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The One-Minute Workout

Science Shows a Way to Get Fit That's Smarter, Faster, Shorter

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Finally, the solution to the #1 reason we don’t exercise: time. Everyone has one minute.
 
A decade ago, Martin Gibala was a young researcher in the field of exercise physiology—with little time to exercise. That critical point in his career launched a passion for high-intensity interval training (HIIT), allowing him to stay in shape with just a few minutes of hard effort. It also prompted Gibala to conduct experiments that helped launch the exploding science of ultralow-volume exercise. Now that he’s the worldwide guru of the science of time-efficient workouts, Gibala’s first book answers the ultimate question: How low can you go?
 
Gibala’s fascinating quest for the answer makes exercise experts of us all. His work demonstrates that very short, intense bursts of exercise may be the most potent form of workout available. Gibala busts myths (“it’s only for really fit people”), explains astonishing science (“intensity trumps duration”), lays out time-saving life hacks (“exercise snacking”), and describes the fascinating health-promoting value of HIIT (for preventing and reversing disease). Gibala’s latest study found that sedentary people derived the fitness benefits of 150 minutes of traditional endurance training with an interval protocol that involved 80 percent less time and just three minutes of hard exercise per week.
 
Including the eight best basic interval workouts as well as four microworkouts customized for individual needs and preferences (you may not quite want to go all out every time), The One-Minute Workout solves the number-one reason we don’t exercise: lack of time. Because everyone has one minute.
Martin Gibala, Ph.D., is a professor and chair of the kinesiology department at McMaster University in Hamilton, Ontario. His research on the physiological and health benefits of high-intensity interval training has attracted immense scientific attention and worldwide media coverage. Gibala has published more than 100 peer-reviewed articles, the results of which have been featured by outlets including The New York TimesThe Wall Street JournalVox, CNN, NBC Nightly News, and Conan. He is frequently invited to speak at international scientific meetings and has received multiple awards for teaching excellence. View titles by Martin Gibala
Christopher Shulgan’s heavily-reported feature writing has won him numerous honours, most recently a National Magazine Award in 2007 in the category of politics and public policy. A former writer-at-large for Toro magazine, he is a frequent contributor to such Canadian media as The Globe and Mail and Maclean’s, He was educated at Queen’s University and Northwestern University, and lives in Toronto.
  View titles by Christopher Shulgan
Chapter One

Fit in Just ­Minutes a Week?

Feel like you don’t have time to exercise? Looking for a way to get in shape—fast? Of course you are. Regular physical activity makes you look and feel better. You’ll also fight the aging process, go through your days in happier spirits, and reduce your chance of developing ailments like cardiovascular disease, diabetes, and even cancer.

I think exercise is one of the best things around. Most of us are under the impression, however, that exercise has to be time-­intensive. We have this notion that it takes at least an hour to get in a good workout—more if you factor in the time required to get to and from the gym.

My studies show that idea is nonsense. The past decade has seen an explosion of research into the science of high-­intensity interval training, better known by its acronym, HIIT, pronounced “hit.” We’re learning that HIIT can provide ­serious benefits that increase a workout’s time-efficiency. Sprint interval training, or SIT, which is the most extreme version of the technique and is characterized by a few brief bursts of ­all-out exercise, is especially potent. We’re not just talking running here. HIIT techniques can be applied to virtually any mode of traditional cardio-type exercises, such as cycling, swimming, or rowing. Thanks to the new science of ultra-low-dose exercise, those who read this book will learn strategies to get fit in the time required to grab a coffee, update a Facebook status, or check a Twitter feed.

Think for a moment about the traditional concept of what it takes to get fit. Most of us will envision an activity that requires hours and hours of hard work. Lots of miles pedaling in the bike saddle. Entire afternoons navigating running trails. Lap after lap at the local pool. Consequently, many people are too intimidated to even try to get fit. Many of us feel like there simply isn’t enough time to fit in a workout.

