It should be fairly intuitive that all forms of exercise are beneficial in some capacity. It’s also patently clear that the rise of desk-based jobs and digital technology is contributing to the proliferation of sedentary lifestyles among the population.
Consequently, health complications like obesity and cardiovascular disease are killing more and more humans every day that passes. While diet is certainly a crucial factor in health and longevity, leading a sedentary lifestyle is unequivocally harmful to our well-being.
As time evolves and we grow accustomed to sitting behind a computer all day, we start to scrutinize every step we take. This has very much spawned the trend of smartwatches and fitness trackers that more or less just count your steps throughout the day.
After all, movement is movement – it’s all the same, right? Well, not exactly…
Walking the recommended 10,000 steps (or more) per day is great and all, but many people don’t realize that low-intensity exercise and leisurely physical activities do not impart the same benefits as high-intensity exercise.
Read on to learn why you shouldn’t shy away from intense exercise, even if it means you have to push yourself out of your comfort zone. As the adage goes: Pain is temporary, pride is forever.
Low-Intensity Exercise Vs. High-Intensity Exercise: Which is More Beneficial?
Movement is often thought of as a means of burning calories (energy), which is partially correct. Even when you wake up and brush your teeth, your body uses biochemical energy to fuel those seemingly mundane activities.
Hence, walking a few miles is healthy if all you normally do is sit at a desk for eight hours a day and then go home to veg out on the couch and watch Netflix. There’s plenty of research showing that walking a certain amount of steps every day is more beneficial than remaining sedentary.
For example, one study found that walking 10,000 steps (roughly 5 miles) or more per day may enhance longevity.1 Though, that’s not a particularly profound discovery if you think about it; walking helps you burn more calories than sitting.
However, putting yourself through a dedicated, intense workout is where the real “magic” of exercise happens. By magic we mean deep-seated physiological adaptations that only high-intensity exercise imparts.
Performing even a few brief all-out intervals effectively increases your resting metabolic rate – the amount of calories you burn while laying down.
This may simply consists of sprinting 100 meters 4-5 times in a short timespan and the increase in resting metabolic rate will persist for upwards of 24-36 hours.2 This is colloquially referred to as the “afterburn effect” of high-intensity exercise.
On the contrary, walking 1000 meters, or even 5000 meters, does not increase your resting metabolic rate (RMR); In fact, low-intensity exercise reduces your RMR over time.3
This is where the deception of calories burned during exercise can throw people off. Many people will go to the gym and walk on the treadmill for a few miles until the machine tells them they burned 300 calories.
Meanwhile, someone else might come along on the treadmill next to one of the people and do a few sprint intervals. Once the sprint intervals are completed, the machine might say they only burned 150 calories .
Naturally, the person walking on the treadmill is going to think their workout is better/healthier/more beneficial. After all, burning 300 calories will result in greater fat loss than burning 150 calories, right?
In reality, that’s not exactly how exercise and weight loss work.
High-intensity exercise, specifically high-intensity interval training (HIIT), may result in less calories being burned during exercise, but the “afterburn effect” will help you burn more calories over the course of time than long bouts of low-intensity exercise.
Thus, HIIT helps you burn more calories in significantly less time than low-intensity exercise, while also enhancing your capacity to absorb and utilize nutrients for energetic purposes as opposed to storing them as body fat.4
What is HIIT? High-intensity Interval Training Explained
Don’t let the word “intense” scare you when it comes to HIIT. We aren’t saying you have to turn into the ultimate meathead and put yourself through grueling bodybuilder-style workouts seven days a week or train like Usain Bolt.
Rather, you just need to put some diligent effort into your exercise regimen and push yourself to a greater degree than leisurely walking or riding your bike a couple miles (which generally isn’t very strenuous).
HIIT entails pushing yourself for a brief interval of time until exhaustion kicks in (e.g. sprinting as fast as you can for 15-20 seconds), then “actively recovering” for a short time before completing another all-out interval, and repeating the process for several cycles.
This forces your body to rely on anaerobic metabolism as you reach your lactic acid threshold (i.e. when the “burning” sensation in your muscles prevents you from performing at max capacity). In turn, HIIT turn exhausts several energy systems in your body and results in a variety of beneficial adaptations at the cellular level, notably mitochondrial biogenesis (we will touch more on this soon).
On the other hand, low-intensity exercise is predominantly dependent on aerobic metabolism, which is why you can walk or jog for a longer duration of time than you can sprint.
Is Walking Beneficial?
Make no mistake that low-intensity exercise, such as walking, is better than not moving/exercising at all. Going for a stroll after a long day at the office is undoubtedly beneficial, especially if you have physical limitations or handicaps that prevent you from being able to exercise intensely.
Nevertheless, the longevity benefits of intense exercise far outweigh those of low-intensity exercise (both anecdotally and in research).
The Many Benefits of Intense Exercise
Let’s take a look at some of the most compelling studies that substantiate the benefits of HIIT.
