Caffeine and its ergogenic effect in sport (second part)
259
Arch Med Deporte 2016;33(4):259-266
Review
Summary
The eects of caeine on the human body have been studied for some time and much is now known about its characteristics.
In the sports world, caeine is one of the most popular ergogenic aids and is widely used by coaches and athletes. Given its
importance, in this paper we analyze the ergogenic eects of caeine on athletic performance and related actions, through
a review of the latest scientic literature. We selected studies that included well-trained subjects performing a physical acti-
vity that reects current practices in sport. Close attention was given to the methodology used, including the dose, timing
and administration method of the caeine, with the aim of establishing an updated guide to caeine as an ergogenic aid in
sport. The results show there are a variety of studies that have investigated the eects of caeine on exercise using dierent
methodologies, making it impossible to reach a general assumption. Nevertheless, we are able to draw valuable conclusions
including the clear trend towards the eectiveness of caeine as an ergogenic aid in certain situations, new ndings that deal
with the use of caeine on consecutive days of physical activity, the best time of day to take the substance, the strategic ma-
nagement of caeine to counteract sleep deprivation, and in what direction the latest research trends in this eld are moving.
Key words:
Caeine. Ergogenic eects.
Sports. Aerobic exercise.
Resumen
Los efectos de la cafeína sobre el organismo humano han sido estudiados desde hace tiempo y, a día de hoy, ya conocemos
gran parte de sus características. En el mundo del deporte, la cafeína es una de las ayudas ergogénicas más populares y em-
pleadas por entrenadores y atletas. Debido a su importancia, en este trabajo nos hemos propuesto el objetivo de analizar los
efectos ergogénicos de la cafeína sobre el rendimiento deportivo y todo lo que rodea a esta acción, a través de una revisión
de la literatura cientíca más actual. Hemos seleccionado aquellos estudios que incluyeran sujetos bien entrenados realizando
una actividad física que reejara las actuales prácticas en el deporte, prestando mucha atención a la metodología empleada,
esto es la dosis, el momento y la forma de administración de la cafeína, para conseguir alcanzar nuestra meta de constituir
una guía actualizada sobre todo lo que rodea a la cafeína como ayuda ergogénica en el deporte. Los resultados obtenidos nos
han mostrado una gran variedad de estudios que han investigado acerca de la cafeína y el ejercicio físico siguiendo diferentes
metodologías, lo que provoca una imposibilidad de generalizar sobre el asunto. Sin embargo, hemos podido extraer valiosas
conclusiones como la clara tendencia hacia la efectividad de la cafeína como ayuda ergogénica en situaciones determinadas,
nuevos hallazgos que tienen que ver con el uso de la cafeína en días consecutivos de actividad física, el mejor momento del
día para el consumo de la sustancia o la administración estratégica de cafeína para contrarrestar la falta de sueño, y hacia
dónde se dirigen las últimas tendencias en investigación dentro de la materia.
Palabras clave:
Cafeína. Efectos ergogénicos.
Deportes. Ejercicio aeróbico.
Received: 18.02.2016
Accepted: 19.04.2016
Caffeine and its ergogenic effect in sport (second part)
Antonio García Moreno
Universidad Pablo de Olavide. Sevilla
La cafeína y su efecto ergogénico en el deporte (segunda parte)
Correspondence: Antonio García Moreno
E-mail: an[email protected]
Antonio García Moreno,
et al.
260
Arch Med Deporte 2016;33(4):259-266
The ergogenic effect of caffeine on anaerobic exercise
High-intensity, short-duration exercise
Research
41
assessed the performance of racing cyclists completing
a 1-km time trial on cycloergometers. The subjects took a tablet with
5 mg/kg of caeine or placebo dissolved in an aqueous solution 75
minutes beforehand. The results showed that taking the caeine cut
the time it took to nish the trial and led to a higher average speed,
higher average power and greater peak power compared to the placebo.
Caeine in tablet form administered to trained subjects accustomed
to the protocol of the activity improves performance in high-intensity,
short-duration exercise.
