You need to make calisthenics excercises progressively harder instead of endlessly increasing the volume, if you want to increase strength. The pinnacle are pus

You need to make calisthenics excercises progressively harder instead of endlessly increasing the volume, if you want to increase strength. The pinnacle are pushups on one arm, Bruce Lee demonstrated those on two fingers. The book Convict Conditioning contains progressions for several bodyweight excercises.