KNOXVILLE, Tenn. -- Nick Thoman didn't know quite what to expect when he returned to competitive swimming after a nine-month layoff.
So far, so good.
Thoman set two individual American records and was part of a record-breaking relay team Friday in the Winter National Championships at the University of Tennessee's Allan Jones Aquatic Center. That included an electrifying 100-yard backstroke performance in which he beat fellow Olympic gold medalist and former American record-holder Matt Grevers.
"I knew it was going to be a hard day," Thoman said. "Racing against Grevers, I'm glad he made me work for it. I just kind of put my faith in the training. Thank God I could get back after taking nine months off. It was just great."
Thoman took those nine months off after winning a gold medal in the 400-meter medley relay and a silver in the 100-meter backstroke at the 2012 Summer Olympics. He took it easy, went to Mardi Gras and gained about 30 pounds. He got back in the pool for good in May and has been working his way back ever since.
"I just had fun and did all the things I couldn't do when I was swimming," Thoman said. "Then I really got hungry again for getting back in the water and for competition. I've been doing pretty well ever since."
Thoman won the 100-yard backstroke with an American-record time of 44.07 seconds. He also joined Eric Knight, Tim Phillips and Cullen Jones on a 200 medley relay team that set a U.S. record with its time of 1 minute, 23.02 seconds. Thoman's 50 backstroke time of 20.69 seconds while swimming the first leg of the 200 medley relay also counted as an individual American record.
The American record in the 100 backstroke was formerly held by Grevers, who posted a time of 44.55 last year. Grevers, who did win the 100 butterfly Friday in 44.94 seconds, said he knew he'd have to break his own record to win the 100 backstroke. As it turned out, even that wasn't quite good enough.
"I thought I could be around 44.5, which I ended up being," said Grevers, who posted a runner-up time of 44.49 seconds. "And he was a lot faster. It was just an impressive swim by him."
Missy Franklin also was impressive.
The four-time Olympic gold medalist set a meet record in the 200 freestyle (1:41.40), won the 100 backstroke (51.59) and joined California teammates Caroline Piehl, Camille Cheng and Elizabeth Pelton on an 800 freestyle relay team that set a meet record (6:59.11).
In the 200 freestyle, Franklin beat fellow Olympic gold medalist Katie Ledecky, who finished second in 1:42.03. One day earlier, Ledecky finished first and Franklin second in the 500 freestyle.
And in the 100 backstroke, Franklin was followed in order by California teammates Pelton, Rachel Bootsma and Melanie Klaren.
"It's awesome," Franklin said. "I think one of the things Cal is kind of known for is our backstrokers. We have a lot of elite backstrokers on our team. To kind of come out here to nationals and get one through four is awesome, and to have five girls I believe in the heat. It was just so fun. We joke it really is just like practice."
Friday also featured a winning performance from a hometown swimmer. Claire Donahue, who grew up less than 30 miles from Tennessee's campus in Lenoir City, won the women's 100 butterfly in 51.69 seconds.
"It was a little more nerve wracking," Donahue said. "My entire family was here. I had some old teammates here. But it's kind of comforting too to know you have that kind of support."
Other individual winners included Celina Li in the women's 400 individual medley (4:06.54), Andrew Seliskar in the men's 400 individual medley (3:41.19), Joao De Lucca in the men's 200 freestyle (1:31.65), Alia Atkinson in the women's 100 breaststroke (57.62) and Damir Dugonjic in the men's 100 breaststroke (51.93).
California's Cindy Tran, Marina Garcia, Farida Osman and Kaylin Bing won the women's 200 medley relay (1:36.91). Michigan's Michael Wynalda, Connor Jaeger, Jack Mangan and Justin Glanda won the men's 800 freestyle relay (6:21.70).
The three-day meet, sponsored by AT&T, concludes Saturday.