Page 46 - Journal of Special Operations Medicine - Winter 2016

spatial orientation because of the high density of muscle may indicate a clinically meaningful difference in per-
spindles and Golgi tendon organs that are responsible formance. 33,34 The difference in median score for the
for proprioceptive input for postural control. 25-28 These SOM, VEST, and PREF scores is 0. This lack of change
spindles make up what Kavounoudias and Gilhodes indicates that the crewmen experienced no difference in
29
described as the “proprioceptive chain,” allowing input their ability to use somatosensory, vestibular, or inaccu-
to travel from the one location of the body to another rate visual information when wearing TG versus NTG.
to aid postural control and body orientation. The high The difference in the VIS median score was 3, with the
volume of tactical training undertaken by the SWCC crewmen performing better with their TG on. Therefore,
while wearing helmets may increase the rate at which SWCC may use visual input to a greater degree under a
the muscle spindle fires, allowing for faster reaction to challenging balance condition with the addition of TG.
sudden perturbations and improved postural stability.
The amount of time wearing helmets, often more than 4 Limitations
hours per training day, may have also increased muscular This study is not without limitations. Only a small
strength and endurance of the cervical muscles, allowing sample of SWCC was recruited to participate. Also, the
SWCC to maintain postural stability without experienc- crewmen wore tactical footwear during the TG tests,
ing cervical fatigue. This is interesting because previous which may influence the results of the SOT. NeuroCom’s
literature has shown decreased postural stability with Balance Manager Smart Equitest system does allow foot-
exercise-induced fatigue of the cervical extensors. 25,26,30 wear to be worn in cases in which the individual is un-
able to remove their footwear (i.e., elderly populations),
It is also possible the degree of difficulty of the SOT may but states that testing should be done under similar con-
not have been great enough to elicit significant change ditions unless differences between shod and unshod pro-
between wearing TG and not wearing TG. Other studies tocols was the primary measure. Also, the SOT uses an
have shown significant changes in gait when load was equilibrium score to assess postural stability combining
added to military Soldiers compared with normal gait the somatosensory, visual, and vestibular systems into
pattern with changes in knee range of motion, forward one score. The equilibrium score is based upon an equa-
head posture, and pelvis rotation during dynamic move- tion that has a set theoretical limit of stability of 12.5°
ment. 10,31 Dynamic postural stability is another aspect of often seen the normal population. Chaudhry et al.
35
35
balance that allows researchers to assess postural stabil- believe this may also be a limitation because individuals
ity in a valid, reliable, and more functional manner. outside of the normal population may have a higher limit
32
One such test involves jumping off of two feet, landing of stability and, therefore, a theoretical inaccurate result
on one foot, and subsequent postural stabilization upon from the SOT may be observed because of this set limit.
a force plate. This task may be more challenging to
32
SWCC and may reveal greater difference in SOT when Conclusion
the SWCC remain stationary even in challenging sen-
sory conditions. A more challenging dynamic task may SWCC performed very similarly on the SOT with and
be more appropriate because these types of movements without wearing TG. This demonstrates that the sensory
are necessary in some aspects of military training, such systems of the SWCC responded similarly with and with-
as land-based tactical skills and leaping on and off of the out TG to maintain postural stability. There may be a slight
craft. Further, other literature has observed decreased clinically significant difference indicating that SWCC use
dynamic postural stability during a single-leg landing their visual system more while wearing TG even though
jump task in US Army Soldiers while wearing TG. no statistically significant differences were found in the
17
Decrement in dynamic postural stability may increase the SOTcomp score. The researchers believe the primary rea-
risk for lower limb musculoskeletal injury, potentially to soning behind the similar performance is due to frequent
a greater degree than static postural stability tasks. exposure to an unstable occupational platform. This ex-
posure would drive the development, and likely improve-
Although no statistical differences were found, it is im- ment, of postural stability under the conditions tested in
portant to consider the potential clinical significance of the current study. Therefore, the risk of incurring lower
differences observed. Rounding to the nearest whole extremity musculoskeletal injury due to postural instability
number, for ease of clinical interpretation, reveals a dif- may be diminished, but this risk should not be completely
ference score of 3 for the SOTcomp, with the crewmen dismissed, because safety is still imperative to completing
performing worse while wearing TG. It is the opinion any task while carrying a load. Based upon the findings of
of the authors that clinical significance may be observed this study and the nature of the SWCC operational task,
with a change of 3 or more in the SOTcomp score. A further investigation of postural stability during more chal-
change of 3 in the score may be a clinically significant lenging testing conditions, such as greater surface perturba-
difference when investigating differences in SWCC be- tions, dynamic tasks, and heavier loads, may elicit changes
cause, in highly trained crewmen, a small difference in postural stability not observed here.

30 Journal of Special Operations Medicine Volume 16, Edition 4/Winter 2016