How Much Exercise is Enough? (10/31/12)
Lots of people ask me how much they should exercise. First I have to ask them what they think “exercise” is.
What Is Exercise?
Any use of voluntary muscle. The body is an information processing unit which considers and takes account of innumerable elements of which we are not consciously aware – like how physical activity affects the 100 trillion bacteria in the gut. By this definition, standing is exercise; walking is exercise; talking and cajoling and fidgeting among friends is exercise. You don’t have to go to a gym to “exercise.”
Is There Such a Thing as Too Much Exercise?
Though most of the population will never experience the negative results, the answer is certainly yes. Some people – not a lot, but some, seem genetically set to have adverse results from regular exercise – at least if you look at risk factors like high blood pressure. And many excited and pumped up high school and college athletes are less excited when suffering osteoarthritis early in life. Such “overuse” problems are far more common than the tragic head trauma occurring to football, hockey and soccer players.
As for marathons, it is remarkable that so many people can run 26 plus miles, that so many of them fully enjoy the race, and that so many describe it as a peak life experience. The first marathon runner, Theuysippus, died from his effort. It’s probably better for lots of people who like to run to run far less than 26 miles at a clip. Many middle aged people who run a lot will harm their joints – while others will fly by unscathed as they happily run.
Is There Great Individual Variation in the Effects of Exercise?
Absolutely. Genetics, nurture, diet, age all play a large role. That’s one reason it’s so hard to know what’s absolutely “best” for any individual to do, as many studies look at very specific populations whose results will not generalize to others. Clearly pleasure must be part of the equation.
Does Intensity Matter?
Yes. More data is coming out that intensity modifies inflammation and arterial resilience – once again with considerable individual variation. One recent study has 70 somethings who run or bike rapidly 2-4 hours a week showing experiencing much less brain shrinkage than those who move “less than briskly.” Some British academics argue that the majority of the population can increase insulin sensitivity and stave off metabolic syndrome (high blood pressure, obesity, sleep apnea) with quick, 20-60 second bouts of flat out exercise while walking or swimming or biking. People who do some periods of intense exercise often describe much better moods.
Yet some will go overboard – often without any idea of potential harm. There may be 200 high school athletes who die of sudden death each year (the total number is controversial), presumably because they have underlying arrhythmias and other heart disease that only shows up with intense activity – or take “aids” like energy drinks that increase their risks.
What About Walking?
Humans are walking machines. That’s one activity we’re really built to do.
Generally, if people walk about an hour a day – particularly if they move rather quickly – they will tend to maximize overall survival. Walking as briskly as possible helps.
How fast is enough? In one Australian study of 65 year old men, three miles per hour was the difference between “the quick and the dead.” Most studies show that faster movement means greater lifespan – and better quality of life. But recognize that people have very different natural speeds of walking – and that these usually slow with age. In terms of weight control, people tend to do well if they can walk about an hour a day (particularly if they add that amount to their standard physical activity regimen). In terms of exercise as a separate variable, lifespan expansion will also tend to maximize around an hour or so brisk walking each day – though some will do better with more.
What About Exercise and Sitting?
One of the more provocative research results of the last few years is the realization that athletes who sit a lot during the day suffer much higher rates of heart disease, stroke and death than expected. We may like to sit, but sitting is not good for us. So standing when typing or telephoning, even walking business meetings, may help keep people awake and alert longer, control weight – and delay the grim reaper.
Most people do far too little physical activity of any sort to worry about overdoing exercise. Remember that all movement counts- and at 20 minutes or so increases brain cell growth. Intense activity, at least intermittently, may be preferable for improving mood and avoiding diabetes and obesity. Sitting and remaining stationary counts negatively – so much so that one research group declares every hour of TV watching may decrease lifespan by 20 minutes.
Lifespan tends to maximize at physical activity levels of an hour or more each day.
When you have the chance, move.
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