1. THE EFFECT OF PHYSICAL FATIGUE ON REACTION
TIME BETWEEN PROFESSIONAL AND AMATEUR
SOCCER PLAYERS
Between Professional and Amateur Players
PL van Heerden (BA Human Movement Sciences)
JA de Roos (BSc Sport and Exercise Science)
Cell: 072 287 5063 Email: jordyanterio@gmail.com
Keyword(s): Reaction Time, fatigue, soccer,
maximal

2. Abstract
Reaction Time (RT) is an important component in many sport settings and coaches are
always looking to improve on this in order to improve all round performance. The purpose of
this study is to determine how fatigue influences RT with a comparison between professional
and amateur soccer players. Twenty soccer players (n=20) were used for this study, 10
professional and 10 amateur players. They were tested on a field with their soccer boots and
the necessary attire to make it specific to the sport. Each player completed an initial, rest
value RT test for a baseline measure. Thereafter they participated in a series of maximal
shuttle sprints. After each bout they completed RT tests to monitor progress. Distance was
recorded for each bout. According to the graphs there was no significant difference in the
extent to which the average distance covered decreased between the two samples. There
were also a similar trends shown for RT between the two samples, however the professional
groups changes were not as dramatic as the amateur group. It was found that the professionals
did have better RTs on average however further study is needed to indicate how different the
different levels of fatigue affect the RTs of the players.
Key word(s): Reaction Time, fatigue, soccer, maximal

3. Introduction
Reaction Time (RT) is an important component in many sport settings and coaches are
always looking to improve on all the fitness components in order to improve all round
performance. In soccer, a defender needs a rapid RT in order to make a tackle, deciding
when and which way the opponent is going to move the ball. A goalkeeper will need a great
RT when making a save. A striker needs to react to an attempted tackle by the opposition’s
defender. During a soccer match, the players undergo bouts of explosive sprints and need to
recover quickly in order to maintain a high level of performance and may reach a point of
fatigue. The purpose of this study is to determine how an acute fatigued state influences RT
in soccer players, comparing the different levels of profession (professional and amateur). We
found no studies that looked at this topic specifically but many had similar tests and goals.
In competitive situations Ozdemir, Kirazci and Ugras (2010) state that athletes should not
only be able to perform several motor skills effectively, but they should also be able maintain
these skills under the restriction of several regulations during strenuous exercise conditions.
In this study we place them under such conditions to initiate a fatigued state and test their
RTs at various levels in bouts.
RT is defined by Sabzi (2012) as the period between the application of a stimulus and the
beginning of a movement. Some studies have proven that different exercise intensities have
different effects on RT. Sabzi (2012) proved that anaerobic, mixed and super maximal
intermittent exercises had the greatest effect on RT. Physical exercise close to ventilatory
threshold positively affects basic cognitive task performance Rattray and Smee (2013).
Therefore vigorous anaerobic exercise was used in our study to create an onset of fatigue.
Fatigue can be described as loss of functional and cognitive output ability due to a number of
factors. Hatton et al. (2013) defined fatigue as ‘the observation of a decrement in
performance following exercise. Muscular fatigue is characterized by a lack or decrease in
power output and strength. Cognitive or mental fatigue is characterized by a lack of
consciousness or concentration which can be harmful when performing tasks such as driving
or handling machinery. Sabzi (2010) defined fatigue as a multidimensional and unknown
phenomenon that leads to a decrease in work capacity and arbitrary power output.
Hogervorst, Riedel, Jeukendrup and Jolles (1996) stated that there is controversy over the
effect of exercise on cognition. They found that several studies had described the effect of
exercise as negative on performance cognition task. Most of these exercises where short

4. duration and lasted between two to fifteen minutes. Audiffren, Tomporowski & Zagrodnik
(2008) confirmed this and stated that exercises gradually reduces peak reaction time between
15- 20min.
Studies have been done between these two variables and found that different exercise types
and intensities have different effects on both types of fatigue.
Draper, McNorris and Parker (2010) found that fatigue can negatively affect choice or probe
reaction and response time. The difference between reaction and response time is that RT is
measured up until the initiation of a movement such as pressing or releasing a button and
response time is referred to exerting a larger movement. Draper, McMorris and Parker (2010)
compared the effect of acute short duration exercise on the performance of simple and choice
RT in line with the inverted U- hypothesis. It has been argued that high intensity exercise and
low intensity exercise would result in poor cognitive performance, while during moderate
intensity the results would be optimal. However there is little known empirical evidence to
prove this. Tomporowski (2003) stated that choice RT is likely to show linear improvements
with an increase in exercise intensity, although not explicitly.
In 1968 and 1980 Welford found that reaction would get slower as the subject gets more and
more fatigued. Welford (1980) also found that physically fit subjects had faster reaction times
and this was also proved by Levitt and Gutin (1971) and Sjoberg (1975).
Zemkova, Miklovic and Hamar (2009) had a similar method to what we used to perform the
RT test. Pressing a button as fast as possible, responding to a visual stimulus. Zemkova,
Miklovic and Hamar (2009) used a program called FitPro.
The information obtained from this study can give a good idea as to how well both
professional and amateur soccer players tolerate fatigue and how it would affect their RT and
therefore, performance. This could be useful to a professional coach by illustrating if his
players are performing at an elite level or below standards. An amateur coach can use this
information to find ways of improving the performance of amateur players and to strive to be
in the elite class. This information could also be used to set a benchmark when comparing
the two different levels of soccer.
The possibility exists to extend the study and incorporate heart rate as initially planned.
However with adequate resources it would be a good idea to monitor the blood lactate levels
to see what level of fatigue has been achieved and whether that is similar from athlete to

