What is the minimum number of days recommended for improving your cardiovascular fitness?

The American College of Sports Medicine (ACSM) has updated its position stand on the quantity and quality of exercise to maintain cardiorespiratory and muscular fitness. The revised ACSM guidelines include for the first time a recommendation for flexibility training as a component in maintaining fitness in addition to aerobic and strength training exercises.

The ACSM position stand is published in the June 1998 issue of Medicine & Science in Sports & Exercise (vol. 30, no. 6). The 17-page position stand also provides the rationale and supportive research for the recommendations. The following information highlights the ACSM recommendations for exercise in healthy adults.

Cardiorespiratory Fitness and Weight Control

To maintain cardiorespiratory fitness and weight control, the recommendations state that aerobic exercise should be performed three to five days a week for 20 to 60 minutes at an intensity that achieves 55 to 90 percent of the maximum heart rate and 40 to 85 percent of the maximum oxygen uptake reserve. In place of one 20- to 60-minute session on a given day, the recommendations state that two to six 10-minute periods of aerobic activity throughout the day can be used to fulfill the requirements for the amount of exercise.

Lower-intensity exercise is recommended for persons who are unfit. Lower-intensity exercise should be performed for 30 minutes or more. Persons training at higher levels should exercise for at least 20 minutes. Moderate-intensity exercise for a longer duration is recommended for most adults.

Muscular Strength

According to the recommendations, resistance training should be a part of a fitness program and of sufficient intensity to enhance muscular strength and endurance and to maintain a fat-free mass. One set of eight to 10 exercises that work the major muscle groups should be performed two or three days a week. The guidelines advocate for most persons eight to 12 repetitions (or to a near-fatigue level) of each exercise. Persons who are older or frail may benefit from 10 to 15 repetitions.

The recommendations for resistance training are based on three factors: a practical amount of time to perform resistance training, the degree of training that results in improved muscular strength and endurance, and the suitability of the level of resistance training for most adults. With respect to the amount of time, the position stand notes that higher dropout rates occur when more than 60 minutes is required to complete a session. A previous study revealed that only 20 minutes is required to complete one set of weight-training exercises, whereas 50 minutes is required to complete three sets. While more frequent training and additional sets and repetitions may produce larger gains in strength, the difference in improvement is usually small in the average healthy adult, plus the average adult does not have the same goals as an athlete. In addition, more intense resistance training may increase the risk of orthopedic injury or a cardiac event in middle-aged and older participants.

Flexibility Training

The recommendations state that flexibility exercises two or three days a week should be incorporated into the fitness program. At least four repetitions per muscle group should be completed at each session. Stretching exercises should mobilize the major muscle and tendon groups and may include static, proprioceptive neuromuscular facilitation and ballistic techniques.

With the static technique, the tendons and muscles are slowly stretched and the stretched position is held for a period of time. Static stretches should be held for 10 to 30 seconds. Proprioceptive neuromuscular facilitation stretching consists of alternating isometric muscle contraction and passive stretching. This technique is sometimes described as active/assisted, contract/relax or hold/relax. Proprioceptive neuromuscular facilitation stretching should be maintained for a six-second contraction, followed by a 10- to 30-second assisted stretch. Ballistic stretching involves repetitive bouncing motions in which the tendon is rapidly stretched and relaxed.

The Physical Activity Guidelines issued by the U.S. Department of Health and Human Services recommend at least 150 minutes per week of moderate-intensity physical activity—think of it as 30 minutes, five days a week—for all adults, even the elderly and disabled. However, you don't have to do all 30 minutes in a single daily session. In fact, the newest guidelines allow you to count all moderate intensity physical exertion throughout the day, even if it's just a few minutes at a time.

You can also reach your goal by performing chunks of exercise in 10- or 15-minute blocks throughout the day. For example, do 10 minutes before breakfast, 10 minutes during your lunch break, and another 10 minutes after dinner. Or do 15 minutes in the morning and 15 minutes in the afternoon. If you're just starting out, gradually build up to 150 minutes a week.

If you're already exercising and fit, you can cut your exercise time in half—to just 75 minutes a week—by doing vigorous exercise instead of moderate. Generally, that would amount to 25 minutes, three days a week. Or, you can perform an equivalent combination of the two intensities, with each minute of vigorous-intensity activity equivalent to two minutes of moderate-intensity activity.

If you're able to do more, that's even better. The Physical Activity Guidelines specify that you can derive more health benefits by boosting your workout time from 150 minutes a week to 300. But the most important thing is that you do something.

To learn more about the benefits of cardio exercise as well as many options for taking part in cardio, read Cardio Exercise from Harvard Medical School.

Image: Halfpoint/Getty Images

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

How long does it take to improve cardiovascular fitness?

How many days a week should you exercise to get cardiovascular fit?

What are the recommended minimums for cardiovascular exercise?

What is the minimum number of days a person needs to participate in cardiovascular exercise to achieve Health benefits?