March/April 2020 - 23

Laser and Light Therapy
referred to as the Arndt-Schultz principle 8,9
. This principle
suggests that lower doses of light are possibly more
effective than much higher doses.
As alluded to earlier, most of these LLLT devices generate
light in the red visible, or near-infrared bands of the electromagnetic
spectrum, with wavelengths in the range of
600-1000nm. These devices are identified as class 3A or
3B lasers, and are not thought to stimulate any appreciable
thermal effects. These devices are often designed as a
single emitter, or in a " cluster " , which is a less common
configuration. The output may be either continuous or
pulsed. The longer wavelengths (>1300nm) appear to be
rapidly absorbed by water, thereby having less penetration,
hence why most units sold work within the lower
wavelengths previously noted.
The parameters of how to use these devices are
dependent upon the output power (watts or mW),
irradiation area (cm2) and time (seconds). The energy
delivered is measured in Joules (J). The energy density is
calculated by the total amount of energy divided by the
irradiation area (J/cm2). Units that have a higher power
output, and larger irradiation area, often require shorter
treatment times. This is one of the arguments put forth
for the use of high powered lasers, which allow clinicians
to treat tissues utilizing much shorter treatment times.
However, with increasing power, comes the risk of potential
tissue damage if overtreatment occurs. The use of LLLT
devices are not thought to present this same risk, hence
why they are more commonly found in most clinical settings.
Treatment times often fit into the range of 30 to 60
seconds per treatment point for most devices, and the total
treatment time depends upon the number of points being
treated in a session. Larger tissue areas, such as the lower
back, often require more treatment points than a smaller
structure like a toe. This is why new devices like LED pads
are becoming increasingly popular, as they allow for larger
areas to be treated, often unattended, allowing for greater
clinical efficiency. Another advantage to LED devices is a
decreased risk to ocular structures in the eye, which has
long been one of the chief concerns with using laser devices
in a clinical setting without wearing appropriate eyewear for
everyone in the room where the treatment is occurring.
It has long been acknowledged in the literature that
therapeutic lasers can have a beneficial effect in the
treatment of dermatologic conditions, as well as to
stimulate intra-oral healing. The use of therapeutic
light therapies for musculoskeletal conditions is less
clear, although over the last few decades research has
begun to demonstrate a clearer appreciation for its role
in the treatment of tissue pain, and stimulate a more
rapid healing response in muscle and joint conditions,
amongst other clinical uses. Recently, a systematic review
and meta-analysis of the effects of LLLT on pain and
disability in knee osteoarthritis, published in the British
Medical Journal, found that it significantly reduced pain,
as compared to placebo, as well as a notable reduction in
disability 10
. Takenori 11
and colleagues, in a randomized,
double-blind placebo clinical trial, found that LLLT
performed on a cohort of collegiate athletes led to an
almost immediate 30% reduction in pain in almost 75%
of the participants. A paper by Vinck 12
suggests that one
potential role that laser therapy may play in reducing pain
may be through its ability to modulate nerve conduction
and reducing action potentials. Other studies have come to
similar conclusions.
In a pilot study by Foley and colleagues 13
, which
examined the role of LED phototherapy in facilitating return
to play in injured university athletes, a total of 395 injuries,
including sprains, strains, tendinopathies and contusions
were treated over 1,669 sessions. It was found that the
use of an 830nm LED device led to a quicker recovery and
return to play. Although a control group was not utilized in
the study, it nonetheless suggests therapeutic light may
play an important role in facilitating the healing process 13
However, one of the most exciting developments in
.
the literature examines the role laser therapy may play
in the role of enhancing tissue recovery and improving
performance. A randomized controlled trial by Tomazoni
and colleagues 14
examined the role of LLLT, applied
prior to an intense running session in high level soccer
players, on markers of muscle damage, inflammation, and
oxidative stress in the tissues. It was found that utilizing
laser therapy prior to running reduced muscle damage, led
to reductions in the levels of creatine kinase and lactate
dehydrogenase post-exercise, as well as interleukin-6, in
addition to other biomarkers. Furthermore, the athletes
treated with the laser also showed improvements in VO2
max, as well as both aerobic and anaerobic thresholds
during the exercise session.
In a similar study published in the Journal of Strength
and Conditioning Research 15
, a randomized, double-blind,
placebo controlled study also found that pre-exercise
photobiomodulation therapy not only improved average
time of sprints performed and fatigue index in an anaerobic
testing protocol, but also decreased the percentage of
change in blood lactate levels post exercise.
It is becoming increasingly clear that photobiomodulation
therapies, including low-level laser therapy, high-powered
laser, and LED cluster devices, are showing efficacy in
both the treatment of injuries, and as a method to enhance
athletic performance and recovery. It would be wise for
clinicians and performance coaches alike to further explore
how to incorporate these devices into their therapeutic
regimens, as a way to improve their clinical outcomes and
performance enhancement programs. n
References
1. Mester E, Ludany G, Sellyei M, et al. Studies on
the inhibiting and activating effects of laser beams.
Langenbecks Arch Chir. 1968; 322:1022-1027.
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March/April 2020

Table of Contents for the Digital Edition of March/April 2020
