Interesting comparison...

did my elliptical session as planned after work yesterday...

Cross Trainer stats:
time: 30:00
total strides: 3234
calories: 1010 (grain of salt stat but good for comparison purposes)

Garmin HR stats*:
avg HR: 142
max HR: 157

*Time spent in HR Zones:
00:26 [Z1: 93-111]
04:46 [Z2: 111-130]
12:35 [Z3: 130-148]
11:55 [Z4: 148-167]
00:00 [Z5: 167-185]

this was a comparable workout to Saturday's effort with regard to the total strides (3234 v 3242 for Saturday) & "calorie" count (1010 v 1013) yet my HR spent over 4 mins longer in Z2 (04:46 v 00:22) and over 8 mins longer in Z3 (12:35 v 04:25) and no time at all in Z5 (00:00 v 11:51)...my avg HR was 18bpm less and my max HR was 17bpm less...

I still felt I was working at the same intensity - I wouldn't of thought the training effect would have kicked in at the 6th session...interesting...