Quarto
Unknown Enemy
In your typical fragmentation grenade, it's not the explosion that kills you - it's the flying fragments of the grenade casing that are propelled outwards by the explosion. I would figure that if you're sitting on top of a grenade, most of the casing would probably stay intact because you're applying pressure onto it. Of course, this would only make the explosion stronger in the directions where your body is not directly on top of the grenade, but that still means that the bulk of the force would go sideways, not upwards where you are. So, all in all, the grenade would deal less damage than if it exploded a metre or two away from you. But that's just what my very limited knowledge of granades and physics suggests - I'm sure one of the people with actual military service (we seem to have a few here) would be able to better explain it.