Lasers in Medical Science

, Volume 10, Issue 4, pp 253–259

The relevance of pulse repetition rate and radiant exposure to the neurophysiological effects of low-intensity laser (820 nm/pulsed wave) irradiation upon skin temperature and antidromic conduction latencies in the human median nerve

  • Andrea S. Lowe
  • G. David Baxter
  • Deirdre M. Walsh
  • James M. Allen
Original Articles


The effects of low-intensity near-infra-red laser irradiation (820 nm; 1.5 and 9.0 J cm−2; pulsed at 12 Hz, 73 Hz and 5 kHz) upon peripheral neurophysiology and skin temperature were investigated using antidromic conduction studies in the human median nerve in vivo. Healthy human volunteers (n = 90) were recruited and allocated randomly to either a control group (n=10) or one of eight experimental groups (two radiant exposures, 1.5 J cm−2 and 9.0 J cm−2 at one of three pulse repetition rates, 12 Hz, 73 Hz or 5 kHz, in addition to a placebo group for each radiant exposure;n = 10 all groups). Analysis of variance (ANOVA) demonstrated a significant (p≤0.05) decrease in skin temperature following irradiation at the lowest radiant exposure (1.5 J cm−2) combined with pulse repetition rates of 73 Hz and 5 kHz, with the greatest effect at 73 Hz. These changes in skin temperature were coupled with increases in negative peak latency (NPL); ie changes in NPL were inversely related to changes in skin temperature. However, in contrast to the authors' previous findings using continuous wave (CW) laser irradiation, differences in NPL were not found to be significant. These findings, therefore, provide little evidence of the neuro-physiological effects of low-intensity infra-red irradiation at the dosage levels and pulse repetition rates used here.

Key words

Nerve conduction Laser therapy Skin temperature Biostimulation 


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  1. 1.
    Baxter GD, Bell AJ, Allen JM, Ravey J. Low level laser therapy: current clinical practice in Northern Ireland.Physiother 1991,77:171–8Google Scholar
  2. 2.
    Devor M. What's in a laser beam for pain therapy?Pain 1990,43:2, 139Google Scholar
  3. 3.
    Basford JR. Low-energy laser therapy: controversies and new research findings.Lasers Surg Med 1989,9:1–5PubMedGoogle Scholar
  4. 4.
    Baxter GD.Low Level Laser Therapy: Current Clinical Practice, Analgesic and Neurophysiological Effects. DPhil Thesis: University of Ulster, 1991Google Scholar
  5. 5.
    Walker J. Low-level laser therapy for pain management: a review of the literature and underlying mechanisms. In: Ohshiro T, Calderhead RG (eds)Low Level Laser Therapy: A Practical Introduction. Chichester: Wiley, 1988Google Scholar
  6. 6.
    Moore KC. An update on the application of low reactive level laser therapy (LLLT) in the United Kingdom.Laser Ther 1989,1:157–62Google Scholar
  7. 7.
    Greathouse DG, Currier DP, Gilmore RL. Effects of clinical infrared laser on superficial radial nerve conduction.Phys Ther 1985,65:1184–7PubMedGoogle Scholar
  8. 8.
    Snyder-Mackler L, Bork CE. Effect of Helium-Neon laser irradiation on peripheral sensory nerve latency.Phys Ther 1988,68:223–5PubMedGoogle Scholar
  9. 9.
    Basford JR, Daube JR, Hallman HO, Millard TL, Moyer SK. Does low-intensity Helium-Neon laser irradiation alter sensory nerve action potentials or distal latencies?Lasers Surg Med 1990,10:35–9PubMedGoogle Scholar
  10. 10.
    Baxter GD, Bell AJ, Allen JM, Ravey J. Laser mediated increase in median nerve conduction latencies.Irish J Med Sci 1991,160:145–6Google Scholar
  11. 11.
    Baxter GD, Allen JM, Bell AJ. The effect of low energy density laser irradiation upon human median nerve conduction latencies.J Physiol 1991,435:63PGoogle Scholar
  12. 12.
    Baxter GD, Allen JM, Walsh DM, Bell AJ, Ravey J. Localisation of the effect of low energy laser irradiation upon conduction latencies in the human median nervein vivo.J Physiol 1992,446:445PGoogle Scholar
  13. 13.
    Baxter GD.Therapeutic Lasers: Theory and Practice. Edinburgh: Churchill Livingstone, 1994Google Scholar
  14. 14.
    Kramer J, Sanotin M. Effect of low-power laser and white light on sensory conduction rate of the superficial radial nerve.Physiother Canada 1993,45:165–70Google Scholar
  15. 15.
    Baxter GD, Walsh DM, Allen JM, Lowe AS, Bell AJ. Effects of low intensity infrared laser irradiation upon conduction in the human median nervein vivo.Exp Physiol 1994,79:227–34PubMedGoogle Scholar
  16. 16.
    Lowe AS, Baxter GD, Walsh DM, Allen JM. The effect of low intensity laser irradiation (830 nm) upon skin temperature and antidromic conduction latencies in the human median nerve: relevance of radiant exposure.Lasers Surg Med 1994,14:40–6PubMedGoogle Scholar
  17. 17.
    Walsh DM.Investigations of the Neurophysiological and Hypoalgesic Effects of Low Intensity Laser Therapy and Trancutaneous Electrical Nerve Stimulation. DPhil Thesis: University of Ulster, 1993Google Scholar
  18. 18.
    Mokhtar B.Combined Phototherapy/Low Level Laser Therapy: Analgesic and Neurophysiological Effects. DPhil Thesis: University of Ulster, 1993Google Scholar
  19. 19.
    Walsh DM, Lowe AS, Baxter GD, Allen JM, Bell AJ. An investigation of the effect of 820 nm laser irradiation upon nerve conduction in the frog sciatic nerve in vitro.Laser Ther 1995,7:5–10Google Scholar
  20. 20.
    DeJesus PV, Hausmanowa-Petrusewicz I, Barchi RL. The effect of cold on nerve conduction of human slow and fast fibers.Neural 1973,23:1182–7Google Scholar
  21. 21.
    Ludin HP, Beyeler F. Temperature dependence of normal sensory nerve action potentials.J Neurol 1977,216:173–9CrossRefPubMedGoogle Scholar
  22. 22.
    Lowe AS, Walsh DM, Baxter GD, Allen JM. Effects of low intensity laser (830 nm) upon forearm skin blood flow in humans.J Physiol 1994,480:137PubMedGoogle Scholar
  23. 23.
    Dyson M, Young S. Effect of laser therapy on wound contraction and cellularity in mice.Lasers Med Sci 1986,1:125–30CrossRefGoogle Scholar
  24. 24.
    King PR. Low level laser therapy: a review.Physiother Theory Pract 1990,6:127–38Google Scholar

Copyright information

© W.B. Saunders Company Ltd 1995

Authors and Affiliations

  • Andrea S. Lowe
    • 1
  • G. David Baxter
    • 1
  • Deirdre M. Walsh
    • 1
  • James M. Allen
    • 2
  1. 1.Biotherapeutics Research Group, School of Health SciencesUniversity of UlsterJordanstownUK
  2. 2.Biotherapeutics Research Group, School of Biomedical SciencesUniversity of UlsterJordanstownUK

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