Global physical activity levels - Need for intervention.

Substantial evidence shows that physical inactivity (PI) and sedentary behavior (SB) increases the risk of many chronic diseases and shortens life expectancy. We describe evidence that certain domains of physical activity (PA) in the United States (US) population have declined substantially over 5 decades. The prevalence of PI is very high worldwide, which has contributed to 6%-10% of the burden of many chronic diseases and premature mortality. Reduction or elimination of PI would likely produce substantial increases in life expectancy of the world's population. Great efforts are needed to reduce PI and SB and increase levels of PA in the US and worldwide.