This is the 12303rd most frequent Polish word.
mięśniowego
"Mięśniowego" means "muscular" or "related to muscles."
The word 'mięśniowego' is an adjective derived from 'mięśnie' (muscles), used here to describe the type of system being discussed.
Ćwiczenia jogi wspomagają rozwój układu mięśniowego.
Yoga exercises support the development of the muscular system.
'Mięśniowego' serves as an adjective modifying the noun 'osłabienia', indicating that the weakening pertains to the muscles.
W wyniku choroby doszło do osłabienia mięśniowego.
As a result of the illness, muscular weakness occurred.
Here 'mięśniowego' is used to qualify 'układu', specifying that the system in question is muscular.