Step Away From the Treadmill
by Lou Schuler, Cassandra Forsythe, and Alwyn Cosgrove
The following article was excerpted from "The New Rules of Lifting for Women," written by Lou Schuler, Cassandra Forsythe, and Alwyn Cosgrove:
This is the part of the book where you start to wonder if maybe I'm the victim of too many protein shakes. I'm going to argue that steady-pace endurance exercise — what most of us refer to as "cardio" or "aerobics" — is overrated as a tool for fat loss. But before I do, let me point out that I'm not disputing any of the facts that are indisputable. Does endurance exercise burn calories? Sure. Does it contribute to a longer, healthier life? Absolutely.
I'm not out to demonize anyone's favorite type of exercise. I just want to make the case that a comprehensive strength-training program — such as the one Alwyn Cosgrove designed for The New Rules of Lifting for Women — gives you plenty of exercise, including exercise at high levels of intensity, and thus delivering all the benefits you want from endurance exercise without requiring very much of it.
Defining the Problem
"Aerobics" is a made-up word, coined by Dr. Kenneth Cooper, a former college track star, to promote steady-pace exercise. Here's what he wrote in Aerobics, his 1968 bestseller:
"I'll state my position early. The best exercises are running, swimming, cycling, walking, stationary running, handball, basketball and squash, and in just about that order. Isometrics, weight lifting and calisthenics, though good as far as they go, don't even make the list, despite the fact that most exercise books are based on one of these three."
Cooper believed that endurance training was the key to everything. It was a counterintuitive idea, but unlike so many other leap-of-faith notions that arose in the 1960s ("tune in, turn on, drop out"), it gained a permanent foothold in science and practice. I call it "counterintuitive" because the human species isn't really designed for long-distance runs. We evolved to walklong distances — that's how our ancient ancestors put food on the table, before they figured out retailing — and to run really fast when we must. We're good at start-stop activities involving lots of different speeds and changes of direction, which is why human children instinctively play games like "tag," why human adults invent games like basketball and soccer, and why fighting sports like boxing and tae kwon do have rounds of several minutes, rather than continuous action until one fighter wins.
What we aren't good at, by nature, is jogging or swimming at a steady pace for longer than a few minutes.
And yet, that's what Cooper and many who followed his example have spent four decades telling us we should do.
To be fair, it's hard to make the argument that our species evolved to do sets of bench presses or deadlifts, either. So maybe it's facetious to take any aspects of modern life, including our exercise routines, and put them into a prehistoric context. I'm just trying to make the point that the ability to do anaerobic exercises — lifting heavy things, running fast, jumping, climbing, fighting — was vital to the survival of our species. Being able to jog for an hour at a specified percentage of your maximum heart rate wasn't.
The word "aerobic" refers to the aerobic energy system, one of three ways your body can fuel movement. You use your aerobic system constantly, whether you think about it or not. As long as you're breathing easily, whether you're working, sleeping, doing chores, or exercising, you're using it. That is, you're using oxygen to burn a combination of fat and glycogen (the form of carbohydrate your body uses for energy) to keep your body functioning.
Generally, the healthier you are, the higher the percentage of fat you'll burn at rest. If you're obese and/or diabetic, you'll burn more glycogen and less fat. A perfectly healthy woman would burn just under 60 percent fat and just over 40 percent glycogen most of the time. During exercise, as your heart rate quickens and you start breathing harder, the ratio will shift. All-out exercise is anaerobic — your body can't use oxygen to burn fuel, so it uses chemicals inside your body to generate the energy it needs. When your body needs to fuel movement without oxygen, it uses glycogen, rather than fat, to keep you moving. It has two systems for this: one for very short sprints, up to perhaps 10 to 15 seconds, and the other for longer dashes that last about a minute.
Given what I just wrote, you'd think that exercising with the aerobic energy system must be superior to using either of your two anaerobic systems, since you burn more fat with aerobics. That's where we got the now-very-much-discredited idea that there's a "fat-burning zone" in which we should all exercise.
The amount of fat you burn during exercise matters less than the amount you burn when you aren'texercising. And that's where you start to see some of the hidden benefits of strength training.
If you compare the number of calories burned during endurance exercise to the number burned during strength training, endurance wins pretty easily. Let's say you weigh 140 pounds. If you ran six miles in an hour — a 12-minute-mile pace — you'd burn an estimated 512 calories. (That's including the 100 or so calories you'd burn in that hour if you didn't go running, but that's the same no matter what type of exercise we're looking at.) An hour of serious strength training would burn an estimated 384 calories, or 25 percent fewer. If you're a talented runner clocking eight-minute miles, you'd burn 800 calories, or more than twice as many as you'd burn in the weight room for that same hour.
At first glance, it's easy to see why strength training doesn't slay calories the way endurance exercise does. You spend more time resting in between sets than you do actually lifting, and you certainly aren't burning fat while you're pushing and pulling weights. If you're challenging yourself at all, you're shifting from your fat-using aerobic energy system to your anaerobic systems, which by design run on glycogen.
