Jo's swing workout (timed sets)

I just finished my swing workout (timed sets) I am doing sets of 2:00 on and :30 sec active rest. I started with a 18# kettlebell but it didn't get my heart rate over 152 (I need my heart rate between 167 and 172) to mimic my run heart rate. So after the first set with the 18# i moved to the 26# kettlebell getting 42 RPM and keeping a heart rate of 167 during swing sets not going below 125 during active rest. I finished 10 sets of 2 mins for a total of 20 minutes. My back began to fatigue around round 8. I am very disappointed in myself and will push harder next week...