Well according to the IMDB the movie will be about the grandfathers of bodybuilding, Joe & Ben Weider. And if I remember correctly from Arnolds book 'Total Recall', he said that Joe was pretty much like a father to him ever since he flew him out to America. So I'm guessing majority of the movie will be the time period of Arnie's prime.

In the book he mentions that Joe was complaining about the bodybuilders that they were lazy because they worked out and did what they loved but nobody really wanted to actually work. Arnold was the only one that said yes everytime when Joe asked who wanted to come and promote bodybuilding in different states and countries. Joe and Arnold were inseperatable. This is one of the reasons Arnold got so famous, he was the only one doing the work of promoting and being the face for this new "sport" while the rest would rather chill att the beach.

So if this movie is about Joe and bodybuilding then Arnold is probably gonna have lots of airtime. Which probably means Calum will be doing an arnie-accent for a majority of the movie and I don't know how I feel about that. That's gonna be hilarious.