Page 108 - Journal of Special Operations Medicine - Spring 2017

performance decrements can be introduced. However, it bacterial species in various parts of the body is some-
is worth emphasizing that P2 must be more than “HPO what overwhelming and the data revealed by research
by anecdote” and cannot be based solely on a person’s are not always consistent. 10,49–52 However, differences
subjective judgment about something like how much in an individual’s microbiome may prove to have far-
sleep they think they need. Despite individual differ- reaching consequences for the development of disease,
ences, the importance of sleep as a biological imperative from cognitive to sensory to physical effects, and hence
cannot be denied, and many studies have shown that provide countermeasures to mitigate performance
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people are notoriously poor judges of how much sleep decrements. 24,49,52 Likewise, unfavorable microorgan-
they both require and actually get. A true P2 approach, isms could potentially threaten a mission’s success. We
therefore, would use objective data to determine how know far too little to make any recommendations re-
much sleep is likely optimal for any individual. garding the microbiome, but accumulating evidence
suggests that it will become increasingly important as
Response to physical training we move forward in both PMI and P2.
and psychological stress
Individual differences in response to physical and psy- Individual Psychological Differences
chological training and stress are well documented. Ex-
amples include differential responses to exercise, such as As debate continues about what may affect real-world
peri- and postexercise levels of creatine kinase, 36–38 stress performance outcomes, the contribution of individual
hormones, 9,33,39–42 and immune markers ; psychological traits and predispositions (i.e., who you came into the
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stress (stress hormones) 41–43 ; and genetic predispositions world as) with certain inclinations, tendencies and pro-
for some individuals to lose, rather than gain, bone den- clivities, remains a longstanding interest. Increasing evi-
sity during exercise in basic training. Other data show dence indicates P2 approaches may have to factor such
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a wide range of responses to the same exercise interven- individual differences into approaches for training and
tion; for example, some individuals are very responsive performance. For example, it is well documented that
to strength and/or aerobic training and others exhibit maintaining attention when carrying out everyday tasks
little to no response, 46–48 similar to what we described is always challenging but it is potentially life threatening
for creatine and β-alanine supplementation. Table 1 in many mission situations. This would be particularly
lists various biomarkers that differ across individuals relevant when a SOF operator fails to monitor their en-
in response to exercise, psychological stress, and other vironment and respond to certain events in the requisite
stressors. Given HPO’s general emphasis on enhancing time. Importantly, some persons are inherently in tune
recovery from stress, such differences, as they continue with attentional control, whereas many have a propen-
to be documented, are likely to be even more important sity to engage in mind wandering, both of which could
for tailoring approaches for individuals. determine performance on tasks requiring vigilance
and, therefore, could shape different HPO interven-
Microbiome tions. 53–56 Other traits being investigated as important
One of the fastest growing areas with regard to indi- in human performance include cognitive ability, general
vidual differences and health is the microbiome. The US self- efficacy (i.e., belief in one’s ability to successfully
National Institutes of Health initiated the Human Mi- accomplish a task), and goal orientation. This is con-
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crobiome Project (http://hmpdacc.org) to identify and sistent with the concept of hardiness, which is essential
characterize the microorganisms associated with both for SOF operators. The three attitudes or traits of hardi-
healthy people and those with disease. The diversity of ness—commitment, challenge, and control—have been

Table 1 Selected Biological Markers Known to Differ Among Individuals in Response to Identical Exercise Training,
Psychological Challenges, and/or Specific Stressors
Stress Responsive Cardiovascular Immune/Inflammatory
Hormone Markers Exercise Markers Indexes Markers Other Markers
Cortisol Lactate Heart rate Interleukin 6 Insulin-like
growth factor-I
Arginine vasopressin Creatine kinase Blood pressure C-reactive protein Vitamin D
Epinephrine/norepinephrine Aerobic capacity or Endothelial
strength function
Adrenocorticotropic hormone
Dehydroepiandrosterone
Neuropeptide Y

84 Journal of Special Operations Medicine Volume 17, Edition 1/Spring 2017