But you know what? That’s wrong. That’s what my years of study have taught me. I’ve discovered that fitness is possible without spending countless hours in the gym. I don’t want to say that all the people who do that are wasting their time. But the fact is, a method exists that enables you to reap the benefits of hours of exercise in just minutes per day. Strategies can be incorporated to transform you from out of shape to fit in the least amount of time possible. Among my biggest discoveries is a workout that provides the benefits of nearly an hour of steady aerobic exercise with just a single minute of hard exercising.

Pretty remarkable, right?

This book is for the people who believe they don’t have time to exercise. In these pages, I describe techniques pulled from the latest scientific studies—how they work and how you can use them. I also provide tips on how to best manage your weight. And provide some easy methods to design muscle-­building workouts that can be conducted anywhere from hotel rooms to your local park, with little or no need for special equipment.

I know, I know—many personal trainers and workout celebrities promise such benefits. But they don’t have the deep scientific knowledge that comes from being a leading researcher in the field. The groundbreaking studies that have come out of my lab have been covered by the New York Times, Time magazine, and NBC Nightly News, to name just a few media outlets. In 2015, a review article that I wrote on the topic of ­time-­efficient exercise was the most accessed paper in the Journal of Physiology, the world’s most cited physiology journal. In fact, the top two titles on the Journal’s annual ranking of most-­accessed papers were from my laboratory, and we had three in the top fifteen. That’s quite a feat, considering all the amazing human physiology research that is conducted worldwide.

I am also fortunate to work with a lot of great people. As the chair of the Department of Kinesiology at McMaster University in Hamilton, Canada, I interact on a daily basis with people whose assembly of brainpower ranks among the best on the planet. “McMaster is one of the centers of the universe when it comes to exercise,” observes Carl Foster, a physiologist at the University of Wisconsin–La Crosse and a past president of the American College of Sports Medicine. In fact, McMaster is a world-leading center of excellence in the study of how physical activity changes human physiology and health.

With this book, I’ve drawn on the expertise of past and present McMaster minds and some of the smartest exercise physiologists in the world to create the most definitive guide to time-efficient exercise. I hope you’ll also find it’s an entertaining read. Once you’ve finished it, you’ll know enough to design your own time-efficient workouts. And you’ll have grasped the techniques required to go from out of shape to a buff portrait of health in the least amount of time.

Already fit? If you’re not using the techniques described here, chances are you’re getting beat by someone who is. This book will provide you with techniques that can help you break through a training plateau and drop seconds or even minutes from your personal-best times. It’ll also allow you more time to do other stuff, like work or hang out with loved ones, because you’re not spending hours in the saddle, on the trails, or in the pool. And during those weeks or months when work or other duties make it difficult to exercise, this book will provide you with a series of techniques designed to maintain your fitness level in the minimum amount of time.

So let’s get to discussing the most time-efficient workouts possible, for everyone from couch potatoes looking to get in shape to athletes wanting to boost their race performance. No longer do you have to fit your day around your workout. Now you can fit working out around your day.

Introducing a More Time-Efficient Way to Work Out

So what is interval training? Basically, it’s bursts of intense exercise separated by periods of recovery, which can involve complete rest or lower-intensity exercise. ­Understanding the concept is easier if you contrast it with regular endurance training. That’s the sort of thing most people envision when they think about heading out for a run. Or head out for a swim. Or a ride. The point is that traditional exercise training involves traveling a certain distance at a relatively constant pace. The resultant graph of effort versus time looks roughly like this:

That line of constant effort might stretch out to forty-five minutes, an hour, ninety minutes, or even more. When you can afford the time, it’s wonderful to get out and just run or ride with your mind at ease. That sort of training has a lot of therapeutic benefits. It reduces stress and can provide the opportunity to enjoy the outdoors. But my research has shown that it is anything but the most efficient way to train.

If time is our most valuable resource, and if we’re attempting to get the most benefit from exercise in the least amount of time, then, as my research has shown, we’re better off employing interval-training techniques. The graph of an interval-­training workout looks more like this:

The idea is to vary the intensity of your workout. Go hard, relax, go hard, relax. The harder you go, the shorter the duration and the fewer intervals you need to achieve the same benefits of a much longer endurance-training workout.

