Is a Mile a Mile?

Wed, 12 June 2013 - 1:17 a.m. MT
Credit: ARA Staff - American Running Association

People who move their bodies for health may wonder, is distance—not speed—the most important factor in attaining the benefits associated with exercise? California-based pathologist and very first AMAA Journal editor Tom Bassler, MD, was an early pioneer in popularizing running for everyday, formerly sedentary people, including cardiac patients, and also a huge proponent of distance over speed. He even felt that walking was equally beneficial to running and encouraged slow endurance exercise to maximize cardiovascular health. The idea is that setting a distance goal will leave you out on the course longer if you choose to go slowly, and time spent moving moderately is the key to health, not how quickly you cross the finish line.

His assertions were based in epidemiological evidence, and tempered by a desire in the 1960s and 70s to see folks quit smoking and get off the couch. As noted in Hypertension: Often Symptomless, Always Worrisome, Dr. Bassler was the deputy coroner in Los Angeles County and as such started to notice on his autopsy table a correlation between healthy, youthful Achilles tendons and healthy, youthful coronary arteries.

But by what metric is walking as beneficial as running? There are many ways of examining this issue: calories burned, blood pressure, fat oxidation, metabolic rate, incidents of heart attack—the list goes on and on. Tom felt that all of this boiled down to one end-all metric: mortality rate. In one study, completed in Italy and looking at over 200 men, researchers measured how far subjects could go on a track in 20 minutes. They then waited for years to collect data on how and when they died. There is a rather linear relationship, it turns out, between how far the men could walk and how long they could live. Terry Kavanagh’s work with heart patients in Toronto has produced similar findings. 

We well know that brisk walking is a great way to attain the hour or more of moderate endurance exercise most days of the week to stay healthy. To better compare walking with running, let’s look more closely at several metrics.

Caloric Expenditure. Bassler wrote, “A mile is 100 calories, whether you walk, jog, or run.” 

An hour of 10:00-minute miles are worth 10 METs; an hour of 15:00-minute miles are worth 5 METs. It would seem then that if walking you would need to double the time of the run; the same distance covered running or walking doesn’t result in the same caloric burn, since the time it takes to complete the mile is only 50% greater but the MET value is less by half.

Calorically, using MET values from the ASCM’s 2000 Compendium of Physical Activity Tracking Guide, we can determine that a 170-pound male who jogs a 10:00 mile but briskly walks 50% slower—4 miles per hour—burns 770 calories on a one-hour run and 385 calories on a one-hour walk. But if he walks the same 6 miles he covered in an hour of running, Dr. Bassler heavily rounded out the caloric values to determine that this person burns roughly the same number of calories. 

To calculate your calories burned based on METs, use this formula: 

Weight (in kg) x METs = calories burned per hour 

This does not take into account differences in metabolism due to gender, age, or body composition. Because one pound is 0.45359 kg, if you weigh 170, you weigh about 77 kg. 

Again, you would therefore burn about 770 calories in one hour of 10:00-mile (6 mph) running, and 385 calories in one hour of 15:00-minute mile (4 mph) walking. This works out to 128.33 calories per mile of running, and 96.25 calories per mile of walking. The two values are not that far off. And this is simply the caloric metric. When Bassler declared in his 1979 book The Whole Life Diet (co-written with Robert E. Burger) that, “speed isn’t important, distance is,” he was talking about living a healthy, long life. He was correct in the notion that how long you may live is proportional to the distance you can cover on foot—and not how fast you could do so. As a result he promoted slow activities that require endurance.

Metabolic Rate. Dr. Bassler was correct that “aerobic athletes are different metabolically.” It’s been shown repeatedly that at rest marathoners burn more body fat than the rest of the population. We know from studies that people who exercise twice a day have an almost permanent elevation in metabolic rate because of it. And the most fit subjects from repeated Cooper Institute research using treadmill stress tests have heart disease death rates some 50 percent lower than the least fit. Risk of stroke, diabetes, hypertension, and even dementia are all significantly lower as well. These are not elite athletes. The subjects exercise the equivalent of 15 to 25 miles of running per week at about 10 minutes per mile.

Fat Levels in the Blood. The above metabolic improvements also occur after walking for long periods, as does the influence on the body’s ability to clear the blood of triglyerides. One study (reported in the excellent book Physical Activity and Health: The Evidence Explained and cited in this publication before) found that the rise in blood triglycerides after a high-fat meal was 43% lower in trained endurance athletes than in sedentary controls. More importantly, a single session of exercise decreases levels of fat in the blood by up to a third—and this was an equivalent result whether the subjects walked for 90 minutes at 60% VO2max or twice as long at half that intensity.

The 1996 study by Tsetsonis and Hardman showed that you can trade intensity for duration to achieve increased body fat oxidation and lower plasma triglycerides. Total energy expended looks to be the key determinant on the effects of exercise on markers of insulin resistance syndrome.

Insulin resistance is a condition in which the body produces insulin but doesn’t use it properly. Intervention studies, along with epidemiological evidence, show that exercise helps prevent insulin resistance syndrome. The syndrome manifests in a cluster of abnormalities, including impaired glucose tolerance and raised plasma triglycerides. When the body cannot properly dispose of glucose, an array of health problems can result, including type-2 diabetes.

Essentially what happens is that when people are insulin resistant, their muscle, fat, and liver cells do not respond well to insulin. Their bodies then need more insulin to help glucose enter cells. The pancreas tries to keep up with this increased demand for insulin by producing more. Eventually, the pancreas fails to keep up and excess glucose builds up in the bloodstream, setting the stage for diabetes. Ironically, many people with insulin resistance have high levels of both glucose and insulin circulating in their blood at the same time. So to enjoy the exact same fat metabolism, double the time of an easy run with a brisk walk, but Bassler’s idea that a mile is a mile is not too far off from a caloric standpoint. 

Your Activity Tells You if It’s Working. Bassler helped establish that diet and exercise are so intertwined that one can make the other seem effortless. His goal was to establish communication between diet and exercise, so your ability (or inability) to complete a long walk or run could tell you if you’re eating right, and the foods you crave on a daily basis could tell you if you’re exercising right. 

He saw that regular aerobic exercise results in improved health “because such exercise burns calories and because such exercise cries out to the jogger to change his diet.” At the same time, he proffered an encouraging idea for moderate exercisers the world over: If you’re logging 30 miles per week in five hours of vigorous activity, you may not be seeing benefits to your longevity different from the next runner who covers that mileage in 7.5 hours moderately.

 

National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, http://diabetes.niddk.nih.gov/dm/pubs/insulinresistance/#what

 

Physical Activity and Health: The Evidence Explained by Adrianne Hardman and David Stensel, 2003, Routledge, New York, NY, pp.138-143

 

The Whole Life Diet by Thomas J. Bassler and  Robert E. Burger, 1979, M. Evans and Company, Inc., New York, NY, pp. 39, 76-80, 169-170

 

ACSM Compendium of Physical Activities Tracking Guide, 2000

(RUNNING & FITNEWS® January / February 2012 • Volume 30, Number 1)




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