Feed-forward loop between body composition, strength and performance in older adults.

Frailty syndrome is hypothesized to arise from malfunction in feedback mechanisms among interacting physiological systems. However, empirical evidence to support this hypothesis is not yet available. We present evidence of a feed-forward loop relationship between certain components of the frailty syndrome: body composition, strength and physical performance level. The evidence has been found by performing statistical analysis on measures from 878 females and 588 males aged 60-97, participating in the Rancho Bernardo Study, followed for at least three visits over 12 years. In the analysis, we have used fat mass and lean mass (measured by whole body DXA scans), grip strength (measured by dynamometer) and time to get up and walk a certain distance. The results provide evidence of a feed-forward loop between these variables. The results also suggest that adverse changes in body composition would not only reduce the physical performance and grip strength, but the changes would further result in adverse changes in body composition. Our findings support the hypothesis that feed-forward loops are present between the components of the frailty syndrome at the time of development of frailty, which itself may be a manifestation of dysregulated energetics.