When to Wear a Weight Vest
Another reason runners may run with weight is because their goal is to lose weight. I generally don't recommend hand-lifting heavy objects in this situation. Carrying dumbbells or lifting weights while running can cause you to alter your gait, which can lead to injury. A weight vest that is closer to your center of gravity and more evenly distributed is a safer approach. Even so, I still recommend separating running and strength training so you can target the right muscle groups with proper form and prevent injury.
If you're planning a big self-reliance adventure, you'll definitely want to be strong enough to carry all your gear, no matter how many hours or days you plan to be there. If you can't train with a backpack on, a weight vest is a great option. Choose a vest that's commensurate with the weight you'll be carrying in the race, and practice how you plan to move in it, which could be a combination of hiking and running. That way, your body gets used to how it actually moves with the extra weight on.
All in all, training for the specificity of your activities and goals is the most important consideration. Excessive running may not be necessary for you, and if it is, you'll want to do it as safely as possible.
How to choose weight-bearing running equipment
Road, trail and track runs all have different distances, equipment requirements and terrain. It's important to train specifically for your activity or adventure. I'm a trail runner specializing in long-distance mountain races, so I often have a lot of gear to carry for hours. In this case, I train with a hydration bag filled with what I need on race day to accommodate the weight my body needs to carry comfortably.
This is very different from a road marathon, where you may only need gels and a water bottle. You'll still want to practice this in your workouts, but in this case, there's no need to carry an extra 5-10 pounds during your run. My favorite backpacks, hydration vests, and totes are from the brand Big Trick r Aspire. They have everything from straps to race vests to larger packs for all-day adventures.