The effect of obesity on inflammatory cytokine and leptin production following acute mental stress.

Obesity may contribute to cardiovascular disease (CVD) risk by eliciting chronic systemic inflammation and impairing the immune response to additional stressors. There has been little assessment of the effect of obesity on psychological stress, an independent risk factor for CVD. Therefore, it was of interest to examine interleukin-6, tumor necrosis factor-α, interleukin-1ß (IL-1ß), interleukin-1 receptor antagonist (IL-1Ra), and leptin following an acute mental stress task in nonobese and obese males. Twenty college-aged males (21.3 ± 0.56 years) volunteered to participate in a 20-min Stroop color-word and mirror-tracing task. Subjects were recruited for obese (body mass index: BMI > 30) and nonobese (BMI < 25) groups, and blood samples were collected for enzyme-linked immunosorbent assay analysis. The acute mental stress task elicited an increase in heart rate, catecholamines, and IL-1ß in all subjects. Additionally, acute mental stress increased cortisol concentrations in the nonobese group. There was a significant reduction in leptin in obese subjects 30 min posttask compared with a decrease in nonobese subjects 120 min posttask. Interestingly, the relationship between the percent change in leptin and IL-1Ra at 120 min posttask in response to an acute mental stress task was only observed in nonobese individuals. This is the first study to suggest that adiposity in males may impact leptin and inflammatory signaling mechanisms following acute mental stress.

Forearm blood flow response to acute exercise in obese and non-obese males.

Chronic exercise is thought to improve endothelium-dependent vasodilation; however, few studies have evaluated the effects of acute exercise on microvascular vasodilatory capacity (MVC). Moreover, no studies have compared MVC responses in obese and non-obese individuals following acute exercise. To evaluate MVC, utilizing forearm blood flow (FBF) and excess blood flow (EBF) before and up to 48 h after a single exercise bout to elicit peak oxygen consumption (VO2 peak) in obese and non-obese males. Twelve obese (37.0 ± 1.1 kg/m(2)) and 12 non-obese (21.9 ± 0.3 kg/m(2)) males volunteered to participate. FBF measures, before and during reactive hyperemia (RH), were obtained prior to (PRE-E), immediately after (POST-E), and at 1 (POST-1), 2 (POST-2), 24 (POST-24), and 48 (POST-48) hours after exercise. EBF, was calculated as the difference between FBF, before and during RH. Blood samples were obtained to evaluate the response of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α), which are potential modifiers of MVC. FBF before and during RH were significantly (P < 0.05) increased in both groups POST-E. The EBF magnitude of change from PRE-E was significantly (P < 0.05) elevated in non-obese when compared with obese males. Although not related to MVC, concentrations of IL-6 significantly decreased between POST-2 and POST-24 in both groups. An acute bout of exercise designed to elicit VO2 peak significantly increased forearm MVC in non-obese and obese males, although the magnitude of change in EBF from PRE-E to POST-E was greater in non-obese males.

Modelling the anxiety-depression continuum in chicks.

The clinical syndromes of anxiety and depression are now thought to exist along a temporal continuum and this construct has been modelled in a preclinical setting in chicks separated from conspecifics. This research sought to further the validity of the chick anxiety-depression continuum model. Dose-response studies using two classes of anxiolytics (chlordiazepoxide: 2.5, 5.0, 10.0, 15.0 mg/kg, and clonidine: 0.1, 0.15, 0.2, 0.25 mg/kg) and three classes of antidepressants (imipramine: 1.0, 3.0, 10.0, 15.0 mg/kg, maprotoline: 2.5, 5.0, 10.0, 20.0 mg/kg and fluoxetine: 1.0, 5.0, 10.0, 20.0 mg/kg) showed an ability to detect anxiolytic activity of chlordiazepoxide, clonidine, imipramine and maprotoline in the anxiety-like phase of the model and to detect antidepressant effects of imipramine, maprotoline and fluoxetine in the depression-like phase of the model. In addition, blood plasma interleukin-6, a biomarker of stress, was found to be elevated in response to social-separation stress. Collectively, these findings further characterize the model as a simulation of the anxiety-depression continuum and begin to establish the paradigm as a high-utility adjuvant to rodent screening assays for putative anxiolytic and antidepressant compounds.

