Note: Before beginning any exercise program consult with your physician.
Of course there is no set formula for exercise. And "exercise" encompasses a wide range of activities from walking to high-impact aerobics, from jumping rope to punching a speed bag, from ping-pong and bowling to soccer and football. We would also include Yoga, Pilate's Exercises, Calisthenics, etc.
Some of the most valuable exercise is "unprogrammed," just incorporated into the daily routine. Examples of this are short walks to the store, walking in and around the workplace, using stairs over elevators, and doing domestic chores. All of these tasks are also opportunities.
In general, exercise should be viewed as we do food groups. Try to incorporate on a regular basis the following "food groups" of exercise:
Aerobic - High or low impact depending on age and general physical condition.
Strength - Generally isotonic is preferred to isometric. In isometric, force is applied to an immobile resistance. In isotonic, force is applied to a resistance that moves, such as weights or springs.
Stretching - This is perhaps best exemplified by Hafta (vs. meditative Yoga). Although there are many stretching exercises.
In designing an exercise program, formulate a plan that can be adapted to fit a lifetime. Mix it up. Avoid boredom.
Like food groups, substitute different items in the same "exercise group." Jumping rope or just hopping on one foot can be substituted for the treadmill. A hike is another option. Strength building can involve weight lifting or it can use your own weight as in push-ups. In general, many repetitions of light weight is preferred to fewer repetitions of heavy weights. This will build strength rather than bulk.
Remember, match the level of exercise to age and general physical condition. Even a very elderly, frail person may be able to exercise with two pound dumbbells, or maybe just lifting the weight of the arms.
To determine how vigorous to do aerobics for your age click here: RECOMMENDED HEART RATE