People have been trying for centuries to get the benefits of exercise in creative ways that require less time. Think about hucksters wandering the Wild West promoting health elixirs or comic-book classified ads promising strongman muscles in mere weeks. More recently, the prestigious academic journal Cell published a study about a compound, known by the acronym AICAR, that helped sedentary mice run for 44 percent farther than untreated mice. The study raised a flurry of excitement about the possibility of developing an exercise pill, yet no one’s been able to replicate the results in humans.

Interval training is the closest thing we have to an exercise pill. And over the past ten years there’s been an explosion of research into the technique. This research has been conducted in my own lab as well as those of my colleagues all over the globe. And researchers like myself have concluded that high-­intensity interval training may be the most efficient workout that the science of physiology has ever produced. Neatly summing up its benefits, A.J. Jacobs wrote in Esquire, “HIIT could be the biggest time-saver since microwaves.”

HIIT is so popular that it has ranked at or near the top of the annual list of worldwide fitness trends compiled by the American College of Sports Medicine, the largest sports medicine and exercise science organization in the world. Personal trainers everywhere from New York to Hong Kong are staging fitness classes based on principles I helped establish at McMaster, just as Hollywood stars and Victoria’s ­Secret models are using HIIT principles to get ripped for movie roles and fashion-week runway appearances. But here’s the thing: We’ve still got this idea in our heads that interval training is reserved for incredibly fit people working out in gyms in in­credibly tight clothing. And doing workouts that last about an hour.

Again, that’s nonsense. Workouts don’t have to last an hour. They can last ten minutes or even less—and get you ­remarkable fitness benefits in that time. Even if you’re overweight. Even if you’re out of shape. There is a “flavor” of interval training appropriate for you. This exciting new science of ­interval exercise can be adopted to help everyone get fit—­especially the people who long ago wrote off exercise because they felt like they didn’t have the time.

Want to get fit fast? Or just get up a flight of stairs without losing your breath? Interval training can help. Want to cut your Ironman time? Burn fat faster? Or simply increase how far you can pedal on your Sunday ride? Interval training can help with that, too.

Most important, it can help in a lot less time than you ever thought possible. Interval training is perfect especially for the most time-pressed among us—everyone from city-­hopping frequent-­flyer executives to stay-at-home parents.

Public health guidelines generally call for at least two and a half hours per week of moderate-intensity exercise to gain health benefits. Devoted fitness enthusiasts often schedule at least an hour per workout. Interval training is a way to get the benefits of an hour-long run or bike ride in a fraction of the time. In the most extreme form, known as sprint interval training, it’s possible to get those same benefits with just three minutes of hard exercise a week. In fact, my lab conducted the study that showed this—and the resultant news story rocketed to the top of the New York Times’ most-­popular-articles list.

I’m excited about this book for the same reason I’m excited about interval training itself—for their potential to make the benefits of exercise available to the greatest possible number of people. To that end I’ve tried to make this book a compelling instruction manual that’s written in plain language and understandable for those without a degree in physiology.

I tell readers what interval training is, why and how it works, and who it works for. Then I provide a series of workouts and microworkouts that have been tested in laboratories around the world, followed by a discussion of the workouts’ benefits, which have been established through rigorous scientific study.

The technique can be applied to pretty much any sort of exercise—­and the most time-efficient versions include elements that boost both cardiovascular fitness and strength. ­Cycling, swimming, or bodyweight-style movements like burpees, push-ups, and pull-ups—they all accommodate interval-­training techniques.

Now, I’m excited to translate the latest science into training techniques that virtually anyone can use.

How I Got HIIT

These days, when I conduct interviews on television shows or in newspapers, the journalists call me things like the “guru” of interval training. This makes me a bit uncomfortable, especially given the training method’s incredible history (which we’ll consider in chapter three). It’s true that I’ve devoted most of my career to researching the topic. I’ve published dozens of academic studies in peer-reviewed journals over the past decade involving every aspect of interval training—how to do it, who can benefit, and how its potency compares with that of more traditional exercise approaches.

