Age-related Differences in Rapid Torque Production: Influence of Muscle Size, Quality, Architecture, and Activation

Rapid torque production is important for many activities of daily living and has been shown to decrease in older adults. The purpose of the present study was to examine the age-related differences in the rate of torque development (RTD) and the influence of muscle size (CSA), muscle quality (EI), pennation angle (PA), fascicle length (FL) and the rate of electromyographic rise (RER) on RTD. Ultrasonography was used to examine muscle architecture and RTD and RER were examined with surface electromyography during a maximal isometric strength assessment in 35 young and 22 older men. Absolute peakRTD (aRTDpeak) and PA were lower and EI was greater in the older men (P<0.05), with no differences in CSA, FL and RER (P>0.05). With groups combined, CSA, EI, and PA were related to aRTDpeak (P<0.05). These findings may suggest that the age-related reductions in aRTDpeak may be related to alterations in muscle quality and PA. iv ACKNOWLEDGEMENTS I would first like to thank my advisor, Dr. Eric Ryan, for your patience, wisdom, and help with all aspects of this thesis. I have learned so much about the writing process and what it takes to be a productive researcher. I would also like to thank my committee members, Dr. Abbie Smith-Ryan and Mr. Eric Sobolewski, for taking the time to review my document and for providing invaluable insight and advice. Finally, I would like to thank Gupper, Ed, Andrew, Craig, and Brennan for all your help both in and out of the lab.