Achilles Tendinopathy: Low Level Laser Therapy Dosage Calculation

Current recommendations specify that LLLT dosage be provided in Joules (J, total energy), rather than the previous
recommended Joules/cm2 (J/cm2, energy density). Use Joules rather than Joules/cm2 to specify how much energy is
delivered in a treatment.

In Laser devices that do not calculate Joules automatically, dose can be determined in seconds of exposure required to give
the desired Joules by using the following calculation:

• Joules = watts.seconds
• hence, Seconds = Joules/watts

For example:

• For a 50 mW Laser (= 0.050 Watts), with a required dose = 2 J per point…
• Seconds exposure = 2 / 0.05 = 40 secs

This change is very important clinically as the use of the previously recommended Joules/cm2 resulted in confusion when
comparing dosages between protocols. The resultant dose in Joules/cm2 could be the consequence of a number of
different treatment options.

 For example, 4 J/cm2 can be delivered by: Option #1 a 20 mW Laser with a beam cross section of 0.5 cm2 in 100 seconds i.e., 4 = (0.02/0.5 x 100) Option #2 a 10 mW laser with a beam cross‐section of 0.25 cm2 in 100 seconds i.e., 4 = (0.01/0.25 x 100) In Option #1, the total energy delivered would be 2 J In Option #2 the total energy would be 1 J

This example illustrates that using Joules/cm2 resulted in one patient receiving twice the total amount of energy that is