Can You Get Stronger Just by Imagining It? The Science of Motor Imagery Training

What research says

• Yue & Cole (1992) randomized 30 healthy adults to actual maximal contraction training, imagined contraction training, or no training, for 4 weeks.
• The imagined-training group still gained about 22% strength (vs. ~30% for actual contraction and 3.7% for control), with gains even appearing in the untrained hand.
• A follow-up by Ranganathan et al.
• (2004) replicated the effect: imagined training alone increased finger-abduction strength by ~35% and elbow-flexion strength by ~13.5%, both statistically significant.

What research says

• In Yue & Cole (1992), electrically evoked twitch force — a marker that should rise with hypertrophy — was unchanged across all three groups, meaning strength rose without any muscle growth.
• Ranganathan et al.
• (2004) found that EEG-derived cortical potentials rose in parallel with the strength gains, indicating changes in motor-cortex activity accompanied the improvement.
• EMG correlated only weakly with strength gains, pointing to central nervous system (motor program) adaptation rather than a change in the muscle itself.

What research says

• Clark et al.
• (2014) randomized 44 healthy young adults to 4 weeks of wrist immobilization alone, immobilization plus daily mental imagery of strong contractions, or a no-intervention control.
• The immobilization-only group lost an average of 45% of strength, versus about 24% in the imagery group — roughly half the loss.
• Measures of voluntary activation impairment and cortical inhibition were also smaller in the imagery group.

What research says

• In Ranganathan et al.
• (2004), the physically trained group gained about 53% strength, while imagined-training groups gained only ~35% (finger abduction) and ~13.5% (elbow flexion) — well short of real training.
• The effect of imagined training has only been shown in small, short-term studies and doesn't demonstrate muscle growth or improved movement performance.