Worsening of neck and shoulder complaints in humans are correlated with frequency parameters of electromyogram recorded 1-year earlier

Citation
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
ISSN journal
03015548 → ACNP
Volume
79
Issue
1
Year of publication
1998
Pages
7 - 16
Database
ISI
SICI code
0301-5548(199812)79:1<7:WONASC>2.0.ZU;2-J
Abstract
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.