Cardiorespiratory responses of Hi Fit and Low Fit subjects to mental challenge during exercise.

The influence of psychological states on physiological responses during exercise is of considerable importance to individuals for which the efficiency of energy production is critical to occupational performance. Numerous studies have shown that aerobic fitness is associated with enhanced cardiovascular efficiency at rest and that responses to mental stress demonstrate evidence of increased sensitivity (relative increase in HR response) and enhanced efficiency (a decrease in absolute HR). However, the effect of aerobic fitness and its impact on cardiorespiratory (CR) responses to psychological stress during exercise has not been investigated. Therefore, the purpose of this study was three-fold; (1) to examine during exercise, anxiety, effort sense, and CR responses to a mental challenge, (2) to examine anxiety and heart rate (HR) responses from rest to exercise with mental challenge between below average fitness (Low Fit) and well-above average fitness (Hi Fit) individuals (exercising at similar relative intensities), and (3) to examine anxiety, effort sense, and CR responses of Low Fit and Hi Fit individuals to a mental challenge during exercise at a similar relative intensity. Twelve Low Fit and eleven Hi Fit subjects participated in two, 32-minute cycle ergometer rides at 65 % of VO2max. In the mental challenge condition (MCC), subjects rode while participating in mentally challenging tasks (Stroop Color-Word task and mental arithmetic) from min 6 to min 14 of the protocol. In the no mental challenge condition (NMCC), subjects exercised at the same intensity and duration without a stressor. Subjects were counter-balanced between fitness levels and condition. HR, VE, VE/VO2, RR, VO2, RER, effort sense (RPE), and state anxiety (SAI) were assessed at 5, 14, 24, and 30 min. SAI was also assessed at - 5 min before exercise and after 15 min of recovery. In addition, the NASA task load index (NTLX) was used to assess perceived overall workload. SAI increased significantly at 14 min in the MCC. NTLX scores indicated that the MCC was perceived as a greater overall workload. Furthermore, HR, VE, VE/VO2, and RR were significantly elevated during the mental challenge condition at 14 min. The Hi Fit subjects tended to respond to the dual stress of exercise and mental challenge with a relative increase in HR, while absolute HR was similar in both groups. An examination of fitness group differences revealed that SAI and NTLX were similar for Low Fit and Hi Fit subjects when exercising in the MCC, although, Hi Fit subjects demonstrated lower HR responses from 6 min to 14 min. VE, VE/VO2, and RR were similar for Low Fit and Hi Fit subjects. These results suggest that psychological stress during physical activity can exacerbate cardiorespiratory responses and suggests that factors that impact CR adjustment to mental challenge from resting baseline may differ from the factors that impact CR adjustment to mental challenge during exercise. Finally, fitness level attenuates HR and may attenuate additional cardiorespiratory responses while participating in a dual stress condition, of exercise and mental challenge.

Rigorous running increases growth hormone and insulin-like growth factor-I without altering ghrelin.

