Alexander, who's endured five operations on his left knee -- told the St. Louis Post-Dispatch after the workout that he's planning to operate at full health in 2011.
"I've been working out and training throughout this whole offseason to be a hundred percent for the season," he said. "It's a lot better than it was during the season. Everything's coming back like it's supposed to."
Quarterback Sam Bradford worked with Alexander in practice and liked what he saw.
"Watching him go through wide receiver drills and just getting off the line, he looks much quicker, looks much faster, much more explosive than he did (last) season," Bradford told the newspaper.
"Last year when he was healthy and was in the lineup, he made some big plays for us. So to have him at full go, it definitely is exciting."
The 6-foot-5, 220-pound Alexander was signed by the Rams in August after going undrafted in the 2010 NFL Draft.
After starting the year on the practice squad, Alexander was in an out of the lineup last season, hauling in 20 catches for 306 yards and a touchdown. He was injured in practice in late October and underwent a fifth procedure on his left knee to remove torn cartilage, but appeared in the team's final six games, starting the final two games against San Francisco and Seattle.
"It was great, just to see that I can play in this league at a pretty high level," said Alexander. "Coming in as a rookie, you think the NFL is this crazy league that's impossible to play in. So for me to come in and make an impact on the team was truly gratifying."
Alexander says last year's flashes were just a glimpse of what could be ahead.
"Just a little taste," he said. "A lot of guys are kind of writing me off because of the injuries that have happened in my career. I'm ready to show everybody what I can do."
The Associated Press contributed to this report.