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L-Tyrosine - an overlooked supplement?
AST Sports Science
"Fatigue makes cowards of us all" chanted the legendary coach Vince Lombardi. That may well be true, but central nervous system (CNS) fatigue is a bodybuilder's worst enemy. Optimal function of the CNS is vital at it enables the recruitment of all fibers required to lift maximal weights, and ensure an effective muscle growth stimulus from training. Therefore, bodybuilders must avoid training with CNS fatigue at all costs.
An increased concentration of brain serotonin during exercise has been implicated as an important factor in the onset of CNS fatigue [3]. Supplementing with the amino acid L-Tyrosine may prove to be an effective supplement that reduces the build up serotonin in the brain and delays CNS fatigue.
What L-tyrosine can do for you . . .
In the brain, serotonin and dopamine are chemicals that produce opposite effects. High serotonin levels (or an increased serotonin to dopamine ratio) produce a feeling of deep relaxation and fatigue [3]. Whereas higher dopamine concentrations produce a sense of mental alertness, sharpness and well being and enhance performance[1,4].
During exercise one of the biggest contributors to the feeling of fatigue is a build up of serotonin in the brain [3,4]. However, if an athlete can decrease this ratio of serotonin to dopamine by either decreasing serotonin levels or increasing dopamine levels the feeling of fatigue may be alleviated [5] As most athletes know, if you feel good, you're more likely to push harder and perform better.
While the amino acid L-tryptophan increases serotonin levels, L-tyrosine is the major precursor of dopamine [6]. Some investigations have shown that L-tyrosine administration increases dopamine synthesis and brain concentrations [5,7,8], whereas other studies have shown that tyrosine administration improves mood and sense of well-being in human subjects that are under stress [9, 10]. These results raise the possibility that supplementation with L-tyrosine during exercise could offset feelings of fatigue and enhance performance. A recent study looked at the effects of using L-tyrosine during exercise.
L-tyrosine supplementation and exercise performance . . .
Using nine competitive cyclists, researchers from Brigham Young University examined the performance effects of tyrosine supplementation with and without carbohydrates [11]. The cyclists performed four separate trials after taking a dose of tyrosine, a tyrosine/carbohydrate combination, a carbohydrate-only supplement and a placebo supplement. On each occasion, the cyclists were asked to pedal at 70% of their maximal oxygen uptake for 90 minutes followed immediately by a time trail performance test.
Sixty minutes before each exercise bout, each subject consumed one of the supplements in a random order, in a double blind fashion. The amount of carbohydrate used was (polydextrose 70 grams/l), and the dose of L-tyrosine used was 25mg per kg body wt. The carbohydrate plus L-tyrosine combination combined both amounts.
The carbohydrate/tyrosine supplement enabled the cyclists to finish the time trial the fastest (26.11 minutes). However, this was closely followed by the carb-only supplement (27.17minutes), which were followed by the tyrosine-only supplement (32.64 minutes) followed by the placebo (34.44 minutes).
The statistical findings revealed no difference between any of the groups, this suggested that tyrosine supplementation did not enhance performance. However, a closer look at the data shows that the plasma tyrosine-to-free tryptophan ratio was significantly higher after the cyclists consumed the tyrosine supplements. This is important. It means the supplementation worked to increase the ratio of tyrosine to tryptophan in the blood. Also, the raw data shows that six of the nine subjects in the carbohydrate/tryrosine trial finished faster than in all other trails, where as the in the carb only trial, only three of the nine finished faster. The small number of participants in this study may not have statistically enabled the positive effects of taking tyrosine to shine through.
How L-Tyrosine can work for you . . .
The evidence on L-tyrosine's ability to increase dopamine concentrations and improve mood and well-being in humans is substantial. Supplementing with tyrosine increases circulating levels of this amino acid. Because tyrosine competes for transport across the blood brain barrier with tryptophan, increasing blood tyrosine levels via supplementation could lower the brain serotonin/dopamine ratio and improve your attitude and focus during a workout, particularly the later stages.
Paul Delia was the first to realize the value of L-tyrosine and incorporate this amino acid into Dymetadrine Xtreme to enhance and prolong the potent effects of the ephedra/caffeine/willow bark stack. However, to obtain the effects I've previously described and possibly delay fatigue, bodybuilders may need to use gram dosages.
If bodybuilders want to experiment with this amino acid to improve performance, here is what I recommend. Take your serving of Creatine HSC and VP2 Whey Isolate 30 minutes before training (as your driving to the gym). Then take a 2-3 gram dose of L-tyrosine with some water just before you start your warm up sets. Taken in this way, an effective amount of tyrosine will get into circulation at the right time to reduce the serotonin dopamine ratio and hopefully delay fatigue.
Supplementing with tyrosine would be an effective, safe strategy for drug tested bodybuilders, tyrosine is not on any banned list. Particularly, bodybuilders that train twice a day and restrict calorie intake would probably receive a nice little boost from strategic incorporation of L-tyrosine before a workout.v If you perform a weight training session in the early am and then head back to the gym in the afternoon to grind out a Max-OT cardio session, I'd recommend supplementing with L-tyrosine during this second intense workout of the day. As your contest draws nearer and energy depletion becomes more evident, you may want to try L-tyrosine supplementation before both daily workouts. Sometimes that 16-minute Max-OT cardio session can be the longest 16-minutes of your life, L-tyrosine supplementation may help it become a little easier.
References:
1. Chaouloff, F, Laude D, and Elghozi JL. Physical exercise: evidence for differential consequences of tryptophan on serotonin synthesis and metabolism in central serotonergic cell bodies and terminals. J Neural Transm 78: 121-130, 1989.
2. Bailey, SP, Davis JM, and Ahlborn EN. Effect of increased brain serotonergic activity on endurance performance in the rat. Acta Physiol Scand 145: 75-76, 1992.
3. Romanowski, W, and Grabiec S. The role of serotonin in the mechanism of central fatigue. Acta Physiol Pol 25: 127-134, 1974.
4. Davis, JM, and Bailey SP. Possible mechanisms of central nervous system fatigue during exercise. Med Sci Sports Exerc 29: 45-57, 1997.
5. Badawy, AA-B, and Williams DL. Enhancement of rat brain catecholamine synthesis by administration of small doses of tyrosine and evidence for substrate inhibition of tyrosine hydroxylase activity by large doses of the amino acid. Biochem J 206: 165-168, 1982.
6. Wurtman, RJ, and Lewis MC. Exercise, plasma composition and neurotransmission. In: Advances in Nutrition and Top Sport, edited by Brouns F.. Basel: Karger, 1991, vol. 32, p. 94-109.
7. During, MJ, Acworth IN, and Wurtman RJ. Dopamine release in rat striatum: physiological coupling to tyrosine supply. J Neurochem 52: 1449-1454, 1989.
8. During, MJ, Acworth IN, and Wurtman RJ. Effects of systemic L-tyrosine on dopamine release from rat corpus striatum and nucleus accumbens. Brain Res 452: 378-380, 1988.
9. Lieberman, HR, Corkin S, Spring BJ, Wurtman RJ, and Growden JH. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 42: 366-370, 1985.
10. Banderet, LE, and Lieberman HR. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Res Bull 22: 759-762, 1989.
11. Chinevere TD, Sawyer RD, Creer AR, Conlee RK, and Parcell AC. Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance. J Appl Physiol 93: 1590-1597, 2002.
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