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|Title: ||The biomechanics of military load carriage and injury potential|
|Authors: ||Birrell, Stewart A.|
|Keywords: ||Load carriage|
|Issue Date: ||2007|
|Publisher: ||© Stewart Birrell|
|Abstract: ||This thesis consisted of two main research themes: 1) The biomechanics of
military load carriage, and 2) injuries and discomfort caused by load carriage.
Although different in their methodological approaches, the two sections are linked
and integral to each other. Harman et al (2000) suggest that the biomechanical
analysis of military load carriage, and in particular the study of ground reaction forces
(GRF), is relevant to the understanding and prevention oflower extremity injuries.
The general aims of the biomechanical analysis of load carriage were to
determine the effect that heavy load carriage, rifle carriage and load distribution has
on GRF parameters. In addition to determining the mechanisms behind these potential
changes, base-line data for British military load carriage systems (LCS) were also
established. An important factor for the thesis was to consider the LCS as a single unit
(where possible) and not its individual components, for example the backpack alone.
The final biomechanical study involved a 3D, bi-Iateral gait analysis of load carriage;
with this type of analysis being rare in the published literature.
Results from the biomechanical studies showed that GRF parameters increased
proportionally to applied load, even when heavy loads of up to 40 kg were carried.
Also seen was an increase in mediolateral impulse and stance time with greater
carried load. Another area which has received little or no attention in the literature is
the effect of rifle carriage on gait. This thesis showed that rifle carriage changed basal
gait patterns as observed in the GRF parameters. The most noteworthy results were an
increase in impact peak and mediolateral impulse. The mechanism behind these
changes is most likely to be a restriction of natural arm swing induced by rifle
carriage. Distributing load more evenly around the body had limited effect on the
GRF parameters measured. However, some important changes were observed. These
were an increase in force minimum and a decrease in maximum braking force at the
heaviest load. The latter effect has been strongly linked to an increase in the incidence
of foot blisters within the literature. Finally, the gait analysis study showed significant increases in joint moments and torques with carried load. Also observed was a
decrease in stride length and increase in percentage double support and stance. The
main kinematic differences were a decrease in range of motion at the knee and pelvis
rotation, and an increase in pelvis tilt as load is added.
Four further studies were conducted in an effort to determine the discomfort
and injury caused by load carriage. The first 3 studies collected sUbjective discomfort
data via interviews, questionnaires and the use of comfort ratings. All of which were
collected either during or after a prolonged period of load carriage by military
personnel. Results gleaned from these studies showed that the upper limb is
susceptible to short term discomfort following load carriage, whereas the lower limb
is not. The lower limb may be at an increased risk of developing medium to long term
injuries such as joint degradation and stress fractures. However, foot pain was rated as
the most uncomfortable skeletal region of the body following a 1 hour field march
with load, and blisters were experienced by around 60% of participants. Shoulder
discomfort commences almost as soon as load is added and increases steadily with
time. However, foot discomfort seems to increase more rapidly once the discomfort
first materialises. This early development of shoulder or foot pain may be a risk factor
for severe pain or non-completion of a period of prolonged load carriage. Finally,
females experienced more discomfort in the hip joint and feet compared to males. (Continues...).|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Design School)|
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