I went for a walk today, in an effort to get a bit of fitness back and to change things a little bit.  I took my Garmin 800 with me and recorded it with the GPS function.  Sadly, the GPS got lost at one point and has recorded me going to places I know for fact I didn't.  Anyway, I walked 5.14Km @ 6.9Kph, which I think is reasonable for a first effort.  My average HR was much lower than when I'm on the bike, sitting at 127BPM (usually around the 155 mark on the bike).  I walked up Church Rd, which I later learned has a 13 (or was it 15) percent grade.  I certainly wouldn't want to ride my bike up it!