. 2017;69(5):1–76. doi: 10.3138/ptc.2015-88

Table 8.

Details of Individual Studies on Use of NMES in ACL Reconstruction

Author (Date), Study Design, and Study Size	Population Comparison Groups	Electrode Parameters: Size, Channels, Placement, and Limb Position	Stimulation Parameters: Waveform, Frequency, Pulse Duration, ON:OFF Time, and Amplitude	Treatment Schedule: Min/D Repetitions, D/Wk, and Total Wk Progression	Outcome Measures and Timing	Statistically Significant Results, NMES Compared with CON	Comments
Anderson and Lipscomb (1989)¹⁰⁴ RCT N=100 enrolled; N=96 analyzed Included in SR⁹²	ACL recon using semitendinosis and gracilis±meniscal repair POD 1 NMES+immobilization in flex 60° (n=20) Immobilization in flex 60° (n=20) Immobilization in flex+CPM (n=20) TENS+immobilization in ext (n=20) Immobilization in ext (n=20)	Electrode size and placement nr	Biphasic PC 35 Hz 150 μs ON:OFF 10:110 s Amplitude nr No simultaneous voluntary contraction with NMES	10 h/d (300 contractions) 7 d/wk 12 wk	Thigh volume: circumferential measure @ 0, 6, 12, 28, 52, and 78 wk Varus/valgus stress test: X-ray with 15 lb stress @ 78 wk ACL laxity: KT-1000 @ 28 and 78 wk Strength: Cybex @ 28, 52, and 78 wk	Increased strength @ 52 and 78 wk Increased ROM and less patellofemoral crepitus (no time frames provided) No significant between-groups difference in all other outcomes	Unusually demanding protocol 10 h/d×12 wk Pulse duration short to elicit effective strengthening of quads. Several key features of protocol not reported. Technical difficulties with the stimulator precluded use of NMES for 5 patients for extended periods. Methods for assessing patellofemoral crepitus not described.
Currier and colleagues (1993)⁹⁸ Non-RCT N=17 enrolled; N=17 analyzed Included in SR⁹²	ACL recon Patellar tendon NMES (n=7) from POD 1 NMES (n=7) from POD 1–3 Then NMES+PEMF CON (n=3)	8×12.5 cm 2 channels Electrodes: over femoral triangle and on VM and muscle bellies of the biceps femoris and medial hams Knee in full ext	2500 Hz AC 50 Hz burst rate NMES group: ON:OFF 15:50 s Ramp up 5 s NMES/PEMF group: ON:OFF 10:50 s Ramp-up 5 s Amplitude set for each patient pre-op at 50% of MVC Simultaneous voluntary contraction during NMES	10 contractions 1–3/d post-op Then 3 d/wk Total 6 wk	Thigh girth: tape measure @ pre-op and 6 wk Pain: VAS comparing 3 sessions each of NMES with NMES+PEMF Torque MVIC: Biodex – only for NMES+PEMF group @ pre-op and 6 wk	NMES and NMES+PEMF reduced loss of thigh girth @ 6 wk NMES+PEMF was less painful than NMES alone (sessions 1–3 vs. sessions 4–6) Torque decrease averaged 13.1% using NMES+PEMF @ 6 wk	Lack of randomization and small sample size warrant caution in extrapolating findings to clinical practice. Torque comparisons were not available.
Delitto and colleagues (1988)⁹⁹ RCT N=20 enrolled; N=20 analyzed Included in SR¹¹⁶	ACL recon 2–3 wk post-op NMES (n=10) CON (n=10): Ex	Electrode size nr 2 channels Electrodes: on quads and hams co-contraction In 65° knee flex	2500 Hz AC 50 Hz burst rate ON:OFF 15:50 s Amplitude max tolerable No simultaneous voluntary contraction with NMES	15 contractions 5 d/wk 3 wk	Isometric flex and ext torque: Cybex @ 0 and 3 wk	Increased torque	Compliance with voluntary Ex was not monitored.
