Residual Force Enhancement of the Knee Extensors in Older Adults Is Not Related to Alterations in Muscle Architecture

1,2 Geoffrey A. Power, 2 Demetri P. Makrakos, 2 Charles L. Rice and 2 Anthony A. Vandervoort 1 Human Performance Laboratory, University of Calgary, Calgary, AB, Canada 2 Canadian Centre for Activity and Aging, The University of Western Ontario, London, ON, Canada Corresponding author email: [email protected] SUMMARY Young and old adults experienced a similar level of residual force enhancement (RFE) following a conditioning stretch of the knee extensors. There was greater RFE, and greater passive force enhancement (PFE) at long vs. short muscle lengths in both groups. Fascicle length and pennation angle changes of the vastus lateralis following stretch did not contribute to RFE in either group. The stretch amplitude may not have been large enough to engage sufficient passive force transmitting elements which has been shown previously to contribute to greater RFE in older adults.