I'm not really sure what the problem is; a resting heart rate of 75-80 is actually quite good. Lower is better. :) Your heart rate really isn' an issue unless you have a heart condition or are training as an elite athlete.
Are you adequately fueled? If you are suddenly experiencing a decrease in ability, you may be overtraining.
However, it's not about what others do, it's about what you can do. That's a pretty intense circuit... of course it's going to leave you winded!
Everyone has different fitness levels.
Writer, mother, wife, and breadwinner. I love to run, but running doesn't love me, so I'm switching to my low-impact bike.
I'm not pregnant, just fat: My blog. fatnotpregnant.blogspot.com/
| current weight: 190.6