As for sprint capability, Graham-Paulson et al
42
conducted research
on 12 trained wheelchair athletes who completed a trial consisting of
four 4-minute pushes and three sets of three 20-m sprints, each sepa-
rated by 4 minutes of rest. In another study by Kopec et al
43
, 11 athletes
did six 20-metre sprints at the beginning, in the middle and at the end
of a 60-minute simulated team-sport circuit. The wheelchair athletes
who took 4 mg/kg of caeine 70 minutes before the trial registered
better times in the 20-metre sprints and improved their maximal-push
performance compared to those who took the placebo. In the other
study, the athletes who took capsules with 6mg/kg of caeine 60 mi-
nutes before the trial improved their sprint capability both when fresh
and when tired.
Another study
44
measured the sprint capability of trained cyclists
by means of a trial on cycloergometers consisting of four 5-minute sets
of ve maximal sprints lasting 30 seconds with ve 30-second active
recovery periods. The cyclists chewed gum with 240 mg of caeine for
5 minutes at the end of the second set of tests. The caeine reduced the
subjects’ fatigue during the sprints, which may imply improvements in
high-intensity performance in cyclists. So, the most recent studies show
that caeine has an ergogenic eect on performance in high-intensity,
short-duration exercise.
Exercises based on strength and power
Most of the studies investigating the ergogenic eect of caeine
on exercises based on strength and power included in this review em-
ployed similar methodologies. One example is provided by 3 studies on
resistance-trained athletes who were administered 6 mg/kg of caeine
in capsule form 60 minutes prior to sessions in test conditions. In the
rst study
45
, the subjects performed a maximal leg-press test, while the
participants in the second
46
completed leg-press and arm-curl tests with
a 12-repetition maximum (RM) load to achieve the greatest number
of reps to failure. In both studies, caeine improved the maximum
isometric voluntary contraction of knee extensors
45
and increased the
total number of leg-press and arm-curl reps
46
, providing foundations
for improvement in the performance of exercises involving resistance.
However, in the third study
8
, in which the athletes performed 4 sets of as
many bench-press and shoulder-press reps as they could at 70% of 1RM,
and as many leg-press and bar-row reps as they could at 80% of 1RM, the
caeine had no ergogenic eect on performance. The study suggests
that all the participants were regular caeine consumers, which may
have altered their response to caeine. Nevertheless, the number of
leg-press repetitions was greater after caeine intake, although the
scale of this improvement was small and no signicant dierences were
observed in the exercises for the upper part of the body. Consequently,
two studies point towards improvements in strength and power per-
formance after taking 6 mg/kg of caeine 1 hour before exercise, while
another study shows no ergogenic eect under the same conditions.
The habituation of the subjects to caeine in the study by Astorino et
al
8
may go some way towards explaining the lack of benecial eects,
but the subjects in the study by Hudson et al
46
were also regular caeine
users (daily consumption of 100-400 mg) and their performance impro-
ved. In Chen et al’s trial
45
, the subjects were not regular consumers of
caeine (weekly consumption of less than 200 mg) and they beneted
from the eect of the substance in their anaerobic tests. With the data
available, it is dicult to pinpoint why the studies gave the results that
they did because the tests were conducted in very similar conditions
and threw up very dierent results. Perhaps the answer lies in individual
physiological and metabolic responses to caeine. Be that as it may, it
is necessary to place greater emphasis on and study the physiological
and metabolic parameters that these studies ignored and which may
explain the results obtained.
In 3 other studies conducted along similar lines to the ones just
described, well trained athletes with experience in strength training
took 5 mg/kg of caeine diluted in an aqueous solution 1 hour before
exercise
6,7,47
. The studies measured the number of bench-press, leg-
press, deadlift and horizontal-row repetitions to failure. In all three
studies, the subjects increased the number of repetitions completed
in each exercise after caeine intake and experienced a signicant
reduction in the perceived exertion and muscle soreness rating. In Da
Silva et al’s study
6
, the participants also showed a greater readiness to
invest in mental eort. In view of these results, we can conclude that
the intake of 5 mg/kg of caeine 1 hour before exercise can improve
the strength performance of trained athletes, possibly due to a greater
readiness to make mental eort and a reduction in perceived muscle
soreness and exertion.
