EAST RUTHERFORD, N.J. — Giants General Manager Jerry Reese looked out a window at the team’s training facility one day last summer and quickly became confused. He knew that Manchester United, the British soccer power, was training at the facility ahead of its match with all-stars from Major League Soccer, but he had no idea what the players were wearing.

“Ronnie, what’s that strap on their back?” Reese said to Ronnie Barnes, the Giants’ vice president for medical services. Barnes smiled.

“That’s a G.P.S. device,” he told Reese. “And we should have them, too.”

The reason, Barnes said, was simple. Technology, the Giants hope, will ultimately help optimize a player’s ability while reducing the risk of injury, essentially telling the team when a player is physically ready to be at his best. Now, after dabbling with the use of heart-rate monitors before last season, the Giants are pushing forward with the idea, an outlier among N.F.L. teams.

In recent off-season workouts, the Giants used heart-rate monitors, G.P.S. devices and hydration/nutrition monitoring to better evaluate how much energy a player had exerted and how quickly he was recovering. While similar technology is widely used by soccer teams around the world, as well as by athletes in individual sports, like runners, few professional sports teams in the United States have shown an interest.