Light,
in practice.

How light reflects from human skin and other surfaces.

A laser study in 30 volunteers comparing how 660 and 830 nm light travel through tissue.

In isolated mitochondria, 810 nm increased ATP production at selected power and time settings.

Lab-grown cells responded to 660 nm even without CCO, an enzyme involved in cellular energy production.

Measurements of skin roughness, fine lines and collagen density.

Recovery markers and cycling performance in 48 participants.

Why light intensity and session length need to be considered together.

Zhang et al. describe Fresnel reflection at an optically coupled interface. Kampa et al. measured approximately three times more transmitted power with contact than with a 1 cm gap through about 14.38 mm of skin and muscle in living dogs, using an 830 nm laser. This was a transmission measurement, not a comparison of clinical outcomes.

Joensen et al. found that contact effects varied with laser-probe geometry. Vogt et al., Gurjarpadhye et al. and Lim et al. investigated tissue deformation, water redistribution and pressure-dependent blood and scattering changes. Compression-based optical clearing requires actual tissue deformation.

These studies explain the optical principles behind contact delivery. They do not measure HELIO panel transmission, establish compression from its non-protruding convex lenses, or demonstrate that HELIO produces superior clinical outcomes.

A practical test of the Tenmars TM-206 solar meter.

Understanding study methods, settings and results.

Ryu et al. (2023). How cultured human tendon cells multiplied and moved after 630 nm LED light.

Wong-Riley et al. (2005). Different wavelengths changed CCO activity and ATP levels in cultured nerve cells.

Pruitt et al. (2022). Measurements on human forearms tracked oxidized CCO and oxygen-rich blood after light exposure, including 850 and 1064 nm lasers.

Huang et al. (2013). With 810 nm light, reactive oxygen molecules (ROS) rose in normal cultured mouse nerve cells and fell in stressed cells. Voltage across the inner mitochondrial membrane increased in both.

Chen et al. (2011). In cultured mouse connective-tissue cells, 810 nm triggered ROS and activated NF-κB, a protein that controls gene activity. Antioxidants suppressed this signal.

Sharma et al. (2011). Cultured mouse nerve cells responded differently to different amounts of 810 nm light. ATP, calcium, ROS and mitochondrial voltage were measured; more light did not always give a larger response.

Mason et al. (2014). In CCO purified from bovine hearts, light absorption appeared near 655 nm at the oxidized heme–copper centre (heme a₃/CuB) and peaked near 835 nm at the oxidized copper centre (CuA).

Karu et al. (2005). Cultured HeLa cells showed a red absorption peak near 665 nm. The 650–680 nm region was linked to relatively oxidized CCO; oxygen availability changed the absorption pattern.

Karu et al. (2004). Cell attachment showed peaks near 620, 680, 760 and 820–830 nm in cultured HeLa cells. These peaks describe a cell response. The proposed links to CCO came from comparing spectra.

Hale & Querry (1973). Water absorbs little red light. At 1060 nm, it absorbs less than at the nearby 970 nm band, but more than at 630 or 810–850 nm.

Tseng et al. (2009). Skin measurements in 18 people with skin types I–VI showed how blood, skin pigment, water and scattering together shape the path of light.

Lohr et al. (2009). In lab solutions, 670 nm released the signalling molecule nitric oxide (NO) from blood and muscle proteins — hemoglobin and myoglobin. The work also included animal heart tissue.

Chai, Yoo & Pollack (2009). Light expanded a particle-exclusion zone in water next to a hydrophilic material, with wavelength-dependent responses. This model experiment underpins research into light, interfacial water and charge separation; its strongest response was at 3100 nm.

Bowen & Arany (2023). Seven participants used whole-body 660 + 850 nm light at 24 mW/cm² for 14 minutes — 20.2 J/cm² per session. Sessions took place three times a week for four weeks in this small, unblinded study.

Diez et al. (2004). Measurements of individual ATP-synthase molecules showed how proton flow turns their tiny rotor while they make ATP, the cell’s energy carrier.

Kim et al. (2016). Research using 630 nm LEDs in human dermal fibroblasts and mouse skin examined collagen production and MMP-1. Type-I collagen increased and MMP-1 decreased.

Barolet et al. (2009). A pulsed 660 nm LED protocol increased type-I procollagen and reduced MMP-1 in reconstructed skin. A split-face clinical study recorded improvements in wrinkles and surface roughness.

Houreld et al. (2010). An 830 nm laser increased NO and cell proliferation and reduced TNF-α and IL-1β in a cultured human fibroblast model of diabetic wounds.

Sommer, Haddad & Fecht (2015). At 670 nm, illumination reduced interfacial viscous friction on model hydrophilic surfaces. The authors propose that reduced resistance around ATP synthase offers another mechanism for light-induced ATP production.

GembaRed explains overlapping wavelength bands and mechanisms, including CCO, nitric oxide, water and ion channels, with links to the underlying research.

Tong et al. (2025). In cultured human meniscus-derived stem cells, 1064 nm LED exposure increased calcium, reactive oxygen species and cell proliferation at selected doses. Blocking TRPV1 reduced these responses. CCO activity and nitric-oxide concentration remained unchanged.