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Effects of a serotonin re-uptake inhibitor and oral amino acid supplementations on physical and mental performance as well as neuroendocrine variables were investigated. 10 male subjects cycled in four trials until exhaustion. Participants ingested a placebo in trial (T) I, 20 mg paroxetine in T II, 21 g branched-chain amino acids (BCAA) in I Ill and 20 g tyrosine (TYR) in T IV. Heart rate, capillary lactate, plasma insulin, free fatty acids, glucose, serotonin and fI-endorphine did not differ in trials. Plasma ammonia increments during exercise were higher in T Ill. Plasma BCAA in T Ill and plasma TYR in T IV were increased after 30 mm of exercise according to the supplemented substances. In contrast to all other trials, the ratio of plasma free TRP/BCAA did not increase in T Ill. Plasma TYR/BCAA was augmented in I IV and decreased in T III after 30 mm of exercise, whereas it did not change in I I and II. Plasma prolactin (PRL), growth hormone, cortisol, adrenocorticotropic hormone, norepinephrine and epinephrine increased during all trials. Plasma PRL increments were higher in I IV. Exhaustion was reached earlier in I II. No significant differences were found between other trials. Drive during psychometric testing subsequent to exercise was improved in I III and IV. The results indicate that fatigue during endurance exercise was increased by pharmacological augmentation of the brain serotonergic activity. However, a reduction of 5-HI synthesis via BCAA supplementation did not affect physical fatigue. TYR administration did not alter physical performance either although plasma PRI increments suggest that changes in the monoaminergic system were induced. Precaution is necessary before assuming an ergogenic value of amino acids.

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The goal of this study was to evaluate the physiological responses during incremental field tests (FT) in nordic walking (NW), walking (W) and jogging (J). Fifteen healthy middle-aged women participated in three FT. Heart rate (HR) and oxygen uptake (V(O)(2)) were monitored continuously by portable analyzers. Capillary blood lactate (La) was analyzed at rest and after every stage of the FT. The disciplines showed differences during stage 1.8 and 2.1 m s(-1) for V(O)(2) between NW and W (P < 0.05). The maximum value was measured at 1.8 m s(-1 )(8%). In accordance with La, V(CO)(2) was higher in NW compared with W during all stages (P < 0.05) and even higher in NW compared with J during 2.1 and 2.4 m s(-1). While there were higher HR for NW and W at 2.4 m s(-1) than in J (P < 0.01), there were increases for HR at fixed values of 2 (La2) and 4 (La4) mmol l(-1 )lactate for J compared with NW and W (P < 0.01). Although the speed of NW was slower than that of W at La2 and La4 (P < 0.05), there were no differences for the HR and the V(O)(2) Our results demonstrate that metabolic responses are a helpful instrument to assess the intensity during bipedal exercise. As NW speed at submaximal lactate levels is lower than in W and J, W and J test measures of HR and V(O)(2) are not suitable for NW training recommendations. Additionally, the V(O)(2) formed by performing NW is not as high as previously reported.