running after bicycling

A friend came from the other side of Greenville to try out the Clemson triathlon course today--it is only three weeks away. We worked fairly hard on the bike, though not race pace, and did the course in 43:53. That's maybe a minute or two under what my time was last year (they reported bike time combined with the swim-to-bike transition so I don't have an accurate time). Then we did the run course. I wasn't pushing myself and I did it in 34:43--an 11:07 minutes per mile pace. Last year (on a slightly different course) my time was 40:27. But what really puzzles me is how easy it felt, when the 5K on Friday, where I ran a 10:19 pace, felt so hard. I am more caught up on my sleep today, but I biked 34 miles yesterday (not pushing) so it isn't that my legs are more rested. I just seem to run better after I bike. I think that my running style settles down into something more efficient when my legs are somewhat tired.