Guislin previously took part in the 2009 Summer National Senior Games, which were also held at Stanford. More than 30,000 people attended.
"I had never competed in an Olympic-style event," he said on Wednesday. "My wife and I had to qualify for the nationals. We had such a great time that now we're addicted."
Guislin will compete in the 50-, 100-, 200- and 500-yard competitions, he said. He will also carry the solar torch at Stanford to open the games.
Although he has not broken any records, he does take pride in his "personal bests," he said.
The athletic championship for seniors is a qualifying competition for the National Senior Games or "Senior Olympics" in Cleveland, Ohio, in 2013, said Anne Warner Cribbs, California Senior Games Association chairperson and organizer of the Bay Area games.
This month's games are expected to draw more than 2,500 athletes in 27 sports, from tennis and cycling to horseshoes and rugby.
Seniors continue to break boundaries in sports activities, even those considered strenuous, Cribbs said.
This year, a special award, the ENCORE Cup Series, will highlight so-called Boomer sports: soccer, rugby, water polo, sailing and fencing, she said.
The National Senior Games Association has not yet sanctioned these demanding sports, Cribbs said. But among the California Senior Games Association, "We believe they deserve recognition," she said. Trophies will be awarded to the outstanding men's and women's team and individual in each sport annually, she said.
New also this year is the bocce tournament, which has 100 entrants so far and will take place in Livermore, Cribbs said. Bocce was added at the request of many of the sport's enthusiasts. And an eight-team rugby tournament at Stanford will return for a second year.
Cribbs pointed out that senior athletes "are anything but 'retiring.' They train hard and use their life experience to deliver all-out performances, capturing a piece of the Olympic spirit that inspires us all. These athletes provide a model for an active and engaged life for their peers as well as following generations."
Guislin agreed. "If you asked me five years ago if I would be getting up at 5 in the morning to swim, I would have said you were crazy," he said. "At Stanford (Master Swimmers), every third person is a physician because they believe it's the fountain of youth."
New age-group records are set in swimming and track and field each year at the games, according to Cribbs. Track and field produced three American records and three world records at California's 2011 State Championships.
But the real thrill of engaging in athletics for Guislin is talking to fellow swimmers. "Everybody's your age. I feel like I'm with 100 people who are my best friends," said Guislin, who typically works out by swimming 2,500 to 3,500 meters each day.
The bulk of the games are centered at the Stanford athletic fields. The events are open to athletes 50 and older, and spectators are admitted for free.
Competitions include archery, badminton, basketball, bocce, bowling, cycling, feats of strength, fencing, golf, horseshoes, lawn bowling, race walk, racquetball, road race, rowing, rugby, sailing, shuffleboard, soccer, softball, swimming, table tennis, tennis, track and field, triathlon, volleyball and water polo.
The lawn-bowling tournament takes place at the Palo Alto Lawn Bowls, at 474 Embarcadero Road (next to Gamble Garden), March 20-22. The golf tournament takes place March 13 at Palo Alto Municipal Golf Course, 1875 Embarcadero Road.
Cribbs said she is particularly proud of the eight or nine women's water polo teams that will compete. Water polo is a sport that many women did not get to play in high school since it was reserved for males. But women who watched their children play in high school decided to start their own teams.
There is a theory that once people reach a certain age, they can't engage in vigorous sports. But Cribbs said the games show that athletics are the key to a good, healthful quality of life.
"We can show the world that the competition never ends," she said.