Category Archives: Interval training

How to get fit in just 90 minutes per week

by David Gutierrez, staff writer 

(NaturalNews) A workout technique known as interval training can help you get in shape in a fraction of the weekly time investment required by more conventional workout techniques, according to a study conducted by researchers from Liverpool John Moores University (LJMU), the University of Birmingham and published in the Journal of Physiology.

According to World Health Organization recommendations, all people should engage in between three and five hours of endurance training every single week in order to be fit and healthy and to reduce their risk of chronic diseases and early death. Yet, it can be a major challenge for many city dwellers to make that much time for exercise. Indeed, the majority of U.S. adults do not meet exercise recommendations, and lack of time is considered the main cause.

The study compared two separate forms of workout known as High-Intensity Interval Training (HIT). HIT consists of alternating between a vigorous activity (such as running or cycling) and a less vigorous activity (such as walking) – which activities are used and for how long varies depending upon the needs of the individual. HIT programs are popular because they provide comprehensive fitness workouts in a short period of time. For example, a typical HIT workout might consist of 90 seconds cycling on an exercise bike as fast as possible, followed by 60 seconds of slow cycling, repeated five times for a total of a 15-minute workout.

Fitness in just 90 minutes per week

In the current study, researchers evaluated several health markers of people who had taken part in HIT or Sprint Interval Training (SIT) workouts.

“SIT involves four to six repeated 30-second ‘all out’ sprints on special laboratory bikes interspersed with 4.5 minutes of very low intensity cycling,” researcher Sam Shepherd said.

“Due to the very high workload of the sprints, this method is more suitable for young and healthy individuals. However, anyone of any age or level of fitness can follow one of the alternative HIT programs.”

The researchers found that just three half-hour SIT sessions per week improved insulin sensitivity (a marker of health and fitness) as effectively as five one-hour traditional endurance sessions. SIT was also effective at improving delivery of glucose and insulin to skeletal muscle and burning of fat stored in skeletal muscle.

“Additionally, we found a reduced stiffness of large arteries which is important in reducing the risk of vascular disease.” researcher Matthew Cocks said.

The findings suggest that HIT and SIT should be effective at reducing the risk of cardiovascular disease, diabetes, obesity and many other conditions associated with aging.

Shepherd further noted that according to the preliminary results of an ongoing pilot study at the University of Birmingham, people between the ages of 25 and 60 rank HIT (performed on exercise bikes) as more enjoyable than traditional endurance training. The study participants also appear to experience greater improvements in mood from HIT than from endurance training.

“This could imply that HIT is more suitable to achieve sustainable changes in exercise behavior,” Shepherd said.


The Right Sets for Strength and Size

By: Scott Quill
You’ve been told to listen to your body, learn its idiosyncrasies, embrace it like a friend. Don’t buy it. You can listen and learn, sure, but forget the friendly stuff. When it comes to muscle, you need to be less good buddy and more psychotic drill sergeant.

Keep your muscles off balance. When they get used to lifting a certain amount in a certain way (sound like your workout?), they stop growing. A weight-training program that never changes also creates strength imbalances; that’s unproductive and dangerous.

This doesn’t mean you have to master the incline behind-the-back modified Slovenian triceps windmill. Just do your usual exercises, but use different combinations of sets and repetitions.

What follows is a guide to different kinds of sets and how they produce different results, from trainer Craig Ballantyne, C.S.C.S., owner of Plug this into your weight training-program and see the surprised—and supersized—reaction you get from your muscles.

Straight Sets
What they are: The usual—a number of repetitions followed by a rest period, then by one or more sets of the same exercise.

Why they’re useful: The rest periods and narrow focus of straight sets help add mass and build maximal strength. As long as you rest enough between sets (1 to 3 minutes), your muscle, or group of muscles, will work hard two, three, even five times in a workout.

How to use them: The start of your workout is the best time to do straight sets, regardless of your experience level, Ballantyne says. Your energy and focus are high at the start, so it’s the best time to execute difficult moves. Perform three straight sets of six to eight repetitions of a challenging exercise like the bench press, pullup, or squat; aim to do the same number of repetitions in each set, with either the same or increasing amounts of weight.