Draper and Ballard (1991)⁹⁵ RCT (groups matched for age and gender) N=30 enrolled; N=30 analyzed Included in SR¹¹⁶	ACL recon POD 1 NMES (n=15): EMG-BF NMES (n=15) during voluntary contraction Subjects were trained using device pre-op Both groups standard rehab POD 1–6 wk	5×10 cm 1 channel Electrodes: active on femoral nerve; dispersive 5–7 cm prox to patella on VM	Waveform nr; PC 35 Hz ON:OFF 10:20 s Ramp-up and ramp-down 4:2 s Amplitude set to tolerance, increasing each session No simultaneous voluntary contraction with NMES	30 min TID 7 d/wk 4 wk	Isometric peak torque as % of non-operated limb: Cybex @ wk 6 ROM: goniometer weekly @ wk 1–6	Strength gain in group with EMG–BF greater than NMES alone No significant between-groups difference in all other outcomes	Initial intensity of stimulation likely suboptimal (initially only 15 mA, ultimately 40 mA). Compliance with home programme was tracked with a log. No CON group for comparison
Ediz and colleagues (2012)¹⁰⁵ RCT N=29 enrolled; N=26 analyzed	ACL recon Hams autograft (aged 18–40 yr) NMES (n=15): POD 4+Ex POD 1 CON (n=14): Ex POD 1	6×8 cm Channel number nr Electrodes: on quads, hams, triceps surae	Waveform nr; PC 30 Hz 300 μs ON:OFF 10:20 s Amplitude max tolerable without discomfort No simultaneous voluntary contraction with NMES	20 min/d 5 d/wk 6 wk	Effusion: numerical bulge-dancing patella Swelling: difference in circumference @ mid-centre of the patella between operated an d non-operated knees Pain: average daily resting pain International Knee Documentation Committee scoring system Tegner Activity Scale @ 0, 1, 2, 8, 12, and 24 wk	Less effusion @ 7 d Less swelling @ 7 d Lower pain scores @ 7 d–12 wk No significant between-groups difference in all other outcomes	The primary purpose was to examine swelling and pain. Strength was not measured.
Eriksson and Häggmark (1979)⁹⁶ RCT N=8 enrolled; N=8 analyzed Included in SR⁹²	ACL recon Casted post-op NMES (n=4): NMES+Ex CON (n=4): Ex	Electrode size nr 1 channel Electrodes: through hole in cast on distal quads and above the femoral nerve @ the groin 10° knee flex	Waveform nr; PC 200 Hz PD nr ON:OFF 5–6:5 s Self-adjusted voltage to below pain threshold No simultaneous voluntary contraction with NMES	1 h/d 5 d/wk 4 wk	Biopsy of VL Atrophy SDH concentration @ 0, 1, and 5 wk	Less muscle atrophy Increased oxidative enzyme	A frequency of 200 Hz is unusual in NMES literature. High frequency results in rapid muscle fatigue and may not be ideal for strengthening.¹¹⁷ Reliability within or between assessors of classification of biopsy sample was not established. Patients immobilized after surgery.
Fitzgerald and colleagues (2003)¹⁰⁸ RCT N=48 enrolled; N=43 analyzed Included in SR¹¹⁶	ACL recon NMES (n=21): NMES+Ex CON (n=22): Ex	6.98×12.7 cm 1 channel Electrodes on VL and VM Supine full knee ext	2500 Hz AC 75 Hz burst rate ON:OFF 10:50 s Ramp-up and ramp-down 2:2 s Amplitude max tolerated (minimum full, sustained, tetanic contraction with palpable evidence of superior glide of patella and no fasciculations) No simultaneous voluntary contraction with NMES	10 contractions (11–12 min) 2 d/wk Mean Rx time for both groups: 10+ wk Ex programme progressed individually	Quad strength: Biodex isometric @ 60° flex Self-reported function: ADL scale Achievement clinical milestones: proportion of successful subjects Pain: NPRS @ 0, 12, and 16 wk	Greater strength @ 12 and 16 wk Greater proportion achieved clinical criteria for advancing to agility training @ 16 wk Better ADL score @ 12 and 16 wk No significant between-groups difference in NPRS	Single blinded Authors noted that the programme was less effective than prior studies; session frequency and leg position might explain this difference. ADL score was a subjective measure, and there was no blinding of subjects.
