Ipsilateral Transfer of Motor Skill From Lower to Upper Limb in Healthy Adults: a Randomized Controlled Trial

In a single-blind randomized controlled study,45 healthy subjects were randomly allocated to one of three single intervention groups: (1) "Leg Training" group (LT) (15 participants) practiced reaching movement (RM) sequences with the non-dominant left lower limb towards the numbered illuminating switch; (2) "Sequence observation" group (SO) (15 participants) observed the identical sequences of the illuminating switches (Switches Observation (SO) group); and (3) "Nature Movie Watching" (MW) group. (15 participants) watched a neutral nature video. Each subject was asked to attend two consecutive sessions, day after day. The first session included familiarization practice of the motor task, a pretest, a single session intervention (according to group randomization), and a posttest. Subjects participated in two sessions. The second session included a retest, 24 hours after the training. The predefined sequence consisted of six reaching movements in the following order of switches: 1, 4, 3, 5, 4, 2.

Recording apparatus used in tests (pretest, posttest, and retest) and training: A custom-made testing device was set up on a rectangular table with a smooth laminated tabletop of 105 cm × 80 cm and adjustable height. Five switch-led units of 5 cm × 8 cm × 5 cm, each composed of a large push-button switch and a red light-emitting diode (LED), attached to the tabletop in a 38-cm radius half circle, successively numbered from 1 to 5. The system was operated by a desktop computer, interfaced with a data acquisition card of LABVIEW software. The algorithm allowed parameters selection of LED activation (illumination) sequence, duration of RM, the delay between RMs, and the number of RM repetitions. Activation of a specific unit LED was a cue for the subject to reach toward that unit and press the push-button switch. Reaching the switch of an activated unit deactivated it, and the response time, between the activated and deactivated LED, was recorded.

Tests (motor tasks): The non-dominant left arm was tested. Motor task: The subjects performed a sequential movement task on a table with push button switches with lights sequentially turning on to indicate the order. Each switch lit up for 1 second, or until hit. Initially, the participants were required to perform 3 sequences to familiarize themselves with the setup, the task, and the sequence. Then, they performed the pre-test which consisted of two blocks of 5 sequences, i.e. 10 sequences, with a 30s break between blocks. After this, the participants underwent one of the following predetermined interventions groups:

1. "Leg Training" Participants sat on a chair with their left heel resting on the table with the push button switches. They performed 10 blocks of the aforementioned sequence with their leg, with a 30s break between each block.
2. "Sequence observation" Participants observed 10 blocks of the identical sequence with the lights alternating automatically, with a 30s break between each block.
3. "Nature movie watching" Participants watched a "scenic relaxation film" for 10 minutes, with a 30s break after every minute.

Two outcome measures were used: 1. response time (s), 2. failure (%) of the reaching movements, defined as failure to reach the switch in the allotted time (1 sec), or pressing the wrong buzzer.