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Evidence Based HIIT Workouts for Women

Briana KellyFebruary 1, 2023

High Intensity Interval Training (HIIT) is all the craze for women, but what’s so special about it?

Over the past few years, HIIT has established itself as a staple in our workout routines. It’s for a good reason, as HIIT is a very effective way to burn calories in a short amount of time, making it the perfect go-to conditioning method for busy women!

Supporting our workouts with concrete facts is important to us, so take a read below to learn more about the science involved with HIIT and the rules we all need to follow to get the best bang for our buck!

If you’d rather just take a quick peek at our favourite exercises, see The Best 5 HIIT Exercises for Women.

What is HIIT?

High Intensity Interval Training is a method of exercise that combines high intensity bouts of movement with short rest periods. HIIT workouts are short; they can last anywhere from 10 to 45 minutes and can be done with or without weights. What makes them so effective is that they stimulate an afterburn: you continue to burn calories even after you’re done!

HIIT training can be done using just one exercise (ie. Work and rest on a spin bike), or using a circuit of several complementary movements (ie. Lunges, Planks, Hops).

According to the NSCA, the effects of HIIT are vast, and can be seen using physiological and performance markers.

Physiological benefits include improved:

  • Aerobic and anaerobic capacity
  • Heart muscle function
  • VO2 Max
  • Efficiency of muscle fuel availability

Performance benefits include:

  • Increased resistance to fatigue
  • Better time-trial performance

Many of these adaptations are equivalent to the changes seen with long, slow endurance work, but they’re achieved in a fraction of the time! No wonder HIIT is so desirable.

“The Golden Mean”

High intensity work stresses the body, and stress leads to adaptation; but, achieving a stressed state doesn’t always mean a high training effect will be achieved. Identifying the right amount of stress is key.

According to Pavel Tsatsouline’s Strong Endurance Manual, “The Golden Mean” describes a “medium” stress – one that is intense enough to warrant a response in the desired area, but not so much that it is costly to other body systems down to the cellular level.

“The Golden Mean” will be slightly different for every person, for different work sets, and for different exercises. It will take practice, trial and error, and consistency to discover! Our bodies are quite good at self-regulating, so make sure you are attuned to the signs. Find an intensity that is high, but is right for you.

The Rules of HIIT

In order to reap the best benefits of HIIT training, It’s important to note there are some rules that must be followed:

  1. Movement quality must not deteriorate
  2. Intensity during work periods must be high
  3. High intensity must be repeatable through subsequent rounds
  4. Respect the STOP signs

Let’s break down each of the rules and discuss the reasons why it’s so important for us ladies to follow them to achieve results.

1. Movement Quality Must not Deteriorate

Our first and foremost concern is ALWAYS movement quality. HIIT requires a baseline of strength and motor control that allows you to maintain proper form while working at a high intensity. 

Our ability to perform quality movement will deteriorate as fatigue sets in, so If the chosen exercise can’t be done well even with ample rest and concentration, don’t add it to your HIIT circuit! Instead, choose a variation that allows you to be successful. This might mean using a lighter weight, modifying the complexity (ie. eliminating any hopping or single leg variations), or changing the exercise entirely! For some ideas, check out the progressions and regressions here: The Best 5 HIIT Exercises for Women.

2. Intensity Must be High

The High Intensity part of HIIT is key. Female bodies won’t reap the benefits of HIIT if the intensity isn’t consistently high during the work periods. This means exercises must be selected appropriately; if an exercise is too challenging, the intensity will taper off with fatigue and impact your outcome. You must find “The Golden Mean”. 

Ultimately, we want to teach our cells (in the muscles, heart, and lungs) to get comfortable working at a high intensity so the next time they can work harder or for longer while minimizing the effects of fatigue.

3. High Intensity Must be Repeatable

The intensity must not fall as subsequent rounds of each exercise are performed. Intensity – or power output – is objective, and can be measured using metrics like the number of reps performed in 40 seconds, or the RPM’s on a bike. The trick is finding a power output that allows you to work at a high intensity, but not so high that you can’t repeat the same work during the next interval (again, “The Golden Mean”!). We expect to see fatigue, but the fatigue should never be so severe that it impacts your ability to perform.

Our bodies rely on several systems to produce energy, and each of these systems produces waste byproducts. When we push towards peak intensity, we encounter our Anaerobic Threshold (or Lactate Threshold), the point where waste production begins to increase exponentially. Working beyond this point is not sustainable; in fact, spending prolonged periods in this state is costly to cellular health. As Pavel says, we must “flirt with the threshold”, not exceed it, in order to preserve our ability to repeat high intensity bouts of exercise.

4. Respect the STOP Signs

Absolute burn-out is not the goal of HIIT. A well-designed HIIT program should leave you feeling ready to take on the world! Respecting the stop signs will allow you to make noticeable progress while keeping your body safe and healthy.

The most important sign: Stop when you can no longer follow rules 1-3!

Other stop signs:

  • Physical: shaking, grip fatigue, sharpness of breath
  • Recovery: inability to recover within rest interval

The day after training, muscle fatigue and DOMS (delayed onset muscle soreness) are normal, but the fatigue should never be so severe that it can’t be alleviated by a good warmup. The same goes for general energy levels. By the end of a session you should feel you worked, but once you’ve cooled down and caught your breath, you should feel energized and refreshed!

HIIT for Everyone

As coaches, we love prescribing interval based workouts on top of our regular strength programs. Our clients love the feeling of pushing themselves into higher zones and we love the movement variability you can add to a workout. HIIT can be applied to all levels of fitness, from the complete beginner to advanced gym rat! It can be done at the start of a program to prioritize power, or as a metabolic “finisher” at the end.

The evidence is in your favour – have fun with HIIT! Just remember: find your “Golden Mean”, stick to the rules, and know when to stop. Now, you’re off to the races!


NSCA Essentials of Strength and Conditioning (2008); Baechle and Earle 3rd Edition.

Tsatsouline, Pavel (2019). Strong Endurance.

Briana, Jess, and Andrea flexing with kettlebells