A special running backpack is a must when running. The last thing you need is a big, bulky, cumbersome bag swinging around as you run. Pick a bag that sits snug into your back. Dr. Nicholas Romanov, creator of the Pose running technique, recommends buying a pack that has a belt so you can tie it around your mid-section to reduce any sway and bounce while running. By keeping the weight around your hips, you're forced to engage your core and glute muscles more than if the bag were swinging around your shoulders.
When running with a backpack, your legs have to deal with extra weight and pressure going through them on every single stride. The temptation will be there to slump forward and use short, shuffling strides. To avoid this, aim to drive down forcefully into the ground on every step. Keep your head looking forward and your chest up, with your shoulder blades pulled back. Brace your core tight and squeeze your glutes as you run.
The last thing you want during a run is the weights in your backpack moving around, digging into your back and causing discomfort. To avoid this, pack the bag as tightly as possible. Rather than just throwing a big weight plate or two in there, use small dumbbells or plates and pack towels or old sweaters around them. This should keep the pack firm and solid and prevent bruising as you run. Alternatively, personal trainer Arnel Ricafranca recommends using books if you don't have weights at hand. As you get fitter and stronger, you can add more weights in the form of extra dumbbells, plates or books.
Running with a weighted pack can be challenging, so start with light weights and short distances and build up gradually. As you become accustomed to the weight and distance, you can either add more weight, run for longer or aim to beat your times. You could even incorporate interval training. Start with a walk while wearing the pack to warm up, slowly increasing your speed over the course of five minutes. Break into a moderate-paced run and maintain this for 90 seconds, then increase your speed, so you're at roughly an eight-out-of-10 effort level. Stay at this pace for 30 seconds, then ease back to a moderate speed and repeat this protocol six to 10 times.