EMBARGOED
FOR RELEASE UNTIL 12:01 AM EDT
MONDAY, APRIL 7, 2008
Contact: Donna Krupa
Newsroom: (619) 525-6202
Office: (301) 634-7209
Cell: (703) 967-2751
dkrupa@the-aps.org
Backpack Straps Can
Decrease Blood Flow In The Shoulder And Arm
Adult
backpacks weighing 26 pounds or more may also lead to a loss in fine motor
control and an increase in fatigue
SAN DIEGO, CA – More than 92 percent of the
children in the U.S. carry backpacks. Typically the backpacks are loaded
with almost one-fourth of the child’s body weight (22 percent) and worn with
only one strap. Last year, a team of physician researchers examined the
effect heavy-loaded backpack straps can have on children. They found the
straps can significantly increase pressure when the load is ten percent or
more. They also found that strap pressures with loads as small as ten
percent of bodyweight can obstruct localized blood flow and contribute to
shoulder fatigue.
This year the team has examined pack straps and adults.
In some professions, such as the military, firefighting and mountain rescue,
the packs may equal as much as 60 percent of adult body weight. The findings
of the most recent study indicate that even light loads of 26 pounds can
decrease upper extremity blood flow, and may result in a loss of fine motor
control and increased fatigue.
Study Being Presented at the 121st Annual
Meeting of the American Physiological Society
The studies were conducted by Timothy Neuschwander,
Brandon Macias and Alan Hargens, all of the Department of Orthopaedic
Surgery, University of California–San Diego. Dr. Neuschwander will present
the team’s findings, Backpack Straps Decrease Upper Extremity
Blood Flow, at the 121st Annual Meeting of the American
Physiological Society (APS;
www.the-APS.org/press), part of the Experimental Biology 2008 scientific
conference.
Background and Study Summary
Backpack straps typically rest on an area of the body
where they may compress the axillary vein which causes abnormally high blood
pressure inside the veins and a subsequent decrease of blood flow in the
shoulders and arms. The researchers speculated that blood flow of the large
and small vessels of the upper extremity area would decrease in an
individual while wearing a backpack.
To test their theory, they examined eight healthy
volunteers, six men and two women between the ages of 18-30. The right
brachial artery was measured using ultrasound and the index finger pulp
microvascular flow was measured using the photoplethysmography method.
Baseline flows were measured immediately before and ten minutes after
donning a 26 pound backpack. A ten minute testing period was chosen because
people typically wear a backpack for at least ten minutes. This amount of
time is also sufficient to measure flood flow.
After wearing the pack for ten minutes, brachial artery
blood flow decreased from 2.66± 0.36 to 1.52± 0.27 mL/s (p<0.05, paired
T-test), and index finger microvascular flow decreased from 100 percent to
46±6 percent (p<0.05, paired test).
Conclusions
The researchers concluded that backpack loads of just
26 pounds decrease upper extremity macrovascular and microvascular blood
flows, and may result in a loss of fine motor control and increased fatigue.
According to Timothy Neuschwander, MD, the first author of the study and a
physician, “We surmise that the mechanism of diminished blood flow is likely
due to strap compression of the axillary vein. We think that backpack straps
may benefit from a redesign that skirts the vein leading from the upper
extremity to the heart.”
*****
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (APS;
www.The-APS.org/press) has been an integral part of this discovery
process since it was established in 1887.
# # #
NOTE TO EDITORS: The APS annual meeting is part
of the Experimental Biology 2008 (EB ’08) gathering and will be held April
5-9, 2008 at the San Diego, CA Convention Center. To schedule an interview
with Dr. Neuschwander please contact Donna Krupa at 301.634.7209
(office), 703.967.2751 (cell) or
DKrupa@the-APS.org.
|
