Abstract
The present study aimed to simultaneously
examine the age-related, muscle-specific, sex-specific, and
contractile mode-specific changes in isolated mouse skeletal muscle
function and morphology across multiple ages. Measurements of
mammalian muscle morphology, isometric force and stress (force/
cross-sectional area), absolute and normalized (power/muscle mass)
work-loop power across a range of contractile velocities, fatigue
resistance, and myosin heavy chain (MHC) isoform concentration
were measured in 232 isolated mouse (CD-1) soleus, extensor digitorum
longus (EDL), and diaphragm from male and female animals
aged 3, 10, 30, 52, and 78 wk. Aging resulted in increased body mass
and increased soleus and EDL muscle mass, with atrophy only present
for female EDL by 78 wk despite no change in MHC isoform
concentration. Absolute force and power output increased up to 52 wk
and to a higher level for males. A 23–36% loss of isometric stress
exceeded the 14–27% loss of power normalized to muscle mass
between 10 wk and 52 wk, although the loss of normalized power
between 52 and 78 wk continued without further changes in stress
(P > 0.23). Males had lower power normalized to muscle mass than
females by 78 wk, with the greatest decline observed for male soleus.
Aging did not cause a shift toward slower contractile characteristics,
with reduced fatigue resistance observed in male EDL and female
diaphragm. Our findings show that the loss of muscle quality precedes
the loss of absolute performance as CD-1 mice age, with the greatest
effect seen in male soleus, and in most instances without muscle
atrophy or an alteration in MHC isoforms.
examine the age-related, muscle-specific, sex-specific, and
contractile mode-specific changes in isolated mouse skeletal muscle
function and morphology across multiple ages. Measurements of
mammalian muscle morphology, isometric force and stress (force/
cross-sectional area), absolute and normalized (power/muscle mass)
work-loop power across a range of contractile velocities, fatigue
resistance, and myosin heavy chain (MHC) isoform concentration
were measured in 232 isolated mouse (CD-1) soleus, extensor digitorum
longus (EDL), and diaphragm from male and female animals
aged 3, 10, 30, 52, and 78 wk. Aging resulted in increased body mass
and increased soleus and EDL muscle mass, with atrophy only present
for female EDL by 78 wk despite no change in MHC isoform
concentration. Absolute force and power output increased up to 52 wk
and to a higher level for males. A 23–36% loss of isometric stress
exceeded the 14–27% loss of power normalized to muscle mass
between 10 wk and 52 wk, although the loss of normalized power
between 52 and 78 wk continued without further changes in stress
(P > 0.23). Males had lower power normalized to muscle mass than
females by 78 wk, with the greatest decline observed for male soleus.
Aging did not cause a shift toward slower contractile characteristics,
with reduced fatigue resistance observed in male EDL and female
diaphragm. Our findings show that the loss of muscle quality precedes
the loss of absolute performance as CD-1 mice age, with the greatest
effect seen in male soleus, and in most instances without muscle
atrophy or an alteration in MHC isoforms.
| Original language | English |
|---|---|
| Pages (from-to) | R296-R314 |
| Number of pages | 19 |
| Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
| Volume | 319 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 1 Sept 2020 |
Keywords
- fatigue
- muscle quality
- power output
- sarcopenia
- sex differences