Two other studies investigating strength and power performance
showed benecial results after the intake of caeine. In the study by
Woolf et al
9,
18 highly trained men ingested a multi-ingredient shake
with 5 mg/kg of caeine 1 hour before exercise. In the trial, the sub-
jects performed a leg-press test and a bench-press test in which the
repetitions and total weight were measured, followed by a 30-second
Wingate anaerobic test on cycloergometer in which power output was
measured. The intake of caeine signicantly increased the total weight
lifted in the bench-press test and the maximum power produced in
the Wingate test compared to the placebo, while no dierences were
registered in the leg-press test. Glaister et al’s study
48
used a protocol
consisting of sets of 6-second maximal sprints one hour after taking
Caffeine and its ergogenic effect in sport (second part)
261
Arch Med Deporte 2016;33(4):259-266
a capsule with 5 mg/kg of caeine. The caeine supplement led to
greater maximum anaerobic power output in comparison with the
placebo. These studies demonstrate that doses of 5 mg/kg of caeine
can increase muscle power and strength in the upper body of trained
athletes.
After this look at the studies of recent years, we can say that the use
of caeine supplements by trained athletes accustomed to anaerobic
exercise may be eective when it comes to achieving improvements
in performance. We have also found, however, that, when certain pa-
rameters, such as habituation to caeine and individual responses to
the substance, are not controlled, then the desired eect may not be
achieved. Nevertheless, these studies reveal very important ndings
within the eld, because from now on, research can develop protocols
taking into account the necessary indications in order to cater for ca-
eine as an important factor in anaerobic performance.
The methodology of research on caffeine and sport
Doses of caeine
We have seen a wide range of doses administered; from small to
more moderate amounts of between 1.5 and 6 mg/kg, to absolute doses,
classied as those between 80 mg and 300 mg. Small doses have proven
sucient to produce signicant improvements in performance, as in
the case of the study by Lane et al
49
, in which a dose of 3 mg/kg impro-
ved power in competitive cyclists and triathletes during high-intensity
interval training. Absolute doses are less commonly used because each
individual has a dierent body weight, which means that the caeine-
subject relationship varies. However, when doses involving more or less
standard quantities are used, similar eects may be achieved among
dierent participants, as the study by Beck et al
50
, in which 37 trained
athletes improved their upper-body strength with a supplement of 200
mg caeine, goes to show.
The most significant study was conducted with trained athletes
51
using 3 different doses of 3, 6 and 9 mg/kg to evaluate the effects
of caffeine on neuromuscular tests consisting of bench-press and
full-squat exercises against incremental loads (25%, 50%, 75% and
90%1RM), followed by an inertial load test on cycloergometer. The
results revealed that mean propulsive velocity at light loads (25%
and 50% 1RM) increased significantly for all caffeine doses compared
to the placebo. At the medium load (75%), the 3-mg/kg dose did
not improve muscle velocity or power in the bench-press and full-
squat exercises. The 9-mg/kg dose improved velocity in the bench
press and power in the full squat with the heaviest load (90%). There
were no significant differences between the placebo and the 3- and
6-mg/kg doses in the cycloergometer test, while the 9-mg/kg dose
improved maximum power output. The 9-mg/kg dose increased the
frequency of adverse side effects dramatically. So we can conclude
that the caffeine dose required for an improvement in neuromuscu-
lar performance depends on the magnitude of the load employed.
A dose of 3 mg/kg of caffeine is enough to improve high-velocity
muscle actions against low loads, whereas a higher caffeine dose
(9 mg/kg) is necessary against greater loads, despite the appearance
of adverse side eects.
The timing of caeine administration
According to Ryan et al
52
, the organism completely absorbs caei-
ne within approximately one hour following ingestion, although this
may vary depending on the dose and the method of consumption.
After the oral intake of caeine, the concentration of the substance in
plasma increases in proportion to the dose and peak levels in plasma
can be seen between 15 and 120 minutes later. Researchers, therefore,
normally administer caeine doses (in capsule or drink form) 1 hour
before exercise in their studies to ensure maximum concentrations in
plasma during the activity
52
.
