Exercise and brain neurotransmission

Leisure time physical activity in relation to depressive symptoms in the Black Women's Health Study

BACKGROUND

A growing body of evidence suggests that physical activity might reduce the risk of depressive symptoms, but there are limited data on Black women.

PURPOSE

The objective was to evaluate the association between leisure time physical activity and depressive symptoms in U.S. Black women.

METHODS

Participants included 35,224 women ages 21 to 69 from the Black Women's Health Study, a follow-up study of African American women in which data are collected biennially by mail questionnaire. Women answered questions on past and current exercise levels at baseline (1995) and follow-up (1997). The Center for Epidemiologic Studies Depression Scale (CES-D) was used to measure depressive symptoms in 1999. Women who reported a diagnosis of depression before 1999 were excluded. We used multivariate logistic regression models to compute odds ratios (ORs) and 95% confidence intervals (CIs) for physical activity in relation to depressive symptoms (CES-D score > or = 16) with control for potential confounders.

RESULTS

Adult vigorous physical activity was inversely associated with depressive symptoms. Women who reported vigorous exercise both in high school (> or = 5 hr per week) and adulthood (> or = 2 hr per week) had the lowest odds of depressive symptoms (OR = 0.76, 95% CI = 0.71-0.82) relative to never active women; the OR was 0.90 for women who were active in high school but not adulthood (95% CI = 0.85-0.96) and 0.83 for women who were inactive in high school but became active in adulthood (95% CI = 0.77-0.91). Although walking for exercise was not associated with risk of depressive symptoms overall, there was evidence of a weak inverse relation among obese women (Body Mass Index > or = 30).

CONCLUSIONS

Leisure time vigorous physical activity was associated with a reduced odds of depressive symptoms in U.S. Black women.

Bicarbonate reduces serum prolactin increase induced by exercise to exhaustion

PURPOSE

The aim of the study was to examine the effect of acid-base status on serum prolactin (PRL) concentration postexercise.

METHODS

Seven male recreational athletes participated in two experimental trials separated by 1 wk. In the respective trial, subjects received either a placebo infusion (normal isotonic saline) or an alkali infusion (isotonic sodium bicarbonate) before and during exercise. Venous and capillary blood samples were drawn at rest, immediately after a 10-min warm-up period, and after a maximal ramp test on a cycle ergometer, as well as at 3, 6, 10, and 15 min postexercise.

RESULTS

Power output, HR, capillary blood lactate concentration, carbon dioxide pressure (PCO2), and partial oxygen pressure (PO2) did not differ between trials at any point in time. Capillary PO2 did not change from resting values, but a significant increase (P < 0.05) was found from the end of warm-up to 3 min of the recovery period. Exercise induced a significant (P < 0.01) decrease in capillary blood bicarbonate concentration (HCO3-), pH, base excess (BE), and PCO2 at exhaustion and during the recovery period. Significantly higher HCO3-, pH, and BE were found during bicarbonate infusion and postexercise in comparison with the placebo trial. Serum PRL concentration was significantly increased 3 min postexercise until the end of the placebo trial, whereas after bicarbonate infusion, serum PRL concentration did not change from values at rest. Significant (P < 0.01) differences between trials in serum PRL concentration were found 10 and 15 min postexercise.

CONCLUSIONS

The present study suggests that acidosis is a stimulus for exercise-induced PRL secretion.

Central excitability does not limit postfatigue voluntary activation of quadriceps femoris

After fatigue, motor evoked potentials (MEP) elicited by transcranial magnetic stimulation and cervicomedullary evoked potentials elicited by stimulation of the corticospinal tract are depressed. These reductions in corticomotor excitability and corticospinal transmission are accompanied by voluntary activation failure, but this may not reflect a causal relationship. Our purpose was to determine whether a decline in central excitability contributes to central fatigue. We hypothesized that, if central excitability limits voluntary activation, then a caffeine-induced increase in central excitability should offset voluntary activation failure. In this repeated-measures study, eight men each attended two sessions. Baseline measures of knee extension torque, maximal voluntary activation, peripheral transmission, contractile properties, and central excitability were made before administration of caffeine (6 mg/kg) or placebo. The amplitude of vastus lateralis MEPs elicited during minimal muscle activation provided a measure of central excitability. After a 1-h rest, baseline measures were repeated before, during, and after a fatigue protocol that ended when maximal voluntary torque declined by 35% (Tlim). Increased prefatigue MEP amplitude ( P = 0.055) and cortically evoked twitch ( P < 0.05) in the caffeine trial indicate that the drug increased central excitability. In the caffeine trial, increased MEP amplitude was correlated with time to task failure ( r = 0.74, P < 0.05). Caffeine potentiated the MEP early in the fatigue protocol ( P < 0.05) and offset the 40% decline in placebo MEP ( P < 0.05) at Tlim. However, this was not associated with enhanced maximal voluntary activation during fatigue or recovery, demonstrating that voluntary activation is not limited by central excitability.

Use-dependent behavioral and neurochemical asymmetry in MPTP mice

Early in Parkinson's disease (PD) physical activity becomes difficult resulting in a more sedentary lifestyle. Clinical and experimental studies have found that increased activity following striatal dopamine loss leads to increased motor function. Decreased physical activity early in PD along with findings that increased physical activity results in functional improvement suggested to us that decreased physical activity during the period of nigrostriatal degeneration may not only be a symptom of the injury, but may also act to potentiate the degeneration. Using the bilateral MPTP mouse model of PD, we restricted use of one forelimb for the first 7 days post-injection. This transient behavioral manipulation during the period of dopamine degeneration resulted in a long-lasting deficit of the restricted forelimb. This was manifested as sustained asymmetrical use of the forelimbs during wall exploration, as well as a neurochemical imbalance between striatal hemispheres measured by immunoreactivity of the dopamine terminal markers, DAT, VMAT2 and TH. These results show a significant interaction between behavior and neurochemistry and suggest that a reduction in activity level may further exacerbate degeneration.

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

This study investigated the effect of caffeine on physical performance in healthy citizens aged > or =70 yr. The randomized, double-blind, placebo-controlled, crossover study was conducted in 15 men and 15 women recruited by their general practitioner. Participants abstained from caffeine for 48 h and were randomized to receive one capsule of placebo and then caffeine (6 mg/kg) or caffeine and then placebo with 1 wk in between. One hour after intervention, we measured reaction and movement times, postural stability, walking speed, cycling at 65% of expected maximal heart rate, perceived effort during cycling, maximal isometric arm flexion strength, and endurance. Analysis was by intention to treat, and P < 0.05 was regarded as significant. Caffeine increased cycling endurance by 25% [95% confidence interval (CI): 13-38; P = 0.0001] and isometric arm flexion endurance by 54% (95% CI: 29-83; P = 0.0001). Caffeine also reduced the rating of perceived exertion after 5 min of cycling by 11% (95% CI: 5-17; P = 0.002) and postural stability with eyes open by 25% (95% CI: 2-53; P = 0.03). Caffeine ingestion did not affect muscle strength, walking speed, reaction, and movement times. At the end of the study, 46% of participants correctly identified when they received caffeine and placebo. Caffeine increased exercise endurance in healthy citizens aged > or =70 yr, but the participants' reasons for stopping the test may have varied between subjects, as the cycling test was done at approximately 55% of maximal oxygen consumption. Further studies are required to investigate whether caffeine can be utilized to improve the physical performance of elderly citizens.

