Which of the following is NOT considered a standard site for skinfold measurements?

The lower back is not considered a standard site for skinfold measurements in body composition assessments. Standard sites for skinfold measurements are chosen based on their consistent associations with body fat levels and ease of access. Commonly accepted standardized sites include the triceps, abdominal, and medial calf, as these locations have established protocols and reliable measurement techniques that can be used across various populations. The lower back, while it can be measured for body composition in certain contexts, does not have the same level of standardization and validation in the context of skinfold assessment, which is why it's not included in the typical list of standard sites. This is vital for ensuring consistency and comparability in body fat measurements across different individuals and studies.