It has been suggested that ghrelin may play a role in growth hormone (GH) responses to exercise. The present study was designed to determine whether ghrelin, GH, insulin-like growth factor-I (IGF-I), and IGF-binding protein-3 (IGFBP-3) were altered by a progressively intense running protocol. Six well-trained male volunteers completed a progressively intense intermittent exercise trial on a treadmill that included four exercise intensities: 60%, 75%, 90%, and 100% of Vo2max. Blood samples were collected before exercise, after each exercise intensity, and at 15 and 30 mins following the exercise protocol. Subjects also completed a separate control trial at the same time of day that excluded exercise. GH changed significantly over time, and GH area under the curve (AUC) was significantly higher in the exercise trial than the control trial. Area under the curve IGF-I levels for the exercise trial were significantly higher than the control trial. There was no difference in the ghrelin and IGFBP-3 responses to the exercise and control trials. Pearson correlation coefficients revealed significant relationships between ghrelin and both IGF-I and IGFBP-3; however, no relationship between ghrelin and GH was found. In conclusion, intense running produces increases in total IGF-I concentrations, which differs from findings in previous studies using less rigorous running protocols and less frequent blood sampling regimens. Moreover, running exercise that produces substantial increases in GH does not affect peripheral ghrelin levels; however, significant relationships between ghrelin and both IGF-I and IGFBP-3 exist during intense intermittent running and recovery, which warrants further investigation.

Percentual responses proximal to the onset of blood lactate accumulation.

AIM: Running at incremental velocities proximal to the onset of blood lactate accumulation (OBLA) elicits linear increases in VO(2), and HR, while the increases in V(E) and blood lactic acid concentrations (BLa) are curvilinear. In addition, effort sense is often measured in the field with the traditional 15-point scale Ratings of Perceived Exertion scale, increases linearly whereas the perceptual response of affect seem to decrease in a nonlinear manner. This study examined the changes in effort sense (RPE) and affect, utilizing the Feeling Scale (FS), at 3 running intensities proximal to the onset of blood lactate accumulation. In addition, the relationship between these perceptual responses and V(E), VO(2), HR, RER, and BLa were examined. METHODS: Eleven highly-trained distance runners (VO(2max) = 67.65+/-1.24) participated in 2 sessions of data collection. During Session 1 subjects performed a discontinuous progressive treadmill protocol to determine peak aerobic power. After each stage a finger tip blood sample was taken to determine BLa. A regression line between the 2 successive workloads that produced BLa above and below 4 mM was calculated to predict the VO(2) that would generate 4mM BLa (VO(2) @ 4 mM). Within 1 week each subject returned for Session 2, which included a 10-min warm-up run followed by 3 submaximal runs lasting 5 min each: the VO(2) at 10% below OBLA (VO(2) 10% ), the VO(2) at OBLA (VO(2) @ 4 mM), and the VO(2) at 10% above OBLA (VO(2) 10%). During the last minute of each run VO(2), V(E), HR, RER, RPE, and FS were assessed. In addition, Bla was assessed immediately following each run. RESULTS: Results demonstrated that VO(2) 10%, VO(2) @ 4 mM, and VO(2) 10% - elicited BLa of 2.66+/-0.33, 3.75+/-0.40, and 6.10+/-0.68 mM, respectively. In addition, RPE increased significantly from VO(2) 10% to VO(2) @ 4 mM and from VO(2) @ 4 mM to VO(2) 10% -; whereas FS demonstrated a slight decrease from VO(2) 10% to VO(2) @ 4 mM, and a more substantial and significant decrease from VO(2) @ 4 mM to VO(2) 10% -. Correlational analyses revealed significant relationships at VO(2) 10% -. Specifically, RPE and FS were negatively related (r=0.62), while RPE and VO(2) were positively related (r=0.53). Correlations across all workloads revealed a tendency for more powerful relationships to exist among RPE and physiological cues than FS and physiological cues. CONCLUSION: This is the first study to directly examine changes in RPE and FS in relation to the physiological threshold for anaerobic metabolism, Bla, which responds to linear increases in exercise intensity in a curvilinear manner. Results support previous investigations suggesting a that the drop in FS has some distinction from the increase in RPE and that FS may be more sensitive to the onset of anaerobic metabolism. Moreover, the relationship of RPE to FS at VO(2) 10% -, but not VO(2) 10% and VO(2) @ 4 mM, supports the hypothesis that the unique variability of FS is diminished at higher intensities of exercise when physiological cues are unambiguous.

