INTRODUCTION: EMG measurements have been used for many years in competitive swimming to describe muscle recruitment and relate it to dry land training and potential problems such as shoulder impingent and muscle fatigue. In the past, most measurements have been done with systems needing direct wire connections to power and amplification. More recently, new wireless equipment has been developed, permitting full freedom of movement for swimmers. METHODS: Small independent surface units (EMU) (50mm*40mm*15mm, 28g) including muscle electrode, ground and a sender are attached to the skin in a normal way. The signal is transmitted directly to the receiver over a distance of up to 50m. In case of transmission failure or interference due to the water, the EMU has onboard memory for up to 7 minutes recording and seamless transmission occurs after the activity has been completed. The electrodes and EMU can be made waterproof with elastic plastic film if the edges of the film are secured with sport tape. BENEFITS Wireless EMG systems put little restraint on the swimmer, his/her movement, or the environment in which measurements can take place. Recordings have been done not only in controlled situations but during actual competition and even in outdoor pools. Further the EMG signal has less noise than most wire systems. RESULTS: Measurements with this system have demonstrated bilateral muscular imbalance in single leg amputee swimmers and diversity in muscle recruitment patterns for competitive swimmers with visual impairment and swimmers with mild and severe cerebral palsy. It has also been used to examine muscle activity during therapeutic applications such as in the Bad Ragaz Ring Method. The muscle use patterns of specific stroke specialists compared to non-specialists have also been investigated with the equipment. DISCUSSION: This equipment can be used to investigate the International Paralympic Committee swimming functional classification system in more details than has been possible to date. It also makes the application of EMG measurements almost coach friendly.
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