Nitric oxide synthesis is required for exercise-induced increases in hippocampal BDNF and phosphatidylinositol 3' kinase expression

Previous studies have shown that running exercise, either alone or in combination with antidepressant treatment, results in increased hippocampal BDNF levels. Nitric oxide (NO) is an important signaling molecule that has neuronal survival-promoting properties and has been shown to play an important role in plasticity associated with activating interventions. Herein, we administered the NO synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME), in conjunction with the monoamine oxidase inhibitor (MAOI) antidepressant, tranylcypromine, and voluntary wheel-running exercise to determine whether the enhancement in full-length BDNF mRNA occurring with these interventions is dependent upon NO synthesis. Our results demonstrate that both chronic exercise and chronic exercise-plus-tranylcypromine lead to enhanced hippocampal BDNF mRNA and protein expression. NOS inhibition prevents this effect of chronic exercise, but only partly prevents the effects of the exercise/antidepressant combination. Thus, the robust enhancement in BDNF mRNA occurring with exercise appears to be NO synthesis-dependent, but the intervention including antidepressant may enhance BDNF expression through alternative intracellular mechanisms. In addition, because exercise and antidepressants have both been shown to activate survival-promoting genes, we evaluated the levels of hippocampal phosphatidylinositol 3' kinase (PI-3K), an important signaling molecule within a principal neuronal survival-promoting intracellular pathway. Like BDNF mRNA and protein, exercise increases the expression of PI-3K, whereas concomitant NOS inhibition prevents this increase in PI-3K immunoreactivity above control levels. Our results are discussed in light of possible overlapping, but distinct intracellular pathways activated by exercise and antidepressant treatment to bring about enhancements in BDNF expression and other survival-promoting effects. These findings further demonstrate the potential therapeutic potential of chronic exercise to supplement pharmacotherapeutic treatment of mood disorders.

Mental and physical effort affect vigilance differently

Both physical and mental effort are thought to affect vigilance. Mental effort is known for its vigilance declining effects, but the effects of physical effort are less clear. This study investigated whether these two forms of effort affect the EEG and subjective alertness differently. Participants performed a physical task and were subsequently presented with a mental task, or vice versa. Mental effort decreased subjective alertness and increased theta power in the EEG. Both results suggest a vigilance decline. Physical effort, however, increased subjective alertness and alpha and beta1 power in the EEG. These findings point towards an increase in vigilance. Beta2 power was reduced after physical effort, which may reflect a decrease in active cognitive processing. No transfer effects were found between the effort conditions, suggesting that the effects of mental and physical effort are distinct. It is concluded that mental effort decreases vigilance, whereas physical effort increases vigilance without improving subsequent task performance.

Increased urinary excretion rates of serotonin and metabolites during bedrest

Astronauts are often on a voluntarily reduced energy intake during space missions, possibly caused by a metabolic or emotional stress response with involvement of the central serotonergic system (SES). We investigated 24 h urinary excretion (24 h-E) of serotonin (5-HT) and 5-hydroxyindol acidic acid as indicators of the SES in healthy males under two different normocaloric conditions: normal physical activity (NPA) and -6 degree head-down-tilt (HDT). HDT or NPA were randomly arranged with a recovery period of 6 months in between. 24 h-E of hormones varied widely among individuals. Values were higher in HDT compared to NPA. Assuming that the 24 h-E values are, beside being indicators for alterations in the number and metabolism of platelets. Also indicators of central SES, HDT condition seems to activate central SES in a higher degree compared to NPA. Therefore, changes in central SES might be involved in the mechanisms associated with space flight or microgravity, including possible maladaptations such as voluntary undernutrition.

Exercise and Its Effects on the Central Nervous System

Exercise can have profound effects on numerous biologic systems within the human body, including the central nervous system (CNS). The inherent complexity of the CNS, and the methodologic difficulties in evaluating its in vivo neurochemistry in humans, provide challenges to investigators studying the impact of exercise on the CNS. As a result, our knowledge in this area of exercise science remains relatively limited. However, advances in research technology are allowing investigators to gain valuable insight into the neurobiologic mechanisms that contribute to the bidirectional communication that occurs between the periphery and the CNS during exercise. This article examines how exercise-induced alterations in the CNS contribute to central fatigue and the overtraining syndrome, and how exercise can influence psychologic wellbeing and cognitive function.

Blood-brain barrier integrity may be threatened by exercise in a warm environment

Seven active men were recruited to examine changes in the serum concentration of S100beta, a proposed peripheral marker of blood-brain barrier permeability, following prolonged exercise in temperate (T) and warm (W) conditions. Subjects were seated immersed to the neck in water at 35.0 (0.1) degrees C (T) or 39.0 (0.1) degrees C (W) for 30 min. Subjects then entered a room maintained at either 18.3 (1.8) degrees C (T) or 35.0 (0.3) degrees C (W) and completed 60 min of cycle exercise at 60% peak oxygen uptake. Serum S100beta concentration was elevated after exercise in the W trial (+0.12 (0.10) microg/l; P = 0.02) but not after the T trial (P = 0.238). Water immersion and exercise elevated core temperature by 2.1 (0.5) degrees C to 39.5 (0.3) degrees C at the end of exercise in the W trial compared with a 0.9 (0.2) degrees C increase during the T trial (P < 0.001). Weighted mean skin temperature was higher throughout the W trial compared with the T trial (P < 0.001). Heart rate (P < 0.001) and blood glucose (P < 0.001) and lactate (P < 0.001) concentrations were elevated to a greater extent during exercise in the W trial than in the T trial. Ratings of perceived exertion (P < 0.001) and thermal comfort (P < 0.001) were markedly higher throughout the W trial than in the T trial. The results of this study demonstrate that serum S100beta was elevated after water immersion and prolonged exercise in a warm environment, suggesting that blood-brain barrier permeability may be altered.

