subclinical may indicates early stage or a mild form of a medical condition, without obvious symptoms yet.. spasm normaly comes due to overuse, secondary to trauma, overactive (with/without increase emg), etc.. its a clinical findings..

eg, spasm of upper trap may due to trauma / whiplash to cervical in accident, may due to overactive of it during shoulder elevation secondary inhibition of mid/lower trap of scapula. morover, stress, computer work, posture of sitt n std also affect upper trap's property.. gentle stretch on spasm muscles will ease spasm n pain; improper streching may induce more spasm s it triggers the protective mechanism, which further increase 'tightness' due to spasm.

upper n lower cross syndrome (UCS/LCS) happens when there is contrary tightness (spasticity) and weakness between agonist n antagonist muscles / muscle groups secondary to muscles imbalances. UCS/LCs only is defined when someone realy shows d typical posture/ do develop particular weakness n tightness..

nutshell, spasm is more likely protective mechanism, which improper stretching may induce more pain n spasms. tightness/ spasticity in UCS/LCS needs stretching accordingly to enhance proper corecttion of the UCS/LCS.