No differences in oxygenation in the forearm and shoulder of patients with work-related muscle pain and healthy subjects during a low-load sustained contraction

• A frequently ascribed symptom associated to work-related muscle pain (WRMP) is muscle fatigue. Studies investigating oxygenation and hemodynamics in association to fatigue development in the muscles of patients with WRMP are sparse. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. In this study we applied near-infrared spectroscopy (NIRS) and electromyography (EMG) to investigate oxygenation, hemodynamics and muscle activity in the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP and healthy controls. Eighteen patients with diffuse neck-shoulder-arm pain and 17 controls (matched in age and sex) were equipped with NIRS and EMG probes. After determination of maximal voluntary contraction (MVC) a sustained contraction of 15% MVC was performed with a cutoff for the maximum time of 12 min. Variables generated were StO2% and HbT from NIRS and RMS%max and MPF from EMG during the contraction. T tests and Mann-Whitney tests were used for analyzes of differences in MVC and endurance times. Full factorial repeated measures analyses of variance (ANOVA) were used to assess differences between patients and controls in NIRS and EMG parameters over time. Results showed no differences in MVC between patients and controls. We found, however, a shorter endurance time for patients compared to controls. There were no significant differences in StO2%, HbT, RMS and MPF responses during contraction between groups for the ECR. For the TD there was a group effect for StO2% with patients showing a lower level at rest and throughout the contraction. For the ECR and TD oxygenation, hemodynamics, RMS and MPF there were no straightforward differences between patients and controls that could explain the differences in endurance time. Therefore, we conclude that the shorter endurance time seen in the present study was not measurable by physiological indicators investigated in this group of patients.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

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