What are Total Joules and how do I calculate Dosage with Full Body Red Light Therapy?
In the quest to find the most scientific and accurate way to deliver dose, we have covered a lot of important topics:
- Finding a reasonable intensity that isn’t too high.
- Calculating dose in J/cm^2 based on intensity and time.
- Proper measurements and how most companies are lying about intensity.
- Using the contact method to reduce reflection losses.
- What do real full-body dosage protocols actually look like.
One thing we haven’t covered yet is how Total Joules comes into play. As we mentioned before, most studies use small lasers with a fairly small coverage area. How can we compare the energy delivered from a laser study to a large full-body panel? Some experts are now suggesting that Total Joules is the best way to consider dosage protocols, not J/cm^2.
For example, let’s say we have a laser spot area of 0.2cm^2, which is fairly common [1]. Yes, the spot size of many lasers is dramatically less than even 1 cm^2! Let’s compare that to our GembaRed Rex panel which is about 12 in x 12 in area with densely packed LEDs, which is about 948 cm^2. So already our 12x12in panel, which some people say is small, is already 4,740 times larger than a laser spot.
Laser Spot Area: 0.2 cm^2
GembaRed Rex Coverage Area: 948 cm^2
- 4,740 times larger than the laser!
GembaRed Reboot Body-Light Coverage Area: 1555 cm^2
- 7,775 times larger than the laser!
So already we see a massive difference in the area covered by a panel versus a laser.
How Intensity Plays a Role:
Now let’s take a look at how our intensity plays a role. We know that many successful laser studies use 100mW/cm^2 (This is why many panel companies try so desperately to lie and say they emit >100mW/cm^2 at 6 inches.). So, we will use that number for the laser. According to some laser guidelines a good fluence (J/cm^2) is 3 to 10 J/cm^2. [2]
Based on the intensity and our desired fluence we can calculate the time. This is made simple with our calculator.
Device |
Fluence (J/cm^2) |
Intensity (mW/cm^2) |
Time (min) |
Laser |
10 |
100 |
1.7 |
GembaRed Rex |
10 |
7 (at 0 inches) |
23.8 |
GembaRed Reboot |
10 |
37 (at 12 inches) |
4.5 |
According to the Law of Reciprocity of dosing, some people would say that all 3 of these doses of 10 J/cm^2 will have an equivalent photobiomodulation effect. However, knowing the massive difference in sizes between each device, this assumption is absurd. Most studies will agree that the Law of Reciprocity only applies within a reasonable range of comparison. [2] It cannot be used to compare drastically different sized devices and power levels.
The Law of Reciprocity says that only the dosage or fluence matters. A high powered light used for a short amount of time would be equivalent effect to a low powered light used for a longer amount of time. This is only true for a reasonable intensity range in equivalent sized devices.
Calculating True Dose: Fluence (J/cm^2) or Total Joules?
Many studies are perfectly satisfied by quantifying the fluence (J/cm^2) as the dosage target. This works well if we assume all the LLLT studies are using similar sized lasers. Now that LEDs are becoming popular clinically and commercially, we see larger devices being used. Now is the time to consider Total Joules.
The conversion of J/cm^2 to Total Joules is very easy. We just multiply the fluence by the treatment area of the device. Since we are only multiplying by 10 J/cm^2 in this case, then the math is pretty simple.
Device |
Total Joules |
Coverage Area (cm^2) |
Fluence (J/cm^2) |
Intensity (mW/cm^2) |
Time (min) |
Laser |
2 |
0.2 |
10 |
100 |
1.7 |
GembaRed Rex |
9480 |
948 |
10 |
7 (at 0 inches) |
23.8 |
GembaRed Reboot |
15550 |
1555 |
10 |
37 (at 12 inches) |
4.5 |
So here we see the Total Joules of a 100mW/cm^2 laser at 10 J/cm^2 fluence is only 2 Joules! That seems rather low, although it is likely still effective for some targeted treatments. Often, we see laser studies applying treatment to multiple points to increase the Total Joules of the session.
By comparison, large LED panels can offer thousands of Joules or even tens of thousands of Joules in a single session! This is a very cost-effective way to deliver a lot of light energy. However, much of this energy is lost by skin reflection if panels are used more than 6 inches away.
What is the target number for Total Joules?
If Total Joules is the best way to quantify dosage with large panels, then how do we know how much is required? Dr. Michael Hamblin has been quoted in some interviews that Total Joules should be the best way to consider dosage. In the interviews, he usually states that several thousand Joules should be enough for a photobiomodulation response. [3]
We can see in this analysis that GembaRed panels can easily reach the desired dosage even if we target lower times and fluences. Remember that too much power can quickly lead to a biphasic dose response, so we want to make sure we reach the minimum effective dose for efficiency and effectiveness.
Now our dosage calculation is even longer! Before, we only wanted to find the Time (s) needed to reach a certain fluence (J/cm^2) based on intensity (mW/cm^2).
Fluence (J/cm^2) = [Intensity (mW/cm^2) ÷ 1000 (mW/W)] × Time (sec)
For the Total Joules calculation we now have to multiply by the treatment area that the intensity covers:
Total Joules = [Intensity (mW/cm^2) ÷ 1000 (mW/W)] × Time (sec) × Treatment Area (cm^2)
Or, if you have already calculated the Fluence, then you only need to multiply by the treatment area.
Total Joules = Fluence (J/cm^2) × Treatment Area (cm^2)
And that is it! For larger devices we need to consider all of these factors of intensity, time, fluence, and total joules to fully understand the true dosage and energy delivered by Red Light Therapy!
*Disclaimer: All information in this article and website are intended for educational purposes only. It is not intended to treat, diagnose, or cure any ailment. Please consult with your doctor or trusted wellness practitioner before starting any new health activity including Red Light Therapy.*
[1]
- PMCID:
- PMC3635110
[2]