#WTFWEDNESDAY: High Intensity Inteveral Training (HIIT)

For this week's installment of #WTFWednesday, I'm discussing High Intensity Interval Training - otherwise affectionately (or not...) know as HIIT.

It's January and that generally means the gym will receive an influx of new members and extra visits, as people commit (or recommit) to their resolutions + goals. And since HIIT is popularly known as an efficient, effective form of exercise (which it is!), it's likely that people might gravitate toward the method.

Unfortunately, HIIT can also get a bad rap for being unsafe or causing injuries (which it also can!); this generally is due to the fact that individuals might try to HIIT it (pun intended) too hard too fast. Just like any other exercise modality, HIIT training should be worked up to, incorporated intelligently, and be paired with appropriate warm-ups and cool-downs.

Check out this short (12 minute) video below for all things HIIT-related, including it's potential benefits, different types, and how to approach it. I've also included a written summary of the key points.

I'd love to know - do you incorporate HIIT into your exercise programming? If so, what are your favorite methods or exercises? I must say, I love me some burpees :)


  • Fitness industry education + certification body ACE defines HIIT as: "a system of organizing cardiorespiratory training which calls for repeated bouts of short duration, high-intensity exercise intervals intermingled with periods of lower intensity intervals of active recovery"

  • Known for being efficient (great if you're time-crunched) + effective (increase in strength + power, metabolism-boosting capabilities)

  • Often associated with high impact movements (running, jumping, slamming, CrossFit) - although it doesn't have to be

  • Sometimes thought as unsafe (as people get injured when going too hard too quickly)

  • All of these things CAN be true, to a degree:

  • If done properly, HIIT an certainly be time-efficient. As little as 5-10 minutes can have positive health benefits, with longer sessions lasting 20-45 minutes. However, it’s important (as with other workouts) to warm-up + cool-down properly.

  • Probably the most buzzed about part of HIIT training is the elusive after burn or EPOC (Exercise Post-Oxygen Consumption) - aka the fact you burn calories well after your workout (often cited as 24-48 hours). More recent research shows that when done properly, yes HIIT can elicit the after burn effect, but that it is likely more effective for men (who can burn extra calories for 24 hours… but women more like for 3 hours <womp womp>).

  • FYI, because you are hypothetically working out in an oxygen-starved state (anaerobic) you are burning less calories/fat during the workout than during aerobic activity (where you burn fat) → idea behind fasted cardio. But, because of the after burn, you can burn more calories overall - which is relevant if you believe the calories in/out theory


  • Potential "after burn" effect: elevated metabolism and associated calorie burn immediately after and up to ~48 hours post-session

  • Improve resting heart rate, blood pressure + blood sugar --> with which most other forms of exercises are also associated

  • Improve aerobic capacity + cardiovascular efficiency --> interesting as it's technically "anaerobic" (without oxygen)

  • Building muscle: This is where HIIT may really shine; while traditionally resistance or strength training is associated with increased muscle density (and traditional cardiovascular or aerobic training is not), HIIT may give you the best of both worlds (increased aerobic capacity as well as muscle building, or at least maintenance)

  • Research shows that adding resistance can increase efficacy (e.g. dumbbells)


  • Tabata: 20 seconds work/10 seconds rest/8 rounds/4 minutes total

  • Great to tack on to the beginning of a workout session or as a "finisher"

  • Fartlek: less structured, can be for time, reps, distance...

  • Be sure to structure work:rest ratio appropriately

  • The longer and/or more intense the work set, the longer the rest set

  • Key components: time, intensity, recovery


  • While it's very effective + efficient, HIIT (like all forms of intense exercise) are perceived by the body as STRESS. If you are already under stress (physical or otherwise), if you add on more stress, it's likely you will see diminishing returns.

  • Account for enough rest within the HIIT session but also over the course of your week. e.g. only 2-3 HIIT sessions per week on non-consecutive days, including less intense work like walking, yoga, Pilates

  • HIIT is intense by definition; if you are brand-new to working out, or coming back after a hiatus, ease into it. (In other words, don't go from couch potato to 30-day Insanity Challenge participant.)

  • If you are pregnant, have an acute injury or other physical limitation, or have some other special condition, HIIT might not be for you. Always check with your healthcare provider before starting a new fitness program, and consider seeking the guidance of a qualified fitness professional.

Note: The information contained in this blog post, on the website www.lizbarnet.com, and via social media is intended to educate + inspire you. None of the information provided is intended to be a direct recommendation; if you apply any of the information presented, you do so at your own risk. Seek out the guidance of a qualified healthcare or fitness professional before starting a new fitness, nutrition, or health/wellness-related program.

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