Influence of mirror therapy and motor imagery on intermanual transfer effects in upper-limb prosthesis training of healthy participants: A randomized pre-posttest study

The effect that a motor skill trained on one side can lead to improvement in the untrained side is called intermanual transfer. Intermanual transfer can help enhance upper limb prosthetic training. To determine the influence of mirror therapy and motor imagery on intermanual transfer in upper limb prosthesis training, a pseudo-randomized clinical trial, single blinded, with a pre-posttest design was used. Forty-seven able-bodied, right-handed participants were pseudo-randomly assigned to two training groups and one control group. One training group undertook an intermanual transfer training program, using an upper-limb prosthetic simulator with added mirror therapy and motor imagery. The second training group completed only the intermanual transfer training program. The control group completed a sham training: a dummy training without using the prosthesis simulator. The program lasted five consecutive days. To determine the improvement in skill, a test was administered before, immediately after, and six days after the training program. Training used the "unaffected" arm; tests were performed with the "affected" arm, resembling the amputated limb. Movement time, the time from the beginning of the movement until completion of the task; hand opening, the duration of the maximum prosthetic hand opening; and grip-force control, the deviation from the required force during a tracking task. No intermanual transfer effects were found: neither the intermanual transfer training program, nor the additional mirror therapy and motor imagery affected prosthesis skills. A limitation of the study was that the training program was applied to able-bodied subjects instead of patients with an amputation. Contrary to previous studies, no intermanual transfer effects were found. Additional mirror therapy and motor imagery did not ameliorate intermanual transfer effects.