Endurance Training: Intervals vs. Long-Slow/Steady-Distance

For Heart Health, Fat Loss, and Physical Performance

Kurt J. Wilkens, RKC

September 20, 2006 11:59 AM

Endurance Training goes by many names and takes many forms. If you spend a considerable amount of time in so-called 'health clubs', it's likely "cardio" (probably the most popular terminology in general); cardio often involves a treadmill or an exercise bicycle. If you're a woman, I would imagine you have, on occasion, referred to it simply as "aerobics"; aerobics are usually done in some type of dance class. If you're an athlete, or at least athletically-inclined, you probably know it as "conditioning", or, if your athletic interests take a decidedly Eastern European bent, it may even be "General Physical Preparation"; depending on your particular athletic pursuit, conditioning/GPP may have you running a lot and doing many, many bodyweight exercises. My personal favorite, and the nomenclature that we prefer at Integrated Conditioning, is 'work capacity'; work capacity is typically developed via the use of various 'weighted' protocols, such as kettlebells (H2H drills, TAPS multi-level drills, etc.) and strongman implements (tire flip, sandbag carry, etc.).
People will typically perform their Endurance Training for one or more of the following reasons: heart health, fat loss, and/or improved physical performance.
Other than for occasional inclusion during specific periods or phases in an athlete's training program, most people generally (I realize it's wrong to generalize, but generalities are not always wrong) seem to think of Long-Slow/Steady-Distance (LSD) work as the best/most-effective-for-everything/only type of Endurance Training worth doing. This type of exercise has been around for a very long time, and it still persists to this day ? even in spite of the mounting evidence that indicates that there may be a far better way to get your Endurance Training (no matter the reason you are performing it).
(In all fairness, interval training is receiving a little more 'press' in the fitness community, but certainly not near what it deserves. I'm hoping that this article will open the eyes and expand the possibilities of at least one person who hasn't already considered switching from LSD to intervals.)
LSD training, also often referred to as Steady-State aerobic exercise, is "steeped in tradition", and anything with so much history behind it is going to be difficult to overcome. People often spout that useless rhetoric about how "? it's worked in the past, it will work now! Why should I do it any differently?"
Well, I'm going to tell you!
First, though, it's important to note that there are essentially two forms of Endurance Training ? aerobic and anaerobic ? and they take place within the body's three energy systems. Anaerobic exercise occurs in the Immediate and Non-Oxidative Energy Systems. The Immediate Energy System, sometimes referred to as the ATP/CP Pathway, involves the breakdown of Adenosine Triphosphate and Creatine Phosphate in the cells for energy; it provides instant energy for very brief bouts of intense exercise, typically lasting no longer than about three seconds. Heavy, one-rep weightlifting would be an example. After those three or so seconds, the Non-Oxidative/Glycolytic Pathway takes up the slack. This pathway produces short bursts of energy via the breakdown of glucose (sugar in the bloodstream) and glycogen (sugar stored in the muscles and liver), and typically is called into play for physical activities lasting between four seconds and one minute. A couple examples might be 100- and 400-meter sprints.
Aerobic exercise makes use ? obviously ? of the Aerobic Energy System, also known as the Oxidative Energy Pathway. This is the body's only energy system that requires oxygen to work. (More or less. There is some overlap between the systems; a continuum of sorts.) The Aerobic Energy System cannot produce energy as quickly as the other two, but it can sustain its energy production for much longer durations; thus, it is used for events that last longer than two minutes ? typically much longer. Think of marathons and/or the Tour de France. LSD training falls into this category.
Now, let's look at Endurance Training a point at a time.

