The first was to set the DF too high, at 153 versus my normal 130 to 132. It felt heavy from the start, but I didn't want to break the (unwritten) rule by changing the DF between intervals and it was only afterwards that it occurred to me that I could have stopped after the first interval and started Sol over again with a lower DF.
My second mistake was to get up and walk around after the 8th interval. I was very out of breath and walking around made me far worse and I really struggled over the last two intervals, which were my slowest at 148 and 146 meters respectively. Overall total was 1521m, which gets me a seat in boat 6 (I think).
Hopefully my back will not suffer any ill effects. I felt really cream crackered after the session and had to walk around slowly for about twenty minutes to cool off.
