1 2 Sensitivity of EMG - EMG coherence to detect the common oscillatory drive to hand muscles in 3 young and older adults 4 5 6

29 Multi-channel surface electromyograms (EMGs) were used to examine the sensitivity of 30 EMG-EMG coherence to infer changes in common oscillatory drive to hand muscles in young 31 and older adults. Previous research has shown that measures of coherence calculated from 32 different neurophysiological signals are influenced by the age of the subject, visual feedback 33 provided to the subject, and the task being performed. The change in the magnitude of EMG34 EMG coherence across experimental conditions is often interpreted as a change in the oscillatory 35 drive to motor neuron pools of a pair of muscles. However, signal processing (e.g., full-wave 36 rectification) and electrode location are also reported to influence EMG-EMG coherence, which 37 could decrease the sensitivity of EMG-EMG coherence to infer a change in common oscillatory 38 drive to motor neurons. In this study, multi-channel EMGs were used to compare EMG-EMG 39 coherence in young (n = 11) and older adults (n = 10) during index finger abduction and pinch 40 grip tasks performed at 2 and 3.5 N with a low and high visual feedback gain. We found that, 41 across all conditions, EMG-EMG coherence was influenced by electrode location (p < .001), but 42 not by subject age, visual feedback gain, task, or signal processing. These results suggest that 43 EMG-EMG coherence is most sensitive to electrode location. The results are discussed in terms 44 of the potential issues related to inferring a common oscillatory drive to hand muscles using 45