Excerpts from a discourse by our Sri Sri Muralidhara Swamiji
Namakirtan is Mediation - 4
Such japa can be done within the mind in the sitting posture. If we are unable to do this we can do the japa uttering the Nãma loudly; we can do the japa as we walk; we can do japa as we go circumambulating a temple. When practiced in this manner the 'shakti' (power) to do the japa within the mind is earned at a point of time. Doing japa continually in this manner is also called dhyana.