Mitochondrial activity declines with age, which may aggravate fatigue and reduce the size and ability of muscles to burn excess blood sugar – a risk factor for diabetes. But this decline was halted and even reversed in the older interval-training group. “After three months of interval training, everything converged towards what we saw in young people,” says Nair.

Regardless of the variation of methods used to report exercise intensities, a consistent pattern appeared with the findings. All of the epidemiology studies that controlled for energy expenditure found greater cardioprotective benefits from the higher aerobic exercise intensities as compared to the moderate aerobic exercise intensities. As a matter of fact, no epidemiological study reported a greater cardioprotective benefit from moderate intensity versus vigorous aerobic exercise. The clinical studies showed very similar results. When energy expenditure was controlled for in the study, the vigorous exercise intensity was more beneficial in altering one or more risk factors to coronary heart disease. Specifically, in relation to the coronary heart disease, the #1 cause of mortality in America, aerobic exercise of a more vigorous type resulted in lower incidence.

There are things that Anaerobic exercise does to your body at a cellular level that just doesn't happen at doing exercise at 50 - 70% of your max HR. That's one reason why no matter how much aerobic cardio exercise one does, it will never increase you anaerobic capacity; however, anaerobic exercise WILL improve your aerobic capacity.