Growing up, Edwin Moses devoured biology, math and anatomy books, collected fossils and conducted science experiments—but he wasn't particularly athletic.  "Education was the top priority in my family, so I spent a lot of time with my head in a book," says Mr. Moses, adding that he was a "tiny kid with braces and glasses, so I got beat up a lot." But in high school, Mr. Moses discovered he was a fast runner. "I was small but had long legs, so I went out for track and field."  Olympic résumé: 400-meter hurdles: 1976, Montreal; 1984, Los Angeles; 1988, Seoul  Current path: Chairman of Laureus, a nonprofit foundation that brings sports and education to children in developing countries  Why this path: "I wanted to work with people with big ideas about world affairs and global change."  That decision would culminate in three Olympic medals—two gold and one bronze—in the 400-meter hurdles. The first medal came in 1976, and the last 12 years later. At one point, Mr. Moses won 122 consecutive races and was undefeated for a period of nine years, nine months and nine days.  Mr. Moses became celebrated in running circles for taking 13 steps between each hurdle (the norm was 14) and for sheer determination. He earned a degree in physics and later held a full-time job as an aerospace engineer, all while training and competing at a relentless pace.  "I don't mind putting in the time to become better and better at something," says Mr. Moses, who won his first gold in the 1976 Montreal Olympics while still in college, where he practiced six hours a day and studied until 2 a.m. most nights. Later, while working at General Dynamics Corp. as an engineer, he ran from 6 a.m. to 2 p.m., and then put in a full workday from 3 to 11 p.m.  Edwin Moses comes down the stretch in the 400-meter hurdles at the 1976 Olympics in Montreal.  "I never really had a coach, I just learned by doing and devised my own training program by reading books and watching films," he says. Mr. Moses left his job at General Dynamics in 1980 to devote himself full time to track. Because the U.S. boycotted the 1980 Moscow Olympics, however, true stardom did not come until after the 1984 Los Angeles Olympics, where he again won the gold medal. Then came a profitable career of endorsements and sponsorship deals, including Eastman Kodak Co., Italy's Kappa sportswear and Adidas AG.  Though he ruptured a disk in his back in 1986, Mr. Moses underwent daily physical therapy and continued to compete until his retirement in 1988, taking home a bronze medal in that year's Seoul Olympics.  After his retirement, Mr. Moses obtained a master's in business while also "detraining" himself, slowly moving from eating 5,000 calories and running hours each day to a more normal pace. He became involved with the U.S. Olympic Committee from 1989 to 1996, serving as chairman of groups on substance abuse, research and education, and later worked for a subsidiary of Smith Barney as a financial adviser. All the while, he continued his public speaking and commercial endorsements.  "I was busy and enjoyed learning about business, but it wasn't enough for me," Mr. Moses recalls. "I didn't want to think about money all the time."  In 2000, he was recruited to become executive chairman of the Laureus nonprofit foundation, based in London, and continues to hold that post today. The organization raises funds for more than 90 projects that provide coaching and education to young people in 35 developing countries.  "Laureus is exactly what I want to do: We're bringing good to the world through sports," says Mr. Moses, age 56, who plans to continue working with Laureus for many years and will also be actively involved in the 2012 Olympics as a TV commentator and newspaper columnist. "I never would have dreamed up any of my life—from winning the gold in '76 to now helping 1.5 million kids around the world. It's all been a surprise and a gift."  Greg Louganis may be the most famous diver of all time, but he sees his time in the water as just a small part of his life.  Now 52, the five-time Olympic medalist (four gold, one silver) and five-time world champion has worked as an actor, spokesman, dog trainer, diving coach, film producer, mentor and author, among other pursuits.  Olympic résumé: Diving: 1976, Montreal; 1984, Los Angeles; 1988, Seoul  Current path: Writer, diving mentor, actor, professional speaker  Why this path: "There are two kinds of people—those who complain about the economy and world affairs, and those who accept a new reality and are being creative to make ends meet. I'm one of the positive people."  "My life is my résumé," Mr. Louganis says simply. "I'm very positive about my future."  That's a marked contrast from earlier points in his life. Growing up in San Diego with his adoptive parents, Mr. Louganis suffered early on from depression. He remembers being bullied as a child for his choice of activities, including dance, acrobatics and gymnastics.  A saving grace: the family swimming pool, where hours of practice led to a first diving lesson at age 9. Just two years later, Mr. Louganis scored a perfect 10 at the 1971 Junior Olympics national competition. (He would go on to win 47 national titles.) At age 16, he competed in the 1976 Olympics in Montreal, where he won a silver medal in the 10-meter platform event.  Feeling that he had failed, Mr. Louganis went into a "dark period," he says, abusing alcohol and drugs. Still, he continued to train, graduated from college—and, eventually, got his life back on track. He was the gold-medal hopeful for the 1980 Moscow Olympics, until the U.S. decided not to attend. He made up for it in 1984, winning gold medals in both the three-meter springboard and 10-meter platform—the first man to achieve that Olympic double since 1928.  Greg Louganis performs in the springboard event during the 1984 Olympics in Los Angeles.  "After '84, I got swept up in a blitz of publicity, but it was short-lived," Mr. Louganis says. "I got a few sponsor deals and commercials, but [gymnast] Mary Lou Retton was really the main attraction."  In 1988, he won two more gold medals at the Seoul Olympics, a feat made all the more remarkable given a head injury sustained during a complex dive. That same year, though, Mr. Louganis—then age 28—learned that he had the AIDS virus.  The diagnosis "was seen as a death sentence then, so I had no expectations about my future," he says.  After retiring from diving in 1989, Mr. Louganis focused on "getting well and beating HIV." When he realized that treatment would allow him to live a full life, he began pursuing new interests. His best-selling autobiography, "Breaking the Surface," came out in 1995.  