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What You Need to Know About High-Intensity Interval Training

Updated: Jan 16

HIIT Training

I have a strong urge to pique your interest in this old school system of training.  You see, high-intensity interval training (HIIT), while around for nearly 100 years, has had a major resurgence in gyms everywhere over the past 10 years, owing in large part, to a veritable blizzard of research papers extolling its benefits.  I’ve also a strong urge to pique your interest even further in a variant of traditional HIIT, one that involves the use of weights.

Actually, I’m pretty excited about HIIT!  I wasn’t until I visited the USMC Base in Iwakuni (Japan) last year and learned that HIIT was the method of training in use there.  “Naw,” I said to myself.  “That can’t be!  There are a lot of systems of training that deliver far superior results for battle-ready warriors.” 

Well, I found out that there isn’t. 

Only, the Marines call it “High-Intensity Tactical Training” (HITT).  Have a look at the USMC web site that’s dedicated to HITT: 

What is High-Intensity Interval Training?

In 1994, at the Physical Activities Science Laboratory at Laval University in Canada, Angelo Tremblay and some of his colleagues tested the long-held belief among most exercise and medical professionals that long, slow cardio at a low intensity is superior for fat loss. In fact, they compared the impact of moderate/low intensity to high-intensity interval training in hopes of finding what was superior for fat loss.

One group did 20 weeks of endurance training while the other group did 15 weeks of high-intensity interval training. The cost of total energy expenditure was much higher in the endurance-training group than in the interval group.

Additionally, Tremblay and his associates found that the endurance group burned nearly twice the amount of calories during training than did the interval group. Lo and behold, skin-fold measurements showed the interval training group lost more body fat than the endurance-training group.

This may not seem to make sense at first glance, but the team found, “When the difference in the total energy cost of the program was taken into account...the subcutaneous fat loss was ninefold greater in the HIIT (interval training) program than in the ET (endurance training) program.”

In layman’s terms, interval training trumped long, slow cardio for fat loss!  The interval trainees got nine times the fat loss for every calorie burned during training.

This is why interval training has so many die-hard advocates and supporters.

Science confirms that interval training is highly effective for fat loss. “Compare the physiques of top-level sprinters to top-level distance runners” is a simplistic, logical response many give when asked why they feel interval training is superior.

Izumi Tabata has conducted research for the National Institute of Fitness and Sports in Tokyo, Japan. In terms of aerobic benefits, Tabata demonstrated that a program of 20 seconds of all-out cycling followed by 10 seconds of low-intensity cycling performed in a sequence eight times for a total of 4 minutes was as beneficial as 45 minutes of long, slow cardio!

Tabata training is now a popular form of interval training. Some popular methods of Tabata training include jumping rope, burpees, and kettlebell swings, along with many others. Numerous studies also confirm the effectiveness of interval training as an enhancement to aerobic capacity.

At this point, it probably sounds like a no-brainer; just do interval training all the time and get lean.

Not so fast.

Muscle grows from exercise via muscle damage, mechanical tension, and metabolic stress. Intervals generally work the same way, so they must be treated with respect.

The CNS (central nervous system) is primarily affected by high-intensity work and takes at least 48 hours to recover, so interval training requires adequate recovery very similar to intense resistance training.

Interval training, in the true sense, is all-out.

The studies that confirm the effectiveness of HIIT have subjects performing intervals with 100% intensity. Whether from personal problems or intense training, stress is imposed; when the right amount of stress is imposed from training, you adapt and improve.

Remember, if you are training intensely multiple times per week and have a full-time job and a family, stressors are acting upon you in all directions. Without proper planning, training will no longer serve as a catalyst to meet your physical goals; it will break you down.

The more your training evolves as you become more fit, the more stress you impose on yourself. 

An intermediate trainee may be able to do 3 days a week of interval training, whereas a more advanced one may be able to do only 1–2 days a week; high intensity, high volume strength training with short rest intervals is interval training in itself.

Adaptations to your training are a consolidation of imposed stressors, which determine your muscle gains, fat loss, and strength levels.

