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Interval Training: An Investment That Pays Off

Written by: Tom Nikkola – Director of Nutrition & Weight Management

When we spend our money, we like to talk about value — getting a lot of benefit from something without investing a lot of money. You dedicate a certain amount of your time every week to exercising and you may be able to get more value for the time you invest. Interval training may be the way you achieve the same benefit you’re getting today with less time invested — or gain even more benefit in the same amount of time.

What is interval training?

Interval training is a method of exercising by varying your level of intensity, using short bursts of exercise at high intensities, interspersed with brief periods of recovery. This type of training protocol allows an individual to perform a significant amount of intense work and gain cardiovascular benefits in a fraction of the time it takes to gain benefits from steady-state, lower intensity exercise.

A recent study on youth compared seven weeks of sprint intervals three times a week against another group who performed 20 minutes of steady-state exercise three times per week for seven weeks. Both groups saw improvements in fitness levels and cardiovascular disease risk factors. The primary difference between the two groups: The steady-state group exercised a total of 420 minutes over seven weeks while the sprint group exercised a total of 63 minutes during the same time!

Another way interval training has been studied is by comparing a group who performs low-intensity, steady-state workouts against another group performing high-intensity training, and ensuring the two groups achieve the same calorie expenditure. The steady-state group exercises longer to achieve the same calorie expenditure. If our bodies managed calories by the often-quoted calorie balance equation, the effect from exercise on body composition would be the same. That’s not the case. When keeping calorie expenditure the same, those performing interval training lose more body weight, body fat and belly fat. In addition, insulin sensitivity is often more improved.[i],[ii] The hormonal effect of interval training likely supports these physical changes. 

Even if you have a chosen sport which relies on great endurance, or are training for an endurance event, interval training can easily be included in a training program and can be a great way to avoid letting your training program become stale. Aside from the physical benefits, high-intensity interval training also appears to be more enjoyable for participants.[iii] For those who are not avid endurance participants, it makes sense that shorter, more focused workouts could be more appealing.

Drawbacks of interval training

As good as the benefits of interval training sound, there are some drawbacks. First, interval training requires a different level of commitment to the workout routine. Though sessions are typically shorter than steady-state exercise sessions, they require more focus and motivation to achieve appropriate intensity levels.

In addition, high-intensity exercise increases the secretion of cortisol, the body’s main stress hormone.[iv] Many people are faced with significant levels of stress already. It may not be appropriate to take on this type of exercise routine if your cortisol levels are already out of range. You can have your cortisol levels checked with a simple saliva test. Just talk with a fitness professional at your local Life Time. If you do have high levels of stress, low-intensity, exercise can be very beneficial. Steady-state workouts have been shown to actually help lower cortisol levels. To avoid excessive stress, intense interval training should not be performed more than a couple times per week (for most people).

Incorporating interval training

Interval training can be incorporated into a walking program by varying the grade, such as changing the incline on a treadmill or walking on rolling hills. It can be done on a bike outside or indoors, just by changing gears. Many group fitness classes are designed around the concept of intervals. A fitness professional can help design an appropriate plan based on your goals, current level of conditioning, your workout schedule and your lifestyle.

Once you’re ready to try intervals, there are several different ways to incorporate them into your program. The following are just a couple ideas to get you started.

  • Strength intervals: If you’re on a treadmill, maintain your speed and crank up the incline for a minute. Whether you’re walking or running, it’s sure to speed up your heart rate. Don’t slow down on the speed. Going outdoors? Find a good hill. Start by simply walking up and down it. You can progress to jogging, running and sprinting as you get into better shape. If you’re on a bike, use more resistance or shift up to put more pressure on your legs while you keep your pedaling speed the same.
  • Speed intervals: Speed intervals are a bit more technical than strength intervals. You’ll be modifying the speed to get your heart rate up to a level you want to achieve, usually with the aid of a heart rate monitor and a fitness specialist’s guidance (at least to start). More speed means more momentum on your joints and greater potential for injury. If you have any joint issues or haven’t spent much time running, don’t start with sprints. Speed intervals should be incorporated after your conditioning improves.

Interval training is not for everyone but if you’re interested and committed, it can be beneficial, time-saving and possibly more enjoyable. As you get into better shape, you’ll be able to push yourself further with “all-out” intensity.  However, if you’re just getting started, take it a step at a time. Add a short jog every few minutes into your walk. Eventually, you’ll be running and then sprinting. Be smart about your training. You’ll get no benefit from sitting on the couch, nursing an injury because you did too much, too fast. In a future article, we’ll look at how you can optimize your interval program through heart rate training and the use of a heart rate monitor. Happy training.

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

Share thoughts and post questions below.


[i] Irving BA, Davis CK, Brock DW, et al. Effect of exercise training intensity on abdominal visceral fat and body composition. Med Sci Sports Exerc. 2008;40(11):1863-1872

[ii] Tjonna AE, Lee SJ, Rognmo O, et al. Aerobic Interval Training Versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome. Circulation. 2008;118:346-354

[iii] Bartlett JD, Close GL, MacLaren DP, Gregson W, Drust B, Morton JP. High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: implications for exercise adherence. J Sports Sci. 2011;29(6):547-553

[iv] Hill EE, Zack E. Battaglini C, Viru M, Viru A, Hackney AC. Exercise and circulating cortisol levels: The intensity threshold effect. J Endocrinol Invest. 2008;31:587-591

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Reader Comments (4)

I recently started taking the Total Conditioning class at LT and after only a two weeks I can already notice and feel a huge difference. I feel stronger and my endurance is building more and more with every class. Another huge benefit is they change the routine every month, so your body is constantly be exercised in different ways.

May 29, 2011 | Unregistered CommenterHeather Quinn

Total Conditioning, taught by a gal named Shanna, at our LT here in Colorado Springs is a complete maniac! It is, BY FAR, the toughest and most challenging class I have ever taken (and I have now tried every single class at LT.) I am currently training for the Chicago Marathon in Oct. and some fellow runners advised me to incorporate more strength training in my trng routine so I have spent the last 3 weeks exploring all the strength trng classes offered at LT. Total Conditioning is an intense strength AND cardio workout. I would highly recommend it if you're seeking those "interval" workouts the author wrote about. I will continue to attend every week because it pushes me, motivates me, and inspires me to go beyond my comfort levels. And, Shanna is an awesome coach, the perfect instructor for this type of class!

May 30, 2011 | Unregistered CommenterWendy

What are you saying?
Steady State Training from above: 420 minutes = 7 weeks x 3 times per week x 20 minutes per time
Interval Training from above: 63 minutes = 7 weeks x 3 times per week x 3 MINUTES PER TIME!????
Am I to deduct that Interval training 3 minutes per day, 3 days a week for 7 weeks compares to
20 minutes of Steady State training 3 days a week for 7 weeks?
Something doesn't add up.

May 31, 2011 | Unregistered Commentermerak7

Sorry for the confusion. The stead state group exercised for a TOTAL of 420 minutes over the course of seven weeks, or sixty minutes per week (20 minutes per day, three days per week). The interval group exercised for a TOTAL of 63 minutes over the course of seven weeks, or 9 minutes per week (3 minutes per day, three days per week). That's not to say people should only exercise 3 minutes per day three days per week, but shows how exercising correctly allows individuals to get more accomplished with less time spent exercising. Hope that makes sense.

May 31, 2011 | Unregistered CommenterTom Nikkola

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