There would be 4 members on each competing team assigned to a particular lane on the track. The amount of teams depends on the size of the meet and the size of the track. A small meet may only have two teams competing against each other, while a large one might have every lane full (6-10 lanes, depending on the venue).
There are 7 hurdles in a 75 meter relay
An athlete can compete in as many events as they qualify for at their country's Olympic trials. Jesse Owens won four gold medals (100 meter dash, 200 meter dash, 4x100 meter relay, long jump) at the 1936 Games. Mark Spitz won seven gold medals (100 meter freestyle, 100 meter butterfly, 200 meter freestyle, 200 meter butterfly, and three relay races) at the 1972 Games.
Swimmer Matt Biondi won 8 gold medals in Olympic competition: 1984 - 4x100 meter freestyle relay 1988 - 50 meter freestyle, 100 meter freestyle, 4x100 meter medley relay, 4x100 meter freestyle relay, 4x200 meter freestyle relay 1992 - 4x100 meter freestyle relay, 4x100 meter medley relay
4 ... gold in men's 4x100 meter freestyle relay and 4x200 meter freestyle relay and silver in 100 meter butterfly and 4x100 meter medley relay.
Brittany has not won an Olympic medal ... the 2012 Games in London will be her first Olympics where she will compete in the 4x100 meter freestyle and 4x200 meter freestyle relay races. She did win a gold medal at the 2009 Junior Pan Pacific Championships in 50 meter freestyle.
7, 5 gold and 2 silver: Gold: 50 meter freestyle, 100 meter freestyle, 4x100 meter medley relay, 4x100 meter freestyle relay, 4x200 meter freestyle relay Silver: 100 meter butterfly, 200 meter freestyle
Mark Spitz won seven medals at the 1972 Games: 100 meter butterfly - Gold 200 meter butterfly - Gold 100 meter freestyle - Gold 200 meter freestyle - Gold 4x100 meter freestyle relay - Gold 4x200 meter freestyle relay - Gold 4x100 meter medley relay - Gold He also won four medals at the 1968 Games: 4x100 meter freestyle relay - Gold 4x200 meter freestyle relay - Gold 100 meter butterfly - Silver 100 meter freestyle - Bronze
8 ... men's 4x100 meter freestyle relay, men's 4x200 meter freestyle relay, men's 100 meter backstroke, men's 100 meter butterfly, women's 4x100 meter freestyle relay, women's 100 meter butterfly, women's 200 meter butterfly, and women's 50 meter freestyle.
Swimmer Amy Van Dyken of the United States won 4 gold medals at the 1996 Games in Atlanta (50 meter freestyle, 100 meter butterfly, 4x100 meter freestyle relay, 4x100 meter medley relay) and 2 gold medals at the 2000 Games in Sydney (4x100 meter freestyle relay, 4x100 meter medley relay).
Gold: 100 meter dash, 200 meter dash, 4x400 meter relay. Bronze: 4x100 meter relay, long jump Those 5 medals were stripped by the International Olympic Committee in 2007 after she admitted to using performance enhancing substances.
4 ... she won 2 silver in 4x100 meter freestyle relay (1960, 1964), 1 in 400 meter freestyle (1956), and 1 in 4x100 meter medley relay (1960).
Í think that 6-7 people can compete in swimming.