The Science of Cycling

The aim of this review is to provide greater insight and understanding regarding the scientific nature of cycling. Research findings are presented in a practical manner for their direct application to cycling. The two parts of this review provide information that is useful to athletes, coaches and exercise scientists in the prescription of training regimens, adoption of exercise protocols and creation of research designs. Here for the first time, we present rationale to dispute prevailing myths linked to erroneous concepts and terminology surrounding the sport of cycling. In some studies, a review of the cycling literature revealed incomplete characterisation of athletic performance, lack of appropriate controls and small subject numbers, thereby complicating the understanding of the cycling research. Moreover, a mixture of cycling testing equipment coupled with a multitude of exercise protocols stresses the reliability and validity of the findings. Our scrutiny of the literature revealed key cycling performance-determining variables and their training-induced metabolic responses. The review of training strategies provides guidelines that will assist in the design of aerobic and anaerobic training protocols. Paradoxically, while maximal oxygen uptake (V-O(2max)) is generally not considered a valid indicator of cycling performance when it is coupled with other markers of exercise performance (e.g. blood lactate, power output, metabolic thresholds and efficiency/economy), it is found to gain predictive credibility. The positive facets of lactate metabolism dispel the 'lactic acid myth'. Lactate is shown to lower hydrogen ion concentrations rather than raise them, thereby retarding acidosis. Every aspect of lactate production is shown to be advantageous to cycling performance. To minimise the effects of muscle fatigue, the efficacy of employing a combination of different high cycling cadences is evident. The subconscious fatigue avoidance mechanism 'teleoanticipation' system serves to set the tolerable upper limits of competitive effort in order to assure the athlete completion of the physical challenge. Physiological markers found to be predictive of cycling performance include: (i) power output at the lactate threshold (LT2); (ii) peak power output (W(peak)) indicating a power/weight ratio of > or =5.5 W/kg; (iii) the percentage of type I fibres in the vastus lateralis; (iv) maximal lactate steady-state, representing the highest exercise intensity at which blood lactate concentration remains stable; (v) W(peak) at LT2; and (vi) W(peak) during a maximal cycling test. Furthermore, the unique breathing pattern, characterised by a lack of tachypnoeic shift, found in professional cyclists may enhance the efficiency and metabolic cost of breathing. The training impulse is useful to characterise exercise intensity and load during training and competition. It serves to enable the cyclist or coach to evaluate the effects of training strategies and may well serve to predict the cyclist's performance. Findings indicate that peripheral adaptations in working muscles play a more important role for enhanced submaximal cycling capacity than central adaptations. Clearly, relatively brief but intense sprint training can enhance both glycolytic and oxidative enzyme activity, maximum short-term power output and V-O(2max). To that end, it is suggested to replace approximately 15% of normal training with one of the interval exercise protocols. Tapering, through reduction in duration of training sessions or the frequency of sessions per week while maintaining intensity, is extremely effective for improvement of cycling time-trial performance. Overuse and over-training disabilities common to the competitive cyclist, if untreated, can lead to delayed recovery.

Cerebral ammonia uptake and accumulation during prolonged exercise in humans

We evaluated whether peripheral ammonia production during prolonged exercise enhances the uptake and subsequent accumulation of ammonia within the brain. Two studies determined the cerebral uptake of ammonia (arterial and jugular venous blood sampling combined with Kety-Schmidt-determined cerebral blood flow; n = 5) and the ammonia concentration in the cerebrospinal fluid (CSF; n = 8) at rest and immediately following prolonged exercise either with or without glucose supplementation. There was a net balance of ammonia across the brain at rest and at 30 min of exercise, whereas 3 h of exercise elicited an uptake of 3.7 +/- 1.3 micromol min(-1) (mean +/-s.e.m.) in the placebo trial and 2.5 +/- 1.0 micromol min(-1) in the glucose trial (P < 0.05 compared to rest, not different across trials). At rest, CSF ammonia was below the detection limit of 2 microm in all subjects, but it increased to 5.3 +/- 1.1 microm following exercise with glucose, and further to 16.1 +/- 3.3 microm after the placebo trial (P < 0.05). Correlations were established between both the cerebral uptake (r2 = 0.87; P < 0.05) and the CSF concentration (r2 = 0.72; P < 0.05) and the arterial ammonia level and, in addition, a weaker correlation (r2 = 0.37; P < 0.05) was established between perceived exertion and CSF ammonia at the end of exercise. The results let us suggest that during prolonged exercise the cerebral uptake and accumulation of ammonia may provoke fatigue, e.g. by affecting neurotransmitter metabolism.

The effects of chronic treadmill and wheel running on behavior in rats

In order to better understand the behavioral adaptations induced by physical activity, this set of experiments assessed the effects of two modes of running exercise on a battery of behavioral tests. The effects of 8 weeks of forced treadmill running and voluntary wheel running on behavior measures in the elevated plus maze, open field, social interaction and conditioned freezing paradigms were investigated. Eight weeks of treadmill running did not alter behavior in any test paradigm. Rats given unrestricted access to running wheels (WR) had a lower percent open arm time (6.0+/-2.3%) compared to locked wheel controls (LC) (20.7+/-5.7%) in the elevated plus maze. WR also showed decreased entries into center (0.2+/-0.2) and crossed fewer lines (61.0+/-14.9) in the open field compared to control groups. Both WR and LC groups showed increased social interaction; however, these differences are attributed to housing conditions. The effects of 4 weeks of wheel running on elevated plus maze and open field behavior were also investigated to address the possibility of a temporal effect of exercise on behavior. Four weeks of wheel running produced behavioral changes in the open field similar to those found at 8 weeks, but not in the elevated plus maze suggesting a temporal effect of wheel running on plus maze behavior. The behavioral adaptations found after 4 and 8 weeks of wheel running were not due solely to enriched environment and appear to be indicative of enhanced defensive behavior.

Effects of long duration exercise on cognitive function, blood glucose, and counterregulatory hormones in male cyclists

Electrocortical effects of long duration exercise on cognitive function were investigated by analyzing P300 amplitude and latency changes during a 3-h cycling exercise. P300 components were measured in 12 well-trained cyclists and blood glucose, cortisol, insulin, glycerol, and free fatty acids (FFAs) epinephrine and norepinephrine were analyzed. Results indicated that P300 components were affected by exercise with a temporary increase in amplitude between the 1st and the 2nd hour and an increase in latency after 2 h of exercise concomitant with some hormonal changes, including an increase in cortisol and epinephrine and a decrease in blood glucose. These findings suggest a combined effect of arousal and central fatigue on electrocortical indices of cognitive function during acute physical exercise.

Comparison between dopaminergic agents and physical exercise as treatment for periodic limb movements in patients with spinal cord injury

STUDY DESIGN

Randomized controlled trial of physical exercise and dopaminergic agonist in persons with spinal cord injury and periodic leg movement (PLM).

OBJECTIVE

The objective of the present study was to compare the effectiveness of physical exercise and of a dopaminergic agonist in reducing the frequency of PLM.

SETTING

Centro de Estudos em Psicobiologia e Exercício. Universidade Federal de São Paulo, Brazil.

METHODS

A total of 13 volunteers (mean age: 31.6+/-8.3 years) received L-DOPA (200 mg) and benserazide (50 mg) 1 h before sleeping time for 30 days and were then submitted to a physical exercise program on a manual bicycle ergometer for 45 days (3 times a week).

RESULTS

Both L-DOPA administration (35.11-19.87 PLM/h, P<0.03) and physical exercise (35.11-18.53 PLM/h, P<0.012) significantly reduced PLM; however, no significant difference was observed between the two types of treatment.

CONCLUSIONS

The two types of treatment were found to be effective in the reduction of PLM; however, physical exercise is indicated as the first treatment approach, while dopaminergic agonists or other drugs should only be recommended for patients who do not respond to this type of treatment.

Hormonal responses during prolonged exercise are influenced by a selective DA/NA reuptake inhibitor

OBJECTIVE

A decrease in dopamine activity is thought to lead to a reduction in motivation and arousal and therefore to the "central" component of fatigue. The purpose of the present study was to investigate the effects of a dopamine (DA) noradrenaline (NA) reuptake inhibitor, bupropion (Zyban), on exercise performance and on the hormonal response to exercise.

