| Purpose:Exercise is stress. During the exercise, as the intensity and amount of stress getting higher, the catecholamines (NEã€E〠DA)concentration in blood get higher. Through the recruiting and coordinating of these neuroendocrine substances, human body systems can serve the exercise. When fatigue comes out, the catecholamines concentration would drop down, as a result, human body cannot keep exercise status or exercise quality which we called "stress fatigue". Many studies have shown that taking tyrosine can enhance the synthetization of catecholamines, exercise performances and cognition ability, but most studies only take one time before the exercise, furthermore, there’s rarely studies that have measured the catecholamines concentration directly. This study will observe the influence of2-week taking tyrosine on plasma catecholamines concentration and athletes’endurance performance.Method:Randomized, single-blind and crossover experiment design was used.15male athletes as subjects were randomly divided into two groups which were randomly given tyrosine and placebo for2weeks, before and after this term, they perform a exercise test(45min,70%Wmax constant intensity exercise+15min Time Trial). Before an immediately after the exercise, antecubital vein blood were drawn to measure catecholamines. After2-week washout period, both group received the opposite medicine and repeat the above-mentioned test routine.Results:(1) Before or after the2-week oral taking medicine, no significant difference was found between the two groups in the amount of workout during the Time Trial test.(2) Time-varying differences in blood lactate, heart rate and RPE scale were highly significant (p<0.01). Before taking, no significant difference were found between the two groups at all time phase of blood lactate concentration; the heart rate at recovery3min and recovery6min were found significant different between the groups (p<0.05).No significant difference was found between the two groups at all time phase of RPE scale. After intake, no significant difference was found between the two groups at all time phase of heart rate and RPE scale, blood lactate concentration for Tyrosine Group at post-3min was significant different from that of Placebo Group. Compared with that of pre-taking tyrosine, the RPE of Tyrosine Group at Ex-60min was significant lower(p<0.05).(3) Before the intake of tyrosine, no significant difference were found between the two groups for rest value of plasma adrenaline and noradrenaline but not for dopamine(p<0.05); After the intake, no significant difference were found between the two groups for rest value of plasma adrenaline and dopamine, but not for the plasma adrenaline. Compared with that of pre-taking tyrosine, the plasma noradrenaline level of Tyrosine Group was significantly lower(p<0.01).(4)Before the intake of tyrosine, no significant difference were found between the two groups at the time of pre-exercise or post-exercise for plasma adrenaline and noradrenaline, but not for the plasma dopamine (p<0.05); After the intake, no significant difference were found between the two groups at the time of pre-exercise and post-exercise for plasma adrenaline and dopamine, The plasma noradrenaline level of Tyrosine Group at the time of pre-exercise was significant lower than Placebo Group(p<0.05), there was no significant difference at the time of post-exercise. Compared with that of pre-taking tyrosine, the plasma noradrenaline level of Tyrosine Group both before and after the exercise was significantly lower(p<0.05).Conclusions:(1) Intake of tyrosine doesn’ t enhance endurance performance significantly.(2) Intake of tyrosine has no effect on plasma E and DA level at rest or E and DA during the one-off endurance exercise or plasma NE post exercise; But can reduce the plasma NE at rest and before exercise. |
