Ann:
these biceps exercises sure are tough! The arms are well and truly fried at the end of these last reps. I can ususally get through them, but if I'm real tired I will either:
1) slow the count down so that I still finish the same number of reps as Cathe and crew but just a tad slower (then rewind to join her for the next set, again at my own pace), or
2) I might start to alternate, curl right, curl left, just to keep going, and again, I'll stay with the number of reps Cathe does, just take longer.
See if either of these techniques work for you. Hope so.
Clare