HIIT Increases Mitochondrial Biogenesis (and Metabolic Rate)
Mitochondria are cellular organelles that serve as the “power plants” of cells since they are where the electron transport chain takes place. Mitochondria are key regulators of metabolic rate as they contain a medley of uncoupling proteins (UCPs) that increase thermogenesis – the process of burning calories to produce heat.
Research has shown that high-intensity exercise, but not low-intensity exercise, increases mitochondrial content in skeletal muscles (i.e. intense exercise activates mitochondrial biogenesis).5
Furthermore, one study found that intense exercise lead to a near-8-fold increase in the expression of UCPs in skeletal muscle tissue, and this effect lasted upwards of 24 hours after exercising.6
In layman’s terms, high-intensity exercise will help you burn more calories while you’re lounging on the couch.
Intense Exercise Lengthens Telomeres
Telomeres are noncoding sequences found at the end of chromosomes. Each time a cell replicates, the telomeres shorten, and this is indicative of aging. Research suggests that even modest amounts of intense exercise could essentially reverse the aging process by inducing an enzyme called telomerase, which works to lengthen telomeres.7
Does this mean you’ll live forever just by sprinting a few times a week? Not exactly, but this stands as one of the most promising putative benefits of high-intensity exercise.
High-Intensity Exercise Increases Growth Hormone and Testosterone
Shortly after a high-intensity workout, the endocrine system goes through two highly beneficial changes.8 First off, growth hormone levels increase. Growth hormone is the quintessential “fountain of youth” since it enhances longevity and promotes healthy body composition by increasing fatty acid oxidation.9
In fact, one study found a significant negative correlation between growth hormone levels and visceral fat tissue in individuals who completed high-intensity workouts.10 Essentially, those with higher growth hormone levels had lower amounts of visceral fat.
Moreover, testosterone levels increase after intense exercise (especially resistance training), and this effect persists indefinitely as part of a consistent workout regimen.11 Testosterone is the most vital anabolic hormone that humans produce and, similar to growth hormone, is also associated with a longer life span in both males and females.12
Intense Exercise Improves Insulin Sensitivity
“Insulin resistance” is a state in which your body no longer properly responds to the signals of insulin. This usually results in chronic hyperglycemia since your cells can’t efficiently absorb glucose from the bloodstream without insulin working like it’s supposed to. When left untreated, insulin resistance can manifest into type-2 diabetes, which has become a not-so-silent killer of many people.
On the flip side, when you’re highly insulin sensitive your body is better at absorbing and utilizing carbohydrates. Interestingly, high-intensity exercise may very well serve as a necessary adjunct to overcoming type-2 diabetes since it has been shown to dramatically improve blood glucose and insulin levels in both diabetics and healthy individuals.13,14
Vigorous Exercise Improves Cardiovascular Function
A lengthy 24-week study found high-intensity training was more effective for improving cardiorespiratory fitness and blood lipid profiles in participants than moderate-intensity training (despite both forms of exercise burning the same amount of calories).15
This reinforces the fact that high-intensity exercise produces physiological adaptations that lower-intensity exercise doesn’t.
HIIT Reduces Waist Circumference and Visceral Fat Tissue
Visceral fat tissue is the fat that surrounds internal organs and lies deep in the abdominal region (think “beer belly”). Having excessive amounts of abdominal fat is a well-known risk factor for cardiovascular disease, type-2 diabetes, metabolic syndrome, and many other life-threatening health conditions.16,17,18
The good news is that intense exercise has been shown to reduce visceral fat and waist circumference significantly in just a matter of weeks.19 Ironically, one study found that low-intensity exercise had negligible impact on waist circumference and visceral fat tissue.20
How to Perform HIIT
Arguably the best thing about HIIT is that there are a myriad of exercises you can perform, most of which can be done anywhere (even in your living room if you’re in a pinch for time).
Some examples of exercises that you can use for HIIT include:
- Sprints on a track or open field tend to be best
- Stationary bike or spin cycles are also great
- Elliptical trainers can be useful
- Various other HIIT/plyometric exercises: Jumping jacks, burpees, squat jumps, etc.
- High-intensity resistance training exercises: Squats, presses, lunges, etc.
To make your workouts easier to follow, consider using a timer. There are various apps you can use for your smartphone/tablet, or even just a stopwatch will suffice.
In the long-term, high-intensity exercise is not only more beneficial for longevity, but also less time consuming.
Rather than slaving away on the treadmill for hours, you’re better off doing a full-body circuit workout, sprints, or any series of exercises that pushes you out of your comfort zone. Even a basic sprint workout can significantly benefit your health and longevity while only taking 20-30 minutes to complete (for most people).
Of course, there’s one thing that tends to scare people away from high-intensity exercise…it burns! In this regard, there is some inherent truth to the saying, “No pain, no gain” (so long as that pain is coming from lactic acid buildup).
Just keep in mind that you reap what you sow when it comes to exercise; hard work yields better results.
- Gregg, E. W., Gerzoff, R. B., Caspersen, C. J., Williamson, D. F., & Narayan, K. V. (2003). Relationship of walking to mortality among US adults with diabetes. Archives of internal medicine, 163(12), 1440-1447.
