promising results have been recently reported with the use of 4 large electrodes placed over the quadriceps muscle3,70,71, which are designed to deliver current via multiple paths (distributed or multipath NMES) as opposed to the more traditional unidirectional current flow. Early studies with this application demonstrated stronger quadriceps muscle contractions combined with reduced discomfort and fatigue compared with conventional NMES70,71. More importantly, this relatively novel NMES modality proved to be more effective than both traditional NMES and standard rehabilitation for improving functional recovery after ACL reconstruction in a recently conducted randomized controlled trial3. Thus, distributed or multipath NMES may represent a valid alternative (or complement) to the NMES procedures described in the present article. Finally, although our treatment algorithm only refers to quadriceps NMES for the treatment of patients after knee surgery, the proposed principles can potentially be applied to other muscle groups and orthopaedic patients having muscle weakness and activation failure.
Investigation performed at the Human Performance Laboratory, Schulthess Clinic, Zurich, Switzerland
1. Gibson JN, Smith K, Rennie MJ. Prevention of disuse muscle atrophy by means of electrical stimulation: maintenance of protein synthesis. Lancet. 1988 ;2(8614):767–70.
2. Snyder-Mackler L, Delitto A, Bailey SL, Stralka SW. Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament. A prospective, randomized clinical trial of electrical stimulation. J Bone Joint Surg Am. 1995 ;77(8):1166–73.
3. Feil S, Newell J, Minogue C, Paessler HH. The effectiveness of supplementing a standard rehabilitation program with superimposed neuromuscular electrical stimulation after anterior cruciate ligament reconstruction: a prospective, randomized, single-blind study. Am J Sports Med. 2011 ;39(6):1238–47. Epub 2011 Feb 22.
4. Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Kohrt WM. Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial. Phys Ther. 2012 ;92(2):210–26. Epub 2011 Nov 17.
5. Rice DA, McNair PJ. Quadriceps arthrogenic muscle inhibition: neural mechanisms and treatment perspectives. Semin Arthritis Rheum. 2010 ;40(3):250–66. Epub 2009 Dec 2.
6. Hart JM, Pietrosimone B, Hertel J, Ingersoll CD. Quadriceps activation following knee injuries: a systematic review. J Athl Train. 2010 ;45(1):87–97.
7. Gondin J, Cozzone PJ, Bendahan D. Is high-frequency neuromuscular electrical stimulation a suitable tool for muscle performance improvement in both healthy humans and athletes? Eur J Appl Physiol. 2011 ;111(10):2473–87. Epub 2011 Sep 10.
8. Marmon AR, Snyder-Mackler L. Quantifying neuromuscular electrical stimulation dosage after knee arthroplasty. J Life Sci (Libertyville). 2011 ;5(8):581–3.
9. Selkowitz DM. Improvement in isometric strength of the quadriceps femoris muscle after training with electrical stimulation. Phys Ther. 1985 ;65(2):186–96.
10. Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL. Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction. Phys Ther. 1994 ;74(10):901–7.
11. Stevens JE, Mizner RL, Snyder-Mackler L. Neuromuscular electrical stimulation for quadriceps muscle strengthening after bilateral total knee arthroplasty: a case series. J Orthop Sports Phys Ther. 2004 ;34(1):21–9.
12. Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Schwartz RS, Schenkman M, Kohrt WM. Relationship between intensity of quadriceps muscle neuromuscular electrical stimulation and strength recovery after total knee arthroplasty. Phys Ther. 2012 ;92(9):1187–96. Epub 2012 May 31.
13. Vivodtzev I, Debigaré R, Gagnon P, Mainguy V, Saey D, Dubé A, Paré MÈ, Bélanger M, Maltais F. Functional and muscular effects of neuromuscular electrical stimulation in patients with severe COPD: a randomized clinical trial. Chest. 2012 ;141(3):716–25. Epub 2011 Nov 23.
14. Bade MJ, Stevens-Lapsley JE. Early high-intensity rehabilitation following total knee arthroplasty improves outcomes. J Orthop Sports Phys Ther. 2011 ;41(12):932–41. Epub 2011 Sep 30.
15. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007 ;89(4):780–5.
16. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, Gómez-Barrena E, de Pina MdeF, Manno V, Torre M, Walter WL, de Steiger R, Geesink RG, Peltola M, Röder C. International survey of primary and revision total knee replacement. Int Orthop. 2011 ;35(12):1783–9. Epub 2011 Mar 15.
17. Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil. 2002 ;83(10):1432–6.
18. Bickel CS, Gregory CM, Dean JC. Motor unit recruitment during neuromuscular electrical stimulation: a critical appraisal. Eur J Appl Physiol. 2011 ;111(10):2399–407. Epub 2011 Aug 26.
19. Gregory CM, Bickel CS. Recruitment patterns in human skeletal muscle during electrical stimulation. Phys Ther. 2005 ;85(4):358–64.
20. Lieber RL. Skeletal muscle adaptability. III: muscle properties following chronic electrical stimulation. Dev Med Child Neurol. 1986 ;28(5):662–70.
21. Reed B. The physiology of neuromuscular electrical stimulation. Pediatr Phys Ther. 1997;9(3):96–102.
22. Theurel J, Lepers R, Pardon L, Maffiuletti NA. Differences in cardiorespiratory and neuromuscular responses between voluntary and stimulated contractions of the quadriceps femoris muscle. Respir Physiol Neurobiol. 2007 ;157(2-3):341–7. Epub 2006 Dec 15.
23. Vanderthommen M, Depresseux JC, Dauchat L, Degueldre C, Croisier JL, Crielaard JM. Spatial distribution of blood flow in electrically stimulated human muscle: a positron emission tomography study. Muscle Nerve. 2000 ;23(4):482–9.
24. Maffiuletti NA. Physiological and methodological considerations for the use of neuromuscular electrical stimulation. Eur J Appl Physiol. 2010 ;110(2):223–34. Epub 2010 May 15.
25. Vanderthommen M, Duchateau J. Electrical stimulation as a modality to improve performance of the neuromuscular system. Exerc Sport Sci Rev. 2007 ;35(4):180–5.
26. Adams GR, Harris RT, Woodard D, Dudley GA. Mapping of electrical muscle stimulation using MRI. J Appl Physiol (1985). 1993 ;74(2):532–7.
27. Henneman E, Somjen G, Carpenter DO. Functional significance of cell size in spinal motoneurons. J Neurophysiol. 1965 ;28:560–80.
28. Feiereisen P, Duchateau J, Hainaut K. Motor unit recruitment order during voluntary and electrically induced contractions in the tibialis anterior. Exp Brain Res. 1997 ;114(1):117–23.
29. Binder-Macleod SA, Halden EE, Jungles KA. Effects of stimulation intensity on the physiological responses of human motor units. Med Sci Sports Exerc. 1995 ;27(4):556–65.
30. Knight CA, Kamen G. Superficial motor units are larger than deeper motor units in human vastus lateralis muscle. Muscle Nerve. 2005 ;31(4):475–80.
31. Enoka RM. Activation order of motor axons in electrically evoked contractions. Muscle Nerve. 2002 ;25(6):763–4.
32. Jubeau M, Gondin J, Martin A, Sartorio A, Maffiuletti NA. Random motor unit activation by electrostimulation. Int J Sports Med. 2007 ;28(11):901–4. Epub 2007 May 24.
33. Bigland B, Lippold OC. Motor unit activity in the voluntary contraction of human muscle. J Physiol. 1954 ;125(2):322–35.
34. Gosker HR, Engelen MP, van Mameren H, van Dijk PJ, van der Vusse GJ, Wouters EF, Schols AM. Muscle fiber type IIX atrophy is involved in the loss of fat-free mass in chronic obstructive pulmonary disease. Am J Clin Nutr. 2002 ;76(1):113–9.
35. Morrissey MC. Electromyostimulation from a clinical perspective. A review. Sports Med. 1988 ;6(1):29–41.
36. Roig M, Reid WD. Electrical stimulation and peripheral muscle function in COPD: a systematic review. Respir Med. 2009 ;103(4):485–95. Epub 2008 Dec 16.
37. Kim KM, Croy T, Hertel J, Saliba S. Effects of neuromuscular electrical stimulation after anterior cruciate ligament reconstruction on quadriceps strength, function, and patient-oriented outcomes: a systematic review. J Orthop Sports Phys Ther. 2010 ;40(7):383–91.
