Falls

Breakfalls (ukemi)

Names by art: Judo: ukemi 受身 · ushiro / yoko / mae-mawari ukemi · Aikido: ukemi 受身 · BJJ: breakfall · Wrestling: fall / sprawl recovery

Ukemi is the art of being thrown. In judo it is taught before any throw, and for a good reason: being thrown is the most common cause of injury in judo, and the rare severe injuries involve the head and spine. Laboratory measurements show what a correct breakfall changes.

⚠ Train with an instructor. Learn and practise this technique only under a qualified instructor, on a suitable surface and with a cooperative partner. This page explains; it does not replace a teacher.

Diagram 1. Back breakfall: chin tucked, back rounded, the arm slaps the mat at about 45° from the body. The gap between head and mat (blue) is the goal.

F: arm and back absorb the landing
≠ 0: head never touches the mat
45°: arm angle from the body

Step by step

Start low: sitting, then squatting, then standing. Height comes last.
Tuck the chin to the chest and keep looking at your belt for the whole fall.
Round the back so you roll onto it from the hips up to the shoulders, not flat.
Slap the mat with the whole arm and palm, at about 45° from the body, at the same moment the back lands; the arm stays relaxed and bounces.
In side falls, land on the side of the body with the lower leg bent and the feet apart, not crossed.
For forward rolls, the roll runs diagonally from one shoulder to the opposite hip; the head never touches the mat.

Common errors

Head falling back: the most dangerous error — the head hits the mat.
Putting a straight arm or a hand out to stop the fall: wrist, elbow and collarbone take the impact.
Landing flat on the back without rolling.
Slapping too late or too far from the body, so the arm does not share the load.
Crossing the legs in a side fall, so the knees knock together.

Biomechanics: what the body does

Main muscles

Neck flexors (sternocleidomastoid, deep neck flexors) hold the chin down; abdominals round the trunk; latissimus dorsi and triceps drive the slap; hip flexors keep the legs up.

Joints

Cervical spine in flexion, thoracic and lumbar spine rounded; shoulder in abduction with the elbow almost straight but relaxed; hips flexed.

Kinetic chain

Here the chain runs in reverse: instead of building speed, the body spends it. Rolling turns a single hard stop into a longer, progressive contact, and the arm takes part of the load before the trunk.

Base and balance

In a fall there is no base; the goal is to choose the contact surface — large and soft (back, side, arm) instead of small and hard (head, elbow, wrist).

Physics and maths

F̄ = Δp / Δt

For the same fall (same change in momentum), a longer contact time Δt means a lower average force.

P = F / A

Pressure: spreading the force over a large area A (back and arm) lowers the pressure on any single point.

What studies measured

Murayama et al., 2020: one expert threw another expert with osoto-gari four times; a sensor on uke’s forehead. Peak head acceleration was 10.3 ± 1.6 g and peak rotational acceleration 679.4 ± 173.6 rad/s², significantly lower than for a POLAR dummy without ukemi whose head hit the tatami.
Murayama et al., 2014: an expert threw a dummy (no ukemi). Osoto-gari: 64.3–87.2 g and 4284.2–5525.9 rad/s². Ouchi-gari: 120.2–149.4 g and 1708.0–2104.1 rad/s². An extra under-mat did not reduce rotational acceleration.
Pocecco et al., 2013: systematic review — about 11–12% injury risk at the 2008 and 2012 Olympics; being thrown was the most common injury mechanism; severe injuries were rare and usually affected the brain and spine.

Our calculation from cited data
Dividing the dummy values for osoto-gari (Murayama et al., 2014) by the ukemi values (Murayama et al., 2020): about 6.2 to 8.5 times higher linear acceleration (64.3–87.2 g vs 10.3 g) and about 6.3 to 8.1 times higher rotational acceleration (4284–5526 vs 679 rad/s²). The two studies used different set-ups, so treat this only as an order of magnitude.

The under-mat result matters: a softer floor did not reduce rotational head acceleration in the dummy (Murayama et al., 2014). Technique — keeping the head off the mat — is what made the difference.

Diagram 2. Peak head acceleration in osoto-gari: an expert performing ukemi (Murayama et al., 2020) versus a crash-test dummy without ukemi, range of trials (Murayama et al., 2014). Different set-ups — see the note in the text.

g: multiples of gravity
ATD: anthropomorphic test device (dummy)

Numbers come from the cited studies, with their sample and conditions. They describe those athletes in that laboratory, not every practitioner.

Comparison across arts

Every grappling art teaches falling, but each prepares for different situations.

Art	Main falls	Emphasis
Judo	Ushiro, yoko, mae and mae-mawari ukemi	Slapping breakfalls from high-amplitude throws; taught before throwing
Aikido	Rolling ukemi forwards and backwards; high falls (breakfalls) at advanced level	Continuous rolling, getting back up at once; ukemi is an equal half of practice
BJJ	Back and side breakfalls, technical stand-up	Landing ready to fight from the ground

Safety

Learn ukemi on proper mats with a qualified instructor before being thrown from standing.
Never practise falls on hard floors or with throws you have not learned to receive.
Murayama et al., 2014 recommends restricting throwing to people who can already perform ukemi.
Any head contact, dizziness or headache after a fall: stop training and get checked.

Train with an instructor. Learn and practise this technique only under a qualified instructor, on a suitable surface and with a cooperative partner. This page explains; it does not replace a teacher.

Judo Aikido Brazilian Jiu-Jitsu Jujutsu Sambo Wrestling

Straight punch (reverse punch / cross) Front kick (mae-geri / teep / ap chagi) Roundhouse kick (mawashi-geri / dollyo chagi / Thai kick) Side kick (yoko-geri / yop chagi) Major outer reap (o-soto-gari) Shoulder throw (seoi-nage) Rear naked choke (mata-leão / hadaka-jime) Cross armlock (juji-gatame / armbar)

Sports science bibliography Code of Honour Glossary

Sources

Haruo Murayama et al. (2020). Ukemi technique prevents the elevation of head acceleration of a person thrown by the judo technique ‘osoto-gari’. Neurologia medico-chirurgica 60(6), 307–312. DOI 10.2176/nmc.oa.2020-0043
Haruo Murayama et al. (2014). Rotational acceleration during head impact resulting from different judo throwing techniques. Neurologia medico-chirurgica 54(5), 374–378. DOI 10.2176/nmc.oa.2013-0227
Elena Pocecco et al. (2013). Injuries in judo: a systematic literature review including suggestions for prevention. British Journal of Sports Medicine 47(18), 1139–1143. DOI 10.1136/bjsports-2013-092886
Jigoro Kano (1986). Kodokan Judo. Kodansha International. ISBN 9780870116810

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