What they are: A set of each of two different exercises performed back-to-back, without rest.

Why they’re useful: Supersets save time and burn fat. You can multitask your muscles—for instance, working your chest and back in one superset and legs and shoulders in another. Lifting heavy weights in a short time period increases the rate at which your body breaks down and rebuilds protein. This metabolism boost lasts for hours after you’ve finished lifting.

How to use them: Insert a superset at any time in your workout. To involve the most muscles, pair compound exercises—moves that work multiple muscles across multiple joints. For example, combine a chest press with a row, or a shoulder press with a deadlift. To save more time, pair noncompeting muscle groups, such as your deltoids and glutes. One muscle group is able to recover while the other works, so you can repeat the set without resting as long.

What they are: Three different exercises performed one after another, without any rest in between.

Why they’re useful: Trisets save time and raise metabolism. A single triset can be a total-body workout in itself, like our 15-minute workouts.

How to use them: Trisets are a good workout for at home (or in an empty gym), because you need to monopolize equipment for three exercises. Do basic exercises that hit different body parts—like bench presses, squats, and chinups. Perform a warmup set using 50 percent of the weight you usually use in each exercise. Then repeat the triset two or three times, using weights that allow you to perform eight repetitions per set. Rest 1 to 3 minutes after each triset.

Drop Sets
What they are: Three or four sets of one exercise performed without rest, using a lighter weight for each successive set. Also called descending sets or strip sets.

Why they’re useful: Drop sets are a great quick workout, fatiguing your muscles in a short time, getting your heart going, and giving you an impressive postworkout pump as your muscles fill with blood.

How to use them: Use drop sets when you’re pressed for time. Don’t do them more than three times a week; you’ll get so tired you won’t be able to accomplish much else. Start with a warmup, using 50 percent of the weight you expect to use in your first set. Now use the heaviest weight you’d use for eight repetitions of that exercise to perform as many repetitions as you can. Drop 10 to 20 percent of the weight and go again. Continue to reduce the weight and go again, always trying to complete the same number of repetitions (even though you won’t), until your muscles fail.

Circuit Sets
What they are: A series of exercises (usually six) that you complete one after another without rest, though you can do some cardiovascular work (such as jumping rope) between exercises.

Why they’re useful: When you use weights, circuits can be a great total-body workout. But they’re most valuable without weights as a warmup of the nervous system, joints, and muscles, Ballantyne says. Because a circuit stresses the entire body, it’s more effective than a treadmill jog, which primes only your lower body.

How to use them: You’ll annoy the other guys at the gym if you do an entire workout based on circuits, because you’ll monopolize so many pieces of equipment. But one circuit is quick and effective. If you’re using it as a warmup, you need only your body weight or a barbell. Or use just a pair of dumbbells and circuit-train at home where you won’t annoy anyone.


Interval Training Doesn’t Work??????

For years bodybuilders were eating plain chicken breasts and doing steady-state cardio to prepare for competitions.
And everyone was happy. No one ever really questioned the efficacy of the mind-numbing cardio since bodybuilders had been stepping on stage completely shredded (with far fewer drugs) for decades.
Then, in the early 2000’s, interval training exploded onto the scene and steady-state cardio was no longer en vogue. (Chicken breasts, however, were still unseasoned and tasteless.) I was in grad school at the time and one of my thesis committee, Dr. Martin Gibala, was doing cutting-edge research showing that intervals produced equal or even better improvements in cardiovascular fitness and performance than steady-state exercise lasting several times as long. 
Other labs were cranking out research showing similar improvements in mitochondrial functions, potential for fat burning, and increased post-exercise metabolism. Finally, the 1994 study by Tremblay was brought to light and a comparison showed that interval training produced an effect that was nine times better than steady-state cardio for body composition change. 
After that, the fitness world was never the same.
Of course, the new research came as no surprise to sprinters and distance runners (yes, distance runners) who had been using intervals for years. But for the fat loss community it seemed as if we’d found the ultimate in fat burning. Steady-state cardio was dropped in favor of interval training and every coach (myself included) began to use intervals in their programming.
But was it a smart decision?

