I think with 'tough' there is always going to be an element of 'strong' but its the type of strong that really matters.
For example before settling down and having a family I would quite often just out for a 'walk' with my dog and come back 3-4 days later having walked 100 or so miles. Like BH I'm no Mr Muscle to look at but I'm strong enough and tough enough to carry a pack with everything I need to be self sufficient for several days in all kinds of weather without quitting. 😎