New insights on mind-muscle connection: Motor imagery concomitant to actual resistance training enhances force performance.

Objectives: Motor imagery (MI) practice has shown substantial benefits on force, but this was mostly demonstrated on force produced by isometric contractions in laboratory settings. Here, we tested a new type of MI intervention to improve force and power in expert athletes.

Design: CrossFit® athletes (n = 100) of national level were randomly assigned to experimental groups who completed a 5-week back squat training program (3 resistance training sessions/week, ~1 h per week). A first group (n = 35) received instructions to perform kinesthetic MI of the concentric phase of the back squat concomitant to its physical execution (MI_CONCENTRIC). A second group (n = 35) performed kinesthetic MI of the eccentric phase concomitant to its physical execution (M_ECCENTRIC). A control group (n = 30) completed the same amount of physical training without engaging in MI (Control).

Methods: Performance was indexed from the 5 repetition maximum (5 RM) squat workload before and after the intervention. Weekly, we assessed squat power using an accelerometer.

Results: MI_CONCENTRIC and MI_ECCENTRIC groups outperformed Control regarding pretest vs. posttest improvements in both 5 RM force and power (R_P² = 0.60, both p < 0.001). The MI_ECCENTRIC group also outperformed the MI_CONCENTRIC group for the 5 RM workload (R_P² = 0.27, p < 0.001). However, subjective evaluations revealed that athletes in the MI_ECCENTRIC group experienced higher effort perception and difficulty to complete the experimental task.

Conclusions: MI practice concomitant to physical training was efficient to improve force on a dynamic multi-joint exercise in expert athletes.