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The purpose of this study was to examine the effects of a mental challenge on cardiovascular and endocrine [epinephrine (EPI), norepinephrine (NE), and cortisol (CORT)] responses to subsequent low-intensity physical exertion. Twelve males (23.25±0.45 years) completed three sessions, including a graded exercise test on a cycle ergometer and two counter-balanced mental stress trials. In the mental challenge-control condition (MC), participants sat quietly for 20 min following a 20 min mental challenge whereas in the mental challenge-exercise condition (MEC) subjects cycled at 35% of maximal oxygen consumption (VO2max) following the mental challenge. Repeated-measures ANOVAs were used to assess state anxiety (SAI), cardiovascular variables, EPI, NE, and CORT levels across time between conditions. Participants reported significantly greater increases in SAI scores immediately after the mental challenge, which then decreased post-challenge in both conditions. Neither EPI or NE demonstrated an alteration in levels in either condition, but CORT significantly increased after the mental challenge in both conditions and then maintained a significantly greater level during the MEC compared to the MC condition from midexercise through 15 min of recovery. Area-under-the-curve calculations for CORT was significantly greater in the MEC compared to the MC. Results suggest that the initial mental challenge may have acted to enhance the overall adrenal response to the subsequent anticipation of and actual participation in the low-level physical challenge.

The purpose of this study was to examine the effects of concurrent physical and mental challenge on stress hormones and indicators of vascular function in firefighters. Twelve professional firefighters exercised at 60% VO(2max) while participating in a computerized Fire Strategies and Tactics Drill (FSTD-fire strategies condition [FSC]), and again at the same intensity without the mental challenge (EAC). No differences in the amount of work performed between conditions existed, although the FSC resulted in greater perceptions of overall workload. Epinephrine and norepinephrine demonstrated significant interaction effects with elevated levels during the FSC. Cortisol responses were significantly elevated across time and for the FSC. Positive correlations were found between cortisol and interleukin-6, endothelin-1, and thromboxane-B(2), and a negative correlation between interleukin-6 and thromboxane-B(2). These results suggest that concurrent challenges results in exacerbated responses of stress hormones and suggests mechanisms that could contribute to the prevalence of cardiovascular events among firefighters., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The purpose of this study was to examine the changes in catecholamines (epinephrine [EPI] and norepinephrine [NE]), interleukin-2 (IL-2) and a biomarker of oxidative stress (8-isoprostane) in healthy individuals who were exposed to a dual challenge (physical and psychological stress). Furthermore, this study also examined the possible relationships between catecholamines (NE and EPI) and 8-isoprostane and between IL-2 and 8-isoprostane following a combined physical and psychological challenge. Seven healthy male subjects completed two experimental conditions. The exercise-alone condition (EAC) consisted of cycling at 60% VO(2max) for 37 min, while the dual-stress condition (DSC) included 20 min of a mental challenge while cycling. DSC showed greater EPI and 8-isoprostane levels (significant condition by time interaction). NE and IL-2 revealed significant change across time in both conditions. In addition, following dual stress, EPI area-under-the-curve (AUC) demonstrated a positive correlation with NE AUC and IL-2 AUC. NE AUC was positively correlated with IL-2 AUC and peak 8-isoprostane, and peak IL-2 was positively correlated with peak 8-isoprostane in response to a dual stress. The potential explanation for elevated oxidative stress during dual stress may be through the effects of the release of catecholamines and IL-2. These findings may further provide the potential explanation that dual stress alters physiological homeostasis in many occupations including firefighting, military operations and law enforcement. A greater understanding of these responses to stress can assist in finding strategies (e.g. exercise training) to overcome the inherent psychobiological challenges associated with physically and mentally demanding professions.

