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sábado, 7 de julho de 2018

Is caffeine consumption recommended for shooting sport athletes?

The following informative article has been prepared for the benefit of all athletes competing in shooting sport by Neda Nozari MD, member of the ISSF Medical Committee.
Caffeine is an odorless and bitter alkaloid which is found in tea, coffee, cola drinks and chocolate as well as a variety of prepackaged energy drinks. Caffeine has long been using as a stimulant to help with energy, focus and to stay awake. 
In January 2004, caffeine was one of several substances removed from the Prohibited Substance List by the World Anti‐Doping Agency. However, the supplement is still being closely monitored. Caffeine consumption is therefore permitted in sporting activities and competitions for the specific purposes of mild “performance enhancement” (1, 4).
What are some of the “performance enhancing” benefits of caffeine?Caffeine is widely used in various sports as an ergogenic aid. Some studies have demonstrated that caffeine supplementation improves power, speed, agility, attention, and reaction time in some sports. 
Unfortunately, there are limited published studies on caffeine effects in precision sport activities such as shooting sport.
Low (40 mg or 0.5 mg /kg) to moderate (300 mg or 4 mg/ kg) doses of caffeine improve alertness, attention and reaction time.  The effects on physical performance including time-to-exhaustion, time-trial, muscle strength and endurance are observed when ingesting doses of more than 200 mg (3 mg/ kg) (3). 
The following Table offers a summary of the cognitive and physical effects of caffeine. (e.g. Caffeine doses (mg/ kg body mass) associated with cognitive and physical effects in both rested and sleep deprived individuals (3).

How is caffeine absorbed?
It takes 15-45 minutes for caffeine metabolites levels to enter the blood stream and they reach their peak level usually after an hour (1). The absorption of caffeine is slower when is consumed with a meal but can be absorbed faster by chewing caffeine-containing gum which allows for rapid absorption through buccal tissue. Then, caffeine is distributed to all tissues very fast and passes easily through the blood-brain barrier for extending its effects. The mean half-life of caffeine in the circulation is nearly 3–5 hour. It means that can interact with many tissues for a long time (3). 
Of course, absorption is dependent upon how much caffeine is ingested. Table 2 offers an estimated caffeine content in common products (3).

What are some side-effects of caffeine?
All athletes should be informed that using caffeine can have its down side. When caffeine is ingested in excessive amounts for a long period, caffeine reaches to toxicity level (caffeinism), which can include the following negative side effects:
  • Central nervous system symptoms: Headache, light-headedness, anxiety, agitation, tremulousness, perioral and extremity tingling, confusion, psychosis, seizures. 
  • Cardiovascular symptoms: Palpitations, chest pain.
  • Gastrointestinal symptoms: Nausea and vomiting, abdominal pain, diarrhea, bowel incontinence, anorexia (2).
More specific to shooting, caffeine ingestion can induce arm and hand tremor and interfere with shooting performance.  Decreased shooting performance maybe due to palpitation, agitation and tremors. The shooter loses his / her concentration and steady in his / her shooting position. So, he/she likely fires a pendulum shot that increases the shooting error (1). In addition, caffeine can affect the nervous system and body temperature both which can affect shooting performance.
The results of one study on professional shooters have showed that:
  • Arm trembling was reported after a single cup of coffee containing 300–600 mg of caffeine. 
  • 300 mg of caffeine caused a marked increase in body sway 40 min after caffeine ingestion compared with a placebo trial (5) and had no effect on shooting accuracy and reaction time in traditional archery recurve bow discipline (8).
  • 5 mg/kg of caffeine caused a significant increase in blood pressure and heart rate but a significant decrease in shooting performance while taking 3 mg/kg of caffeine caused a significant increase in blood pressure and no effect on heart rate and shooting performance. 
The following provides some of the physiological side effects of caffeine on shooters.


Figure 1: Physiological effects of caffeine (6).
What quantity of intentional ingestion of caffeinated products is appropriate in shooting sport? 
Clinician agree that there is no health risk with consumption of up to 400 mg (∼5.5 mg/ kg for a 75 kg individual) of caffeine doses per day by healthy adults (3).
Studies on military soldiers have showed that caffeine can improve their shooting performances’ under conditions of sleep deprivation. But during conventional conditions, a low dose of caffeine had no effect on shooting performance and a medium dose of caffeine could worsen shooting performance (1, 7). 
The findings of other studies have showed also that caffeine had no ergogenic benefit with respect to reaction time, target tracking times and, particularly, performance scores. Treatment groups ingested 2 mg caffeine / kg of body weight and 4 mg caffeine / kg of body weight (2). Ingesting caffeine did not provide any positive increase in mental concentration or reducing perception of tiredness in this study (9).
The results of one study on caffeine effects on shooters performances’ is offered below. Shooters ingested Nescafe classic coffee as caffeine and Nescafe decaffeinated coffee as placebo (9).

Figure 2: Comparison Scores (9)

Figure 3: Comparison Scores between Rounds (1 round=10 shots) (9)

What is the take away?
Based on the above, the general conclusion is that caffeine may be of little performance enhancing benefit to shooting sport athletes.
It is recommended that shooters look for other useful ways of improving their performance before considering the use of caffeine products as a beneficial supplement to enhance their performance.  However, if shooters are interested in use of caffeine products during shooting training sessions, they should seek medical advice to ensure the level of consumption is safe and appropriate. (4).
1) Ebrahimi M, Pordanjani AF, Ahmadabadi F. The effect of different doses of caffeine on cardiovascular variables and shooting performance. Biomedical Human Kinetics. 2015; 7(1).
2) Yew D, Byrns CN. Caffeine toxicity. Medscape: News & Perspective. 2014 Mar 31.
3) McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine’s effects on cognitive, physical and occupational performance. Neuroscience & Biobehavioral Reviews. 2016 Dec 31; 71:294-312.
4) Share B, Sanders N, Kemp J. The Effects of Caffeine on Shooting Performance.
5) Share B, Sanders N, Kemp J. Caffeine and performance in clay target shooting. Journal of sports sciences. 2009 Apr 1; 27(6):661-6.
6) Messina G, Zannella C, Monda V, Dato A, Liccardo D, De Blasio S, Valenzano A, Moscatelli F, Messina A, Cibelli G, Monda M. The beneficial effects of coffee in human nutrition. Biology and Medicine. 2015 Oct 1; 7(4):1.

Posted by Thom Eriik Syrdahl
Source - ISSF Website
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