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Interval Training: Optimizing Principle of Modern Cardio

By Alexander VanHouten, Master Trainer & Life Time Education Specialist

Have we become zombie hamsters on the cardio floor?

As I traverse the fitness floor’s grid of cardio equipment, I scan the sea of people moving intently but going nowhere and ask myself these kinds of silly questions.

In all seriousness, however, are we lifelessly trudging on the proverbial cardio wheel but truly getting (nearly) nowhere in relation to our goals?

Admittedly, I am guilty too. Endless droning on a StairMaster, treadmill, bike, precor AMT (nicknamed “the grasshopper” by a client of mine because of its yellow trim and bouncy movements) – all in pursuit of what?

For some it’s performance: “I want to run that 10K well. So, I get on the treadmill and run 5 miles a day.” For some it’s health: “My doctor said I needed to do 30min/day for my heart health. So, I get on the elliptical and go for 30 minutes.” For others it’s body composition: “I’m trying to get to my goal weight. So, I get on the StairMaster until I burn 500 calories.”

Is it possible there’s a better way? A more effective way? A more efficient way?

What if I told you that with just a bit more information and some engagement above the level of typical cardio wheel we could all be getting better results in less time? Let’s explore the most recent research and extract some principles for cardio in the modern training world.

What does science say?

There is a massive and nearly inarguable body of research that shows the majority of us doing steady state (a.k.a. zombie hamster) cardio are, indeed, benefitting from our exertion – but with possibly double the work for the same if not lesser results.

Let’s face it – unless you’re a true beginner or have been out of it for a while and cannot maintain 30 minutes at a moderate pace, you should really be doing interval training.

Whether it’s switching speeds or inclines on the treadmill, modulating pace on the StairMaster, rowing hard or jumping rope between weight training circuits, interval training is the practice of metered speeding up and slowing down in the session. Work for a time, recover for a time.

Except for a few specific purposes, the interval form of cardiovascular exercise greatly outweighs static training sessions in terms of time efficiency and even magnitude of results overall.[i] [ii]

For starters, interval training has been shown to improve cardiac output and performance (VO2 max) much more efficiently than static training. VO2 max is important because it correlates with several important markers of fitness, namely exercising (e.g. running, cycling, jumping rope) faster without fatigue as well as burning more fuel for greater changes in body composition. Even in sedentary individuals, interval training has been shown to be more effective at increasing lung capacity, cardiac stroke volume, and workload tolerance. [iii]

In a landmark study on untrained, non-smoking males, a 28-minute interval training program (4 minutes hard, 3 minutes easy, 4 repetitions) outperformed a protocol of continuous running at low intensity for 45 minutes.

After 8 weeks at a frequency of 3x/week, the low intensity group actually lowered their VO2 max (reducing their output and using less energy during their workouts over time), whereas the interval group increased their VO2 max over 15%.

Since this study in 2007, so many other studies have corroborated these results that cardiac rehab institutions have begun to incorporate interval training into their rehabilitation protocols. Patients have shown similar improvements compared to static protocols but with less time and in fewer sessions! [iv]

So VO2 max improvement is one thing, but what about body composition?

Well, there is calorie burn to consider. Interval training has been shown time and again to burn comparable calories to static cardio due to a phenomenon called Excessive Post-Exercise Oxygen Consumption (EPOC).

In laymen’s terms, interval training causes individuals to continue heightened caloric burn even after the workout is over – for up to 36 hours [v] whereas the increased caloric output of static cardio ends as soon as the workout is over.

More important for fat loss than the immediate caloric output of the exercise program, however, is the adaptation that it causes in the body.

That is, which form of cardio improves mitochondrial density? Or which form of cardio increases the number of energy-producing organelles that reside in an individual so that his/her metabolism is forever boosted and equipped to nuke fat molecules continually?

This question is way more important in the world of lasting fat loss.

Mitchondrial density increases just as significantly in individuals who train intervals as those who do chronic steady state cardio.[vi] In fact, one fascinating study showed that 6 rounds of 30s above threshold with 4.5 minutes of rest 3x/week for 6 weeks increased mitochondrial density higher than 60 minutes of steady state cardio 5 days/week![vii]

The math here is fascinating. A total of 90 minutes of interval training per week for 6 weeks increases your ability to use your fat stores just as much as training 300 minutes of steady state cardio.

Why would you do 3 times the work for the same results?

Nonetheless, all of this information, while gleaned from excellent research, could confuse the simplicity with which we should approach our cardiovascular exercise. Let me extract some key takeaways.

The Adaptation Principle – The magic happens when your body changes after your workout.

In our calorie-obsessed exercise craze, we have overlooked a fundamentally important idea….

If I do cardio only to burn calories and not to change my metabolism after the fact, then I shouldn’t be surprised if one year from now I’m still doing cardio to burn calories without seeing more extensive physical change.

Your cardio program, like any of the exercise you do, should create change in your body – not just burn calories.

In your program, instead of obsessing over how much fuel your session of cardio may have burned, fixate on how the session changed your metabolism for the better.

Did it cause you to burn more fat at rest and during your subsequent workouts this week? Did it increase your lung capacity and cardiac stroke volume so that your performance universally increases for resistance and cardio alike? Did it improve your ability to regulate the carbohydrates you eat so they don’t immediately turn into love-handle fodder when you digest them? Interval training is the cardio tool to create these changes.

