MICROCIRCULATION IN THE UPPER TRAPEZIUS MUSCLE DURING VARYING LEVELS OF STATIC CONTRACTION, FATIGUE AND RECOVERY IN HEALTHY WOMEN - A STUDYUSING PERCUTANEOUS LASER-DOPPLER FLOWMETRY AND SURFACE ELECTROMYOGRAPHY
Se. Larsson et al., MICROCIRCULATION IN THE UPPER TRAPEZIUS MUSCLE DURING VARYING LEVELS OF STATIC CONTRACTION, FATIGUE AND RECOVERY IN HEALTHY WOMEN - A STUDYUSING PERCUTANEOUS LASER-DOPPLER FLOWMETRY AND SURFACE ELECTROMYOGRAPHY, European journal of applied physiology and occupational physiology, 66(6), 1993, pp. 483-488
Microcirculation in the upper portion of the trapezius muscle was meas
ured percutaneously by continuous laser-Doppler flowmetry (LDF) during
two 10-min series of alternating 1-min periods of static contraction
and rest determined electromyographically (EMG). Stepwise increased co
ntraction was induced by keeping the arms straight and elevated at 30,
60, 90 and 135-degrees, which was repeated with a 1-kg load carried i
n each hand. Thereafter, fatigue and recovery were recorded while the
subject kept her arms straight and elevated at 45-degrees carrying the
1-kg hand load as long as possible, followed by rest with arms hangin
g and no load. A group of 16 healthy women of different ages was studi
ed. Signal processing was done on line using a 386 SX computer. The LD
F- and root-mean-square (rms) EMG signals were normalized. Spectrum an
alyses of EMG mean power frequency (MPF) and median spectrum frequency
were performed. The rms-EMG increased significantly with an increase
in the calculated shoulder torque (r = 0.75). Accumulated local fatigu
e was indicated by a decrease in MPF with increased shoulder angle and
added load (r = -0.54). Blood flow increased with increased shoulder
angle (r = 0.82, with hand load r = 0.62) and with increased shoulder
torque (r = 0.72), and also showed a significant increase with increas
ed EMG activity (r = 0.74). The LDF showed a negative correlation to M
PF (r = -0.67), with increased values when MPF was lowered. During the
endurance test, a moderate increase of LDF occurred which reached its
maximum during the 1st min of recovery. Then, a slow return to the ba
se level was recorded. The ability to increase the flow in the microci
rculation with increasing muscle load was not diminished with age.