Thirty Kilos of Difference

You turn in for seoi-nage (shoulder throw) with everything you have, they do not move, and then they fall on you. Not a throw, exactly. More like weather. You spend the rest of the round underneath a person, wondering if the problem is your technique or your judgment. It is the second one. Mostly.

Size mismatch randori is not one problem. It is two different problems sharing a mat, and the fix for each player is almost the opposite of the other. The smaller player needs to stop spending strength they do not have. The bigger player needs to start spending control they have not yet learned. Get either job wrong and somebody gets hurt, usually the smaller player first.

Section 01What Thirty Kilos Actually Changes

Thirty kilos is not a number on a scale. On the mat it changes four specific things, and naming them helps because each one has its own answer.

None of this means the smaller player cannot throw the bigger one. Judo was built on exactly that promise. It means the smaller player throws the bigger one with timing, angles, and feet, or does not throw them at all. Muscle was never the plan. It just feels like the plan when you are desperate.

The reverse is also true. A bigger player who only uses weight learns almost nothing from these rounds except that weight works, which they already knew. Their judo stalls while yours gets sharper, and that is a bad trade for both of you over a season.

Section 02The Smaller Player: Win With Feet, Angles, and Timing

Your job is not to move them. Your job is to be moving when they move, and to attack the moment their weight is already going somewhere.

Ashi-waza first. Foot techniques are your main battery against size. Deashi-harai (advanced foot sweep), ko-soto-gari (minor outer reap), ko-uchi-gari (minor inner reap), and sasae-tsurikomi-ashi (propping and drawing ankle throw) all attack the one part of a heavy player that is light: a foot in transit. A foot carrying no weight weighs nothing, whatever the scale says. Build your round around sweeps and small reaps, thrown often, at low cost, while you are fresh enough to move.

Move in arcs, not lines. A heavy partner wins a straight pushing contest every time. They do not win a turning contest as easily. Circle, step off at angles, change direction off their step. Every time they have to turn their mass to follow you, there is a half second where one foot is light. That half second is your whole game.

Grip for information and angles. You will rarely win a grip-strength contest, so do not enter one. Take grips that let you feel their weight shift and steer their shoulder, then let go and re-grip rather than clinging to a losing hold. A sleeve grip you can release is worth more than a lapel grip you are trapped in. Against a much bigger player, gripping inside the sleeve and controlling one arm briefly, then attacking off the reaction, beats a long static tug of war you are going to lose slowly.

Choose throws that fail safely. This is the part pride hates. A full-commitment forward throw under a heavy player who does not go over has one ending, and you are under it. Prefer techniques where a failed attempt still leaves you on your feet, balanced, and outside: ashi-waza, tai-otoshi (body drop) thrown with space rather than contact, and drop techniques only when their weight is already coming forward over you, never as a lever to move still mass. Your throw menu shrinks against size. Accept that early and the round gets safer at once.

Counters are gifts. Take them. A bigger, less experienced player often attacks with honest, heavy, readable throws. Their osoto-gari (major outer reap) coming in is your chance: step off, let the reap pass, and answer with your own sweep or a tani-otoshi (valley drop) style counter where the rules and your club allow it, always controlling their fall rather than dropping them. Counter throwing against weight works because their momentum does your kuzushi for you. Wait for it. Do not manufacture it.

When not to randori. There is a rule worth saying flatly. An inexperienced lightweight should not do free randori with an inexperienced heavyweight. Two beginners, thirty kilos apart, is the most dangerous pairing on the mat, because neither player yet has the control the mismatch demands. The smaller one cannot yet fall out of bad positions. The bigger one cannot yet control a fall, theirs or yours. That pairing belongs in uchikomi (repetition entry practice), nage-komi (throwing practice with a cooperative partner), and grip-and-move drills until at least one of you, ideally the bigger one, has real control. A good coach pairs you deliberately. If yours does not, asking is not weakness. It is the skill.

Section 03The Bigger Player: Your Job Is Control

If you are the heavier player, your randori job is different in kind, not just in degree. You are, for this round, partly responsible for another person's safety. That is not a burden placed on you by etiquette. It is what control means at your size.

