Aerobic Exercise: How Often and for How Long?
Synonyms: also called cardiovascular or endurance training
Components of an exercise session:
An individual exercise session should, ideally, include the following components:
• Warm up: lasting 5 – 10 min., Should include moderate intensity cardio or calisthenics, can be non-specific or activity specific, ie warming up the thigh muscles more on a squat day or before a jog. Warming up prepares the body physically as well as psychologically for the challenge ahead. Although scientific evidence is lacking, anecdotal evidence suggests that warming up can indeed help prevent injuries.
• Conditioning: should last for 20 – 60 min. and includes aerobic training, resistance training, or outdoor sports. This phase is responsible for the maximum benefits derived by the tissues from the exercise session.
• Cool down: Should last for a minimum of 5 to 10 min .; like the warm up phase, this would also include moderate intensity of cardio or muscular exercises. This brings the heart rate to normal in a gradual manner and also prevents sudden fall in blood pressure seen in susceptible individuals.
• Stretching: Should last for 10 min. Again, like the warm up phase, this can be non-specific or specific, ie muscles exercised on that day or that session should be stretched. Stretching prevents muscle soreness (mainly DOMS or delayed onset muscle soreness) seen especially with resistance training by washing way lactic acid build-up during exercise.
FITT principle as applied to aerobic exercise: the word FITT stands for frequency, intensity, the time (duration) and the type of exercise included in the session.
1. Frequency of Exercise
The number of days per week that you exercise is a crucial determinant of fitness as well as general health benefits derived from the sessions. Moderate to vigorous intensity aerobic exercise (> or equal to 60% VO2R) for 1 to 2 session per day is recommended. However, for the physically inactive, lower intensity training for more session per day should be prescribed. Most authorities recommend a low to moderate level aerobic intensity for at least 3 to 5 days a week, if not on most days of the week. A combination of moderate to vigorous activity for 3 days will also suffice in giving health benefits.
2. Intensity of Exercise
To achieve health benefits, a minimum of intensity of moderate levels (40% – 60% of VO2R) is required. However, as stated above, a combination of moderate to severe intensity aerobic activity (> or = 60% VO2R) can result in faster and better results.
3. Time (duration) of Exercise
This signifies the amount of time spent performing exercise either per session, per day or week. Furthermore, time spent in exercising can be calculated by adding up intervals of 10 or 20 min. The principle behind this is the consideration of the amount of calories spent exercising per week. Evidence suggests that burning a total of 1000 calories per week by accumulating exercise over the week results in fitness and health benefits. Most prominent researchers agree to 150 min. of physical exercise per week as the minimum required to derive cardiovascular benefits. This translates to 30 min. of aerobic activity on 5 days of a week.
4. Type of Exercise
Aerobic exercise involving large muscle groups (thighs) are recommended to derive maximum cardiovascular benefits. The type of exercise that can be undertaken can be fast walking, jogging, running, cycling, rowing, aerobics class, dancing, swimming, cross-country skiing. Recreational weekend sporting activities like basketball, tennis or football can also provide a different stimulus to the body.
Conclusion: a moderate to high intensity aerobic exercise for a minimum of 30 min. per day for 3 – 5 days a week is the current recommendation for deriving fitness and health benefits from an aerobic exercise program.