Learn cut loose in bouldering: release both feet from the wall, absorb the swing and place the feet back with control. With milestones and safety rules.
Cut loose means: you let both feet come off the wall, your body swings out, and afterwards you place the feet back under control. The honest answer to "Isn't that just a mistake?": sometimes yes, but as a technique it is intentional. Cut loose is the controlled version of what happens to you when a foot slips.
Biomechanics calls the problem behind it the "barn door": when the contact points are not in balance, the body swings away from the wall like an opening barn door [1]. In a cut loose you allow that movement and absorb it deliberately. The international federation IFSC also lists the toe hook, hooking the toe on a hold, expressly as a means against swinging backwards [2]. Cut loose does not mean your feet are gone by accident; it means you bring them back after the swing.
Expect to learn the basic sequence in a few sessions on a slight overhang, but control during bigger swings takes noticeably longer (an experience value, not a measurement).
Entry criteria (practice standard):
Hang with both hands on jugs, both feet on footholds. Lift one foot slightly and put it back. Then the other. This is the preliminary stage.
Milestone: You lift each foot three times and place it back precisely without the body swinging.
Release both feet from the wall for two seconds. Tighten your abs and pull your knees up slightly. The body swings, the arms stay long. Place the feet back on the same holds.
Milestone: You hang three times for two seconds with both feet free and come back without a failed attempt.
The swing is the real problem. Let it happen, brake it with body tension and legs instead of cramping against it. The technique when replacing the feet decides whether you land cleanly or slam into the wall.
Milestone: You place the feet softly three times without the toes hitting the wall hard.
Now a hand move comes in: while the feet are free, you reach for the next hold. Then you place the feet on new footholds. Plan the target beforehand so your eyes do not search only afterwards.
Milestone: You climb a short boulder with two cut looses without stopping in between.
Build the technique into an easy to medium boulder. Choose the spot yourself and decide whether you need the cut loose or whether a foot alternative is enough.
Milestone: You use a cut loose intentionally and under control, not as an emergency fix.
In a cut loose you briefly hang from your hands only, which loads fingers and shoulders. And the swing back can slam the feet into the wall: an ACL concept paper for climbers names eccentric landing mechanics and pendulum swings into the wall as climbing-specific demands [3], described there for lead climbing. In bouldering the mechanism is similar, but the transfer is not proven. According to my search there are no figures on the cut loose itself. In general, falls in bouldering are mostly involuntary: in a survey of 245 injured climbers it was 85%, 62% of the falls included a rotation, 74% landed feet first, and 67% of the injuries affected the lower extremity [4]. In a cohort of 507 boulderers, lower extremity injuries were more often severe and more often caused by falls and jumping off [5]. Start at low height and keep the landing zone clear. This guide explains and motivates but does not replace supervised training.
Do the breath check: breathe out deliberately as you swing out and breathe in as you place the feet back. Holding your breath stiffens the body, and then it cannot absorb the swing. This is practical experience and not proven.
In a cut loose you release both feet from the wall, the body swings out and you place the feet back on footholds. It happens when foot contact is lost, and it is used deliberately as a technique when a move briefly costs foot contact.
Start on a slight overhang with big holds. First lift single feet, then both for two seconds, and absorb the swing with abs and legs. Place the feet softly. Only after that do you add a hand move.
You cannot stop it completely, but you can limit it. The international federation IFSC lists the toe hook expressly as a means against swinging backwards [2]. Body tension and softly placed feet help as well.
It has its own risk: hanging from the hands and swinging back into the wall. There are no figures on the cut loose itself. In general, 67% of the injuries in a survey affected the lower extremity [4].
Pocket: Few Fingers, Big Load, a Clear Build-Up