After I do it for a while, my arms get really tired. But the feeling which I had al the day doesn't feel like muscles fatigue. Rather, it is a kind of exhaustion from the inside out , and at all levels: physical, mental, and psychological. I felt drained mentally! Fears and depression came suddenly, too. This could also be due to some kundalini stimulating practices, as I was also doing nauli and navi kriya around the same time.