Ca2+ dependency of limb muscle fiber contractile mechanics in young and older adults.

Ca2+ dependency of limb muscle fiber contractile mechanics in young and older adults. Am J Physiol Cell Physiol. 2020 Apr 29;: Authors: Teigen LE, Sundberg CW, Kelly LJ, Hunter SK, Fitts RH Abstract Age-induced declines in skeletal muscle contractile function have been attributed to multiple cellular factors, including lower peak force (Po), decreased Ca2+ sensitivity, and reduced shortening velocity (Vo). However, changes in these cellular properties with aging remain unresolved, especially in older women, and the effect of submaximal Ca2+ on contractile function is unknown. Thus, we compared contractile properties of muscle fibers from 19 young (24±3 years; 8 women) and 21 older adults (77±7 years; 7 women) under maximal and submaximal Ca2+ and assessed the abundance of three proteins thought to influence Ca2+ sensitivity. Fast fiber cross-sectional area was ~44% larger in young (6,479±2,487 µm2) compared to older adults (4,503±2,071 µm2, P<0.001), which corresponded with a greater absolute Po (young = 1.12±0.43 mN, old = 0.79±0.33 mN, P<0.001). There were no differences in fast fiber size-specific Po, indicating the age-related decline in force was explained by differences in fiber size. Except for fast fiber size and absolute Po, no age or sex differences were observed in Ca2+ sensitivity, rate of force development (ktr), or Vo in either slow or fast fibers. Submaximal Ca2+ depressed ktr and Vo, but the effects were...
Source: Am J Physiol Cell Ph... - Category: Cytology Authors: Tags: Am J Physiol Cell Physiol Source Type: research