[Tomsdad]

In GURPS terms Knockdown and Knockback are very different things

Knockdown is when you take a bad enough injury that causes your body to react by being unable to support itself.

This is a threat with any Major wound, Vitals, Eyes, Face and Skull hits (and made more likely if its a Major wound to those locations).

This is a physiological reaction (hence it being based on HT) and not much to do with staying stable and upright while grappling/wrestling. Thus I wouldn't give any direct benefit from Sumo or Judo to that roll. Although I'd happily allow experienced Judo/Sumo wrestlers buy HT as part of the overall benefits of being a trained and conditioned fighter. I.e they can "take a punch/hit"


Knock back is very different and I'd certainly allow Sumo to be used in the same way as Judo.

One other indirect way I think Sumo is likely to aid in resisting knockback gets into how GURPS does Mass. Sumo style wrestling tends to encourage a big heavy build. Now in it's simplest form that might just be high ST, well high ST allow you resist knockback by increasing the knockback threshold. You also get direct bonuses to this threshold for Fat and V.Fat build types

So for example a ST12 sumo wrestler who's V.Fat has a knockback threshold 12+3-2 = 13 if he's trying to two handed shove an a equally statted sumo wrestler and say he qualified for the +2 skill damage bonus on a shove so (1d-1+2)*2 he's only going to inflict knock back on a 6!


However a more nuanced approach might be to consider resisting knockback is more a matter of mass than ST, and HP is a better match for mass than ST.
I certainly have no issue with modelling Sumo wrestlers with extra HP to account for extra body mass, as opposed to just increasing ST.
But then the idea of sumo wrestlers who are just strong in general doesn't really faze me either, so it's really just a matter of precise preference and both are good!

If you use Technical Grappling while it has "Strength as a Proxy for Mass" i.e. it directly uses ST and doesn't use HP (although as it says HP is based off ST) it does also have the optional "Grappling Weight Modifier" rules for mass based moves that directly links to weight/mass, and make it harder to shove heavier opponents around. Meaning that heavy sumo wrestlers will indeed be harder to shove or force a posture change on.


A similar situation in terms of falling down is Slams. With Slams GURPS invokes mass but this time with HP! Which indirectly favours that big heavy Sumo wrestler. They also get a skill bonus to damage when they make a slam. I don't think it would be too wild a house rule to give that skill based bonus to damage when being slammed as well*.

(Sumo matches that involve slams get a bit lopsided if you don't, as the sumo wrestler who's slams get's a significant damage bonus and thus advantage in determining the likely end result over the sumo wrestler receiving the slam).

You could also allow the sumo skill to be used for the DX roll to stay on your feet in a slam (although that might end up double dipping if you also allow the bonus to damage on both sides of a slam as per above)



*in rugby I've bounced off my fair share of props!