However, a lot of studies have investigated the eect of caeine
by applying it more than one hour before, less than one hour befo-
re and even during exercise. A study conducted by Marriott et al
53
administered a capsule with 6 mg/kg of caeine 70 minutes before
high-intensity intermittent exercise, leading to improvements in the
performance of the participants. In another study carried out with
racing cyclists, caeine was consumed 20 minutes before a 40-km
time trial on cycloergometer and benecial eects on performance
after taking the supplement were observed
54
. In a recent study
55
, ca-
eine gum was given to cyclists at kilometre 10 of a 30-km trial which
included a 200-metre maximal sprint every 10 km. The participants
had to chew the gum for 5 minutes and then remove it. The results
showed an improvement in the power of the sprint in the last 10 km,
leading to the conclusion that the ergogenic eect of caeine gum
appears 20 minutes after consumption.
Meanwhile, Cooper et al
56
designed an experiment with trained
athletes who completed a four-block intermittent sprint test. The sub-
jects took a carbohydrate gel with caeine 60 minutes before exercise,
just before starting and at the end of the second block, and the results
showed that the gel was eective at reducing fatigue and perceived
exertion, and contributed to maintaining high levels of glucose in the
nal stage of the exercise. Skinner et al
57
conducted very interesting
research in which performance was measured in a 40-km time trial on
cycloergometer following consumption of a caeine capsule 1 hour
before exercise compared to starting exercise with the level of caeine
in blood serum at its peak, which turned out to be between 120 and
150 minutes after intake. The caeine consumed one hour before the
trial signicantly enhanced the athletes’ performance in the 40-km time
trial compared to the caeine at its maximum concentration in serum
on starting the activity, the maximum concentration in blood showing
no ergogenic eect.
One of the most significant studies in this field was that con-
ducted by Ryan et al
52
, in which the subjects were given chewing
gum with 3 mg/kg of caffeine 120, 60 or 5 minutes before a cycling
trial lasting approximately one hour. The caffeine chewing-gum
supplement improved the performance of the cyclists when given
immediately before exercise (5 minutes earlier), but no beneficial
Antonio García Moreno,
et al.
262
Arch Med Deporte 2016;33(4):259-266
effects on performance were appreciated when it was consumed 1
or 2 hours beforehand.
Therefore, we can see that, depending on the dose and form of
delivery, the ergogenic eect of caeine can aect performance re-
gardless of when it is applied.
Methods of caeine administration
Caeine can be administered in many dierent ways, but the most
common way to take caeine is through coee. One study
58
compa-
red the eects of caeine administered through coee with caeine
anhydrous diluted in water at a dose of 5 mg/kg. The results showed
that both caeine anhydrous and coee consumed one hour before
exercise could improve the performance of trained cyclists in aerobic
cycling activities.
Due to the growing popularity of energy drinks, laboratory tests
have started to use energy drinks on an increasing basis to evaluate
the eects of caeine on sports performance. A very recent study59
compared the ergogenic eect of caeine on trained cyclists by means
of both an energy drink (Red Bull) and capsules containing 3 mg/kg of
caeine. The results showed that caeine consumed both through an
energy drink and through capsules improves performance in cycling
endurance tests.
The results seen in this review would seem to indicate that the way
in which caeine is taken can inuence the speed at which the organism
absorbs the substance, but that, regardless of the way it is taken, the
eect on performance is the same when the dose is the same.
The latest trends in research on caffeine and sport
The administration of caeine in alternative forms
More and more research is focusing on the ergogenic eect of
caeine taken in alternative ways. Paton et al
55
and Scott et al
11
used
caeine chewing gum and caeinated isotonic carbohydrate gel,
respectively, to demonstrate the eectiveness of caeine at improving
performance. Another study
60
used a carbohydrate and electrolyte
solution with 5.3 mg/kg of caeine to measure the ergogenic eect
of the substance on endurance in trained cyclists; the results revealed
that the caeinated solution was eective at providing energy during
prolonged exercise, improving performance and reducing muscle
fatigue in the cyclists.
