Frustrated

Why is it that I can swim or bike in the right heart rate zone, but when it comes to the run, no such luck. I've been improving, yes, but this morning was quite a let down.
I've been modifying the swim portion of my plan to make it a decent workout for me. The original plan had me swimming something in the order of 200 yds. Thats 4 laps and barely even worth getting wet, so I changed it. Today ended up with a total of 850 yds, 100 warm up, 500 at a decent pace (Race pace, maybe?), 250 interval speed work.
That all went just fine. Afterward I tried a easy run, 25 min, but my normal walking HR (<110) was still elevated by over 20 beats! My run was seriously out of whack. Ended up well above where it runs to anaerobic. Not good.
I figured while I was there I might as well top it off with some good stretching and abs work, with the pilates class. Well I was right about the abs work, but way off on the stretching. The big down side was that I was the only guy in the class, and I don't think my pride could have handled walking out while the rest of the class seemed to be doing just fine. No matter that I just finished an hour or so of cardio, or that this class seemed to be mostly made up of college girls. I suppose if I wasn't lying in a pool of my own sweat and shame, it might have been a decent view. Couldn't tell you. Shame too great.