High-Intensity Training

Get Fit With High-Intensity Workouts

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Running can be considered a form of high-intentisty aerobic exercise. Carsten Koall/Getty Images

What is high-intensity training and what are its principles and benefits? In plain language, the three main variables in fitness training are intensity, volume and frequency. These definitions essentially apply to any type of training you do, from weights to track interval training or road running and cycling.

Intensity is the difficulty in performing the exercise. For weight training, intensity means how heavy you lift.

For cardio, it could mean how fast you run or walk.

Volume is how much of any exercise or how many exercises you do in a session or over time.

Frequency is how many sessions in a week, month or year that you complete at the intensity and volume you choose.

High-Intensity Aerobic and Anaerobic Exercise

Aerobic exercise
In addition to weight training, an overall exercise program may include elements of aerobic (cardio) and anaerobic training. Aerobic training is what you will recognize as treadmill jogging or walking, cycling or swimming at a low to moderate pace up to a point at which you can still carry on a conversation, even if you are breathing a little heavy. You should be able to keep this up for 30 minutes or more.

Low to moderate intensity aerobic exercise is at a heart rate of approximately 50 to 70% of your maximum heart rate. At this intensity, and with reasonable fitness, you should be able to supply the exercising muscles with sufficient oxygen to keep them contracting and performing for some time.

Aerobic means “with oxygen.&rdquo

Anaerobic exercise
In contrast, anaerobic exercise is at an intensity at which your muscles’ requirements for oxygen exceed the amount you can supply by breathing and via your blood supply. At this exercise intensity, you will stop sooner rather than later because the muscles will fail to function.

At this level of intensity, your heart rate may be at 90 to 100% of your maximum heart rate. This is clearly high-intensity exercise. Weight training for strength with heavy loads is usually anaerobic exercise for short bursts of effort.

High-intensity Aerobic Exercise

Now, you may have noticed a gap in the heart rates discussed above: the range from 70 to 90% of your maximum heart rate. When you start to exercise beyond about 75% of your maximum heart rate (where you can’t talk much because you are breathing hard), you are getting into what can reasonably be described as high-intensity exercise, even though it may still be aerobic. For fitter individuals, this may be fast running, cycling, rowing, swimming, or even race walking. At this intensity, you will be less likely to be able to exercise for the same duration as you could with moderate aerobic intensity.

It’s worth noting that this is the intensity zone where you will burn the most calories (and fat) during and after exercise — duration of exercise being a factor.

Lifting moderately heavy weights intermittently will put you in this zone, but your session won't be long enough to match a 45-minute run or cycle at this intensity. High-intensity aerobic and anaerobic training is the king of calorie burning, but you have to do it for sufficient time to get the most benefit.

High-Intensity Interval Training (HIIT)

High-intensity interval training is a system of training that utilizes short bursts of repeated running or cycling or similar activity. A HIIT training workout in a cycle spin session might look like this:

  1. Warm up. Spin for five minutes at slow pace or resistance (60%).
  2. Cycle for one minute at about 85% of your maximum effort. Spin easy for thirty seconds. Do this five times.
  3. Recover at slow pace as for step 1.
  4. Cycle flat out for fifteen seconds, rest for twenty seconds. Do this ten times.
  5. Recover at slow pace as for step 1.
  6. Cycle for three minutes at 75% of you maximum. Spin for one minute. Do this three times.
  7. Warm down similar to step 1.

This sort of training is common in gym cycle spin classes.

You could use a similarly structured intensity running program at an athletic track or even on a treadmill (if you’re careful), or even when swimming or rowing.

Principles of High-Intensity Training

In the weight training industry, HIT became a term associated with Arthur Jones and the Nautilus gymnasium machines in the 1970s. Later, a number of disciples, such as well-known trainers and competitors Mike Mentzer, Matt Brzycki, Stuart McRobert and others, helped add to its popularity. Supporters of this style of training formed a loose collection of enthusiasts who, I think it is fair to say, disdained more conventional training methods and were very vocal about it.

The general principles of HIT, as it refers to weight training, are summarized in the following points:

  • You should do your repetitions and sets with a load that will lead to complete muscle failure at the end of each set. This means choosing a relatively heavy weight for 8 to 12 repetitions of each exercise. Your muscles should feel exhausted at the end of your session.
  • If you reach complete failure at the last repetition of just one set, further sets may not be required. I take this to mean genuine failure at which point you are completely unable to move the weight to the desired position with good form -- even with the most focused effort.
  • Because of the fewer sets advocated, HIT enthusiasts say that less time is required in the gym to do full-body workouts and to achieve results superior to more traditional workouts involving less intensity and more sets.
  • You should attempt to increase the load at each successive workout, which is said to rapidly provide strength and muscle development.

That sums up the main principles of HIT as it applies to this school of weight training. Even so, the discussion and argument over this topic remains fodder for weight training forums all over the world.

I know of no scientific studies that support the somewhat vague instructions used in this HIT training. These seem to be largely based on what is known to work, anecdotally, and what has been documented in authoritative strength and conditioning books and journals.

My view is that HIT is a nice promotional term, but the fundamentals are confusing and indistinct. When it comes to bodybuilding and weight training — like many other pursuits in life — the harder you work, the luckier you get. Still, not everyone can work this hard without getting hurt.

Can you get hurt practicing high-intensity training? Yes you can.

Genetically gifted bodies (or bodies protected by steroids) may cope with this sort of training and produce outstanding results. But this is not a useful predictor of the value of HIT weight training for all, because it tends to be self-selecting of the fittest.

Summing Up High-Intensity Training

Fitness base
High-intensity training of any type is not for everyone. You need a base of fitness before you try this, or you can get hurt or so discouraged that you stop exercising altogether. That applies to weight training, cardio, or interval training. Think of the classic expression: "no pain, no gain." Serious high-intensity training certainly fits that mold.

Circuit Training
Combining weights with leg movement exercises in a "circuit" is an excellent way to train at high-intensity.

Benefits
The advantages include revving up your metabolism and giving you an afterburn -- where you burn more calories and fat at rest. Second, you can get through your exercise sessions in less time.

According to the new exercise guidelines released by the American College of Sports Medicine and the American Heart Association, you can choose from the following, or a mix of both, and get adequate health benefits:

  • Moderately intense cardio 30 minutes a day, 5 days a week OR
  • Vigorously intense cardio 20 minutes a day, 3 days a week

Safety
High-intensity training will raise your body temperature faster than more moderate training and cause you to sweat more. Drink plenty of fluids and avoid hot weather and full sun as much as possible. You should also get medical clearance before you begin high-intensity training.

High-intensity training is definitely worth considering as an exercise tool to boost your fitness, body shape and fat burning. Work up to it gradually for a safe and effective experience.

Sources:

Haskell, W.L. Physical Activity and Public Health: Updated Recommendation for Adults From the American College of Sports Medicine and the American Heart AssociationMedicine & Science in Sports & Exercise, 2007; 39:1423-1434.

Kraemer W.J., K. Adams, E. Cafarelli, G.A. et al. American College of Sports Medicine. Position stand on progression models in resistance training for healthy adults. Med. Sci. Sports Exerc.2002; 34:364-380.

LaForgia J, Withers RT, Gore CJ. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci. 2006 Dec.24 (12):1247-64. Review.

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