Woman on treadmill

Types of cardio

There are three popular types of cardio:

  1. Steady-state training
  2. Interval training
  3. Circuit training

The three types of cardio are quite different from each other and offer different benefits. In How to do cardio, I only defined steady-state training. Let’s now look at the applications, advantages, and disadvantages of each type of cardio separately, as well as the exercises and activities that are most suitable for each type. You can then use the different types of cardio in a strategic fashion, in accordance with your goals, preferences, and level of experience. Steady-state training, interval training, and circuit training programs have been provided for you in the Cardio Training Programs section.

Steady-state training

What is steady-state training?

As explained in How to do cardio, steady-state training involves increasing your heart rate to a target training zone and keeping it there for a prescribed period of time. The benefits that you derive depend on the zone in which you choose to train.

Applications of steady-state training

Although advanced individuals can use steady-state training in the anaerobic zones to develop anaerobic metabolism, it is usually confined to the aerobic zones and used to develop aerobic metabolism and endurance. (Aerobic respiration, anaerobic respiration, and the basics of endurance science were covered in Introduction to cardio.)

Improving aerobic metabolism is extremely important because the majority of the physical functions and activities that your body undertakes (for example, digestion, breathing, walking, and sleeping) are powered by the aerobic metabolism. Even anaerobic exercises, such as sprinting, rely on the aerobic metabolism to restore the body to neutral after exercise. That’s why anaerobic exercises force you to breathe heavily even though they themselves require little oxygen. Since all physical functions and activities rely on your aerobic metabolism, having a weak aerobic ‘engine’ will limit everything you can do. By strengthening your aerobic metabolism using steady-state training, you will be able to perform better at everything else.

Advantages of steady-state training

  • Great for developing VO2 max, aerobic metabolism, and endurance
  • Improves VO2 max and aerobic metabolism by boosting the efficiency of your cardiorespiratory system and increasing the density of mitochondria and fat-burning enzymes in your muscle cells
  • By enhancing your aerobic metabolism, reduces your body’s demand for anaerobic respiration at more vigorous levels of intensity. This delays the onset of your lactate threshold, which enables you to train at a higher percentage of your VO2 max
  • Decreases your blood pressure and heart rate, both at rest and during exercise, as a result of improving cardiorespiratory efficiency. In turn, the reduced blood pressure and heart rate enhance your ability to relax and focus
  • By increasing the availability of fat-burning enzymes in your muscle cells, enhances your body’s ability to use fat as a fuel source
  • Not as stressful on the cardiorespiratory system as is interval training
  • Generates less metabolic waste and cellular damage than interval training does
  • Workouts can be recovered from relatively quickly

Disadvantages of steady-state training

  • Doesn’t build strength, power, or muscle mass beyond a very low baseline level
  • The lengthy workouts can be very boring for some people (Tip: Try listening to an audiobook)
  • Its repetitive nature can increase the risk of repetitive stress injuries
  • If used excessively, can lead to muscle loss, especially in the presence of inadequate caloric intake and in the absence of weight training

Suitable exercises for steady-state training

Exercises and activities that are most suitable for steady-state training include:

  • Aerobics
  • Dancing
  • Swimming
  • Jogging and running
  • Stair climbing
  • Cycling
  • Rowing
  • Elliptical cross-training

All of these activities allow you to increase and maintain a heart rate sufficient for aerobic training. With some activities, you increase your heart rate by increasing your pace (for example, jogging and swimming); with other activities, you can increase your heart rate by either increasing your pace or the level of resistance (for example, the rowing machine).

The best exercises and activities for steady-state training are those that get the major muscles of both your upper body and lower body involved, while keeping the stress and impact on your joints to a minimum. Of course, it’s best to alternate the types of exercises and activities that you use so as to avoid getting bored, as well as prevent your body from adapting to a specific exercise or activity and therefore require less energy to undertake it.

Interval training

What is interval training?

Interval training involves alternating between different training zones in the same workout, for example, repeatedly switching between three-minute intervals of moderate-intensity and vigorous-intensity exercise. This can significantly increase the total volume and/or average intensity of your training. An advanced and very popular form of interval training, known as high-intensity interval training (HIIT), involves alternating between intervals of maximal-intensity and lower intensity recovery exercise.

Applications of interval training

Interval training, especially HIIT, is usually used to improve anaerobic metabolism and lactate tolerance. However, since it involves alternating between intervals of lower and higher intensity exercise, it, of course, also improves aerobic metabolism.

Advantages of interval training

  • Improves anaerobic metabolism by increasing the amount of enzymes that are necessary for anaerobic respiration
  • By boosting anaerobic metabolism, empowers you to work at higher intensities for longer and with much more efficiency
  • Improves your body’s ability to transition between aerobic and anaerobic metabolisms (known as your metabolic flexibility)
  • Enhances your lactate tolerance
  • Improves explosive sporting performance
  • More effective than steady-state training at strengthening your cardiorespiratory system because it gets your heart, lungs, and breathing apparatus working much more vigorously
  • The workouts are shorter and can therefore be less boring
  • The intensity of the workouts, especially HIIT workouts, activates Type II muscle fibers, which means that HIIT can build more muscle than steady-state training can (muscle fibers are explained in Muscle structure, in the Weight Training Guide)
  • The intensity of the workouts can stimulate the release of muscle-building hormones, such as testosterone and growth hormone
  • Generally burns more kilocalories than steady-state training does, so it can produce weight-loss results similar to those of steady-state training in a shorter period of time, with less risk of muscle loss
  • Produces more of an ‘after-burn’ effect than steady-state training does

Note: Much has been made of the so-called after-burn effect, more technically known as excess post-exercise oxygen consumption (EPOC). EPOC is a measurable increase in metabolic rate and oxygen consumption that can persist for several hours after a workout. The increases are part of the body’s recovery process. The more intense the workout was, the longer the EPOC phase will be.

