To echo some of the points from the aurora book, I think that the human body is really well optimised for 1G environments. We know that there are issues in zero gravity. As you adapt to 2G, you may well get stronger but the stress and strains may have a severe effect on health, life expectancy. Hate to think about the effects on your blood pressure etc

Your great grand kids might eventually cope.

That's actually seen in anime. In Dragon Ball Z, Goku trained in 100 G. I remember thinking it was clever. It reminded me of Spain national football team training for some weeks in La Paz previous to Mexico World Cup in 1986. The idea is enduring harder conditions (> altitude -> less oxygen) to overcompensate.

This is a key assumption of the classic book (and box office bomb movie adaption) https://en.wikipedia.org/wiki/A_Princess_of_Mars

would that be similar to weari nb a backpack having weight same to your body?

Not too similar, imagine all the liquids in your body while running at 2g.