METHODS

Eight healthy well trained male cyclists (Watt(max) 397+/-15 W) participated in the study. Subjects completed one maximal exercise test (to determine maximal power output Watt(max)), and two endurance performance tests (time trials) in a double blind randomised cross-over design. Subjects took either placebo capsules (lactose) or 2 x 300 mg bupropion (BUP). Blood samples were collected for adrenocorticotropin (ACTH), prolactin, cortisol, growth hormone, beta-endorphins, and catecholamines.

RESULTS

Performance was not influenced by BUP (placebo: 89+/-1 min; BUP 2 x 300 mg: 89+/-0.7 min). All hormones increased during exercise in all trials. Cortisol plasma concentrations were significantly higher in the BUP trial at rest, at min 60, and at the end of exercise, while beta-endorphins were higher in the BUP trial at the end of exercise and during recovery, and ACTH at the end of exercise.

CONCLUSION

From the present results, we can conclude that bupropion had a more marked central noradrenergic effect (compared to dopaminergic) on the hormonal response to exercise, but no effect on the outcome of performance.

Implicações do sistema serotoninérgico no exercício físico

Este trabalho revisa as alterações cerebrais de serotonina quando da oferta de nutrientes (carboidratos, proteínas e aminoácidos) durante atividade física. Utilizando a estratégia nutricional, o foco é o aminoácido precursor da serotonina cerebral: o triptofano; sendo um aminoácido essencial, é possível sua modulação via dieta. Uma abordagem emergente e polêmica está relacionada à fadiga durante atividade de curta e longa duração e sua relação com a função serotoninérgica cerebral. Os mecanismos propostos para o desenvolvimento de fadiga precoce durante o exercício se apresentam amplamente inexplorados. Assim serão discutidos os prováveis mecanismos envolvidos na "hipótese da fadiga central" e a oferta de carboidratos e aminoácidos como estratégia para retardar este fato durante atividade física e alcançar melhora no rendimento esportivo.

Cerebral perturbations provoked by prolonged exercise

This review addresses cerebral metabolic and neurohumoral alterations during prolonged exercise in humans with special focus on associations with fatigue. Global energy turnover in the brain is unaltered by the transition from rest to moderately intense exercise, apparently because exercise-induced activation of some brain regions including cortical motor areas is compensated for by reduced activity in other regions of the brain. However, strenuous exercise is associated with cerebral metabolic and neurohumoral alterations that may relate to central fatigue. Fatigue should be acknowledged as a complex phenomenon influenced by both peripheral and central factors. However, failure to drive the motorneurons adequately as a consequence of neurophysiological alterations seems to play a dominant role under some circumstances. During exercise with hyperthermia excessive accumulation of heat in the brain due to impeded heat removal by the cerebral circulation may elevate the brain temperature to >40 degrees C and impair the ability to sustain maximal motor activation. Also, when prolonged exercise results in hypoglycaemia, perceived exertion increases at the same time as the cerebral glucose uptake becomes low, and centrally mediated fatigue appears to arise as the cerebral energy turnover becomes restricted by the availability of substrates for the brain. Changes in serotonergic activity, inhibitory feed-back from the exercising muscles, elevated ammonia levels, and alterations in regional dopaminergic activity may also contribute to the impaired voluntary activation of the motorneurons after prolonged and strenuous exercise. Furthermore, central fatigue may involve depletion of cerebral glycogen stores, as signified by the observation that following exhaustive exercise the cerebral glucose uptake increases out of proportion to that of oxygen. In summary, prolonged exercise may induce homeostatic disturbances within the central nervous system (CNS) that subsequently attenuates motor activation. Therefore, strenuous exercise is a challenge not only to the cardiorespiratory and locomotive systems but also to the brain.

Exercise, antidepressant treatment, and BDNF mRNA expression in the aging brain

Principal mental disorders affecting the geriatric population include dementia and depression. A lack of trophic support is thought to contribute to the pathology of these disorders. Physical activity and antidepressant treatment increase the expression of brain-derived neurotrophic factor (BDNF) in the young rat hippocampus. Herein, we investigated the responsiveness of the aging rat hippocampus to antidepressant treatment and voluntary exercise. In situ hybridization revealed that, in young animals, exercise, antidepressant treatment, or their combination elevated BDNF mRNA levels in several hippocampal regions, most notably in the CA3, CA4, and dentate gyrus (DG). This effect was rapid (detectable at 2 days) and sustainable to 20 days. In aged (22-month-old) rats, hippocampal responsiveness to antidepressant treatment and exercise was also rapid and sustainable, but evident mostly in the CA1 and CA2. Daily swimming also revealed that small amounts of activity led to marked elevations in hippocampal BDNF mRNA. The differences in regional patterns of BDNF mRNA elevations between young and aged animals observed with running were maintained with this different exercise modality. Our results indicate that the aged brain is responsive to exercise and antidepressant treatment, and changes in regional response patterns may reflect shifts in hippocampal physiology during the lifespan.

Recovery from fatigue: changes in local brain 2-[18F]fluoro-2-deoxy-d-glucose utilization measured by autoradiography and in brain monoamine levels of rat

We recently established an animal model of fatigue in which rats were kept in a cage filled with water to a height of 1.5 cm for 5 days. In this way, after the fatigue session, they were returned to their home cage. Rats resting for 15 min or 2 h showed reduced 2-[18F]fluoro-2-deoxy-D-glucose uptake in their brain. Rats resting for 1 h showed a significantly increased ratio of 5-hydroxyindoleacetic acid/5-hydroxytryptamine, an index of serotonin turnover, in the frontal cortex, hippocampus, and cerebellum, and the ratio of [3,4-dihydroxyphenylacetic acid+homovanillic acid]/dopamine, an index of dopamine turnover, tended to be increased as compared with the control. These data suggest that improvement of glucose uptake and increased serotonergic and dopaminergic neuronal activities are associated with recovery from central fatigue.

Establishment and assessment of a rat model of fatigue

To establish an animal model of fatigue, we kept rats in a cage filled with water to a height of 1.5 cm. We selected a weight-loaded forced swimming test for evaluation of the extent of fatigue. Animals kept in the wet cage for 5 days showed a reduction in 2-[18F]fluoro-2-deoxy-D-glucose uptake into their brain. The session for 1 day showed significantly increased 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) and [3,4-dihydroxyphenyl-acetic acid (DOPAC)+homovanillic acid (HVA)]/dopamine (DA) ratios in all brain regions, but the session for 5 days showed the restoration of the 5-HIAA/5-HT ratio in the hippocampus and hypothalamus and in the (DOPAC+HVA)/DA ratio in the striatum and hypothalamus. Our data suggest that decreased glucose uptake and insufficient serotonin and dopamine turnover introduced by deprivation of rest were correlated with central fatigue.

