Trained versus untrained men: different immediate post-exercise responses of pituitary adrenal axis. A preliminary study

Sexual dimorphism in exercise-induced response on steroid hormones to a 24-week supervised concurrent training intervention

BACKGROUND

Steroid hormones are key mediators of adaptative responses to exercise, a stimulus that may concurrently affect their blood concentrations. However, the chronic endocrine adaptations and whether these potential changes are dependent on exercise intensity remain undetermined. Moreover, it is also unknown if the exercise-induced effects on steroid hormonal status are related to the participant' sex.

METHODS

This study aimed to investigate the intensity effects of a 24-week supervised concurrent training intervention on steroid hormones in sedentary young men and women. A total of 106 untrained young adults (68% women) aged 18-25 years were randomly assigned to one of the three groups: (I) Control group (no exercise; n = 35); (II) Ex-Moderate group (concurrent training at moderate intensity; n = 36); (III) Ex-Vigorous group (concurrent training at vigorous intensity; n = 35). Steroid hormones (i.e. cortisol, testosterone and dehydroepiandrosterone sulfate (DHEAS)) were measured in plasma through a chemiluminescent method. Body composition parameters were determined using a dual-energy X-ray absorptiometry scanner.

RESULTS

No significant changes in steroid hormones levels were observed after the intervention (all p ≥ .129). However, a time x group interaction was noted in the testosterone/cortisol ratio (T/C ratio) only in women (p = .044). Concretely, our data showed a significant decrement of T/C ratio in both the Ex-Moderate group and in the Ex-Vigorous compared with the control group (Δ = -24.2 ± 2.0% and Δ = -38.9 ± 45.4%, respectively).

CONCLUSION

Our 24-week supervised concurrent training intervention showed no significant changes in steroid hormone levels. However, a significant decrement of T/C ratio was observed only in women, indicating a sexual dimorphism in the effect on T/C ratio.

Plasma and salivary hormone responses to a 30-min exercise stress test in young, healthy, physically active females

Overreaching, a consequence of intensified training, is used by athletes to enhance performance. A blunted hormonal response to a 30-min interval exercise stress test (55/80) has been shown in males after intensified training, highlighting cortisol and testosterone as potential biomarkers of overreaching. Despite accounting for ~50% of the population, studies into hormonal responses to exercise in females are lacking. The menstrual cycle and oral contraceptives profoundly affect hormonal responses, necessitating separate investigations into the female response to the same exercise-stress test. On three separate visits, 13 females (6 oral contraceptive users, 7 eumenorrheic) completed a VO2max test, resting control trial, and 55/80 stress test. The 55/80 involves alternating between 1 min at 55% VO2max and 4 min at 80% VO2max. Blood and saliva were collected pre, post, and 30 min post-55/80, and at coinciding time points during the resting control trial. Plasma progesterone, estrogen, and plasma and salivary cortisol and testosterone were analyzed via ELISA. A significant elevation of salivary and plasma cortisol (~141% and ~87%, respectively, p < 0.001), salivary testosterone (~93%, p < 0.001), and plasma progesterone (~58%, p = 0.004) were evident from pre- to post-55/80. Plasma testosterone remained unchanged. Hormonal responses were attenuated in oral contraceptive users. The 55/80 induces hormonal elevations in females, similar in magnitude as males.

Hand cooling induces changes in the kinetics of oxygen uptake

The objective of this investigation was to assess the impact of elevated catecholamine concentrations, induced through cold-water hand immersion, on the oxygen consumption (V̇O2) kinetics during intense exercise, and to contrast this effect with that of the priming effect. Ten active participants underwent three 8-minute constant work rate exercises (CWR) at ∆25%, with one CWR preceded by hand cooling (2 min at 0 °C, HC) and two consecutive CWR to induced priming effect on the second bout (SB). Pulmonary gas exchange and blood samples were analyzed to measure levels of epinephrine (E) and norepinephrine (NE). Results demonstrated a significant increase in the primary phase amplitude of V̇O2 kinetics in response to both hand HC (33.9 mL.min-1.kg-1; CI [32.2;35.7], p < 0.001) and SB (34.6 mL.min-1.kg-1; CI [33.0;36.3], p < 0.001) relative to the control (32.7 mL.min-1.kg-1; CI [31.5;35.1]). Additionally, the amplitude of the V̇O2 slow component was reduced for both HC (3.2 mL.min-1.kg-1; CI [2.2;4.1], p = 0.018) and SB (2.9 mL.min-1.kg-1; CI [1.8;4.2], p = 0.009) in comparison to control (3.9 mL.min-1.kg-1; CI [2.9;4.2]). These findings suggest that the increase in E and NE induced by hand cooling prior to exercise modifies V̇O2 kinetics in a manner akin to the priming effect. This research underscores the potential role of catecholamines in facilitating the priming effect and its subsequent impact on V̇O2 kinetics. However, further studies are necessary to clearly establish this link.

Endocrine responses of the stress system to different types of exercise

Physical activity is an important part of human lifestyle although a large percentage of the population remains sedentary. Exercise represents a stress paradigm in which many regulatory endocrine systems are involved to achieve homeostasis. These endocrine adaptive responses may be either beneficial or harmful in case they exceed a certain threshold. The aim of this review is to examine the adaptive endocrine responses of hypothalamic-pituitary-adrenal axis (HPA), catecholamines, cytokines, growth hormone (GH) and prolactin (PRL) to a single bout or regular exercise of three distinct types of exercise, namely endurance, high-intensity interval (HIIE) and resistance exercise. In summary, a single bout of endurance exercise induces cortisol increase, while regular endurance exercise-induced activation of the HPA axis results to relatively increased basal cortisolemia; single bout or regular exercise induce similar GH peak responses; regular HIIE training lowers basal cortisol concentrations, while catecholamine response is reduced in regular HIIE compared with a single bout of HIIE. HPA axis response to resistance exercise depends on the intensity and volume of the exercise. A single bout of resistance exercise is characterized by mild HPA axis stimulation while regular resistance training in elderly results in attenuated inflammatory response and decreased resting cytokine concentrations. In conclusion, it is important to consider which type of exercise and what threshold is suitable for different target groups of exercising people. This approach intends to suggest types of exercise appropriate for different target groups in health and disease and subsequently to introduce them as medical prescription models.

The effect of acute exercise on the cortisol awakening response

The effects of acute exercise on the cortisol awakening response (CAR), characterized by the rapid increase in cortisol concentrations within the 30-45 min following sleep offset has yet to be fully elucidated. Thus, our study investigated the effects of late-evening acute exercise on the CAR the following morning. We hypothesized that exercise would have a significant effect on the CAR the following morning. Twelve participants (mean (SD): age = 23 (4) years; mass = 76.8 (8.7) kg; height = 175.6 (5.0) cm; [Formula: see text]O2max = 48.9 (7.5) ml.kg^-1.min^-1) reported to the laboratory in the evening (1800 h) on two occasions and were randomly assigned to either exercise for one hour (70-75% of maximal power output) or rest condition. Blood and saliva samples were assayed for cortisol. Mixed-effects models determined the effect of exercise on the cortisol response post-waking in both blood and saliva. Participants demonstrated an average exercise-induced increase in circulating cortisol of 477.3%, with actual mean (SD) heart rate relative to maximum of 87.04% (6.14%). Model results demonstrated a negative effect for exercise condition when modeling the serum and salivary cortisol responses to awakening via a quadratic growth model (serum, β_Condition = - 42.26 [95% CI - 64.52 to - 20.01], p < 0.001; saliva, β_Condition = - 11.55 [95% CI - 15.52 to - 7.57], p < 0.001). These results suggest that cortisol concentrations in saliva and blood are significantly lower the morning following a prior evening exercise session. Therefore, the CAR may serve as a useful biomarker to monitor responses to exercise training, although the underlying mechanism for these decreases in the CAR should be investigated further.

