Stretch-shortening cycles protect against the age-related loss of power generation in rat single muscle fibres.
Exp Gerontol
; 190: 112423, 2024 Jun 01.
Article
em En
| MEDLINE
| ID: mdl-38608790
ABSTRACT
Aging 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 active lengthening prior to shortening protects against age-related impairments in power generation. Single muscle fibres from the psoas major of young (â¼8 months; n = 31 fibres) and old (â¼32 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 â¼37 % lower in old compared to young rat single muscle fibres, however, when normalized to cross-sectional area (CSA), there was no longer a significant difference in isometric force between age groups, meanwhile there was an â¼50 % reduction in absolute power in old as compared with young. We demonstrated that SSCs significantly increased power production (75-110 %) in both young and old fibres when shortening occurred at a fast speed and provided protection against power-loss with aging. Therefore, in older adults during everyday movements, power is likely 'protected' in part due to the stretch-shortening cycle as compared with isolated shortening contractions.
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Base de dados:
MEDLINE
Assunto principal:
Envelhecimento
/
Fibras Musculares Esqueléticas
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Força Muscular
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Contração Muscular
Limite:
Animals
Idioma:
En
Revista:
Exp Gerontol
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Canadá