PITTSBURGH -- A few years ago, the Pittsburgh Steelers purchased an AlterG machine, which helps players run on a treadmill at a reduced body weight. It alleviates pressure on the lower body.

Heath Miller uses the machine often, including this week. He started in the offseason before the 2013 season as he rehabbed a torn anterior cruciate ligament.

He's 33 now and still is a starting NFL tight end, and he attributes this machine for helping keep him fresh.

"It's like running in water," said Miller, who typically runs at 60 percent of his body weight.

The machine is a fixture in the Steelers' training room for several players.