Time-course effects of functional fitness sessions performed at different intensities on the metabolic, hormonal, and BDNF responses in trained men

Background

To investigate the time-course effects of a self-regulated training session (performed at an rating perceived exertion of 6/10), all-out session, and a control session on the metabolic, hormonal, and brain derived neurotrophic factor (BDNF) responses in Functional-Fitness (FFT) participants.

Methods

In a randomized, crossover fashion, eight healthy males (age 28.1 ± 5.4 years old; body mass 77.2 ± 4.4 kg; VO_2max: 52.6 ± 4.6 mL.(kg.min)⁻¹; 2000 m rowing test 7.35 ± 0.18 min; 1RM back squat 135.6 ± 21.9 kg) performed a FFT session under two different conditions: all-out, or with the intensity controlled to elicit an rating perceived exertion (RPE) of 6 in the Borg 10-point scale (RPE6). A control session (no exercise) was also completed. Metabolic (lactate and creatine kinase), hormonal (testosterone and cortisol), and BDNF responses were assessed pre, post-0 h, 1 h, 2 h and 24 h after the sessions.

Results

Creatine kinase concentrations were significantly higher (p ≤ 0.05) after 24 h for both training sessions. Total and free testosterone concentrations were lower post-2 h for all-out when compared to the RPE6 session (p ≤ 0.05). Serum cortisol concentration increased post-0 h (p = 0.011) for RPE6 and post-0 h (p = 0.003) and post-1 h (p = 0.030) for all-out session when comparing to baseline concentrations. BDNF was significantly higher (p = 0.002) post-0 h only for the all-out session when compared to baseline. A positive correlation between blood lactate concentrations and BDNF (r = 0.51; p = 0.01) was found for both effort interventions.

Conclusions

A single FFT session when performed in all-out format acutely increases the concentrations of serum BDNF. However, physiological stress markers show that the all-out session requires a longer recovery period when compared to the RPE6 protocol. These findings can be helpful to coaches and practitioners design FFT session.

Acute exercise increases immune responses to SARS CoV-2 in a previously infected man

Evidence is emerging that exercise and physical activity provides protection against severe COVID-19 disease in patients infected with SARS-CoV-2, but it is not known how exercise affects immune responses to the virus. A healthy man completed a graded cycling ergometer test prior to and after SARS-CoV-2 infection, then again after receiving an adenovirus vector-based COVID-19 vaccine. Using whole blood SARS-CoV-2 peptide stimulation assays, IFN-γ ELISPOT assays, flow cytometry, ex vivo viral-specific T-cell expansion assays and deep T-cell receptor (TCR) β sequencing, we found that exercise robustly mobilized highly functional SARS-CoV-2 specific T-cells to the blood compartment that recognized spike protein, membrane protein, nucleocapsid antigen and the B.1.1.7 α-variant, and consisted mostly of CD3+/CD8+ T-cells and double-negative (CD4-/CD8-) CD3+ T-cells. The magnitude of SARS-CoV-2 T-cell mobilization with exercise was intensity dependent and robust when compared to T-cells recognizing other viruses (e.g. CMV, EBV, influenza). Vaccination enhanced the number of exercise-mobilized SARS-CoV-2 T-cells recognizing spike protein and the α-variant only. Exercise-mobilized SARS-CoV-2 specific T-cells proliferated more vigorously to ex vivo peptide stimulation and maintained broad TCR-β diversity against SARS-CoV-2 antigens both before and after ex vivo expansion. Neutralizing antibodies to SARS-CoV-2 were transiently elevated during exercise after both infection and vaccination. Finally, infection was associated with an increased metabolic demand to defined exercise workloads, which was restored to pre-infection levels after vaccination. This case study provides impetus for larger studies to determine if these immune responses to exercise can facilitate viral clearance, ameliorate symptoms of long COVID syndrome, and/or restore functional exercise capacity following SARS-CoV-2 infection.

The Effect of High-Intensity Exercise on Changes in Salivary and Serum Cortisol Proportion Dynamics

Typically, salivary cortisol is reported as 5–10% of total cortisol, but the stability of this proportion and the effect of exercise on the 24-h profile is unclear. Therefore, this study investigated the circadian rhythm of the proportion of serum cortisol represented by salivary cortisol, and the impact of acute high-intensity exercise. Recreationally trained males (n = 8, age = 25.7 ± 2.4 years, height = 174.7 ± 7.8 cm, mass = 69.8 ± 12.1 kg) completed two 24-h profiles (rest and exercise conditions) for serum (Q60) and salivary (Q120) cortisol. Exercise consisted of 5 × 30 s sprinting intervals on the cycle ergometer. Cortisol was assessed using commercially available assays. The proportion (Cprop) of serum cortisol (Cser) represented by salivary cortisol (Csal) was calculated as [Cprop = Csal/ Cser × 100]. Multilevel growth models tested for trends across the 24-h profile. The highest relation between Cser and Csal was observed at 08:00 AM (r = 0.90). The average Cprop was 5.95% and demonstrated a circadian profile characterized by a cubic model. Acute exercise did not alter Cser, Csal, or Cprop. Thus, the proportion of Cser represented by Csal changes across a 24-h period and should be accounted for if using salivary cortisol to reflect circadian output of cortisol.

Effect of High-Intensity Interval Training Versus Small-Sided Games Training on Sleep and Salivary Cortisol Level

PURPOSE

The authors compared sleep quality and salivary cortisol concentration after high-intensity interval training (HIIT) and small-sided games (SSGs) performed at the habitual training time in nonprofessional male soccer players.

METHODS

A total of 32 players (age = 24 [6] y, height = 1.77 [0.06] m, and body mass = 75 [12] kg) were randomized into an HIIT group or an SSG group. Actual sleep time, sleep efficiency (SE), sleep latency, immobility time (IT), moving time (MT), and fragmentation index were monitored using actigraphy before (PRE) and 2 nights after (POST 1 and POST 2) the training session. Salivary cortisol levels were measured before (PRE) and after (POST) training. Cortisol awakening response was evaluated.

RESULTS

Significant intragroup differences in the HIIT group were noted for actual sleep time (P < .0001), SE (P < .0001), sleep latency (P = .047), IT (P < .0001), MT (P < .0001), and fragmentation index (P < .0001) between PRE and POST 1 and for SE (P = .035), IT (P = .004), MT (P = .006), and fragmentation index (P = .048) between PRE and POST 2. Intergroup differences for actual sleep time (P = .014), SE (P = .048), IT (P < .0001), and MT (P = .046) were observed between the HIIT and the SSGs group at POST 1 were detected. Significant intragroup variations were observed in PRE and POST salivary cortisol levels (P < .0001 for HIIT; P = .0003 for SSGs) and cortisol awakening response (P < .0001 for HIIT; P < .0001 for SSGs). Significant intergroup differences between the HIIT and the SSGs group were found at POST (P < .0001) and in cortisol awakening response (P = .017).

CONCLUSIONS

Changes in actigraphy-based sleep parameters and salivary cortisol levels were greater after an acute session of HIIT than SSGs in this sample of nonprofessional male soccer players.

Gonadal hormones may predict structural bone fragility in elite female soccer player

Purpose: This study determined the impact of menstrual status on bone tissue in elite post-pubertal female soccer players over an entire season.Methods: Fifty-one elite female soccer players participated. At baseline, forty-one were assigned to the low hormonal androgenic profile (low-HAPL) and 10 to the high hormonal androgenic profile (high-HAPL).Results: An 8-month training program led to increased bone mineral density content (p<0.05). The low-HAPL athletes improved the Narrow neck average cortical thickness (ACT) by 1.4% and reduced the corresponding Buckling ratio (BR) by 2.6%, thus decreasing the fracture risk (p<0.05). The high-HAPL athletes decreased the Narrow neck ACT by 5.4% and increased the BR by 2.6%, increasing fracture risk (p<0.05). Differences were assigned as being "very likely beneficial" for the low-HAPL athletes, supported by very large (d=3.41) and large (d=1.58) effect sizes for the Narrow neck ACT and BR, respectively.Conclusion: A season of soccer training has induced bone geometry improvements in adolescent females. Bone health parameters improved in the two clusters. However, high-HAPL athletes decreased its resistance to loading compare to low-HAPL athletes. Even if female players do not present clinical symptoms related to their hormonal status, sport medicine physicians should pay attention to their structural bone fragility.