Like intense resistance training, extreme stress is placed on the central nervous system and musculoskeletal system.

Look at sprinters. They produce huge force while sprinting, and this places a large amount of stress on muscles, connective tissue, and the CNS.

If you have health problems or have not been training on a regular basis, think twice about implementing intervals, and consult your physician before beginning interval training. The risk of overuse injuries will drastically increase if intervals are overdone. Rushing into these types of workouts before you have a sufficient base will greatly increase your chance of injury.

 Start slowly.

Try just one or two high-intensity intervals at first. As conditioning improves, begin to challenge yourself.

Barbell Complexes

Do you want to find out what you are made of?

Try barbell complexes.

Not only are these one of the greatest metabolic conditioners and fat loss modalities, they are also one of the best tests of pure guts.

Time to “put up or shut up!” 

If you are doing barbell complexes and find they are not challenging, you are not loading the bar with enough weight or not giving sufficient effort. Barbell complexes potentially serve as a viable alternative to sprints for heavier athletes.  Barbell complexes are performed as quickly as possible, moving exercise to exercise with no break.

To construct a complex, you may do 5–8 squats, followed by 5–8 squats to presses, followed by 5–8 good mornings, followed by 5–8 power cleans, followed by 5–8 bent-over rows, and finally finished off with 5–8 deadlifts.

The beauty of barbell complexes is they can be arranged somewhat specific to the muscle group being worked; if you train legs Monday and chest Tuesday, it would be counterproductive to do very intense intervals that emphasize legs and lower back; this will not let the muscles recover.

On a leg day, a barbell complex might look something like this: overhead squats, squats, reverse lunges, front squats, and Romanian deadlifts.

On a back day, it might look something like this: good mornings, power cleans, hang cleans, deadlifts, and bent over row.

Sound tough?

Your fortitude will be in for a test.

Some points to remember when performing complexes:

  • Use compound exercises

  • Perform exercises as fast as possible while maintaining proper technique

  • Do not rest between exercises

  • Try your best not to drop the bar

  • Start with an empty bar and add weights in increments of 5 or 10 pounds

  • Do 5–7 exercises per complex, each set consisting of 5–8 repetitions

  • Rest 1 to 3 minutes between sets, do not exceed 4 sets, do not exceed 15 minutes’ total duration

  • Barbell complexes are intense interval workouts and are included in your total of interval workouts

Variable Manipulation

When progressing through barbell complexes, be intelligent in how you increase the intensity!

Just piling more pig iron on the bar every session will result in cessation of progress. 

These are some variables you can manipulate to increase intensity:

  • Rest periods—decreasing the rest periods increases intensity. If a 3-minute rest interval is becoming easy, try using the same weight but decreasing the rest interval between complexes; knock off 15–30 seconds between each session, eventually working down to a 1-minute rest interval. All of a sudden you are accomplishing 4 complexes in the same amount of time it used to take to do 2.

  • Weight on the bar—increasing weight on the bar increases intensity. But remember, if you cannot complete more than one set, decrease the bar weight.

  • The number of sets—increasing the number of sets increases intensity. After you get up to 4 complexes, pile on more pig iron.

Barbell complexes can expedite fat loss but also expedite overtraining; I do not suggest you do them more than twice a week. These will test you mentally and physically.

I have given you some practical examples, so try those. I have also laid out the variables taken into account when designing a complex. Play around and find out what works best for you.

kettlebell interval training

Kettlebell Interval Training

In the fitness industry, things run in extremes.

Just take a look at flexibility; studies have shown static stretching pre-workout decreases force production, yet now some advocate if you ever stretch you will be weak and prone to injury. 

On the other side are those who believe that yoga is more important to MMA fighters than sparring. Think of the other extremes: no carbs, low fat, BOSU balls, and the list goes on, friends. 

Kettlebells fall into this extremist camp.

Many times advocates will imply you can develop the endurance of a marathon runner, physique of a bodybuilder, strength of an elite powerlifter, flexibility of a yoga instructor, and speed of a world-class sprinter, without pig iron or any other modalities.

