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Body By Science

For those who think that maybe a little too much group think is taking place in the health and fitness world, Body by Science should prove to be a welcome change.

The authors, Doug McGuff and John Little, propose fairly revolutionary fitness techniques supported by LOTS of footnotes to research backing up their claims. And equally refreshing and entertaining, along the way they slay a number of sacred cows of the fitness world.

I can’t say I agree with everything they say, but overall it is a must-read.

The Basic Thesis

At the risk of over summarizing it, the basic thesis of Body by Science is that the greatest gains in health and fitness are accomplished by increasing the body’s muscle mass. And this, they argue, is best accomplished doing resistance training in a very specific way.

Some of the key elements of their approach are:

Large muscle groups, compound movements

The baseline workout of the Body by Science program is what they call “The Big Five”. It is five resistance/weight exercises that each enlist large muscle groups performing compound movements. The five exercises are:

  1. Lat Row (seated cable row, machine row, barbell row)
  2. Chest Press (machine press, bench press, dumbbell press)
  3. Lat Pull Down (pull down, pull up)
  4. Shoulder Press (machine, dumbbell, barbell)
  5. Leg Press (squats, machine leg press)

SLOW movements, one set to failure

They recommend that movements in each exercise be performed VERY SLOWLY. They cite many research studies that show that slower movements are far superior to faster movements on many levels.

A number of factors can influence the actual optimum speed of each repetition, but they should be slow — usually at least five seconds each way. So 5 seconds up, 5 seconds down, or vice versa depending on the exercise. And you should not “lock out” at either end of the cycle – stop lifting at 90% of the way up and at start lifting at 90% of the way down. This keeps the muscle under load the whole time.

The weight they recommend is that amount which will bring you to the point of failure between 45 and 90 seconds. You will not be able to handle the same weight doing slow movements than you could for faster movements.

For each of these five exercises they recommend doing ONE SET to the point of failure. “Failure” means exactly how it sounds. When you reach failure you simply cannot lift the weight even one more time. Then you move immediately to the next exercise.

In the Body by Science approach you don’t count reps. Instead you time each exercise to see how long you go to failure. You should see that time increase as you gain strength, then you add more weight.

Use machines if possible

Contrary to popular belief, resistance training is simply muscle working against resistance, whether that resistance is applied in the form of free weights or machines. But with the Body by Science approach, they advocate machines. The reason is simple: When you’re pushing each set TO FAILURE, free weights present much higher risk of injury.


Another distinctive of the Body by Science approach is the frequency they recommend. Get this: ONCE PER WEEK! And they don’t just pull that number out of a hat. They back it up with references to research.

They argue that when you apply an intense workload to a muscle it needs that much time to repair and rebuild stronger. Working out before that process is complete is counter productive.

The Rationale

You can read much more detailed information in the book, but I’ll summarize some of the thinking here.

Research referenced in the book shows that for the most part, repeated sets of exercise on the same muscle group don’t yield any more gains than one set. Additional sets serve mostly to take up time and increase risk of injury.

One of the authors, Doug McGuff, a medical doctor, points out the similarity between exercise and medication. In medicine there is an optimum dosage and frequency for any given medication. Just because one dosage and frequency has a positive effect, it doesn’t mean that double the dosage and frequency has double the positive effect. It may even have a negative effect.

They maintain that the same is true of exercise. More sets, reps, weight, or frequency doesn’t necessarily yield better results, and at some point more may well be detrimental.

My own experience with the Body by Science approach

If this “slow movements”, “one set”, “lighter weights” stuff seems a little far fetched, TRY IT! I thought the same thing when I first read it. Then I tried it.

There was one acid test that convinced me it was real. At the time I first found this slow reps approach I had already been a regular at the gym for over 10 years. After my very FIRST workout following the Body by Science approach I was so sore it was almost like my first day in the gym!

For the first half of each exercise (the first minute or so) I felt OK, but after that I started quivering. It’s not as easy as it sounds!

And throughout all my resistance training I have nearly constantly struggled with one injury or another – usually in the shoulder area. But with the Body by Science approach using less weights and slower movements I haven’t had another injury yet.

It makes perfect sense. By slowing the movements down you take MOMENTUM out of the picture and make the muscle do more work with less weight. When you move faster, most of the real muscle exertion happens in the very beginning of a movement. After that momentum increasingly takes over.

