All Cardio is not created equal - but why?

[Rignold]

On days when I am not slogging through C25k, I go to the gym and do a one hour cardio circuit: 20 mins elliptical machine and 20 mins bicycle, both on hill programmes at level 16/12 respectively, then 20 mins on the rowing machine, with no more than 30 secs between each machine. I also do a spin class once a week. It's tough work and I am sweating buckets and breathing hard by the end, but I can do it. Whereas my stamina while out running is far far lower. I'm getting through the runs and progressing, and I realise the running is higher impact than the gym work, but there seems a big discrepancy to me between being able to do 45 or 60 minutes of hard cardio in the gym and gasping for breath at the end of 8 minute slow runs.

Can anyone shed any light on this?

[notbad Graduate]

Although I'm no expert I would guess that it's because when you're running outdoors you have to propel yourself, where as the gym equipment is carrying you with its rhythm. So your effort is much greater which is how you tire more quickly. It will get easier as you progress, and although you sound very fit now you will soon be super fit!

[Tomas Graduate]

I can't explain the physiological reasons, but what you experience matches the relative calorie burns for the different activities. It all depends on weight and speed, of course, but for example I expend 432 calories on running for 30 minutes, whereas when I used to go to the gym, half an hour on the elliptical machine would be around 250.

[melissa22 Graduate]

Have you ever tried swimming with that mix? It's kind of the same thing; you can be super fit from other activities but when you get into the pool you're using a whole other set of muscles and you might as well be starting from scratch. At least in my experience anyways.