Evidence for the effect of laser phototherapy on lateral epicondylalgia (tennis elbow)
Evidence for the effect of laser phototherapy on lateral epicondylalgia (tennis elbow). Laakso L School of Physiotherapy and Exercise Science, Griffith University, Gold Coast, Australia Previous studies have demonstrated disparate results for the effect of laser phototherapy on tennis elbow pain; and a clear mechanism of effect remains elusive. To investigate a possible descending mechanism of effect, two subjects with tennis elbow were recruited (Study 1: female aged 49yrs treated with 780nm, 50mW continuous laser @ 3 J/cm2 to 11 points; Study 2: male aged 39yrs treated with 780nm, 50mW continuous laser @ 2.5 J/cm2 to 13 points). A blinded, single case research methodology was employed, with the addition of placebo in Study 2. Grip strength, pain pressure threshold (PPT) and sympathetic outflow (skin conductance (SC), skin temperature (ST) and blood flux (BF)) were measured at the affected limb before, during and after interventions. Serial dependency was calculated (autocorrelation coefficient and First Difference Transformation) before calculating the celeration line, and trends. In Study 1, the results demonstrated a statistically significant increase (p = 0.01) in pileous ST, and reductions (p = 0.01) in cutaneous BF, glabrous ST and ulnar SC on the affected side thus representing sympathoexcitation (or non-opioid-based analgesia). In Study 2, the results demonstrated increased PPT and grip strength, and decreases in other sympathetic measures post-laser (compared to the placebo period) representing a mixed opioid/non-opioid response. The results support the expectation of a clinical response after one application of laser phototherapy, and in particular a reduction in painful symptoms of lateral epicondylalgia via a sympathetic nervous system response. To clarify dose-response factors, future research with greater subject numbers will investigate laser stimulation thresholds.
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