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PACE: Beyond Intervals

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Al Sears, MD, claims to have a new and better way to do intervals. Sears says it’s beyond intervals. He makes the case in PACE: The 12-minute Fitness Revolution (Wellness Research & Consulting, 2010). It may be the best mass-market book on the merits and application of interval training.

Interval training has worked for elite athletes since the late 1930s, when a German runner used it to set a world record for 800 meters that lasted for 16 years. In 1954, Roger Bannister incorporated intervals into his training and became the first man in history to run a mile under four minutes. Al Sears, one of the first doctors to be board-certified in anti-aging medicine, says his approach makes intervals work better for everyone. To stake his claim, he registered the name in the U.S. Patent and Trademark Office. He calls it PACE®, which stands for Progressive Accelerating Cardiopulmonary Exertion.

Many of his points are quite interesting and I'd like to discuss a few of them. Let’s start with that high-powered acronym.

The last two words, Cardiopulmonary Exertion, simply mean the approach stimulates the heart and lungs to work harder and provide more oxygen. It speeds up your breathing and heart rate.

The first two words, Progressive and Accelerating, are the unique components, according to Dr. Sears. Accelerating means the approach trains your body to respond more quickly—and adapt faster. As you progress, you reach your target heart rate quicker and your breathing gets deeper and more efficient sooner. You will also recover faster. Your heart rate and breathing return to normal in less time. The compression of time to peak exertion and back to resting level makes workouts shorter, a refreshing concept in endurance training. (Arthur Jones made a similar argument in strength training four decades ago.)

That brings us to Progressive, the real breakout feature. Sears had been using most of the PACE program for 25 years before adding this element. “More recently,” he writes, “I added progressivity to increase the benefits.” (Perhaps he never heard that Milo of Croton became the strongest man in the world by lifting and carrying a calf every day until it grew into a full-grown bull. More likely, it didn’t occur to him that overload applies to endurance training as well as strength training. In any event, he caught up fast—and moved ahead of the cardio crowd.)

“Exercise can dramatically change your body over time only when you change what you are doing over time,” he explains. (Emphasis mine) “You have to do a little more of one component each time you do it.”

That’s where interval training leaves traditional aerobics and cardio in the dust.


Sears says we are made for stop and go exertion. “For our ancient ancestors, exertion came in short bouts followed by rest,” he writes. “They didn’t run marathons or jump around for an hour at a time without a break. Whether hunting prey, escaping from predators or fighting for our lives, ancient humankind lived in a world where short, intense exertion was followed by periods of rest and recovery.”

We are not made for aerobics, according to Sears. It’s not the way to exercise. Moreover, he believes aerobic training, as generally recommended by doctors and others, “can actually wreck your body. Do it long enough, and aerobics will make you sick, tired and old before your time.”

The problem, as Sears sees it, is steady state exercise. “When you exercise aerobically, you have to keep the intensity at a medium level,” he explains. “If you increase or decrease the exertion level much, it is no longer aerobic activity.”

As we’ve written here before, that’s not true. Our aerobic energy system continues working at maximum capacity when we cross the so called anaerobic threshold. Our aerobic and anaerobic energy systems work side by side. For details, see New Thinking on Lactic Acid http://www.cbass.com/Lacticacid.htm

Here’s the problem, says Sears: “If you never cross that threshold you never signal your body to increase lung [and heart] strength and reserve capacity.”

To clear up the confusion, Sears has coined a new term to describe when you exert yourself beyond the anaerobic threshold but you are still using your aerobic energy system as well. He calls it “supra-aerobics.”

“By shedding this aerobics dogma and training yourself to find your supra-aerobic zone, you’re going to [build] a bulletproof heart, powerful lungs, strong muscles, youthful features, no excess fat and a long life.”

Okay, you say, but can traditional aerobics actually be harmful? Dr. Sears believes so, and he may be on to something.

Aerobics Harmful?

Dr. Sears goes into considerable detail, but here’s his bottom line: “When you exercise for long periods at a low to medium intensity, you train your heart and lungs to get smaller in order to conserve energy and increase efficiency at low intensity.” It’s specific adaptation to imposed demand. You’re not prepared for greater stress. Your heart, lungs, blood vessels, and muscles give up maximum output while preparing for long, slow exercise.

Sears says that’s why marathon runners drop dead every year. Their bodies are not prepared for the unnatural stress of running 26+ miles.

“Your body doesn’t know whether you’ve run a marathon…or been hit by a truck,” says an expert quoted by Sears. “Their hearts appear to have been stunned.”

