Confused by all the fitness apps at the Apple store, and wondering which one to try?

A new study from the University of Florida evaluated 30 popular free fitness apps for the iPhone to determine which ones fare the best, when held to the American College of Sports Medicine guidelines for physical activity, the Washington Post reports.

In scoring the apps, researchers looked at everything from warm-ups, cool-downs, and stretching to safety and assigned a score for aerobic exercise, strength/resistance, and flexibility.

More than half the apps met some of the criteria for aerobic exercise, 90 percent for some strength/resistance, but many fell short in flexibility. In all, two-thirds did not meet any flexibility criteria, the researchers wrote in the Journal of Medical Internet Research.

Only one app — the Sworkit Lite Personal Workout Trainer — met more than half the criteria from the guidelines. Others that scored well: 7 Minute Workout, StrongLifts, Running for Weight Loss, JEFIT Workout, FitnessBuilder, C25K-5K Trainer Free, Ultimate Fitness Free, Nike+Training Club, and BodySpace.