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Hydrostatic weighing is a technique used to determine an individual's overall body density. The weight of the individual is measured when their body is completely submerged in water. Because the volume of air in the respiratory system affects the measured underwater weight, the individual must exhale completely before entering the water. However, residual volume, the volume of air that always remains in the respiratory system, must also be accounted for.By comparing an individual's in-air weight to their underwater weight, their total body volume can be determined. The density of the body D_b excluding any air in the respiratory system is calculated with the in-air mass of the individual m_air, the individual's total body volume V_total, and an estimate of residual volume V_res by:
Db=mairVtotal-VresEquation 1Body density can be used to calculate an individual's body fat composition, the percentage of total body mass that is made up of fatty tissue. Human fatty tissue has an average density of 0.9 kg/L, and the density of water is 1 kg/L. The acceleration due to gravity is 10 m/s².
Adapted from Siri, WE, Body composition from fluids spaces and density. Nutrition 1956 Springer Nature.
-Fatty tissue has a lower electrical conductivity than lean (non-fat) tissue. This property allows body fat content to be estimated by modeling the tissue between two points as a single resistor. For the same amount of current entering the body, relatively high body fat content would be indicated by:

Question

Passage
Hydrostatic weighing is a technique used to determine an individual's overall body density. The weight of the individual is measured when their body is completely submerged in water. Because the volume of air in the respiratory system affects the measured underwater weight, the individual must exhale completely before entering the water. However, residual volume, the volume of air that always remains in the respiratory system, must also be accounted for.By comparing an individual's in-air weight to their underwater weight, their total body volume can be determined. The density of the body D_b excluding any air in the respiratory system is calculated with the in-air mass of the individual m_air, the individual's total body volume V_total, and an estimate of residual volume V_res by:

Db=mairVtotal-VresEquation 1Body density can be used to calculate an individual's body fat composition, the percentage of total body mass that is made up of fatty tissue. Human fatty tissue has an average density of 0.9 kg/L, and the density of water is 1 kg/L. The acceleration due to gravity is 10 m/s².
Adapted from Siri, WE, Body composition from fluids spaces and density. Nutrition 1956 Springer Nature.
-Fatty tissue has a lower electrical conductivity than lean (non-fat) tissue. This property allows body fat content to be estimated by modeling the tissue between two points as a single resistor. For the same amount of current entering the body, relatively high body fat content would be indicated by:

Quizplus · Accepted Answer

11ecba2d_12f5_b58b_a3bf_53b05f75ec8c_MD0008_00 Electrical conductivity is the measure of how easily a current can move through a material, and it is inversely proportional to electrical resistance. The question states that fatty tissue is less conductive than lean tissue; in other words, fatty tissue is more resistive. Therefore, an individual with a relatively high body fat content will have a relatively high resistance. The question also states that the current entering the body is constant. Current is the movement of electric charges, and electric charge is always conserved; it cannot be created or destroyed. Because current cannot be gained (increased) or lost (decreased) across a resistor, the amount of current entering and exiting a resistor is always the same (Choices A and B). Voltage is the difference in electric potential between two points that drives the movement of electric charges. Ohm law describes the voltage V across a resistor, which is the product of the current I and the resistance R: 11ecba2d_12f5_dc9c_a3bf_3fd335c4a028_MD0008_00 Therefore, the voltage measured across the resistor is proportional to the resistance, and a high body fat content (high resistance) in an individual will be indicated by a high voltage between two points (Choice C). Educational objective: The current entering and exiting a resistor remains the same because electric charge is always conserved. The voltage across a resistor is the product of resistance and current (V = IR). Therefore, tissues with a higher resistance will have a higher voltage across them for the same amount of current.

Passage Hydrostatic Weighing Is a Technique Used to Determine an Individual's