When concentrating while playing, I often get an unintentional aerobic workout from my body-english - I'm jumpin' - I'm swaying - squating - I'll kick either leg in any directions but usually straight back and this has resluted nailing innocent by standers - nothing bad, usually afrim bump that suprizes both of us. No one's been hurt, a bit embarrassing though.
Twisted my back so much playing one afternoon I has to lay low for a few days - that hurt.