Developmental changes in muscle coordination patterns of normal and ab
normal general movements (GMs) are described. GMs were studied simulta
neously with video-recording and polymyography (polyEMG). GMs of norma
l full-term infants gradually lose their neonatally slow and 'writhing
' character, to be turned into the elegant flow of small movements of
'fidgety' GMs at the age of 2-3 months. This transformation coincides
with changes in the polyEMG. Tonic background activity decreases concu
rrent with a reduction in amplitude and duration of phasic bursts. The
coordination between antagonistic muscles does not change, co-activat
ion remains the prevailing pattern. Secondly, preliminary results on h
ealthy preterms (n = 6) are presented. At the examination age of 33-34
weeks postmenstrual age the preterms showed so-called 'preterm' GMs,
which are characterized by variation and graceful complexity. EMG burs
t duration was significantly longer during 'preterm' GMs than during '
writhing' GMs of full-term newborns. The percentage of co-activation d
uring 'preterm' GMs varied considerably. The polyEMG of 'writhing' GMs
of two preterms, who were followed longitudinally, differed from that
of 'writhing' GMs of full-terms. At 'fidgety' age the EMG differences
between preterms and full-terms had disappeared. Finally the first re
sults on abnormal GMs are reported. A synchronized onset of muscle act
ivity in all extremity muscles and 'packaging' of EMG-bursts into subu
nits of 5-8 Hz. seemed to be specific properties of these abnormal GMs
. This could indicate a loss of supraspinal control.