Olympic athletes aren't known for being shy and retiring - but some of the sportsmen and women let their troubles get to them more than others.

For a man not known for his smile, Great Britain's Andy Murray is one of London 2012's most expressive athletes when it comes to beating himself up.

But it's Germany's Markus Steuerwald, pictured above, who has pulled the toughest pouts in the tournament so far, during his volleyball match against Serbia.

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  • London Olympic Games - Day 2

    China's Jingbiao Wu reacts in the men's 56kg weightlifting competition. PRESS ASSOCIATION Photo. Picture date: Sunday July 29, 2012. See PA story OLYMPICS Ceremony. Photo credit should read: Stephen Pond/PA Wire. EDITORIAL USE ONLY

  • Tennis - 2012 Wimbledon Championships - Day Nine - The All England Lawn Tennis and Croquet Club

    Great Britain's Andy Murray reacts against Spain's David Ferrer during day nine of the 2012 Wimbledon Championships at the All England Lawn Tennis Club, Wimbledon.

  • Serbia's Nikola Rosic (19) reacts to a point against Germany during a men's volleyball preliminary match at the 2012 Summer Olympics Thursday, Aug. 2, 2012, in London. (AP Photo/Chris O'Meara)

  • Serbia's Milos Nikic (10) is attended to after getting hit in the face with a spike by Germany during a men's volleyball preliminary match at the 2012 Summer Olympics Thursday, Aug. 2, 2012, in London. (AP Photo/Chris O'Meara)

  • Germany's Markus Steuerwald (2) reacts to a point against Serbia during a men's volleyball preliminary match at the 2012 Summer Olympics Thursday, Aug. 2, 2012, in London. (AP Photo/Chris O'Meara)

  • Diving - Fina Diving World Series 2011 - Day Two - Ponds Forge

    Great Britain's Tom Daley reacts after finishing fourth the mens 10m final during day two of the Fina Diving World Series at Ponds Forge, Sheffield.

  • London Olympic Games - Day 2

    Great Britain's Steven Larsson reacts after being sent off against France during the Group A match at the Copperbox at the Olympic Park, London.

  • U.S. gymnast Danell Leyva during the artistic gymnastics men's individual all-around competition at the 2012 Summer Olympics, Wednesday, Aug. 1, 2012, in London. (AP Photo/Julie Jacobson)

  • South Korea's Shin Lam reacts after being controversially beaten in her Womens Fencing Epee Individual semi final match against Germany's Britta Heidemann at the ExCeL centre, London during the third day of the London 2012 Olympics. Picture date: Monday July 30, 2012. Photo credit should read: Julien Behal/PA Wire