Going forward, "there are so many paths I could take," Mr. Louganis says today. A third book is in the works.  He currently gives speeches, judges diving events and acts. He also devotes time to mentoring young athletes on the U.S. diving team.  "I love working with these kids," Mr. Louganis says. "My greatest joy would be for these hopefuls to break my records. I want them to succeed."  Despite having already run close to 150,000 miles in her lifetime, Joan Benoit Samuelson sees no reason to stop.  Olympic résumé: Marathon: 1984, Los Angeles  Current path: Professional runner, speaker, environmental advocate  Why this path: "There is a niche for all of us to build on our passions to inspire each other. Running has given me so much, and now I want to give back to the world."  Winner of the gold medal in the women's marathon at the 1984 Olympics, Ms. Samuelson, now 54, continues to run competitively and break records for her age group.  "With every finish line I cross, there are new reasons to keep going," she says.  She is best remembered for three feats: winning the women's Boston Marathon in 1979; taking home the gold medal in Los Angeles, the first Games to hold a women's marathon; and winning the 1985 women's Chicago marathon in 2:21:21, an American record for 18 years.  Since then, she has built much of her life around running and served as a role model for millions of marathoners. "Finding something you are truly passionate about not only charges your own life, but inspires others," she says.  Ms. Samuelson grew up in Maine, where she still lives with her husband, Scott. Her early dreams centered on ski racing. But after breaking a leg in high school, she turned to running for rehabilitation.  Joan Benoit breaks away from the pack in the women's marathon of the 1984 Olympics.  "I think it was also a bit about survival of the fittest; I had three brothers and was always running to them for help, or away from them because I had taunted them in some way," says Ms. Samuelson, who grew up in an athletic family. (Her 91-year-old father still skis regularly.)  In 2008, she again found herself in the Olympic trials, thinking the race would mark the end of her competitive career. But after running a sub-2:50 marathon in the over-50 category, she decided to keep racing.  Ms. Samuelson has parlayed her love of running into a profitable career. She is a consultant and spokeswoman for Nike Inc. She has given motivational speeches and has written several books, including "Running for Women," and advises cross-country and long-distance athletes.  Her biggest passion, though, remains running. She still logs about 75 miles a week and often runs races on the weekends. In 1997, she founded the TD Bank Beach-to-Beacon 10K Road Race, held in Maine each August. Race proceeds go to children's charities.  In recent years, she has broken records for women age 50-plus in several races, including the Boston, New York and Chicago marathons.  She is involved in organizations focused on solving health and environmental challenges and hopes to create a "sustainable endurance-training and health center" in Maine where athletes and patients can learn healthy-living strategies.  She hopes to slow her pace enough to pursue a master's degree in public health, now that her children are grown.  "I don't really have a job description," she says. "Every day is different and new."  Long before he became a pinup in a stars-and-stripes bathing suit, Mark Spitz wanted to be a dentist. But after his legendary performance at the 1972 Munich Olympics, where he won seven gold medals, Mr. Spitz was bombarded with endorsement offers. He dropped out of dental school and became one of the most famous athletic pitchmen of all time.  Olympic résumé: Swimming: 1968, Mexico City; 1972, Munich  Current path: Entrepreneur, motivational speaker, investor  Why this path: "I get passionate about new projects. I always want to try new things I've never done before."  "I got shot onto the world stage, a hunk in a Speedo," says Mr. Spitz, 62, who still does sponsorships. "I was an innocent kid who got an extremely quick education in the world of promotion."  All of which started at a YMCA summer camp. "I came home from the first day of camp upset because I didn't want to make arts and crafts—little earrings—all summer," he says. "So my mom asked if I could do more swimming, and I got picked to be on the swim team. It was total chance."  By 10, he was winning every meet he entered. He began training intensely at the Arden Hills Swim Club in Sacramento, Calif., and then moved with his family to Santa Clara to work with Olympic coach George Haines. By 14, he set his mind on the Olympics.  "My parents didn't have a lot of money, but they made sacrifices to support me in my goals," says Mr. Spitz. He set his first world record at 17, in the 400-meter freestyle. A year later, at the 1968 Olympics in Mexico City, he won two gold medals, a silver and a bronze.  Mark Spitz in the butterfly leg of the 400-meter medley relay at the 1972 Olympics in Munich, one of his seven gold medals and world records at those Games.  In 1972, he became the first athlete to win seven gold medals in a single Olympics, setting world records in all seven events. (That mark would stand until swimmer Michael Phelps won eight gold medals in 2008 in Beijing.) He retired from the pool in 1972, having broken 35 world records.  At that point, Mr. Spitz began doing commercials and endorsements (brands as diverse as California Milk Advisory Board and Schick Co. came knocking) and a bit of acting. He eventually became a real-estate developer and helped start several companies, including a prepaid-phone-card venture that went public and was later acquired by AT&T. He was a licensed stockbroker for several years and still manages a portfolio of private-equity investments.  "When you are 22 years old, you feel you will never get old," says Mr. Spitz, who lives in Los Angeles with his wife of 39 years, Suzy. "But even though I've matured, I still have the youthful enthusiasm that has always been the seed of my success."  Second Acts looks at the many paths people are taking in their 50s and beyond. Kristi Essick, the author of these profiles, is a writer in California. You can reach her, and let us know how you're starting over in later life, at next@wsj.com.
Gold medalists Edwin Moses, Greg Louganis, Joan Benoit Samuelson and Mark Spitz talk about how they started over following their Olympic successes, and what drives them now.