Heart Health
First, and most importantly (at least it should be for all of us!), is the heart health issue. For the longest time, we have been led to believe that we need to do LSD work in order to strengthen our hearts and have them work more efficiently. LSD training was going to keep us from dropping dead of a heart attack. And it works, right? Yeah; just ask poor Jim Fixx. (Again, in fairness, there were certainly other factors that might have contributed to his unfortunate demise while running, but I think you take my point ?)
In the inaugural issue of The Performance Menu, Dr. Art DeVany (in an excellent interview by Robb Wolf) declares, "Routinized, lower intensity activities, even jogging, train the natural chaos out of the human heartbeat, making it less adaptable to stress."
Dr. DeVany goes on to offer the following explanation as to why we still see LSD-type training being suggested as best in the so-called 'scientific community':
"? [S]teady state training is often taken to be the norm for training because it is studied most. And it is studied most because that is what researchers know how to do. The far more effective intermittent training [intervals] is little known because the research is harder to do."
In an article on his website, Dr. Al Sears, author of the terrific book 'The Doctor's Heart Cure', offers reasoning very similar to that of Dr. DeVany for choosing interval training over LSD: "Conventional wisdom says that your heart needs endurance training to remain healthy. Indeed, they use cardiovascular endurance (CVE) as a synonym for heart conditioning. But is this really what your heart needs? I don't think so.
"Heart attacks aren't caused by a lack of endurance. Heart attacks typically occur at rest or at periods of very high cardiac output. Often there is a sudden increase in demand. A person lifts a heavy object, is having sex or receives an unexpected emotional blow. The sudden demand for cardiac output exceeds that heart's capacity to adapt.
"What you really need is faster cardiac output. By exercising for long periods, you actually induce the opposite response. When you exercise continuously for more than about 10 minutes, your heart has to become more efficient. Greater efficiency comes from 'downsizing'. You give up maximal capacity because smaller can go further."
In 'The Science of Martial Arts Training', Charles I. Staley, MSS, provides us a somewhat different benefit: "Intermittent exercise ? accumulates a greater volume of stress on the blood pumping capacity of the heart. According to exercise physiologist Dr. Steven Seilor, the periodic elevations and decreases in intensity may create special loading stresses on the heart that are adaptive. Seilor suggests that during an interval, heart rate climbs high, then at the moment the interval stops, heart rate immediately starts to drop, but venous return remains high. These exposures to additional ventricular stretch may help trigger ventricular remodeling (increased heart ventricle volume)."

Fat Loss
Dare I say, this is probably the reason the 'average' person undertakes an Endurance Training regimen. We're constantly told about how LSD training is going to burn the fat right off us and expose the hard, tight body beneath it. This works too, right? Clearly; just look at all the skinny-flabby women bouncing around their aerobics classes for hours at a time.
The reasoning behind LSD being so often cited as the best form of fat-burning exercise is actually quite logical. When one trains in the steady-state LSD fashion (typically for 30-60 minutes), they are training in the Oxydative Energy System. The oxidative pathway burns fat for energy. It has also been suggested that, after about twenty minutes of continuous steady-state exercise, you have depleted your immediately available energy sources ? glycogen and fat ? and are beginning to work on your stored body fat. At first blush, this all sounds well and good ? but, as with so many other things, it's just not that simple.
In an article entitled 'Forget the Fat-Burn Zone', Clarence Bass cites research done by a group of Canadian scientists, headed by Angelo Tremblay, Ph.D. Tremblay, et al, compared the results of an Endurance Training (ET) program versus High-Intensity Interval Training (HIIT) on fat loss:
"As you might expect, the total energy cost of the ET program was substantially greater than the HIIT program. The researchers calculated that the ET group burned more than twice as many calories while exercising than the HIIT program. But (surprise, surprise) skin-fold measurements showed that the HIIT group lost more subcutaneous fat. 'Moreover,' reported the researchers, 'when the difference in the total energy cost of the program was taken into account..., the subcutaneous fat loss was nine-fold greater in the HIIT program than in the ET program.' In short, the HIIT group got 9 times more fat-loss benefit for every calorie burned exercising."
Clarence then gives us the researcher's bottom line as to why this might be: " '[Metabolic adaptations resulting from HIIT] may lead to a better lipid utilization in the post-exercise state and thus contribute to a greater energy and lipid deficit.' In other words, compared to moderate-intensity endurance exercise, high-intensity intermittent exercise causes more calories and fat to be burned following the workout. Citing animal studies, they also said it may be that appetite is suppressed more following intense intervals."
In case you aren't familiar with Clarence Bass, he is an advanced-aged bodybuilder who has truly earned the nickname "Mr. Ripped". He knows whereof he speaks on the issue of fat loss. I would urge you to investigate his website, www.cbass.com.
Another important consideration when it comes to Endurance Training for fat loss is its effect on overall body composition. LSD training is notoriously catabolic. In other words, it will often 'burn' almost as much muscle as it does fat, ultimately producing the dreaded "skinny fat person".
Again, we can find an answer on Clarence's website. In an interview with Dr. Pat O'Shea (author of 'Quantum Strength and Power Training'), Clarence poses the following question: "? Would the Tabata protocol of high-intensity intervals be good for bodybuilders who want to preserve muscle mass while losing fat?"
To which Dr. O'Shea responds:
"The answer is definitely a big yes ? short-term intense interval training is highly effective in altering the ratio of lean body mass to fat without compromising muscle size. Intense interval work is an excellent way of losing weight while simultaneously getting ripped for peak contest shape."
Mr. Bass' website is certainly not the only place to go to find this data. There are numerous other independent sources that could be cited to support the premise that intervals are far better fat-burners than LSD.
Rob Faigin is the author of the remarkable 'Natural Hormonal Enhancement', a thoroughly researched and referenced work on diet and exercise. He appears in photographs to be well-muscled and quite lean, so it may be that he knows what he's talking about. In a discussion ? in his NHE book ? on the impact of cardiovascular exercise on fat loss, Rob tells us that, "? once again, conventional wisdom is wrong.
"The prevailing belief is that to reduce bodyfat you should perform cardiovascular exercise at a low level of intensity in a steady, rhythmic fashion for an extensive duration. However ? this lowers the intensity/volume ratio, which, in turn, increases cortisol relative to growth hormone and testosterone ? definitely not the hormonal profile you want."
Allow me to summarize for you with a somewhat time-worn example: Would you rather look like a lean, powerful sprinter, or a soft, weak distance runner? No offense to distance runners, of course ?