Effects of venlafaxine on extracellular 5-HT, dopamine and noradrenaline in the hippocampus and on peripheral hormone concentrations in the rat in vivo

The purpose of the present study was to study the effect of an acute dose of the serotonin (5-HT) - noradrenaline (NA) reuptake inhibitor venlafaxine on extracellular concentrations of 5-HT, NA and dopamine (DA) in the hippocampus and on the peripheral hormone concentrations in freely moving rats. Blood obtained from a catheter placed in the vena femoralis was analyzed for adrenocorticotropin (ACTH), beta-endorphins, prolactin (PRL), growth hormone (GH) and cortisol. Collections are referred to pre and post injection of 20 mg/kg of venlafaxine. Extracellular hippocampal NA and 5-HT as determined with in vivo microdialysis increased significantly after drug injection. PRL and ACTH were significantly affected by the drug. At the selected dose venlafaxine is able to increase the release of 5-HT but also of NA in rat hippocampus. Due to the dual reuptake properties of the drug and the functional interconnection of the NA and the 5-HT systems, the observed effects on peripheral hormones are possibly mediated by a combined action of these 2 systems.

Investigation of the effects of pool-based exercise on fibromyalgia syndrome

OBJECTIVE

The aim of this study was to compare pool-based exercise and balneotherapy in fibromyalgia syndrome (FMS) patients.

METHODS

Fifty female patients diagnosed with FMS according to the American College of Rheumatism (ACR) criteria were randomly assigned to two groups: group 1 (n=25) with pool-based exercise, and in group 2 (n=25) balneotherapy was applied in the same pool without any exercise for 35 min three times a week for 12 weeks. In both groups, pre- (week 0) and post-treatment (weeks 12 and 24) evaluation was performed by one of the authors, who was blind to the patient group. Evaluation parameters included pain, morning stiffness, sleep, tender points, global evaluation by the patient and the physician, fibromyalgia impact questionnaire, chair test, and Beck depression inventory. Statistical analysis was done on data collected from three evaluation stages.

RESULTS

Twenty-four exercise and 22 balneotherapy patients completed the study. Pretreatment (week 0) measurements did not show any difference between the groups. In group 1, statistically significant improvement was observed in all parameters ( P<0.01) except for the chair test at both weeks 12 and 24. In group 2, week 12 measurements showed significant improvement in all parameters ( P<0.01) except for the chair test and Beck depression inventory. Week 24 evaluation results in group 2 showed significant improvements in pain and fatigue according to visual analogue scale (VAS), 5-point scale, number of tender points, algometric and myalgic scores, and patient and physician global evaluation (P<0.01 and P<0.05, respectively), while improvements were nonsignificant in morning stiffness, sleep, fibromyalgia impact questionnaire (FIQ), chair test, and Beck depression inventory parameters in this group. Comparison of the two groups based on the post-treatment (weeks 12 and 24) percent changes and difference scores relative to pretreatment (week 0) values failed to show a significant difference between the groups for any parameter except Beck depression inventory (P<0.01).

CONCLUSION

The results of our study showed that pool-based exercise had a longer-lasting effect on some of the FMS symptoms, but statistical analysis failed to show a significant superiority of pool-based exercise over balneotherapy without exercise. While we believe that exercise is a gold standard in FMS treatment, we also suggest in light of our results that balneotherapy is among the valid treatment options in FMS, and further research regarding the type and duration of the exercise programs is necessary.

The influence of specific noradrenergic and serotonergic lesions on the expression of hippocampal brain-derived neurotrophic factor transcripts following voluntary physical activity

Previous studies have shown that hippocampal brain-derived neurotrophic factor (BDNF) mRNA levels are significantly increased in rats allowed free access to exercise wheels and/or administered antidepressant medications. Enhancement of BDNF may be crucial for the clinical effect of antidepressant interventions. Since increased function of the noradrenergic and/or serotonergic systems is thought to be an important initial mechanism of antidepressant medications, we sought to test the hypothesis that noradrenergic or serotonergic function is essential for the increased BDNF transcription occurring with exercise. In addition, individual transcript variants of BDNF were examined, as evidence exists they are differentially regulated by discrete interventions, and are expressed in distinct sub-regions of the hippocampus. The neurotransmitter system-specific neurotoxins p-chloroamphetamine (serotonergic) and N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (noradrenergic) were administered to rats prior to commencing voluntary wheel-running activity. In situ hybridization experiments revealed an absence of exercise-induced full-length BDNF mRNA elevations in the hippocampi of noradrenergic-lesioned rats. In addition, the striking elevation of the exon I transcript in the dentate gyrus was removed with this noradrenergic lesion. In contrast, other transcript variants (exons II and III) were elevated in several hippocampal regions as a result of this lesion. In serotonin-lesioned rats, the significant increases in full-length BDNF, exon I and exon II mRNA levels were sustained without alteration (with the exception of exon IV in the cornus ammonis subregion 4, CA4). Overall, these results indicate that an intact noradrenergic system may be crucial for the observed ability of exercise to enhance full-length and exon I hippocampal BDNF mRNA expression. In addition, these results suggest that the promoter linked to exon I may provide a major regulatory point for BDNF mRNA expression in the dentate gyrus. Elevations of other exons, such as II and III, may require the activation of separate neurotransmitter systems and intracellular pathways.

Neurohumoral responses during prolonged exercise in humans

This study examined neurohumoral alterations during prolonged exercise with and without hyperthermia. The cerebral oxygen-to-carbohydrate uptake ratio (O2/CHO = arteriovenous oxygen difference divided by arteriovenous glucose difference plus one-half lactate), the cerebral balances of dopamine, and the metabolic precursor of serotonin, tryptophan, were evaluated in eight endurance-trained subjects during exercise randomized to be with or without hyperthermia. The core temperature stabilized at 37.9 +/- 0.1 degrees C (mean +/- SE) in the control trial, whereas it increased to 39.7 +/- 0.2 degrees C in the hyperthermic trial, with a concomitant increase in perceived exertion (P < 0.05). At rest, the brain had a small release of tryptophan (arteriovenous difference of -1.2 +/- 0.3 micromol/l), whereas a net balance was obtained during the two exercise trials. Both the arterial and jugular venous dopamine levels became elevated during the hyperthermic trial, but the net release from the brain was unchanged. During exercise, the O2/CHO was similar across trials, but, during recovery from the hyperthermic trial, the ratio decreased to 3.8 +/- 0.3 (P < 0.05), whereas it returned to the baseline level of approximately 6 within 5 min after the control trial. The lowering of O2/CHO was established by an increased arteriovenous glucose difference (1.1 +/- 0.1 mmol/l during recovery from hyperthermia vs. 0.7 +/- 0.1 mmol/l in control; P < 0.05). The present findings indicate that the brain has an increased need for carbohydrates during recovery from strenuous exercise, whereas enhanced perception of effort as observed during exercise with hyperthermia was not related to alterations in the cerebral balances of dopamine or tryptophan.

