Cocoons
From flat on your back with arms overhead and legs straight, you fold into a ball — knees to chest, hips off the floor, arms swinging over to meet them — then extend back out long. It combines a reverse crunch and a crunch in one rep, and the long starting position is what makes it harder than either.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie flat on a mat with your legs straight and together, arms extended past your head on the floor.
- Press your lower back into the mat before the first rep and hold that contact as long as you can.
- Point your toes slightly and keep your knees together — the legs move as one unit.
- Take up the slack: no gap between your lumbar spine and the floor, ribs down, not flared toward the ceiling.
Every rep
Breathing & tempo — Exhale hard as you fold and finish the breath at the tuck, inhale as you extend. One second in, one to two seconds held, three to four seconds out.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Bodyweight only, and there is no clean way to load it — a dumbbell in the hands wrecks the arm path. Progress by extending further toward the floor, holding the tuck for two seconds, and slowing the extension to four seconds. When a set of 20 with a four-second extension is comfortable, move to a hanging or rollout variation instead of adding reps.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Shorten the extension — stop with your heels 20 cm above the floor and your arms at 45 degrees rather than fully flat. Extend further only as far as you can keep the lumbar spine pressed down.
Slow the arms to the same speed as the legs and pause a full second at the tuck. If the rep only works when you throw your arms, cut the reps in half and do them deliberately.
Aim to lift the glutes a hand's width off the mat on every rep. Knees moving without pelvis moving is hip flexion, and the abs are only spectators.
Cap the set at 15-20 controlled reps with a pause at each end. When that gets easy, slow the extension to four seconds instead of adding reps.
Why bother
Both ends of the rectus abdominis move at once. The pelvis rotates up toward the ribs as the knees tuck, and the ribs curl down toward the pelvis as the arms come over. Most floor ab work fixes one end and moves the other; this shortens the muscle from both directions in the same rep.
The extended position is the real work. Arms overhead and legs straight puts your abs at their longest, with a long lever at each end trying to pull your lower back into an arch. Holding that flat-back position on the way out is harder than the tuck itself, and it is the part people skip.
Where it fits
Finisher on any day, two or three times a week, or as part of a bodyweight circuit when no equipment is available. Because you cannot load it, treat rep quality as the progression: slower extensions and a hard pause at the tuck beat adding another twenty sloppy reps.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
Asked and answered
What is the difference between a cocoon and a V-up?
A V-up keeps the legs straight and meets the hands at the toes, so it is mostly a hip-flexor movement with a long lever. A cocoon tucks the knees, which shortens that lever and shifts more of the job onto the abs and the pelvic tilt. If your hip flexors dominate every ab exercise, the cocoon is the better pick.
How many should I be able to do?
Twenty controlled reps with a one-second pause at each end is a solid standard, and far harder than twenty fast ones. Most people who claim 40 are swinging. If you are past that standard, stop adding reps and progress to hanging work or rollouts, which can actually be made heavier.
Can I add weight to make it harder?
Not usefully. Holding a plate overhead breaks the arm swing and ankle weights turn it into a hip-flexor drill. Progress this one through tempo and range instead, and when it stops challenging you, switch exercises rather than trying to load it.
My hip flexors cramp on the extension. What is going on?
The straight-leg, arms-overhead position is the longest lever in the movement and the hip flexors are holding your legs up against all of it. Stop the extension with your heels 20-30 cm off the floor so the flexors never reach end range under that lever, and keep the exhale on the fold so the trunk stays braced instead of the hips taking over. If it still cramps, the abs are not driving the tuck — cut to sets of eight and rebuild the pelvic tilt first.