116th Boston Marathon

Temperatures that rose into the 80s slowed the field at the 116th Boston Marathon and may have convinced as many as 4,300 runners to sit this one out. A total of 22,426 runners started the race in Hopkinton in temperatures expected to be as high as 84 by the time the last of them finish their 26.2-mile trek to Boston's Back Bay. Runners are seen here starting the marathon, in Hopkinton, Mass., on Monday, April 16, 2012.

Allison Roe, the 1981 Boston Marathon women's champion, fires the starters pistol for the elite women's start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

The elite men start the 116th running of the Boston Marathon, in Hopkinton, Mass.

Masazumi Soejima, of Japan, waits for the start of the wheelchair division of 116th running of the Boston Marathon, in Hopkinton, Mass.

Geoffrey Mutai, of Kenya, warms up prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Dick Hoyt, left, and his son, Rick, start the 116th running of the Boston Marathon, in Hopkinton, Mass.

From left, Masazumi Soejima, of Japan, and Ernst Van Dyk, of South Africa, start the wheelchair division of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Caroline Kilel, of Kenya, the 2011 Boston Marathon women's winner, warms up prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Runners wait to have their photograph taken in front of the "Welcome to Hopkinton" sign at the athlete's village prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Kurt Fearnley, of Australia, start the wheelchair division of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Volunteers fill cups at the athlete's village prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

A runner grabs a bottle of water at the athlete's village prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Elizabeth Corkum, from New York City, poses for a photograph in front of a sign prior to the start of the 116th running of the Boston Marathon, in Hopkinton, Mass. Corkum has run five previous marathons, but this will be her first Boston Marathon.

Wakako Tsuchida, center, from Japan, waits for the start of the wheelchair division of the 116th running of the Boston Marathon, in Hopkinton, Mass.

Morgan Uceny, right, finishes in the B.A.A. Invitational Mile in Boston on Sunday, April 15, 2012.

Collis Birmingham, of Australia, wins the B.A.A. Invitational Mile in Boston on Sunday, April 15, 2012. The race, which is sponsored by the Boston Athletics Association, is a prelude to Monday's 116th running of the Boston Marathon.

Collis Birmingham, of Australia, wins the B.A.A. Invitational Mile in Boston on Sunday, April 15, 2012.

Morgan Uceny, right, finishes first ahead of Marina Muncan, of Serbia, left, in the B.A.A. Invitational Mile in Boston, Sunday, April 15, 2012. The race, which is sponsored by the Boston Athletics Association, is a prelude to Monday's 116th running of the Boston Marathon.