Weight Loss

That’s all great, but how exactly does the content of Body by Science relate to weight loss? I’m glad you asked!

The book has a chapter entitled “The Science of Fat Loss”. If nothing else about the book would interest you, this chapter would easily be worth the price of the whole book.

In this chapter – probably more than in any other – they completely buck conventional wisdom. They argue convincingly that long, steady aerobic exercises (think running, elliptical machines, StairMaster, etc.) is the WORST WAY to lose FAT, and that resistance training is the BEST WAY to lose FAT.

Slow Twitch/Fast Twitch

To understand why this is the case, you need to know a little about “fast twitch” and “slow twitch” muscle fiber. I’ll give you the overly simplified, but practically accurate version.

Almost all major muscles contain both fast and slow twitch fibers, but in most muscles the slow twitch fiber is the minority tissue. It is the body’s preferred “engine”. It’s not very strong, but it’s efficient and can perform activity for a long time on very little fuel. Any activity you can perform for more than 20-30 minutes is aerobic, and this means it uses slow twitch fibers.

Your body’s “fast twitch” fiber is called into duty to do the high performance activities, like sprinting, jumping, and lifting. Any activity with an intensity level so high that you cannot maintain it for more than a minute or two before you need to recover is “anaerobic”, the opposite of “aerobic”, and uses mostly fast twitch muscle fiber.

So how does this relate to burning fat?

The body is very adaptive and changes to meet the demands placed on it. When you only do aerobic exercise, you are using only “slow twitch” muscle fiber, and your slow twitch fiber becomes more efficient. The body doesn’t want to keep any tissue that isn’t regularly used because it requires resources (like fuel, calories) to keep it alive and well. Since aerobic exercise DOES NOT use fast twitch fibers – at least not much – this allows them to atrophy (shrivel up due to non-use).

It is estimated that one pound of muscle requires 50-100 calories per day JUST TO STAY ALIVE. So even if that pound of tissue does nothing all day, it still requires energy.

So let’s say Fred starts a running program to lose weight. He runs 3-5 days/week increasing mileage and frequency along the way. Well, it’s quite likely that while Fred’s cardiovascular conditioning may improve and he may improve his running performance, but over a few months he could LOSE FIVE POUNDS OF MUSCLE TISSUE! That,s right. Since he’s not using his fast twitch muscle fiber, he could lose it.

Well, if he loses five pounds of muscle, he burns 250-500 calories/day LESS outside that time when he isn’t running! And if you take the high end of that estimate (100 calories per day to keep a pound of muscle alive), he’s probably barely breaking even. He’s running 4 miles per day burning 500 calories per run, but losing muscle tissue which would have burned that 500 calories/day DOING NOTHING.

ALTERNATIVELY Fred could do the kind of exercise that ADDS MUSCLE TISSUE instead of killing it. Let’s say in that scenario he ADDS five pounds of muscle tissue. Well, that additional five pounds of muscle tissue burns upwards of 500 calories per day WITHOUT the running.

And adding that additional muscle tissue using the Body by Science approach requires a much lower investment of time, effort, and wear-and-tear.

I should point out that you’ll see very similar reasoning on my page Weight Training and Weight Loss on this site! No doubt Body by Science has had some impact on my thinking, but I was certainly already arriving at some of these conclusions on my own 🙂

One major oversight…

There is one fairly major oversight in their reasoning of why aerobic activity like running is bad for losing weight. They argue that by running regularly one’s fast twitch fibers are allowed to atrophy.

But this line of reasoning doesn’t show that running CAUSES the fast twitch fibers to atrophy, only that it doesn’t cause the fast twitch fibers to grow. But what if one ran AND performed resistance training? Then it seems logical that the running would burn a LOT of calories while the resistance training causes muscle growth.

Many weight training advocates respond to this by claiming that doing long, aerobic exercises like running should be avoided because it diverts too much of the body’s recovery capacity away from rebuilding muscle tissue.

But I have never seen a single footnote to research to back up this claim, so I conclude that it is just a bogeyman from popular weight training culture :).

The negatives of the book

Before I pick at it let me say that on balance I believe Body by Science is a major positive contribution to the world of health, fitness, and weight loss.

Having said that, there is room for improvement.

Too technical in places

There are significant portions of Body by Science that simply go too deep into the physiological processes. This level of depth and detail is not of any practical use to anyone. And what’s worse is it can seriously distract and/or discourage many readers from getting the gold out of the book.

