Stretch-shortening cycles protect against the age-related loss of power generation in rat single muscle fibres

Exp Gerontol. 2024 Apr 10:112423. doi: 10.1016/j.exger.2024.112423. Online ahead of print.ABSTRACTAging is associated with impaired strength and power during isometric and shortening contractions, however, during lengthening (i.e., eccentric) contractions, strength is maintained. During daily movements, muscles undergo stretch-shortening cycles (SSCs). It is unclear whether the age-related maintenance of eccentric strength offsets age-related impairments in power generation during SSCs owing to the utilization of elastic energy or other cross-bridge based mechanisms. Here we investigated how aging influences SSC performance at the single muscle fibre level and whether performing an active lengthening prior to shortening protects against age-related impairments in power generation. Single muscle fibres from the psoas major of young (~8 months; n = 31 fibres) and old (~32 months; n = 41 fibres) male F344BN rats were dissected and chemically permeabilized. Fibres were mounted between a force transducer and length controller and maximally activated (pCa 4.5). For SSCs, fibres were lengthened from average sarcomere lengths of 2.5 to 3.0 μm and immediately shortened back to 2.5 μm at both fast and slow (0.15 and 0.60 Lo/s) lengthening and shortening speeds. The magnitude of the SSC effect was calculated by comparing work and power during shortening to an active shortening contraction not preceded by active lengthening. Absolute isometric force was ~37 % lower in old compared to y...

Source: Experimental Gerontology - April 12, 2024 Category: Geriatrics Authors: Makenna A Patterson Avery Hinks Binta S Njai Benjamin E Dalton Emma F Hubbard Geoffrey A Power Source Type: research