“Exactly,” says Sears. “During long-duration exercise, your heart is under constant stress with no time to rest and recover. If it goes on for long enough, your heart is traumatized and your body reacts by triggering a wave of inflammation.”

As I was writing this, a new study was announced confirming that marathon runners suffer heart damage. Eric Larose, a professor of medicine at Laval University in Quebec, was running in a marathon when a younger runner close to him collapsed and died near the finish line. The incident prompted the study which he reported at the 2010 Canadian Cardiovascular Congress. 

Larose and his colleagues recruited 20 healthy runners in the 2008 Quebec City Marathon; the runners ranged in age from 21 to 55. They were given exercise, blood, and MRI tests 6 to 8 weeks before the marathon, two days after, and three months later.

The tests showed that during the race, over half of the segments of the heart lose function due to an increase in inflammation and a decrease in blood flow. The less fit runners showed greater signs of injury, said Larose. They experienced greater loss of function associated with lower blood flow and greater irritation of heart segments, he explained.

Most of the damage had disappeared at three months.

Dr. Sears would probably say that the runners would’ve faired better if they had incorporated intervals into their training program. He’s not against endurance training, as long as it’s not your only exercise. “By supplementing your endurance training with a PACE routine, you’ll actually improve a broad range of athletic capacities,” he said.

Two more topics and then I’ll let you have at the book. First, I want you to hear about a study Sears did with identical twins comparing the results of endurance training and PACE. The results are eye popping. And then I’ll give you a thumbnail rundown on how PACE works.

Cardio Versus PACE

Twin 18-year-old girls came to Dr. Sears with almost identical body composition measurements. They were typical teenage girls, not fat and not skinny. (I’ll use Dr. Sears’ words to describe the study.)

At the start of the study, both twins ran one mile each, three times a week. Over the course of 16 weeks, the PACE twin progressively decreased her distance to fit the PACE program. The cardio twin progressively increased her distance to match a traditional cardio routine.

By the end of the study, the PACE twin was sprinting 6 exercise sets. Each set had a 50-yard exertion interval followed by a recovery period of 30 seconds. The cardio twin was jogging 10 miles straight with no breaks.

The results? The PACE twin went from 24.5% body fat all the way down to 10% for a total fat loss of 18 pounds. What’s more, she gained 9 pounds of pure muscle.

The cardio twin lost fat, but not as much. She also started at 24.5% body fat but went down to only 19.5% body fat for a total fat loss on 8 pounds. Not bad, but instead of gaining valuable muscle, the cardio twin actually lost 2 pounds of muscle.

As I noted above, a characteristic of the PACE program is that the training time decreases, while the typical cardio program gets longer. In this example, the PACE twin exercised for one quarter as long as the cardio twin.

Finally, let’s look at some key elements of the PACE program.

PACE, in Brief

Perhaps the most praiseworthy aspect of Dr. Sears’ PACE program is that it makes interval training accessible to anyone who is mobile. If you can move, you can do PACE. Sears has designed a program for all levels of fitness. The before-and-after photos scattered throughout the book look like any Joe or Jane who might walk into a doctor’s office. They are not models.

“Some of my patients feel a high level of exertion after walking for 60 seconds,” Sears writes. “Others can sprint for 50 yards and not even break a sweat.” PACE will work for either extreme.

In one example, a 56-year-old lady weighing 250 pounds started out walking for just 45 seconds. All she did was walk for a few seconds and rest for a few seconds, and then repeat. That’s all she needed to get started.

“[During a series of] weeks, [she] went from walking for 45 seconds to ‘power walking’ up steep hills,” Sears recounts. “Today she can run, sprint and workout with weights.”

As noted earlier, progressivity is a key element of the program. Another is change. You have to keep challenging your body and change what you’re doing over time.

You begin by slowly working up to maximum effort, and then you rest. (Maximum is what challenges you at first.) Once is enough to get started. From there you add reps, exert yourself, rest, and then do it again. A unique feature is that the rest periods are flexible. You rest until your heart rate and breathing come down and you feel ready for another rep. Total exertions periods on average are about 12 minutes; don’t count the rest periods. You can do more if you like, but Sears suggests keeping total exertion time under 20 minutes.

Another distinguishing feature is that the exertion periods often vary during the course of the workout. You might begin with a 4 minute work period and end with 30 seconds. Or you can do it the other way around; start short and end long. Mix it up; do it one way in one workout and change the next.

You can walk, run, bike, swim, or whatever you like. It’s best to change what you do from time to time.

