Thanks keeper for the explanation....(and, of course, Mr. Silver for starting the thread). I hit a new high BPM this weekend (the hill only peaked at 19% but in a series of rollers where the longest was 1/2 mile long). I hit the nausea point, but it doesn't sound as bad as Mr. Silver; DH took the route of valor and engaged "La Nona" and got off and walked. Darn...now I found out he probably did the right thing.