Given that one uses 3-d movements in any case, it should be a wearable technique, else you are prone to oversimplification. So EEG or EMG devices might help after looking into the literature on movement control founded by David Marsden, continued by Bhatia and Mark Hallet. Actually, I can barely imagine these movements carried out in whatever scanner. But the big data companies like Apple will launch themselves in "augmented reality", so there may be resources to draw on. It also may depend on the kind of MA you're willing to study.

Perhaps this paper will be of interest:

Jacini, W. F., Cannonieri, G. C., Fernandes, P. T., Bonilha, L., Cendes, F., & Li, L. M. (2009). Can exercise shape your brain? Cortical differences associated with judo practice. Journal of Science and Medicine in Sport, 12(6), 688-690.