Impact of physical activity on monocyte subset CCR2 expression and macrophage polarization following moderate intensity exercise

Coronary artery disease (CAD) is an immune-mediated disease in which CCR2 attracts classical, intermediate, and non-classical monocytes to the arterial intima where they differentiate to macrophages. Balance between pro-inflammatory M1 and anti-inflammatory M2 macrophages contributes to CAD prevention. Moderate to vigorous intensity physical activity (MVPA) elicits an immune response and reduces the incidence of CAD, however, the impact of prior MVPA on monocyte subset CCR2 expression and macrophage polarization following acute exercise is unknown.

Purpose

To determine the impact of physical activity status on monocyte subset CCR2 surface expression and macrophage polarization in response to an acute bout of moderate intensity cycle ergometry.

Methods

24 healthy women and men (12 high physically active [HIACT]: ≥1500 METmin/wk MVPA & 12 low physically active [LOACT]: <600 METmin/wk MVPA) underwent an acute moderate intensity (60% VO2peak) bout of cycle ergometry for 30 ​min. Blood samples were collected prior to (PRE), immediately (POST), 1 ​h (1H), and 2 ​h (2H) following exercise. Monocyte CCR2 and macrophage CD86 (M1) and CD206 (M2) were analyzed by flow cytometry.

Results

Intermediate monocyte CCR2 decreased in response to exercise in the HIACT group (PRE: 11409.0 ​± ​1084.0 vs. POST: 9524.3 ​± ​1062.4; p ​= ​0.034). Macrophage CD206 was lower in the LOACT compared to the HIACT group at 1H (HIACT: 67.2 ​± ​5.6 vs. LOACT: 50.1 ​± ​5.2%; p ​= ​0.040). Macrophage CD206 at 1H was associated with both PRE (r ​= ​0.446, p ​= ​0.043) and POST (r ​= ​0.464, p ​= ​0.034) non-classical monocyte CCR2.

Conclusion

These data suggest that regular moderate to vigorous physical activity positively impacts both monocytes and macrophages following acute moderate intensity exercise and that this impact may contribute to the prevention of coronary artery disease.

Corticosterone in Lizard Egg Yolk Is Reduced by Maternal Diet Restriction but Unaltered by Maternal Exercise

When females face adverse environmental conditions, physiological changes, such as elevated corticosterone levels, to cope with the stressors may also impact their offspring. Such maternal effects are often considered adaptive and may "prime" the offspring for the same adverse environment, but maternal corticosterone levels do not always match that of the eggs produced. We examined how diet restriction and increased locomotor activity, via exercise training, affected steroid hormone levels of female green anole lizards, as well as the hormone levels in the yolk of their eggs. Diet restriction did not affect female hormone levels, but training increased corticosterone levels. Despite this, training did not affect yolk steroid levels, but eggs from females with diet restriction had lower corticosterone levels in yolk. This suggests that two common stressors, food shortage and increased locomotor activity, impact female physiology in a way that is not translated to her offspring.

Endocrine responses after a single bout of moderate aerobic exercise in healthy adult humans

Exercise is a stress stimulus for the human organism affecting the homeostatic mechanisms of the body, depending on the type, duration, intensity and frequency of exercise. The aim of this study was to determine the effects of a moderate aerobic exercise bout on the Hypothalamo-Pituitary-Adrenal (HPA) axis acute hormonal responses in healthy adult humans. Twelve healthy male and female volunteers (age: 30.6 ± 4.4 years), performed a single bout of a 30-minute aerobic exercise at 70% of VO2max on a treadmill, following standard diet. Blood samples were collected before (t0), at the end of the exercise bout (t30), and 30 min after the completion of exercise (t60). Serum adrenocorticotropic hormone (ACTH), cortisol (COR), aldosterone (ALDO) and renin (REN) were measured. One-way ANOVA was used for statistics. ACTH and COR decreased after exercise, reaching significance (p < 0.01) 30 min after the completion of the exercise bout. ALDO increased at the end of exercise and remained elevated 30 min after its completion. REN significantly increased at the end of exercise (p < 0.05) and remained elevated. The exercise regimen used in this study had beneficial effects on the stress axis, suggesting that specific exercise protocols can be characterised by mild physiological stress-inducing effects hence be prescribed for special diseased populations.

Acute Response to Endurance Exercise Stress: Focus on Catabolic/anabolic Interplay Between Cortisol, Testosterone, and Sex Hormone Binding Globulin in Professional Athletes

Background

Endocrine system plays a major role in both permissive and regulatory activities in order to adequately respond to physical stress of exercise. But level and direction of activation depend on many factors and are not easily interpreted.

Methods

We tested a group of male professional athletes (21 water polo players and 15 wrestlers), together with 20 sedentary controls matched by age. All participants took a continuous progressive exercise stress test on a treadmill until exhaustion and plateau of oxygen consumption (VO₂). Blood samples for cortisol, sex hormone binding globulin (SHBG) and testosterone were drawn in four time points: baseline (B), start of the test (S), point of maximal strain (MAX) and in the 3^rd minute of recovery period (R).

Results

Cortisol levels significantly increased in both groups, but the response between S and MAX was more pronounced in controls (p=0.036). The athletes had significantly higher levels of cortisol in all points in test, except during R (p=0.118), when their cortisol levels gradually started to decline. Significant increase in total testosterone was in great deal a consequence of increase in SHBG level (p<0.01 for both). Consequently, calculated free testosterone significantly decreased during test (p=0.008), and the drop was more pronounced in athletes. This was in concordance with significant correlation between SHBG and cortisol level demonstrated in athletes, but not in controls.

Conclusions

It seems that high intensity endurance exercise favors catabolic response, but the level of response highly depends on a previous level of training.

Effects of acute or chronic heat exposure, exercise and dehydration on plasma cortisol, IL-6 and CRP levels in trained males

This study examined the acute and chronic effects of euhydrated and hypohydrated heat exposure, on biomarkers of stress and inflammation. Eight trained males [mean (SD) age: 21 (3) y; mass: 77.30 (4.88) kg; V̇O_2max: 56.9 (7.2) mL kg^-1 min^-1] undertook two heat acclimation programmes (balanced cross-over design), once drinking to maintain euhydration and once with restricted fluid-intake (permissive dehydration). Days 1, 6, and 11 were 60 min euhydrated exercise-heat stress tests (40 °C; 50% RH, 35% peak power output), days 2-5 and 7-10 were 90 min, isothermal-strain (target rectal temperature: 38.5 °C) exercise-heat sessions. Plasma was obtained pre- and post- exercise on day 1, 2, and 11 and analysed for cortisol, interleukin-6 (IL-6), and C-reactive protein (CRP). Cortisol and CRP were also assessed on day 6. IL-6 was elevated following the initial (acute) 90 min isothermal heat strain exercise-heat exposure (day 2) with permissive dehydration ((pre exercise: 1.0 pg mL^-1 [0.9], post-exercise: 1.8 pg mL^-1 [1.0], P = .032) and when euhydrated (pre-exercise: 1.0 pg mL^-1 [1.4], post-exercise: 1.6 pg mL^-1 [2.1], P = .048). Plasma cortisol levels were also elevated but only during permissive dehydration (P = .032). Body mass loss was strongly correlated with Δcortisol (r = -0.688, P = .003). Although there was a trend for post-exercise cortisol to be decreased following both heat acclimation programmes (chronic effects), there were no within or between intervention differences in IL-6 or CRP. In conclusion, acute exercise in the heat increased IL-6 and cortisol only when fluid-intake is restricted. There were no chronic effects of either intervention on biomarkers of inflammation as evidenced by IL-6 and CRP returning to basal level at the end of heat acclimation.