Physical Performance
It is a widely held opinion (by people who think they know) that LSD-type training is necessary and/or the best method for the improvement of one's endurance if one wishes to succeed in sports. Almost everywhere you look, you will find athletes out jogging for miles at a time, hoping to put themselves into a better-conditioned state than their opponents. Do you find yourself gasping for breath after a particularly demanding grappling or sparring session? You need to run longer! Are you a football player who gets overly winded during short plays? You should be doing more aerobic exercise!
Right?
Well, not exactly.
With the obvious exception of the true extreme-duration steady-state-type endurance sports such as Triathlons and marathons and the Tour De France, more often than not, LSD work is actually counter-productive when it comes to maximizing one's athletic performance. In fact, all in all, interval training will offer far greater benefits and improvement than will LSD. Let's look at two of the biggest reasons why you should choose intervals over LSD in your quest for peak performance.
First, interval training will develop your aerobic capacity along with the anaerobic; LSD-type training will only build your aerobic capacity. Rob Faigin, in his book 'Natural Hormonal Enhancement', again provides us with some science:
"In addition to the hormonal advantages of interval training, there are cardiovascular benefits as well. One study that compared improvements in aerobic capacity (as measured by VO2max) achieved through interval training to improvements achieved through continuous training, found that interval training resulted in a two-fold greater increment in VO2max. Another study comparing these two types of exercise found that while both training modalities improved aerobic capacity to the same degree, interval training increased anaerobic capacity by 28% while continuous exercise failed to improve anaerobic capacity. Furthermore, once aerobic improvements are attained through exercise, interval training is the most effective means of maintaining such improvements ? Collectively, these studies demonstrate that intensity is the key factor relative to both increasing and maintaining cardiovascular fitness. Interval training accentuates intensity; hence, it affords considerable cardiovascular benefits in addition to hormonal benefits."
Thank you, Rob!
Second, anaerobic endurance is more practical to most sports, as opposed to aerobic. This is especially so for most power athletes, such as fighters (boxers and wrestlers/grapplers and traditional martial artists) and ball players (football players, baseball players, etc.). Anaerobic endurance is also more applicable to one's day to day activities, in my humble opinion, than the LSD work.
The reason for this has to do with the fact that the action in these type sports, for the most part, is anaerobic in nature; it takes place in the Immediate/ATP-CP and Non-Oxidative/Glycolytic Energy Pathways, to be precise. Typically, there is a brief flurry of high-intensity work followed by a short ? often active ? rest, followed by more work, etc.
Let's look at some examples from combat sports, because it's an area with which I have some familiarity.
To illustrate just how much this tradition of LSD work has held on, allow me to use a personal example. Just a few short years ago, I had a Tae Kwon Do instructor who was preparing for yet another rank test. Already a fourth- or fifth-degree black belt, I would have thought he'd know better by now. Nonetheless, I found him one morning, jogging slow laps around the job site (we both worked in construction at the time). While he did in fact pass his belt test, I have to wonder how; and, would it not have been easier for him if he'd been doing some interval work instead of ? or at least in addition to ? his jogging.
Meaning no offense to him at all, I suppose that this also illustrates how one can be quite technically proficient (and an excellent instructor) in a particular athletic endeavor, and at the same time, really not know how best to train for it. As I recall, he may even have told me he wasn't a fan of heavy weight training; that it made one slow. He was clearly "bound by tradition". (On the other hand, it's been a few years since I've spoken with him. It may well be that he's come around to the 'right' way of thinking. I hope so ?)
In 'Special Topics in Martial Arts Conditioning', the course text for ISSA's Specialist in Martial Arts Conditioning certification, Charles I. Staley, B.Sc., MSS, touches on this very subject: "As a martial artist, most of your energy output is anaerobic. Without oxygen (kinda makes you wonder why most martial arts instructors stress aerobic conditioning so fervently, doesn't it?). Delivering blows and kicks, grappling, throwing, and lightening fast reflexive movements must be performed over and over again, testing your tolerance to excruciating pain and fatigue ?"
In other words, why train for that type of performance by settling in to a long, slow, almost relaxed, form of exercise?
For a more practical, in-the-trenches, example of the effect of LSD running versus intervals on performance, we can look to Forrest E. Morgan, Major, USAF. Maj. Morgan, a very serious traditional martial artist, is the author of the comprehensive tome on how a warrior should think and train: 'Living the Martial Way'. Maj. Morgan relates to the reader how, after graduating from the USAF Officer Training School, he continued his running program, eventually working up to the point where he was running for an hour a day ? sometimes as much as seven miles or more at a shot. "I thought certainly this would give me the stamina I sought for fighting. Wrong!
"The more I ran, the more my fighting suffered. I lost all my burst speed, the ability to spring at the opponent ? Furthermore, I lost the ability to jump; it seemed my feet were anchored to the floor. But most frustrating, for all the work I was putting in, I didn't seem to have any more fighting stamina than before I started running. I tired just as quickly as I always did. I discovered what track and field athletes have known for decades: the steady, plodding pace of distance running produces a steady, plodding athlete."
Thus it was that Major Morgan discovered the need for, and benefits of, interval training. It also brings up a very good point. Intervals develop speed, LSD doesn't, and once you're fast, you can always slow down; if you've trained yourself to be slow, it is, I submit, nigh-on impossible to suddenly get fast. Put as simply as possible (which is the only way I understand anything), LSD-type exercise trains the slow-twitch muscle fibers; intervals tend to develop the fast-twitch fibers. It has also been suggested that exercise can convert one type of muscle fiber to another! This is a crucial point because we are born with only a certain number of muscle fibers ? slow and fast ? and only the luckiest among us have a high degree of fast-twitchers relative to slow. These fast-twitch-fellows are the ones we seem to look up to most; icons of strength and power and speed. Why would you do anything that is going to change some of your precious fast-twitch fibers into slow?
Being fast can also save your life. Consider the following scenario: Walking alone at night through Central Park (not the wisest move to begin with, but ?), minding your own business, you find yourself suddenly set upon by a gang of no-goodniks. After a flurry of brutal violence, you are able to extricate yourself from their grasp. In making your escape, which would you consider to be your wisest course of action: Settling into a slow, measured jog that would allow the hooligans to quickly catch up with you and kick your face into a Jackson Pollock painting; or, sprinting all-out for the nearest source of light or population/witnesses before your assailants can grab you and drag you into the bushes to ? well, you know?

