A common antidepressant combined with an intensive treadmill training program helped people with partial spinal cord injuries walk better and faster, U.S. researchers said on Sunday.

They said Forest Laboratories' antidepressant Lexapro or escitalopram, which affects a message-carrying brain chemical called serotonin, helps strengthen remaining nerve connections along the spine, giving patients with spinal cord injuries more ability to control their muscles during training.

"The drug is enhancing the effects of the therapy," said George Hornby, a research scientist at the Rehabilitation Institute of Chicago, who is presenting his findings at the Society for Neuroscience's meeting in Chicago.

"The drug on its own isn't a miracle drug. What you need is the drug plus the training," Hornby said in a telephone interview.

The findings are the first in humans and builds on studies in animals that found giving serotonin-like drugs after spinal cord injuries can promote recovery of walking when paired with an intensive training program.

For their study, Hornby and colleagues tested the effects of antidepressants in 50 people who had partial ability to move a year after they had suffered a spinal cord injury.

Of these, 34 patients could walk on their own, but slowly.

All 50 underwent an eight-week walking program on a motorized treadmill, assisted by a robot or physical therapist. Up to 40 percent of their body weight was supported in a harness.

Five hours before training, they were given either 10 mg of Lexapro or a placebo.

While both groups improved, those who took Lexapro were able to walk much faster, Hornby said.

He said the drugs appeared to work by increasing muscle spasms experienced by people with spinal cord injuries, something most doctors consider to be a negative side effect of these types of injuries.

Hornby said the muscle spasms represent reflexes, which can be trained. Patients who have a spinal cord injury "rely on those reflexes to walk," he said.

The volunteers only got an antidepressant only on the day of training, but the benefits lasted after the drug was out of their systems, Hornby said.

He thinks the drug is strengthening the residual connections between the brain and the spinal cord.

"It helps you drive that muscle harder, and it's easier for the brain to activate the muscle," he said.

The researchers plan to do more studies using different antidepressants to see which works best. And they may also try electrical stimulation of muscles to see if that enhances the effect.