Hormonal response to a non-exercise stress test in athletes with overtraining syndrome: results from the Endocrine and metabolic Responses on Overtraining Syndrome (EROS) - EROS-STRESS

OBJECTIVES

Overtraining syndrome (OTS) leads to worsened sports performance and fatigue. The pathophysiology of OTS has not been entirely elucidated, and there is a lack of accurate markers for its diagnosis. Changes in hormonal responses implicated in OTS were stimulated by exercise, which has limited their interpretation. Hence, we aimed to evaluate growth hormone (GH) and prolactin responses to a gold-standard and exercise-independent stimulation test, the insulin tolerance test (ITT).

DESIGN

Volunteers were recruited and divided into OTS-affected athletes (OTS), healthy athletes (ATL), and healthy non-active subjects (NCS) groups, after general and specific inclusion and exclusion criteria.

METHODS

We evaluated the responses of growth hormone (GH) and prolactin to the ITT, and compared between groups.

RESULTS

A total of 51 subjects were included (OTS, n=14, ATL, n=25, and NCS, n=12). OTS disclosed significantly lower basal levels of GH (p=0.003) and prolactin (p=0.048), and GH (p=0.001) and prolactin (p<0.001) responses to ITT (p=0.001), compared to ATL, but similar to NCS. OTS showed a later rise in GH levels in response to hypoglycemia, compared to ATL, but not to NCS. We suggest cutoffs for GH and prolactin levels to aid in the diagnosis of OTS.

CONCLUSIONS

OTS-affected athletes show reduced GH and prolactin basal levels and responses to a non-exercise stress test compared to healthy athletes, but not to sedentary subjects.

Exercise and the Cortisol Awakening Response: A Systematic Review

BACKGROUND

The cortisol awakening response (CAR) has been used as a biomarker of stress response in a multitude of psychological investigations. While a myriad of biochemical responses have been proposed to monitor responses to exercise training, the use of CAR within the exercise and sports sciences is currently limited and is a potentially underutilized variable. Therefore, the purpose of this review was to collate studies that incorporate both exercise and CAR, in an effort to better understand (a) whether CAR is a useful marker for monitoring exercise stress and (b) how CAR may be most appropriately used in future research.

METHODS

A systematic review of the literature was conducted, following PRISMA guidelines. Searches were conducted using PubMed, SportDISCUS, Scopus, and PsychInfo databases, using search terms related toCAR and exercise and physical activity.

RESULTS

10,292 articles were identified in the initial search, with 32 studies included in the final analysis. No studies investigated the effects of laboratory-controlled exercise on CAR. Variable effects were observed, possibly due to inconsistencies in study design, methodology, population, and CAR analysis. The available literature suggests a threshold of exercise may be required to alter the HPA axis and affect CAR. Moreover, CAR may represent a combination of previous exercise load and upcoming stress, making current interpretation of field-based observational research challenging.

CONCLUSIONS

More research is needed to fully elucidate the influence of exercise on CAR and address a number of gaps in the literature, including controlling exercise load, consistent sample collection, and CAR calculation and analysis.

Evaluation of efforts in untrained Wistar rats following exercise on forced running wheel at maximal lactate steady state

[Purpose]

We aimed to examine the effect of running speed on metabolic responses associated with maximal lactate steady state (MLSS) in rats during forced running wheel (FRW) exercise.

[Methods]

Forty male adult Wistar rats were divided into seven groups. The blood lactate threshold and peak running speed were determined for an incremental power test group. Five groups participated in constant power tests at intensities 10, 13, 14.5, 16, and 17.5 m/min to determine MLSS and a non-exercise group was chosen as the control. Animals were euthanized immediately after constant power tests and their corticosterone, non-esterified fatty acid (NEFA), blood glucose, and creatine kinase (CK) levels analyzed. The differences among groups were identified by one-way analysis of variance (p < 0.05).

[Results]

Blood lactate threshold corresponded a running intensity of 15 m/min, while MLSS was determined to be 16 m/min. Serum corticosterone concentrations were significantly higher in 14.5, 16, and 17.5 m/min groups (298.8±62, 338.3±65, and 354±26 nM, respectively) as compared to that in the control group (210.6±16 nM). Concentrations of NEFA observed in groups 13, 14.5, 16, and 17.5 m/min (662.8±24, 702.35±69, 718.4±34, and 752.8±77 μM, respectively) were significantly higher than those in 10 m/min and control groups (511.1±53 and 412.1±56 μM, respectively). The serum CK concentration recorded for group 17.5 m/min (372.4±56 U/L) was higher than those recorded for other groups.

[Conclusion]

The speed above 16 m/min on FRW resulted in increased physiological demands and muscle damage in untrained healthy Wistar rats.

Cortisol and testosterone dynamics following exhaustive endurance exercise

PURPOSE

Cortisol (C) and testosterone (T) are impacted significantly by prolonged endurance exercise with inverse responses. Increases in C are witnessed concurrently with decrements in T, possibly impacting recovery. This study was conducted to assess the dynamics of C and free T (fT) concentration and recovery time following an exhaustive endurance exercise session (EES).

METHODS

12 endurance-trained males (X ± SD: VO2max 66.3±4.8 ml/kg/min, age 22.8 ± 3.1 years, body fat 11.0 ± 1.4 %, training 7.1 ± 3.2 years) completed a treadmill EES at ventilatory threshold (74.7 ± 4.6 % of VO2max; 96.9 ± 10.8 min). Basal blood C and fT were collected at baseline: -48, -24 h, and immediately before (0 h) the EES as well as immediately (+0 h), +24 h, +48 h, and +72 h after the EES. Blood glucose (G) was measured to confirm no undue influence on C. Statistically data were analyzed with repeated measures ANOVA (LSD post hoc).

RESULTS

C (nmol/L) increased significantly from -48 h (321 ± 59) to +0 h (701 ± 178) (p < 0.001), and displayed a baseline overshoot with +24 h (209 ± 67) being significantly lower than -48 and +0 h (p < 0.03). fT (pmol/L) decreased significantly from -48 h (161 ± 40) to +0 h (106 ± 38) (p < 0.01) and remained lower at +24 h (110 ± 33) and +48 h (129 ± 30) (p < 0.001). G remained stable throughout. A moderately negative correlation (r = -0.636, p < 0.026) was found between C and fT at +0 h.

CONCLUSIONS

EES recovery may require 48 h for C and 72 h for fT to return to baseline values. Furthermore, C and fT were only correlated immediately post-exercise. Future research should perform more frequent measurements throughout time course.

Gut Microbiota Modification: Another Piece in the Puzzle of the Benefits of Physical Exercise in Health?

Regular physical exercise provides many health benefits, protecting against the development of chronic diseases, and improving quality of life. Some of the mechanisms by which exercise provides these effects are the promotion of an anti-inflammatory state, reinforcement of the neuromuscular function, and activation of the hypothalamic-pituitary-adrenal (HPA) axis. Recently, it has been proposed that physical exercise is able to modify gut microbiota, and thus this could be another factor by which exercise promotes well-being, since gut microbiota appears to be closely related to health and disease. The purpose of this paper is to review the recent findings on gut microbiota modification by exercise, proposing several mechanisms by which physical exercise might cause changes in gut microbiota.