In the interests of full disclosure, however (and after a several-page rant against it), I would be remiss if I didn't mention the fact that some LSD work may be required at the outset of an athlete's training career, simply to develop a foundation of aerobic endurance. Once the athlete can perform steady-state aerobic activity for 20-30 minutes at a shot, however, it's probably time to move on to anaerobic training.
In an Internet article entitled 'A Basic Primer on Endurance Training', Charles Staley writes, "Note: Many conditioning specialists eschew the concept of developing an aerobic base, feeling that a highly developed aerobic capacity is counter-productive to the attainment of speed and strength. However the anaerobic system is based on the aerobic system, so at least in principle, it seems logical to develop the system which will promote lactic acid clearance during high intensity training efforts later in the cycle. As in all things, it really is an issue of how much aerobic work is done, and where it is placed in the training cycle."
There is one form of aerobic training that I do find sort of intriguing ? as far as aerobic exercise goes, anyway. It's called Aerobic-Intervals, so I suppose it may not even fit perfectly into the LSD format. I think this form of aerobic work may be more beneficial than traditional LSD aerobics if only because it utilizes shorter work intervals, with rest periods between, thus allowing for relatively greater training intensity. If you need to include some aerobic-type work ? in the off-season, say ? I would submit that this may be the way to go. You can find further tuition on this method in Staley's article referenced above, or in his excellent book, 'The Science of Martial Arts Training'.
On a personal note again, I've been trying for some time to get my sister to switch to intervals, but she just won't do it; she sticks with her LSD-type jogging on a nearly daily basis and wonders why she can't make any significant progress in fat loss and conditioning! (Naturally, diet can also play a very significant role in one's success or failure, physique-wise. This is another area where traditions remain strong, and I can't get my darling sister to pay heed to anything I say about this, either. "But I need my bread and pasta!" Oh well ?) If I had to guess, I would venture to say that most fitness-minded people ? my sister included ? don't like interval training because it can be a downright brutal form of exercise. Believe me, I can relate to this way of thinking.
On the other hand, the real beauty of intervals is that they usually only need to be done for a relatively short period of time, and with less frequency. Whereas LSD training is most often expected to be done 3-5 times a week, for 30-60 minutes at a shot, an effective interval training program can feature workouts as short as ten minutes (total time!), performed as infrequently as twice a week. I should think that the time-efficient quality ? irregardless of its many other discussed benefits ? of interval training would be a real boon to busy people with full-time jobs, family and social obligations, etc, who do not wish to spend all their lives in the gym.