Hasegawa and collegues (2011)¹⁰⁰ RCT N=20 enrolled; N analyzed nr	ACL recon Semitendinosis autograft (aged 13–54 yr) NMES (n=10): POD 2+Ex CON (n=10): Ex	4 channels active simultaneously Electrodes: on quads, hams, tib ant, triceps surae Supine with knee ext	Monophasic PC 20 Hz 250 μs ON:OFF 5:2 s Amplitude set to max tolerable and individually progressed No simultaneous voluntary contraction with NMES	20 min/d 5 d/wk 4 wk	Muscle thickness: (US still imaging) @ pre-op and @ 4 and 12 wk Quads strength: Cybex normalized peak torque @ 60°/s pre-op and @ 4 and 12 wk Muscle function: Lysholm scores @ pre-op and 6 mo post-op	Increased thickness VL and triceps surae Less decline in quads strength Greater recovery of quads strength @ 12 wk No change in Lysholm scores	Unexpected finding given that the frequency (20 Hz) and duty cycle were less than typically used (50–80 Hz) for muscle strengthening. Frequency of 20 Hz may have limited fatigue associated with stimulation.
Lepley and colleagues (2015)¹⁰⁹ RCT Parallel longitudinal design N=43 enrolled; N=36 analyzed	ACL recon +10 healthy CON NMES (n=9): post-op wk 1–6+eccentric Ex from post-op wk 6+PT NMES (n=12): NMES alone post-op wk 1–6+PT Eccentric Ex alone (n=9): from post-op wk 6+PT CON (n=13): PT wk 1–6	7×13 cm 1 channel Electrodes: on VL and VM @ 60° knee flex	2500 Hz AC 75 Hz burst rate ON:OFF 10:50 s Ramp-up 2 s Amplitude max tolerable No simultaneous voluntary contraction with NMES Eccentric Ex: 4 sets of 10 @ 60% 1 RM; 2 min rest between sets	10 contractions 2 d/wk 6 wk	Strength: % MVIC change in quads strength (3 trials normalized to body weight) @ 90°/flex Quads activation: % change scores in Central Activation Ratio using superimposition burst technique Relationship change between quads activation and strength Quads activation and strength compared with healthy controls @ pre-op, 12 wk post-op, and return to play	Increased quads strength recovery using NMES+eccentric Ex or eccentric Ex alone No significant between-groups difference in all other outcomes	Eccentric Ex was the key determinant for improvements in muscle activation and strength (the authors contend that the stimulator they used was not powerful enough to overcome the inhibition of the muscle).
Lieber and colleagues (1996)¹⁰⁶ RCT N=40 enrolled; N analyzed nr Included in SR⁹²	ACL recon 2–6 wk post-op and 90° knee flex NMES (n=20): NMES CON (n=20): Ex Both groups allowed therapist-monitored home Ex	Electrode size and placement nr	Custom-built device Asymmetric biphasic PC 50 Hz 250 μs ON:OFF 10:20 s (for both NMES and voluntary Ex) Ramp-up and ramp-down 2:2 s Amplitude max tolerable No simultaneous voluntary contraction with NMES	30 min/d (60 contractions) 5 d/wk 4 wk Eccentric Ex increased 15%, 25%, 35%, and 45% of the injured limb's max volitional torque @ wk 1, 2, 3, and 4, respectively	Knee ext torque: torque transducer Transducer recorded muscle tension for each contraction over the 4-wk period for every subject, both NMES and Ex @ 6, 8, 12, 24, and 52 wk	No between-groups differences in all outcomes	The authors attempted to match the groups during training on the parameter of activity (Nm*Min). However, the voluntary Ex group still performed 30% more activity than NMES. Thus, on the basis of training intensity the study favoured the Ex group. Fatigue-inducing protocol of 300 contractions/wk might account for lack of benefit.
