I. Lundblad et al., Worsening of neck and shoulder complaints in humans are correlated with frequency parameters of electromyogram recorded 1-year earlier, EUR J A PHY, 79(1), 1998, pp. 7-16
Citations number
74
Categorie Soggetti
Physiology
Journal title
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY AND OCCUPATIONAL PHYSIOLOGY
The aim was to investigate whether output and electromyogram (EMG) variable
s obtained from an isokinetic endurance test of the shoulder flexor muscles
of 23 women with neck and shoulder problems in a car and truck industry co
rrelated with improvement or worsening of complaints 1 year later. Each sub
ject performed 100 maximal isokinetic shoulder forward flexions at 60 degre
es s(-1). Surface EMG of the trapezius, deltoid, biceps brachii and infrasp
inatus muscles and mechanical output (peak torque) were determined for each
contraction. The EMG was used to determine mean frequency f(mean) and the
ratio between the signal amplitudes of the EMG of the passive relaxation an
d active flexion parts of each contraction cycle (SAR). The subjects also r
ated the degree of fatigue they experienced throughout the test. The magnit
ude of the shift in f(mean) was correlated with whether improvement or wors
ening occurred for complaints in the neck and or shoulders; a significant r
elationship (r(2) = 0.44; P = 0.001) existed between the total frequency sh
ift of the four muscles and the variables measuring improvement in complain
ts. In the multivariate predictions other f(mean) variables and perception
of fatigue were also of significance. The present study would indicate that
a high degree of f(mean) shift correlates with improvement in neck and sho
ulder complaints 1 year later. One possible reason could be that f(mean) re
flects the muscle morphology and/or a pathological situation for the type-1
muscle fibres.