During EPOC, the body burns more kilocalories than it would have done if the training had not occurred. However, the effect is actually very small, even after lengthy and very intense sessions of cardio. What’s more, heavy weight training is now believed to produce a more significant after-burn effect than any type of cardio can.

Disadvantages of interval training

  • The intensity of the workouts, especially HIIT workouts, can be very stressful and difficult to maintain
  • If overused, can lead to persistent stress- and anxiety-related symptoms, such as increased heart rate even while resting, difficulty sleeping, and an inability to relax and focus
  • Easier to overtrain with interval training (especially HIIT) than it is with steady-state training
  • Higher risk of injury than there is with steady-state training
  • At very high intensities, rapidly depletes muscle glycogen stores. Once depleted, the body is more likely to use protein for energy, in which case there will be less protein available to repair muscle tissue damaged by exercise. This makes post-exercise protein consumption more important

Suitable exercises for interval training

Exercises and activities that are suitable for interval training include:

  • Running
  • Cycling
  • Rowing
  • Elliptical cross-training

Generally speaking, the other activities listed for steady-state training are not suitable for interval training, especially HIIT, because they often can’t produce and adequately maintain the required level of intensity. Arguably, the most ideal exercises for interval training are rowing and elliptical cross-training because they get your whole body involved while keeping the stress and impact on your joints to a minimum.

Circuit training

What is circuit training?

Like steady-state training, circuit training involves keeping your heart rate in a target training zone for a prescribed period of time. However, instead of using a single exercise or activity, such as jogging, you perform a series of different exercises with little to no rest between them. Different types of exercises can be used, including weight training exercises.

The series of exercises used in circuit training workouts is known as a circuit and alternates between primary exercises and active-rest exercises. The purpose of the primary exercises, which are of a higher intensity than are the active-rest exercises, is to get your heart racing. The purpose of the active-rest exercises is to allow you to momentarily catch your breath before the next primary exercise, while also keeping you moving (hence ‘active’ rest).

Here’s an example of a circuit that I have deliberately kept very short and simple:

StepPrimary exercises (40 seconds)Active-rest exercises (20 seconds)
1Burpees (YT)Inch worm (YT)
2Jumping jacks (YT)Lateral crab crawl (YT)
3Break dancer (YT)Bird dog (YT)

As you can see, the circuit is split into steps. If you were to follow this circuit, you would do all of the following without resting:

  • In Step 1, you would do burpees for 40 seconds and then the inch worm for 20 seconds
  • In Step 2, you would do jumping jacks for 40 seconds and then the lateral crab crawl for 20 seconds
  • In Step 3, you would do the break dancer for 40 seconds and then the bird dog for 20 seconds

That would be the end of your workout, unless you repeat the circuit. You could also choose to do each step twice before moving on to the next step.

Applications of circuit training

Depending on the types of exercises that you use, circuit training can help you to develop both aerobic and anaerobic metabolisms. However, generally speaking, it is less efficient than steady-state training is at developing aerobic metabolism and less efficient than interval training is at developing anaerobic metabolism.

The main appeal of circuit training is that, depending on the types of exercises that you use, it can help you to develop aspects of health and fitness that can’t be developed using the other forms of cardio. For example, if you use plyometric exercises, you will develop the explosive abilities of your muscles and tendons, or if you use agility drills, you will develop agility.

Note that even though you can use weight training exercises, circuit training can’t be used to develop muscular size and strength beyond a low baseline level. The reason is that it is not compatible with some of the important principles of effective weight training, such as muscle flushing and time under tension. This is why weight training circuits have been included only in my beginner weight training programs, where they serve to promote neuromuscular adaptation and build muscular endurance.

Advantages of circuit training

  • Can be used to develop a variety of aspects of fitness, from aerobic and anaerobic metabolism to speed, power, agility, flexibility, coordination, and balance
  • Workouts can be designed around improving performance in specific sports
  • Countless exercises to choose from, as well as numerous ways in which to structure the circuits
  • Workouts can actually be fun

Disadvantages of circuit training

  • Depending on the exercises, there could be a high risk of injury
  • Generally not as effective as steady-state training and interval training are at developing cardiorespiratory fitness and aerobic and anaerobic metabolisms

Suitable exercises for circuit training

Exercises that are suitable for circuit training include:

  • Compound bodyweight exercises
  • Compound free-weight exercises, including kettlebell exercises
  • Compound machine exercises
  • Compound resistance band exercises
  • Compound medicine ball and stability ball exercises
  • Agility drills
  • Combat movements

Exercises that are ideal for circuit training are those that:

  • Can maintain your heart rate in the desired training zone
  • Are relatively safe
  • Are easy to transition between
  • Can easily be adapted to make them easier/more challenging
  • Can improve your functional strength and other aspects of fitness, such as speed, power, agility, coordination, and balance

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