The Old Science: "Walking Is Enough"
Let's frame the health question with some data from the American Heart Association:
A sedentary lifestyle is one of the 5 major risk factors (along with high blood pressure, abnormal values for blood lipids, smoking, and obesity) for cardiovascular disease.
The American Heart Association used to say (and the
government agreed) that virtually anything would satisfy the bare minimum for avoiding that "sedentary lifestyle":
[The benefits of exercise] will generally occur by engaging in at least 30 minutes of modest activity on most, preferably all, days of the week. Modest activity is defined as any activity that is similar in intensity to brisk walking at a rate of about 3 to 4 miles per hour.
That 30 minutes was even considered cumulative across the day:
It has been shown that repeated intermittent or shorter bouts of activity (such as 10 minutes) that include occupational and recreational activity or the tasks of daily living have similar cardiovascular and other health benefits if performed at the moderate intensity level with an accumulated duration of at least 30 minutes per day.
It's relevant to note:
People who already meet these standards will receive additional benefits from more vigorous activity.
The CDC breaks down the "more vigorous activity" required to achieve those "additional benefits":
- 2 hours and 30 minutes (150 minutes) each week of vigrous-intensity aerobic activity
- muscle-strengthening activities on 2 or more days a week that work all major muscle groups.
The Corrected Science: "Walking Is Almost Never Enough"
The recommendation above "has been revised by the scientists who first developed" it!
The old advice was adopted by the World Health Organization and the US and UK governments. Now it appears that while it was technically correct, it failed as policy.
Until now, government recommendations have suggested that people can achieve a minimum level of fitness through their normal daily routines. But amid fears that the lightest of activities such as dusting and the stroll to the car are being counted as exercise, a new study by the public health experts behind the formula concludes adults need to add jogging and twice-weekly weight training sessions if they want to cut their risk of heart disease and obesity.
Source: The Guardian, specifically Polly Curtis, health correspondent, on 17 August 2007.
Why did it fail as policy? Because, as the BBC shows, people thought that what they were doing was plenty exercise (hint: it wasn't):
In a survey of nearly 1,200 people, around half of men and three quarters of women thought moderate exercise conferred the greatest health benefits.
"It's extremely worrying that British adults now believe that a brief stroll and a bit of gardening is enough to make them fit and healthy," said Dr Gary O'Donovan, lead author.
"Brisk walking offers some health benefits, but jogging, running and other vigorous activities offer maximal protection from disease."
Conclusion: Walking OK - Running and Lifting Awesome
- Walking at a moderate or slow pace won't help one whit.
- Walking briskly for a good while every day will provide the bare minimum of recommended activity.
- Doing more will get the good stuff. Jogging, playing sports, and lifting heavy things will provide the health benefits we're after: increased mood and energy, avoiding heart disease and osteoporosis.
One reason we misunderstand scientists is that we only listen to half of what they say. The studies show that brisk walking provides the minimum necessary exercise if done for 150 minutes a week, and again, that is minimum time. Interpreting that to say that moderate walking 2 or 3 times a week for 20 minutes is enough is factually incorrect. We misunderstand scientists because they are using very particular language, and people normally use vague language. In this case, the scientists are trying to be more clear: the bare minimum is the bare minimum, and for any real health benefits, we'd all better get to work.