How High Is High in High-Intensity Training?

Alex McMillan

Alex McMillan

Head Trainer, Mid Age Man

To get the most benefit from exercise, try to push your body in high-intensity bursts. But what does high intensity mean?

I’m a firm believer in high-intensity exercise. It’s the best and fastest way to lose weight, get fit, and build muscle.

Personally, I favor high-intensity interval training, or HIIT, a specific form of high-intensity exercise. You can, though, get your intensity any way you like.

But how high is high? What does high intensity mean?

I’m reminded of the definition that U.S. Supreme Court Justice Potter Stewart gave for hard-core pornography: “I know it when I see it!”

You’ll know the exercise is high intensity if it feels intense to you. For someone who is morbidly obese, this might mean just walking up the stairs. The rest of us need to put in a little more effort.

There’s been a little discussion as to whether very intense exercise over long periods of time is bad for you. After all, the marathon as a race is based on an episode in which a herald called Pheidippides ran around 42 kilometers from Marathon in Greece to Athens to tell everyone that the Greeks had secured a famous victory over the Persians.

“Joy, joy to you, we’ve won,” he supposedly said.

And then he dropped dead.

Now, I say “supposedly said” because this story sounds like quite an elaborate fable to me. Those ancient Greeks were always running around and dropping dead, turning people to stone and morphing into deer while they were at it, then telling the future, stealing golden wool, and having sex with a god who had turned into a swan. There was definitely something in the water.

Yet there might be something to it. Not the swan part, the dropping dead.

Jim Fixx, the author of The Complete Book of Running, actually did drop dead, of a heart attack. After the same thing happened to a few other runners, people began to question the benefits of running flat out.

Set your own limits, and only attempt high-intensity workouts when you feel in good condition, but attempt to drive your heart rate to 85% of its maximum rate for maximum benefit.

Several studies have found that endurance athletes who spend years training and competing at extremely high intensities have surprising formations in their hearts and arteries.

Middle-aged male triathletes have more scarring inside their hearts, a.ka. myocardial fibrosis, than regular people and even female triathletes, according to research presented late last year to the Radiological Society of North America.

The docs studied 55 men, who had an average age of 44. There was scarring in the left ventricle, the part that does the bulk of the heart’s pumping, in 10 of them. That’s 18%. And those men were the hard-core athletes, who had swum farther, cycled harder and hit a higher peak systolic blood pressure than the other triathletes in the study.

There was no scarring in the hearts of the 30 women in the study, who had an average age of 43. But the men in general had done more Iron Man competitions and attacked more middle-distance races than their more-sensible female equivalents.

Testosterone may have something to do with it, but the scarring when it happens is definitely exercise-related, the experts at the medical center in Hamburg, Germany, that conducted the study concluded. “Repetition of any extreme athletic activity may not be beneficial for everyone,” Jita Starekova, the doctor who headed the research, said.

Two other recent studies, one in the Netherlands and one in Britain, looked at close to 600 people who exercise a lot, whether running or biking. They found that those very fit people also tend to have more plaque in their artery walls than normal folks. And of course, plaque is a sure precursor of heart disease. Looking at training regimens and race times, the folks in lab coats figured out that the more the person had exercised, the more plaque they had.

The good news is that the plaque is different from the kind you’d find in fatties who just sit around all day. The plaque from the crazed runners and cyclists is calcified and dense, meaning it is likely to stay where it is. The formations are more “benign,” in the words of a cardiologist who wrote about the findings in the journal Circulation, which of course we all read religiously.

Regular out-of-shape people who develop plaque in their arteries develop buildups that are fatty and loose, a bit like their bodies in general. That makes it much more likely that the plaque will break free and cause a heart attack.

Yet another study by boffins from the University of Minnesota and Stanford University looked at people who had done something very specific: men who had run at least 25 of the Twin Cities marathon in Minneapolis-St. Paul. In a row. Not all at once of course. You would drop dead from that. They had run them consecutively, over the years.

They hadn’t just done the Twin Cities race, either. The 50 mad runners that the doctors discovered had run a combined 3,510 marathons. That’s 70 marathons per man.

Some of them had started in high school, or even earlier. Others had come to road racing late. Most ran 30 miles or more per week.

Of those 50, 16 had no plaque in their arteries at all. Another 12 had some plaque, another 12 moderate plaque, and the final 10 had worryingly large amounts.

It did not turn out that the men who had run the most inevitably had the most plaque. Instead, a history of heavy smoking and high cholesterol in the past was a better indicator. Years of hard running hadn’t harmed their hearts, and may have kept some of them clear.

It was lifestyle choices that explained the bulk of the plaque. “You can’t just outrun your past,” the leader of the study said.

Whether you’re running, biking, swimming or working out, you should do so in short bursts of high intensity if you want to boost your metabolism, burn calories and develop tone.

