When his back locked up one day in spring training, Diamondbacks right-hander Bronson Arroyo couldn't pitch. He also couldn't step foot in the weight room or do most of the other things he considers essential to staying in pitching shape as a 37-year-old.

"Missing three weeks of spring training was tough on me," Arroyo said on Friday night after turning in his best start of the season, tossing seven shutout innings in a 2-0 win over the San Diego Padres at Petco Park.

"People don't realize what it takes out of a guy like me to not be able to go in the weight room and lift and be able to stay strong. The body starts atrophying pretty quick. For some of the bigger, stronger, younger guys, they can go out there and feel like their arm is really fresh. But for me, I need a lot of work in order to stay kind of strong."

The back didn't force Arroyo to miss any starts in the regular season, but he said it wasn't until a couple of weeks ago that he was able to return to the usual between-starts workout routine he's had for the past 10 years. And doesn't think it's a coincidence that he's finally starting to give the Diamondbacks the kind of results they expected when they signed him to a two-year, $23.5 million deal in February.

In his past two starts, Arroyo has given up just two runs in 13 1/3 innings, allowing 10 hits and two walks while striking out eight.

On Friday, he said he felt like he had more zip on his pitches than he had in previous starts. According to Pitch-f/x data at the web site BrooksBaseball.net, Arroyo averaged 88.4 mph with his two-seam fastball. He entered the day averaging 85.6 mph with his fastball, according to FanGraphs.

"I'm starting to feel a little better," he said. "It makes a difference for me when I can get the ball up to 88-89 mph once in a while. It makes them respect some of my other stuff a bit more."

Arroyo didn't allow his first hit until there was one out in the fifth inning. He hadn't struck out more than three in his previous five starts; he had four strikeouts by the end of the fourth inning and finished with six.