Building muscle improves your health, reduces injury risk, and, according to a review in the journal Sports Medicine, improves your running performance—which is always motivating. Across 26 studies of endurance athletes, strength-training programs (either plyometrics or heavy weights) boosted fitness, increased efficiency, and reduced runners’ times in 3K and 5K races.

Design your own program by picking six exercises: two for each of your major muscle groups (upper body, core, and lower body), with one working the front side (say, planks) and one the back side (bridges), says Rebekah Mayer, national training manager at Minneapolis-based Life Time Run. Do them two or three days per week. And remember that intense strength-training DVDs or classes don’t always pair well with a running routine, says Sapper—if you do them, leave rest days between hard efforts. For an equipment-free at-home workout, see Nike’s Strength Workout.

Make It Routine

Build it in. Runners that Reichmann and Sapper coach had an easier time staying motivated to incorporate strength moves when they penned them into their training plans. Now, their schedules might say: Run three miles, then do three sets of 15 one-legged squats, mountain climbers, planks, and push-ups. For best results, strength-train later in the same day as your more intense or longer running workouts, allowing a full day of recovery in between hard sessions, Mayer says.

Break it up. Try “exercise snacks”—planks when you get up in the morning, push-ups before you leave for work, lunges on coffee breaks.

Take a class. Don’t want to DIY? Choose a runner-friendly strengthening class that sounds fun, like Pilates, a barre class, or BodyPump. It might cost money, but spending can increase the odds you’ll follow through, Holland says.

Change it up. In about a month, your body will adjust to the routine. “Make it harder—whether it means doing more repetitions, more weight, or different exercises—or you’ll stop seeing results,” Mayer says.