I think there are people on the C25K thread doing both, I am attempting to but doing a poor job at either at the moment!! Well done to getting to week 5 on the running, i'm still on week 3 after a long break.
How does it work if you do both? Do you either run or shred or do both ? Do you have any rest days? Am training for a 10K and need to find a cross training exercise and am considering shreding. I run 3 times a week and was thinking shredding three days and having one rest day?
I did both at the same time, but was, erm, creative in my timings! I only ran once a week, sometimes skipping ahead in C25K if I felt I was progressing fast enough (ie not always taking three weeks to do a week's worth, instead doing two weeks and then progressing to the next week). I shredded three times week, swam one night a week and did Zumba on a Saturday (Tuesdays were my day off!) There were one or two people on the Shred thread I was on at the time who would do a run and a shred in the same day, but I never had the time or inclination for it.
Shred is very ache-inducing the first couple of times, but mostly calms down a lot after that (the first days on Levels 2 and 3 didn't leave me in anything like the amount of pain I was in after starting Level 1).