There are many varieties of interval training available to you ? most of them quite good. Just a couple of the more popular ones for your consideration: The Tabata Protocol, based on the research of Japanese doctor Izumi Tabata, Ph.D., is typified by 6-8 intense 20-second work intervals followed by 10-second rest intervals. High-Intensity Interval Training (first promulgated, I believe, by Shawn Phillips in an old issue of Muscle Media) involves doing one 30-second jog followed by a 30-second sprint; this is repeated four times in the first and second workouts ? for a total of four minutes ? after which another minute (one 30-second jog, one 30-second sprint) is added for the next two workouts. You continue in this way, adding one minute after every couple workouts, until you are doing fifteen minutes of work.
Again, these are just a couple of the more well-known examples. There are many other ways of implementing intervals into your program, and I would encourage you to look into some of them ? or even create your own protocol!
For the purposes of this article, and in the interests of simplicity, you will note that I've addressed Endurance Training only in terms of the more conventional types of non-weighted protocols (running, swimming, jumping rope, etc.) rather than including the somewhat more unorthodox weighted variations. Bear in mind that weighted Endurance Training can be just as marvelously effective ? if not more so ? as any non-weighted exercise at improving heart health, fat loss, and physical performance.
Something to consider when choosing a form of interval training, from Health for Life's 'MAX 02': "Studies suggest that weight-bearing activities [such as running, jumping rope, etc] promote faster caloric expenditure. Which means weight-bearing activities may increase your aerobic efficiency more rapidly than non-weight bearing ones [such as swimming and cycling]." Which basically means, if you choose to jump rope, for example, rather than ride the recumbent exercise bike, you will burn more calories quicker, get aerobically fit quicker, and ultimately, lose body fat quicker. Sounds like a win-win-win to me!

While I may well be "preaching to the choir" on this issue, there may be some of you ? like my TKD instructor and my sister ? reading this who are still stuck in the old ways, wasting away your time, energy, and muscle on Long-Slow/Steady-Distance exercise. If this is you, I sincerely hope you will at least give some consideration to the ideas discussed in this article. Don't turn a deaf ear, blind eye, insert-favorite-bodypart-metaphor-here, to this information; investigate intervals for yourself. There is far more research out there supporting interval training than what I've presented here.
Finally, I'd like to leave you with one parting thought: Just because you've always done something a certain way (and perhaps even gotten some results from it), doesn't mean you've been doing it the best way. After all, if you can get better results for your efforts, in less time, isn't that something you should be thinking about?

Kurt J. Wilkens is the founder of Integrated Conditioning, Inc., a South Florida-based personal training company that emphasizes Functionality and Wellness over simple 'fitness'. Integrated Conditioning specializes in combining Old-School Physical Culture with Modern Sports Science to develop the most effective programs possible for any individual's specific needs. Training is available to you online, or in the convenience of your own home. Kurt is an ISSA-Certified Fitness Trainer, an ISSA-Specialist in Martial Arts Conditioning, and a Certified Russian Kettlebell Instructor. He can be reached via his website: IntegratedConditioning.com.

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