I agree with Mike on this one.
Another point to keep in mind is that the HH and IH races are very different in terms of the rhythm pattern required. This makes it difficult for an athlete to train both patterns, let alone in the same day. Under an ideal situation, I'd suggest splitting the HH and IH work into different days, preferably with the IH work earlier in the week as long as you can get enough recovery to do HH work later.
If you have to do both in the same day, then absolutly go with what mike said above, with doing the HH speed work first and the IH longer work second.