- Emberts, T., Porcari, J., Dobers-tein, S., Steffen, J., & Foster, C. (2013). Exercise intensity and energy expenditure of a tabata workout. Journal of sports science & medicine, 12(3), 612.
- Meuret, J. R., et al. “A comparison of the effects of continuous aerobic, intermittent aerobic, and resistance exercise on resting metabolic rate at 12 and 21 hours post-exercise.” Medicine & Science in Sports & Exercise, 39 (5 suppl):S247, 2007.
- Trapp, E. G., Chisholm, D. J., Freund, J., & Boutcher, S. H. (2008). The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. International journal of obesity, 32(4), 684.
- Little, J. P., Safdar, A., Wilkin, G. P., Tarnopolsky, M. A., & Gibala, M. J. (2010). A practical model of low‐volume high‐intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. The Journal of physiology, 588(6), 1011-1022.
- Jiang, N., Zhang, G., Bo, H., Qu, J., Ma, G., Cao, D., … & Zhang, Y. (2009). Upregulation of uncoupling protein-3 in skeletal muscle during exercise: a potential antioxidant function. Free Radical Biology and Medicine, 46(2), 138-145.
- Kadi, F., Ponsot, E., Piehl-Aulin, K., Mackey, A., Kjaer, M., Oskarsson, E., & Holm, L. (2008). The effects of regular strength training on telomere length in human skeletal muscle. Medicine & Science in Sports & Exercise, 40(1), 82-87.
- Kraemer, W. J., Patton, J. F., Gordon, S. E., Harman, E. A., Deschenes, M. R., Reynolds, K. A. T. Y., … & Dziados, J. E. (1995). Compatibility of high-intensity strength and endurance training on hormonal and skeletal muscle adaptations. Journal of applied physiology, 78(3), 976-989.
- Besson, A., Salemi, S., Gallati, S., Jenal, A., Horn, R., Mullis, P. S., & Mullis, P. E. (2003). Reduced longevity in untreated patients with isolated growth hormone deficiency. The Journal of Clinical Endocrinology & Metabolism, 88(8), 3664-3667.
- Slentz, C. A., Aiken, L. B., Houmard, J. A., Bales, C. W., Johnson, J. L., Tanner, C. J., … & Kraus, W. E. (2005). Inactivity, exercise, and visceral fat. STRRIDE: a randomized, controlled study of exercise intensity and amount. Journal of Applied Physiology, 99(4), 1613-1618.
- Craig, B. W., Brown, R., & Everhart, J. (1989). Effects of progressive resistance training on growth hormone and testosterone levels in young and elderly subjects. Mechanisms of ageing and development, 49(2), 159-169.
- Horstman, A. M., Dillon, E. L., Urban, R. J., & Sheffield-Moore, M. (2012). The role of androgens and estrogens on healthy aging and longevity. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 67(11), 1140-1152.
- Dunstan, D. W., Daly, R. M., Owen, N., Jolley, D., De Courten, M., Shaw, J., & Zimmet, P. (2002). High-intensity resistance training improves glycemic control in older patients with type 2 diabetes. Diabetes care, 25(10), 1729-1736.
- Henriksen, E. J. (2002). Invited review: Effects of acute exercise and exercise training on insulin resistance. Journal of Applied Physiology, 93(2), 788-796.
- O’Donovan, G., Owen, A., Bird, S. R., Kearney, E. M., Nevill, A. M., Jones, D. W., & Woolf-May, K. (2005). Changes in cardiorespiratory fitness and coronary heart disease risk factors following 24 wk of moderate-or high-intensity exercise of equal energy cost. Journal of applied physiology, 98(5), 1619-1625.
- Katsuki, A., Sumida, Y., Urakawa, H., Gabazza, E. C., Murashima, S., Maruyama, N., … & Adachi, Y. (2003). Increased visceral fat and serum levels of triglyceride are associated with insulin resistance in Japanese metabolically obese, normal weight subjects with normal glucose tolerance. Diabetes care, 26(8), 2341-2344.
- Fontana, L., Eagon, J. C., Trujillo, M. E., Scherer, P. E., & Klein, S. (2007). Visceral fat adipokine secretion is associated with systemic inflammation in obese humans. Diabetes, 56(4), 1010-1013.
- Banerji, M. A., Faridi, N., Atluri, R., Chaiken, R. L., & Lebovitz, H. E. (1999). Body composition, visceral fat, leptin, and insulin resistance in Asian Indian men. The Journal of Clinical Endocrinology & Metabolism, 84(1), 137-144.
- Broeder, C. E., Burrhus, K. A., Svanevik, L. S., & Wilmore, J. H. (1992). The effects of either high-intensity resistance or endurance training on resting metabolic rate. The American journal of clinical nutrition, 55(4), 802-810.
- Irving, B. A., Davis, C. K., Brock, D. W., Weltman, J. Y., Swift, D., Barrett, E. J., … & Weltman, A. (2008). Effect of exercise training intensity on abdominal visceral fat and body composition. Medicine and science in sports and exercise, 40(11), 1863.