CrossFit Games director Dave Castro has revealed that a gruelling opening day of the 2018 competition will be capped by a 42,195-metre marathon row.

Castro made the announcement at the athletes’ dinner on Monday night, with many left speechless ahead of Wednesday, when the Games kick off at the Alliant Energy Centre in Madison, Wisconsin in the United States.

“I told you Wednesday would be the hardest day in the history of the CrossFit Games, I did not lie. You guys will row 42,000 metres,” Castro said to audible gasps.

Details of events at the Games, which take place from August 1-5, are traditionally held secret by organisers CrossFit HQ, sometimes until weeks, days or even just minutes before the athletes compete.

The marathon row will be the fourth individual event on Wednesday. The time cap is four hours, with Castro expecting the best athletes to complete it in just over three hours.

Individual Event 4 will take place in the Coliseum, with 80 rowers all rowing at the same time. “Enjoy your dinner,” Castro added after his announcement, smiling, to laughter.

Earlier on Monday, Castro revealed that the opening event of the competition will be a criterium bike race.

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Details had already been released for Individual Event 2, where each athlete will have one set of rings and will complete 30 muscle-ups before crossing the finish line.

Workout No 3 for individual athletes on the opening day will be the heavy weight-pushing event called the “CrossFit Total”, which hasn’t featured in the Games since 2007, where athletes will be tested with three one-repetition maximum challenges.

Castro had teased fans and athletes by posting an image of a road bike on his Instagram page two weeks ago, with many speculating that Event 1 would be a triathlon.

More commonly known as a “crit”, Individual Event 1 will consist of 10 laps around a 1,200 metre closed circuit, for a total of 7.5 miles, that has been set up in the arena.

There will be two heats of 40 – one for the men, and one for the women, with all athletes racing at the same time.

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Time trials will be held beforehand to determine the initial places, with a rolling start behind a pace bike.

Once the pace bike has exited the course, racing will begin, and a white flag will be shown to signify the start of the final lap.

“There is a high possibility of crashes. Don’t crash,” Castro told the athletes. “I don’t really want you guys to crash. You can’t crash this early. You haven’t seen the best stuff yet.”

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Ahead of his announcement of the marathon row, Castro had already hinted that Individual Event 4 promised to be a “nice finisher” to what “might end up just being the single hardest day in Games history”.

The full marathon row will be the longest event in Games history, surpassing the half marathon row in 2013.

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Details of the full schedule are yet to be released, as is Castro’s way. But we know that Individual Event 9, which will take place on Saturday, is titled “Chaos” with the scoring section of the CrossFit Games website detailing that it will be scored out of 100 points.

Team Event 1 will take the form of a four-person dead lift challenge.

Castro also confirmed on Monday that Fibonacci will return to the Games, this time as a “Redemption” event.

Only one male athlete, Logan Collins, finished the Fibonacci Final in 2017, which came at the end of a four-day stretch of events.

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This time the event is scheduled earlier in the week on Friday, with Castro believing more men will now have the stamina to finish it.

The time cap is still six minutes, as in 2017, when 27 women finished the Fibonacci Final.