The American College of Sports Medicine has released new recommendations about how much and what types of exercise adults should get based on current scientific evidence.

People should engage in 150 minutes of moderate intensity cardiorespiratory exercise per week, either by working out five days a week at a moderate level of intensity or engaging in less frequent, more intense workouts, according to the recommendations made in the position stand “Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise.” The position stand's purpose is to offer health-and-fitness professionals scientific, evidence-based recommendations that help them customize exercise prescriptions for healthy adults.

Each major muscle group should be trained two or three days per week. During resistance training, doing a lower number of repetitions, between eight and 15, improves strength and power, whereas doing 15 to 20 repetitions improves muscular endurance, the guidelines say.

The ACSM recommends stretching several times each week to improve range of motion as well as doing 20 to 30 minutes of neuromotor exercises, which should include balancing and coordination exercises in addition to multifaceted activities, such as tai chi and yoga, two or three days per week.

The position stand also dispels a few myths about working out. Pedometers do not accurately measure physical activity and should not be used as your only measure of physical activity, it says, and although exercising does help prevent heart disease, it is still possible for active adults to have heart problems. The guidelines also warn of the dangers of sedentary behavior, saying that even if people meet the exercise recommendations, they could still be at risk for health problems if they sit for long periods of time.

“It is no longer enough to consider whether an individual engages in adequate amounts of weekly exercise,” says Carol Ewing Garber, chair of the writing committee. “We also need to determine how much time a person spends in sedentary pursuits, like watching television or working on a computer. Health-and-fitness professionals must be concerned with these activities as well.”