The stress-buffering effect of acute exercise: Evidence for HPA axis negative feedback

According to the cross-stressor adaptation hypothesis, physically trained individuals show lower physiological and psychological responses to stressors other than exercise, e.g. psychosocial stress. Reduced stress reactivity may constitute a mechanism of action for the beneficial effects of exercise in maintaining mental health. With regard to neural and psychoneuroendocrine stress responses, the acute stress-buffering effects of exercise have not been investigated yet. A sample of highly trained (HT) and sedentary (SED) young men was randomized to either exercise on a treadmill at moderate intensity (60-70% VO2max; AER) for 30 min, or to perform 30 min of "placebo" exercise (PLAC). 90 min later, an fMRI experiment was conducted using an adapted version of the Montreal Imaging Stress Task (MIST). The subjective and psychoneuroendocrine (cortisol and α-amylase) changes induced by the exercise intervention and the MIST were assessed, as well as neural activations during the MIST. Finally, associations between the different stress responses were analysed. Participants of the AER group showed a significantly reduced cortisol response to the MIST, which was inversely related to the previous exercise-induced α-amylase and cortisol fluctuations. With regard to the sustained BOLD signal, we found higher bilateral hippocampus (Hipp) activity and lower prefrontal cortex (PFC) activity in the AER group. Participants with a higher aerobic fitness showed lower cortisol responses to the MIST. As the Hipp and PFC are brain structures prominently involved in the regulation of the hypothalamus-pituitary-adrenal (HPA) axis, these findings indicate that the acute stress-buffering effect of exercise relies on negative feedback mechanisms. Positive affective changes after exercise appear as important moderators largely accounting for the effects related to physical fitness.

Oral contraception but not menstrual cycle phase is associated with increased free cortisol levels and low hypothalamo-pituitary-adrenal axis reactivity

BACKGROUND

In females, estrogen is a potential modulator of cortisol response to stressors. The aim of this study was to determine the influence of menstrual cycle phase, oral contraception (OC) use and exercise training on hypothalamo-pituitary-adrenal (HPA) axis activity and reactivity after physical stress.

AIM

We investigated the effects of the menstrual cycle and OC use on exhaustive exerciseinduced changes in free salivary cortisol concentrations and free urinary cortisol/cortisone excretion in healthy young women.

MATERIALS AND SUBJECTS

Twenty-eight women were allocated to an untrained group (no.=16) or a trained group (no.=12), depending on their physical training background. The untrained group was composed of nine OC users (UNTOC+) and seven eumenorrheic women (UNT-OC-) tested in the follicular and luteal phases, while the trained group was entirely composed of OC+ subjects (T-OC+).

METHODS

Three laboratory sessions were conducted in a randomised order: a prolonged exercise test, a short-term exercise test, and a control session. For each session, urine and saliva specimens were collected at rest (09:00 h) and then, 30, 60 and 90 min later.

RESULTS

Estradiol fluctuation during the menstrual cycle phase did not alter free cortisol baseline values and responses to exercise. OC use was associated with increased free resting salivary concentrations and urinary cortisol excretion with blunted salivary cortisol response to prolonged exercise stimulation. No training effect was noted.

CONCLUSIONS

OC but not menstrual cycle phase is associated with increased free cortisol levels and low HPA axis reactivity.

The interface of hypothalamic-pituitary-adrenocortical axis and circulating brain natriuretic peptide in prediction of cardiopulmonary performance during physical stress

Brain natriuretic peptide (NT-pro-BNP) was implicated in the regulation of hypothalamic-pituitary-adrenocortical (HPA) responses to psychological stressors. However, HPA axis activation in different physical stress models and its interface with NT-pro-BNP in the prediction of cardiopulmonary performance is unclear. Cardiopulmonary test on a treadmill was used to assess cardiopulmonary parameters in 16 elite male wrestlers (W), 21 water polo player (WP) and 20 sedentary age-matched subjects (C). Plasma levels of NT-pro-BNP, cortisol and adrenocorticotropic hormone (ACTH) were measured using immunoassay sandwich technique, radioimmunoassay and radioimmunometric techniques, respectively, 10min before test (1), at beginning (2), at maximal effort (3), at 3rdmin of recovery (4). In all groups, NT-pro-BNP decreased between 1 and 2; increased from 2 to 3; and remained unchanged until 4. ACTH increased from 1 to 4, whereas cortisol increased from 1 to 3 and stayed elevated at 4. In all groups together, ΔNT-pro-BNP2/1 predicted peak oxygen consumption (B=37.40, r=0.38, p=0.007); cortisol at 3 predicted heart rate increase between 2 and 3 (r=-0.38,B=-0.06, p=0.005); cortisol at 2 predicted peak carbon-dioxide output (B=2.27, r=0.35, p<0.001); ΔACTH3/2 predicted peak ventilatory equivalent for carbon-dioxide (B=0.03, r=0.33, p=0.003). The relation of cortisol at 1 with NT-pro-BNP at 1 and 3 was demonstrated using logistic function in all the participants together (for 1/cortisol at 1 B=63.40, 58.52; r=0.41, 0.34; p=0.003, 0.013, respectively). ΔNT-pro-BNP2/1 linearly correlated with ΔACTH4/3 in WP and W (r=-0.45, -0.48; p=0.04, 0.04, respectively). These results demonstrate for the first time that HPA axis and NT-pro-BNP interface in physical stress probably contribute to integrative regulation of cardiopulmonary performance.

Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine

Successful training not only must involve overload but also must avoid the combination of excessive overload plus inadequate recovery. Athletes can experience short-term performance decrement without severe psychological or lasting other negative symptoms. This functional overreaching will eventually lead to an improvement in performance after recovery. When athletes do not sufficiently respect the balance between training and recovery, nonfunctional overreaching (NFOR) can occur. The distinction between NFOR and overtraining syndrome (OTS) is very difficult and will depend on the clinical outcome and exclusion diagnosis. The athlete will often show the same clinical, hormonal, and other signs and symptoms. A keyword in the recognition of OTS might be "prolonged maladaptation" not only of the athlete but also of several biological, neurochemical, and hormonal regulation mechanisms. It is generally thought that symptoms of OTS, such as fatigue, performance decline, and mood disturbances, are more severe than those of NFOR. However, there is no scientific evidence to either confirm or refute this suggestion. One approach to understanding the etiology of OTS involves the exclusion of organic diseases or infections and factors such as dietary caloric restriction (negative energy balance) and insufficient carbohydrate and/or protein intake, iron deficiency, magnesium deficiency, allergies, and others together with identification of initiating events or triggers. In this article, we provide the recent status of possible markers for the detection of OTS. Currently, several markers (hormones, performance tests, psychological tests, and biochemical and immune markers) are used, but none of them meet all the criteria to make their use generally accepted.

Experimental and clinical findings from physical exercise as complementary therapy for epilepsy

Complementary therapies for preventing or treating epilepsy have been extensively used. This review focuses on the positive effects of physical exercise programs observed in clinical studies and experimental models of epilepsy and their significance as a complementary therapy for epilepsy. Information about the antiepileptogenic and neuroprotective effects of exercise is highlighted. Considering that exercise can exert beneficial actions such as reduction of seizure susceptibility, reduction of anxiety and depression, and consequently, improvement of quality of life of individuals with epilepsy, exercise can be a potential candidate as non-pharmacological treatment of epilepsy.

