time per week is considered the minimum (1). Depending on the intensity of the exercise, 300
calories may require anywhere from thirty to forty five minutes of exercise. Unconditioned
individuals can obtain similar results by performing several shorter workout sessions per day (i.e.
ten minutes three or more times per day) as with performing the entire exercise session all at
once (4). This strategy may be useful for busy individuals or those who are just beginning an
exercise program.
Detrained individuals may not be able to exercise for 20’ continuously when they start
their exercise program. In this case, a modified type of interval training should be used. A total of
20-30’ can be performed by alternating periods of exercise (of several minutes duration, whatever
the individual is capable of) with periods of total rest (to allow for recovery). As fitness improves,
longer periods of exercise will be possible and less rest required until a full 20’ can be done without
stopping.
At this point, exercise time can be increased at each workout by a minute or two until the
final time goal is reached. Longer durations of exercise will burn more calories and may be more
beneficial for fat loss. Total caloric expenditure can also be increased by keeping duration the
same and exercising at higher intensities. For beginners, duration should be increased before
increasing intensity to avoid injury and burnout.
Intensity and duration: an inverse relationship
There is an inverse relationship between intensity and time of aerobic activity. High
exercise intensities (especially above LT) limit time. High workout times generally mandate
lower exercise intensity. As discussed in chapter 22, individuals seeking fat loss should find the
combination of intensity and duration which allows them to maximize caloric expenditure.
Type
In general, the type of activity done is less important than the previous three variables.
Ultimately, the best aerobic activity is that which an individual enjoys and will do regularly.
Bodybuilders should avoid high impact aerobic activities such as running as their higher body
mass may increase the chance of joint injury.
Aerobics classes are generally not encouraged for bodybuilders because it is relatively
more difficult to keep heart rate at low intensities. Endurance athletes should perform the
majority of their training with the same type of activity they will compete in (i.e. cyclists should
cycle, runners should run). The topic of cross-training is beyond the scope of this book.
The combination of the above principles will differ for different goals. The amount of training
needed for general fitness differs from that needed for a pre-contest bodybuilder or an endurance
athlete. Table 1 shows a sample aerobic progression for an untrained individual.