I spent some time yesterday reading up in Blond's, Pammie's journal, and saw my question answered there. Basically, you can sub exercises, but you have to do it intelligently........ie, check exrx.net or equivalent, and make sure that the subbing exercise is hitting the same target groups. I learned that chest flyes are an isolation exercise, not a compound as the DB press is, for example. I think I'll try to stick with the program as written, but not be afraid to sub out. Good!
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5x5, 311, 90" (30" calf work)
Beg: 11:10am
A: BB Squat bar+15kg (50.6lbs)

B: SLDL's w/shrug bar+15kg/20/20/25/25kg (55lbs)

C1: Bulgarian Split Squats bar only (8kg)
C2: Walking Lunges bar only

D: Seated Calf Raise bar+30 +5kg plate on lap (94.6lbs)

End: 12:06pm

Ok, I feel like I've just been initiated into the Secret Club of UP.........read about the hell of the split-squat/lunge combo, but ya just have NO CLUE until you do it! My ass is sore! Already! So what wil tomorrow bring?!?

note on the split squats..... couldn't do them rear leg elevated, or with rear foot upside down....hurt my foot. So I modified just plain split squat......still felt the work!

Will do some walking later, w/ the mutt.