5. athlete. The possibility also exists to see how fatigue would affect hand- eye coordination or
for soccer foot- eye coordination.
Sanders (1998) cited studies showing that reaction times are less consistent when the subject
has not had adequate practice of the task.
Researchers who have examined the effects of anaerobic exercise on cognitive processes
have consistently failed to detect a clear relation between exhaustive exercise and processes
involved in perception, sensory integration, or discrimination.
Materials and Methods
This was a quantitative, cross-sectional study. Participants were selected from various soccer
clubs with respect to their level of profession and district league within which they play. A
convenient sample of (n=20) was selected, 10 amateur players and 10 professional players.
The reason for the small size was because testing took place just after mid-season and not
many teams were willing to risk injury to their players at that particular stage of the season.
They were tested on a field with their soccer boots and the necessary attire to make it specific
to the sport. The amateur players were selected at random from the Cape Town Tygerberg
Football Association (CTTFA) and specifically from the premiere league, the highest level of
amateur soccer in the Western Cape. The professional players were selected at random from
either the National First Division (NFD) or the Premiere Soccer League (PSL), the highest
level of soccer in South Africa. Ten players were selected from each of the levels, having
two samples of ten players.
The professional and amateur soccer players underwent the same tests in order to determine
what effect acute fatigue had on their RTs. The Deary-Liewald RT Tester was used to
measure the RT, in milliseconds, of each player via a laptop we had on site. The Deary-
Liewald RT test has been used by multiple sources and has been deemed credible. The same
laptop where used for all players. The method used to produce acute fatigue was 20 meter
shuttle running at maximal effort. The fatigue experienced by each player was shown by the
decrease in distance during each bout.
The following protocol was implemented with each player:

6.  5 practice runs on the RT test to become familiar with the apparatus (An “x” will
appear in a block on the screen. The space bar needs to be pressed as quick as
possible once the “x” appears)
 Standardised warm-up routine
 Initial resting RT score was taken
 Then a 30 second bout of maximal shuttle sprinting, followed by 15 seconds to record
a RT reading was done. This was repeated four times.
 Test complete
The Deary-Liewald RT tester displays an empty block in the middle of the screen, in which
an “x” appears. The participant had to react by pressing the spacebar as quick as possible
once the “x” appeared. The participants kept their fingers ready on the spacebar for
standardisation.
Distance was measured by counting cones spaced one meter apart up to 20 meters. All Tests
were performed on grass and all participants wore their soccer boots and training gear to
avoid restrictions and keep the test standardised.
Upon completion of the following data was captured:
 RT (msec): at rest; post bout 1; post bout 2; post bout 3; post bout 4
 Distance covered with each bout
To analyse this data we used an independent sample t-test for each stage/bout comparing
professional and amateur players and an additional t-test to compare the overall differences
between the RTs of the two different samples. Graphical representation in the form of line
graphs were used to show the comparison of the average scores of distance and RTs between
professional and amateur levels.

7. Results
Figure 1: Average distances covered between professional and amateur players during each
bout of shuttle sprints.
Figure 1 shows a gradual decrease in the average distances covered by both professional and
amateur player as the bouts took place. The sharpest decline appears to have occurred from
the first to second bout. There was a plateau between bouts 2 and 4 with a slight but
insignificant increase in distances in the fourth bout for both groups.
A fatigue index was made to give an indication of the degree of fatigue experience by both
groups:
(Distance covered bout 1 – Distance covered after 4th bout) ÷ Distance covered bout 1 × 100
= Anaerobic Fatigue %
Professionals = 14.65%
Amateurs = 18.5%
The above calculation displays the percent decline in distance covered by the two sample
groups over the four bouts of vigorous exercise.
(RT bout 0 (rest) – RT bout 4) ÷ RT bout 0 (rest) × 100 = % decline in RT
Professionals = 4.49%