Paternostro-Slugo and colleagues (1999)¹¹¹ RCT N=49 enrolled; N=47 analyzed Included in SR¹¹⁶	Aged 17–40 yr Post–ACL recon (n=25) Post–ACL patellar ligament repair (n=24) NMES (n=16): NMES+Ex TENS+Ex (n=14) CON (n=17): Ex	Electrode size nr 4 channels Electrodes: on MP, VL, rec fem, VM, hams	Monophasic PC 2 sets: set 1, 30 Hz, 200 μs; set 2, 50 Hz, 200 μs Set 1: ON:OFF 5:15 s, 6 min rest between sets Set 2: ON:OFF 10:50 s Amplitude tolerance level, strong visible muscle action No simultaneous voluntary contraction with NMES	Set 1: 12 contractions repeated 4×(total 48) Set 2: 12 contractions BID (total 120 contractions/d) 7 d/wk 6 wk	Quads and hams strength: Isometric (45° flex) Isokinetic (60°/s) @ 6, 12, and 52 wk	No significant between-groups differences in strength	Tracked compliance Double blinded PD less than ideal to elicit muscle strengthening. No. of contractions for training greater than usual. Fatigue-inducing protocol of 500 contractions/wk might account for lack of benefit.
Rebai and colleagues (2002)¹⁰⁷ RCT N=10 enrolled; N=10 analyzed Included in SR⁹²	ACL recon (6–24 mo post-injury) POD 3–4 NMES 80 Hz+Ex (n=5) NMES 20 Hz+Ex (n=5) Ex standardized 2 h/d, 5 d/wk	Electrode size nr Electrodes: on MP of 3 superficial heads of quads Knee ~75° flex	Asymmetric balanced biphasic PC NMES 20 Hz: amplitude set to achieve≥25% MVIC NMES 80 Hz: amplitude set to achieve≥35% MVIC 300 μs For 20 Hz group, ON:OFF 15:10 s; for 80 Hz group, ON:OFF 15:75 s Amplitude max tolerable No simultaneous voluntary contraction with NMES	20 Hz: 144 contractions (60 min) 80 Hz: 36 contractions (54 min) 5 d/wk 12 wk	Muscle and fat volumes: MRI @ pre-op and 12 wk Quads and hams isokinetic strength: 90°/s, 180°/s, and 240°/s through 0–60° flex comparing the operated with contralateral limb @ 1 wk pre-op and 12 wk	Less deficit in muscle strength in 20 Hz group than in 80 Hz group @ 180°/s and 240°/s comparing operated with contralateral limb No difference in quads peak torque deficit @ 12 wk comparing pre- with post-op No effects on hams (less affected by strength loss) Less fat accumulation in NMES 20 Hz No significant between-groups differences in all other outcomes	The 20 Hz group received 4 times the number of quads contractions. Neither 20 Hz nor 80 Hz is ideal for muscle strengthening. 2 h of Ex is unusually high. No CON group for comparison.
Ross (2000)¹⁰¹ RCT N=20 enrolled; N analyzed nr Included in SR⁹²	ACL recon 1 wk post-op Aged 22–42 yr NMES (n=10): NMES+CKC Ex CON (n=10): CKC Ex Standard rehab both groups from POD 1	4×8.9 cm 2 channels Electrodes: on prox VL and distal VM and hams (prox medial hams and distal biceps femoris	Symmetric biphasic PC 50 Hz 200 μs ON:OFF 15:35 s, 3 s ramp-up Amplitude max tolerable No simultaneous voluntary contraction with NMES	30 min/d 5 d/wk 3 wk Then 3 d/wk for 2 wk	Anterior joint laxity: KT-1000 Unilateral squat to max knee flex Lateral step-up: max 15 s Anterior reach test: distance reached @ 0 and 6 wk	Better unilateral squat Better lateral step test @ 6 wk No significant between-groups differences in all other outcomes	Pilot study intended to determine reliability of outcome measures.
Sisk and colleagues (1987)⁹⁷ RCT N=24 enrolled; N=22 analyzed Included in SR¹¹⁶	ACL recon Knee immobilized in flex post-op NMES (n=11): NMES POD 4–5+Ex CON (n=11): Ex Ex both groups from POD 2	10×5 cm 1 channel Electrodes through window in cast: 5 cm prox to patella and 3 cm distal to femoral triangle	Symmetrical biphasic PC 40 Hz 300 μs ON:OFF 10:30 s Rise time 0.5 s Amplitude self-adjusted to max comfortable No simultaneous voluntary contraction with NMES	8 h/d 7 d/wk 6 wk	MVIC quads @ 70°–80° flex: KinCom dynamometer—highest of 3 max trials, ratio of torque to body weight @ 7, 8, and 9 wk	No significant between-groups difference in any outcomes	8 h/d, 7 d/wk atypical; fatiguing protocol might account for lack of benefit.