However, there is more going on.
First is the afterburn — the calories your body continues to burn after the workout is over. Intensity is the most important factor determining post-workout metabolism, so the harder you work in the weight room, the more calories your body will burn afterwards. Let's say that afterburn accounts for an additional 50 calories.
Calories aren't the only consideration. Serious strength training also signals your body to burn a higher percentage of fat calories for many hours after you leave the gym. A really intriguing University of Colorado study, published in the Journal of Applied Physiology in 2003, measured post-workout fat oxidation. ("Fat oxidation" is what happens when your body uses oxygen to turn fat into energy, as it does when you're using your aerobic energy system.) The researchers had a group of men and women do a weight workout one day and an aerobic workout another, with each workout burning about 400 calories.
Fifteen hours after the weight workout, the men and women were burning 22 percent more fat than they did 15 hours after their aerobic workout. The researchers concluded that the exercisers would've needed to burn twice as many calories during their aerobic workout — 800, instead of 400 — to reach the level of post-workout fat oxidation achieved by the lifters.
"Burn More Calories While You Sleep!"
I haven't yet mentioned resting metabolic rate (RMR), which is the speed at which your body burns calories regardless of whatever you happen to be doing at the moment. With men, it's pretty clear that weight lifting increases RMR. The workouts themselves speed up metabolism, in part because the body needs to work harder to repair and rebuild muscles, connective tissues, and bones.
There's also a cumulative effect that comes from adding new muscle tissue. It isn't anything close to the "50 calories per pound of muscle" that some people claim (and I say that knowing full well I've used that figure in articles going back a few years). But muscle is metabolically active tissue, and having more of it certainly forces your body to burn more calories throughout the day and night. The real key, though, is the workouts. The harder they are, the more calories you burn in the next day or two as your body recovers.
Women seem to get a slight increase in metabolism from lifting. It's still in the neighborhood of just 50 calories a day, which isn't a fifth of a Snickers bar. But it shows that the weights are doing something that probably won't happen with endurance exercise.
So if you add it all up, weight workouts give you two and possibly three important advantages over endurance exercise:
1 The afterburn, which might be an extra 50 calories.
2. A higher percentage of fat calories used for energy after the workout.
3. A possible increase in resting metabolic rate, in the neighborhood of 50 calories a day.
Having said all that, I'll acknowledge that you could equal these benefits of resistance training simply by doing more endurance exercise, or doing it at a higher intensity. You'd burn more calories, you'd get a greater afterburn than you would by exercising at an easier pace, and you'd train your body, over time, to use a higher percentage of fat calories during your runs or swims or rides, and to tap into those fat stores earlier in the workout.
Can strength training compete with that? Let me explain why I think the answer is yes.
The Power of Perturbation
Let's slow down for a moment, and ask ourselves why strength training has a bigger effect on metabolism and post-exercise fat-burning than endurance exercise. I think there are two key reasons.
First, there's the inefficiency factor. When you hear your boss use a word like "inefficiency," you know someone in the office will soon be using monster.com as her home page, and you hope it's not you. But when we talk about inefficient exercise, we're talking about routines that require more effort. Your body isn't used to the exercises yet, or hasn't fully adapted to the exercise parameters, and thus has to work harder to get through the routine.
Harder work means better results — you'll burn more calories during the workout, and you'll burn more afterwards, when your body is recovering. In other words, inefficiency is the ideal.
The problem with a repetitive routine, like running or cycling, is that your body makes adaptations and gets progressively more efficient. Those adaptations allow you to go farther and faster in your runs or rides, which is good if your goal is to be an endurance athlete who goes farther and faster. If your goal is to be leaner, then greater endurance isn't really to your benefit; the increased efficiency means you use fewer calories per unit of exercise.
Here's an example:
Back in 1990, researchers at the U.S. Department of Agriculture published a study that compared the effects of diet and exercise, vs. exercise alone, for overweight women. The diet was extreme, cutting the women's daily calorie intake by 50 percent. Both groups of women did six days a week of steady-pace endurance exercise, 35 to 40 minutes a day. The diet-plus-exercise group lost a boatload of weight, as you can imagine — 29 pounds in 12 weeks, on average. Unfortunately, a third of it was muscle, which meant their resting metabolic rates slowed down by an average of 9 percent. The exercise-only group also lost weight, about 13 pounds per person, but only 14 percent of it was lean tissue, and their metabolic rates stayed the same.
But the really, really startling finding is that the first group became so efficient at endurance exercise that they burned 16 percent fewer calories when doing it at low intensities. The exercise-only group also got more efficient, but only burned 8 percent fewer calories. (I should note that the effect disappeared at higher intensities of exercise, which gets back to what I said earlier about the importance of working harder, vs. working longer.)