8. Amateurs = 4.05%
The above calculation displays the percent decline in reaction time achieved by the two
sample groups from rest to after the four bouts of vigorous exercise.
Figure 2 Illustrates a comparison of the average RTs between professional and amateur
players recorded after each bout of shuttle sprints. (Note: Bout 0 indicates resting RT values)
In figure 2, both samples portrayed a similar pattern, with the increases or decreases in RT
being more exaggerated in the amateur group. In both groups there was an increase in
average RT between the rest and first bout indicating they became slower. There was a
decrease (improvement) in average RT between the first and second bout for both amateurs
and professionals. Between the second and third bout the reaction time remained relatively
the same, slight decrease, for the professional group but increased for the amateur group.
From the third to the end of the final bout both amateur and professional groups improved
their reaction times.
It is important to note that a decline in RT means that there is improvement and if there was
an increase in RT, it has deteriorated.
200 220 240 260 280 300
0
1
2
3
4
Reaction Times (msec)
ShuttleBouts
Professionalvs Amateur Reaction
Times
Amateur
Pro

9. Table 1. The reaction time statistics
*Significance is set at 0.05
Table 1 shows that there is a significant difference between the average reaction times
professional and amateur players. However it does not show the degree to which they differ
between bouts or at different levels of fatigue. That will require further study.
Discussion
According to the findings, professional players proved to have better speed endurance and
fatigue tolerance than the amateur players as suspected, but they were only significant in
average reaction time as opposed to each bout.
The professionals proved to have a higher fatigue tolerance to the vigorous exercise which
supports a study done by Rampinini et al. (2011) which concluded that in high-level
professional players, the fatigue induced by a soccer match occurs to a smaller extent than in
amateur players.
The percentage decline in RT proved that the professional group handled or maintained their
RT better in the fatigued state than their amateur counterparts.
The results of this study supports the study done by Tomporowski (2003) which tested the
effects of different exercise types on RT, and a study done by Kashihara and Nakahara (2005)
which found that vigorous exercise improved choice RT, but only for the first 8 minutes after
exercise. Therefore it could be said that the acute effects of vigorous exercise improve choice
BOUT
no.
Professional (P) Amateur (A) Mean
difference
(A-P)
t p-value
Mean ± SD (msec) Mean ± SD (msec)
1 (rest) 251.6±37.8 269.0±36.5 17.4 -1.047 0.309
2 262.1±40.5 283.2±57.4 21.1 -0.95 0.355
3 254.8±21.9 266.5±53.6 11.7 -0.639 0.531
4 253.7±25.3 276.5±23.8 22.8 -2.077 0.052
5 240.3±6.5 258.1±38.5 17.8 -1.442 0.167
Average 252.5±7.9 270.66±9.6 18.16 -3.268 0.011*

10. reaction, as it showed from the results. This means that coaches can utilize an intense warm
up before a game to enhance their reaction times to avoid “waking up late” during a game.
The reason for the initial increase in RT directly after the first bout is not well understood but
it is suspected that the initial shock to the physiological system going from resting to a
maximal state may be a key factor. Another factor that could have possibly affected this
trend is that they were still adjusting to the test protocol and in turn caused a delay in the first
reading after a bout of vigorous exercise. Further study is needed to investigate the reason
for that finding.
The professional group displayed the characteristics expected from elite athletes and the
amateur group were less consistent as predicted. In other words, professionals proved
themselves to be of a better standard, both in reaction time and the ability to maintain that
reaction time, while under strenuous conditions. A professional athlete should have the trait
or ability to repeat a task over and over, at the same given intensity, more accurately than an
amateur athlete.
It is suspected that in the final bout psychological factors played a role in the increased
average distance covered with knowing that there will be no more exertion after that and
acted as motivation, however this has not been elucidated and is not necessary for the current
study.
Conclusion
In conclusion it can be said that professional players do have faster RTs than amateur players
on average at various stages of acute fatigue. Factors for this could be due to better quality of
training resulting in better fitness levels. Conveniently supporting Welford (1980) and Gorg,
Lata, Walia, & Goyal (2013) who pointed out that physically fitter individuals have faster
RTs. However the tolerance of fatiguing effects on RT needs further study.
If we compare relative values, in accordance with their fitness levels, there is not much
difference between the two groups. If we compare in absolute fashion, the professionals do
have better RT results at various stages during maximal shuttle sprinting intervals.

11. Recommendations
We recommend that future studies should incorporate heart rate and lactate as a
measurement. A possibility would be to monitor it during a game as you would incorporate
the effect of aerobic and anaerobic modalities. A possibility would also be to try and find a
reaction time test that is more specific to soccer and the movements required for the sport. A
larger sample size would be required to make the results more significant. A deeper
investigation can be done to observe the difference in the fatiguing effects of exercise
between the two levels of profession.
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