Two innovative pieces of research in the eld were conducted by
Doering et al
61
, who exposed the subjects to mouthwash with 35 mg of
caeine 8 times during a 60-minute cycling activity, and by Schubert et
al
62
, who gave the participants a 59-millilitre “shot” of 2 dierent energy
drinks with caeine before a 5-km treadmill test. Neither of the studies,
however, revealed any ergogenic eects of caeine on performance
in the tests or dierences in physiological or perceptive variables
compared with the placebo. This lack of benets was associated with
the low doses of caeine employed. Nevertheless, there is a focus in
current research on new ways of using caeine, such as energy drinks,
chewing gum, gels or carbohydrate and electrolyte solutions
11,55,59,60
,
which are dierent to the traditional ones, such as coee or capsules,
and good results are being obtained.
The eect of caeine on performance in adverse
environmental conditions
Exercise is tolerated less in hot environments than it is in cool ones,
and several studies have investigated whether caeine can counteract
exercise fatigue induced by heat
63
. One study reports that a dose of
6 mg/kg of caeine did not produce any ergogenic eect on aerobic
performance in a hot environment
64
, while 3 other studies suggest that
doses of 3 and 6 mg/kg of caeine are eective when it comes to pro-
viding benets in endurance exercises carried out at high temperatures
of between 33°C and 36°C
63,65,66
.
Bearing in mind that the subjects in the study by Roelands et al
64
responded very dierently to the caeine and that their internal tem-
perature increased signicantly during the exercise after consuming
caeine compared to the placebo, which may have counteracted
the ergogenic eects of the substance, we could say that caeine, in
doses of 3 to 6 mg/kg, proves an eective supplement to compensate
performance diminished by high temperatures.
The eect of caeine on performance in sports people who
are habitual consumers as opposed to those not habituated
to the substance
Several studies associate the level of habituation to caffeine of
participants to an absence of beneficial effects on physical activity.
In research conducted by Desbrow et al
67
, low doses of caffeine did
not improve the performance of trained subjects during prolonged
exercise, possibly due to their habituation to the substance. Other
studies attribute the participants’ low level of caffeine consumption
to a lack of improvement in their performance, the adverse reac-
tions induced by caffeine in the subjects possibly counteracting its
ergogenic effect
68,69
.
However, one study conducted on cyclists and triathletes who
were habitual caeine consumers did note improvements in perfor-
mance with low doses
70
. Meanwhile another study carried out on
athletes with dierent levels of caeine consumption only observed
improvements in strength performance in those participants less
accustomed to the substance, who also registered more intense
emotional responses
71
.
It can be concluded, therefore, that the subjects’ level of caeine
consumption should be controlled and their response to the substance
should be observed more strictly in future research. However, Gliottoni
et al
72
did try to clarify the matter somewhat when they conducted
research on 24 university athletes, split into two groups: small caeine
consumers, who took 100 mg or less a day, and major caeine consu-
mers who ingested 400 mg or more a day. The results showed similar
work levels during exercise between the two groups after taking 5 mg/
kg of caeine, which caused a moderate hypoalgesic eect during
Caffeine and its ergogenic effect in sport (second part)
263
Arch Med Deporte 2016;33(4):259-266
high-intensity activity in both groups. So, according to Gliottoni et al
72
,
the level of habituation to the substance does not aect the scale of
the ergogenic eect of caeine on physical performance.
The eect of caeine on reaction time
Two studies used a reactive agility test to measure the reaction time
of trained athletes after taking caeine
73,74
. In both studies, 6 mg/kg of
caeine was administered to the subjects in capsule form 60 minutes
before the trial, with the dierence that Duvnjak-Zaknich et al’s research
74
evaluated the subjects in conditions of fatigue, while Jordan et al’s
73
did
so when they were fresh. In the reactive agility test, the participants had
to react as quickly as possible to a stimulus indicating one side (left or
right) to which they had to make a 5-metre sprint. The results of both
studies showed better reaction times after taking caeine compared to
the placebo, so caeine intake can be understood to enhance reactive
agility performance no matter whether athletes are fresh or tired.
