Don't really know where I'm going with this, I have no point to make! Going up a few posts to what
@Pogue Mahone posted , that was quite interesting to me regarding advances in sports medicine etc. While players undoubtedly run more than ever they're in a position to do so too being more fit, having nicer pitches, the game not allowing the strength of tackle it once did etc. Then there's the data analysts who don't just monitor match performance but also training performance, trying to pick up on signs that someone might need a small break here and there. I wonder if all that evens itself out to a degree?
Is a less fit player from 20-30 years ago in an age of less medical science/slightly worse pitches/more brutal tackling allowed running himself into the ground putting in less effort or feeling it less than a more fit player doing the same now despite not running as far? I would think it's quite relative but I'm no expert at all, that's just an instinctive answer.