I SERIOUSLY don’t know how some sections made it past the editors.

What percentage of the audience of this book is ever going to care about the “Krebs Cycle” or “Cori Cycle”? What percentage would care even if they could follow it?

If the authors/publisher feel that this technical information is too important to leave out, they should put it in a companion book or a website.

To readers, when you get to these heavy sections just gloss through at high speed till you reach normal material again.


Body by Science is ANTI-CARDIO. In some cases they make compelling arguments. For instance, in the chapter entitled “The Science of Fat Loss” they make an irrefutable case against “cardio” as the way to burn fat. And they’re RIGHT about THAT.

But to completely denounce the health and fitness contributions of steady endurance training misses the mark.

I admit that Doug McGuff is a scientist and I am not, but I am certain he is wrong about this. Can they truly show legitimate evidence that incidence of cardiovascular disease is not lower in people who engage in regular “cardio”? I seriously doubt it.

They say “Mechanical work is mechanical work… Your heart and lungs cannot tell whether you’re working your muscles intensely for thirty seconds on a stationary bike or working them intensely on a leg press”.

Really? Then why during sprint intervals am I gasping for air and hitting my maximum heart rate? And why does nothing like that happen during leg presses? There’s obviously some significant physiological difference between the two.

Someone pitch in here and help me see where I’m wrong on this.


Since I’ve been a runner all my life I’m naturally going to have an emotional reaction to someone who comes after my sacred cow, but hear me out. The ATTACK on running in Body by Science is totally misguided and lacking in real substance. My defense is not purely emotional.

Running bad for knees?

In Body by Science they say:

Rather than being known in the future as the man who “saved America’s hearts,” it is more likely that [Kenneth Cooper] will be regarded as the man who “destroyed America’s knees.”

Well, as a runner for over 40 years with at least 35000 miles behind me, I have never had even ONE knee problem as a result. I’ve had the occasional pulled hamstring, Achilles tendinitis, etc., but nothing that didn’t go away with some rest. And nothing more serious or long-term than I have ever experienced in resistance training (shoulder problems), swimming (shoulder problems), and cycling.

Of course I realize that this is anecdotal evidence, but Google “is running bad for your knees” and read the results. Many highly reputable mainstream sites like reference research that supports my own anecdotal observations. Some research even seems to show that running is GOOD for your knees! See Running May Be Good for Your Knees. Clearly the idea that running destroys knees is far from an open-and-shut case.

Running KILLS?

Body by Science also pretty much says that RUNNING KILLS! But let’s have a look at their case.

They point out that Euchidas (479 BC) and Pheidippides (425 BC) both died while or immediately after running the equivalent of ultra-marathons. Then they add,

To no surprise, some modern extremists in the realm of fitness have either met the same premature end as their Grecian counterpart (such as the author and running guru Jim Fixx) or suffered a host of ailments that are not compatible with long-term health and survival. The scientific literature is filled with data that strongly make the case that long-distance runners are much more likely to develop cardiovascular disease, atrial fibrillation, cancer, liver and gallbladder disorders, muscle damage, kidney dysfunction (renal abnormalities), acute microthrombosis in the vascular system, brain damage, spinal degeneration, and germ-cell cancers than are their less active counterparts. (Page 6)

I’m not a scientist, so there’s a pretty good chance I couldn’t fully refute the inferences drawn from all those footnoted research studies showing that running kills. But I did at least try to find and read the research. And here’s the thing: Most of it isn’t publicly available beyond the abstract (not even that in some cases). In order to read the full studies you need to have some special access to the scientific journals in which they are published.

So I tried to follow the authors’ very own admonition to “Be cautious with studies”:

So, if friends, relatives, doctors, champions, and popular publications are suspect, where can we turn for our answers? It’s tempting to reply, “To science.” However, even in this realm, one has to be careful to look closely at the studies that have been conducted, as not all studies represent an honest attempt to find the truth (and, as noted earlier, some are not performed properly). One should never, for example, skim through a study and just look at its abstract and conclusion sections (which, incidentally, is what most people do), because that’s where one can get misled a lot of times. (Page xvi)

So, I’m being cautious. I can’t access the actual studies they reference in the footnotes showing the dangers of running. I can only read the titles, and I DO NOT accept that the claims made in the titles are actually true.