Questioning the Origin

As much as I was swept up in the excitement that surrounded intervals, one thing recently started to become clear to me: None of the studies (with the exception of the Tremblay study) had actually examined the effects of intervals on fat loss in a true randomized controlled trial.  
Sure, there was definitely a benefit for performance. But when it came to body composition only the mechanisms measured at the muscle level showed a likelihood of greater fat burning. Studies using real people to actually measure fat loss were limited.
I want to quickly go over three studies that represent the bulk of research on intervals and body composition and see if we can come to some sort of conclusion on the best method you can use to lose the most fat.

The Tabata Study

Since you can’t really go anywhere in the fitness industry without seeing or hearing about the latest and greatest Tabata workout, I just had to include this one.  All in all though, there are really only a few points I need to bring forth.

• The steady-state group in the Tabata study performed steady-state cardio. No surprise there. But the interesting part is that the Tabata group actually performed steady-state cardio instead of Tabatas for one of the five training days. In other words, 20 percent of their training days were allocated to a different method than what they were actually testing.
• The majority of the improvements in Tabata performance happened in the first three weeks and then leveled out.
• Tabatas were done at 170% of VO2 max, which is basically balls to the wall, maximal effort training on every set.

Having read all this I came to the following conclusions: Tabatas may or may not be effective for fat loss, but it certainly wasn’t measured in this study and, based on this information, there is no real reason to assume that they are better than steady-state or any other type of interval training. 
In fact, you can’t really draw any conclusions about the effectiveness of Tabata style intervals for anything considering that they were also using steady state exercise and the results are difficult to separate out. Finally, even if Tabatas are effective for fat loss, lifting weights to perform them likely won’t enable you to exert maximal effort to reach 170% of VO2 max on every set. 
If you’re lifting weights, odds are that your first set is sub maximal if you’re able to lift it again after the 10-second rest interval prescribed by the protocol.
Note that I’m not saying these protocols aren’t difficult (anyone who’s ever done a round knows exactly what I’m talking about). I’m just saying they’re not “technically” Tabatas, since you’re using sub-maximal weights.

The Tremblay Study

If there’s a single study I’ve seen used to support the use of intervals for fat loss more than any other, this has got to be it.  Having checked it out though, I’m sad to say that I was disappointed. Here are a few things I discovered:

• The steady-state group lost only 1.1 pounds. The interval group lost 0.22 pounds.  Yes, you read that right. Less than a frigging pound after 15 weeks!
• The total of the changes in skinfold measurements (taken with a caliper to assess body fat) was almost three times lower in the interval group suggesting that even though weight loss was less, body composition may have changed more. 
• The interval group actually started out with higher skinfold measurements.
• There was no dietary control in this study.

You can take from this study that doing intervals or steady-state without dietary intervention will result in a maximum of one pound of weight loss. As you know, that sucks serious ass.
And even though the total skinfolds dropped more in the interval group, the trunk skinfold decrease was pretty much the same. In fact, the main reason for the difference in the skinfolds in the first place wasn’t that the steady-state group didn’t lose fat. The big problem was that the calf skinfold of the steady-state group actually went up which obviously affects the total.  Moreover, it makes sense that the interval group (who had almost 20 percent greater skinfolds to start with) would lose more regardless of which protocol they used.
In the end, I think the body fat testing method in this study sucks. These days we use DEXA or MRI to measure body composition. And even when they did this study, hydrostatic weighing was the standard.  So why’d they use caliper testing? Skinfolds can get pretty sketchy depending on your tester.
If multiple testers are used, they can be even less reliable. (This might even be responsible for the increase in calf fat seen in the steady state group, but that’s total speculation.)
Ultimately, the body weight loss in this 15-week study pretty much blows donkey balls and I think this only goes to reinforce the obvious: you can’t neglect your diet. 

