Evaluation of the Reproducibility of Jumping Mechanography

Sarcopenia, the age-related decline in muscle mass and function (widely recognized as "frailty"), is increasingly being appreciated, primarily in the research environment. Interventions to prevent or treat sarcopenia can be anticipated to reduce falls, fractures and thereby to facilitate independence and improve quality of life for older adults. Unfortunately, there is no current consensus definition of sarcopenia, thereby impeding clinical recognition and treatment. It has been advocated that low appendicular (arm and leg) lean mass, as measured by DXA, be utilized as a clinical diagnostic tool to define sarcopenia. While such an approach is possible, however, muscle strength loss is more rapid than mass loss, indicating deterioration of muscle "quality." Muscle quality may be affected by changes at the neuromuscular, cellular or subcellular levels; parameters not detected by measuring mass alone. Clearly, tools evaluating muscle performance, not simply mass, are needed to optimally identify, and subsequently monitor, treatment of older adults with sarcopenia. While current tests of muscle power/function (e.g., chair-rising, self-selected gait velocity, etc.) do correlate with functional limitation in older adults, these existing tests have limitations in that they cannot be performed in all people, may have "yes/no" results rather than a continuous scale and may not be highly precise. Thus, improved muscle function assessment tools are needed, both clinically and in research venues. Jumping mechanography is very likely one such methodology.