How to analyze this design?

#1
Let's say you're measuring performance on a test under these conditions:

A- Control, unstressed
B- Under stress
C- 1 hour after stress occurred
D- 4 hours after stress occurred
E- 1 day after stress occurred
F- 2 days after stress occurred

Every group is an independent sample set. Not a longitudinal design.

You expect a difference between A and B, but you are not expecting any of the other groups to be different from the control. Indeed this is what you find. How do you analyze?

Do you decide in advance to make planned comparisons, comparing each experimental group to the control and that's all? Or do you run a one-way ANOVA, then perform post-hoc comparisons? Would this design make it more difficult to detect a significant effect using ANOVA even if there's an A-B difference, since there are so many groups equivalent and indeed hypothesized to be so?