The American College of Sports Medicine and the American Heart Association have put out physical activity recommendations for healthy adults aged between 18 and 65 (25).
The core recommendations are that individuals should aim for a minimum of 30 min on 5 days each week of moderate intensity aerobic exercise (brisk walking is an example).
This can be substituted by vigorous intensity exercise for a minimum of 20 min 3 days each week (jogging is an example). A combination of moderate and vigorous exercise can be used to meet the guidelines. In addition, strength training 2 days a week using the major muscle groups with a load that allows 8–12 repetitions to volitional fatigue is also recommended.
For healthy older adults the recommendations are essentially the same but the addition of balance and flexibility training should also be considered.
Frequently in the research literature when advising / assessing level of physical activity, 150 min / week of moderate intensity physical activity is used as a level to aim for. For both clinical and research purposes this is a useful guide as it is clear and easily remembered.
Although these guidelines give a benchmark, there is a strong dose response rate and doing more is associated with increased benefits (25). The Cancer Research Fund/ American Institute for Cancer Research recommends at least 60 min a day of physical activity. Research findings indicate that the benefits of decreased risk of cancer are more evident at higher levels of physical activity (12,19).
It must be noted, however, that physical activity that does not reach the level of the guidelines is still beneficial (14,15). Bouts of appropriately intense activity of 10 min or more can also count towards daily quota (25). Although episodic accumulation has been shown to improve fitness to the same degree as a continuous session, it has not been firmly established whether equivalent health benefits are also gained (26).
The above is an extract from a paper by Leslie Alford from the University of East Anglia on the impact of regular exercise on our physical and mental health. You can obtained the references by clicking on FULL TEXT.
L. Alford. What men should know about the impact of physical activity on their health. International Journal of Clinical Practice, 2010; 64 (13): 1731