Page 146 - JSOM Summer 2022

fat, as well as a host of other related health disorders (e.g., use of wearable technology and by adopting an interdisci-
endocrine dysfunction, chronic pain, poor sleep). 9,19 plinary model of care that can adequately address these inter-
related health and performance deficiencies. 5,9
Allostatic Load
Allostatic load/overload accumulates as one is repeatedly ex- Allostatic Imbalance
posed to chronic stressors, causing wear and tear on the body; At the most basic level, when there is low demand, the body
in other words, it is the “the price the body pays when exposed becomes deconditioned, and performance is decreased. With
to chronic stressors resulting in repeated overactivation of the maximum, optimal demand and physical training (i.e., bal-
10
neuroendocrine and immune systems.” The normal physio- anced), maximum performance will be reached, requiring nor-
logical response of an individual to a given stressor occurs for mal rest periods and recovery to be sustained. These training
a short interval and is then turned off once the stressor has levels can be exceeded for short periods, leading to a temporary
abated. However, when an individual’s ability to cope with decline in performance but ultimately resulting in improved
environmental challenges is exceeded, allostatic overload de- performance. This state is known as functional overreaching
velops as a transition to an extreme state in which the neuro- and is a positive adaptation used by athletes who must perform
endocrine and immune systems are repeatedly activated and at supra-maximal levels. To maintain performance and pre-
buffering protective factors are inadequate. 10,13 vent injury, these supramaximal training and performance ep-
isodes must be followed by complete recovery (approximately
Four primary biomarkers measure allostatic load/overload. 2 weeks). 6,28-31 When supramaximal demands are prolonged
These consist of 12-hour integrated measures of the hypotha- and repeated without adequate recovery, performance will de-
lamic-pituitary-adrenal (HPA) axis activity and sympathetic cline, and the body will show signs of increased wear and tear.
6
nervous system activity: (1) cortisol, (2) adrenaline, (3) nor- This is known as NFO, 6,28-32 defined as a training-specific con-
adrenaline, and (4) dehydroepiandrosterone (DHEA). These dition in which there are negative psychological and hormonal
biomarkers accurately measure HPA neuroendocrine responses disruptions (e.g., low testosterone/high cortisol levels) and de-
32
to stress. 10,20 The secondary biomarkers that indicate allostatic creased performance, leading to overtraining syndrome.” In
load/overload include (1) systolic blood pressure measure- this state, the body requires a more prolonged recovery period
ment, (2) diastolic blood pressure measurement, (3) waist-hip to restore maximal performance and lessen the risk of injury.
ratio, (4) total cholesterol level, (5) high-density lipoprotein NFO commonly occurs in SOs, when mission demands make
cholesterol level, and (6) blood sugar levels. Interestingly, the it impossible to gain recovery during deployments. When
10
four primary markers of allostatic load are considered equally NFO persists over longer periods, OTS will develop. OTS is
influential in predicting mortality over 4 years compared with a chronic condition in which health and performance decline
the secondary outcomes of allostatic load. 10,19 further. 6,28,33 The symptoms of OTS may include diminished
performance, increased morning resting heart rate (HR), al-
18
According to Guidi et al. and Davies, allostatic load/over- terations in hormonal status, marked weight reduction, lack
11
load is not an actual physiological principle but repeated or of improved training status, increased vulnerability to inju-
lengthy deviations from homeostasis. Chronic negative health ries, diminished appetite, restlessness, disruption in circadian
consequences may result from prolonged allostatic load/over- rhythm, general lethargy, decreased self-esteem, emotional in-
load caused by overexposure to stressors (e.g., repeated de- security, and depressed mood. 34
ployments, work, family, social), leading to hypertrophy of the
adrenals and hyperemia, hemorrhagic erosive gastritis/ulcers, Finally, a more non–training-specific concept known as under-
and atrophy of the thymus and lymph nodes, collectively re- recovery syndrome (URS) is a broader condition of insuffi-
ferred to as the “stress triad.” Over time, chronic stress can cient recovery. URS develops when there is an imbalance be-
21
slowly degrade the physical and mental attributes of SOs while tween daily life demands (e.g., work, family, social life) and
increasing their vulnerability to overuse injuries. 4,5,22-24,25-26 restoration. 28,31,32 In other words, the imbalance occurs when
The health and efficiency of what is referred to as the “hu- continuous, excessive psychological or physiological demands,
man motor” are markedly impacted by the brain’s increased whether perceived or real, exceed those of recovery, lead-
energy demands and chronic physiological and psychological ing to psychological, neurophysiological, and physiological
stress. 13,27 degradation. 9,28,32
Given the unique training and deployment burdens and result- We posit that progressive, ongoing fatigue can result in long-
ing chronic stress, a unified understanding of the consequences term under-recovery and underperformance, further placing
of SO life is beginning to emerge. A recent observational study SOs at increased risk of acute and chronic decrements in phys-
by Frueh et al. found a distinctive pattern of physiological ical, psychological, neuroendocrine, and immunological sys-
9
and psychological conditions in the Special Forces population. tems. Therefore, we propose a theoretical continuum model
Over 6 years, clinicians in this study observed that SOs suffer synthesizing the incremental stages leading to these progressive
from unusually high allostatic loads. High allostatic load and degradations (Figure 2). This model displays the steps leading
overexposure to endocrine, neural, and immune stress medi- to URS/OTS and elucidates the importance of recovery/resto-
ators can adversely affect various organ systems, manifesting ration following an overload event (e.g., deployment, rigorous
into disease. 9,13 Frueh et al. concluded that, because of con- training cycles), leading to super-compensation, whereby the
9
tinuous, long-term exposure to extreme environmental con- individual has a higher performance capacity than they did be-
ditions and training, traditional medical models of care are fore the overload event. Inadequate recovery may result in al-
frequently not effective in treating the interrelated functional lostatic imbalance, requiring a recovery period of days, weeks,
performance and health deficiencies of SOs. Thus, to ensure months, or years to regain peak performance. 11,30,31,35 This the-
the health and performance readiness of SOs, future research- oretical continuum model has yet to be substantiated within
ers should focus their efforts on early detection through the the SO community and thus deserves extensive exploration.

142 | JSOM Volume 22, Edition 2 / Summer 2022