Any repetitive task results in performance impairments over time. The cause of these decrements is typically considered physiologically induced. However, recent studies and exercise physiologist feel these impairments are influenced by the central nervous system.
Transcranial magnetic stimulation (TMS) is suggested to alter the excitation of the movement areas in the brain (corticomotor tracts).
The limits of maximal voluntary rate (MVR) are unknown, but if they are modified centrally, then corticomotor excitability (CME) via TMS could elicit MVR improvements.
This study had two objectives: to show that elementary motor learning can lessen MVR deterioration and that this can be further improved with neruo-modulation (TMS).
What was done
Eleven subjects practiced an index finger movement task after TMS intervention targeting I- wave dynamics (ITMS) and sham TMS intervention, separated by a week, in a pseduo-randomized order.
The ITMS protocol consisted of an intervention stimulus interval of 1.5 ms delivered every 5s for 15 minutes (180 paired stimuli at 0.2 Hz). The sham TMS used a single pulse of TMS, with the single-pulse delivered every 5 s for 15 min.
In both protocols, the subjects practiced a movement task for six 10-s practice sets that involved flexion and extension of the index finger. Electromyography (EMG) was taken in both groups.
Results
There was a significant increase in paired-pulse motor evoked potentials (MEP) during ITMS, while no change was found in the sham TMS. These increases were noted in the 3rd minute and continued upward until the 9th minute. The overall increase was 250% of baseline.
Kinematics improved in both conditions with the sham condition showing no change in CME during or immediately following the intervention.
Discussion
This study found short-term training of MVE task can improve sustainability of a task. CME increased steadily during the trial and lasted 20 min after the bout.
These long-term alterations suggest plasticity-like effects and potential long-term retention.
Practical Implication
This study suggests MVR task, can be improved with a single, repeated-bout practice session. This suggests in swimming, single repetition training is possible in improving cortical plasticity.
Moreover, ITMS potentially enhances this improvement through CME. This could be a potential avenue for motor improvement in the future. However, one must be careful in extending these findings to elite athletes, but it is a step toward motor control training.
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Reference:
- Teo WP, Rodrigues JP, Mastaglia FL, Thickbroom GW. The breakdown in central motor control can be attenuated by motor practice and neuro-modulation of the primary motor cortex. Neuroscience. 2012 Jun 28. [Epub ahead of print]