If your cardio program isn’t changing you, scrap the short-sighted calorie counting and go back to the drawing board. In general, research suggests that at least 3 days/week of cardiovascular exercise (at varying intensities for 20-60 minutes each session) can significantly improve performance, health, body composition, blood chemistry and even insulin sensitivity.[viii] [ix]

For starters, I recommend a base building day, a moderate intensity day, and a high intensity day to cover all your bases. (To learn how to execute each of these types of cardio and learn relevant terminologies, check out our Cardio Burn Workout Workshop!)

The Dark Side of Interval Training – How much is too much?

Since interval training is scientifically superior in so many respects, should we scrap all of our old workouts and do intervals 30 minutes 5 days/week?

Though it’s a tempting proposition, moderation is key in interval training. Since such efforts require adequate rest and recovery, most studies that measured such positive adaptations only allowed participants to train at high intensities 3 days per week. And so should we.

If you’re going to incorporate this style of training into your workouts (and you should), opt for a maximum of 3 dedicated sessions of interval cardio weekly. You can also incorporate high intensity exercises such as med ball slams, burpees, and jumping jacks between sets during weight training.

Is Steady State Cardio Dead?

Don’t get too disillusioned with your former cardio routines, however. We shouldn’t abandon all semblance of rote exercise yet! Rest assured that steady state cardio still has its uses.

For beginners, steady state cardio is necessary to condition joints, ligaments, muscles and tendons. It also builds endurance for higher intensity work exerted over a meaningful and effective amount of time.

Starting with intervals may not only be confusing but may lead to injuries that would hinder further progress toward exercise goals.

Additionally, there are many people who have limitations that don’t allow their bodies to exercise at higher intensities. Low intensity, steady state cardio still elicits the positive adaptations of cardio and should be used accordingly by these individuals.

Other useful applications of steady state cardio in one’s program include active recovery from interval training sessions and race pacing for performance. Finally, there’s my personal favorite – mental “space out” time after a long day while mindlessly getting some movement clocked on your activity monitor.

The Future of Intervals

Eventually, I imagine there will be some chip that will chime in our ears to dictate exactly what our volume/duration/intensity should be based on our immediate lactate and stress levels and current state of recovery. (While there’s no chip yet, Life Time does have an app in conjunction with metabolic testing. That’s about as close as we can get right now).

Presently, however, we can take advantage of this optimizing cardio principle. Perhaps at our next workouts we can jump on the grass hopper (precor AMT if you want to be technical about it) or venture some other variety of interval work – and change our bodies to be smarter and faster than ever before.

Are you interested in adding interval work to your fitness routine? Talk with a fitness professional, who can offer his/her guidance on an interval protocol that’s appropriate for your fitness level and personal goals.

If you want to learn more about how we design our programs to support fitness and performance using our Core 3 Training™ methodologies

Download the Core 3 Training Manual.

Thanks for reading. If you learned something new, please share the post on your favorite social media channel.

[i] Helgerud, J., Høydal, K., Wang, E., Karlsen, T., Berg, P., et al. (2007). Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine and Science in Sports and Exercise, 39(4), 665-671

[ii] Wisløff, U., Ellingsen, Ø., and Kemi, O. J. (2009). High-intensity interval training to maximize cardiac benefits of exercise training? Exercise Sport Science Review, 37(3), 139-146.

[iii] Daussin, F.N., Zoll, J., Dufour, S.P., Ponsot, E., Lonsdorfer-Wolf, E. et al. (2008). Effect of interval versus continuous training on cardiorespiratory and mitochondrial functions; relationship to aerobic performance improvements in sedentary subjects, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 295, (R264-R272).

[iv] Bartels, M.N., Bourne, G.W., and Dwyer, J.H. (2010). High-intensity exercise for patients in cardiac rehabilitation after myocardial infarction. Physical Medicine and Rehabilitation. 2(2), 151-155.

[v] Wilson, et al. Concurrent Training: A Meta Analysis Examining Interference of Aerobic and Resistance Exercise. University of Tampa, FL. J Strength Conditioning.

[vi] Gibala, M. (2009). Molecular responses to high-intensity interval exercise. Applied Physiology, Nutrition, and Metabolism, 34(3), 428-432

[vii] Burgomaster, K.A., Howarth, K.R., Phillips, S.M., Rakobowchuk, M., Macdonald, M.J., McGee, S.L., and Gibala, M.J. (2008). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. Journal of Physiology, 586(1), 151-160.

[viii] Daussin, F.N., Zoll, J., Dufour, S.P., Ponsot, E., Lonsdorfer-Wolf, E. et al. (2008). Effect of interval versus continuous training on cardiorespiratory and mitochondrial functions; relationship to aerobic performance improvements in sedentary subjects, American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 295, (R264-R272).

[ix] Shepherd SO, Cocks M, Tipton KD, Ranasinghe AM, Barker TA, Burniston JG, Wagenmakers AJ & Shaw CS. (2013) Journal of Physiology, 591, 657-75.

The posts on this blog are not intended to suggest or recommend the diagnosis, treatment, cure, or prevention of any disease, nor to substitute for medical treatment, nor to be an alternative to medical advice. The use of the suggestions and recommendations on this blog post is at the choice and risk of the reader.
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