The eect of caeine on athletes’ cognitive and perceptual
dimensions
Many studies have investigated the eectiveness of caeine on
cognitive function and perception during sports activity, pointing
towards the potential of caeine in this eld. Hogervorst et al
75
suggest
that a low dose of caeine improves cognitive performance during
and after vigorous exercise. The subjects, trained cyclists, ingested a
carbohydrate energy bar with 100 mg of caeine just before starting
and at minutes 55 and 115 of a 3-hour cycloergometer exercise at 60%
VO
2
max, followed by a test to exhaustion at 75% VO
2
max. Cognitive
function measures (Stroop and Rapid Visual Information Processing
tests) were taken before exercise and while cycling after 70 and 140
minutes of exercise, and again 5 minutes after completing the time
to exhaustion ride. In the results obtained, the participants comple-
ted the complex information processing tests signicantly faster and
took longer to nish the time to exhaustion test after taking caeine
compared to the placebo. So caeine in a performance bar can
signicantly improve endurance performance and cognitive ability
during and after prolonged exercise. These eects may be salient
for performance in sports and activities in which concentration and
decision making play a major role.
In the same line of research, Stevenson et al
76
showed how caeine
not only improved the performance of experienced golfers during
an 18-hole round, but also managed to increase their alertness and
positively aect their mood compared to the placebo. These results
support the eects observed after a moderate intake of caeine of
between 5 and 6 mg/kg in two studies which measured performance
and mood in athletes
77,78
. In both studies, the participants enjoyed a
more positive subjective experience and were in a more favourable
mood during exercise after taking caeine than after taking the pla-
cebo. The benecial eects of caeine on the aective dimensions
of athletes during exercise may prove to be of great interest both to
research and to sports people themselves, since these dimensions
play an important role in tasks involving persistence and eort, and,
therefore, directly inuence performance in training and competitions.
The side eects of caeine consumption
The eects of caeine intake have been widely reported, their being
understood as inherent to consumption of the substance. An irregular
heartbeat, increased alertness, trembling hands, hyperactivity and ner-
vousness are among the most common adverse eects experienced
by athletes when they consume caeine. On occasions, when these
eects appear, they do not prevent the athlete from improving his/her
performance, as was the case with the rowers in Carr et al’s study
23,
who
improved their times in an 2,000-metre ergometer test, or the partici-
pants in the study of Pallares et al
51
, who signicantly improved their
neuromuscular performance with 9 mg/kg despite the appearance of
adverse side eects. On other occasions, however, the side eects do
inuence the athlete, hindering improved performance, as occurred in
the study conducted by Share et al
79
with elite clay-pigeon shooters, who
experienced symptoms such as headaches, anxiety and tremors after
taking caeine, which particularly aected their accuracy, the primary
indicator of performance in the discipline.
Another study evaluated the eect of caeine on sleep quality in
athletes who consumed the substance as an ergogenic aid in an aerobic
activity carried out in the afternoon
80
. Caeine improved the physical
performance of the participants in the afternoon, but signicantly
disrupted their sleep indices at night: reduction in sleep eciency,
diculty falling asleep and overall decrease in sleep itself. So although
caeine may work as an eective supplement to improve endurance
performance, athletes who consume it in training and/or competitions
late in the afternoon or in the evening should take into account its
detrimental eect on sleep.
Developments in research on caffeine and sport
The eect of caeine on performance depending on the
time of day
Three studies have investigated the eect of caeine taken in
the morning and in the afternoon to nd out when caeine should
be taken to benet athletic performance the most, while minimising
adverse eects. Working on the basis that the body’s circadian rhythm
produces neuromuscular declines in the morning, Mora-Rodriguez et
al
81
designed a series of muscle strength and power tests for trained
athletes, who completed them in the morning (10 am) after taking
either 3 mg/kg of caeine or placebo and in the afternoon (6 pm) after
taking placebo alone. Muscle strength and power output in the tests
proved signicantly higher in the afternoon than in the morning with
the placebo, while caeine improved performance in the morning com-
pared to the placebo. Caeine consumption, therefore, would appear
to counter the neuromuscular declines caused by the body’s circadian
rhythm, improving muscle strength and power in trained athletes in
the morning, raising their level of performance to that of the afternoon.
Antonio García Moreno,
et al.
264
Arch Med Deporte 2016;33(4):259-266
Mora-Rodriguez et al
82
and Souissi et al
83
administered caffeine
(5 and 6 mg/kg) and placebo in morning and afternoon exercise
sessions. The results showed that the level of caffeine in blood plasma
increased in the participants in a similar fashion in the morning and
in the afternoon, leading to a substantial improvement in performan-
ce. The negative effects were more prevalent after caffeine intake
in the afternoon. So caffeine consumption can be recommended
in the morning to favour performance and minimise any resulting
adverse effects.