One more negative effect of chronic endurance exercise:
Your body will adapt to the increased efficiency by selectively shrinking your Type I muscle fibers. Yes, literally, those fibers get smaller as they get better at running or riding. The effect may not be dramatic, but it illustrates how endurance exercise makes your body more efficient, which is to say better at going longer distances with less fuel. If you're trying to get your body to burn morefuel, you can see the problem here.
The same problem arises with strength training, if you forget the "strength" and focus on the "training." Doing high-repetition work with light weights simply makes your muscles more efficient at lifting light weights, which is a surefire way to shrink your muscles and reduce their ability to burn calories.
Heavier lifts, as you can imagine, are inherently less efficient than lighter lifts. They require a bit more energy to perform, but consume a lot more energy as your body recovers from them.
Imagine a lower-body workout that includes leg presses, vs. one in which you do squats with a barbell on your shoulders. For the leg press, you're merely straightening your legs by pushing on a platform that, by virtue of its 45-degree angle, is designed to be easy to push. Contrast that with barbell squats, in which most of your body's muscle fibers are involved in either lifting the weight or keeping your body upright while you lift it. The squatting movement is natural — we do it every time we jump or get up from a chair — but the heavy weight and the difficulty of keeping it balanced on your shoulders make it extraordinarily inefficient.
That inefficiency flips all the switches on what's called your sympathetic nervous system. Again, forget that the word "sympathetic" has warm and fuzzy connotations in most of its uses. When we're talking about our nervous system, "sympathetic" involves the heavy-duty stuff, the stress hormones that trigger our fight-or-flight responses. It's your body's internal equivalent of a smoke detector.
Activating the sympathetic nervous system means your adrenal glands are kicking out adrenaline and other stress hormones, your heart rate and blood pressure increase, and your bronchial passages widen. Your body's core temperature increases, your sweat glands open, your pupils dilate, and you might even get goose bumps.
We're conditioned to think that all these things are bad, but in the context of a workout, they're actually good, since without this festival of stress, you wouldn't be able to work as hard in the weight room. And your body wouldn't burn as many calories, or use as much fat for energy, while you're recovering.
In other words, the real key to successful strength training is metabolic perturbation. You're shaking things up in your muscle cells, your nervous system, and your hormones. The calories you burn while throwing so much of your body into the spin cycle can be modest or substantial, but they're only part of the effect. What your body does afterwards, when it's trying to recover, has at least as big an impact on your physique as the calories used while you're actually lifting.
Could you shake things up with endurance exercise? Sure, if you do intervals, which are a mix of all-out and easy efforts, rather than running or riding at a steady pace. But at that point you're shifting away from your exclusive use of your aerobic energy system, and using one or both of your anaerobic systems.
In other words, you've stopped doing "aerobics" and started doing something that resembles strength training, at least in terms of energy. You're selectively using glycogen-fueled movement with the goal of forcing your body to use more fat while it recovers.
A Decent Interval
I'm not going to get into the particulars of Alwyn's workouts in this excerpt, except to explain why he emphasizes intervals over steady-state endurance.
First, there's metabolic perturbation, which we just discussed. Since it's harder to run or ride or swim fast, it's also more inefficient. That means you shake things up more than you would at a steady pace, which leads to a bigger post-exercise response.
Second, it takes less time. You'd be hard-pressed to go longer than 20 minutes in an interval workout. Thirty minutes is a pretty good interval workout even for an advanced athlete. So you're in and out faster.
As with any type of anaerobic exercise, you force your body to use carbohydrates for energy during the high-intensity intervals. Then you use more fat when you're recovering.
You can do intervals any number of ways, with any combination of work and rest. Alwyn uses a 1:2 ratio here, so you'll go hard for a minute, say, and then rest two minutes. In his experience, that's the most effective protocol for rapid fat loss in women who aren't either elite athletes or absolute beginners. (It's kind of an obvious point, but I'm journalistically obligated to say it anyway: Intervals aren't a good choice for someone who hasn't exercised since high school gym class.)
Now, if you actually enjoy endurance exercise, and would miss it if you couldn't do any, we don't want to discourage you from that. But Alwyn has come up with a unique way of making it more effective.
Do intervals first, to work off some of the glycogen in your muscles. Then step off the track or treadmill or get off the bike or out of the pool. That is, stop altogether for five minutes. Then get back on or in and do some steady-speed exercise at an easy pace.
Why bother? Because after you stop exercising, your body will immediately flood your bloodstream with triglycerides. Women's muscles use more of these fat molecules for energy than do men's. When you start exercising again, you'll have more fat readily available for energy, which means you'll burn more of it than you would if you'd done nothing but steady-pace work.
Does it work? Alwyn says the female clients he trains typically lose two pounds of fat in a week, and six to 10 pounds in a month.
Adapted from The New Rules of Lifting for Women by Lou Schuler, Cassandra Forsythe, and Alwyn Cosgrove. Available at Amazon.com and wherever books are sold.
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