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How-To Fitness: Interval Workouts and Recovery 

You’ve likely heard (or experienced) the impressive benefits of interval workouts. For the short time investment, interval training offers major bang for your buck in terms of fat burning, body composition change, cardiovascular conditioning, and insulin sensitivity. But workouts this demanding require special attention to design and recovery. Let’s take apart the interval model and some key recommendations for including it in your fitness program.

What is an interval workout?

Interval training alternates bursts of high exertion (a.k.a. “high intensity”) effort with periods of very low exertion movement (i.e. “rest”). The objective is exhaustion, which means you'll push yourself to your maximum. Interval workouts differ from regular aerobic exercise because these brief intervals of massive exertion take you to the anaerobic level. (Some interval programs are specifically designed to stay in the aerobic zone but will differ in the resulting benefits.)

Interval activities themselves can include a variety of sprint drills, cycling bursts, stair runs, and explosive power workouts just to name a few. Depending on the particular routine, rounds of exertion are often 20-30 seconds but can vary from 10 seconds for beginners to a few minutes for serious competitive athletes.

The opposing periods of “rest” in interval work can vary considerably depending upon the particular protocol as well as the person’s fitness level and individual goals. Common interval routines like “30-second” sprints suggest a 30-second exertion time and rest periods of 3-4 minutes in each interval. Intervals are repeated anywhere from 4-8 times commonly. The shorter the rest time, the fewer intervals are recommended per session, particularly for those beginning interval training. Recovery time in between interval workouts should generally be 3-4 days for most people.

Why does recovery matter so much for intervals?

As Tom has mentioned in his “Mastering the Art of Stress and Recovery” series (I, II). it’s important to remember that all exercise is a stress to the body. Regardless of the type of stress the body senses (e.g. mental, emotional, physical, etc.), it will respond by releasing one of three stress hormones, including the catecholamines (epinephrine and norepinephrine) and cortisol. Given the very demanding nature of interval training, the exertion imposes a high (albeit brief) stress load on the body. The higher the stress load, the higher the secretion of stress hormones.

For example, people can have chronically high levels of cortisol due to excessive amounts of stress or inadequate physical and hormonal recovery from it. To the point here, cortisol and the anabolic hormone testosterone typically have an inverse relationship: as one goes up, the other typically goes down. This is an important point to understand because testosterone is a vital hormone that helps the body repair from exercise stress. When we overdo exercise (or any kind of stress), we hormonally compromise our body’s ability to handle the stress and make necessary repairs.

In addition to the recovery between interval workouts are the rest periods within the interval session itself. Rest periods are the total amount of time spent between intervals (or sets/reps). If you don’t allow the muscles and nervous system to recuperate fully between intervals during maximal or high intensity interval training, you risk injury! 

Finally, keep in mind that interval training, while incredibly beneficial and efficient, is also extremely taxing and not for everyone. Those just getting back into shape should work on building a solid level of aerobic fitness before taking on interval exercise. When you’re ready, talk to your doctor, and work with a trainer to establish an appropriate interval program for your needs and goals.

Questions? Thoughts? Offer up your comments on interval training or the importance of workout recovery. Be Strong and Live Long!

Written by Jason Stella, National Brand Developer-Fitness and Certified Personal Trainer

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.

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