The eect of caeine on performance in exercise carried out
on consecutive days
A very recent study
84
assessed the performance of experienced
golfers in a golf tournament played over two days in which the par-
ticipants ingested a dose of 155 mg of caeine before starting and
halfway through each round. The results showed that the caeine
increased the golfers’ capabilities and substantially reduced fatigue
during the tournament. Two other studies measured the eect of ca-
eine intake on performance in demanding physical activities, skiing
85
and sprinting
86
, over 2 consecutive days. Caeine enhanced sprint
capability and speed in the cross-country skiing trial (which consisted
of 10 minutes on a laboratory simulator) on both days of exercise, and
greater muscle damage was observed on the second day as a result
of the heightened performance on the rst. Caeine, therefore, would
seem to be a useful supplement for athletes competing on consecutive
days because it can improve performance on both days of physical
exercise, counteracting the muscle soreness produced after the rst
day and reducing fatigue.
The eect of caeine on the recovery period and delayed
onset muscle soreness (DOMS)
One study
87
measured the physiological parameters of wrestlers
during the breaks between 4 ghts simulating a competition after
taking 5 mg/kg of caeine. The elevated heart rates and blood lactate
levels observed in the wrestlers who had consumed caeine suggest
that it may impair recovery between consecutive maximal eorts. In
another study conducted by Hurley et al
88
with trained athletes who
performed a set of muscle-strength exercises to failure after taking
5 mg/kg of caeine 1 hour before exercise, soreness and soreness on
palpation were recorded before exercise and 24, 48, 72, 96 and 120
hours afterwards. The results showed that caeine intake prior to
maximal strength training produces benecial responses in terms of
perception of soreness and performance, a signicant decrease in so-
reness levels being observed 48 and 72 hours after exercise, and more
total repetitions being performed with caeine compared to placebo.
A further benecial eect of sustained caeine ingestion in the days
after the exercise bout was an attenuation of DOMS. This decreased
perception of soreness in the days after a strenuous resistance training
workout could prove useful as it may allow individuals to increase the
number of training sessions in a given time period.
The eect of caeine on performance in a state of sleep
deprivation
We have seen that one of the adverse side eects of consuming
caeine in the afternoon or evening is the harm that it does to the
quality of sleep. But can caeine oset capabilities diminished by a
lack of sleep?
Two studies evaluated the physical and cognitive performance of a
group of athletes whose sleep was limited to between 2 and 4 hours
89,90
.
The results were aected by sleeping fewer hours than normal. In one
of the studies
89
, 80 mg of caeine was given to the subjects in a state
of sleep deprivation without improving performance, but taking into
account the extremely low dose used, one can only conclude that
adequate sleep is essential for rst-rate athletic performance and that
a dose of 80 mg is no substitute for a lack of sleep. The latest study
conducted in this eld of research
90
, however, did note improvements
in the performance of participants taking 3 mg/kg of caeine after little
sleep, so it can be claimed that caeine consumption is an eective
strategy to maintain physical and cognitive performance after a night
of limited sleep.
Conclusions
We can highlight the following conclusions from this review:
− Despite the wide variety of protocols and methodologies employed
by the dierent studies investigating the subject, no generalisations
can be made about the ergogenic eect of caeine on athletic
performance.
− Caeine has a clear ergogenic eect on aerobic and anaerobic exer-
cise, provided that those factors capable of limiting the response
of individuals to the substance are controlled.
− The latest trends in research point towards caeine consumption
in alternative forms, such as gels, chewing gum and energy drinks,
and have led to the discovery that caeine is an eective supple-
ment when it comes to compensating performance diminished
by high temperatures.
− Recent ndings show: that caeine is eective when athletes
compete or train on consecutive days; caeine should be taken
in the morning rather than in the afternoon in order to get the
greatest benet in terms of performance and minimise its adverse
eects; and the use of caeine is an eective strategy to maintain
physical and cognitive performance after a night of limited sleep.
Thanks
Dr. José Naranjo Orellana for the support and assistance received in the
preparation of this work.
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