The best way to train for carrying your heavy pack is to do this at least 3 times a week. It will be strange, and some neighbors may start calling the police if you are toting a backpack with guns, axe, and knife attached on a regular basis. Here is how to get started without looking like that weird prepper creeping in the neighborhood.
Start light but walk around your neighborhood at 4 miles per hour with a pack on. Put in 10 pounds of weight. You can get weight pouches either at a dive shop (they will carry varying sized weights) or any sporting goods store that carries a weight vest (usually 1 pound pouches). If you cannot walk with a 10-pound pack at 4 miles an hour, try it with just the backpack with some clothes in it. Then every time you go out for the brisk walk, add 1 pound of weight in the pack until you get to the desired weight (the weight of your actual bag filled with all the items).
Other options are to get a body armor vest and fill it with a workout plate inserted only in the rear panel and run to get started, and/or get a 45 lb weight vest and start filling it 2 pounds at a time starting at 10 lbs and run. Running with a fully weighted body armor vest or a 45 lb fully loaded weight vest is an amazing training method for both strength, power, and endurance. I also climb indoors with a 45 lb fully loaded weight vest to increase my strength, power, and endurance.
I hope you don’t have a 70 lb pack because that is going to be rough walking 4 miles an hour with that much weight.