The Trapp Study

In my hunt for research comparing intervals to steady-state, I emailed my old grad school professor Dr. Martin Gibala and he admitted that the research comparing the effects of these two methods on body composition is limited. Studies with any form of dietary control are even harder to find. Fortunately he referred me to the Trapp study and I’m happy to report that there may be some support for interval training on fat loss after all. Here are the cliff notes:

• All subjects had VO2 peak test, body composition tested with DEXA, three-day dietary inventory on the first and last visit, and blood tests for fasting glucose, insulin, and leptin.
• The steady-state group started at 10-20 minutes of cycling three times per week for 15 weeks. They gradually worked up to 40 minutes of exercise per session.  Resistance on the bike was increased over the study.
• The interval group performed 8 seconds of sprinting followed by 12 seconds of easy pedaling on an exercise bike. Subjects performed as many repeats of this as possible until they reached 60 repeats of this sprint-rest cycle (about 20 minutes). In the beginning, many of the subjects couldn’t complete the rounds, so it took a few weeks to build up to it. Resistance on the bike was increased over the course of the study. This was repeated three times per week for 15 weeks.

And the Results?
• Total estimated energy expenditure was the same for both groups after 15 weeks and no dietary differences were determined.
• As expected, VO2 peak increased in both groups
• The interval group lost weight while the control and steady state groups did not. More importantly, the interval group lost 5.5 pounds of fat while the steady-state group actually gained 0.7 pounds of fat mass.
• Interestingly, the four women in the interval group that lost the least fat were also the leanest to begin with. With these women removed the interval group actually lost an average of 8.7 pounds of fat.
• The interval group had a significant decrease in central abdominal fat whereas the other two groups actually had a slight (although statistically insignificant) gain. There was also a slight trend for the interval group to lose more fat from the legs.
• The interval group increased lean mass in the trunk while the steady-state group did not.
• Both groups decreased fasting insulin, but only the interval group was different from the control group.
• Leptin decreased in only the interval group following training as would be expected when losing body mass.

So What Does All of That Mean?

In the end, the results of this study show that interval training can lead to greater fat loss than steady state training when done in the way presented. This study also suggests that this protocol might be more effective for losing fat mass and gaining lean mass, specifically in the trunk. 
Another major point to be taken from this study is that leaner people tend to lose fat slower no matter what type of protocol they’re on. This brings to light the fact that the women in the interval group actually started at 35.1% body fat and the women in the steady state group started at 31.7%. 
Although these differences were said not to be statistically significant, we can’t ignore the fact that this may have contributed to the greater success of the interval group.  You’ll also note that none of the groups in this study were exceptionally lean to begin with, so this study might not be as relevant to leaner individuals. 
In fact, the women who did not lose as much fat with the interval protocol were closer to a BMI of 21, so this might be more indicative of what would happen with a leaner person.
And even though there were diet records kept at the beginning and end of this study, it’s possible that there were dietary differences during the 15 weeks. More specifically, high intensity training is known to suppress appetite while steady state exercise is more likely to increase appetite.  This might explain why the steady state group failed to lose any fat at all when we know this method has worked for bodybuilders for years.  Without quantifying this, it’s hard to know whether the differences are from the training itself or from one group eating less than the other. 
Of course, some might argue that interval training creates a greater “post exercise burn”, but the truth is that this burn (otherwise known as EPOC) only constitutes about 13 percent of the total calories burned from interval training. So if you’ve burned 500 calories from the bout, a mere 75 calories might be burned in addition as a result of this effect.
My guess is that food likely played a large role since self-report isn’t the most reliable form of dietary constraint. (Read: the women probably ate some doughtnuts and didn’t tell anyone about it.)
The most interesting fact about this study, is the 8-second sprint followed by the 12-second light pedaling looks a lot like the Tabata protocol.  However, instead of doing the protocol for 8 repeats, the subjects in this study had to do it 60 times with maximal effort to get the fat loss benefit. 
So while doing “Tabatas” in the gym might technically be interval training, unless you’re doing them 60 times through you’re probably wasting your time.