Many more details can, of course, be found in PACE: The 12-minute Fitness Revolution.

*  * *

I’m sure Dr. Sears would agree that many aspects of his program are not new. (I’ve used and written about many of them myself.) Sears, to his credit, has created a version unique in application and scope. And he has packaged and explained it superbly. As I’ve already said, the flexibility and accessibility are unmatched.

My compliments to Dr. Sears. He’s doing great work.

*  *  *[

Readers Speak Out

[Many readers commented on this article. Here are two exchanges we believe you'll find thought provoking.]


I would prefer to go against most of the conventional thinking.

For me, it makes total sense, that our always quoted ancestors of thousands of years ago, were anything but " brief periods of action followed by significant rest periods." Our ancestors had to do everything themselves. Chopping trees, making shelters, walking, JOGGING vast distances to move, hunt, forage, see neighbors, keep the territory safe, see what was over the horizon. This went on for thousands of years.

Still to this day, those people who have to hunt without bullets will have to run their prey to death. That takes hours.

The way some of these articles are put one would think a man of those times could simply out sprint animals to kill them!

Only when serious danger was imminent would one have to sprint. Otherwise, every day was endurance day; so in fact the one thing man would avoid where possible would be intense periods, because that would lead to early fatigue. Fighting was intense...those battles could last a day or more.

Modern man has developed the "frantic" brain.........." gotta, gotta, gotta...". Everything has become rush mode, from business, to games, to even leisure (what's leisure?!). Because we lack the real macho achievements of those before us, we have to invent macho pastimes, and pain is part of this. That comes from the intense "lift as much as you can, as quick as you can"...and the same for running/cycling etc.

Of course this has a tremendous training effect, when done judiciously and with common sense. But where is that today? Gone for the most part.

The long periods of cardio have been abused along with the above, because people attack the long distance training too hard, and that of course will wreck anybody, as will doing intervals too quickly and too often. Long and slow is an incredible strength builder and metabolic booster, when done correctly and as part of one's approach to a fit life, let alone a race or an event.

I am also firmly of the opinion that when one is pushing hard intervals or intense weights ( both of which I love ), gas should ALWAYS be left in the tank. You basically give your all only when competing, so you are able to train day after day with plenty of energy.

I continue to admire your work, as you are your own guinea pig....and I humbly submit that the authors of most of the articles that are against the prolonged cardio, are people that have never really tried it at all, ( as part of a sensible fitness plan) and do not like it ( in which case there is bias ). As one of your top long distance gurus has noted..." ya gotta slow down to go faster "....and he has been around for years and tested it all and achieved it all.


Richard Stent, South Africa

Clarence's Reply and Reader Follow-up

Hi Richard:
Thought we might hear from you on this one. Very well stated, my friend.
Likely truth is that ancient man did all combinations short, hard and long, slow--whatever was required for survival.
The problem is that some, including doctors and some personal trainers, believe that crossing the anaerobic threshold is not necessary and may even be harmful. We've both seen people in fitness centers riding bikes while reading their newspapers. They simply don't get it--and probably don't want to.
If you do long, slow, you should also do short, hard. I know you do both.
Did you happen to see my article on the German study of top triathletes, Combined Strength and Endurance Training Best? http://cbass.com/CombinedStrength_Endurance_Heart.htm
As suggested earlier, the two types of adaptation are complementary. Either extreme, however, can be problematic. For example, the researchers point out that “ultra-endurance exercise is thought to be associated with a predisposition to ventricular tachycardia [abnormal rhythm] and sudden cardiac death, which is common in male athletes.
As we've discussed before, you're inclined toward long endurance, and I'm disposed to short, hard stuff. The idea of running a marathon has absolutely no appeal for me. You, on the other hand, are just getting warmed up at 26 miles. Yet, we are both pretty fit.
Problem is that some people have no business running marathons; as the doctor quoted in PACE article says, their body thinks they've been hit by a truck. They're asking for trouble.
My guess that very few people living in ancient time would have occasion to run 26 miles without stopping--certainly not by choice. Even when chasing prey they probably stopped to rest every chance they got. Prey also stopped when possible.
So there is no one best way. Doing a little of both would probably be best for most people.
Remember too that Al Sears isn't talk to guys like us. We probably don't need him. But that women who could only go for 45 seconds, she needs him. She's his patient/audience. Of course, there are far more inexperienced trainers and people in terrible shape (like that women) than people like us. We're the exception, not the rule.
Remember, only 5% of Americans are physically active on any given day. Probably more in Australia and perhaps where you live.
I admire and appreciate you, my friend. You're the real deal and I love hearing from you.
Right on, Clarence...many thanks for the reply.

