Page 43 - Journal of Special Operations Medicine - Winter 2016

Postural Stability of Special Warfare
Combatant-Craft Crewmen With Tactical Gear

Paul M. Morgan, MS; Valerie J. Williams, DPT; Timothy C. Sell, PhD

ABSTRACT

Background: The US Naval Special Warfare’s Special to loads that may exceed the Soldier’s body weight.
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War fare Combatant-Craft Crewmen (SWCC) operate on The amount of gear worn for protection and tactical
small, high-speed boats while wearing tactical gear (TG). operation has significantly contributed to improving
The TG increases mission safety and success but may af- military operations. The added weight, however, ap-
fect postural stability, potentially increasing risk for mus- pears to increase pain and the risk for musculoskeletal
culoskeletal injury. Therefore, the purpose of this study injury, which is a significant problem in the US military:
was to examine the effects of TG on postural stability more than 700,000 such injuries were reported as of
during the Sensory Organization Test (SOT). Methods: 2006. The cause of musculoskeletal injuries may be
1-4
Eight SWCC performed the SOT on NeuroCom’s Bal- due to multiple factors, including overuse, performing
ance Manager with TG and with no tactical gear (NTG). military duties in body armor, or even leisure activities
The status of gear was performed in randomized order. and exercise. 3,5-7
The SOT consisted of six different conditions that chal-
lenge sensory systems responsible for postural stability. One risk factor for injury is decreased postural stability
Each condition was performed for three trials, resulting or, simply stated, one’s balance. Postural stability can
8,9
in a total of 18 trials. Results: Overall performance, each be affected by the increased amount of weight worn by
individual condition, and sensory system analysis (soma- military Servicemembers by moving the center of mass
tosensory, visual, vestibular, preference) were scored. superiorly and anteriorly, altering sensory input, hinder-
Data were not normally distributed therefore Wilcoxon ing response time, increasing task difficulty by influenc-
signed-rank tests were used to compare each variable (p ing mobility, and increasing the risk for musculoskeletal
= .05). No significant differences were found between injury. 1,3,4,10-15 Schiffman et al. observed decreased pos-
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NTG and TG tests. No statistically significant differences tural stability in military personal performing static
were detected under the two TG conditions. This may be tasks with weights of 6kg, 16kg, and 40kg. The addi-
due to low statistical power, or potentially insensitivity tion of load carriage has been shown to increase pos-
of the assessment. Also, the amount and distribution of tural sway during static upright stance, suggesting that
weight worn during the TG conditions, and the SWCC’s the external load negatively affects the ability of the
unstable occupational platform, may have contributed individual to maintain postural stability while decreas-
to the findings. The data from this sample will be used ing mobility for occupational tasks. 11,12,16 Further, Sell et
in future research to better understand how TG affects al. performed a standardized jumping task to simulate
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SWCC. Conclusion: The data show that the addition of military activities and observed that TG negatively af-
TG used in our study did not affect postural stability of fects dynamic postural stability. It was concluded that
SWCC during the SOT. Although no statistically signifi- the observed decrement in dynamic postural stability
cant differences were observed, there are clinical reasons when wearing TG may lead to increased risk for muscu-
for continued study of the effect of increased load on pos- loskeletal injury. 17
tural stability, using more challenging conditions, greater
surface perturbations, dynamic tasks, and heavier loads. Although there have been numerous studies of pos-
tural stability and military load carriage, the effect of
Keywords: postural stability; tactical gear; sensory organi- body armor on postural stability of Special Operations
zation test; Navy; SWCC Forces (SOF) Special Warfare Combatant-Craft Crew-
men (SWCC) is unknown. The postural stability of this
specific group is particularly important because of the
specialized environment and conditions in which they
Introduction
work. SWCC perform special missions on small, high-
Tactical gear (TG) worn by US military members has sig- speed water craft on ocean and small-river water sys-
nificantly increased in weight since the late 19th century tems for the insertion and extraction of SOF in areas

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