Faculty of Sport, University of Ljubljana, ISSN 1318-2269  75 Kinesiologia Slovenica, 16, 1-2, 75–83 (2010)
Izvleček
Cilj raziskave je bil izmeriti vrednosti preučevanih 
kinematičnih spremenljivk in ugotoviti, ali obstajajo 
statistično pomembne razlike v vrednostih omenjenih 
kinematičnih spremenljivk pri natančnih nogometnih 
brcah z notranjo stranjo stopala po približanju žogi 
pri kotu 0 stopinj ter pod kotoma 30 in 60 stopinj. V 
vzorcu preizkušancev je bilo 20 poklicnih nogometašev 
iz nogometnega kluba ‘Radnički‘ iz Niša, Srbija. Za 
snemanje tehnike brcanja z notranjo stranjo stopala 
v vodoravni ravnini smo uporabili hitro kamero, ki 
je delovala s frekvenco 300 Hz. Enosmerna analiza 
variance je pokazala pomembne razlike v vrednostih 
vseh preučevanih spremenljivk, z izjemo linearne 
hitrosti žoge po brci in trajanja stika stopalo-žoga. V 
nekaterih razponih vrednosti preučevanih spremenljivk 
so bile dosežene natančne vrednosti. Poleg tega so 
preizkušanci, kljub temu da se je kot udarca noge 
pomembno razlikoval od kota približevanja nogometaša 
(0, 30 in 60 stopinj), svojo nogo pred brco samodejno 
nastavili v skoraj enak položaj in nato streljali. 
Ključne besede: biomehanska analiza, nogomet, kot pri-
bliževanja, razlike
Abstract
The aims of this research were to quantify the range 
in values of examined kinematic variables and the 
existence of statistically significant differences in values 
of the kinematic variables in accurate attempts of soccer 
kicks inside the foot, subsequent to approach abreast, 
within an angle of 0 degree and angled approaches, 
within angles of 30 and 60 degrees. The sample of 
subjects consisted of 20 professional soccer players of  
F.C. ‘Radnički’ from Niš, Serbia. A high-speed camera 
operating at 300 Hz was used to record the inside-foot 
kicking technique, in a horizontal plane. One-way 
ANOVA showed significant differences in the values of 
all examined variables, with the exception of the linear 
velocity of the ball after the kick and the duration of 
foot-ball contact. There are certain ranges in the values 
of the examined variables within which the accuracy 
was achieved. Also, although the angle of attack of the 
swing foot significantly differed compared to angle of 
approach of soccer player (0, 30 and 60 degrees), subjects 
automatically set their swing foot in almost a similar 
position before the kick, and hit the target. 
Key words: biomechanics analysis, soccer, angle of ap-
proach, differences
1
Faculty of sport and physical education, University of Niš, 
Serbia
2
1
st
 E.P.A.L. High School, Kozani, Greece
* Corresponding author: 
Faculty of Sport and Physical Education, University of Niš
St. Čarnojevića 10a
18000 Niš, Serbia
Phone: +381 1 8510900
Fax: +381 1 842482
E-mail: bubanjsasa@yahoo.co.uk
KINEMATICS OF ACCURATE INSIDE OF 
FOOT KICK
KINEMATIKA NATANČNE BRCE Z 
NOTRANJO STRANJO STOPALA
Saša Bubanj*
1
Ratko Stanković
1
Saša Joksimović
1
Radoslav Bubanj1
Stanimir Joksimović
1
Goran Kozomara
1
Pavlos Efthimiadis
2

