The effects of caffeine consumption on
Positive or Negative?
Introduction: Caffeine is odorless
and a bitter alkaloid which is found in tea, coffee, cola drinks,
and chocolate (1, 2). See the Table 1 for
caffeine equivalents in common products (3).
Table 1. Estimated caffeine content in common
The amount of its metabolites level usually increases in the
blood within 15–45 minutes after caffeine intake, and reaches to the peak level
after an hour (1).
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 be interacted with many tissues for a long time (3).
January 2004, caffeine was one of several substances removed from the
Prohibited Substance List by the World Anti?Doping
Agency, the supplement is still being closely monitored in doping tests. This new
strategy permits caffeine consumption in sporting activities and competitions
for the specific purposes of performance enhancement (1, 4).
(40 mg or 0.5 mg /kg) to moderate (300 mg or 4 mg/ kg) doses of caffeine
improve alertness, attention and reaction time, but effects are less on memory
and higher-order executive function, such as judgment and decision making. Low
and moderate doses of caffeine don’t not alter significantly sensory functions
including vision or hearing. Effects on physical performance including
time-to-exhaustion, time-trial, muscle strength and endurance are observed by
dose of more than 200 mg (3 mg/ kg) (3). See the Table 2 for caffeine doses
associated with cognitive and physical effects.
Table 2. Caffeine doses (mg/ kg body mass) associated with cognitive and
physical effects in both rested and sleep deprived individuals (3).
studies have demonstrated that caffeine supplementation improves power, speed,
agility, attention, and reaction time in some sports. Now, caffeine is widely
used in various sports as an ergogenic aid. Unfortunately, there are limited
published studies on caffeine effects in precision sport activities such as
of caffeine supplementations
side-effects questionnaire of caffeine supplementation in shooters revealed
that commonly associated side-effects such as headache, anxiety, and tremor.
Caffeine administration can induce arm and hand tremor and interfere with
shooting performance. Arm trembling was reported after a single cup of coffee including
300–600 mg of caffeine. And also, 300 mg of caffeine caused a marked increase
in body sway 40 min after caffeine ingestion compared with a placebo trial (5).
Figure 1: Physiological effects of caffeine (6).
caffeine ingested in excessive amounts for a long period, caffeine reaches to
toxicity level (caffeinism), which including below symptoms:
system symptoms: Headache, lightheadedness, anxiety, agitation, tremulousness,
perioral and extremity tingling, confusion, psychosis, seizures.
Palpitations, chest pain.
symptoms: Nausea and vomiting, abdominal pain, diarrhea, bowel incontinence,
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).
quantity of intentional ingestion of caffeinated products is safe and
appropriate for the shooting sport?
The results of one study on professional shooters have showed
that taking 5 mg/kg of caffeine caused a significant increase in blood pressure,
a significant increase in heart rate but a significant decrease in shooting performance.
Moreover, taking 3 mg/kg of caffeine caused a significant increase in blood pressure.
But this amount of caffeine had no significant effect on the heart rate and
shooting performance. Decreased of shooting performance maybe due to palpitation,
agitation and tremors in body of shooter. 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
effect on the nervous system and body temperature as effector factors .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 worse 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 in the Olympic Double Trap ) The treatment groups ingested 2 mg caffeine / kg of
body weight and 4 mg caffeine / kg of body weight(
(2). Consumption of 300 mg caffeine provided no performance benefit to shooting
accuracy and reaction time in traditional archery recurve bow discipline (8).
can see the results of one study on caffeine effects on shooters performances’
in below. Shooters ingested Nescafe classic coffee as caffeine and Nescafe
decaffeinated coffee as placebo (9).
Figure 2: Comparison Scores between Treatments (9).
Figure 3: Comparison Scores between Rounds (1 round=10 shots) (9)
didn’t show any effect on increasing mental concentration and reducing
perception of tiredness in this study (9).
is recommended that shooters look for other useful ways for improving their
performances’ before considering the use of caffeine products as a supplementation.
However, if shooters are interested in use of caffeine products during shooting
training sessions, please request medical supervision to ensure the level of
consumption is safe and appropriate. Some athletes experience a perceived or
psychological benefit from the ingestion of caffeine products. This means some
individuals are ‘caffeine responders’, while others are ‘no responders’ with
caffeine consumption. For both of them, we advise to follow a medical consult
before consumption (4).