Snyder-Mackler and colleagues (1995)¹⁰² RCT Multicentre trial N=129 enrolled; N=110 analyzed Included in SR⁹²	ACL recon (mixed grafts—e.g., Achilles, patellar semitendinosis, or gracilis) NMES (n=31): NMES high intensity NMES (n=25): NMES low intensity NMES (n=20): NMES mixed high and low intensity CON (n=34): high- intensity Ex from 1 wk post-op	1 channel High-intensity group: 8.9 cm diameter Electrodes: on proximal and distal VL Knee flex 65° Low-intensity group: 4×5 cm Electrodes: on proximal and distal VL Knee flex 90°	High-intensity group: 2500 Hz AC 75 Hz burst rate ON:OFF 11:120 s Low-intensity group: Waveform nr; PC 55 Hz 300 μs ON:OFF 15:50 s 15 min Amplitude max tolerated for each contraction No simultaneous voluntary contraction with NMES	High-intensity group: 15 contractions 3 d/wk 4 wk Low-intensity group: 15 contractions QID 5 d/wk 4 wk	Quads strength: NMES superimposition technique @ 4 wk Knee flex during stance @ 4 wk	Greater strength with high-intensity NMES and mixed-intensity NMES No effect using low-intensity NMES or Ex No significant between-groups differences in all other outcomes	Compliance monitored Suggests NMES using AC at high intensity is more effective than NMES using portable, battery-powered, low-frequency devices at lower intensity; however, it is important to note that groups also used different duty cycles, no. of contractions, and knee positions.
Snyder-Mackler and colleagues (1994)¹¹² Analysis of a sub-sample of N=52 from RCT reported in Snyder-Mackler (1995) ⁹⁵ Included in SR¹¹⁶	ACL recon 2–6 wk post-op Aged 15–43 yr NMES (n=31): NMES console device NMES (n=21): NMES battery-powered device Standard rehab all groups from wk 1	Console device: 10.2×12.75 cm 1 channel Electrodes: on VM and prox VL Sitting knee flex 65° Battery device: 4×5 cm Electrodes: on VM and prox VL Sitting knee flex 90°	Console device: 2500 Hz AC 75 Hz burst rate 400 μs 50% duty cycle ON:OFF 11:120 s Battery device: Waveform nr; PC 55 Hz 300 μs 15 min ON:OFF 15:50 s Intensity max tolerated for each contraction No simultaneous voluntary contraction with NMES	Console device: 15 contractions 3 d/wk 4 wk Battery device: 13 contractions; QID 5 d/wk 4 wk	Quads strength: MVIC ext torque compared with uninvolved quads expressed as % Using burst superimposition technique	Linear relationship between quad torque and training intensity Training with medium-frequency units resulted in greater torque	Training intensities monitored. Suggests training with console units may be superior to that with portable units, but caution is required in interpretation because the parameters were different.
Snyder-Mackler and colleagues (1991)¹⁰³ RCT N=10 enrolled; N=10 analyzed Included in SR⁹²	ACL recon 3–6 wk post-op Aged 18–28 yr NMES (n=5): NMES+Ex CON (n=5): Ex Ex=15 co-contractions of 15 s duration @ 60–90° flex 2×/d, 7 d/wk	Electrode size nr 1 channel Electrodes: 4 on quads VM and VL and on hams distal short head of biceps and proximal medial hams Sitting knee flex 60°	2500 Hz AC 75 Hz burst rate 50% duty cycle 400 μs ON:OFF 15:50 s; ON time included 3 s ramp Amplitude max tolerable, increasing each contraction No simultaneous voluntary contraction with NMES Monitored with Cybex to ensure no net ext torque	15 co-contractions of hams and quads 3 d/wk 4 wk	Gait analysis: motion analysis Quads strength: KINCOM isokinetic @ 90°/s and 210°/s; max peak and average torque over 3 trials Joint laxity: KT-1000 @ 4 wk	Increased quads strength Better gait parameters (cadence, stance time, and walking velocity) No significant between-groups differences in joint laxity	Log book used to check compliance with Ex. CON group also seen 3 d/wk to check Ex. Caution required in interpretation because of the small number of subjects.
