Confirming CFTS

Hey guys,

Sorry to keep asking boring beginner questions but I really need to confirm my understanding of the appropriate terminology. Could anyone please give more info/ correct me on any of the following:

3-1-3: Used with weight lifting…3 weeks increased intensity…1 week maintain intensity…drop volume. Is this done with anything else like med balls?

Short to Long: starting with shorter distances and moving up. Progression for sprints only. Does this start in GPP and continue into SPP1? Also do you drop back down to the shorter distances in each SPP? As you work along the S-L programme do the short distances remain when you add on the longer distances?

Just a random question: why is a lot of the core work endurance based? I thought this wasn’t specific or is it more for recovery?

Thanks!