Double-under
/ ˌdʌbəl ˈʌndə(r) / · noun (plural: double-unders)
Also: DU, double under
A jump-rope movement in which the rope passes under the feet twice during a single jump. The athlete jumps slightly higher than for a regular skip and accelerates the rope so that it completes two full rotations between takeoff and landing. Double-unders test rhythm, calf endurance, and concentration under fatigue, and have appeared in nearly every CrossFit Open since 2012.
Movement standard
For a rep to count under standard CrossFit rules: the rope must rotate twice on a single jump, and the athlete must clear the rope on both passes. A single under between two double-unders does not count as a double-under, though athletes are generally allowed to mix singles and doubles freely (only the doubles count toward the rep total). Open events typically require unbroken sets only when the workout description explicitly demands them: most workouts count cumulative reps regardless of breaks.
Mechanics
The biggest mistake recreational athletes make is treating the double-under as a high jump. It is not. The jump is barely higher than for singles: the difference is in rope speed, not air time.
- Posture: trunk vertical, ribs stacked over hips. Eyes forward, not down at the rope.
- Jump: a small bounce off the balls of the feet, ankles doing most of the work. Knees stay relatively quiet; piking forward at the hip kills the rhythm.
- Wrists: the rope speed comes from the wrists, not the arms. Elbows stay tucked roughly at hip height; the hands rotate small circles. Larger arm movements waste energy and slow the rope.
- Rhythm: one even bounce per double-under. Trying to bounce twice (once for each rope pass) breaks the rhythm and burns out the calves within seconds.
Common mistakes
- Jumping too high: burns out the calves in 30 seconds and creates a piked landing position. A small bounce is enough.
- Pike (knees forward, heels back): the body shape that develops when athletes try to "make room" for the rope. The fix is staying vertical; the rope passes under without the body contorting around it.
- Tucking the knees up: common compensation when the rope is too short or the athlete is rushing. The cue "long body, fast rope" addresses this.
- Looking down at the rope: drops the chest and disrupts balance. Keep the gaze forward at a fixed point.
- Spinning the arms: opens the rope arc and slows it. Hands stay close to the hips, wrists do the work.
Programming
Double-unders are most often used as a metabolic conditioning tool, where the demand is sustained capacity rather than max effort:
- Capacity sets: 5 × 50 unbroken with 60 seconds rest. Builds the unbroken capacity needed for 100+ rep workouts.
- EMOM under fatigue: every minute on the minute, 30 double-unders + 5 burpees for 10 minutes. Trains the recovery between sets that race-day workouts demand.
- Open prep: the Open often uses 50 or 100 unbroken double-under requirements. Athletes who can't reliably string together 75+ at race pace fail the cut to the next round of work.
Equipment notes
Rope length is the single biggest determinant of success for newer athletes. Standing on the middle of the rope with one foot, the handles should reach roughly to the elbow when the cable is pulled vertical. Speed ropes (steel cable, ~5 oz / 150 g handles) are the standard for competition; weighted ropes (typically 8–16 oz (225–450 g)) are used as training tools to build wrist endurance and feel the rope pass. Beaded or leather ropes are slower and harder to use efficiently. Athletes train with the rope they intend to race with, since handle balance and rope feel matter as much as rotation speed.
Sources
- CrossFit Level 1 Training Guide
- CrossFit Open Movement Standards (annual)
- Essentials of Strength Training and Conditioning, 4th ed.