38. Petterson S, Snyder-Mackler L. The use of neuromuscular electrical stimulation to improve activation deficits in a patient with chronic quadriceps strength impairments following total knee arthroplasty. J Orthop Sports Phys Ther. 2006 ;36(9):678–85.
39. Gondin J, Brocca L, Bellinzona E, D’Antona G, Maffiuletti NA, Miotti D, Pellegrino MA, Bottinelli R. Neuromuscular electrical stimulation training induces atypical adaptations of the human skeletal muscle phenotype: a functional and proteomic analysis. J Appl Physiol (1985). 2011 ;110(2):433–50. Epub 2010 Dec 2.
40. Hopkins JT, Ingersoll CD, Krause BA, Edwards JE, Cordova ML. Effect of knee joint effusion on quadriceps and soleus motoneuron pool excitability. Med Sci Sports Exerc. 2001 ;33(1):123–6.
41. Hurley MV, Scott DL, Rees J, Newham DJ. Sensorimotor changes and functional performance in patients with knee osteoarthritis. Ann Rheum Dis. 1997 ;56(11):641–8.
42. Hurley MV, Jones DW, Newham DJ. Arthrogenic quadriceps inhibition and rehabilitation of patients with extensive traumatic knee injuries. Clin Sci (Lond). 1994 ;86(3):305–10.
43. Shakespeare DT, Stokes M, Sherman KP, Young A. Reflex inhibition of the quadriceps after meniscectomy: lack of association with pain. Clin Physiol. 1985 ;5(2):137–44.
44. Slemenda C, Brandt KD, Heilman DK, Mazzuca S, Braunstein EM, Katz BP, Wolinsky FD. Quadriceps weakness and osteoarthritis of the knee. Ann Intern Med. 1997 ;127(2):97–104.
45. Arvidsson I, Arvidsson H, Eriksson E, Jansson E. Prevention of quadriceps wasting after immobilization: an evaluation of the effect of electrical stimulation. Orthopedics. 1986 ;9(11):1519–28.
46. Mizner RL, Stevens JE, Snyder-Mackler L. Voluntary activation and decreased force production of the quadriceps femoris muscle after total knee arthroplasty. Phys Ther. 2003 ;83(4):359–65.
47. Stackhouse SK, Stevens JE, Lee SC, Pearce KM, Snyder-Mackler L, Binder-Macleod SA. Maximum voluntary activation in nonfatigued and fatigued muscle of young and elderly individuals. Phys Ther. 2001 ;81(5):1102–9.
48. Gapeyeva H, Buht N, Peterson K, Ereline J, Haviko T, Pääsuke M. Quadriceps femoris muscle voluntary isometric force production and relaxation characteristics before and 6 months after unilateral total knee arthroplasty in women. Knee Surg Sports Traumatol Arthrosc. 2007 ;15(2):202–11. Epub 2006 Sep 28.
49. Hortobágyi T, Maffiuletti NA. Neural adaptations to electrical stimulation strength training. Eur J Appl Physiol. 2011 ;111(10):2439–49. Epub 2011 Jun 4.
50. Oatis CA, Li W, DiRusso JM, Hoover MJ, Johnston KK, Butz MK, Phillips AL, Nanovic KM, Cummings EC, Rosal MC, Ayers DC, Franklin PD. Variations in delivery and exercise content of physical therapy rehabilitation following total knee replacement surgery: a cross-sectional observation study. Int J Phys Med Rehabil. 2014;Suppl 5. Epub 2014 Apr 22.
51. van Grinsven S, van Cingel RE, Holla CJ, van Loon CJ. Evidence-based rehabilitation following anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2010 ;18(8):1128–44. Epub 2010 Jan 13.
52. Electrophysical agents—contraindications and precautions: an evidence-based approach to clinical decision making in physical therapy. Physiother Can. 2010 ;62(5):1–80. Epub 2011 Jan 5.
53. Avramidis K, Strike PW, Taylor PN, Swain ID. Effectiveness of electric stimulation of the vastus medialis muscle in the rehabilitation of patients after total knee arthroplasty. Arch Phys Med Rehabil. 2003 ;84(12):1850–3.
54. Mintken PE, Carpenter KJ, Eckhoff D, Kohrt WM, Stevens JE. Early neuromuscular electrical stimulation to optimize quadriceps muscle function following total knee arthroplasty: a case report. J Orthop Sports Phys Ther. 2007 ;37(7):364–71.