Noradrenergic and serotonergic blockade inhibits BDNF mRNA activation following exercise and antidepressant

Antidepressants and physical exercise have been shown to increase the transcription of hippocampal brain-derived neurotrophic factor (BDNF). Much evidence regarding the initial actions of antidepressant medications as well as exercise leads to the hypothesis that noradrenergic (NE) and/or serotonergic (5-HT) activation is a key element in the BDNF transcriptional elevation common to both interventions. Currently, we used short-term beta-adrenergic, 5-HT(1A), or 5-HT(2A/C) receptor blockade to characterize the influence of NE and 5-HT systems on BDNF transcription during physical exercise and antidepressant treatment. In situ hybridization revealed that beta-adrenergic blockade significantly blunted the BDNF mRNA elevations due to exercise, and also inhibited the modest elevations in the CA3 and dentate gyrus following short-term treatment with tranylcypromine. In contrast, 5-HT(2A/C) blockade only minimally altered exercise-induced BDNF mRNA levels, but inhibited up-regulation of BDNF transcription via tranylcypromine. Finally, 5-HT(1A) blockade did not inhibit exercise-induced BDNF mRNA elevations, but significantly enhanced levels above those achieved with exercise alone in the CA4. These results suggest that NE activation via beta-adrenergic receptors may be essential for both exercise and antidepressant-induced BDNF regulation. 5-HT(1A) and 5-HT(2A/C) activation, on the other hand, appear to be most important for antidepressant-induced BDNF regulation, but may also participate significantly in exercise-induced regulation in the CA4.

Exercise, Fatigue, Neurotransmission and the Influence of the Neuroendocrine Axis

Fatigue during prolonged exercise has traditionally been attributed to the occurrence of a "metabolic end point", where muscle glycogen concentrations are depleted, plasma glucose concentrations are reduced, and plasma free fatty acid levels are elevated. But there exists also a "central fatigue hypothesis" which is based on the increase in the concentration of brain serotonin (5-Hydroxytryptamine or 5-HT) during exercise. However, the physiological mechanisms for central fatigue are largely unexplored, therefore we designed several experiments where central serotonergic activity was manipulated. These animal and human experiments showed that although brain neurotransmission had significantly increased, the supplementation with L-TRP did not lead to premature fatigue. In human studies we used several reuptake inhibitors in order to modify brain activity during exercise. These results clearly showed that time trial performance could not be influenced, but that during prolonged exercise the brain activity can be influenced, as measured by the peripheral hormones.

Forced limb-use and recovery following brain injury

Animals subjected to exercise display significant alterations in brain function and neurochemistry, reflecting the innate plasticity of the adult brain to environmental challenges. Following injury, the brain is sensitive to reorganization and regeneration, and thus may be primed for influence by external behavioral demand such as increased use of an injured forelimb. The focus of this review is on the effects of altered use of the impaired forelimb in unilateral rodent models of brain injury. Both the benefits of increased use and the detrimental effects of decreased use following injury will be discussed.

Effects of acute physical exercise characteristics on cognitive performance

The effect of physical exercise on mental function has been widely studied from the beginning of the 20th century. However, the contradictory findings of experimental research have led authors to identify several methodological factors to control in such studies including: (i) the nature of the psychological task; and (ii) the intensity and duration of physical exercise. The purpose of this article is to provide information, from the perspective of performance optimisation, on the main effects of physical task characteristics on cognitive performance. Within this framework, some consistent results have been observed during the last decade. Recent studies, using mainly complex decisional tasks, have provided the research community with clear support for an improvement of cognitive performance during exercise. Diverse contributing factors have been suggested to enhance cognitive efficacy. First, an increase in arousal level related to physical exertion has been hypothesised. Improvement in decisional performance has been observed immediately after the adrenaline threshold during incremental exercise. Such positive effects could be enhanced by nutritional factors, such as carbohydrate or fluid ingestion, but did not seem to be influenced by the level of fitness. Second, the mediating role of resource allocation has been suggested to explain improvement in cognitive performance during exercise. This effect highlights the importance of motivational factors in such tasks. Finally, when the cognitive performance was performed during exercise, consistent results have indicated that the dual task effect was strongly related to energetic constraints of the task. The greater the energy demand, the more attention is used to control movements.

Forced nonuse in unilateral parkinsonian rats exacerbates injury

Diagnosis of Parkinson's disease (PD) is based on the presentation of clinical symptoms such as bradykinesia, resting tremor, and rigidity. However, one feature of PD that often begins years before diagnosis is decreased physical activity. We hypothesized that this depressed activity is not only a symptom of the early dopaminergic loss but also a catalyst in the degenerative process. Two experiments were performed to test this hypothesis. First, rats were exposed to a mild dose of 6-hydroxydopamine unilaterally into the nigrostriatal dopamine (DA) projections, which would normally result in an approximately 20% DA loss and no detectable behavioral asymmetries. A subset of these lesioned animals then had a cast applied for 7 d to the contralateral forelimb. After the cast was removed, these animals displayed long-term behavioral asymmetry and exacerbation of neurochemical loss (approximately 60% depletion). Second, a group of animals received a high dose of 6-hydroxydopamine that normally would yield a severe loss of nigrostriatal terminals (approximately 90% loss) and chronic sensorimotor deficits. During the first 7 d after neurotoxin exposure, a subset of these animals were forced to rely on the contralateral forelimb, a procedure we have previously reported to protect DA terminals and behavioral function. Some of these rats then had the use of their "recovered" forelimb restricted during the second or third week after lesioning. This precipitated a severe and chronic loss of DA terminals and functional deficits. These results suggest decreased physical activity not only is a symptom of PD but also may act to potentiate the underlying degeneration.

Informed decision-making on sympathomimetic use in sport and health

The International Olympic Committee, the World Anti-Doping Agency, and International Sport Federations have banned and restricted the use of many stimulants including prescription and over-the-counter medications and dietary supplements. In addition to elite athletes, people of all ages use stimulants in attempts to improve athletic performance, alter body composition, and increase levels of energy. Here we introduce a seven-stage model designed to facilitate informed decision-making by individuals taking or thinking of taking stimulants for sport, health, and/or appearance reasons. We review for amphetamines, over-the counter sympathomimetics, and caffeine their performance-enhancing and performance-degrading effects, health benefits and mechanisms of action, medical side effects, and legal, ethical, safety, and financial implications.

No effect of a noradrenergic reuptake inhibitor on performance in trained cyclists

INTRODUCTION

According to the central fatigue hypothesis, serotonin (5-HT) is related to fatigue, whereas the noradrenergic system is primarily concerned with arousal and motivation, and therefore hypothesized to enhance performance. The purpose of the present study was to examine the effects of a selective noradrenergic reuptake inhibitor (reboxetine 2 x 4 mg REB-NARI) on exercise performance.

METHODS

Seven healthy well-trained male cyclists (age: 23 +/- 1.7 yr, height: 182 +/- 5.8 cm, weight: 73.5 +/- 8.5 kg, VO2max: 73.5 +/- 6.4 mL x kg(-1) x min(-1), Watt(max): 376 +/- 11.7 W) participated to the study. Subjects completed two endurance tests (time trials) starting at 65% Wmax in a double-blind randomized cross-over design. Blood samples were collected for adrenocorticotropin, prolactin, cortisol, growth hormone (GH), beta-endorphins, and catecholamines and were taken at 30-min time intervals until the end of exercise. Performance was analyzed with a paired t-test, whereas data for hormonal and metabolic differences during the trials were analyzed using an ANOVA repeated measures design and an LSD-planned comparisons test. Significance level was set at P < 0.05.

RESULTS

Performance was not influenced by the NARI (REB: 97 min +/- 3 min, placebo (PLAC): 92 min +/- 1 min). All hormones increased during exercise except for GH in the REB trial, which was significantly lower than PLAC. The other hormones were significantly higher in the REB trial versus the PLAC trial at the end of exercise and during recovery.

