Expertise-driven differences in drummers' wrist-muscle motor unit behaviour.

In order to improve their performance, musicians devote thousands of hours to practising their instrument. However, how practise shapes the behaviour of muscles involved in music-making is not yet fully understood. Using surface electromyography, we report the muscle spike shapes of twenty-two drummers with different levels of playing experience, who performed a uni-manual isochronous drumming task at five different tempi. We used Bayesian mixed effects models to predict the mean (i) Spike Frequency, (ii) Spike Duration, and (iii) Number of Peaks per Spike in the Flexor Carpi Ulnaris and Extensor Carpi Radialis wrist/forearm muscles, and how these parameters vary with expertise (Cumulative Life Practice time; CLP, in hours). As to be expected, participants with more drumming experience showed better overall technical drumming performance (i.e., less variable timing) and less strike velocity asymmetries between hands. Furthermore, higher CLP - mediated by muscle, arm, and tempo - predicted greater Mean Spike Frequency, shorter Mean Spike Duration, and fewer Peaks per Spike. These findings suggest that the long-term training undertaken by individuals involved in drumming may contribute to changes in muscle activation patterns which are characterised by overall more efficient muscle usage. The results provide new insights with respect to practice-related muscle activation adaptation in drumming.