Increase in IL-6, TNF-α, and MMP-9, but not sICAM-1, concentrations depends on exercise duration

It has been suggested that exercise intensity is of importance in the regulation of increase in pro-inflammatory molecules, but there is still a debate about the effect of duration on these molecules. Therefore, the effect of exercise duration on the serum concentrations of interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), soluble form of intercellular adhesion molecule-1 (sICAM-1), and matrix metalloproteinase-9 (MMP-9) was studied in 22 half-marathon (HM) and 18 marathon (M) male amateur runners who completed their exercise task in 1.8 ± 0.2 (mean ± standard deviation) and 3.6 ± 0.4 h, respectively (thus, average speed was 11.7 ± 1.5 and 11.9 ± 1.8 km h(-1), respectively). Blood was sampled 2 days before, 15 min after, and 28 h after the race. IL-6, TNF-α, and MMP-9 always increased immediately after exercise, but the increase was larger (P < 0.05) in M versus HM (∆IL-6: 31 ± 24 vs. 5 ± 4 pg ml(-1); ∆TNF-α: 1.7 ± 1.9 vs. 0.5 ± 0.8 pg ml(-1); MMP-9: 288 ± 216 vs. 145 ± 128 ng ml(-1), respectively). sICAM-1 also increased with exercise, but similarly in M and HM (20 ± 40 vs. 23 ± 32 ng ml(-1), respectively). Only sICAM-1 remained elevated 28 h post-exercise in both HM and M, while IL-6, TNF-α, and MMP-9 returned to pre-exercise levels. Competitive HM and M races induce significant increases in IL-6, TNF-α, sICAM-1, and MMP-9 concentrations. As HM and M runners performed the competition with similar absolute intensity, the difference in response between the groups suggests that exercise duration is of importance in the regulation of IL-6, TNF-α, and MMP-9, but not sICAM-1 concentrations in response to prolonged running.

Physically active men show better semen parameters and hormone values than sedentary men

Physical exercise promotes many health benefits. The present study was undertaken to assess possible semen and hormone differences among physically active (PA) subjects and sedentary subjects (SE). The analyzed qualitative sperm parameters were: volume, sperm count, motility, and morphology; where needed, additional testing was performed. The measured hormones were: follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), cortisol (C), and the ratio between T and C (T/C). Maximum oxygen consumption was also assessed to check for differences in fitness level. Statistically significant differences were found for several semen parameters such as total progressive motility (PA: 60.94 ± 5.03; SE: 56.07 ± 4.55) and morphology (PA: 15.54 ± 1.38, SE: 14.40 ± 1.15). The seminological values observed were supported by differences in hormones, with FSH, LH, and T being higher in PA than in SE (5.68 ± 2.51 vs. 3.14 ± 1.84; 5.95 ± 1.11 vs. 5.08 ± 0.98; 7.68 ± 0.77 vs. 6.49 ± 0.80, respectively). Likewise, the T/C ratio, index of anabolic versus catabolic status, was also higher in PA (0.46 ± 0.11 vs. 0.32 ± 0.07), which further supports the possibility of an improved hormonal environment. The present study shows that there are differences in semen and hormone values of physically active subjects and sedentary subjects. Physically active subjects seem to have a more anabolic hormonal environment and a healthier semen production.

Physical exercise in epilepsy: what kind of stressor is it?

Stress has been considered the most frequently self-reported precipitant of seizures in people with epilepsy. The literature documents that physical stress, that is, physical exercise, can have beneficial effects in people with epilepsy. In view of evidence indicating that sensitivity to stress is reduced after a physical exercise program, physical activity could be a potential candidate for stress reduction in people with epilepsy. This review considers how physical exercise could contribute to reduce seizure susceptibility and, hence, seizure frequency. Possible mechanisms by which exercise can be beneficial for people with epilepsy are highlighted. Hypothalamic-pituitary-adrenal axis adaptation, neurotransmitter system modulation, and metabolic and neuroendocrine changes may interfere with seizure susceptibility. The psychological stress of different sports activities is an important concern that must also be taken into account. Overall, among stress reduction therapies for the treatment of seizures, exercise might be a potential candidate.

Biological factors and the determination of androgens in female subjects

The idea of the presence of androgens in females may sound peculiar as androgens generally refer to male hormones. Although produced in small amounts in women, androgens have direct and significant effects on many aspects of female physiology. Moreover, androgens are precursors to estrogens, which are the predominant female sex hormones. The measurement of androgens in blood is important in the diagnosis of both gonadal and adrenal functional disturbances, as well as monitoring subsequent treatments. The accuracy of such measurements is crucial in sports medicine and doping control. Therefore, the concentration of androgens in female subjects is frequently measured. Analysing such compounds with accuracy is especially difficult, costly and time consuming. Therefore, laboratories widely use direct radioimmunoassay kits, which are often insensitive and inaccurate. It is especially complicated to determine the level of androgens in women, as the concentration is much lower compared to the concentration found in males. Additionally, the amount of androgens in fluids tends to decrease with aging. Analyses of hormone concentrations are influenced by a myriad of factors. The factors influencing the outcome of these tests can be divided into in vivo preanalytical factors (e.g., aging, chronobiological rhythms, diet, menstrual cycle, physical exercise, etc.), in vitro preanalytical factors (e.g., specimen collection, equipment, transport, storage, etc.) and as mentioned before, analytical factors. To improve the value of these tests, the strongly influencing factors must be controlled. This can be accomplished using standardised assays and specimen collection procedures. In general, sufficient attention is not given to the preanalytical (biological) factors, especially in the measurement of androgens in females. Biological factors (non-pathological factors) that may influence the outcome of these tests in female subjects have received little attention and are the topic of the present review.

Exercise and circulating cortisol levels: the intensity threshold effect

This study examined the influence of exercise intensity upon the cortisol response of the hypothalamic-pituitary-adrenal (HPA) axis. Specifically, we examined exercise at intensities of 40, 60, and 80% maximal oxygen uptake (VO2max) in an attempt to determine the intensity necessary to provoke an increase in circulating cortisol. Twelve active moderately trained men performed 30 min of exercise at intensities of 40, 60, and 80% of their VO2max, as well as a 30-min resting-control session involving no exercise on separate days. Confounding factors such as time of day--circadian rhythms, prior diet--activity patterns, psychological stress, and levels of exercise training were controlled. Cortisol and ACTH were assessed in blood collected immediately before (pre-) and after (post-) each experimental session. Statistical analysis involved repeated measures analysis of variance and Tukey post-hoc testing. The percent change in cortisol from pre- to post-sampling at each session was: resting-control, 40, 60, and 80% sessions (mean+/-SD) =-6.6+/-3.5%, +5.7+/-11.0%, +39.9+/-11.8%, and +83.1+/-18.5%, respectively. The 60% and 80% intensity magnitude of change was significantly greater than in the other sessions, as well as from one to another. The ACTH responses mirrored those of cortisol, but only the 80% exercise provoked a significant (p<0.05) increase pre- to post-exercise. The calculated changes in plasma volume for the resting-control, 40%, 60%, and 80% sessions were: +2.2+/-3.0%, -9.9+/-5.0%, -15.6+/-3.5%, and -17.2+/-3.3%, respectively. Collectively, the cortisol findings support the view that moderate to high intensity exercise provokes increases in circulating cortisol levels. These increases seem due to a combination of hemoconcentration and HPA axis stimulus (ACTH). In contrast, low intensity exercise (40%) does not result in significant increases in cortisol levels, but, once corrections for plasma volume reduction occurred and circadian factors were examined, low intensity exercise actually resulted in a reduction in circulating cortisol levels.

Cortisol and GH: odd and controversial ideas

Activation of the hypothalamo-pituitary-adrenal (HPA) axis and of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis represents a physiological response to the energetic, metabolic, vascular, and sometimes neurophysiologic or psychological needs of exercise. Long-lasting increased and (or) decreased secretion of cortisol (the end-product of the HPA axis) or of GH is detrimental to health. This suggests that the activity of these hormonal axes is finely tuned toward homeostasia, tolerating limited prolonged homeostatic disruption. However, the relationships between exercise training and cortisol and GH secretion are full of odd and controversial ideas. In this review, the relationships between HPA axis adaptation to exercise training or disadaptation with overtraining will be discussed, with an emphasis on the limitation on the current measures used to profile hormonal activity. Knowledge of these relationships between cortisol and GH responses to exercise is an important tool to fight against doping with glucocorticoids and GH, and their health-damaging consequences.