Looking back to the beginning of my research, I can see why I started pursuing it when I did. In 2004 I had just begun my all-important second three-year contract as an assistant professor at McMaster University. Tenure is a tough thing to secure in academia, and I had less than thirty-six months to prove myself as an asset to the university—or be jettisoned from the faculty. It was my career’s ultimate make-or-break period.

On top of the pressure to produce quality research, I was teaching three courses, including one to more than two hundred undergraduates. My wife, Lisa, had just gone back to work as a high school physical education teacher. We had two young boys, ages one and three. Juggling my child-rearing responsibilities with teaching and research meant that, for the first time in my life, I felt like I didn’t have time to exercise.

I can remember coming home from my office hours and walking through my front door excited at the possibility of ­trying to squeeze in a workout. But then something would come up. The boys would need to be fed. Or we’d be out of milk. Somebody might have a fever. I’d put off exercising to cater to more pressing needs. It would be days or even a week before another chance to exercise would emerge.

Interval training at that point was largely confined to the domain of highly trained individuals focusing on athletic performance. Few regular people ever performed interval-based workouts. Explaining why the average person didn’t appreciate the value of intervals requires learning a bit about the way the body works.

Fitness means different things to different people. To exercise scientists, it means cardiorespiratory fitness, a parameter that can be measured in the laboratory by way of a test called maximal oxygen uptake or “VO2max” (the “V” stands for “volume”). It is also called aerobic fitness, and it refers to the capacity of your body to transport and utilize oxygen. Scientists have found that it’s one of the best predictors of overall health. The more aerobically fit you are, the better your heart can pump blood, the longer it takes you to get out of breath, and the farther and faster you’re able to bike or run or swim. One more thing: It also happens to be the form of fitness that helps you live longer and live better by reducing your chances of developing ailments like cardiovascular disease and diabetes. Aerobic fitness is the thing most of us want when we first start working out.

About

Finally, the solution to the #1 reason we don’t exercise: time. Everyone has one minute.
 
A decade ago, Martin Gibala was a young researcher in the field of exercise physiology—with little time to exercise. That critical point in his career launched a passion for high-intensity interval training (HIIT), allowing him to stay in shape with just a few minutes of hard effort. It also prompted Gibala to conduct experiments that helped launch the exploding science of ultralow-volume exercise. Now that he’s the worldwide guru of the science of time-efficient workouts, Gibala’s first book answers the ultimate question: How low can you go?
 
Gibala’s fascinating quest for the answer makes exercise experts of us all. His work demonstrates that very short, intense bursts of exercise may be the most potent form of workout available. Gibala busts myths (“it’s only for really fit people”), explains astonishing science (“intensity trumps duration”), lays out time-saving life hacks (“exercise snacking”), and describes the fascinating health-promoting value of HIIT (for preventing and reversing disease). Gibala’s latest study found that sedentary people derived the fitness benefits of 150 minutes of traditional endurance training with an interval protocol that involved 80 percent less time and just three minutes of hard exercise per week.
 
Including the eight best basic interval workouts as well as four microworkouts customized for individual needs and preferences (you may not quite want to go all out every time), The One-Minute Workout solves the number-one reason we don’t exercise: lack of time. Because everyone has one minute.

Author

Martin Gibala, Ph.D., is a professor and chair of the kinesiology department at McMaster University in Hamilton, Ontario. His research on the physiological and health benefits of high-intensity interval training has attracted immense scientific attention and worldwide media coverage. Gibala has published more than 100 peer-reviewed articles, the results of which have been featured by outlets including The New York TimesThe Wall Street JournalVox, CNN, NBC Nightly News, and Conan. He is frequently invited to speak at international scientific meetings and has received multiple awards for teaching excellence. View titles by Martin Gibala
Christopher Shulgan’s heavily-reported feature writing has won him numerous honours, most recently a National Magazine Award in 2007 in the category of politics and public policy. A former writer-at-large for Toro magazine, he is a frequent contributor to such Canadian media as The Globe and Mail and Maclean’s, He was educated at Queen’s University and Northwestern University, and lives in Toronto.
  View titles by Christopher Shulgan

Excerpt

Chapter One

Fit in Just ­Minutes a Week?