But the very titles of the research cited in Body by Science to show the dangers of running instantly shows their bias. From those titles I see that most of that research involves marathoners, ultra marathoners, or Ironman triathletes.

So EVEN IF everything implied in the titles of these research articles were true, do those studies REALLY address things related to the common runner? I seriously doubt that more than 2% of runners have either (1) run a marathon, (2) run an ultra marathon, or (3) participated in an Ironman distance triathlon event. The studies they reference address the far extremes, not 98% of runners.

Additionally it seems like I’ve always heard that running provides tremendous health and fitness benefits. Let’s see, in about 30 seconds of Googling “is running good for you” I found
Is Running Good Or Bad For Your Health?. This article references recent studies involving many thousands of subjects over long periods of time. They said “The health benefits of running short or long distances are so overwhelmingly positive that they swamp potential dangers”.

Jim Fixx

In 1977 Jim Fixx wrote “The Complete Book of Running” in which he pointed out many of the health benefits of running. In 1984 he died of a heart attack WHILE RUNNING.

His body wasn’t even cold when every anti-running activist idiot on the planet starting dancing on his grave celebrating the irony, featuring his death in their stupid arguments against running. “Ha, the guy who wrote ‘The Complete Book of Running’ DIED WHILE RUNNING! So, ergo, running is bad for you and causes heart attacks.”

The usually scientifically minded McGuff fails to point out (as does every other anti-running activist of this vein) that Fixx had a known family history of heart trouble. Body by Science also refuses to go anywhere near extremely convincing – almost “conclusive” – data that overwhelmingly demonstrates that running is GOOD FOR YOU in countless ways.

And did Jim Fixx live longer than his father or grandfather? Does anyone know how many people died of a heart attack on the same day that Jim Fixx died? What percentage of them were runners? Are there any statistics that show whether the heart attack fatalities among runners are higher or lower than that of the population in general? Are there studies that show whether heart attack fatalities are higher in runners than in body builders/resistance trainers?

I am quite certain that the answers to most of these questions would tell a very different story than the one told in Body by Science.

Did the authors mention that one of the heroes of the resistance training movement, Mike Mentzer, a man to which both authors pay great respects in the dedication of the book, DIED FROM HEART COMPLICATIONS at age 49?

Nope. The only thing that matters is that Jim Fixx wrote “The Complete Book of Running”, became something of a leading figure in the running boom of the late 1970s and early 1980s, and died while running.

Running vs other forms of training

Many now point out the great value of resistance training relative to running, and high-intensity interval training (running) over long, steady-state running. And they have a point.

The “McMaster Studies” referenced in the book do much to show that just 6-9 minutes of high-intensity training per week yielded the same fitness benefit (measured by before and after time trials on a stationary bike) as 4.5 – 6.0 hours/week doing long, steady training.

But I see some serious shortcomings of these McMaster studies. They took randomly selected university students and trained them three times/week for TWO WEEKS. After two weeks they compared their before and after time trial results.

But I wonder what would happen if they had these two groups train for a year instead of two weeks? And what would happen if the endurance training group did sprint interval training for the last month of that year? Assuming no other shortcomings in the experiment I would bet heavily on the endurance training group.

Real-Life McMaster Study

As a matter of fact, I would say that this modified experiment has been performed MILLIONS of times over. A very typical training/racing cycle for elite competitive track distance runners involves this very cycle. During Fall and Winter, competitive runners do “base training”. That’s long, steady endurance training.

Then in early Spring they start cutting back a little on the distance and start increasing “speed work”. This is pretty much high-intensity interval training. As the actual competitive track season progresses through Spring and Summer the workouts are usually shorter, faster, and races are more frequent.

If you could convince a collegiate track team to have their distance runners only train using speed work all year long (which you couldn’t), they would definitely not fare as well as those following the more typical pattern.

Don’t get me wrong. I definitely agree that the McMaster studies made real contributions to our understanding of the value of high intensity exercise. But it doesn’t prove the lack of value of the endurance training.

But whether you agree with my opinion on that or not, it is very clear that the McMaster studies DON’T show or imply that endurance training like steady-state running/cardio is actually BAD for you in any way.


Despite what I consider to be a few gaping holes (mostly dealing with running and cardio), Body by Science makes some fairly convincing arguments for a new way of thinking about health, fitness, and exercise.

The slower movements, lighter weights, and less frequent workouts are all convincingly argued and their benefits thoroughly documented.



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