Trail running vests, a style of running rucksack, use stretch fabric and adjustable straps to hug your torso, moving with you rather than against you. Front pockets hold nutrition, your phone and other bits within reach, so you don't need to stop and unclip the pack. Rear compartments fit hydration bladders, spare layers and kit for long days on the hills.
A lightweight running backpack for suits commuters carrying work clothes and a laptop, and minimalist trail runners who just need room for a jacket and snacks. Bigger packs handle multi-day trips or winter runs, when spare layers and safety gear aren't optional. Look for reflective trim and light attachment points if you run before sunrise or after dark.
A short loop on tarmac calls for a slim commuter rucksack; a technical fell route calls for a vest with more storage and a secure fit.
Shop running backpacks and rucksacks at Runners Need and find the right fit for your next run.