You should think about several things when working with heavy stuff.
One is caravan animals.
When delivering heavy stuff caravan animals can carry heavy stuff and running fast is easy for them.
Next is when you run and what is easy or hard.
It is faster to deliver if you run. Frost (winter) is hard because it is too cold. Green (summer) is hard because it is too hot spring is probably the best.
Finally the last reason if you are big or fat.
If you are big or fat you could lose weight and get stronger from carrying heavy stuff.
How do you work with heavy stuff?