Page 79 - Journal of Special Operations Medicine - Spring 2014

losses in as little as 8 weeks of training (21% decrease). measurement, late-phase RFD (0–200 ms) remained
Therefore, it may be important for Special Operators’ suppressed. 5,29 Reduced RFD is an important outcome
lower body power output to be assessed before and dur- measure because the ability to quickly generate muscle
ing deployments. The assessment of lower body power force is necessary during swift exfiltration from an SSR
output could be critical because explosive lower body mission. 5
power is highly pertinent to battlefield activities that
require bouts of both high-intensity and short-duration Additionally, Christensen et al. reported a 4% decrease
activity. Additionally, decrements in lower body power in BM and a 5% decrease in total FFM, while the mus-
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output were associated with losses in FFM following cle mass of the lower extremities decreased 6%. The
5
8 weeks of Ranger School (r = 0.30). Commanders loss of lower extremity muscle mass was attributed to
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should also be aware of potential losses in muscle mass knee extensor atrophy. Reduction of MVC will also re-
and power output in Special Operators who are on long duce the ability of Special Operators to jump and sprint,
missions (i.e., at least 8 weeks) in which caloric defi- since these movements depend on RFD. These findings
5
cit, sleep deprivation, and high-energy expenditure are are in accordance with the 8.2% and 9.9% decline in
expected; thus, specific countermeasures and adequate maximal jump height following the 8-day SSR mis-
recovery time after mission completion could be consid- sion. 5,29 A vertical jump test may also then be used to
ered to attenuate Operators’ muscle atrophy and loss of assess the strength of the knee extensors. Christensen
lower body power output. et al. concluded that the effects of long-term covert SSR
missions (i.e., weight loss, muscle atrophy, reduction of
Considering the significant association between lower muscle contraction dynamics) are similar to those of mi-
body power and military tasks, commanders could also crogravity and bed rest. Christensen et al. and Thor-
5
track changes in Special Operators’ lower body power lund et al. recommended the following countermeasures
output to maintain operational proficiency in the field. be considered for future research: (1) resistance training
For example, a simple field test such as the maximal programs for cramped spaces, (2) electrical muscle stim-
vertical jump (countermovement) test could be utilized ulation, and (3) amino acid supplementation to attenu-
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by commanders to assess lower body power output per- ate or prevent muscle atrophy. Fitts et al. studied the
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formance decrements. 5,16,23,30 This test requires minimal effects of 28 days of bed rest on human skeletal muscle
equipment, practice, and time. The test may be valu- fibers. With the aim of counteracting muscle atrophy
16
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able in the field, since it can be administered using chalk- and loss of power, these researchers assigned one group
marked fingers and a blackboard or wall. 16,30 Nindl et of subjects three daily supplements, each containing
al. provide a description of this test. Welsh et al. also 16.5g of essential amino acids and 30g of sucrose. The
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found a maximal vertical jump test to be sufficient in de- supplementation prevented type I fiber force decline in
tecting changes in lower body power output after 8 days the soleus muscle (located in the deep portion of lower
of SUSOPS. However, a loaded jump test may be rel- leg behind the calf muscle) and prevented the decline in
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evant for Soldiers because of the substantial loads carried peak power of the vastus lateralis type II muscle fibers.
during military operations, which may be more represen-
tative of changes in strength and lower body power. 22,23 Additionally, Fitts et al. suggested that a supplement
The vertical jump test to assess lower body power decre- that stimulates muscle protein synthesis be tested as
ments during operational stress may be a important con- a countermeasure for astronauts on the International
sideration for commanders due to its face validity and Space Station. Christensen et al. and Thorlund et al.
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content validity in measuring brief, powerful lower body therefore proposed that the effectiveness of this supple-
exertions similar to many battlefield activities. 30 mentation be tested on Special Operators immobilized
for days on SSR missions. 5,29 Moreover, Thorlund et al.
Special Operators engage in a variety of missions, some noted that researchers should be mindful of the highly
of which may require high-energy expenditure and result restricted space for equipment and supplies during SSR
in overexertion, while others may be opposite in nature, missions and suggested that a reconditioning period be
described by immobilization. For example, Christensen considered between deployments in which Special Op-
et al. and Thorlund et al. reported a significant 10% erators may be conducting highly immobile missions. 29
and 11% decline in knee extensor maximal voluntary
contraction (MVC), respectively, following 8 days of The fitness requirements of Special Operators are ne-
a simulated SSR mission, in which Danish National cessitated by the types of occupational tasks they must
Guard SSR unit Soldiers were required to remain in a perform. Some of these physical tasks may require (1)
face down lying position the entire mission. 5,29 Further- carrying very heavy loads for long periods of time, (2)
more, the rate of force development (RFD) diminished short bursts of high-intensity physical activity, (3) lifting
17%–22% and 18%–26% after the 8-day mission, and heavy loads, and (4) climbing while wearing PPE. For
1
following a 3-hour recovery from the initial post-mission example, during the different phases of training, Ranger

Operational Stressors on Physical Performance and Countermeasures 71