High Intensity Interval Training: All You Need To Know!

What Is High Intensity Interval Training?

High intensity interval training is a cardiovascular workout consisting of short intense bursts. Lasting anywhere between 15 and 90 seconds, training is accompanied by brief in-between rest periods.

Recently, HIIT workouts became a popular alternative to the decried and derided steady state cardio marathons you subject yourself to after a weekend binge. To the contrary, HIIT workouts take up less time and deliver the same, if not better, results.

But brevity isn’t HIIT’s only benefit! For most, it’s the promise of the holy grail, concurrent fat loss, and muscle gain. Trying to convince you of its benefits, HIIT evangelists are quick to compare a marathon runner and a sprinter. They contrast a marathon runner’s long runs and low muscle mass to the sprinter’s bursts and toned physique.

So now you have the gist of it, you know that HIIT workouts are an alternative to conventional cardio. You know they consist of short bursts with in-between rests and may lead to muscle gains.

But to fully understand how high-intensity interval training can be a catalyst for change, we’ll examine the scientific evidence and my own experience.

HIIT versus Steady State Cardio

Cardiovascular exercise is beneficial for plenty of reasons, but most partake to either lean out or maintain their body fat level. Prolonged cardio sessions are, and have for a long time, been an accepted way of achieving those goals.

Unfortunately, most people run into the same problems with this conventional form of exercise. Namely; the marathon sessions become the bane of their gym experience, their metabolism adjusts, they hit a plateau, and they begin looking for a more efficient exercise.

As people begin looking for alternatives to their cardio woes, most come across some form of HIIT. Its appeal is a no-brainer, it’s a more effective way to lose fat in less time. Backed by enthusiasts and research, HIIT’s greater effectiveness is well documented.

Research Backed

Research1 published in Applied Physiology, Nutrition, and Metabolism Magazine demonstrated that “repeated high-intensity exercise sessions are a powerful method to increase whole-body and skeletal muscle capacities to oxidize fat and carbohydrates.”

A 2008 study2 by McMaster University found that “HIIT induces numerous metabolic adaptations usually associated with traditional endurance training,” and that “a total of only approximately 15 minutes of very intense exercise can increase skeletal muscle oxidative capacity and endurance performance and alter metabolic control during aerobic-based exercise.”

The research mirrored what the fitness community already knew; high intensity interval training a worthy alternative and an effective method in your quest to achieve a leaner and fitter body.

To better understand the studies, here’s an example. If you do steady state cardio for 30 minutes, you may burn 200 calories, 180 of which are pure fat. In the same time span, HIIT will burn 800 calories, 480 of which are fat.

As evidenced above, the former burns a higher perfentage of fat. However, HIIT burns a higher overall number because it increases your cell and muscle oxidal capacity.

Excess Post-Exercise Oxygen Consumption

But that’s not HIIT’s greatest strength, that distinction goes to excess post-exercise oxygen consumption, Popularly known as EPOC, the increased rate of oxygen intake occurs following strenuous activity.

EPOC prompts greater fat metabolization throughout the day and gives your body a greater capacity to lose fat. Conversely, post steady state cardio EPOC prompts fat metabolization to a lesser degree since the exercise is significantly less stimulating.

The abundance of positive evidence and favorable accounts from HIIT devotees may have you reaching for the HIIT Kool-Aid, but there is a drawback to consider.

Too much HIIT and your metabolism may adjust to the afterburn. Consequently, over time your body will spare less calories during EPOC periods. So don’t dive into a full time HIIT regimen, ease into it instead.

In It For The Gains Though!

Striving for a lean physique is a noble and worthy pursuit. Anything that requires dedication and leads to a healthier lifestyle is a worthwhile challenge. But some don’t stop there, they strive for muscle mass to boot.

If you’ve ever tried to attain them simultaneously, you’ve practiced concurrence training. The regiment compounds a cardio routine for fat loss and resistance training for muscle gain. The former consists of hours spent walking on an incline.


Unfortunately, ample research shows that effort may have a perverse effect. Namely, a University of Alberta study3 concluded that there is “support for the contention that combined strength and endurance training can suppress and augment some aspects of capillarization in skeletal muscle.”

Specifically, steady state cardio doesn’t lead to the hoped-for “concurrent” effect. Instead, it blunts, and in some cases causes muscle loss when combined with resistance training.

