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158 Biobehavioral Resilience to Stress

in vigor and motivation (Friedl, 2005; Zitzmann, Faber & Nieschlag, 2006).
This stress-related effect on testosterone secretion has been used by some to

justify the use of anabolic steroid “hormone replacement” treatment during

stressful athletic training. The behavioral effects (i.e., aggressiveness) may be

even more important as a competitive advantage than are more commonly
cited physical effects such as increased muscle mass and neuromuscular

strength (Friedl, 2005; Pope, Kouri & Hudson, 2000). In older men, testos-
terone supplementation is advocated as a strategy to maintain vitality and
counter depression (Pope, Cohane, Kanayama, Siegel & Hudson, 2003). It
is possible that effects of testosterone on male aggressiveness and motiva-

tion are mediated through cortical and subcortical dopaminergic systems
involved in reward and fear extinction (Hannan, Friedl & Plymate, 1990;
Hannan, Friedl, Zold, Kettler & Plymate, 1991). Habitual exercise has also
been hypothesized to play an important role in activating these or similar
mechanisms (Gilbert, 1995). Exercise and stimulants (e.g., cocaine, amphet-
amines, caffeine) may also exert their effects by related mechanisms, par-

ticularly the DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of
32 kD) signaling pathways (Bastia & Schwarzschild, 2003) (Figure 7.3).*
Dopaminergic systems appear to be central to coping ability and
higher order cognitive functioning under stress (Previc, 2005). Addi-
tional characterization of mechanisms, which are common for the eff ects
of many drugs, types of behavior, external stimuli, and stressors, will
likely help to elucidate key factors of resilience and its possible behav-
ioral outcomes (e.g., motivation, risk taking, motor activity). Additional
research in this area is needed to achieve potentially broad scientifi c and

applied benefit. A clear understanding of psychological resilience to stress,
and of its physiological basis, would certainly be counted among the most
useful and important discoveries of contemporary scientific inquiry in the

field of human performance.

Psychosocial Modifiers of Environmental Stress and Health

Although not yet fully mapped or understood, there certainly exists an impor-
tant relationship between perceived stress and health outcome. Indicators of
cumulative stress load have been used to demonstrate dramatic eff ects on
health, especially as associated with immune function, cardiovascular dis-
ease, and death. For example, in a carefully controlled study involving delib-
erate exposure to the common cold virus, Cohen, Tyrrell, and Smith (1991)
demonstrated that with increasing levels of life stress, there occurs a linear

* Caffeine acts through adenosine 2A receptors to produce physical and mental perform-
ance enhancing effects (Kalda, Yu, Oztas & Chen, 2006).

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