Sri Chinmoy: For a spiritual person like me, concentration can be done at any moment, at any place and in any position. I can concentrate even while I am running. About fifteen years ago, I was a very good sportsman — an athlete in India. Even while running the fastest hundred meter dash, I used to concentrate. While I was pole vaulting — in the air — I was able to concentrate. So concentration can be done at any moment, at any place, in any position; it need not be done only while sitting.
When the inner being compels us to concentrate, we concentrate. There is no hard and fast rule that one has to concentrate only while standing or while seated in the lotus position. When the inner being inspires us, we aspire and this aspiration can be expressed either in the form of concentration or meditation.