Many of us want to know "how much exercise is do I need?" and probably more to the point is, "how little exercise can I get away with doing, to maintain or improve my overall health and fitness?" (well, I'll at least speak for myself!)
According to the American College of Sports Medicine (ACSM) , who sets the standards for national guidelines on exercise and fitness, they publish a "position stands" with concrete information regarding frequency, intensity and duration of each type of exercise (i.e., cardiorespiratory, strength/resistance, flexibility, endurance, etc). I have summarized their published national guidelines below (note: these have not been updated since 1998; I welcome fitness experts to chime in with newer --published-- information:
Definition of Fitness:
The ability to perform moderate-to-vigorous levels of physical activity without undue fatigue and the capability of maintaining this capacity throughout life.
Aerobic Training
Frequency: 3-5 days/week
Intensity: 55%-90% of max heart rate
Duration: 20-60 minutes of continuous or intermittent exercise (10-minute "bouts", accumulated throughout the day DO COUNT!!)
Bottom line:
Aerobic endurance training fewer than 2 days/week, for less than 10 minutes, is insufficient for maintaining or developing fitness.
Resistance Training
Frequency: 2-3 days/week
One "set" of 8-12 repetitions of each exercise, including 8-10 various forms of exercise for each major muscle group
Flexibility Training
Frequency: 2/3 days/week
Performing both static and dynamic techniques to develop range of motion is ideal
The above information is just quick summary from the two published articles (each includes 14-20 pages!) from the two articles (reference below) that you may view online.
So, now the real question: do you follow any of these recommendations in your weekly/daily lifestyle currently? If so, is it religiously or sporadically, or somewhere in between?
[Source: POSITION STAND, ACSM
The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults, June 1, 1998]
[Source: Circulation
The American College of Sports Medicine and the American Heart Association Physical Activity and Public Health: Updated Recommendation for Adults http://circ.ahajournals.org for online version of journal article]