Table 1.
Studies investigating the EMG activity during motor imagery.
| Study | Number of participants | Motor task | Main findings |
|---|---|---|---|
| LACK OF MUSCLE ACTIVITY DURING MOTOR IMAGERY | |||
| Decety et al. (1993) | n = 6 | Leg contraction to press and release a loaded footplate | No change in phosphocreatine concentration or in pH during motor imagery |
| Demougeot and Papaxanthis (2011) | n = 17 | Vertical arm movements | No arm muscle activation during motor imagery |
| Gentili et al. (2006) | n = 40 | Pointing arm movement | No EMG activity during motor imagery |
| Gerardin et al. (2000) | n = 8 | Auditory-cued hand movements | Surface EMG did not detect any muscle activity during motor imagery |
| Gueugneau et al. (2008) | n = 9 | Pointing arm movement | No EMG activity during motor imagery |
| Hanakawa et al. (2008) | n = 13 | Finger tapping sequence | Surface EMG was monitored during fMRI recordings to confirm the absence of muscle activity during motor imagery |
| Jackson et al. (2003) | n = 9 | Foot sequence task | No significant difference in the EMG signal between imagery and baseline conditions, showing that the patterns of cerebral activation during fMRI recordings are not due to movements |
| Kleber et al. (2007) | n = 16 | Singing of an Italian aria | No difference between baseline and imagined singing |
| Lafleur et al. (2002) | n = 9 | Foot sequence task | EMG recordings showed no change in muscle activity during scans compared to baseline levels |
| Lim et al. (2006) | n = 13 | Arm movement | No EMG activity during motor imagery |
| Lotze et al. (1999b) | n = 10 | Making a fist | Low EMG activity, which did not differ from the baseline, was a precondition before fMRI recordings |
| Lotze et al. (2003) | n = 16 | Performance of Mozart’s violin concerto in G major | No observable differences between motor imagery and rest |
| Mulder et al. (2004) | n = 37 | Abduction of the big toe | No EMG activity during motor imagery |
| Mulder et al. (2005) | n = 31 | Squat movements with additional weights | EMG activity recorded during motor imagery did not differ from baseline |
| Naito et al. (2002) | n = 10 | Palmar flexion and dorsiflexion of the wrist | No EMG activity in the motor imagery condition |
| Personnier et al. (2008) | n = 28 | Arm movements in the sagittal plane | Muscle activation patterns are very similar between motor imagery and rest conditions |
| Ranganathan et al. (2004) | n = 30 | Isometric little finger abduction and elbow flexion | Muscle activity during motor imagery was near zero |
| Roosink and Zijdewind (2010) | n = 20 | Finger tapping sequence | No EMG activity during motor imagery |
| Shick (1970) | n = 10 | Volleyball serve skill | No EMG activity during motor imagery |
| Yahagi et al. (1996) | n = 7 | Wrist flexion | No EMG activity during motor imagery |
| Yue and Cole (1992) | n = 30 | Isometric little finger abduction | No EMG activity during motor imagery |
| Zijdewind et al. (2003) | n = 29 | Ankle plantar-flexion | No EMG activity during motor imagery in the majority of the participants. When little EMG activity was recorded, participants were asked to concentrate until being able imagining the movement without muscle activation |
| MUSCLE ACTIVITY DURING MOTOR IMAGERY | |||
| Bird (1984) | n = 5 | Motor imagery of a past athletic event (including riding, rowing, swimming, water skiing, and basketball) | The EMG configuration during motor imagery mirrored that observed during actual practice |
| Bonnet et al. (1997) | n = 26 | Foot pressure on a pedal | EMG activity weakly increased during motor imagery |
| Boschker (2001) Bakker et al. (1996) | n = 39 | Arm lifting movements (biceps curls) | Significant EMG activity is recorded in the muscles contributing to the contraction. Greater muscle activity in the active than in the passive arm, and greater biceps activity when imagining lifting a heavy compared to a light weight |
| Dickstein et al. (2005) | n = 15 | Rising on tiptoes | EMG activity was recorded in six participants in at least one of the target muscles |
| Gandevia et al. (1997) | n = 12 | Range of simple and complex movements (e.g., flexions/extensions, handwriting, walking, threading a needle…) | Imagery increased background EMG in the involved muscles. In some occasions, spindle discharge also increased |
| Guillot et al. (2007) | n = 30 | Biceps dumbbell curls | The magnitude of EMG activity is correlated to the mental effort required to imagine the movement. EMG patterns during imagery of concentric, isometric, and eccentric contractions mirror those observed during actual movements. EMG activity is recorded in agonist, antagonist, synergist, and fixator muscles |
| Hale (1982) | n = 48 | Biceps dumbbell curls | Internal imagery perspective produced greater biceps activity than the external imagery perspective |
| Harris and Robinson (1986) | n = 36 | Arm lifting | Significant EMG activity is recorded in the muscles contributing to the contraction. Greater EMG activity during the first-person than during the third-person perspective |
| Hashimoto and Rothwell (1999) | n = 9 | Wrist flexion and extension | Larger EMG responses in flexor and extensor muscles during imagined flexions and extensions, respectively |
| Jacobson (1930, 1932) | The number of participants varied among tasks | Biceps dumbbell curls, bending the forearm, sweeping, climbing a rope | EMG activity was recorded in the specific muscle involved with the imagined activity |
| Jowdy and Harris (1990) | n = 38 | Juggling task | Increased muscle activity during motor imagery. No effect of the imagery ability on the magnitude of muscle activity |
| Lebon et al. (2008) | n = 30 | Biceps dumbbell curls | The median frequency of EMG power spectrum in agonist and antagonist muscles was significantly higher during motor imagery than during baseline |
| Li et al. (2004a) | n = 9 | Flexion and extension movements of the fingers | EMG activity was recorded in the finger flexors in four participants |
| Livesay and Samaras (1998) | n = 30 | Tightly squeezing a hand-size rubber ball | Increased EMG activity in the dominant forearm |
| Lutz and Linder (2001) | n = 160 | Dart throwing | Greater biceps EMG activity was recorded when imagery instructions included assertions about behavior, such as motor actions and visceral responses |
| Shaw (1938) | The number of participants varied among tasks | Range of complex movements (e.g., flexions/extensions, handwriting, walking, threading a needle…) | Increased EMG activity during motor imagery was distributed across different muscle groups including those not directly related to the corresponding movement |
| Slade et al. (2002) | n = 60 | Biceps dumbbell and manipulandum curls | EMG activity was significantly greater for both curls in the active arm during motor imagery when compared to baseline |
| Suinn (1980) | n = 1 | Skiing a downhill race | Recorded muscle patterns were strikingly similar to those observed during actual practice |
| Wehner et al. (1984) | n = 27 | Contour tracking arm task | Similar frequency distribution in the power spectrum during actual practice and motor imagery |