Inside the office of the New York City startup that's convinced 2 million people to crawl through mud

When Will Dean proposed a teamwork-based challenge where participants have to trudge through mud and obstacles involving barbed wire, judges at the Harvard Business School competition were skeptical of his idea.

Who on earth would voluntarily put themselves through so much grueling pain, nevermind pay to do it?

But a year later, the first Tough Mudder event took place at Bear Creek Mountain Resort, Pennsylvania.

Seven years later, Tough Mudder has become a symbol of the ultimate endurance event, with over 2 million participants to date.

Unlike marathons, triathlons, or Ironman competitions, Tough Mudder is not a race. Participants are not timed, and there is no winner or loser. Instead, the emphasis is on teamwork and camaraderie.

Past challenges have taken place in North America, Australia, the UK, Ireland, and Germany, and the company plans to add China, Indonesia, and the United Arab Emirates to the list.

Business Insider recently visited Tough Mudder's New York headquarters for a glimpse of what it's like to work for a company that strives to push people past their mental and physical limits.