The Bottom Line

Before I tell you what to do for the greatest fat loss, let’s quickly review a few key points:

• Tabatas have NOT been studied for fat loss. But based on the last study you should be able to tell that you’re going to have to put in a hell of a lot more work than you thought.
• The Tremblay study should never be referenced with regards to the success of interval training.
• Regardless of your cardiovascular protocol, diet is still number one when it comes to fat loss.
• The fatter you are, the more interval training will work for you. The leaner you are, the less effective it will be. This should really be no surprise.
• If you’re going to do intervals, performing 8 seconds max effort to 12 seconds, rest three times per week seems to be the only scientifically validated method for fat loss at this time.
• Oh…and you have to do it sixty times.

So What the Hell Do I Do?

The bad news, as mentioned above is that most forms of cardio performed without any dietary change aren’t really all that effective for fat loss.
The good news is that interval exercise performed with 8 seconds of max effort and 12 seconds off for a total of 60 repetitions (20 minutes) might give you an extra edge with fat loss even if you haven’t changed your diet. In fact, if you’re trying to put on lean mass, this might be a method you could use to mitigate fat gain.
Of course, if fat loss is the primary goal, you’re smart enough to know that reducing calorie intake is necessary to maximize your results. However, the additional benefit of this protocol is that the high intensity intervals will serve as an appetite suppressant making you less hungry so you won’t eat yourself into a food coma and stumble out of the local buffet like Lindsay Lohan at an after party.
So what should you do? Simply jump on a treadmill, bike, Airdyne, or local track and set the intervals in motion. To make the whole process easier, you could even pick up a Gym Boss timer to alert you to when you should stop and start each set. 
This will allow you to focus on your intervals instead of watching the clock (which consequently is difficult to do when your vision is blurred from the tears associated with this protocol).
So, despite all the interval hype, it appears that only one interval protocol holds water when it comes to scientifically measured effectiveness.  If you want to lose fat, go 8 seconds on and 12 seconds off for 60 rounds, and kill it! (Just don’t kill yourself.)

Mark Young is an exercise and nutrition consultant from Hamilton, Ontario, Canada.  Rather than blathering on about credentials and clientele, he would prefer you check out his website and check out the content for yourself.

Tabata, I., et al. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Med Sci Sports Exerc. 1996 Oct;28(10):1327-30.
Tremblay, A., et al. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism. 1994 Jul;43(7):814-8.
Trapp, EG., et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women.  International Journal of Obesity (2008) 32, 684–691.
The result of interval training or steady-state cardio?
The result of interval training or steady-state cardio?

<img alt="Are intervals really that effective for fat-loss?” border=”0″ src=”; style=”margin-top: 100px;” />

Are intervals really that effective for fat-loss?

Somehow the old school bodybuilders didn't mind the mind-numbing cardio.

Somehow the old school bodybuilders didn’t mind the mind-numbing cardio.

<img alt="Wait. To lose fat you have to work out and eat right? Whoa!” border=”0″ src=”; style=”margin-top: 100px;” />

Wait. To lose fat you have to work out and eat right? Whoa!

© 1998 — 2010 Testosterone, LLC. All Rights Reserved.