Feel like you don’t have time to exercise? Looking for a way to get in shape—fast? Of course you are. Regular physical activity makes you look and feel better. You’ll also fight the aging process, go through your days in happier spirits, and reduce your chance of developing ailments like cardiovascular disease, diabetes, and even cancer.

I think exercise is one of the best things around. Most of us are under the impression, however, that exercise has to be time-­intensive. We have this notion that it takes at least an hour to get in a good workout—more if you factor in the time required to get to and from the gym.

My studies show that idea is nonsense. The past decade has seen an explosion of research into the science of high-­intensity interval training, better known by its acronym, HIIT, pronounced “hit.” We’re learning that HIIT can provide ­serious benefits that increase a workout’s time-efficiency. Sprint interval training, or SIT, which is the most extreme version of the technique and is characterized by a few brief bursts of ­all-out exercise, is especially potent. We’re not just talking running here. HIIT techniques can be applied to virtually any mode of traditional cardio-type exercises, such as cycling, swimming, or rowing. Thanks to the new science of ultra-low-dose exercise, those who read this book will learn strategies to get fit in the time required to grab a coffee, update a Facebook status, or check a Twitter feed.

Think for a moment about the traditional concept of what it takes to get fit. Most of us will envision an activity that requires hours and hours of hard work. Lots of miles pedaling in the bike saddle. Entire afternoons navigating running trails. Lap after lap at the local pool. Consequently, many people are too intimidated to even try to get fit. Many of us feel like there simply isn’t enough time to fit in a workout.

But you know what? That’s wrong. That’s what my years of study have taught me. I’ve discovered that fitness is possible without spending countless hours in the gym. I don’t want to say that all the people who do that are wasting their time. But the fact is, a method exists that enables you to reap the benefits of hours of exercise in just minutes per day. Strategies can be incorporated to transform you from out of shape to fit in the least amount of time possible. Among my biggest discoveries is a workout that provides the benefits of nearly an hour of steady aerobic exercise with just a single minute of hard exercising.

Pretty remarkable, right?

This book is for the people who believe they don’t have time to exercise. In these pages, I describe techniques pulled from the latest scientific studies—how they work and how you can use them. I also provide tips on how to best manage your weight. And provide some easy methods to design muscle-­building workouts that can be conducted anywhere from hotel rooms to your local park, with little or no need for special equipment.

I know, I know—many personal trainers and workout celebrities promise such benefits. But they don’t have the deep scientific knowledge that comes from being a leading researcher in the field. The groundbreaking studies that have come out of my lab have been covered by the New York Times, Time magazine, and NBC Nightly News, to name just a few media outlets. In 2015, a review article that I wrote on the topic of ­time-­efficient exercise was the most accessed paper in the Journal of Physiology, the world’s most cited physiology journal. In fact, the top two titles on the Journal’s annual ranking of most-­accessed papers were from my laboratory, and we had three in the top fifteen. That’s quite a feat, considering all the amazing human physiology research that is conducted worldwide.

I am also fortunate to work with a lot of great people. As the chair of the Department of Kinesiology at McMaster University in Hamilton, Canada, I interact on a daily basis with people whose assembly of brainpower ranks among the best on the planet. “McMaster is one of the centers of the universe when it comes to exercise,” observes Carl Foster, a physiologist at the University of Wisconsin–La Crosse and a past president of the American College of Sports Medicine. In fact, McMaster is a world-leading center of excellence in the study of how physical activity changes human physiology and health.

