Plug your numbers into the following equations to determine your lean body weight:

100% – ___ (Fat percentage) = ___ (Lean body mass percentage)

__ (Body weight) × ___ (Lean body mass percentage)= ___ (Lean body weight)

To give you an example, let’s assume one woman determined that her body fat percentage is 23 percent. To calculate this woman’s desired weight for her desired body fat range, you must calculate her lean mass. First, because 23 percent of her body is fat, to determine her lean mass, you simply subtract 23 from 100 for 77,which means that 77 percent of her body is lean body mass.

Then, assuming that her total body weight is 140 pounds (63.5 kg), you use the decimal form of this percentage to derive her ideal lean body weight, as follows:

100% – 23 (Fat percentage) = 77 (Lean body mass percentage)

140 (Body weight) × .77 (Lean body mass percentage)

= 107.8 (Lean body weight)

As discussed, ideal body fat levels for most women are between 18 and 22 percent; the average for a healthy woman today is actually about 25 percent body fat.

So, if you want to determine what your body weight should be for a desired percentage of fat within this healthy range, first subtract the desired percentage of fat from 100 percent, and then divide the lean body weight by the decimal form of this percentage, as follows:

100% – ____ (Desired percent fat) = ____ (Desired lean percent)

____ (Lean body weight) / _____ (Desired lean percent)= _____ (Desired body weight)

Remember that muscle weight increases even though body fat is decreasing.

Body composition and even girth measurements should be evaluated every six weeks throughout your exercise program (see the sidebar Taking Girth Measurements for more information). The results can be motivating, especially if your weight loss is from fat.

Flexibility Assessment

The sit-and-reach test can be helpful in measuring flexibility, specifically of the low back and hamstring muscles. This test is helpful because tension in this area can play a large role in low back pain and muscle tightness.

As one of several fitness tests used to measure flexibility, the sit-and-reach test can be easily reproduced to assess your improvement in this area later. However, this testing technique is limited because it measures flexibility only in the low back and hamstrings. It doesn’t address the flexibility of other joints and muscles in the body.