Why do you never hear about the paleo workout? Think about how Grug would've lived back in the day. He hunted animals with his tribe by running them down. Now you might imagine a short burst of speed, spring up to the animal, stab it with a spear, but no. Because humans can sweat they would've actually jogged after the animals for two or three hours, exhausting it. The rest of the time they would've just walked around. The heaviest thing they'd ever haul is maybe an animal carcass and a couple of rocks here and there.