Blast: Metabolic Interval Training

Beg, Borrow, and Steal to Get Ripped Fast

Metabolic interval training, or “Blast” as I call my version of it, is an exercise protocol that utilizes the latest science of endocrinology and performance training to totally tax the body’s major energy systems. The main focus of Blast is to maximize the use of stored adipose tissue (fat) as a fuel source, both during and after exercise.
Blast is a “beg, borrow, and steal” type of training, taking ideas from every aspect of exercise to make a superior training session that incinerates fat at an incredible rate. In a given session, you could experience a combination of standard resistance training, calisthenics, body-weight training, gymnastics, reactive training — that’s plyos for you old-schoolers — Olympic movements, kettlebell training, and strongman events in one integrated interval training session.
These sessions are fast paced, involving intervals of hard work and short rest periods to produce maximum fat loss in the shortest period of time. And don’t just think gymrats are the only ones who thinks this works — it’s backed up by science.
In a 2008 study presented in the Journal of Strength and Conditioning, metabolic interval-type training had a ten-fold greater fat loss when compared to either aerobic exercise or weight training individually. Numerous other studies found in The Journal of Medicine and Science in SportThe European Journal of PhysiologyThe Journal of Sports Nutrition, and The European Journal of Applied Physiologyover the last eight years have supported this.
Some research showed that metabolic interval training actually had as much as a 50 percent increase in the use of fat as a fuel source during exercise. One research study showed that this type of training produced EPOC (Excess Post-Exercise Oxygen Consumption) that lasted 16 to 48 hours.
As a personal trainer and performance coach, I have to produce results fast or I’ll find myself without a job. As an athlete myself, I’ve trained about every way known to man in the last 30 years, but I’m always looking for more productive ways of doing things. After reading the research, I began working on how to incorporate this type of training into what we do at my gym.
Over the last twelve months I’ve been working on the Blast training protocols with all my clients: professional and college athletes, bodybuilders, strongmen, MMA fighters, police officers, firefighters, powerlifters, and MILF’s (Moms in Love with Fitness — get your mind out of the gutter). Through the use of Polar heart rate monitors and the BodyBugg by APEX, we found that the average client burned 11kcal per minute during exercise and had an elevated metabolism post exercise.
I haven’t seen the 16 to 48 hours of EPOCH that some of the science has reported, but my clients have maintained a metabolic “afterburn” of four hours on the average.
One thing that I didn’t expect was that this type of training helps aid recovery. Like “feeder” sets, Blast does a great job of flushing out the metabolic garbage from muscles by pumping tons of blood through them. GPP (general physical preparedness) is most assuredly improved by doing metabolic interval training.
Enough science. Time to show you how to do it!
You can work this in as a stand-alone session or build it into your body part splits. I’ll give you some loose guidelines of how we do it for a stand-alone session.

Work and Rest

We start with a split of 30 seconds of work to 20 seconds of rest. We’ll work up to 45 seconds of work and as little rest as 15 seconds.
Week 1: 
Week 2: 
Week 3: 
Week 4: 

Exercise Selection and Load

The bigger the movement the better, but the load doesn’t need to be super high. I personally prefer compound movements across as many joints as possible and a load that allows 15 or more reps to be completed in the interval.

Stations and Rounds

Twelve stations and three rounds is what seems to work best. Much more than that and my clients — regardless of their conditioning — seem to just shut down. Our typical session lasts about 45 minutes.

Breaks Between Rounds

We range between 90 and 120 seconds of rest between rounds. That’s generally enough time to wipe your face off and get a sip of water.
 The rest between rounds can be adjusted depending on condition of those in a training session. Some of our high school teams have gone up to 60 seconds work and 15 seconds rest.


Training sessions per week should be limited to no more than four. Most of my clients lift weights two times per week and then add one to two Blast sessions.


How much effort should you put into each set and every round? I guess that depends on what you want to get out of the training? More effort = better results!

A “Regular Gym” Example

At my facility we have all kinds of specialized equipment. Your gym probably doesn’t. Sorry about that. But here’s a session example you can do with common equipment that’ll leave you sucking gas and dripping sweat.

Bonus Round

Fifteen to twenty minutes of good old low- to moderate-intensity cardio. The calories burned during this time period are almost exclusively fat because of the hormonal cascade you set up during the metabolic interval training.

Same Session Blast

Like the idea but aren’t super keen on doing an entire separate session? Then just toss it in at the end of your workout.
Start out with no more than three exercises and three rounds at the end of your main training session. I’ve done the same body parts that I just trained, and I’ve just worked feeder sets for what I hit the day or two before. Both ways produce great results.
Give this session a shot and let me know what you think!

About Chad Coy

Blast: Metabolic Interval Training

Chad Coy is a strength and conditioning coach, a drug-free powerlifting champion, and a noted strongman competitor. He’s currently the owner of ClubFitness24 by Powerhouse Gym and Parisi Speed School, Kokomo, Indiana.

