I'm going to tell you how I'm preparing physically.
On weekdays, I'm training a lot on my bike, in the gym and motocross.
When I train motocross I do half-hour sessions to get a good physique and to not get tired when I go raod racing.
With the bike there are days that I go out with the mountain and others on the road and, in the gym, I work on my balance and my physique.
On weekends, I speed up with a PreMoto4 that I bought to train because it is better than the 450 to train the technique.