Exhaustion VS Adrenaline

You've been running for an hour.  You've been beat up, shot at, and chased.  You're out of breath, but the imminent danger behind you doesn't let you stop.  You keep going, dodging this way and that, barely recognizing that your legs hurt and your lungs sting.  You cough up some blood.  That's probably not good...

The best part about RPGs is that we can be as realistic or as cinematic as we want.  And that perfect mix of action-movie-badass and realistic human limits is something I want to explore in my current project Hostargo.  The idea of "exhaustion" levels has always intrigued me, but the games I've played don't integrate it very nicely into the rest of their mechanics.  For example, in D&D it's tacked on as its own set of rules, and in Shadowrun your "stun" hit points don't function much differently than your actual "health" hit points.

Currently, I have a system where your stats lower as you take damage.  For example, if hit by a sword, your "Grit" may be reduced by two.  In the setting, there is magical healing, as well as other various ways to recover health, so I'm looking for a way to simulate characters getting "worn down".  Enter Exhaustion, a value that starts at zero and increases as you:

• Physically over-exert yourself
• Fail at casting magic (in this case the spell doesn't fail, you instead gain an exhaustion point)
• Go long periods of time without sleep
• Contract a sickness or disease
• Spend a long time thinking about a stressful problem
• Over-eat?

For each level of exhaustion,
your maximum stats are temporarily lowered.
This means that healing, through magic or otherwise, cannot recover your health (stats) past their maximum level, minus your exhaustion level.

This mechanic ensures that, as an action game with magical healing, conflicts in Hostargo will eventually come to an end, even if it's a hostage stand-off that lasts long into the night.

Normally in Hostargo, and assuming you're at full health, as soon you gain an exhaustion point, your stats would immediately decrease due to their new lowered maximum. But in the heat of battle, adrenaline pumps through our veins and can keep us going until the point of collapse.  So while in an "action scene", any exhaustion gained would not immediately reduce your stats.  Instead, exhaustion will only apply to being healed: you couldn't go past your maximum minus your level of exhaustion.

Side note: Exhaustion will be fully healed after a short rest, a bit of food, and some water.

I love the scenes in movies where the hero fights to near death, but powers through their pain in order to win. But once that delicious adrenaline is gone... they collapse, usually waking up hours later somewhere safe and surrounded by loved ones.  Epic.

Let me know what you think of the mechanic! Is it simple? Does it work?  Is this topic even worth considering having rules for?