With this book, I’ve drawn on the expertise of past and present McMaster minds and some of the smartest exercise physiologists in the world to create the most definitive guide to time-efficient exercise. I hope you’ll also find it’s an entertaining read. Once you’ve finished it, you’ll know enough to design your own time-efficient workouts. And you’ll have grasped the techniques required to go from out of shape to a buff portrait of health in the least amount of time.

Already fit? If you’re not using the techniques described here, chances are you’re getting beat by someone who is. This book will provide you with techniques that can help you break through a training plateau and drop seconds or even minutes from your personal-best times. It’ll also allow you more time to do other stuff, like work or hang out with loved ones, because you’re not spending hours in the saddle, on the trails, or in the pool. And during those weeks or months when work or other duties make it difficult to exercise, this book will provide you with a series of techniques designed to maintain your fitness level in the minimum amount of time.

So let’s get to discussing the most time-efficient workouts possible, for everyone from couch potatoes looking to get in shape to athletes wanting to boost their race performance. No longer do you have to fit your day around your workout. Now you can fit working out around your day.

Introducing a More Time-Efficient Way to Work Out

So what is interval training? Basically, it’s bursts of intense exercise separated by periods of recovery, which can involve complete rest or lower-intensity exercise. ­Understanding the concept is easier if you contrast it with regular endurance training. That’s the sort of thing most people envision when they think about heading out for a run. Or head out for a swim. Or a ride. The point is that traditional exercise training involves traveling a certain distance at a relatively constant pace. The resultant graph of effort versus time looks roughly like this:

That line of constant effort might stretch out to forty-five minutes, an hour, ninety minutes, or even more. When you can afford the time, it’s wonderful to get out and just run or ride with your mind at ease. That sort of training has a lot of therapeutic benefits. It reduces stress and can provide the opportunity to enjoy the outdoors. But my research has shown that it is anything but the most efficient way to train.

If time is our most valuable resource, and if we’re attempting to get the most benefit from exercise in the least amount of time, then, as my research has shown, we’re better off employing interval-training techniques. The graph of an interval-­training workout looks more like this:

The idea is to vary the intensity of your workout. Go hard, relax, go hard, relax. The harder you go, the shorter the duration and the fewer intervals you need to achieve the same benefits of a much longer endurance-training workout.

People have been trying for centuries to get the benefits of exercise in creative ways that require less time. Think about hucksters wandering the Wild West promoting health elixirs or comic-book classified ads promising strongman muscles in mere weeks. More recently, the prestigious academic journal Cell published a study about a compound, known by the acronym AICAR, that helped sedentary mice run for 44 percent farther than untreated mice. The study raised a flurry of excitement about the possibility of developing an exercise pill, yet no one’s been able to replicate the results in humans.

Interval training is the closest thing we have to an exercise pill. And over the past ten years there’s been an explosion of research into the technique. This research has been conducted in my own lab as well as those of my colleagues all over the globe. And researchers like myself have concluded that high-­intensity interval training may be the most efficient workout that the science of physiology has ever produced. Neatly summing up its benefits, A.J. Jacobs wrote in Esquire, “HIIT could be the biggest time-saver since microwaves.”

HIIT is so popular that it has ranked at or near the top of the annual list of worldwide fitness trends compiled by the American College of Sports Medicine, the largest sports medicine and exercise science organization in the world. Personal trainers everywhere from New York to Hong Kong are staging fitness classes based on principles I helped establish at McMaster, just as Hollywood stars and Victoria’s ­Secret models are using HIIT principles to get ripped for movie roles and fashion-week runway appearances. But here’s the thing: We’ve still got this idea in our heads that interval training is reserved for incredibly fit people working out in gyms in in­credibly tight clothing. And doing workouts that last about an hour.

Again, that’s nonsense. Workouts don’t have to last an hour. They can last ten minutes or even less—and get you ­remarkable fitness benefits in that time. Even if you’re overweight. Even if you’re out of shape. There is a “flavor” of interval training appropriate for you. This exciting new science of ­interval exercise can be adopted to help everyone get fit—­especially the people who long ago wrote off exercise because they felt like they didn’t have the time.

