What's rucking?

Here's a clue: it's the best fitness hack ever, strength training for people who don't want to join a gym

As mentioned in my How to Change your Health Fate post (the title of which I think I may change to How Not To Die!), strength training is vital as you get older — very much a case of use it, or lose it. But, does this have to mean expensive gym memberships and sweaty weight rooms full of posturing Schwarzenegger wannabes?