Build Core Strength with Single Jackknives

Single 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 one knee towards the chest with the other leg staying straight or near straight. Then, alternate.

Common Mistakes

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

Breathing

Inhale when extending leg, exhale during the crunch.

Muscle Focus

Primary Muscles

Abs

Secondary Muscles

Obliques, Hip Flexors