Science and Medicine

Americans exercise almost three times more than they did 40 years ago

Americans exercise almost three times more than they did 40 years ago, but still far less than the recommended four hours a week.

The U.S. Centers for Disease Control and Prevention recommends that adults aged 18 to 64 exercise moderately for 2.5 hours per week and engage in a vigorous activity, such as running and muscle strengthening, for an hour and fifteen minutes per week. The current average time Americans spend on exercise is two hours a week.

“The United States is the fattest country in the world,” says Geoffrey Godbey, professor emeritus of recreation, park and tourism management at Penn State. “The amount of exercise Americans get has become a major concern.”

Godbey and colleague John Robinson, professor of sociology at the University of Maryland, analyzed American Time Use Survey (ATUS) data from the U.S. Census Bureau’s most recent national diary study of more than 100,000 respondents of all ages across the country to examine the amount of time Americans spend on sports and fitness activities.

The results are reported in the 2011 edition of Time Use in Australia and United States/Canada Bulletin, which will appear online this week.

Read more: Americans Exercise More, But Not Enough

Cooperation favors same-handedness—for sharing the same tools, for example.

Left-handed people are relatively rare because of the balance between cooperation and competition in human evolution, according to a new study of sports data.

Representing only 10 percent of the general human population, left-handers have been viewed with suspicion and persecuted across history. The word “sinister” even derives from “left or left-hand.”

Researchers at Northwestern University now report that a high degree of cooperation, not something odd or sinister, plays a key role in the rarity of left-handedness.

They developed a mathematical model that shows the low percentage of lefties is a result of the balance between cooperation and competition in human evolution.

Professor Daniel M. Abrams and graduate student Mark J. Panaggio—both right-handers—are the first to use real-world data (from competitive sports) to test and confirm the hypothesis that social behavior is related to population-level handedness.

The results are published this week in the Journal of the Royal Society Interface.

“The more social the animal—where cooperation is highly valued—the more the general population will trend toward one side,” said Abrams, an assistant professor of engineering sciences and applied mathematics at the McCormick School of Engineering and Applied Science. “The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.”

Read more: Sports Stats Show Why Lefties are Rare