55. Petterson SC, Mizner RL, Stevens JE, Raisis L, Bodenstab A, Newcomb W, Snyder-Mackler L. Improved function from progressive strengthening interventions after total knee arthroplasty: a randomized clinical trial with an imbedded prospective cohort. Arthritis Rheum. 2009 ;61(2):174–83.
56. Levine M, McElroy K, Stakich V, Cicco J. Comparing conventional physical therapy rehabilitation with neuromuscular electrical stimulation after TKA. Orthopedics. 2013 ;36(3):e319–24.
57. Kittelson AJ, Stackhouse SK, Stevens-Lapsley JE. Neuromuscular electrical stimulation after total joint arthroplasty: a critical review of recent controlled studies. Eur J Phys Rehabil Med. 2013 ;49(6):909–20. Epub 2013 Nov 28.
58. Forrester BJ, Petrofsky JS. Effect of electrode size, shape and placement during electrical stimulation. J Appl Res. 2004;4(2):346–54.
59. Gondin J, Giannesini B, Vilmen C, Dalmasso C, le Fur Y, Cozzone PJ, Bendahan D. Effects of stimulation frequency and pulse duration on fatigue and metabolic cost during a single bout of neuromuscular electrical stimulation. Muscle Nerve. 2010 ;41(5):667–78.
60. Kesar T, Binder-Macleod S. Effect of frequency and pulse duration on human muscle fatigue during repetitive electrical stimulation. Exp Physiol. 2006 ;91(6):967–76. Epub 2006 Jul 27.
61. Packman-Braun R. Relationship between functional electrical stimulation duty cycle and fatigue in wrist extensor muscles of patients with hemiparesis. Phys Ther. 1988 ;68(1):51–6.
62. Nosaka K, Aldayel A, Jubeau M, Chen TC. Muscle damage induced by electrical stimulation. Eur J Appl Physiol. 2011 ;111(10):2427–37. Epub 2011 Aug 3.
63. Fitzgerald GK, Piva SR, Irrgang JJ. A modified neuromuscular electrical stimulation protocol for quadriceps strength training following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther. 2003 ;33(9):492–501.
64. Zory RF, Jubeau MM, Maffiuletti NA. Contractile impairment after quadriceps strength training via electrical stimulation. J Strength Cond Res. 2010 ;24(2):458–64.
65. Lieber RL, Kelly MJ. Factors influencing quadriceps femoris muscle torque using transcutaneous neuromuscular electrical stimulation. Phys Ther. 1991 ;71(10):715–21; discussion 722-3.
66. Fahey TD, Harvey M, Schroeder RV, Ferguson F. Influence of sex differences and knee joint position on electrical stimulation-modulated strength increases. Med Sci Sports Exerc. 1985 ;17(1):144–7.
67. Hasegawa S, Kobayashi M, Arai R, Tamaki A, Nakamura T, Moritani T. Effect of early implementation of electrical muscle stimulation to prevent muscle atrophy and weakness in patients after anterior cruciate ligament reconstruction. J Electromyogr Kinesiol. 2011 ;21(4):622–30. Epub 2011 Feb 18.
68. Laufer Y, Snyder-Mackler L. Response of male and female subjects after total knee arthroplasty to repeated neuromuscular electrical stimulation of the quadriceps femoris muscle. Am J Phys Med Rehabil. 2010 ;89(6):464–72.
69. Walls RJ, McHugh G, O’Gorman DJ, Moyna NM, O’Byrne JM. Effects of preoperative neuromuscular electrical stimulation on quadriceps strength and functional recovery in total knee arthroplasty. A pilot study. BMC Musculoskelet Disord. 2010;11:119. Epub 2010 Jun 14.
70. Maffiuletti NA, Vivodtzev I, Minetto MA, Place N. A new paradigm of neuromuscular electrical stimulation for the quadriceps femoris muscle. Eur J Appl Physiol. 2014 ;114(6):1197–205. Epub 2014 Feb 25.
71. Morf C, Wellauer V, Casartelli NC, Maffiuletti NA. Acute effects of multipath electrical stimulation in patients with total knee arthroplasty. Arch Phys Med Rehabil. 2015 ;96(3):498–504. Epub 2014 Nov 4.