LOW-INTENSITY LASER IRRADIATION (830 NM) REDUCES SKIN BLOOD-FLOW IN HUMANS

Low-intensity (therapeutic) laser therapy (LILT) has become a popular therapeutic modality for use by physiotherapists in the clinical manag ement of a wide variety of conditions, including the promotion of woun d repair and as an hypo-algesic agent. Nevertheless, the scientific da ta in support of the continued application of lasers in the clinic rem ains sparse, although recent studies have demonstrated a number of qua ntifiable biological effects of low-intensity laser, including laser-m ediated increases in human median nerve conduction latency in vivo. In the present study, the effect of irradiation with low-intensity laser (1.5 J cm(-2); 830 nm) on forearm skin blood flow in humans has been assessed using a laser Doppler flowmeter: (1) under resting conditions ; (2) with concomitant measurement of antidromic median nerve conducti on latency; and (3) after raising skin blood flow by immersion of the arm in water at 45 degrees C for a period of 10 min. Under resting con ditions and with concomitant measurement of nerve conduction latencies , irradiation at the parameters stated produced no dramatic change in the measured red cell flux signal (RCFS). However, when the latter was raised by pre-heating the limb, laser irradiation effected a signific ant reduction in measured flux when compared to placebo at 20 min post irradiation. Such an effect of LILT indicates a laser-induced reductio n in skin blood flow. These findings may have importance to our furthe r understanding of laser's effects in vivo and its putative clinical e fficacy.