Strengthen Core with Jackknives

Jackknives

Rep Range

Time Based

Hints

Begin on your back with arms straight down on the floor, using elbows to prop up your upper body. Extend legs in front. Bring both legs together feet touching each other, draw both knees to the chest at once.

Common Mistakes

Avoid collapsing the elbows or not fully extending the legs after each repetition.

Breathing

Inhale when extending legs, exhale during the crunch.

Muscle Focus

Primary Muscles

Abs

Secondary Muscles

Obliques, Hip Flexors