Intensity Beats Cancer: Why Vigorous Exercise Matters for Long-Term Health

Let me preface this article by reminding you that all exercise is good for you.

Walking, jogging, yoga, Zumba, strength training, CrossFit — it all counts. Regular physical activity is associated with a lower risk of all-cause mortality, cardiovascular disease and several types of cancer.

So I am not arguing that one type of exercise is good and another is useless. I don't believe in either-or.

I want you to do it all.

More importantly, I want you to understand why.

Because different types and intensities of exercise challenge the body in different ways. And high-intensity exercise provides some powerful benefits that we should not ignore.

Your Body Adapts to What You Ask of It

Let's start with the concept of an adaptive threshold.

To force a physiological adaptation, you need to give your body a sufficient reason to adapt. A stimulus that is comfortably below your current capacity may still have benefits, but it won't necessarily produce the same adaptations as a greater challenge.

This is easy to understand with strength training.

Lifting a 1-pound weight 100 times will not make you as strong as lifting a 100-pound weight once. Two reps at 100 pounds will not elicit the same adaptations as one rep performed at 200 pounds. And so on. If you want to build strength, at some point you need to ask your muscles, bones and nervous system to do something they are not already completely comfortable doing.

The same basic principle applies to cardiovascular fitness.

If you want your body to become better at handling high demands, occasionally you need to expose it to high demands.

Why Intensity Matters for Your Heart

During vigorous exercise, your heart rate rises, cardiac output increases and your blood vessels are exposed to very different demands than they experience during an easy walk.

Over time, exercise can improve cardiovascular fitness, endothelial function and vascular health. Research suggests that physical activity at a variety of intensities is beneficial, with higher-intensity aerobic exercise potentially producing particularly meaningful improvements in some measures of cardiovascular health.

That doesn't make walking useless. Far from it.

A ruck walk, long hike or easy bike ride can be fantastic for building aerobic capacity, accumulating movement and supporting recovery. But it creates a different physiological challenge than a hard sprint.

And that is the point.

Different doses of exercise create different adaptations.

For long-term health and health span — the years of life you remain healthy, capable and independent — we want more than just one kind of stimulus.

What About Cancer?

This is where things get especially interesting.

We have known for years that regular physical activity is associated with a reduced risk of several cancers. Exercise can influence insulin sensitivity, chronic inflammation, body composition, hormone regulation and immune function — all factors that may affect cancer risk.

But vigorous exercise adds another layer.

During intense exercise, the body undergoes a dramatic temporary shift. Stress hormones rise. Blood flow changes. Skeletal muscles release signalling molecules. Immune cells, including natural killer cells and other cytotoxic immune cells, are mobilized into circulation.

Researchers are still working out exactly how all of these mechanisms influence cancer development and progression. We should be careful not to simplify this into "hard exercise kills cancer cells." Human biology is much more complicated than that.

But the emerging evidence around vigorous activity is compelling.

A large study of more than 22,000 adults who did not otherwise exercise found that even very short bursts of vigorous activity were associated with a lower incidence of cancer. The researchers found benefits beginning with only a few minutes of vigorous activity per day.

Think about that.

Not an Ironman.

Not a marathon.

Minutes.

You Need Easy AND Intense

This brings me back to where we started.

I don't want you to stop walking.

I don't want you to abandon your yoga class, your easy bike rides, your hikes around Vancouver or whatever other movement you enjoy.

Low- and moderate-intensity activity allow you to accumulate a large volume of movement without beating yourself up. They support aerobic fitness, metabolic health, recovery and your ability to remain active as you age.

But I also don't want you to be afraid of intensity.

Especially as we get older, the temptation can be to make everything easier. Lift lighter. Move slower. Avoid getting out of breath.

There are certainly times when that is appropriate. But healthy aging isn't about removing every physical challenge from your life.

It is about maintaining the capacity to meet challenges.

That means strength training.

It means mobility.

It means aerobic work.

And it means occasionally going hard.

Good coaching matters here. Intensity is relative to the individual. A beginner in their 50s or 60s does not need to train like a 25-year-old competitive athlete to benefit from vigorous exercise. The appropriate dose is the one that challenges your current capacity while allowing you to train safely and consistently.

That is one of the things we work hard to get right at Empower.

Hard Is Not the Same as Intense

One more thing.

A hundred-mile bike ride is hard. But it isn't necessarily intense in the way I am using the word here.

Even HYROX, hard as it is, involves pacing and sustained effort.

Compare that with a 100-metre sprint.

Or a heavy one-rep-max lift.

Those efforts require enormous output over a very short period of time.

In CrossFit, we often think of intensity in terms of power: doing more work in less time.

That distinction matters.

You can do something extremely difficult for several hours. You can also do something for 20 seconds that requires almost everything you've got.

They are not the same physiological experience.

And we benefit from training both.

I Intend to Put Up a Fight

Intensity sucks.

There is no way around that.

When I enter the pain cave, however, I remind myself why I am there.

I am training for more than today's workout.

I am training for health span. For resilience. For strength. For the ability to keep doing the things I love as I age.

And yes, I think about heart disease.

I think about cancer.

I can't guarantee that exercise will prevent either one. None of us can.

But I can improve the odds.

So when the workout gets uncomfortable, I imagine myself looking death in the eye and saying:

No.

Not today.

I'm in a fight for my life that I intend to win.

So are you.