76 Kinematics of foot kick Kinesiologia Slovenica, 16, 1-2, 75–83 (2010) 
INTRODUCTION
Previous studies in biomechanics that focused on accurate soccer kick indicated the possible 
influence of certain kinematic variables on the accuracy of target hit. These studies showed a 
decrease in the approach velocity of the soccer player, as well as linear and angular joint velocities 
and ball speed, compared with powerful kicks (Godik, Fales, & Blashak, 1993; Lees and Nolan, 
1998; Teixeira, 1999). In regard to curve kicks, Asai and colleagues (Asai, Carre, Akatsuka, & 
Haake, 2002) indicated that the determinant factor in spinning a ball was the angle between the 
direction of impact surface of the kicking foot and the swing direction. In contrast, the ball would 
follow a nearly straight trajectory and gain the maximum possible velocity with minimal spin, 
if it is hit at the center (Asai et al., 2002; Carre, Asai, Akatsuka, & Haake, 2002). Concerning the 
point of impact on the foot, the results of study conducted by Ozaki and Aoki (2008) showed 
that the impact point in the in-front curve kick, in which a player kicks a ball by rubbing it up 
with toe, was located nearer to the toe, compared to the in-front curve kick, in which a player 
utilizes the angle of attack to spin the ball and in the inside kick. According to results of the 
research conducted by Shinkai et al. (Shinkai, Nunome, Ikegami, & Isokawa, 2008), in side-foot 
kicking, the foot contacted the ball slightly longer than in the instep kicking. The mentioned 
variables that affect the accuracy are also influenced by various factors, such as training level, i.e. 
professional vs amateur soccer players (Asami and Nolte, 1983; Commetti et al., 2001; Davids, 
Lees, & Burwitz, 2000; Lees and Nolan, 1998), gender (Barfield, Kirkendall, Yu, 2002), preferred 
leg (Dorge, Andersen, Sorensen, & Simonsen, 2002; Nunome et al., 2006) and muscle strength 
(Masuda et al., 2005; Ostojić, 2003; Reilly, 1996). Opavsky (1988) examined maximal ball speed, 
subject to type of approach. Values of ball speed were higher after running, compared to the 
stationary approach. However, results concerning the ball speed obtained during competition 
differ from those obtained in laboratory conditions (values were higher during competition, 
compared with the values reported in the literature, Ekblom (1994).
The aims of the research were to quantify the range in values of examined kinematic variables 
and the existence of statistically significant differences in values of the variables, in accurate 
attempts of inside of foot soccer kick, subsequent to approach abreast, within an angle of 0 degree 
and angled approaches at 30 and 60 degrees.
METHOD
Participants
The sample of subjects consisted of 20 professional soccer players of F.C ‘Radnički‘, 14 right-
footed, 6 left-footed (age: M = 20.3 years, SD = 4.45 years; height: M = 180.16 cm, SD = 6.44 
cm; weight: M = 76.4 kg, SD = 7.32 kg), competing in the 2
nd
 Serbian division. The study was 
conducted at the Faculty of Sport and Physical education of Niš, and in accordance with the 
ethical principles of the Helsinki Declaration, whereby each of the subjects agreed with a written 
consent to any procedures related to research.
Instruments and procedure
For the purposes of study, a special designed steel platform was constructed, on which were 
placed a wooden board (P = 3m
2
) and glass plate (P = 1m
2
) in the form of square. The glass plate 

Kinematics of foot kick 77 Kinesiologia Slovenica, 16, 1-2, 75–83 (2010)
consisted of three layers (thickness of each layer was 10mm) mutually connected by plastic film, 
in order to increase plate strength. Glass and wood substrates were located at a height of 1m from 
the ground. A mirror in the form of a square (P = 1m
2
), was placed below the glass plate at an 
angle of 45 degrees to the ground surface, with purpose of reflect the kicking technique of the 
subjects. At a distance of 2m from the mirror, in the projection of mirror’s centre and y axis, a 
Casio Exilim Pro F1 high speed camera was placed and adjusted to record 300 frames per second. 
At 10m distance from the centre of the glass plate and at a height of 2 m from the ground, i.e. in 
the projection of x axis, on a ripstol, a circular target (0.3m in diameter) was fixed (Figure 1).
Figure 1. The view (from above) of polygon.
A mirror set at an angle of 45 degrees to the surface enabled the recording of kicking technique 
in the horizontal plane. The point of intersection of x and y axis, i.e. the centre of the glass plate, 
was condense, the initial position of the ball, prior to ball kick. The rubber soles of subjects’ 
shoes were marked with coloured tape, which showed the extreme proximal and distal points 
of foot (Figure 2).

78 Kinematics of foot kick Kinesiologia Slovenica, 16, 1-2, 75–83 (2010) 
Figure 2. The view (from below) of platform and subject.
For the purpose of measurement, we used a FIFA-approved Nike ball, size five, with a diameter 
R = 220 mm, with markers drawn on it, in order to determine the number of ball rotations. 
Subjects were instructed to kick a stationary ball, aiming at a circular target placed in front of 
the ball, by using inside-foot kicking and stationary onestep approaches (0 degree, 30 and 60 
degree, Fig. 3). Subjects were asked, in the case of approach at an angle of 0 degrees, to hit the 
ball centrically, in order to avoid rotation of the ball in the horizontal plane while, in the case of 
approach at angles of 30 and 60 degrees, to hit the ball excentrically, in order to cause the rotation 
of the ball in the horizontal plane. The task was to hit the target 5 times with each of the three 
approaches, i.e. a total of 15 hits. In this experiment, only successful attempts of kicking the ball 
were considered (300 target hits). 
Figure 3. The view (from below) of the performed kicking technique.

