Intense treadmill exercise can be safe for people who have recently been given diagnoses of Parkinson’s disease and may substantially slow the progression of their condition, according to an important new study of adults in the early stages of the disease.

But the same study’s results also indicate that gentler exercise, while safe for people with Parkinson’s, does not seem to delay the disease’s advance.

As most of us know, Parkinson’s disease is a progressive neurological disorder that involves problems with motor control. Symptoms like weakness, stiffness, loss of balance and falls can make exercise difficult and potentially hazardous. Though Parkinson’s is currently incurable, its symptoms can be eased for a time with various drugs.

But most of those drugs lose their effectiveness in people over time.

So some researchers have begun searching for other treatment options, particularly for use in the beginning stages of the disease. If people with early Parkinson’s could brake the disease’s advance and delay their need to start medications, the researchers have reasoned, they might change the arc of their disease, delaying its most severe effects.