Over the course of the 12-week Body for Life program an individual would get noticeably fitter, so their intensity scale needs to be adjusted over time. This is considered normal.
Common choices include walking or running (perhaps on a treadmill), cycling, swimming, or the use of a rowing machine or cross-trainer. However, exercise classes are generally not suitable, unless they are specifically designed to suit Body for Life.
Source: Wikipedia > Body For Life
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