Strength Training vs. HIIT

By Jessica Tranchina, PT, DPT – July 1, 2021

For the past 20 years, HIIT training (high intensity interval training) has taken over as one of the most popular ways to train in the fitness industry. It is fast, tough and trendy, all at the same time. It’s basically a go-to for workouts and, in some cases, the only way many of us train. Strength training, on the other hand, got a little lost in the shuffle, and we were led to believe that as long as we lifted a few weights in a HIIT class, it was sufficient. Because many of us crave the feeling of utter exhaustion that usually comes from a good HIIT workout, many believe the more we feel that way, the better the workout … but is that the case? 

Not to put a COVID-19 spin on everything, but if the pandemic has taught us one thing, it is that it’s OK to slow down. It’s more than OK — actually, it’s necessary. 

The sudden halt to our everyday lives back in March of 2020 showed us all that we just do too much. Pre-COVID, the “hustle culture” was alive and well. People scoffed at downtime and we were made to feel guilty about resting. I don’t know about you but, as of late, people in my circles have been encouraging others to slow down.

It feels like slowness is encouraged in all aspects these days, including exercise. I’ve taken this cue and applied it to my workouts. Instead of my usual high-intensity workouts, I’ve been enjoying slower, more intentional workouts. I began to embrace strength training.

If you are reading this and thinking, “No way am I giving up my HIIT workouts,” that’s fine and dandy, but HIIT can also keep cortisol levels high if you don’t recover from your workouts properly and give yourself enough time to rest between HIIT sessions — not a beneficial scenario for those of us who are already chronically stressed. 

Strength training is one of the best ways to permanently change your body composition, increase your overall strength, and improve your bone and joint strength. Simply, it’s a type of exercise focusing on the use of resistance to build strength and lean muscle mass. Having more muscle mass can improve your basal metabolic rate so you’re burning more calories at rest, which in turn leads to greater weight loss.

High-intensity interval training can be extremely difficult because it takes a lot out of you. Additionally, this form of exercise may also not be sustainable long-term due to difficulty maintaining the high levels of intensity and interest in each workout. In one study, a small portion of the participants opted out of the program because of disinterest and an overall “lower level of enjoyment” in the Tabata group versus in the other groups.

What are some of the lesser-known facts about strength training?

  1. Strength training helps prevent chronic diseases like heart disease and Type 2 diabetes.
  2. Strength training has been shown to decrease body fat significantly!
  3. These two studies that followed subjects paired into three different groups showed that the group incorporating diet with strength training lost 21.1 pounds of fat in a 12-week period. This was comparing a diet group, a diet with cardio group and a diet with strength training group. The strength training group yielded the best results, being 35% higher than the cardio subjects and 44% higher than the diet-only group.
  4. Another study showed that strength training even causes an afterburn effect for up to two hours after the workout.

HIIT became popular when a study came out by Dr. Izumi Tabata conducted in 1996. Dr. Tabata conducted the study with elite athletes — half of them pedaled on an ergometer at a moderate intensity (measured as 70% of their VO2 max, a measure of the maximum amount of oxygen your body can use during intense exercise) for 60 minutes. The other half cycled for 20 seconds at an extremely high intensity (170% VO2 max) followed by 10 seconds of rest, for seven or eight rounds, so up to four minutes in total. They also cycled for 30 minutes at 70% VO2 max one day a week. Both groups trained like this five days a week for six weeks, and by the end of the study, the high-intensity group was found to have burned more calories.

The trouble is, however, that the average person can’t even reach 170% VO2 max, so the results of the study cannot be extrapolated to the general public. Most people cannot reach the intensity required to get the benefits from true HIIT. Reaching even 100% of your VO2 max is complete exhaustion. This would be at the point when people can no longer continue. They’re often throwing up and it’s a very hard thing to achieve. While it’s theoretically possible, there aren’t many people who can reach the required intensity. Most people do not have the anaerobic or aerobic capacity to be able to sustain a high heart rate long enough to actually sustain the high intensity. What’s being called “HIIT” is often a long-winded cardio class, which is fine, but it’s not actually HIIT.

If your HIIT class is 45 minutes long, you may not be engaging in real HIIT because, if you were, you physically wouldn’t be able to do more than three to four minutes. As duration increases, intensity drops. Therefore, you may very well be doing intervals, but they’re probably not as high intensity as you think. 

If you enjoy HIIT, the occasional class is fine, but doing too much can be harmful, especially since many people are far more stressed than they even realize! Adding HIIT as their primary (or only!) exercise option to the mix has the potential to be a disaster.

It could lead to an increased risk of injury, excess cortisol production, burnout, excess fatigue and so on.

That’s not to say that everyone will experience these things as bio-individuality needs to be considered, but it could be a matter of time for any given individual to experience the adverse effects of a high-intensity-only protocol. If you haven’t given a strength-based program a try, you definitely should. Your adrenal glands will thank you! 

Ultimately, the best routine is the one you know you’re going to follow through with, so tie up those laces and get moving!

About the Author

Jessica Tranchina, PT, DPT, is a co-founder of Generator Athlete Lab and has been an athlete her whole life. As the creator of the Generator Method, Tranchina works to help guide others to better performance and recovery and is passionate about bringing the active community of Austin together from all fitness levels and athletic backgrounds. She is the owner of PRIMO Performance and Rehabilitation, which started in Austin in 2010, where her expertise and unique skill set have been established as one of the best in her field. NASM-CPT, A.R.T Certified Provider, CKTP.


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