Want to get fit fast? Or just get up a flight of stairs without losing your breath? Interval training can help. Want to cut your Ironman time? Burn fat faster? Or simply increase how far you can pedal on your Sunday ride? Interval training can help with that, too.

Most important, it can help in a lot less time than you ever thought possible. Interval training is perfect especially for the most time-pressed among us—everyone from city-­hopping frequent-­flyer executives to stay-at-home parents.

Public health guidelines generally call for at least two and a half hours per week of moderate-intensity exercise to gain health benefits. Devoted fitness enthusiasts often schedule at least an hour per workout. Interval training is a way to get the benefits of an hour-long run or bike ride in a fraction of the time. In the most extreme form, known as sprint interval training, it’s possible to get those same benefits with just three minutes of hard exercise a week. In fact, my lab conducted the study that showed this—and the resultant news story rocketed to the top of the New York Times’ most-­popular-articles list.

I’m excited about this book for the same reason I’m excited about interval training itself—for their potential to make the benefits of exercise available to the greatest possible number of people. To that end I’ve tried to make this book a compelling instruction manual that’s written in plain language and understandable for those without a degree in physiology.

I tell readers what interval training is, why and how it works, and who it works for. Then I provide a series of workouts and microworkouts that have been tested in laboratories around the world, followed by a discussion of the workouts’ benefits, which have been established through rigorous scientific study.

The technique can be applied to pretty much any sort of exercise—­and the most time-efficient versions include elements that boost both cardiovascular fitness and strength. ­Cycling, swimming, or bodyweight-style movements like burpees, push-ups, and pull-ups—they all accommodate interval-­training techniques.

Now, I’m excited to translate the latest science into training techniques that virtually anyone can use.

How I Got HIIT

These days, when I conduct interviews on television shows or in newspapers, the journalists call me things like the “guru” of interval training. This makes me a bit uncomfortable, especially given the training method’s incredible history (which we’ll consider in chapter three). It’s true that I’ve devoted most of my career to researching the topic. I’ve published dozens of academic studies in peer-reviewed journals over the past decade involving every aspect of interval training—how to do it, who can benefit, and how its potency compares with that of more traditional exercise approaches.

Looking back to the beginning of my research, I can see why I started pursuing it when I did. In 2004 I had just begun my all-important second three-year contract as an assistant professor at McMaster University. Tenure is a tough thing to secure in academia, and I had less than thirty-six months to prove myself as an asset to the university—or be jettisoned from the faculty. It was my career’s ultimate make-or-break period.

On top of the pressure to produce quality research, I was teaching three courses, including one to more than two hundred undergraduates. My wife, Lisa, had just gone back to work as a high school physical education teacher. We had two young boys, ages one and three. Juggling my child-rearing responsibilities with teaching and research meant that, for the first time in my life, I felt like I didn’t have time to exercise.

I can remember coming home from my office hours and walking through my front door excited at the possibility of ­trying to squeeze in a workout. But then something would come up. The boys would need to be fed. Or we’d be out of milk. Somebody might have a fever. I’d put off exercising to cater to more pressing needs. It would be days or even a week before another chance to exercise would emerge.

Interval training at that point was largely confined to the domain of highly trained individuals focusing on athletic performance. Few regular people ever performed interval-based workouts. Explaining why the average person didn’t appreciate the value of intervals requires learning a bit about the way the body works.

Fitness means different things to different people. To exercise scientists, it means cardiorespiratory fitness, a parameter that can be measured in the laboratory by way of a test called maximal oxygen uptake or “VO2max” (the “V” stands for “volume”). It is also called aerobic fitness, and it refers to the capacity of your body to transport and utilize oxygen. Scientists have found that it’s one of the best predictors of overall health. The more aerobically fit you are, the better your heart can pump blood, the longer it takes you to get out of breath, and the farther and faster you’re able to bike or run or swim. One more thing: It also happens to be the form of fitness that helps you live longer and live better by reducing your chances of developing ailments like cardiovascular disease and diabetes. Aerobic fitness is the thing most of us want when we first start working out.