Aerobic fitness is measured by the volume of oxygen you can process in any given time. This is called your VO2 maximum or VO2max. It’s mostly measured in millilitres of oxygen used per kilogram of bodyweight per minute.
An elite marathon runner might have a VO2 of 80 and an obese, sedentary and very unfit person of the same age around 35.
You mainly get very high VO2 by doing aerobic or cardio training for lengthy sessions, usually in one block; say, an hour or running, cycling or similar activity. But . . . you can also get a reasonably high VO2 — but not as high as a marathon runner — by doing higher intensity exercise for less time. This might involve sprints or middle distance intervals at high intensity, or even workouts like this one in the gym without running at all. Training for team sports can provide this sort of aerobic fitness. Typical VO2 in elite athletes in sports like football (soccer) might be around 60 to 65, with some individuals even higher.
Why You Need Cardio for Health
‘Cardio’ like walking or slow jogging on treadmills is often recommended in heart rehabilitation programs or for the very unfit in order to build up heart and lung fitness. This is much less stressful than doing higher intensity intervals for a shorter time. And regular, moderate-intensity, sustained aerobic exercise conditions other aspects of your body other than your ability to to get fitter faster, which is perceived as one benefit of interval training.
Aerobic conditioning of the longer, slower type builds the small blood vessels called ‘capillaries’, in muscles, — the heart is a muscle — and these are encouraged to grow throughout muscle tissue to facilitate oxygen supply at times of high demand. With this sort of conditioning, your heart has extra blood supply and it gets bigger and stronger as well. For example, in one study, two groups were trained, one doing continuous, cardio type exercise, and the other shorter intervals of higher intensity. The longer, slower cardio group added twice as much capillary capacity as the interval trainers.
This might even be important if you were unfortunate enough to suffer a heart attack. The extra blood supply, called ‘collateral supply’ could save your life.
You will get some of this capillary conditioning with interval training, but the big benefits mostly come from regular, sustained aerobic type exercise — jogging, running, cycling swimming for 30 minutes or more at a session. Naturally, the higher-intensity interval type exercise will improve your anaerobic performance if you need this for sports.
If you’re training for health and fitness, don’t put all of your eggs in the weight training and high-intensity interval training baskets. Find time to fit in some good, old-fashioned cardio.