This is patently false!

A kettlebell looks like a cannonball with a handle welded to the top. For centuries, kettlebells have been used for strength training by top Russian athletes and for stress relief by those rotting in gulags.

If you are not sure what a kettlebell is, think of the old-time cartoons, like Bugs Bunny, where strongmen tossed around those odd-shaped cannonballs with handles. 

In the days of yesteryear, circus strongmen used these implements as part of their acts. Today, many folks are integrating kettlebell training into their strength and conditioning regimens.

Advocates of kettlebell training are quick to point out that kettlebells can simultaneously build core stability, coordination, endurance, strength, power, and flexibility.

Okay, but what about fat loss?

A recent study at the University of Wisconsin–LaCrosse demonstrated that intense kettlebell intervals burn calories at the same rate as a mile run at a 6-minute pace (that is, 1,200 calories an hour). Clearly, fat loss is a byproduct of intense kettlebell training.

Three effective kettlebell exercises are clean and jerks, snatches, and swings.

Here is a good circuit for conditioning and fat loss; complete the circuit without a break:

  • 10 Kettlebell Swings

  • 30 seconds of Jump Rope

  • 5 Clean and Jerks (each side)

  • 30 seconds of Jump Rope

  • 5 Snatches (each side)

  • 30 seconds of Jump Rope

Follow this circuit with a 1–4-minute break and repeat the circuit 3 times. Remember, these circuits are an intense form of interval training if you give 100%. These count in your weekly total of interval workouts, so don’t try and do a barbell complex twice a week, and then do this circuit 2–3 times. All intense training is a stressor; without recovery, you will be in a perpetual catabolic state.

Jumping Rope

Jumping rope can burn up to 1,000 calories per hour, making it one of the most efficient fat-burning workouts available.  Unlike other forms of interval training that are much more stressful on the CNS, muscles and connective tissues are also spared significant stress while jumping rope.

Furthermore, jumping rope tone muscles throughout the entire body and develops lean muscles in all major muscle groups. Of course, jumping rope optimizes conditioning and maximizes athletic skills by combining agility, coordination, timing, and endurance. Most importantly for you, it can help burn body fat.

Jumping rope is very practical because, unlike advanced kettlebell exercises, the learning curve is easy. Jump ropes are portable and inexpensive and can be purchased for less than $10. If you go on vacation, throw your jump rope in your bag and you have no excuse to not do your conditioning work.

For your jump-rope program, start by jumping rope 30 seconds and resting 1 minute for 6 sets. Depending on ability, add 10 seconds per week or workout. Make it your goal to complete 6 sets of 3 minutes of jump rope, with a 30-second rest interval. When you are able to complete 6 sets of 3 minutes, body fat will have melted off and conditioning will be at a whole new level.

A Few Last Words

Fat loss comes from strength training and dieting.  If you’re depending on long, slow cardio, or even interval training for fat loss, your body is telling you that your diet is not in check. 

The age-old truth is still the same truth today: Strength training and diet are the keys to fat loss.

About Frederick Hatfield

Frederick C. Hatfield, MSS, Ph.D., is Co-founder and President of the ISSA. Dr. Hatfield, (aka "Dr. Squat") won the World Championships three times in the sport of powerlifting and performed a competitive squat with 1014 pounds at a bodyweight of 255 pounds (more weight than anyone in history had ever lifted in competition).

Dr. Hatfield's former positions include an assistant professorship at the University of Wisconsin (Madison) and Senior Vice President and Director of Research and Development for Weider Health and Fitness, Incorporated. Dr. Hatfield was honored by Southern Connecticut State University when they presented him with the 1991 Alumni Citation Award.

He has written over 60 books (including several best-sellers) and hundreds of articles in the general areas of sports training, fitness, bodybuilding, and performance nutrition. He has been a coach and training consultant for several world-ranked and professional athletes, sports governing bodies, and professional teams worldwide. Dr. Hatfield qualified for the 1998 World Championships in Olympic Lifting and competed in the Master's Division.

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