See his Ten Rings: My Championship Seasons (2003).
A yogi (Sanskrit, feminine root: yogini) is a term for a male practitioner of various forms of the path of Yoga, maintaining a steadfast mind, the process of transcending the lower self through daily practices. In contemporary English yogin is an alternative rendering for the word yogi. This word is often used to describe Buddhist monks or a householder who is devoted to meditation.
The Shiva-Samhita text defines the yogi as someone who knows that the entire cosmos is situated within his own body, and the Yoga-Shikha-Upanishad distinguishes two kinds of yogins: those who pierce through the "sun" (surya) by means of the various yogic techniques and those who access the door of the central conduit (sushumna-nadi) and drink the nectar.