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Throws
Major outer reap (o-soto-gari)
Names by art: Judo: o-soto-gari 大外刈 · Sumo: sotogake 外掛け (outside leg trip, related) · Wrestling: outside trip / reap · BJJ: osoto-gari
O-soto-gari is one of the first throws taught in judo and one of the most studied. It looks like a leg sweep, but a 2026 study found that what separates black belts from white belts is the leg that stays on the floor: the ankle of the support leg drives the rotation of the whole body. It is also the throw that produced very high head accelerations in crash-test dummies — which is why it is taught only after ukemi.
- v
- uke’s head moves backwards and down
- CM
- uke’s centre of mass, now behind the heel
Step by step
- Grip: sleeve with one hand, lapel or collar with the other.
- Kuzushi (breaking balance): pull the sleeve down towards your hip and push the lapel up and back, so uke’s weight goes onto one heel.
- Step in deep beside uke with your support leg, toes pointing forwards, knee slightly bent — your chest close to uke’s chest.
- Swing the reaping leg past uke’s leg and reap it backwards with the back of your thigh against the back of uke’s thigh, toes pointed.
- At the same time push off the floor with the ball of the support foot (ankle extension) and bring your head and chest forwards and down, so your body rotates as one piece.
- Keep the sleeve grip and pull it up during the fall so uke can breakfall; never fall on top of uke in practice.
Common errors
- Reaping before kuzushi: uke’s weight is still spread over both feet and the leg does not move.
- Standing too far away, so only the leg works and you lean back yourself — the classic counter (o-soto-gaeshi).
- Support foot flat and passive: the study points to the ankle push as the difference between levels (Liu et al., 2026).
- Letting go of the sleeve: uke cannot control the fall and the head can hit the mat.
Biomechanics: what the body does
Main muscles
Support leg: calf muscles (gastrocnemius, soleus) for the ankle push, quadriceps and gluteus maximus for stability. Reaping leg: hamstrings and gluteus maximus extend the hip backwards. Trunk and arms: latissimus dorsi and pectorals pull and push the grips.
Joints
Support ankle in plantar flexion during the throw; reaping hip in extension, knee almost straight; trunk flexing forwards.
Kinetic chain
In Liu et al., 2026, black belts produced more angular impulse (more whole-body rotation) than white belts. The extra rotation came from the support leg: higher upward ground force and ankle plantar-flexion moment in the second half of the throw. The reap and the forward-down movement of the trunk are one rotation, like a see-saw around the support foot.
Base and balance
Uke falls because the centre of mass is moved behind the heel (outside the base) and the leg that could step back to recover is removed. Tori stays balanced on one leg only if the support foot is close to uke and under tori’s own centre of mass.
Physics and maths
What studies measured
- Liu et al., 2026: 20 male judoka (10 black, 10 white belts), motion capture at 250 Hz and a force plate under the support leg at 1000 Hz. Black belts had greater angular impulse (p = 0.043) and a much higher external moment from the support-leg ground force between 50% and 65% of the movement (p < 0.001). Upward ground force, ankle plantar-flexion moment and ankle power were also higher in black belts (in the 60–84%, 56–88% and 59–64% windows).
- Murayama et al., 2014: a dummy without ukemi thrown with o-soto-gari reached 4284.2–5525.9 rad/s² of rotational and 64.3–87.2 g of linear head acceleration; with o-uchi-gari, 1708.0–2104.1 rad/s² and 120.2–149.4 g.
- Murayama et al., 2020: an expert uke performing ukemi when thrown with o-soto-gari: 10.3 ± 1.6 g and 679.4 ± 173.6 rad/s².
Our calculation from cited data
From Murayama et al., 2014: the dummy’s rotational head acceleration in o-soto-gari was about 2.0 to 3.2 times that in o-uchi-gari (4284.2 ÷ 2104.1 ≈ 2.0; 5525.9 ÷ 1708.0 ≈ 3.2), even though o-uchi-gari gave the higher linear acceleration. O-soto-gari makes the head swing backwards; o-uchi-gari makes it hit more directly.
Rotational acceleration is closely linked to the acute subdural haematoma, the most common severe head injury in judo, as Murayama et al., 2014 explains. That is the physical reason behind the rule “ukemi first”.
Numbers come from the cited studies, with their sample and conditions. They describe those athletes in that laboratory, not every practitioner.
Comparison across arts
Leg reaps and trips from the outside exist in almost every wrestling tradition; the grips and the rules change the details.
| Art | Grip and form | What changes |
|---|---|---|
| Judo | Sleeve and lapel of the judogi; big rotational reap | Scores by throwing onto the back; ukemi is compulsory before learning it |
| Sumo | Mawashi (belt) grips; sotogake hooks the leg from outside | Any part of the body touching the ground except the soles loses; no falling technique is needed to score |
| Wrestling | No jacket: over-under, head and arm, or body lock; outside trip | Follows uke to the mat to pin; the trip is often combined with a body lock |
Safety
- Only practise with partners who already master the back breakfall (ushiro ukemi).
- Keep the sleeve and pull it up during the fall; never drop your body weight onto uke.
- Start from kneeling or low height and from walking speed; full-speed throws come last.
- Murayama et al., 2014: an under-mat did not reduce rotational head acceleration — mats do not replace ukemi.
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.
Related
Judo Jujutsu Sambo Sumo Wrestling Brazilian Jiu-Jitsu
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) Breakfalls (ukemi) Shoulder throw (seoi-nage) Rear naked choke (mata-leão / hadaka-jime) Cross armlock (juji-gatame / armbar)
Sources
- L. Liu, T. Deguchi, M. Shiokawa, K. Hamaguchi & M. Shinya (2026). Kinetics of the lower limb during the rotational movement of the body in osoto-gari: a comparison between black belt and white belt judokas. Sports Biomechanics 25(8), 1286–1302. DOI 10.1080/14763141.2026.2636943
- 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
- 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
- Jigoro Kano (1986). Kodokan Judo. Kodansha International. ISBN 9780870116810
- Toshiro Daigo (2005). Kodokan Judo Throwing Techniques. Kodansha International. ISBN 9784770023308
Cite / use this content
You may quote short excerpts with a visible link to this page. Suggested citation:
Wabukan (2026). “Major outer reap (o-soto-gari)”. https://wabukan.com/manual/o-soto-gari (accessed 2026-10-30).
Full rules, ready-made link code and press kit → · Updated: 2026-10-30