Kinematic changes at intensities proximal to onset of lactate accumulation.

AIM: The purpose of this study was to examine changes in selected kinematic variables at 3 running intensities proximal to the onset of blood lactate accumulation (OBLA; 4 mM of blood lactate). It was hypothesized that greater changes in lower body mechanics would occur when running faster than normal race pace compared to when running slower than race pace. METHODS: Nine competitive male distance runners ran at 3 running intensities (RI): 1) each runner's VO(2) at 10% below the VO(2) at OBLA, 2) VO(2) at OBLA, and 3) VO(2) at 10% above the VO(2) at OBLA. Selected kinematic and physiological variables were measured at each RI. RESULTS: VO(2) at RI 1, 2 and 3 was highly correlated with running speed (r=0.93). The blood lactate (BL) showed a nonlinear increase from RI 1 (2.9+/-0.8 mM) to 2 (4.1+/-0.9 mM) to 3 (6.7+/-1.8 mM). The vertical oscillation of center of gravity (VOCOG), stride frequency (SF), range of motion (ROM) of trunk angle, and maximal knee flexion during flight phase (MKFF) changed nonlinearly as did the BL. Significant relationships between BL and VOCOG (r=0.44) and between BL and SF (r=0.51) were found (ps<0.05). CONCLUSION: The findings show a possibility that lower body running mechanics have a relationship with BL.

Glucoregulatory endocrine responses to intermittent exercise of different intensities: plasma changes in a pancreatic beta-cell peptide, amylin.

Amylin, a peptide hormone released from the beta cells of the pancreas and cosecreted with insulin, is reported to inhibit the release of postprandial glucagon and insulin and to modulate gastric emptying. Changes in insulin and glucagon are important for controlling blood glucose levels under conditions in which metabolic rate is elevated, such as during and following exercise. Amylin may participate in the regulation of blood glucose levels in response to exercise, although the role of amylin has not been investigated. The purpose of the study was to determine the effects of a progressive, intermittent exercise protocol on amylin concentrations and to compare its response to circulating levels of insulin, glucagon, cortisol, and glucose. Seven well-trained males completed an intermittent exercise trial on a treadmill at four progressive exercise intensities: 60%, 75%, 90%, and 100% of maximum oxygen consumption (.VO(2)max). Blood samples were collected before exercise, after each exercise intensity, and for 1 hour following the exercise protocol. Subjects also completed a control trial with no exercise. Amylin and insulin rose from baseline (5.79 +/-.78 pmol/L and 4.76 +/-.88 microIU/mL) to peak after 100% .VO(2)max (9.16 +/- 1.35 pmol/L and 14.37 +/- microIU/ml), respectively and remained elevated during much of recovery. Thus, a progressive intermittent exercise protocol of moderate to maximum exercise intensities stimulates increases in amylin levels in well-trained individuals in a similar fashion to that of insulin, whereas glucagon concentrations only increase after the greatest exercise intensity, then quickly decline. Future studies should examine the effects of higher amylin concentrations in exercise recovery on glucoregulation.

Leptin and steroid hormone responses to exercise in adolescent female runners over a 7-week season.

The purpose of the study was to investigate the responses of leptin and steroid hormones to maximal exercise in adolescent female runners over a competitive season. Seven adolescent female distance runners completed three testing trials during weeks 1.4 and 7 of their high-school track season. Blood samples were collected before and after a discontinuous graded exercise test to exhaustion (GXT) for each trial. Tests were administered during the subjects' normal training time (3:30 p.m.-5:00 p.m.). Compared to week 1, peak O2 uptake rose significantly during the season and was 10% and 7% higher at weeks 4 and 7, respectively. Levels of dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), cortisol, testosterone, and leptin increased significantly in response to the graded exercise tests. Testosterone levels were also changed over the course of the study. Resting testosterone levels and testosterone responses to exercise in weeks 4 and 7 were both higher than in week 1. Resting concentrations and acute increases of the other hormones were not changed over the season. It appears, therefore, that DHEA, DHEAS, cortisol, testosterone and leptin concentrations increase in response to running in adolescent female runners. Data also suggest that training and/or maturation increases resting testosterone concentrations and testosterone responses to running in adolescent female runners during a training season.

