Every runner has a signature form that aficionados can identify as precisely as a fingerprint. Some of the greats – like the Czech hero Emil Zatopek – have a crazy quilt form that resembles a drunk rumba dancer but it got the job done. Others, like Catriona Morrison and Gwen Jorgenson and Javier Gomez seen here, have elegant strides that should be memorialized on a Grecian urn.

No matter whether it is in Denmark or Maui, London or Texas, running remains the purest expression of the eternal athlete, the essence of which has not changed from the from the time of the caveman hunters to today’s recreational runners swathed in space age materials.

All photographs ©Timothy Carlson

Andy Potts and Rasmus Henning fought one of the best duels of the year at Ironman 70.3 California. Potts broke loose in the final mile for the win.

Jonas Colting of Sweden had two wins and a second but injuries forced him to withdraw after just 6 miles of valiant effort on the final day's double marathon.

There may be no lovelier race course landscape than Pacific Grove.

Andreas Raelert came into Kona with 3rd and a 2nd place finishes hoping that he could duplicate Tim DeBoom’s 1998-1999-2000 3-2-1 progression. But Craig Alexander and Pete Jacobs had better days.

Rebekah Keat repeated her 2010 win and sub 9-hour clocking this year at Challenge Copenhagen.

Young runner at the Pacific Grove sprint triathlon.

Brian Fleischmann retreating back to the course after going up the wrong sand ladder at the San Francisco Triathlon at Alcatraz.

Ultraman runner and pacer share a near-kiss on the run.

Legendary pitcher Satchel Paige said “Don’t look back – somebody might be gaining on you.” most elite competitors follow his advice religiously.

It’s not all about the bike – Lance Armstrong runs at XTERRA USA Nationals in Ogden Utah.

Catriona Morrison unleashed a 3:04:14 run to break 9 hours and win Memorial Hermann Ironman Texas.

Another scenic spot along the Challenge Copenhagen run.

Gwen Jorgenson ran a race-best 33:43 10k to earn second place at the London round of the ITU World Championship Series and secure the first US women’s 2012 Olympic slot.

Running past the elegant Nyhaven waterfront at Challenge Copenhagen.

Frederik Van Lierde tries sponges and water to cool off at a Palani Road aid station at Ironman Hawaii.

Javier Gomez takes an aggressive, elegant stride in a pouring rain at the London WCS.

Sebastian Kienle is a power runner – seen at Ironman Arizona.

Near gale force winds pushed Michael Coughlin to a second place overall finish and third fastest double marathon on Day 3 of Ultraman. Don’t believe? Just check the bent over palm trees at the entrance to the Mauna Lani.

This was just as close as Tim O’Donnell could get to Eneko Llanos on the run at Ironman Texas.

Melanie McQuaid led the XTERRA World Championship until the final mile of the run. Then she collapsed with 400 meters to go.