Jumping jacks are a popular physical exercise that involves jumping while spreading the legs and arms simultaneously. To perform a jumping jack, start in a standing position with your feet together and arms at your sides. Jump up, spreading your legs shoulder-width apart while raising your arms above your head. Then, return to the starting position. This exercise is often used in warm-ups and fitness routines because it increases heart rate and improves overall cardiovascular fitness. Jumping jacks can be done anywhere and require no special equipment, making them accessible for people of all fitness levels.