While she isn’t crazy about it, running on the treadmill is essential for 39-year-old Erica Sara. She’s a mother to a toddler, and the roads near her rural Pennsylvania town aren’t running-stroller friendly, nor are they safe for Sara when the sun isn’t up. When she can, she runs on the roads, but a couple of times each week, Netflix and the moving belt get her through.

Sara isn’t unlike many runners around the country, who for a variety of reasons need to manage at least some of their training on the treadmill. The question is, how should they adjust the miles on the machine to best mimic those on the road?

Luke Humphrey, 36, owner and coach of Hanson’s Running in Rochester Hills, Mich., says that runners should take into account a few minor differences when they have to hit the treadmill.

“When you’re on a treadmill, you’re missing the headwind you’d encounter outside,” he says. “You’re not going to have to work quite as hard.”

On the flip side, however, Humphrey points out that without the wind and openness on the road, treadmill runners encounter more humidity indoors. “That’s slightly harder on your body, so it might balance out,” he says.

Sara says that when training for a race, she always puts in time on the road.

“I always do my long runs outside,” she says. “I think it’s important for my body to get used to the changes in terrain and the camber of the road.”

As with anything, each individual must determine how to best use the treadmill to suit their specific training needs, but there are a few guiding principles that can help you get the most out of it.

READ MORE: 5 Coach-Recommended Treadmill Workouts

Tricks of the Trade

Ultrarunner Jackie Palmer, 29, an Atlanta-based, Milestone Sports-sponsored athlete who finished seventh at this year’s Western States 100, puts the treadmill to use when prepping for big, hilly events. A post-doc fellow at Emory University, she says the long climbs she needs to practice aren’t available to her in the city.

“Atlanta has no elevation so I’ll use the treadmill to simulate long, grinding climbs,” she says.

This might mean hill repeats of 5-10 minutes in duration, something Palmer does up to once per week, depending on the race she has on her docket.

“I will try to simulate the climbs I’ll be racing to get the biomechanical simulation I need,” she says. “When getting ready for Georgia Death Race, for instance, I stack books under the base of the front of the treadmill to get to a 25 percent grade.”

Humphrey prefers that his athletes use the treadmill for hill-based workouts rather than very fast repeats.

“With some runners, going too fast on the treadmill can be something of a hazard, or they may worry about flying off the back,” he says. “I have calculators to help my runners figure out how to equate a hill workout to certain miles per hour.”

Other options to get the most of the treadmill include breaking up steady-paced runs into longer interval efforts.

“Instead of a 10-mile run, I’ll have them run five x 2 miles with short rest,” Humphrey explains.

He also finds the treadmill a handy tool for athletes running in particularly adverse weather conditions, like ice or extreme summer heat. “If it’s a specific workout where pace is more important than effort, then the treadmill is an option,” he says. “But for easier runs, I want them to get out to acclimate, especially in the summer.”

The outdoor component even plays a role for members of the New York City-based Mile High Run Club, a treadmill studio that serves up a variety of classes and training programs. Over the summer, the club’s offerings include coached plans in the lead-up to the New York City Marathon.

“Our plans are a mixture of indoor classes, a long run outdoors, and outdoor track work,” says founder and owner Deborah Warner. “There’s a benefit to training outdoors to get used to the conditions, and for long runs, it’s just more fun.”

Once summer and the fall marathon is over, however, many of the Mile High members take to the indoor classes, which vary in duration and intensity.

“If you’re going to run indoors, why not make it purposeful?” Warner says. “We believe that if you incorporate the classes into your training, they will enhance it.”

Warner says that by doing speed work in a group setting on treadmills, no one gets left behind, either.

“More people can then tap into the social aspect of running,” she says. “This is an extension of the lifestyle.”

Sara says that the key to her treadmill running is her attitude. “I’m not at the front of the pack, so maybe I would feel differently if I were,” she says, “but if you have to run on the treadmill, why not embrace it? It’s better than nothing, and if you adjust your expectations, you’ll be just fine.”

READ MORE: 24 Hours on a Treadmill