of Physical Therapy at Nova Southeastern
University Discusses Beneficial Effect of Low Level
Samuel Cheng, an Assistant Professor of
the Physical Therapy Program at Nova Southeastern University, spoke recently
for The Athletic Trainers’ Association of Florida, on the parameters,
impact and use of low level light lasers to treat pain and injury. Low
level laser light treatments are a new, painless, sterile, non-invasive
treatment used to treat a variety of pain conditions, injuries, wounds,
fracture, and neurological conditions.
Cheng, who used low level light lasers in Taiwan, said the Law of Grotthus-Draper
confirms that the body must absorb the energy from the laser before it
can have an “effect.” He said the light’s depth of
penetration depended on the laser’s wavelength which is measured
in nanometers and the power of light which is delivered to the skin.
Using a power-point presentation, Cheng
explained that low level light or “cold” lasers can trigger many cellular changes including
the production of enzymes and protein substances vital for innumerable
bio-chemical actions. He added, “The laser light also stimulates
the cell’s mitochondria, the biochemical engine that produces enzymes
essential for cell function.
Cheng described the pain reduction benefits
of low level light lasers as “using light to reduce the excitability of nervous tissue, reactivate
enzymes, and increase ATP (Adenosine Triphosphate) release and energize
inactivated enzymes.” He described the laser as “sending energy
to jumpstart a system.”
He noted that the laser’s parameters include wavelength – measured
in nanometers, power--measured in milliwatts, energy density – measured
in joules, and frequency. Cheng said some machines deliver a steady stream
light while others deliver pulsed light. He added that studies indicate
skin absorbs light best in a range of 600-1000 nanometers.
Cheng, who brought two lasers with him
to the lecture, said the two most common low power lasers were Helium
Neon – a
visible gas in the 400-700 nm light range and Gallium Arsenide, which
usually had a wavelength
between 600-1200 nm.
The U.S. Food and Drug Administration cleared the first low level light
laser (ML830) in 2002 for pain relief for Carpel Tunnel Syndrome, a pinched
nerve problem in the wrist that affects about 8 million Americans annually.
Cheng explained that lasers were classified into four groups: Class 1
includes lasers used for CD players, Class II describes a laser which
could be used as a laser pointer, Class IIIa and Class IIIb are therapeutic
lasers and Class IV encompasses surgical lasers.
Cheng cautioned members of his audience
to know which class of lasers they used. “If you use a Class IV laser, you can burn the skin,” he
In offering clinical evidence for using
lasers, Cheng said one should place the head of the laser directly on
the skin at
the pain point or “right
where it hurts.”
He also said the clinician should hold the laser over each pain point
for approximately 10-30 seconds. Regarding contraindications, Cheng said
clinicians should avoid using the laser over the eye and over the fetus
of a pregnant woman.
He concluded his talk by demonstrating two lasers, the ML830 and the
Erchonia 635. Both are Class IIIA lasers, yet ML830 offers direct light
and Erchonia offers pulsed light.
Cheng’s final remarks to the athletic
trainers stressed the positive: low level light lasers are very helpful
pain and inflammation.
M. Samuel Cheng, PT, MS, Sc.D, Assistant Professor of the Physical Therapy
Program at Nova Southeastern University, can be reached at firstname.lastname@example.org
or (954) 262-1273.