Some 16,000 competitors descended on Dalkeith Park over the weekend to push their mental and physical limits in the gruelling SAS-designed challenge.
The the endurance test pushes runners to their mental and physical limits as they sprint, duck, crawl, swim and leap their way along a brutal obstacle course.
Unlike traditional running events, teamwork is the name of the game. Contestants are expected to help their fellow "mudders" run through electric wires, climb walls and plunge into ice-cold pools.
The challenge, launched in 2010, is now held in more than 60 countries worldwide.