Unless you are deconditioned, geriatric, or have a heart problem, extended (40-60+ minutes) of pure aerobic activity offers minimal fitness gains. For some people, though, a morning 3-mile jog is a pleasurable wake-up, and pleasure is good. That's recreation, not fitness-training.
You will often see people swimming half-miles of laps, on the elliptical for 45 minutes while reading the newspaper or watching TV, jogging on the treadmill for 60 minutes. If viewed as recreation, that's fine and it might feel good but there are minimal fitness gains to it. Why?
- Aerobic cardio doesn't build strength or burn fat with any effectiveness. Anyway, you don't need to get rid of any fat, do you?
- However, extended cardio does release endorphins so you feel good after. That's not fitness, though
- If you can do a vigorous hour of laps, cycling, elliptical, or jogs, you basically have that down and don't need "slow endurance" work more than once a week or every other week. If you can't do an hour of things like that, you are deconditioned and probably ought to work on it as a component of your conditioning program.
- If the purpose of "cardio" is to build or maintain cardiovascular and pulmonary efficiency, then the long slow cardio does nothing for that. The stress on those organs is too minimal to build stamina.
To improve cardio effectiveness and endurance (except for those in the deconditioned, geritatric, or heart-disease categories) you need to up the intensity and reduce the time spent. That means sprints and other HIIT-style efforts which are anaerobic stressors. Another cardio thing you can do is to vary your cardio work-outs. Doing the same thing repeatedly (eg jogging) becomes useless as your body adapts to that one thing and it becomes too easy.
I say that if you can breathe or talk, it isn't exertion: it's recreation.
My preference for cardio/endurance fitness is to combine it in high-intensity calisthenics classes or high-stress machines like Jacob's Ladder or Stairmaster. I'll do rowing or running sprints too sometimes, but I like those things that address full-body muscular conditioning along with difficult cardio. It's time- efficient to combine the conditioning with the cardio.
