The physiological benefits of aerobic – also known as endurance or cardio – training include improvements in tidal volume (quantity of air the lungs move), blood volume, and stroke volume (quantity of blood the heart moves per beat). It also increases the number of capillaries, and the number and size of mitochondria. All of these contribute to the body's ability to transport oxygen to the working muscle.

Recent research has shown that cardio – but not strength work or interval training – can make rodent brains bigger.

Okay, forget how much that last part sounds like the promise of a 1950 sci-fi film. Let's look at other research.

A long-term study followed 1583 middle-aged men and women with no personal history of either dementia or heart disease for two decades. Before-and-after tests done 20 years apart showed that the ones who had kept in shape tended to have larger brains, while the poorly conditioned participants had lost gray matter.

Holding on to gray matter advances cognitive decline and decreases the risk for dementia. No specific type of exercise was explored in that study, however.

And that's a perfect lead-in to the long-raging debt over Cardio and High-Intensity Interval Training (HIIT).

Fans Of HIIT Always Stack the Deck

Let me be clear: I have nothing against high-intensity intervals. I use them often in my own workouts and when teaching.

But something interesting occasions when staunch advocates of HIIT compare the relative benefits of HIIT with standard cardio.

They tend to cheat.

In the hands of the die-hard HIIT fan, the word “cardio” has become code for lame-o exercise at the lowest levels of intensity. It should come as no surprise that the benefits – if any – of such lame workouts would fall far short of the benefits of HIIT.

And no one challenges the criteria. So let's challenge them with just a few simple facts.

You Can Go Hard AND Long

It's not true that intense training must involve short intervals of, say, 20 to 60 seconds. If you train well aerobically and seriously enough to achieve the aerobic benefits covered above, you can maintain a high level of work for a pretty long time.

Elite marathon runners, for example, run faster than 5-minute-mile pace for 26.2 miles. Most people would find it difficult, if not impossible, to run a single 5-minute mile. It's a fast pace. Elite marathoners do it for a couple of hours.

As Matt Fitzgerald – well-known marathoner, trainer, and author of several books and articles – states, “well-trained endurance athletes really do not have to slow down much as they increase the duration of their efforts. reading magazines on elliptical trainers. ”

Can not We Combine Cardio With HIIT?

The training combination that appeals to me most fits a set of about 8 intents intervals into a long training of moderate or moderately high intensity.

It's not just my personal preference, though. There's evolutionary evidence that this way of training is precisely what we were always meant to do.

In his book Born To Run, Christopher McDougall reveals the blend of morphology, paleontology, anthropology, physics, and math that led to understanding how humans became the greatest distance runners in the animal kingdom.

There's no way this article could do justice to McDougall's fascinating and detailed description of the emergence of homo sapiens over Neanderthals (they were parallel species), and the evolution of humans as supreme hunters hundreds of thousands of years before the creation of the tools we associate with hunting (spearheads, bows and arrows).

A few of the evolutionary changes include upright posture to allow deeper breathing and limit retention of sun heat; the ability to release body heat through sweat, rather than panting like other mammals until they must rest or die of hyperthermia; and the ability to accelerate once the pursued animal has been run to exhaustion.

Human “persistence hunting” was a combination of endurance running primarily, plus some short sprints. Humans evolved to run in conditions that no other animals can match, and it's easier for us.

Good At Endurance (For a Long Time)

Endurance athletes can typically continue into what's considered old age in other sports. In such activities as distance running, they can still out-perform teenagers or 20-year-olds until their mid-60s.

When workouts are always high-intensity, over-training, failure to recover fully, and a high incidence of injury are likely.

Burn-out after constant high-intensity work makes it feel like drudgery, instead of something to look forward to each day. Why not work out in a way that you'd enjoy long-term?

Endurance athletes of other types display similar results. Master's cyclists in their 50s and up often outperform younger cyclists.

So the choice is not really between short, intenet intervals and long, slow cardio with a magazine. The right kind of training combines both.

The cardio, of course, should be hard enough to cause a training effect, not help you catch up on your reading.

That perfect combination is effective, enjoyable, sustainable over the long haul, and entirely in sync with our evolutionary nature.