Bridging the gap between serum biomarkers and biomechanical tests in musculoskeletal ageing

Musculoskeletal ageing is a major public health interesting and strain due to the significant demographic modifications in the population, and it is linked to high risk of falls, loss of autonomy in elderly individuals and institutionalization with small health outcomes. Thus, this pathological status is related to high morbidity and health care rates. Bone mass and muscle mass and strength increase during late adolescence and early adulthood but start to reduce noticeably from the fifth decade of life and are closely linked. Preclinical and clinical data strongly support the muscle-bone cross-talk showing the presence of many tissue-specific factors released by the muscle that modulate bone, such as insulin-like growth factor-1 (IGF- 1), IL-6, IL-15, myostatin and irisin. Bone and muscle tissues were increasingly recognized as endocrine target organs and endocrine organs themselves, interacting through paracrine and endocrine signals. It is then plausible that laboratory parameters could be involved in sarcopenia and osteoporosis diagnosis and treatment monitoring. This narrative review raises the possibility of whether this poor correlation between different muscle/lean mass assessment methods and muscle function tests could suggest that each parameter evaluates different aspects of "muscle status" or "muscle quality". If this is true, no one test can be used to assess muscle status but rather a battery of tests is necessary for a comprehensive assessment. More research is required to provide information for researchers to optimally design studies by using the muscle assessment method that is best associated with selected specific outcomes.