An examination of stress and burnout in certified athletic trainers at division I-a universities.

OBJECTIVE: A growing body of knowledge indicates that too much stress can negatively influence psychological and physical health. A model proposed by Smith to explore personal and situational variables, stress appraisal, and burnout has led to significant understanding of burnout of individuals working in service professions. We examined the relationship of hardiness, social support, and work-related issues relevant to athletic trainers to perceived stress and the relationship of perceived stress to burnout. DESIGN AND SETTING: Correlational analyses were performed to examine the relationships predicted by Smith's model. In addition, we conducted stepwise multiple regression analyses to assess the relative contributions of the personal and situational variables to perceived stress and to examine the relative impact of perceived stress on 3 burnout factors (emotional exhaustion, personal accomplishment, and depersonalization). SUBJECTS: One hundred eighteen certified athletic trainers working in National Collegiate Athletic Association Division I-A intercollegiate settings that maintain a football program. MEASUREMENTS: We assessed personal and situational variables using the Hardiness Test, the Social Support Questionnaire, and the Athletic Training Issues Survey, adapted for this study. The Perceived Stress Scale was used to assess stress appraisal, and the Maslach Burnout Inventory was used to assess 3 dimensions of burnout. RESULTS: Our results were in support of Smith's theoretical model of stress and burnout. Athletic trainers who scored lower on hardiness and social support and higher on athletic training issues tended to have higher levels of perceived stress. Furthermore, higher perceived stress scores were related to higher emotional exhaustion and depersonalization and lower levels of personal accomplishment. CONCLUSIONS: Our findings examining burnout in Division I athletic trainers were similar to those of other studies investigating coaches and coach-teachers and in support of Smith's theoretical model of stress and burnout.

Effects of a proposed challenge on effort sense and cardiorespiratory responses during exercise.

PURPOSE: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency. METHODS: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min. RESULTS: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change. CONCLUSION: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.

Effects of aerobic exercise on serum leptin levels in obese women.

It has been demonstrated that leptin concentrations in obese patients may be altered by weight loss. We examined the effects of a 9-week aerobic exercise program on serum leptin concentrations in overweight women (20-50% above ideal body mass) under conditions of weight stability. Sixteen overweight women, mean (SE) age 42.75 (1.64) years, comprised the exercise group which adhered to a supervised aerobic exercise program. A graded exercise treadmill test was conducted before and after the exercise program to determine maximal oxygen uptake (VO2max) using open-circuit spirometry. The women demonstrated improved aerobic fitness (VO2max increased 12.29%), however, body fat and the body mass index did not change significantly [42.27 (1.35)-41.87 (1.33)%]. Fourteen women, age 40.57 (2.80) years, did not exercise over the same time period and served as a control group. Serum leptin levels were not significantly altered for either the exercise [28.00 (2.13)-31.04 (2.71) ng x ml(-1)] or the control group [33.24 (3.78)-34.69 (3.14) ng x mg(-1)]. The data indicate that 9 weeks of aerobic exercise improves aerobic fitness, but does not affect leptin concentrations in overweight women.

Applying physiological principles and assessment techniques to swimming the English Channel. A case study.