CONCLUSION

In conclusion, the results demonstrate that the drug had a central effect. In particular, the higher resting GH concentrations indicated a marked and selective noradrenergic effect of REB. However, performance was not influenced by a selective NARI in well-trained endurance athletes.

Brain microdialysis in exercise research

During the last 5 to 10 years, the microdialysis technique has been used to explore neurotransmitter release during exercise. Microdialysis can collect virtually any substance from the brains of freely moving animals with a limited amount of tissue trauma. It allows the measurement of local neurotransmitter release in combination with ongoing behavioural changes such as exercise. Several groups examined the effect of treadmill running on extracellular neurotransmitter levels. Microdialysis probes were implanted in different brain areas to monitor diverse aspects of locomotion (striatum, hippocampus, nucleus accumbens, frontal cortex, spinal cord), food reward (hypothalamus, hippocampus, cerebral cortex), thermoregulation (hypothalamus). Some studies combined microdialysis with running on a treadmill to evaluate motor deficit and improvement following dopaminergic grafts in 6-hydroxydopamine lesioned rats, or combined proton nuclear magnetic resonance spectroscopy and cortical microdialysis to observe intra- plus extracellular brain glucose variations. This method allows us to understand neurotransmitter systems underlying normal physiological function and behaviour. Because of the growing interest in exercise and brain functioning, it should be possible to investigate increasingly subtle behavioural and physiological changes within the central nervous system. There is now compelling evidence that regular physical activity is associated with significant physiological, psychological and social benefits in the general population. In contrast with our knowledge about the peripheral adaptations to exercise, studies relating exercise to brain neurotransmitter levels are scarce. It is of interest to examine the effect of short and long term exercise on neurotransmitter release, since movement initiation and control of locomotion have been shown to be related to striatal neurotransmitter function, and one of the possible therapeutic modalities in movement, and mental disorders is exercise therapy. Until very recently most experimental studies on brain chemistry were conducted with postmortem tissue. However, in part because of shortcomings with postmortem methods, and in part because of the desire to be able to directly relate neurochemistry to behaviour, there has been considerable interest in the development of 'in vivo' neurochemical methods. Because total tissue levels may easily mask small but important neurochemical changes related to activity, it is important to sample directly in the extracellular compartment of nervous tissue in living animals. Since the chemical interplay between cells occurs in the extracellular fluid, there was a need to access this compartment in the intact brain of living and freely moving animals. Estimation of the transmitter content in this compartment is believed to be directly related to the concentration at the site where these compounds are functionally released: in the synaptic cleft. As measurements in the synapse are not yet possible, in vivo measurements in the extracellular fluid appear to provide the most directly relevant information currently available. This article provides an overview of the in vivo microdialysis technique as a method for measuring in the extracellular space, and its application in exercise science. Although this technique has been used in different tissues such as brain, adipose tissue, spinal cord and muscle, in animals as well as humans, we will focus on the use of this in vivo method in brain tissue. Recently two excellent reviews on the application of microdialysis in human experiments especially in subcutaneous tissue have been published, and we refer the interested reader to these articles.

Diagnosis of overtraining: what tools do we have?

The multitude of publications regarding overtraining syndrome (OTS or 'staleness') or the short-term 'over-reaching' and the severity of consequences for the athlete are in sharp contrast with the limited availability of valid diagnostic tools. Ergometric tests may reveal a decrement in sport-specific performance if they are maximal tests until exhaustion. Overtrained athletes usually present an impaired anaerobic lactacid performance and a reduced time-to-exhaustion in standardised high-intensity endurance exercise accompanied by a small decrease in the maximum heart rate. Lactate levels are also slightly lowered during submaximal performance and this results in a slightly increased anaerobic threshold. A reduced respiratory exchange ratio during exercise still deserves further investigation. A deterioration of the mood state and typical subjective complaints ('heavy legs', sleep disorders) represent sensitive markers, however, they may be manipulated. Although measurements at rest of selected blood markers such as urea, uric acid, ammonia, enzymes (creatine kinase activity) or hormones including the ratio between (free) serum testosterone and cortisol, may serve to reveal circumstances which, for the long term, impair the exercise performance, they are not useful in the diagnosis of established OTS. The nocturnal urinary catecholamine excretion and the decrease in the maximum exercise-induced rise in pituitary hormones, especially adrenocorticotropic hormone and growth hormone, and, to a lesser degree, in cortisol and free plasma catecholamines, often provide interesting diagnostic information, but hormone measurements are less suitable in practical application. From a critical review of the existing overtraining research it must be concluded that there has been little improvement in recent years in the tools available for the diagnosis of OTS.

Effect of ingesting caffeine and ephedrine on 10-km run performance

BACKGROUND

The ingestion of either caffeine (C) or ephedrine (E) has been shown to improve performance during high-intensity aerobic activity lasting 10-20 min, with an additive effect being found when the combination (C + E) was ingested. It was the purpose of this study to determine if the addition of E to C would improve performance in activity lasting longer than 20 min.

METHODS

One and one half hours after ingesting a placebo (P), C (4 mg/kg), E (0.8 mg/kg), or C + E, 12 subjects performed a 10-km run while wearing a helmet and backpack weighing 11 kg. The trials were performed in a climatic suite at 12-13 degrees C, on a treadmill where the speed was regulated by the subject. VO(2), VCO(2), V(E), heart rate (HR), and rating of perceived exertion (RPE) were measured during the run at 15 and 30 min, and again when the individual reached 9 km. Blood was sampled at 15 and 30 min and again at the end of the run and assayed for lactate, glucose, and catecholamines.

RESULTS

Run times (mean +/- SD), in minutes, were for C (46.0 +/- 2.8), E (45.5 +/- 2.9), C + E (45.7 +/- 3.3), and P (46.8 +/- 3.2). The run times for the E trials (E and C + E) were significantly reduced compared with the non-E trials (C and P). Pace was increased for the E trials compared with the non-E trials over the last 5 km of the run. VO(2) was not affected by drug ingestion. HR was elevated for the ephedrine trials (E and C + E). RPE remained similar for all trails. Caffeine increased the epinephrine and norepinephrine response associated with exercise and also increased blood lactate, glucose, and glycerol levels. Ephedrine reduced the epinephrine response but increased dopamine and FFA levels.

CONCLUSION

The previously seen additive nature of E and C was not evident in this study, with the primary ergogenic effect being attributed to E.

Effects of a prolonged run on simple reaction time of well trained runners

The aim of the present study was to examine the effect of increased arousal induced by a prolonged exercise at ventilatory threshold simple reaction time performance performed during a running task. 11 well trained triathletes completed two testing sessions within a 2-wk. period. The first session was a protocol of VO2 max determination conducted on a treadmill. This protocol was used to assess the velocity associated with ventilatory threshold (vVvt). The second session was a 90-min. running test performed at vVvt. This last session was composed of five submaximal treadmill runs (10-min. long, 0% grade) separated by four overground runs (10-min.). Before, during each treadmill run, and after exercise, subjects performed three blocks of 20 simple reaction time. Furthermore, at the end of each overground run, perceived exertion (RPE) was recorded. Analysis showed a significant impairment in Simple RT performance during the first treadmill run only. After this first run a significant effect of exercise duration on Simple RT was observed. After 40-min. of exercise a significant improvement in reaction time during exercise was recorded, Furthermore, when Simple RT was recorded at rest, there was no difference pre-exercise and postexercise. These results suggest that a simple cognitive performance could be improved during exercise, despite the negative effect of the dual task. This improvement in reaction time could be explained mainly by an increase in arousal induced by a prolonged exercise.

