Researcher Stephen Brusatte says scientists have believed that the physical qualities of Tyrannosaurus developed because of its large body.

VOA: special.2009.10.13

Stress is how your body reacts to physical, chemical,emotional or environmental influences.

VOA: special.2009.03.24

The C.D.C.defines physical activity as anything that gets your body moving.

VOA: special.2010.06.08

Physical activity produces body heat.

VOA: special.2010.07.27