Leading the way on Saturday are 2007 world leader Reese Hoffa (Athens, Ga.) and defending world champion Adam Nelson (Charlottesville, Va.) in the men's shot put. Fresh off a stunning personal-best throw of 22.43/73-7.25 on August 3 in London, Hoffa will be most tested by his American teammates. In addition to being the defending world champion, Nelson is a two-time Olympic and World Outdoor silver medalist. Dan Taylor (Carbondale, Ill.) and Noah Bryant (Santa Barbara, Calif.) also will challenge for medal-podium finishes.

On the track, American record holder Deena Kastor (Mammoth Lakes, Calif.) leads an American contingent that includes Kara Goucher (Portland, Ore.) and Katie McGregor (St. Louis Park, Minn.) in the women's 10,000 meters, while Mbarak Hussein (Albuquerque, N.M.), Simeon Sawe (Santa Fe, N.M.), Fernando Cabada (Bloomington, Ind.), Mike Morgan (Rochester Hills, Mich.) and Kyle O'Brien (Shelby Township, Mich.) contest the men's marathon.

The women's heptathlon begins day 1 of competition, with qualifying rounds in several events, including the men's 1500m, men's 400m hurdles, men's triple jump and men's 100 meters. Below is a time schedule for Saturday and list of U.S. entrants.

Team USA entrants - Saturday, August 25

7 a.m., men's marathon final - Mbarak Hussein (Albuquerque, NM), Simeon Sawe (Santa Fe, NM), Fernando Cabada (Bloomington, IN), Mike Morgan (Rochester Hills, MI), Kyle O'Brien (Shelby Township, MI)

10 a.m., men's shot put qualifying - Adam Nelson (Charlottesville, VA), Reese Hoffa (Athens, GA), Dan Taylor (Carbondale, IL), Noah Bryant (Santa Barbara, CA)

10 a.m., women's heptathlon 100H - Hyleas Fountain (Kettering, OH), Diana Pickler (Pullman, WA), Virginia Johnson (State College, PA)

10:40 a.m., women's steeplechase - Jennifer Barringer (Boulder, CO), Anna Willard (Ann Arbor, MI), Lindsey Anderson (Morgan, UT)

11:20 a.m., heptathlon high jump

11:25 a.m., men's 1500m - Alan Webb (Reston, VA), Leonel Manzano (Austin, TX), Bernard Lagat (Tucson, AZ)

12:10 p.m., men's 100m first round - Tyson Gay (Fayetteville, AR), Mark Jelks (Kansas City, KS), J-Mee Samuels (Fayetteville, AR)

7:10 p.m., heptathlon shot put

7:30 p.m., women's 800m first round - Alysia Johnson (Canyon Country, CA), Hazel Clark (Knoxville, TN),Alice Schmidt (San Diego, CA)

7:30 p.m., men's hammer qualifying - A.G. Kruger (Ashland, OH), Kibwe Johnson (Ashland, OH)

8:15 p.m., men's 100m second round

8:20 p.m., men's shot put final

8:30 p.m., men's triple jump qualifying - Walter Davis (Baton Rouge, LA)*, Aarik Wilson (Bloomington, IN), Lawrence Willis (Lafayette, LA), Kenta Bell (Decatur, GA)

8:40 p.m., men's 400m hurdles first round - Bershawn Jackson (Raleigh, N.C.)*, James Carter (Raleigh, N.C.), Kerron Clement (Gainesville, FL), Derrick Williams (Fayetteville, AR)

9:30 p.m., heptathlon 200m

9:50 p.m., women's 10,000m final - Deena Kastor (Mammoth Lakes, CA), Kara Goucher (Portland, OR), Katie McGregor (Saint Louis Park, MN)