Exercise and cancer- why it helps and how much is enough? (part 2)

Posted on May 4, 2016

(Last Updated On: May 11, 2016)

This is a four part series-

A framework for why this matters

For every fitness variable -things like strength, endurance, speed- we have certain thresholds we should hit to optimize results. When we mix them -think any and every sport- things change and we have new parameters we try to hit. We’re always tinkering to see what those parameters should be. Soccer do this mixture (more endurance focused), football do this mixture (more strength focused), 100 meter runner here (almost all speed), marathon runner there (almost all endurance). And it changes based on the person. One soccer player might be able to run for days, but they fall apart every time they get slide tackled. They can get by with doing less endurance work, but need some serious time in the weight room.

What about for disease though? So often we’re told “you should be exercising.” Ok, what does that mean? You don’t tell a football player “you should be exercising.” If they want to get stronger, you tell them you should be resistance training. Ok, but still, what does that mean? Sets? Reps? Frequency? Intensity? Exercises? We strive for some specificity as that often increases results.

We don’t ever do this with cancer, and barely ever with disease. The only exception here is probably cardiac rehab i.e. rehab after a heart attack. Even then, the prognosis too often seems to be “walk as tolerated.”

There is research -though it’s often too vague as well- dedicated to optimizing parameters, yet it doesn’t seem to be implemented much.

If we look at the cancer.gov discussion on physical activity, we see things like this,

“The Centers for Disease Control and Prevention (CDC) recommend that adults “engage in moderate-intensity physical activity for at least 30 minutes on five or more days of the week,” or “engage in vigorous-intensity physical activity for at least 20 minutes on three or more days of the week””

Does anyone have any idea what that statement means? What’s moderate intensity? What’s vigorous? If we asked 20 different people to demonstrate, we’d get 20 different examples.

Furthermore, here is what it says for the colorectal cancer section (bolding mine),

The magnitude of the protective effect appears greatest with high-intensity activity, although the optimal levels and duration of exercise are still difficult to determine due to differences between studies, making comparisons difficult. It is estimated that 30 to 60 minutes of moderate to vigorous physical activity per day is needed to protect against colon cancer.”

First, why don’t we have better quality research on this? Technology is not a limitation in this regard. It’s not complex to look at sets, reps, frequency, type of exercise, etc. We just haven’t done the studies. Considering the magnitude of an affect we can get from exercise, as we’ll see, this is disappointing.

Second, those values for colorectal don’t match up with the CDC recommendations. Initially the recommendation was moderate to vigorous. But for colorectal it looks like you want vigorous. This is what’s meant by different diseases may require different parameters.

Third, that comes across as it’s not all equal. That perhaps there is a difference whether you do vigorous or moderate. It’s not only how much you do in total, for example- do more moderate intensity to make up for not doing any vigorous intensity. It’s whether and how much you do each one– do all the moderate you want, but for optimal results we need at least X amount of vigorous.

This is critical because it’s common for people to think if they walk a bunch, or if they kneel and stand up a bunch in their gardening, they’re good. That might not be enough based on what this is saying. You could walk 100 miles a week, but if it’s all below a certain pace, you might not be getting the optimal benefit, or any benefit, because your parameters are not optimal. Much like an American football player could run miles and miles; that probably won’t help him play a sport where the average play is 3 to 4 seconds. (In fact, it might hurt the ability to play football.)

Still, what is moderate and vigorous? Look around, such as on heart.org, and we get this,

  • Moderate-intensity physical activity is defined as – physical activity done on a scale relative to an individual’s personal capacity, moderate-intensity physical activity is usually 11-14 on a scale of 1 to 20.
  • Vigorous-intensity physical activity is defined as – physical activity done on a scale relative to an individual’s personal capacity, vigorous-intensity physical activity is usually 17-19 on a scale of 1 to 20.

So it’s all relative then? Is it just how you feel while doing something?

Part three: 

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