How much of a strength boost is my magic drug giving someone if it makes them liable to seriously injure themselves with their own attacks?

Question

In my setting there are various types of magical potions that provide a variety of effects. One of these is a highly potent but dangerous performance enhancer most commonly known by the name of "redknuckle". And one of the many reasons it is so dangerous is because it temporarily enhances the drinker's physical strength, but crucially, not their durability, and it in fact enhances their physical capabilities beyond what their bodies can realistically withstand. People who use redknuckle before getting into fights have a tendency to break their own bones and tear their own skin, hence the name of the potion.

Now, most of the people who use this potion are not mundane mortal humans, so the comparison isn't perfect. However, assuming that the people who use this potion, even if they're stronger and tougher than humans, have a comparable strength-to-durability ratio to that of humans, I'm trying to get a sense of what the minimum effect of this potion would have to be before the potion would get a reputation of its drinkers seriously injuring themselves with their own power.

How much stronger would redknuckle have to make a human before their own punches and kicks, when directed against another human opponent, would be liable to cause them to break their own bones and tear their own skin?

Answer 1

Humans can already break their own bones fighting.

Your potion is still useful though, trained fighters aim for areas that will not break their hands striking or legs kicking. So the range of fight stopping strikes would increase. You'd be able to end a fight with a front kick to a conditioned stomach or even a kick to the thigh (or even a punch to the thigh).

Quite apart from grappling, just because you have the strength doesn't mean you use it all. I playfight with my sons and have never hurt them.

Normally dangerous strikes like one to the solar plexus may well kill your opponent. A strike to the neck might paralyze them.

So double or more the strength would be fine so long as your fighter knows what he's doing. Using less than full strength also gives you better strike control in many cases.

Answer 2

Adrenalin

Your drug seems much like Adrenalin, though a bit more powerful. People full with Adrenalin can do amazing feats, often looking outside the realm of possibility. This is because the body normally limits itself to prevent damage. If you're in any normal situation it would be bad to lift something super heavy for example. If you wouldn't limit yourself, the time to recover for your body can be days, weeks, months or even a permanent damage. Pump someone full with adrenalin and suddenly these limits are removed, which goes hand in hand with increased pain thresholds. The reason being that some damage to the body is be preferable over death.

If for whatever reason you are pumped full of adrenalin you can easily tear tendons and bruise muscles. If you punch, for example, a wall without adrenalin you can already break bones, so with adrenalin this is even more risky.

How much stronger would redknuckle have to make a human before their own punches and kicks, when directed against another human opponent, would be liable to cause them to break their own bones and tear their own skin?

To go back to your question. Your answer is that it doesn't need to improve their strength at all to harm themselves badly in a fight. From a few quick searches I saw references that there's about a 30% increase in strength with adrenalin. The example was lifting power, where someone normally lifting 100kg at max strength could lift 130 with adrenalin, though I would check out the actual sources yourself. The maximum of adrenalin (30%) seems a 'safe' maximum increase for the drug to not absolutely tear yourself apart, while still giving plenty of strength. That is of course not addressing more adrenalin someone might get in a fight.