© 1998 — 2010 Testosterone, LLC. All Rights Reserved.


Interval training can cut exercise hours sharply

LONDON – People who complain they have no time to exercise may soon need another excuse.
Some experts say intense exercise sessions could help people squeeze an entire week’s workout into less than an hour. Those regimens — also called interval training — were originally developed for Olympic athletes and thought to be too strenuous for normal people.
But in recent years, studies in older people and those with health problems suggest many more people might be able to handle it. If true, that could revolutionize how officials advise people to exercise — and save millions of people hours in the gym every week. It is also a smarter way to exercise, experts say.
High-intensity interval training is twice as effective as normal exercise,” said Jan Helgerud, an exercise expert at the Norwegian University of Science and Technology. “This is like finding a new pill that works twice as well … we should immediately throw out the old way of exercising.”
Studies on intense training have been published in sports medicine journals and have largely been based on young, healthy people. Experts say more studies are needed on how older and less fit populations handle this type of exercise before it can be recommended more widely.
Intense interval training means working very hard for a few minutes, with rest periods between sets. Experts have mostly tested people running or biking, but other sports like rowing or swimming should also work.
Helgerud recommends people try four sessions lasting four minutes each, with three minutes of recovery time in between. Unless you’re an elite athlete, it shouldn’t be an all-out effort.
“You should be a little out of breath, but you shouldn’t have the obvious feeling of exhaustion,” Helgerud said.
In Britain and the U.S., officials recommend that people get about 2 1/2 hours each week of moderate exercise. Those guidelines target a mostly sedentary population and are intended to help with weight control and heart health, not boosting fitness levels, increasing strength or endurance.
Some experts have cautioned that ordinary people shouldn’t substitute their regular exercise routine for intense training.
“There isn’t enough evidence to say people should do one or the other,” said Gary O’Donovan, a sports and exercise expert at the University of Exeter. “Any bout of exercise has the potential to improve your blood pressure or lower your cholesterol, and it doesn’t necessarily have to be intense.”
Still, O’Donovan said there was a dose-response relationship between intensity and exercise and more intense exercise would probably produce better benefits.
Helgerud says the time people spend in the gym could be slashed dramatically if they did interval training instead. He said officials have been too afraid of recommending intense training for fear it would be too much for some people.
“I’m much more afraid of people not exercising at all,” he said. “Inactivity is what’s killing us.”
When compared to people on a normal exercise routine, like jogging, research has shown those doing interval training can double their endurance, improve their oxygen use and strength by more than 10 percent and their speed by at least 5 percent. Even studies in the elderly and in heart patients found they had better oxygen use and fitness after doing interval training.
Still, experts advise people to consult a doctor before starting any fitness program.
For Adamson Nicholls, a 36-year-old Londoner and martial arts enthusiast, interval training is a way to boost his endurance so he can outlast sparring opponents. “It’s a shortcut to explosive fitness,” he said, adding the training resulted in snappier and heavier punches.
Using interval training, Nicholls got into top shape last year in about six weeks with weekly 45-minute sessions. He estimates the same level would have taken about three months via regular training.
Experts say that’s because intense bursts of activity are precisely what the body needs to build stronger muscles. Traditional workouts lasting an hour or more simply don’t push the body enough.
“A lot of the (benefits) from exercise are due to a stress response,” said Stephen Bailey, a sports sciences expert at the University of Exeter. “If you disturb your muscles, there’s an imbalance created and your body will start signaling pathways that result in adjustments.”
Bailey said intense bursts of exercise help the body to convert one type of muscle fiber into another type that uses oxygen more efficiently and is capable of exercising a lot longer. Even though interval training only takes a few minutes, its effects last for hours.
“You’ve exercised at such a high intensity that you’re going to create a massive disturbance in your muscles,” Bailey said.
That creates a higher metabolism for several hours afterward, which the body will bring down by burning fat and carbohydrates.
“This is definitely the way forward to save time on your exercise,” Nicholls said. “The results are worth it.”


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