Jumping jack

A jumping jack, also known as a star jump and called a side-straddle hop in the US military, is a physical jumping exercise performed by jumping to a position with the legs spread wide and the hands going overhead, sometimes in a clap, and then returning to a position with the feet together and the arms at the sides.

The name origin for the jumping jack exercise has sometimes erroneously been identified as World War I U.S. General John J. "Black Jack" Pershing,^[1] who is said to have developed the exercise, but in fact the name comes from the jumping jack children's toy, which makes similar arm swing and leg splay motions when the strings are tugged.

Although he played no part in inventing the exercise, the late fitness expert Jack LaLanne was given credit for popularizing it in the United States. LaLanne used the jumping exercise during routines he promoted in decades of television fitness programming.^[2]

The exercise can be made more or less intense with different variations. In general, squatting deeper will make jumps more difficult, although not resulting in greater height than squats at <90. According to studies, greater height is achieved when performing the jump from a shallower squat position (star jumps are often performed from a quarter squat position), while deeper squats are more effective at improving vertical jump height.

The legs are stepped to the side without jumping, with the knees slightly bent and keeping in line with the ankles.

In an intermediate variation, the legs hop out to shoulder width while raising the arms, then hop back together while lowering the arms.^[3]

Power jacks are like jumping jacks but land in a wide squat position. As with other jumps, jumping out of a deeper squat position increases the intensity of the exercise and this can result in injury if proper form is not maintained in the deep squat position between successive jumps. Power jacks can be performed over multiple counts to pull the legs back to center with two small incremental jumps to return to the starting position,

Squat jacks are performed by jumping the legs out and in while staying in a half squat position.

Star jumps are more explosive and performed with greater height than regular jumping jacks. Instead of landing in a wide stance the legs are swung out laterally in the air and pulled back to center to land in a tucked narrow squat. They are a rebounding jump beginning and landing in the tucked narrow squat position to continue successive jumps.

A similar jump exercise is called half-jacks, which were created to prevent rotator cuff injuries, which have been linked to the repetitive movements of the exercise. They are like regular jumping jacks but the arms go halfway above the head instead of all the way above it. The arms also hit the sides to help tighten the jump.

The most jumping jacks performed in one minute is 136 - achieved by Binod Thapa in Kathmandu, Nepal, on 28 July 2023.^[4]

In 2010, National Geographic Kids organized an event in 1,050 locations as a part of Michelle Obama's "Let's Move!" exercise campaign in which 300,365 people were measured doing jumping jacks (for one minute) in a 24-hour period.^[5]

• Split jack

• Star Jump Demonstration Archived 16 February 2022 at the Wayback Machine