I have to tell you this.......any endurance work I do over 2 hours is always very slow, and includes plenty of walking!

I will only do this once a week maximum, and the rest of my training is short and hard....including weight training.

I actually detest marathons...and would rather do something longer, because then I do not feel guilty walking!

I love short and hard, and have trained that way for many years. However, I simply have always found that a long run once a week does wonders for overall conditioning (something top weight training coaches are talking about more often). A long run can be one hour, or three.


Another Reader Comments

Dr. Sears' book is probably the most sensible of the publication on intervals I've seen since being introduced to the subject 30 years ago, when I first got into running.

However, I want to point out that Dr. Sears has made a number of questionable claims, including the following condensation in your article:

The problem, as Sears sees it, is steady state exercise. “When you exercise aerobically, you have to keep the intensity at a medium level,” he explains. “If you increase or decrease the exertion level much, it is no longer aerobic activity.”

Dr. Sears goes into considerable detail, but here’s his bottom line: “When you exercise for long periods at a low to medium intensity, you train your heart and lungs to get smaller in order to conserve energy and increase efficiency at low intensity.” It’s specific adaptation to imposed demand. You’re not prepared for greater stress. Your heart, lungs, blood vessels, and muscles give up maximum output while preparing for long, slow exercise.

However, as you noted in October:

The “athlete’s heart,” the researchers write in their report, is the “most striking adaptation...to long-term, frequent physical training.” Endurance training and resistance training produce two types of adaptation. “The volume load in endurance training leads to thickening of the ventricular wall and cavity dilatation [expansion], whereas the pressure load in resistance training induces…increased myocardial [heart muscle] mass and wall thickness, without a substantial change in cavity size.”

Which is something the sports medicine world has noted for years. In fact, after I became a "hard core" runner (in my 20s, having never competed or trained in school), at my best, I was running a sub-4:20 mile and <15:00 5k with a resting heart rate of 32bpm and 88/60 blood pressure. I found this out because I would get light-headed when standing up too quickly...the flight surgeons in the military finally figured out that my extremely low pulse was due to my larger heart (adapted to the training) and "outstanding" per stroke volume of blood my heart was able to generate.  (As Dr. Leonard Schwartz called it, I had the classic athlete's hypo-tension vs. hyper-tension.)

So, based on your October article and the (objective) research performed, aerobic training does increase the size of one's heart and, per some researchers, lungs. I've actually contacted Dr. Sears' office and asked if they could cite the research he's citing to back this statement, however, they only had one vague reference that did not equate to the years of studies that have shown the opposite of what he states.
Also, when you decrease your exertion level, you're still "aerobic".  Big error by Dr. Sears in that statement...one can be doing a slow walk and that is aerobic as is cycling at 60% of your max heart rate.

Another problem: Dr. Sears, unfortunately, appears to be lumping the steady state aerobic types--the people who get on an Elliptical Trainers, Indoor bikes--with people who get outside and train in the real world. I've never, ever done any steady state running were the road(s) have been flat and there's been no wind. Rarely is that the case. Example, Running in (flat) downtown Chicago on the lake was a blast, when the wind was at my back. For my 40 minute run this morning, I covered one gradual .5 mile incline and a shorter (.1) incline on the way out, heading into an 8 - 9mph headwind.  On my return, I have a .75 mile hill before turning into my neighborhood.  

Apologies for the long email, but, as much of Dr. Sears' information, as I understood from his office staff, is the result of a 'net research service, I wanted to bring some of the inconsistencies or possible mistakes in his claims to your attention.

As always, best to you and Carol and thanks for your work!

Parker Reed, Texas

Clarence Replies

Hi Parker:
Thanks for interesting feedback.
Dr. Sears would probably agree that most serious runners, such as yourself, include plenty of up and down intensity in their training. Unfortunately, many less experienced trainers have been led to believe it's best to stay in the so called aerobic zone, for fat loss and fitness. That can be a problem.
Others are attempting marathons without proper preparation, which can can present major problems.
Finally, many are afraid to attempt interval training. That's where PACE can really be a Godsend.
You're a continual source of thoughtful comment. We appreciate you. Thanks
So as you and (and former distance runner/triathlete and Runner's World cover model/athlete) Mark Sisson note, walk a lot, run fast a few times a week and lift heavy twice a week. Parker

Bulls Eye! Mix it up; slow and fast, hard and easy. Clarence











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