Details of the primary studies for muscle strength and activation

StudyTreatmentBiofeedback modeEMG deviceOutcome parameterOutcome valuesES
EMG FB GroupControl Group
[16]

8 weeks (daily)

  • Isometric contraction VL (2 × 5–20 s, 5 s rest)

  • Isometric contraction VM (2 × 5–20 s, 5 s rest)

  • Isometric contraction BF (2 × 5–20 s, 5 s rest)

  • Isometric contraction SM (2 × 5–20 s, 5 s rest)

Visual

  • EMG activity VL

  • EMG activity VM

  • EMG activity BF

  • EMG activity SM

Myomed 134EMG onsetPre:
562.09 ± 55.33
Post:
487.92 ± 46.71		Pre:
548.21 ± 64.76
Post:
538.41 ± 53.58		1.01*
EMG offsetPre:
687.54 ± 75.39
Post:
570.17 ± 62. 11		Pre:
701.23 ± 69.52
Post:
682.31 ± 65.68		1.76*
Knee flexor strengthPre:
38.23 ± 11.03
Post:
84.02 ± 6.95		Pre:
37.42 ± 10.48
Post:
86.04 ± 5.43		0.32
Knee extensor strengthPre:
41.75 ± 10.54
Post:
87. 11 ± 6.54		Pre:
42.92 ± 12.49
Post:
86.39 ± 6.74		0.11
[17]

8 weeks (12 × 15 min sessions)

  • Isometric contraction QF (15 s contraction, 10 s rest, 15 min in total)

Visual & acoustic

  • EMG activity VM

MyoTrac InfinitiElectrical activity VMPre:
207.7 ± 86.7
Post:
342. 1 ± 108.5		Pre:
223.0 ± 82. 1
Post:
347.3 ± 86.0		0.05
[18]

3 weeks (3 times every day)

  • Quadriceps isometric (10 reps)

  • Mini squatting (10 reps)

  • Four-way straight leg raising (10 reps)

  • Knee terminal extension (10 reps)

Visual & acoustic

  • EMG activity VM

  • EMG activity VL

Myomed 932Knee extension strength 60°/sPre:
47.84 ± 17.87
Post:
54.47 ± 17.97		Pre:
50.25 ± 24.2
Post:
62.95 ± 22.8		0.41
Knee flexion strength 60°/sPre:
32.94 ± 14.38
Post:
42.26 ± 23.94		Pre:
27.75 ± 18.9
Post:
40.6 ± 19.79		0.08
Knee extension strength 180°/sPre:
23.68 ± 7.31
Post:
31.89 ± 9.28		Pre:
24.85 ± 11. 1
Post:
35.55 ± 12.6		0.33
Knee extension strength 180°/sPre:
17.10 ± 12.95
Post:
24.10 ± 13.87		Pre:
13.85 ± 11.4
Post:
22.95 ± 15.5		0.08
Knee isometric extension strengthPre:
77.94 ± 28.47
Post:
103.57 ± 63. 1		Pre:
79.3 ± 26.61
Post:
83.35 ± 21.4		0.43
[20]

6 weeks (3 times per week)

  • Shoulder flexion strengthening in a Video Game (5 s contraction, 5 s rest, 10 reps)

Visual & acoustic

  • EMG activity AD

NeuroTrac MyoPlus4 ProShoulder flexion strengthPre:
65.00 ± 20.16
Post:
78.20 ± 22.87		Pre:
70.55 ± 24. 11
Post:
74.74 ± 23.54		0.15*
[21]

8 weeks (3 times per week)

  • Gym ball exercises (10 s hold, 5 s rest, 10 reps)

Visual

  • EMG activity RA

Myomed 932Activation capacity TAPre:
17.69 ± 2.23
Post:
35.09 ± 1.31		Pre:
17.59 ± 2.49
Post:
33.60 ± 2.2		0.82*
[19]

4 weeks (2 times per week)

  • Stretching and strengthening (2 × 8 reps)

  • Shoulder rotators, adductors, abductors, extensors with particular attention to supraspinatus

Visual

  • EMG activity SP

  • Muscle balance

  • Muscle relaxation

mDurance systemRMS SP
limb affected		Pre:
100. 1 ± 13. 1
Post:
171.5 ± 5.1		Pre:
101.2 ± 11.9
Post:
145. 1 ± 12.9		2.72*
RMS SP
limb free		Pre:
172.3 ± 6.0
Post:
182.5 ± 5.2		Pre:
170.9 ± 4.8
Post:
182.6 ± 8.7		0.01
[15]

5 weeks (5 times per week)

  • Quadriceps isometric (5 s contraction, 5 s rest, 10 reps, 3 sets)

  • Knee terminal extension (5 s contraction, 5 s rest, 10 reps, 3 sets)

  • Straight leg raising (5 s contraction, 5 s rest, 10 reps, 3 sets)

  • Isometric hip adduction (5 s contraction, 5 s rest, 10 reps, 3 sets)

Visual

  • EMG activity VM

  • EMG activity RF

Myomed 932Knee isometric extension strengthPre:
9.07 ± 1.87
Post:
13.68 ± 1.99		Pre:
9.42 ± 1.86
Post:
11.06 ± 1.56		1.47*
[22]

5 weeks (2 times per week)

  • Cybex isokinetic knee extension 30°/s, (5 × 5 reps, 2 min rest)

Visual & acoustic

  • EMG activity QM

Ouroboros EMG-1821IEMG activity QMPre:
442.95 ± 95.65
Post:
525.90 ± 112.20		Pre:
407.34 ± 40.81
Post:
454.97 ± 53.20		0.81*
Knee extension peak torquePre:
165.28 ± 30.10
Post:
234.28 ± 52.63		Pre:
165.85 ± 37.08
Post:
211.57 ± 40.57		0.48*
[23]

19 days (5 times per week)

  • Isometric knee extension (6 s hold, 25 s rest, 5 reps)

Visual

  • EMG activity RF

Cyborg J-33Knee extension peak torque trained legPre:
113.26 ± 37.01
Post:
138.59 ± 19.38		Pre:
103.73 ± 25.07
Post:
103.23 ± 27.50		1.49*
Knee extension peak torque untrained legPre:
114.04 ± 35.27
Post:
127.78 ± 32.92		Pre:
97.60 ± 22.46
Post:
95.57 ± 17.52		1.22*

* Significant effects between EMG FB Group and Control Group post intervention. ES: effect size; VL: vastus lateralis muscle; VM: vastus medialis muscle; BF: biceps femoris muscle; SM: semimembranosus muscle; AD: anterior deltoid muscle; RA: rectus abdominis muscle; SP: supraspinatus muscle; RF: rectus femoris muscle; TA: transversus abdominis muscle; QM: quadriceps femoris muscle; IEMG: integrated electromyography; RMS: root mean square