Like all racket sport athletes, badminton players must acquire high levels of skill to be effective in international competition. To achieve these skills, athletes must constantly practice repeatedly over extended periods of time both in closed environments as well as under more open match condition environments. Although the high level of skill is discernable to the eye, from a physiological perspective, we have not been able to measure the effect of repeated practice on the human neuromuscular system. Transcranial magnetic stimulation (TMS) is a well-established, non-invasive technique that can measure the excitability of the human neuromuscular system as well as map the topography of individual muscles (see review Hallet, 2000, Nature, 401, 147-150). A number of experimental TMS studies have shown rapid changes in the human neuromuscular system associated with short-term, simple motor learning tasks (see review Rösler, 2001, News In Physiological Sciences, 16, 297-302). However, long-term changes associated from repetitive skilled movements tasks has not been fully studied. Moreover, as TMS is primarily a tool used in the clinical area, the purpose of this study was to investigate the neuromuscular effects and motor cortex topography following systematic long-term skill practice in a non-clinical population. The study investigated neuromuscular representation of the first dorsal interosseus (FDI) muscle in 3 groups. Group 1 consisted of elite athletes (n=5), including a Commonwealth Games gold medallist and an ex-world champion. Group 2 consisted of social competition (pennant) players (n=5) who played regularly (at least 3 times per week) but do not deliberately practice their skills. Group 3 was a control group (n=10) who do not play any racquet sport. Subjects were tested non-invasively and individually. TMS was delivered using a magnetic stimulator (Magstim, Dyfed, UK). Neuromuscular excitability, measured as motor evoked potentials (MEPs), was recorded using surface electrodes (4mm, Grass). During testing, subjects received a number of stimuli at multiple sites over one half of the scalp (hemisphere), approximately in the area of the motor cortex controlling the FDI. After a short rest interval, the other hemisphere was tested. For both hemispheres, excitability of the muscle was recorded and these measurements where then arranged in a grid system allowing calculation and comparison of the topographic maps of both hands to be completed. In the control and pennant groups, neuromuscular excitability was similar in both hands (? amplitude < 0.5mV between dominant and non-dominant hands) and topographical maps were found to be symmetrical (< 3mm difference medio-laterally between maps). Conversely in the elite group stimulation evoked higher MEPs in the playing side in all athletes (? amplitude 10.5mV vs. 5.7mV, playing vs. non-playing respectively). Further, all athletes demonstrated asymmetry in the topographical representation of the FDI muscle (6mm to 16mm medio-laterally). Although all the elite athletes demonstrated increased excitability and asymmetry between the two sides, no correlation could be observed between the success of the player and the differences seen. The results demonstrate neuromuscular reorganisation as a result of long-term deliberate skilled practice, however the differences that separate world champions from international athletes from a neuromuscular perspective are subtler and requires further study.
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