Further evidence came from a Penn State University study4, which suggested that “the combination of strength and endurance training results in an attenuation of the performance improvements and physiological adaptations typical of single-mode training.”

So if you’re trying to lose fat while placing yourself on the fast track to hypertrophy, those prolonged cardio sessions may not be a viable option.

High Intensity Gains

Instead, the research has increasingly pointed to, you guessed it, low volume and high intensity interval training. In fact, a recent Journal of Physiology published study

In fact, a recent Journal of Physiology published study5 found ”increased resting muscle glycogen GLUT4 protein content” in test subjects and concluded that HIIT is a “potent stimulus for increasing muscle mitochondrial capacity and improving exercise performance.”

But there’s plenty of evidence beyond the science. HIIT’s efficacy makes sense when comparing it to resistance training. If we use a high intensity interval training session on the stationary bike as our example, muscle gain isn’t surprising.

HIIT cycling consists of hip flection, a movement similar to a leg press or a squat. It’s also done repeatedly for brief periods in a single session, mimicking multiple reps in a weight lifting set. FInally, HIIT “sprints” consist of short overlapping bursts of intense exercise and are therefore anabolic.

There’s more research, a study6 published by the Journal of Strength and Conditioning Research concluded that high intensity interval training resulted in “significant improvements in V̇o2max, O2 pulse, and power output.” A 2013 study

A 2013 study7 in the Journal of Applied Physiology, Nutrition, and Metabolism found that “as little as three HIIT sessions per week, involving less than 10 minutes of intense exercise within a time commitment of less than 30 minutes per session, including warm-up, recovery between intervals and cool down, has been shown to improve aerobic capacity, skeletal muscle oxidative capacity, exercise tolerance and markers of disease risk after only a few weeks in both healthy individuals and people with cardiometabolic disorders.”

Personal Experience

I’ve practiced some form of cardiovascular exercise for years. When I was younger, I ran three miles a day. After I signed up for a gym, I began walking on an incline on the treadmill.

Eventually, I graduated to extended sessions on the stationary bike. Primarily, I saw cardio as a way to keep my body fat low, while trying to gain muscle.

I also viewed cardio as a way to combat the occasional binge, it was a tool I’d employ to balance out an excessive weekend.

But as I learned more about nutrition, fitness, and discipline, I began to understand that you can’t out train a bad diet and that cardio was enabling the regretful binges.

So I shifted my perspective and began keeping better dietary habits, loosened my self-imposed restrictions, and tried different exercise routines.

Eventually, the years of conventional cardio started to take a toll on my left knee. After going on a regimen of one-hour stationary bike sessions, for over five times a week, my knee called it quits.

Shifting Over to HIIT

I stumbled across HIIT as soon as I began looking for alternatives. So after doing my research and giving my knee a break, I got to it, aiming for three to four sessions a week.

Initially, I was skeptical, how can 15 minutes of cardio with brief spikes of intensity do the job of an hour marathon? The research alleviated any doubts, but the results reassured me.

I measured my progress through a DXA scan, which is one of the most accurate body fat measurements available outside of a hydrostatic tank.

I kept all other aspects of my diet and fitness the same so I could get an accurate reflection. Initially nervous, I was pleasantly surprised at my results. The DXA showed that my body fat fell by 1% and my lean muscle mass increased.

The muscle gain happened mostly in the quads, which wasn’t surprising since mine would swell after every HIIT session.

The gains make sense since HIIT and resistance training are both performed in the same manner. Both are done in sets with multiple repetitions.

I was obviously happy with those numbers, but I would’ve been just as happy if they stayed the same. After all, I set out for an exercise that would deliver consistent results, but I found one that performed even better, for my joints and my time.

Ultimately, I’d recommend HIIT workouts as an alternative cardio form to anyone looking for a better exercise. Science and personal experience aside, most people find conventional cardio monotonous and boring. As a result, they end up dreading their time at the gym.

HIIT workouts are a swift, refreshing, and most of all, challenging remedy. The required pace and intensity are a breath of fresh air that stays with you throughout your day.

1 Comment

  1. Great article. It would seem to me that HIIT results for fat loss would best be achieved in a fasted state. What’s your oppinion on that?

Leave a Reply

Your email address will not be published. Required fields are marked *