As a runner you know that a program that incorporates various distances, paces, and surfaces helps you perform your best. What you may not realize is that the same holds true with the company you keep—or don't keep—on the run. Whether you'd rather gab away the miles with pals or be alone in your own thoughts, runners who are strictly social butterflies or lone rangers are at a disadvantage. "Being set in an introverted or extroverted running pattern can limit your experiences and prevent you from growing as a runner," says Michelle P. Maidenberg, Ph.D., M.P.H., a psychotherapist who works with athletes. Mixing things up and seeking out—or passing up—companionship can make you a more balanced runner.

SOLO PRACTICE
Between chirping cell phones, pinging e-mails, chatty coworkers, and rowdy kids, it can be tough finding moments of peace and quiet in your day. Running alone can allow you to hit the mute button on the world (especially if you leave the gadgets behind) and take full advantage of exercise's stress-busting benefits. "Running alone can be a meditative experience where you get to really think and concentrate or completely clear your mind and zone out," Maidenberg says.

There are performance benefits as well. When you're on your own, you can pay better attention to your form, breathing, and pace, says Brendan Cournane, a Chicago-based running coach. "It's easy to choose to run with a group at a casual pace, but doing that all the time can keep you from reaching your running potential," he says. "And if you always run with a group that's too fast, it can push you into doing more than you should." Running by yourself is especially important if you're coming back from injury and need to listen to your body to avoid another setback.

Also, solo training makes you self-sufficient for race day: You'll feel comfortable finding—and sticking to—a pace on your own without relying on a partner, and you'll get practice recognizing when your body needs hydration and fuel.

GROUP LOVE
One of the biggest gifts running partners give you is accountability: It's hard getting up at 5 a.m. to run, especially if it's raining and you stayed up late watching Leno or The Daily Show. But if you know that a buddy is waiting for you, you'll have extra motivation to climb out of bed, Cournane says. And it works on the run, too: A partner can keep you from slipping off pace or cutting a run short.

This positive peer pressure even works on a subconscious level—thanks to a concept called "social facilitation," says Cindra Kamphoff, Ph.D., a sports psychology consultant at Your Runner's Edge. It was first discovered with cyclists—they had faster times when racing against someone else versus doing a time trial on their own. The same holds true with runners. "When you run with others, you tend to give more effort," she says. "You get caught up in the pace, and you might not recognize how fast you're going."

Pairing up can also encourage you to branch out. "You learn more about how other people train and what they're doing, and it can inspire you to do something different," Kamphoff says. "It can open up your mind to trying new distances, races, or types of workouts."

Many beginners are solo runners, says Cournane, because they feel overwhelmed or intimidated by running with others. He suggests dipping your toe into the running community by pairing up with just one other person. Before you go, talk about your goals, especially pace. If your friend is faster, schedule your running date for a day he'll be doing an easy, recovery day. That way you can enjoy the run without worrying about keeping up or holding him back.

THE RIGHT BALANCE
With so many advantages to solo and group running, it's smart to do both. A loner might want to pair up with a slightly faster friend for speedwork or join others for company on long runs. And a social runner could split off from her relaxed group in order to do a quality workout designed for her individual goals.

That's what Kamphoff did when preparing for September's Omaha Marathon. Although she prefers to log miles with her running group, she did solo runs in order to work on her mental game. "You have to practice letting go of the inner chatter that can get in the way of what you want to accomplish," she says. "And that's something you have to do on your own." On race day, Kamphoff was able to reframe her negative thoughts. She won the women's division in 3:05.