Trained men show lower cortisol, heart rate and psychological responses to psychosocial stress compared with untrained men

Physical activity has proven benefits for physical and psychological well-being and is associated with reduced responsiveness to physical stress. However, it is not clear to what extent physical activity also modulates the responsiveness to psychosocial stress. The purpose of this study was to evaluate whether the reduced responsiveness to physical stressors that has been observed in trained men can be generalized to the modulation of physiological and psychological responses to a psychosocial stressor. Twenty-two trained men (elite sportsmen) and 22 healthy untrained men were exposed to a standardized psychosocial laboratory stressor (Trier Social Stress Test). Adrenocortical (salivary free cortisol levels), autonomic (heart rate), and psychological responses (mood, calmness, anxiety) were repeatedly measured before and after stress exposure. In response to the stressor, cortisol levels and heart rate were significantly increased in both groups, without any baseline differences between groups. However, trained men exhibited significantly lower cortisol and heart rate responses to the stressor compared with untrained men. In addition, trained men showed significantly higher calmness and better mood, and a trend toward lower state anxiety during the stress protocol. On the whole, elite sportsmen showed reduced reactivity to the psychosocial stressor, characterized by lower adrenocortical, autonomic, and psychological stress responses. These results suggest that physical activity may provide a protective effect against stress-related disorders.

Corticotroph axis sensitivity after exercise: comparison between elite athletes and sedentary subjects

Strenuous exercise activates the hypothalamic-pituitary-adrenal (HPA) axis. Several reports showed that physical training is associated with a decreased efficiency of the feedback control of HPA axis. The aims of the present study were: 1) to evaluate the differences in the mechanical, hormonal, and lactate responses to a high-intensity isokinetic exercise among different groups of competitive athletes (CA, no.=20) of power and endurance disciplines and sedentary controls (SED, no.=10); 2) to determine the effects of the training status on the HPA axis responsiveness following exercise, as indirectly evaluated by the rates of ACTH, cortisol, and DHEA recovery after exercise. CA and SED fulfilled eight sets of twenty concentric contractions of the knee extensors at 180 degrees/sec angular velocity throughout a constant range of motion (100 degrees). There was a rest period of 30 sec between each set and a 3-min rest period between the two legs. Before, immediately after the isokinetic exercise and at different times in the subsequent 120 min of recovery, blood and saliva were sampled to determine plasma ACTH, salivary cortisol, serum DHEA, and serum lactate concentrations. CA showed a higher cortisol response to exercise than SED, whereas no differences were found in the responses of ACTH, DHEA and lactate. In the athlete group the exercise-induced increases of ACTH, cortisol, and lactate were higher in power athletes with respect to endurance athletes. No differences were observed between athletes and SED in the rates of hormonal recovery after exercise: this finding does not support the concept that a reduced feedback control of HPA axis can represent a feature of trained individuals.

Can non-invasive glucocorticoid measures be used as reliable indicators of stress in animals?

Refinement techniques are being increasingly employed in all fields of animal research to try to ensure that the highest standards of welfare are upheld. This review concerns one of the main emerging techniques for the assessment of welfare itself, namely the non-invasive measurement of glucocorticoids (GCs) as indicators of stress. The paper is divided into three sections. The first discusses the relationship between GCs and stress. The second section considers whether factors other than stress are linked to rises in GCs, eg exercise, oestrus cycle and diet. The final part examines the reliability of the non-invasive techniques that measure GCs from samples of saliva and faeces. Although it is important to take into account some caveats associated with the methodologies employed, it is concluded, nevertheless, that these techniques can give accurate and reliable information regarding the welfare status of an individual or group of animals without the procedures themselves causing any kind of distress to the subjects.

Interactions of metabolic hormones, adipose tissue and exercise

Physiological and psychological systems work together to determine energy intake and output, and thus maintain adipose tissue. In addition, adipose tissue secretes leptin and cytokines, which induces satiety and has been linked to catecholamines, cortisol, insulin, human growth hormone, thyroid hormones, gonadotropin and lipolysis. Thus, adipose tissue is acted upon by a number of physiological stimuli, including hormones, and simultaneously, is an active component in the regulation of its own lipid content. All of the hormones mentioned above are associated with each other and respond to exercise and exercise training. Thus, exercise is one of the major links between the hormonal modulators of energy intake and output. It appears that the sympathetic nervous system and the catecholamines are key components facilitating the lipolytic activity during exercise. These two neuroendocrine factors directly affect adipose metabolism and metabolic hormones that influence adipose metabolism. Acute low- and moderate-intensity exercise causes hormonal changes that facilitate lipolytic activity. Exercise training reduces these hormonal responses, but the sensitivity to these hormones increases so that lipolysis may be facilitated. Large amounts of adipose tissue blunt the metabolic hormonal responses to exercise, but the sensitivity of these hormones is increased; thus maintaining normal lipolytic activity. Although the physiological role of the endocrine system during exercise and training is significant, other training effects may have as great, or greater influence on lipolytic activity in adipose tissue.

Hormonal and Metabolic Adaptation in Professional Cyclists During Training

The aim of this study was to examine hormonal and metabolic changes in a group of 18 professional male cyclists ([Formula: see text]69.9 [95% CI 64.9 to 74.9] m L kg−1ùmin−1) during two successive periods of adapted intensive training. The second training period included 4 days of cycling competition. Intensity was increased while volume was decreased in the second training. Anthropometric data were collected before and at the end of the two training periods. Venous blood samples were taken in a basal state before the two training sessions and after each training session. Serum concentrations of cortisol (C), testosterone (T), dehydroepiandrosterone sulfate (DHEAs), and catecholamines were determined as well as branched-chain amino acids (valine, leucine, isoleucine) (BCAA) and free fatty acids (FFAs). At the end of the two training periods, the subjects lost fat mass whereas mean body mass was unchanged. The T/C ratio was reduced transiently after the first training session (45.90%), while DHEAs/C remained unchanged. T/C and DHEAs/C were significantly increased after the second training session compared to the first (48.40 and 97.18%, respectively). Catecholamines and FFAs were unchanged. The significant increase in BCAA levels after the second training session was of note as it might constitute a "store shape" of amino acids in anticipation of future intense training loads. Based on the responses of testosterone, DHEAs, and cortisol, and on the training-induced increase in BCAA, there appeared to be hormonal and metabolic adaptation despite the inherent psychological stress of competition. Key words: cycling training, cortisol, testosterone, DHEAs, amino acids

The overtraining syndrome in athletes: a stress-related disorder

Physical exercise is a type of allostatic load for several endocrine systems, notably the hypothalamic-pituitary-adrenal (HPA) axis. Athletes undergoing a strenuous training schedule can develop a significant decrease in performance associated with systemic symptoms or signs: the overtraining syndrome (OTS). This is a stress-related condition that consists of alteration of physiological functions and adaptation to performance, impairment of psychological processing, immunological dysfunction and biochemical abnormalities. Universally agreed diagnostic criteria for OTS are lacking. The pituitary-adrenal response to a standardized exercise test is usually reduced in overtrained athletes. This HPA dysfunction could reflect the exhaustion stage of Selye's general adaptation syndrome. The most attractive hypothesis that accounts for the observed neuro-endocrine-immune dysregulation is the Smith's cytokine hypothesis of OTS. It assumes that physical training can produce muscle and skeletal trauma, thus generating a local inflammatory reaction. With the excessive repetition of the training stimulus the local inflammation can generate a systemic inflammatory response. The main actors of these processes are the cytokines, polypeptides that modulate HPA function in and outside the brain at nearly every level of activity. It is hoped that future research will focus on endogenous risk factors for morbidities related to the neuro-endocrine-immune adaptation to exercise.

Associations between neuroendocrine responses to the Insulin Tolerance Test and patient characteristics in chronic fatigue syndrome

OBJECTIVE

Subtle dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis have been proposed as an underlying pathophysiological mechanism in chronic fatigue syndrome (CFS). This study attempted to assess the relationship between patient characteristics and HPA axis functioning using a neuroendocrine challenge test.