The overall conclusion I draw from all these studies is that running hard does appear to stress your heart. But it’s not doing life-threatening damage. The benefits of being slim and fit would outweigh any scarring or plaque, which if it develops appears to be the “good kind” of plaque.

Your heart is pumping harder when you exercise hard. This may cause some scarring, although not in everyone, particularly if you’re a woman. I have a hunch – though the studies haven’t found this – that the plaque would have formed anyway in the runners who developed it, due to dietary and lifestyle choices, but thanks to the running it became hard and stuck to the artery walls, where it hopefully stays.

However, I would not overdo high-intensity exercise. A Hong Kong policeman who was very fit tried running on a hot and humid day here in Sai Kung, when he wasn’t feeling that great to start with. After running hard for a while with a colleague, he said he felt funny, really tired, sat down – and eventually keeled over dead, of heat stroke.

In another episode, a pro tennis coach who was also very fit nevertheless had a history of partying a lot. From all reports, he had a big night out, then taught a few hours of tennis lessons the next day in the Hong Kong heat, then decided to push his limits with a hard-core run at lunch. And he had a heart attack, and died.

You should build up your capacity for high-intensity exercise. And you should only go for intense training if you’re feeling well-rested, hydrated and in the right frame of mind. Listen to your body.

I would suggest starting with 10 second bursts of going all out. Then rest a little, with some mild exercise while you catch your breath. Then go for it again.

The “Tabata Protocol” may sound like something from The Bourne Identity. But it’s a high-intensity tactic developed by the exercise physiologist Izumi Tabata while working with the Japanese speed-skating team. It involves 8 bursts of 20 seconds of all-out intensity interspersed by 10-second rest breaks. That’s a four-minute workout in all. It’s highly efficient, and highly effective.

Starting with 10 seconds, then building to 20, adding extra sets as you go, is a good way to go. I’ll leave the break in between up to you and your body – we’re not all Olympic speed skaters. But you should be going at around 85% of your hardest in your high-intensity phases.

You’ll only be able to sustain this very high heart rate for a short amount of time, of course. Those 10 or 20 seconds of high-intensity exercise will seem longer than they sound. At close to full effort, like a car crash, everything seems to move in slow motion, while you have heightened awareness of everything that’s going on.

For high intensity exercise, the idea is to get your heart rate right up to around 85% of the fastest your heart can go. So, you can think of performing whatever exercise you have picked at 85% of the absolute maximum you can give.

As a rough guideline for your “maximal hear rate,” the theoretical fastest your heart would go, you can use the formula developed by Hirofumi Tanaka, the director of the Cardiovascular Aging Research Laboratory at the University of Texas, and his team.

Take the number 208 and subtract 0.7 x your age. So, if you’re 40, that’s 208 – (0.7 x 40) = 180 beats per minute.

Tanaka’s formula builds on an earlier version of working out your max heart rate that is simply 220 minus your age. So, for someone who’s 40, that is 220 – 40 = 180.

Same difference. There are actually variations for other ages, but they’re pretty close.

Don’t try to find out what your actual maximum heart rate is! By definition, you’d die! You’ve gone too fast! Remember the marathon runner!

But to burn fat and force your body to regenerate, speeding up your metabolism in the process, you need to hit that high-intensity threshold. Once you’ve found it, you can constantly push it a little further each time. People who exercise at high intensities regularly develop higher maximal heart rates. The above formulas can be misleadingly low for people used to Tabata-style intensity-burst workouts.

The good news is you can pick your exercise “poison,” whatever activity you enjoy the most. But whatever you do, be it biking, swimming, running, weight training, suspension training with a TRX, pole dancing or jumping rope, you should put in short bursts of highly intense exercise that pushes you to your limits. Sprint at your fastest, then slow down and “jog,” whatever the sport. Your heart should be beating, almost as fast as it can go.

If you do that, your body will obviously burn a lot of energy during those bursts. But it will also be burning more energy while you are resting and after your workout. You will be breathing harder than normal – you may not even notice it – for even a few hours to replenish the “oxygen deficit” you will have created.

And you will force your body to repair. You will build more muscle if you have stressed your body through resistance work, and this afterburn effect continues for up to 48 hours. This all requires energy, and burns calories. You will literally have boosted your metabolism.

You be the judge of whether you’re really going for it. And you be the judge for when it’s time to stop. But that high intensity, that 85% of max, is what you’re chasing. It’ll not only burn fat and build muscle while you’re excising, but for a day or two afterwards.

That’s how you get the real health benefit of high-intensity interval training. You have to shock your body a little – and it will respond.

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About the author

Alex McMillan

Alex McMillan

Head trainer at Mid Age Man. Alex believes there are four pillars to being healthy: physical fitness, sensible nutrition, mental strength, and wellbeing for your body and soul.

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