Cyclists set out on a practice run for the Ironman 70.3 Kansas. The athletes worked out May 4, 2008, at Clinton Lake.

You may think riding a bike for 56 miles is tough.

Or hopping off the bike and strapping on running shoes to embark on a half marathon, often striving to keep the pace below 5-minute miles.

But the most intense, painful and downright ugly struggles of the Ironman 70.3 Kansas just might come during the competition’s first few minutes, or even seconds.

Sending 1,500 people into Clinton Lake for a swim won’t be for the faint of heart.

“Triathlon may not seem like a contact sport, but – let me tell you – the swimming is a contact sport,” said Ryan Robinson, a Lawrence triathlete and event co-director. “When you put that many people in that small of an area, it’s more like water polo.”

The Lawrence competition is one of 11 qualifying events in North America run by the Ironman organization, which has been building momentum ever since the first Ironman pitted endurance athletes on a grueling course in Hawaii back in 1978. Lawrence now joins a site roster that recently added Austin, Texas, and next year will include New Orleans.

While a full Ironman is the program’s most demanding – opening with a 2.4-mile swim, followed by 112 miles on a bike and then finishing with a full marathon, stretching 26.2 miles – the half course at Clinton Lake promises to be far more than a walk in the federal portion of the park.

The components:

¢ Swim. The 1.2-mile swim starts at 6:45 a.m. June 15 at Bloomington Beach. Competitors will jump into water expected to be about 72 degrees, and they will be permitted to wear wetsuits – providing both warmth and buoyancy. All event participants open with the swim, then will strive to make two right turns offshore before returning to the beach and the first transition, into the…

¢ Bike. Wet competitors will run their way to their waiting bicycles, staged in an adjacent parking lot. From there it’s a 56-mile trek, heading out on rural roads stretching north to Stull, west to the Douglas County line, south to U.S. Highway 56 and back to the lake’s transition point. But the course won’t be a square. Competitors will be riding out to each point and back, passing through the “Iron Cross” intersection of Douglas County Roads 458 and 1023 four times before getting back to the beach for the beginning of the…

¢ Run. After changing shoes and jettisoning helmets, competitors will hit the road for a half marathon. The course runs for two loops through roads at the southwestern end of the lake, with turnaround areas including a boat dock and a campground.

The finish line is back near the transition area at Bloomington Beach. Athletes will be vying for shares of $25,000 in prize money and qualifying spots for the world championships in November in Clearwater, Fla.