The Life cycle at the gym shows about 12 miles for 45 minutes. Since I try to keep my heart rate in the cardio zone (for me, about 132 bpm), and at the same time keep my cadence at an average of 100, I have no problems logging in 12 miles for 45 minutes on the Lifecycle.

On the trainer, I do the two spinerval videos that I have with great intensity, and also log 12 miles for a 45 minute video. My HRM really tells me how hard I am working.