The purpose of this study examined the changes in heart rate (HR), catecholamines (NE, EPI) and percentages of blood lymphocyte subsets (CD3+ T cells, CD3+CD4+ helper T cells, CD3+CD8+ cytotoxic T cells, CD3- CD56+ NK cells, CD4/CD8 ratio, CD19+ B cells, and total lymphocytes [NK cells+T cells+B cells]) in firefighters exposed to a computerized firefighting strategies and tactics decision-making challenge while participating in moderate intensity exercise. Furthermore, this study also examined the possible relationships between catecholamines (NE and EPI) and blood lymphocyte subsets following combined mental and physical challenge. Ten professional male firefighters participated in two counterbalanced exercise conditions on a cycle ergometer: (1) 37min of cycle ergometry at 60% VO(2max) (exercise alone condition; EAC) and (2) 37min of cycle ergometry at 60% VO(2max) along with 20min of a computerized firefighting strategies and tactics decision-making challenge (firefighting strategies condition; FSC). FSC elicited significantly greater HR, NE, and EPI when compared to EAC. Both EAC and FSC elicited increases in CD3- CD56+ NK cells. The percentages of CD3+ T cells, CD3+CD4+ helper T cells, CD4/CD8 ratio, CD19+ B cells, and total lymphocytes were lower immediately following both conditions. Following dual challenge NE AUC was negatively correlated with percentage of CD19+ B cells immediately post challenge, and HR was negatively associated with the percent change in the CD4/CD8 ratio from pre to post challenge. These elevations in NE and heart rate simultaneously in response to the dual challenge suggest greater sympathetic activation that in turn would possibly explain the alteration in the distribution of lymphocyte subsets., (Published by Elsevier Inc.)

The purpose of this study was to examine the changes in heart rate (HR), catecholamines (norepinephrine [NE] and epinephrine [EPI]), pro-inflammatory cytokines (interleukin-2 [IL-2] and interleukin-6 [IL-6]), and lymphocytes (CD8+ and CD56+) in firefighters exposed to a decision-making challenge (firefighting strategies and tactics drill) while participating in moderate intensity exercise. Nine professional male firefighters participated in two counterbalanced exercise conditions on a cycle ergometer: (1) 37 min of cycle ergometry at 60% VO(2max) (exercise alone condition ; EAC) and (2) 37 min of cycle ergometry at 60% VO(2max) along with 20 min of a computerized firefighting strategy and tactics decision-making challenge (firefighting strategy condition; FSC). FSC elicited significantly greater HR, NE, EPI, and IL-2 when compared to EAC. These elevations may suggest that the addition of a mental challenge to physical stress can alter the hormonal and immunological responses during firefighting. In addition, this evidence provides insight into the possible mechanisms that explain the link between physical activity, psychological stress, and stress-related diseases., (Published by Elsevier B.V.)

The purpose of this study was to examine the cardiorespiratory (CR) and stress hormone responses to a combined physical and mental stress. Eight participants (VO2(max) = 41.24 +/- 6.20 ml kg(-1) min(-1)) completed two experimental conditions, a treatment condition including a 37 min ride at 60% of VO2(max) with participants responding to a computerized mental challenge dual stress condition (DSC) and a control condition of the same duration and intensity without the mental challenge exercise alone condition (EAC). Significant interactions across time were found for CR responses, with heart rate, ventilation, and respiration rate demonstrating higher increases in the DSC. Additionally, norepinephrine was significantly greater in the DSC at the end of the combined challenge. Furthermore, cortisol area-under-the-curve (AUC) was also significantly elevated during the DSC. These results demonstrate that a mental challenge during exercise can exacerbate the stress response, including the release of hormones that have been linked to negative health consequences (cardiovascular, metabolic, autoimmune illnesses).

Exercise elicits intensity-dependent increases in epinephrine (Epi), norepinephrine (NE), cortisol (CORT), and lactate (Lac), whereas at rest the hormonal responses to mental stress include increases in Epi, NE, and CORT, but not Lac. Additionally, elevations in CORT at rest are associated with negative affect. Finally, as exercise intensity increases, perceptions of effort (RPE) increase and affect becomes more negative. The purpose of this study was to examine the responses of Epi, NE, CORT, Lac, RPE, and affect during incremental increases in exercise to maximum. Seven highly-trained male runners completed a discontinuous treadmill protocol that included 10 minutes at 60%, 10 minutes at 75%, 5 minutes at 90%, and 2 minutes at 100% of VO2max. Blood samples were collected through an intravenous catheter before, during, and following exercise during the experimental condition, and during a time-matched control condition. RPE and affect were assessed just prior to each blood draw. The Epi, NE, CORT, and Lac displayed the expected incremental increases, however affect became more negative at higher exercise intensities, and RPE increased as exercise intensity increased. Data suggest that CORT follows the same pattern of response to graded exercise as affect. Since perceptual and affective responses to exercise are associated with motivation, these documented negative affective shifts during exercise should be considered in order to develop strategies that lead to enhanced exercise adherence and performance.