Mere gymnastics is nutrition for the body.
Now, as to ‘doing’ : Sustained effort ends in effortless being; in other words, what has been attained by constant practice is finally transcended.
Then comes spontaneity. Not until this happens can the utility of hathayoga be understood. When the physical fitness resulting from
hathayoga is used as an aid to spiritual endeavor, it is not wasted.
Otherwise, it is not yoga, but bhoga (enjoyment).