Taradaj and colleagues (2013)¹¹⁰ RCT N=80 enrolled; N analyzed nr	ACL recon Soccer players 6 mo post-op NMES (n=40): NMES+Ex CON (n=40): Ex Both groups received standard 6 mo rehab post-op	8×6 cm 1 channel each leg Electrodes: on quads bilaterally, exact location nr @ knee flex 60°	2500 Hz AC 50 Hz burst rate ON:OFF 10:50 s 55–67 mA Amplitude set to produce a strong, visible motion, but no ROM was permitted during stimulation No simultaneous voluntary contraction with NMES	10 contractions 30 min BID (3 h between treatments) 3 d/wk 4 wk	Strength: tensometry Muscle circumference: tape measure Ease of motion: goniometry pendulum test @ 1 and 3 mo	Increased strength Increased thigh circumference No significant between-groups differences in goniometry	Blinded assessor Large sample size Ex programme is not applicable to early post-op period: aggressive nature of Ex would likely jeopardize the recon. This study supports starting NMES late (i.e., 6 mo) in athletes who have not regained strength as expected.
Wigerstad-Lossing and colleagues (1988)¹¹³ RCT N=23 enrolled; N=26 analyzed Included in SR¹¹⁶	ACL recon (patellar tendon) POD 2 NMES+Ex (n=13) CON (n=10): Ex (10 min/h, 8/d)	4×10 cm 1 channel Electrodes through window in cast: 5 cm distal to inguinal ligament and 10 cm proximal to patella base on VL	Asymmetrical balanced biphasic PC 30 Hz 300 μs ON:OFF 6:10 s +2 s ramp up Intensity max tolerated (65–100 mA) Simultaneous voluntary quads contraction	4 sets of 10 min 10 min intervals between sets (132 quad contractions) 3 d/wk NMES group instructed to reduce home Ex to 50% on NMES days	Knee extension strength: Cybex MVIC @ 30° and 60° flex Isokinetic @ 30°/s and 180°/s @ pre-op and 6 wk CSA: CT @ pre-op and 6 wk Oxidative and glycolytic enzyme activity: biopsy @ pre-op and 6 wk	Less reduction in isometric strength Less reduction in CSA Less decrease in oxidative and glycolytic enzyme activity	Compliance in control group was addressed by attending PT 1×/wk. Results suggest that use of NMES, applied very early post-op, prevents secondary muscle weakness. (Note that in the 1980s, patients were immobilized in a cast post-op for extended periods.)

NMES=neuromuscular electrical stimulation; ACL=anterior cruciate ligament; CON=control; RCT=randomized controlled trial; SR=systematic review; POD=post-operative day; flex=flexion; CPM=continuous passive motion; TENS=transcutaneous electrical nerve stimulation; ext=extension; nr=not reported; PC=pulsed current; ROM=range of motion; recon=reconstruction; PEMF=pulsed electromagnetic fields; VM=vastus medialis; hams=hamstring muscle; MVC=maximum voluntary contraction; pre-op=pre-operatively; post-op=postoperatively; VAS=visual analog scale; MVIC=maximum voluntary isometric contraction; Ex=exercise; max=maximum; quads=quadriceps muscle; EMG=electromyography; BF=biofeedback; prox=proximal; TID=3 times per day; PD=pulse duration; VL=vastus lateralis muscle; SDH=succinate dehydrogenase; Rx=treatment; ADL= activities of daily living; NPRS=numerical pain rating scale; tib ant=tibialis anterior muscle; US=ultrasound; AC=alternating current; RM=repetition maximum; Nm*Min (defined as activity=muscle tension×contraction duration; BID=twice per day; MP=motor point; rec fem=rectus femoris muscle; MRI=magnetic resonance imaging; CKC=closed kinetic chain; QID=4 times per day; rehab=rehabilitation; CSA=cross-sectional area; CT=computed tomography; PT=physiotherapy/physical therapy.