Yes push/sit "ups" are not a productive use of one's time.
why not
if its after Work and the day is done and you have made your money, why not test yourself with this method to produce more energy to do frivolous things like (pushups)
creating and inventing the energy to do frivolous things is a great acheivement
it brings you to the next level
in other words
if the creative inventive processes work via chanting method ,
you can take this energy to do at your will the most profitable, gratifying, productive, prolific and dynamic things
please bare with me and consider this