Veins are seen on the horse Clifton Promise while mounted by New Zealand rider Jonathan Paget during training for the equestrian eventing competition in Greenwich Park at the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/David Goldman)

The horse Oregon De La Vigine of France rider Denis Mesples have a cover with a skull on the head during a training session at Greenwich Park, the site for the equestrian and modern pentathlon events at the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Markus Schreiber)

Footprints from a gymnast are seen on the floor during training session ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Julie Jacobson)

China's Feng Zhe trains on the vault during a practice session ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Gregory Bull)

A gymnast from China practices during a training session ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Emilio Morenatti)

A beach volleyball in pictured against the scenic Admiralty House during practice at the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. The Beach Volleyball venue is being played at the historic Horse Guards Parade. (AP Photo/Dave Martin)

Dancers perform during ceremony to welcome athletes from Syria for the 2012 Summer Olympics at Olympic village on Wednesday, July 25, 2012, in London. (AP Photo/Eranga Jayawardena)

USA's Ryan Lochte trains at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27.(AP Photo/Daniel Ochoa De Olza)

Swimmers practice in the pool at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Matt Slocum)

Golfer Rory McIlroy, of Northern Ireland, watches his girlfriend, tennis player Caroline Wozniacki, right, practice at the All England Lawn Tennis Club at Wimbledon, London, at the 2012 Summer Olympics, Wednesday, July 25, 2012. Tennis competition is scheduled to begin Saturday, July 28. (AP Photo/Mark Humphrey)

Cuba's Lisandra Guerra trains for the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Sergey Ponomarev)

A gymnast from China waits to practice during a training session ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. (AP Photo/Julie Jacobson)

Swimmers practice in the pool at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Matt Slocum)

A diver enters the pool at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Matt Slocum)

Australia's synchronized swimming team practice at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Mark Duncan)

Members of a British army reserve unit walk past the Olympic rings on the grounds of the rowing venue at the 2012 Summer Olympics, Wednesday, July 25, 2012, in Eton Dorney, near Windsor. (AP Photo/Peter Morgan)

Murat Shakenov of the Kazakhstan men's water polo team, throws a ball during a training session in preparation for the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. The opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Julio Cortez)

A diver jumps on a spring board during a practice session at the Aquatics Center at the Olympic Park ahead of the 2012 Summer Olympics, Wednesday, July 25, 2012, in London. Opening ceremonies for the 2012 London Olympics will be held Friday, July 27. (AP Photo/Matt Slocum)