Exercise and eating disorder symptoms among young females

BACKGROUND

In various settings, eating disorder symptoms have been linked to physical activity.

METHODS

A random sample of 726 females, aged 17-23 years, responded on a self-administered questionnaire. "High level exercisers" (HiEx) were defined as subjects exercising > or =6 sessions/week, > or =1 h/session. "Exercisers with obligatory attitudes" (ObEx) were those obtaining a result above the 95th percentile on a composite score of obligatory exercise items. These groups were compared to controls regarding composite scores of eating disorder symptoms and other symptoms.

RESULTS

While HiEx did not, ObEx obtained a significant result at the p<0.001 level regarding the score for body image problems, recurrent weight-reducing attempts, bingeing and post-prandial impulses to vomit. ObEx was also associated with symptoms related to stress and in particular with a high level of general activity coupled with perfectionistic ambitions.

CONCLUSIONS

Eating disorder symptoms in young females seem to be associated with obligatory attitudes to exercise rather than with exercise quantity.

Effects of phrenicotomy and exercise on hypoxia-induced changes in phrenic motor output

To investigate models of plasticity in respiratory motor output, we determined the effects of chronic unilateral phrenicotomy and/or exercise on time-dependent responses to episodic hypoxia in the contralateral phrenic nerve. Anesthetized (urethane), ventilated, and vagotomized rats were presented with three, 5-min episodes of isocapnic hypoxia (11% O(2)), separated by 5 min of hyperoxia (50% O(2)). Integrated phrenic (and hypoglossal) nerve discharge were recorded before and during each hypoxic episode, for the first 5 min after the first hypoxic episode, and at 30 and 60 min after the final episode. Of 36 rats, one-half were sedentary while the other one-half had free access to a running wheel; each of these groups was split into three subgroups: 1) unoperated, 2) chronic left phrenicotomy (27-37 days), and 3) sham operated. Neither unilateral phrenicotomy nor running wheel activity influenced the short-term hypoxic phrenic response (during hypoxia) or long-term facilitation (posthypoxia). Posthypoxia frequency decline was exaggerated in phrenicotomized-sedentary rats relative to unoperated-sedentary rats (change in burst frequency = -23+/-4 vs. -11 +/-5 bursts/min, respectively; 5 min posthypoxia; P<0.05), an effect that was eliminated by spontaneous exercise. The results indicate that neither voluntary running nor unilateral phrenicotomy has major effects on time-dependent hypoxic phrenic responses, with the exception of an unexpected effect of phrenicotomy on posthypoxia frequency decline in sedentary rats.

Alteration in dopamine metabolism in the thermoregulatory center of exercising rats

To examine the role of monoamines and amino acids in thermoregulation, we measured their concentrations in the preoptic area and anterior hypothalamus (PO/AH) in exercising rats, using an in vivo microdialysis technique. Body temperature (Tb) was monitored using a telemetry system. Tb increase by about 1.0 degrees C in the first 15 min of treadmill exercise (10 m/min; for 60 min), and was maintained thereafter at a steady high level possibly due to activation of the heat loss system. The levels of dopamine metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) in the PO/AH significantly increased during exercise. However, exercise did not induce an increase in the level of either serotonergic substances (5-hydroxytryptamine and 5-hydroxyindoleacetic acid) or amino acids (aspartate and glutamate). Our data indicate that dopamine breakdown processes in the PO/AH are activated during exercise. Dopamine in the PO/AH may be involved in the heat loss mechanisms for thermoregulation when Tb rises during exercise.

Facts and fallacies of purported ergogenic amino acid supplements

Although current research suggests that individuals involved in either high-intensity resistance or endurance exercise may have an increased need for dietary protein, the available research is either equivocal or negative relative to the ergogenic effects of supplementation with individual amino acids. Although some research suggests that the induction of hyperaminoacidemia via intravenous infusion of a balanced amino acid mixture may induce an increased muscle protein synthesis after exercise, no data support the finding that oral supplementation with amino acids, in contrast to dietary protein, as the source of amino acids is more effective. Some well-controlled studies suggest that aspartate salt supplementation may enhance endurance performance, but other studies do not, meriting additional research. Current data, including results for several well-controlled studies, indicated that supplementation with arginine, ornithine, or lysine, either separately or in combination, does not enhance the effect of exercise stimulation on either hGH or various measures of muscular strength or power in experienced weightlifters. Plasma levels of BCAA and tryptophan may play important roles in the cause of central fatigue during exercise, but the effects of BCAA or tryptophan supplementation do not seem to be effective ergogenics for endurance exercise performance, particularly when compared with carbohydrate supplementation, a more natural choice. Although glutamine supplementation may increase plasma glutamine levels, its effect on enhancement of the immune system and prevention of adverse effects of the overtraining syndrome are equivocal. Glycine, a precursor for creatine, does not seem to possess the ergogenic potential of creatine supplementation. Research with metabolic by-products of amino acid metabolism is in its infancy, and current research findings are equivocal relative to ergogenic applications. In general, physically active individuals are advised to obtain necessary amino acids through consumption of natural, high-quality protein foods.

Effects of tryptophan and/or acute running on extracellular 5-HT and 5-HIAA levels in the hippocampus of food-deprived rats

The present microdialysis study has examined whether exercise-elicited increases in brain tryptophan availability (and in turn 5-HT synthesis) alter 5-HT release in the hippocampus of food-deprived rats. To this end, we compared the respective effects of acute exercise, administration of tryptophan, and the combination of both treatments, upon extracellular 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels. All rats were trained to run on a treadmill before implantation of the microdialysis probe and 24 h of food deprivation. Acute exercise (12 m/min for 1 h) increased in a time-dependent manner extracellular 5-HT levels (maximal increase: 47%), these levels returning to their baseline levels within the first hour of the recovery period. Besides, exercise-induced increases in extracellular 5-HIAA levels did not reach significance. Acute administration of a tryptophan dose (50 mg/kg i.p.) that increased extracellular 5-HIAA (but not 5-HT) levels in fed rats, increased within 60 min extracellular 5-HT levels (maximal increase: 55%) in food-deprived rats. Whereas 5-HT levels returned toward their baseline levels within the 160 min that followed tryptophan administration, extracellular 5-HIAA levels rose throughout the experiment (maximal increase: 75%). Lastly, treatment with tryptophan (60 min beforehand) before acute exercise led to marked increases in extracellular 5-HT and 5-HIAA levels (maximal increases: 100% and 83%, respectively) throughout the 240 min that followed tryptophan administration. This study indicates that exercise stimulates 5-HT release in the hippocampus of fasted rats, and that a pretreatment with tryptophan (at a dose increasing extracellular 5-HT levels) amplifies exercise-induced 5-HT release.