Key result
Neonatal rat twitch time delays to 16-18 days, with myosin composition correlating to shortening velocity.
Why the study?
The relationship between contractile properties and myosin heavy chain composition in motor units of neonatal rat soleus muscles was not fully characterized.
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Neonatal rat muscle data extend myosin-velocity correlations; leaves open translation to human cardiac maturation.
Nelson et al. (1994) studied this question. Developmental age (16-18 days) vs. Developmental age (7-8 days) was evaluated on Unloaded shortening velocity (Vus) and twitch time to peak force (TTP). In neonatal rats, twitch time to peak force shifted from 7-8 days to 16-18 days, and myosin heavy chain composition correlated with unloaded shortening velocity of individual motor units.
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