STALKER actually did this pretty well if I remember correctly. While you had breakpoints where the character would suffer extreme exhaustion, allowing him to sprint for only a few meters or where he could not move at all, there was also a system of increased stamina loss the more you carried. So while the breakpoint for extreme stamina loss was around, say, 50 kg, there was already a noticeable difference between 10 and 40 kg. Still, even that could do with improvement.