ACE Personal Trainer Practice Exam

What characteristic defines the fat-free mass in the context of BIA?

1. It consists of less than 50% water

2. It is responsible for the majority of electrical resistance

3. It contains 70-75% water

4. It primarily consists of stored energy

The correct answer is: It contains 70-75% water

The characteristic that defines the fat-free mass, particularly in the context of bioelectrical impedance analysis (BIA), is that it contains 70-75% water. This high water content is significant because it allows for better conductivity of electrical signals, which is essential in BIA assessments. Since fat-free mass includes components like muscle, organs, and bone, which are rich in water, it contributes effectively to the body’s overall water balance and plays a critical role in how electrical impedance is measured. Understanding this property is vital when analyzing body composition, as the water content influences the electrical resistance encountered when a small electrical current is passed through the body during the BIA measurement. This resistance is then used to estimate body composition, making the water content a defining characteristic of fat-free mass.