Although often referred to interchangeably, mud runs and obstacle races are not strictly speaking the same thing - a mud run does not necessarily involve obstacles while an OCR could be held in a city centre! Having said that, the majority of mud runs and obstacle races in the UK will feature both.
Mud runs are all about experiencing something that most people don't get in their day-to-day lives - the primal thrill of crashing through woodland, bogs and rivers. While cross-country and trail runs are also off-road, only mud runs aim their course directly at the muddiest areas. If you don't cross the finish line covered head-to-toe in dirt, something has gone wrong!
Although some people race mud runs, the majority of entrants are there for a social experience and sign up as a team, enjoying the camaraderie of helping each other through muddy bogs and over obstacles. Expect to give a helping hand to someone you've never met and laugh about the ridiculousness of the situation together. It's not difficult when you've got twigs in your hair and a hill to climb.
Mud runs are year-round events, with many taking place in the autumn to ensure maximum muddiness, though some die-hard events occur in the winter when the leading competitors must break the ice on a bog to wade through (as we've experienced). Whichever season you go for, we'd recommend approaching a mud run in the same way: with a healthy appetite for the absurd!