Power is a dial, not a switch. Throw at the speed your partner can fall at. A throw your partner cannot take ukemi (receiving/falling technique) from is not a good throw, whatever it scores in your head. If you cannot slow a technique down and still finish it, you do not own that technique yet. Practice owning it at half speed on the big rounds and full speed only with partners who have asked for it and can handle it.

Throw selection is a duty. Avoid techniques that land your mass on your partner: makikomi (wrapping) finishes where you roll over uke, heavy driving finishes that pile forward, and any throw you cannot stop mid-way. Prefer clean turning throws and reaps where your weight stays on your own feet and your partner falls clear of you. When you do throw, hold the sleeve and guide the fall to the end. Letting go at the top so you can watch is how small partners get hurt by big throws that were almost fine.

Your falling responsibility runs both ways. You owe your partner two falls: the one you give and the one you take. When a smaller partner attacks, be an honest uke. Do not plant your weight and make every throw a strength test, and do not do the opposite either, the theatrical dive that teaches them a throw worked when it did not. Give the real reaction a person your size would give to good technique, take the fall cleanly when the technique is right, and land clear of them. Being a heavy uke who falls well is a genuine skill, and smaller partners will teach you more if they are not afraid to attack you.

Win the round smaller. Set yourself a rule that fits the pairing: sweeps before big throws, one big throw per exchange at most, no using body weight to pin a partner flat in standing just because you can. The constraint is the training. Plenty of heavy players reach a decent grade with a game that only works downward in weight. It fails all at once the first time they meet someone their own size who can actually play.

Section 04Pairing Rules Worth Posting on the Wall

That last row matters more than players admit. Control is a fresh player's skill. In the last ten minutes of a hard session, a tired heavyweight should be paired up in size or moved to technical work. Coaches know this. Tired players never volunteer it. Volunteer it.

Section 05Goal-Switching: The Real Skill

The deepest fix is not a technique. It is changing what a good round means when the scales are uneven.

For the smaller player, a good round stops meaning "I threw them" and starts meaning "I attacked their feet fifteen times, I was never underneath them, I countered once cleanly, and I finished able to play again." That round built your judo. The round where you strained into three dead forward throws and got landed on built nothing except a story.

For the bigger player, a good round stops meaning "I won" and starts meaning "Every throw I made was controlled, my partner attacked me without fear, my sweeps did most of my work, and nobody checked their ribs afterward." If you need a harder test of your judo, find it against your own size, where the test is honest.

Clubs that say this out loud get better mismatch rounds within weeks, because players stop grading themselves on the wrong scoreboard. The techniques follow the goals. They always do.

Section 06Where It Goes Wrong

The smaller player treats it as a strength referendum. Every failed muscled throw is framed as proof the gap is unfair, when the actual failure was selection. You brought a lever to a timing fight.

The bigger player apologizes instead of adjusting. Saying sorry after every hard landing while changing nothing is not control. Control is slower entries, cleaner finishes, and held sleeves. Change the throwing, not the commentary.

Both players go quiet and grip-fight for four minutes. Fear disguised as tactics. The smaller one is afraid to attack, the bigger one is afraid to hurt them, and nobody does any judo. The fix is a constrained round: ashi-waza only, or attacks off movement only, agreed before hajime (begin).

The coach uses the small player as a durability test for the big one. It happens in tough rooms and it is wrong. A partner is not equipment. If the bigger player needs resistance, that resistance should come from size, experience, or a drill designed for it, never from a smaller beginner's body.

Nobody says stop. Either player can end a pairing that has gone past control, at any point, without a reason that would satisfy a court. Saying "I need a different partner for this round" is a complete sentence in a healthy dojo.

Section 07The Companion Guide

This article gives you the knowledge. The companion guide turns it into training. The Size-Mismatch Randori Playbook sets out the pairing matrix your coach can run the room from, the smaller player's ashi-waza attack plans by grip, the bigger player's control standards with a throw-by-throw permission table, and a full set of constrained randori formats that make uneven rounds productive instead of dangerous. It includes readiness checklists for promoting a pairing from drills to free randori, fall-control progressions for heavy players learning to throw light, and a session log for tracking pairings, formats, and incidents honestly over a season.

It is made for the small player who dreads the big rounds, for the big player who knows they are somebody's dread, and for the coach pairing a whole room on a busy night.