Q&A: How a Little Exercise Brings Big Benefits

New York Times columnist and author Gretchen Reynolds explains in her new book why you don't need to train for a marathon to benefit from exercise. And she sings the praises of "fartleking." What's that? Read on.

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Gretchen Reynolds writes the New York Times’ “Phys Ed” column and has been a devotee of physical exercise — particularly running — for decades. In her work, she’s discovered that while inactivity can drastically shorten the healthy lifespan, most of the benefits of working out don’t require hours of effort or marathon-type training.

Healthland spoke with the author of The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer about how to get the most out of the physical activity that you can actually fit into your busy schedule.

Healthland: What surprised you most when you looked into the science of exercise?
Reynolds: In all honesty, [it] was how little physical activity can make a very profound difference physiologically.  That did surprise me. I used to run marathons and like a lot of people, I really did think you had to run [and] your exercise had be fairly strenuous for a long period of time to get meaningful benefits. The science is very clear that that is just not true.

So, what’s the least you can get away with?

The very least you can do is probably just standing up, which I am doing as we talk. I now stand during almost every telephone conversation because it’s an easy time to do it.  The science is very persuasive that just not sitting for a long time makes some difference.

But, certainly at least 20 minutes a day makes a truly profound difference in your health and dramatically reduces the risk of a whole host of diseases, particularly diabetes, heart disease and dementia, as well as cancer.

(MORE: Exercise Keeps Muscles Young, Even in Elderly Heart Patients)

Do you have one of those standing desks and can you actually work standing up?

I bought a music stand. It’s very cheap. I can read papers I need to read.  I  didn’t invest in [anything] expensive.  It’s very easy actually to coordinate your office so you can stand up occasionally.

I can’t sit still for that long anyway.

There is very good science suggesting that fidgeting improves your overall  health. It has been shown to raise  V02max, which is a measure of aerobic fitness.   You can burn several hundred calories a day if you fidget.

And yet we tell kids to sit still all the time.

I spoke with a physiologist and he wishes teachers would stop saying that. Kids who are moving are ultimately better able to pay attention and they appear to do better on tests. The human body at any age does want to be in motion.  Fidgeting may be the body’s response to being told to sit still.

So, are ab exercises like crunches and sit-ups actually bad for you?

Crunches are okay if you do just a do modified crunch.  A full sit-up has been shown to be hard on the back and  even a crunch if you pull up very far is more likely to be damaging to your back than good for your abdomen.

The way to do it is to lie on back with your knees up, put your hands palm down underneath the lower back and lift your head and shoulders a little way off the ground. Imagine that your head and shoulders are on a bathroom scale and lift up just enough to make the weight go to zero. You don’t need to go higher and you are more likely to hurt your back if you do.

Doing things to make your core stable is very good for your back and waistline, but what you do not need is six-pack abs. There’s no functional  reason to work for that. If you want to look good, that may have its place, but if you want a healthy back and healthy core, you try and work the muscles all around the spine and that does not require a lot of effort.

Side planks are really good, but a full sit-up is not good.

What are the benefits of strength training?

That has a lot of really important effects, especially as you leave your 20s behind. You  start losing muscle mass by your 30s and early 40s, and the only way to maintain that muscle mass is strength training. Endurance training does not do that.

Strength training will ensure that you maintain as much muscle as you can and that has all sorts of important physiological implications.  One is that muscles are the biggest users of blood sugar, so you are less likely to get diabetes and other diseases like heart disease. You will maintain your  independence through middle age and longer.

What effects does exercise have on the brain overall?

They are so wide-ranging. That impact is probably what keeps me exercising every day. Many of us were taught that we were born with a certain number of brain cells and will never have any more. That is absolutely untrue. We all will continue to create brain cells throughout our  lifespan. But if you exercise, you’ll create twice as many. Even really quite mild exercise— like going for a walk for 30 to 40 minutes four times a week— means that you will have a larger hippocampus, which is related to memory and learning. You will have more volume there because you are creating more brain cells, and people who exercise do perform better at every age.

(MORE: Is Exercise the Best Drug for Depression?)

And yet the stereotype of the intellectual has typically not been of a fit person..

In fact, kids who are more aerobically fit perform better academically. Even if you just go for a walk before a math test, you generally perform better. The differences are most profound in people after 40 because you do start to lose volume in the hippocampus beginning in the 40s and pretty dramatically after that. If you can be building brain cells there, it has a really demonstrable effect on your ability to think well into your 80s. And it costs almost nothing and it’s really easy.

What about stretching?

That’s the topic people are most passionate about. I get more angry letters from people who love stretching than about anything else.  The science suggests very strongly that static stretching, which is what most people think of as stretching, like reaching over and touching your toes and getting into some position and holding it, [isn't helpful].

Most people were taught to do that before starting their actual workout. The science suggests that it is, in fact, counterproductive. The brains senses that you are about to overstretch that muscle and sends out a message that in fact tells the muscle to stop contracting so hard and then you cannot perform as well in your next exercise bout. You can’t jump as high or run as fast.

So static stretching before exercise appears unwise. The evidence suggests that it doesn’t do a whole lot afterwards, but it probably won’t hurt.

Is warming up equally problematic?

It does appear to be important for reducing the chances of injury, but that means literally warming up the tissue. The best way to do it appropriately is to do a truncated version of what you’re about what about do. So if you’re running, start with a walk or easy jog. That raises the temperature and gets the range of motion improved in the knees and hips.

And, um, what is a fartlek?

My teenage sons love to go out and say they’re [doing that]. [The word comes from the Swedish for “speed play”]. It’s a way to occasionally increase the intensity of your workout. If your goal is to improve athletic performance, you do need to increase intensity and the best way to do that is through some form of intervals, which I hate but you do need to do occasionally if you want to get faster and fitter.

So, fartlek is an easy informal way to incorporate intervals into regular training.  If you are a runner, you look for a tree maybe 100 yards away and speed up, sprint to the tree and then slow down. It’s a very informal approach to interval training: you don’t set your watch for one minute on, and it’s fun, and you can tell someone you were fartleking and can say that in polite company.

Why are there so many exercise fads?

I think it’s in part because until fairly recently, exercise was not put to the test scientifically. A lot of exercise advice came from PE teachers or someone who tried something and it worked for them and then it would become an entrenched myth.

A couple of really interesting overarching truths are that every single person is different in how they respond and genes play a much bigger role than has been acknowledged, even in terms of whether you respond well to exercise at all. Some respond enormously to endurance training, they get much fitter and lose weight. Some respond to weight training. Some do not.

If you’re not getting the response you want, it’s not just your fault. Everyone’s body will respond to some kind of activity.

So how should someone who hasn’t been exercising start?

Put on whatever shoes you find comfortable and walk around the block. If you can do that comfortably and that feels okay, you will have generated so many physiological benefits already. It’s really good for the human mood to get out and move around.

Do that a couple of days in a row, and then do it twice.  Call it going for a walk, it doesn’t have to be quote-unquote exercise, or training. It’s almost certain that you will feel better and you will have reduced your risk about 20% for diabetes, heart disease, dementia, cancer and premature death of all types. That requires no training, equipment or monetary investment. It could make an enormous difference in American public health if we can convince people that very small amounts of activity can change your life.

(MORE: Study: A 20% ‘Fat Tax’ Would Improve Public Health)
Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.