Rate of force development is Ca 2+ -dependent and influenced by Ca 2+ -sensitivity in human single muscle fibres from older adults

• Published in: Experimental gerontology Vol. 150; p. 111348
• Main Authors: Mazara, Nicole, Zwambag, Derek P, Noonan, Alex M, Weersink, Erin, Brown, Stephen H M, Power, Geoffrey A
• Format: Journal Article
• Language: English
• Published: England 14-04-2021
• Subjects: Rate of force development; Muscle contractility; Calcium sensitivity; Myosin; Aging; Cross-bridge
• ISSN: 1873-6815

Natural adult aging is associated with declines in skeletal muscle performance, including impaired Ca
sensitivity and a slowing of rapid force production (rate of force redevelopment; k
). The purpose of this study was to investigate the relationship between impaired Ca
sensitivity and k
of single muscle fibres from young and older adults. Participants included 8 young (22-35 yrs) and 8 older (60-81 yrs) males who were living independently. A percutaneous muscle biopsy of the vastus lateralis of each participant was performed. Single muscle fibre mechanical tests included maximal Ca
-activated force (P
), force-pCa curves, and k
. We showed a decrease in pCa
in old type II fibres compared to young, indicating impaired Ca
sensitivity in older adults. The k
behaved in a Ca
-dependent manner such that with increasing [Ca
], k
increases, to a plateau. Interestingly, k
was not different between young and old muscle fibres. Furthermore, we found strong associations between pCa
and k
in both old type I and type II fibres, such that those fibres with lower Ca
sensitivity had a slowed k
. This Ca
association, combined with impaired Ca
handling in older adults suggests a potential Ca
-dependent mechanism affecting the transition from weakly- to strongly-bound cross-bridge states, leading to a decline in skeletal muscle performance. Future research is needed to explore the role alterations to Ca
sensitivity/handling could be playing in age-related whole muscle performance declines.