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The estimation of percent body fat using electrodes is achieved through Bioelectrical Impedance Analysis (BIA). This method works by sending a low-level electrical current through the body and measuring the resistance encountered by the current. Different tissues in the body, such as fat, muscle, and water, conduct electricity at different rates. Since muscle contains more water and is a better conductor than fat, BIA can provide an estimate of body composition based on the measured impedance. The resulting data can then be used to estimate body fat percentage, making this method useful for evaluating overall fitness and health.

In contrast, skinfold measurements use calipers to measure the thickness of skinfolds at various sites on the body, calculating body fat indirectly. Body Mass Index (BMI) is a simple calculation based on height and weight but does not provide a measure of body fat directly. Hydrostatic weighing involves water displacement to determine body density and subsequently estimate body fat percentage, but does not utilize electrical impulses or electrodes.