We all know physical activity is good for you. But why exactly is it good for you? What effect does exercise have on the cells and tissues of the body? What do we need to know so that we can use physical activity more effectively to combat chronic diseases such as arthritis, diabetes and heart disease? And what social and psychological factors prevent people from exercising or playing sports?

Elderly women can increase muscle strength as much as young women can, a new study from the University of New Hampshire finds, indicating that decline in muscle function is less a natural part of the aging process than due to a decline in physical activity.

Moderate physical activity during pregnancy does not contribute to low birth weight, premature birth or miscarriage and may actually reduce the risk of complications, according to a Michigan State University professor who contributed to the U.S. government's first-ever guidelines on physical activity.

Arthritis is the nation’s most common cause of disability. The number of adults with doctor-diagnosed arthritis is projected to increase to 67 million by 2030, and a large proportion of U.S. adults will limit their activity as a result, according to the Centers for Disease Control and Prevention.

The University of Houston department of health and human performance is launching an international effort to recruit 500 participants for a study promoting healthy dietary habits and physical activity. The study will take place entirely in the virtual world of Second Life (SL).

Voluntary physical activity does not appear to cause a reduction in anxiety and depression, but exercise and mood may be associated through a common genetic factor, according to a report in the August issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

The key to good health is to be physically active. The key to being active is… to be born that way?

New research documents the decline in physical activity among children, with less than a third meeting recommended physical activity guidelines by the time they are 15 years old, according to a study in the July 16 issue of JAMA.

UK and US guidelines on how much physical activity children need to boost their health and stave off obesity need to be revised, conclude researchers in a study published ahead of print in the Archives of Disease in Childhood.

People with diagnosed diabetes are nearly twice as likely to have arthritis, and the inactivity caused by arthritis hinders the successful management of both diseases, according to a new Morbidity and Mortality Weekly Report (MMWR) study released today by the Centers for Disease Control and Prevention (CDC).

Contrary to what many researchers expect, physically active older teens don’t necessarily eat a healthier diet than their less-active contemporaries.

Childhood obesity is a growing concern for pediatricians and caregivers. In response to this problem, the American Academy of Pediatrics (AAP) created guidelines for children regarding physical activity and screen time, which includes both watching television and playing video games.