METHOD

A test battery designed to assess different dimensions of CFS was given to 18 CFS patients and 17 controls. To evaluate the integrity of the HPA axis, the Insulin Tolerance Test (ITT), a centrally acting neuroendocrine challenge test, was performed on patients and controls. ACTH, salivary free cortisol and total plasma cortisol levels were assessed as a measure of the HPA axis stress response. Correlations of patient characteristics were calculated with integrated responses for all endocrine parameters.

RESULTS

CFS patients had a significantly reduced area under the ACTH response curve (AUC) in the ITT. The AUC was significantly associated with the duration of CFS symptoms (r = -.592, P = .005) and the severity of fatigue symptomatology (r = -.41, P = .045). In addition, duration of CFS was correlated with the severity of fatigue symptoms (r = .38, P = .045). Similar associations were not observed for cortisol parameters.

CONCLUSION

It has been postulated that neuroendocrine dysregulations observed in CFS are of an acquired nature. The results of a strong association between the integrated ACTH response and the duration of CFS emphasizes the need to consider factors known to be risk factors for the chronicity of CFS symptoms, such as profound inactivity, deconditioning and sleep abnormalities, as possible candidates for secondary causes of neuroendocrine dysregulations in CFS.

The 24-h Urinary Cortisol/Cortisone Ratio for Monitoring Training in Elite Swimmers

PURPOSE

The effect of training variations on 24-h urinary cortisol/cortisone (C/Cn) ratio was investigated in highly trained swimmers to determine whether it could be a good marker of training stress and performance.

METHODS

Fourteen swimmers (five female and nine male) were tested after 4 wk of intense training (IT), 3 wk of reduced training (RT), and 5 wk of moderate training (MT). At the end of each period, the swimmers performed in their best event at an official competition. Individual performances were expressed as a percentage of the previous season's best performance. The fatigue state was evaluated with a questionnaire.

RESULTS

The C/Cn ratio was statistically different for the three periods (IT: 1.10 +/- 0.7, RT: 0.64 +/- 0.3, and MT: 0.57 +/- 0.2). The differences in the C/Cn ratio between two consecutive performances were related to the differences in performance (r = -0.52, P < 0.01), and the C/Cn ratio was significantly related to the total training (r = 0.32, P < 0.05) and total score of fatigue (TSF) (r = 0.35, P < 0.03) over the follow-up period. Cn levels were related to the dryland training (r = -0.46; P < 0.01) and TSF (r = -0.40; P < 0.02). During IT, variations in the C/Cn ratio were related to the changes in the mean intensity (r = -0.67; P < 0.02) and to TSF (r = 0.69; P < 0.01).

CONCLUSION

The 24-h C/Cn ratio was moderately related to both training and performance whereas Cn levels were only related to training. The C/Cn ratio could be a useful indicator for monitoring the overreaching state in elite swimmers.

Acute and chronic effects of exercise on tissue sensitivity to glucocorticoids

The aim of this study was to address the effect of endurance training on tissue sensitivity to glucocorticoids (GC) in both resting and exercising conditions. In vitro dexamethasone inhibition of LPS-induced interleukin-6 secretion in cultures of peripheral monocytes was compared in untrained subjects (UT) and in endurance-trained men (ET) at the end of a 2-h run and during exercise recovery. We demonstrated an in vitro plasticity of sensitivity of monocytes to GC in ET men, superimposed to changes in systemic cortisol concentrations (plasma and saliva). Compared with sedentary men, similar resting cortisol levels in ET men are associated with decreased sensitivity of monocytes to GC 8 and 24 h after the end of the last training session (P < 0.05, ET vs. UT). Moreover, in these ET subjects, an acute bout of exercise increased the sensitivity of monocytes to GC (at 1000 and 1200; ET vs. UT, P > 0.05). This acute exercise-induced increase in tissue sensitivity to GC, which is synchronous with activation of the hypothalamo-pituitary adrenal axis, may act to shut off muscle inflammatory reaction and cytokine synthesis and then decrease exercise-induced muscle damage or inflammatory response. By contrast, the decreased sensitivity of monocytes to GC reported in ET men 24 h after the last bout of exercise may be related to the process of desensitization that may act to protect the body from prolonged, exercise-induced cortisol secretion. These acute and chronic effects of exercise on tissue sensitivity to GC demonstrate an adaptation of the hypothalamo-pituitary adrenal axis to repeated and prolonged exercise-induced increases in GC secretion.

Decrease in serum leptin after prolonged physical activity in men

PURPOSE

This study was designed to determine whether serum leptin levels were affected by a 5-d military course after 3 wk of combat training.

METHODS

26 male soldiers (mean age = 21 +/- 2 yr) were examined at the beginning of the training program and just at the end of the 5-d course. The combination of continuous heavy physical activity and sleep deprivation led to energy deficiency. Blood samples were analyzed for serum leptin, insulin, cortisol, adrenocorticotropin (ACTH), and testosterone; plasma was analyzed for free fatty acids (FFA), glycerol, glucose, and catecholamines.

RESULTS

At the end of the 5-d course, there was a significant reduction in serum leptin (0.40 +/- 0.04 ng x mL(-1) versus 1.47 +/- 0.14 ng x mL(-1), < 0.001), i.e., a mean decrease of 67.00 +/- 3.75%. Plasma norepinephrine and dopamine rose significantly from 296 +/- 17 ng x L(-1) to 672 +/- 48 ng x L(-1) and 23 +/- 3 ng x L(-1) to 40 +/- 5 ng x L(-1) ( < 0.001 and < 0.01, respectively), whereas epinephrine remained unchanged. Serum concentrations of the anabolic hormone, insulin, fell from 31.17 +/- 3.03 microU x mL(-1) to 17.79 +/- 1.58 microU x mL(-1) ( < 0.001), whereas plasma FFA and glycerol were increased ( < 0.001, < 0.05, respectively). A statistically significant correlation appeared between the changes in leptin and insulin (r = 0.5306, < 0.01). Serum testosterone decreased significantly ( < 0.001), whereas serum cortisol, ACTH, and plasma glucose were unchanged at the end of the course. The training program had no significant effect on mean body mass index.

CONCLUSION

A 4-wk strenuous military training program, which induced an energy deficiency, reduced serum leptin to a third of normal levels. The decrease in serum leptin was attributed to the exercise-induced elevation in catecholamines and hypoinsulinemia.

Effects of moderate and intensive training on the hypothalamo-pituitary-adrenal axis in rats

The influence of the two distinct training programmes, moderate (M) and intensive (I), on hypothalamo-pituitary-adrenal (HPA) axis was investigated, in rats. Changes in plasma concentrations of adrenocorticotropin hormone (ACTH) and corticosterone were followed in response to (i) a 60-min acute running session performed on 2nd, 4th and 6th of the seven training weeks (ii) an acute restraint stress of 40 min applied after the final training programme. After 2nd, 4th and 6th week of the two training programmes, a 60-min running resulted in an enhanced secretion of ACTH and corticosterone, compared with both the baseline values (i.e. before running) and to the sedentary (S) group. However, on 4th and 6th weeks compared with 2nd week, ACTH and corticosterone remained elevated in intensive group when they are significantly reduced in moderate group. We could suggest that a moderate training resulted in an adapted hormonal response whereas a deadapted process occurred for the intensive programme. The day after the last training session, basal ACTH, corticosterone and corticosteroid-binding globulin (CBG) capacity were not affected by training. Hypothalamic corticotropin-releasing factor tissue-content (CRF) was increased significantly in the two trained groups. When compared with the sedentary group, the body weight of the rats in the two trained groups was significantly decreased with a total adrenal mass increasing but only in intensive group. The surimposed restraint stress resulted in significant increases in plasma ACTH and corticosterone both in trained and in sedentary animals. This result suggests that the adapted HPA axis response induced by both a moderate and intensive training do not prevent against the effects of a novel stress such as restraint stress.