MEASUREMENT BY LASER-DOPPLER FLOWMETRY OF MICROCIRCULATION IN LOWER LEG MUSCLE AT DIFFERENT BLOOD FLUXES IN RELATION TO ELECTROMYOGRAPHICALLY DETERMINED CONTRACTION AND ACCUMULATED FATIGUE

Single-fibre percutaneous laser-Doppler flowmetry (LDF) of the tibiali s anterior muscle was performed continuously for measurement of the mi crocirculation during different blood fluxes. as well as in relation t o different muscle activities and fatigue determined electromyographic ally (EMG). The laser-Doppler power spectrum density function was stud ied in a frequency range of 0-8.2 Hz as representing the blood flow mo st selectively. Reduced blood flow from tourniquet inflation caused a decrease in signal power density, compared to that of intact blood flo w at rest. During postocclusion reactive hyperaemia an increased signa l power was recorded. This reached its maximum within 4.4 (SD 1.88) s after deflation of the tourniquet. The different fluxes were recorded at high sensitivity and disturbances were small. Periods of 1-min stat ic dorsi-flexion of the foot at 10, 20, 30, 40, and 50% MVC (maximal v oluntary contraction) with 1-min rest between were associated with a s ignificant increase in LDF, the recordings obtained during the rest pe riods showing a tendency towards an increase. A decrease in the EMG me an power frequency (MPF) indicated accumulated fatigue. The LDF for th e rest periods that followed upon continuous contractions up to the sa me MVC levels showed a tendency towards an increase but variability wa s large. With further development, these techniques may be useful in t he evaluation of insufficiency of the peripheral circulation.