Bioelectrical impedance analysis lacks the precision necessary to detect small changes in fat-free mass during weight loss interventions, as indicated by the absence of observed muscle preservation despite statistically significant improvements in muscle function.

When muscles are trained through repeated resistance exercises, the nervous system gets better at activating more muscle fibers and firing them faster, which makes the muscles stronger without making them bigger. This improved nerve control allows people to lift more or perform better in strength tasks, even when the actual amount of muscle tissue doesn't change enough for simple body scans to detect.