The usual goal is to make your cardiovascular system and skeletal muscles more able to tolerate oxygen debt (muscles need more than CV system can deliver).
(The usual goal; is; to make your cardiovascular system and skeletal muscles more able to tolerate oxygen debt (muscles need more) (CV system; can deliver; )
The usual goal CV system
is can deliver
to make your cardiovascular system and skeletal muscles more able to tolerate oxygen debt (muscles need more