I'm using a Garmin Forerunner 405CX watch and following Garmin's Training Plan - Level 2.  Today's Week 2 run was to be 5x2 mins at 10k effort with 60 secs jog between efforts. I understand 10k effort to mean 92-94% of my Maximum Heart Rate (is that the same as Heart Rate Reserve?) of 185bpm, but I could barely reach 170bpm and had trouble sustaining that for 30 seconds, let alone 2 mins! I'm assuming that I'm doing something wrong here. And with my troubled relationship with science and numbers, that doesn't entirely surprise me. Help!

Chimpster: I think my MHR is 185bpm because I measured it with a heart rate monitor. I'll try the 5x2 mins at 10kph; that seems to make sense really.The Garmin training plan tells me that a long run should be 65-75% of MHR, threshold run should be 80-85% of MHR, etc, but on the Garmin Connect site which stores all my activity data,  there's a table with a column for bpm, and a column for %HRR. I was assuming that 122-135 bpm = 50-60 %HRR meant that I should set my watch to ensure my heart beats 122-135bpm if I want to run at 50-60 percent of my MHR. Perhaps I've misunderstood something here!