BACKGROUND: This study presents the use of physiological principles and assessment techniques in addressing four objectives that can enhance a swimmer's likelihood of successfully swimming the English Channel. The four objective were: (1) to prescribe training intensities and determine ideal swimming pace; (2) to determine the amount of insulation needed, relative to heat produced, to diminish the likelihood of the swimmer suffering from hypothermia; (3) to calculate the caloric expenditure for the swim and the necessary glucose replacement required to prevent glycogen depletion; and (4) to determine the rate of acclimatization to cold water (15.56 C/60 F). METHODS: The subject participated in several pool swimming data collection sessions including a tethered swim incremental protocol to determine peak oxygen consumption and onset of lactate accumulation and several steady state swims to determine ideal swimming pace at 4.0 mM/L of lactate. Additionally, these swims provided information on oxygen consumption, which in combination with ultrasound assessment of subcutaneous fat was used to assess heat production and insulation capabilities. Finally, the subject participated in 18 cold water immersions to document acclimatization rate. RESULTS: The data demonstrated the high fitness level of this subject and indicated that at a stroke rate of 63 stokes/min, HR was 130 heats/min and lactate was 4 mM/L. At this swimming pace the swimmer would need to consume 470 kcal of glucose/hr. In addition, the energy produced at this swim pace was 13.25 kcal/min while the energy lost at the present subcutaneous fat quantity was 13.40 kcal/min, requiring a fat weight gain of 6,363.03 g (13.88 lbs) to resist heat loss. CONCLUSIONS: Finally, the data from the cold water immersions suggested that acclimatization occurred following two weeks of immersions. There results were provided to the swimmer and utilized in making decisions in preparation for the swim.

Effects of low-volume resistive exercise on beta-endorphin and cortisol concentrations.

It has been recently suggested that high and sustained lactate levels may elicit increases in peripheral B-EN concentrations (16). We have observed elevated and sustained lactate concentrations in response to a low-volume resistive exercise protocol (14) that were similar to those from other exercise protocols that produced elevated beta-endorphin (B-EN) concentrations. Thus, the purpose of the study was to determine the effects of a low-volume (21,700 J) resistive exercise repetition maximum (RM) protocol using weight machines on peripheral lactate, B-EN and cortisol concentrations. Subjects completed 3 sets of bench press, lat-pull, leg extension, and leg curl exercise at a 10-RM load. Blood samples were collected and rating of perceived exertion (RPE, 15-point Borg scale) was assessed before exercise (-40 and -10 min), after each exercise, and after the exercise session (+ 35 min); blood samples were collected at 7 additional post-exercise times. RPE increased significantly throughout the exercise. Lactate concentrations rose significantly to peak at 8.54 mM at LE. B-EN and cortisol concentrations (-10) of 4.63 +/- 0.54 pmol.l-1 and 12.09 +/- 1.44 micrograms.dl-1, respectively, were not significantly elevated over time. The data suggest that a low-volume resistive exercise protocol using weight machines elevates lactate concentrations without altering B-EN and cortisol concentrations.

Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance.

The purpose of this study was to determine the effects of increased training intensity (ITI) on VO2max, plasma lactate accumulation, ventilatory threshold (VT), and performance in trained distance runners. Seven trained male distance runners increased their training intensity three d.wk-1 at 90-95% HRmax for eight wk. ITI did not alter VO2max (65.3 +/- 2.3 vs 65.8 +/- 2.4 ml.kg-1.min-1) but improved 10 km race time (means = 63 s decrease) and increased run time to exhaustion on the treadmill at the same speed and grade (means = 3.88 min). Significant decreases in plasma lactate concentration at 85 and 90% of VO2max were observed after ITI. No differences were found in plasma lactate at 65, 70, 75 or 80% of VO2max or VT following ITI. Significant correlations were obtained between 10 km race times and changes in plasma lactate at 85 and 90% of VO2max (r = 0.69 and 0.73, respectively). Lactate accumulation at both 2.5 and 4.0 mM were at a significantly greater percent of VO2max after ITI. Additionally, the changes in plasma lactate were dissociated from alterations in VT after ITI. These data indicate that previously trained runners can increase training intensity to improve endurance performance by lowering lactate at the intensity at which they trained despite no changes in VO2max and VT.