Kinematics of foot kick 79 Kinesiologia Slovenica, 16, 1-2, 75–83 (2010)
A sample of variables consisted of the approach velocity of swing foot-AVSF (in m · s
–1
), the attack 
angle of swing foot (AASF, in deg), the angle of direction of the ball after the kick-ADBAK (in 
deg), the linear velocity of the ball after the kick-LVBAK (in m · s
–1
), the angular velocity of the ball 
after the kick (AVBAK (in deg · s
–1
), the number of rotations of the ball after the kick-NRBAK (1 
rotation=360 deg), the point of impact on foot-PCF (in %) and duration of foot-ball contact-DFBC 
(in s) (Figure 4). Concerning the variable PCF, in order to indicate the point of impact, the length 
of the foot was expressed in percentages. In this way, the proximal end of foot (heel) was 0% of 
total foot length while distal end of foot (toe) was 100%. PCF represented the projection of the 
point of impact between the foot and the ball (on coloured tape placed on sole of subjects and 
within an angle of 90 degrees).
Figure 4. Closer explanation of certain variables.
In order to examine kicking technique and determine values of the analysed variables HU-
M-AN
TM
 software for kinematics movement analysis was used. For statistical analysis and 
interpretation of results, SPSS version 13 software was used. The results were expressed through 
descriptive statistics; for establishing statistically significant differences between variables in ball 
inside of foot kick, analysis of variance (one-way ANOVA) was used.
R ESUlTS
All results of descriptive statistics and one-way ANOVA, are presented in Table 1.
The highest mean value of the attack angle of the swing foot (AASF) was achieved by hitting the 
ball after approach of subjects at an angle of 0 degrees (74.77 deg), then after approaching at an 
angle of 30 degrees (72.45 deg) and finally, after approaching at an angle of 60 degrees (66.94 deg). 
Concerning the mean values of the approach velocity of swing foot (AVSF), descriptive statistics 
showed that the highest mean value was achieved by hitting the ball after the approach of subjects 
at an angle of 60 degrees (14.03 m · s
–1
), then after approach at an angle of 30 degrees (13.12 m · 
s
–1 
) and finally, after approach at an angle of 0 degrees (12.59 m · s
–1
). The highest mean value 
of linear velocity of the ball after kick (LVBAK), was achieved by hitting the ball after approach 
of subjects at an angle of 0 degrees (16.37 m · s
–1 
), then after approach at an angle of 60 degrees 
(16.09 m · s
–1
) and finally, after approach at an angle of 30 degrees (15.79 m · s
–1
). In regard to 

80 Kinematics of foot kick Kinesiologia Slovenica, 16, 1-2, 75–83 (2010) 
angular velocity of the ball after kick (AVBAK), the highest mean value was achieved by hitting 
the ball after approach of subjects at an angle of 60 degrees (1865.19 deg · s
–1 
), then after approach 
at an angle of 30 degrees (1569.90 deg · s
–1 
) and finally, after approach at an angle of 0 degrees 
(1511.55 deg · s
–1 
). The increase in value of the variable AVBAK, directly affected the increase in 
value of the variable NRBAK. The highest mean value of angle of direction of the ball after kick 
(ADBAK), was achieved by hitting the ball after approach of subjects at an angle of 60 degrees 
(27.66 deg), then after approach at an angle of 30 degrees (24.77 deg) and finally, after approach 
at an angle of 0 degrees (19.31deg). The highest mean value of number of ball rotations after the 
kick (NRBAK) was achieved by hitting the ball after approach of subjects at an angle of 60 degrees 
(5.18), then after approach at an angle of 30 degrees (4.36) and finally, after approach at an angle 
of 0 degrees (4.20). Concerning the mean values of number of point of impact on foot (PCF), the 
point of impact on foot, effectuated by hitting the ball after approach of subjects at an angle of 
0 degrees, was the closest to distal part of foot i.e., to the heel and that is situated on 50% of the 
total distance from the heel, in regard to approaches at angles of 30 degrees, (where the point of 
impact was situated on 52% of the total distance from the heel), and 60 degrees, (where the point 
of impact was situated on 54% of the total distance from the heel), respectively.
Concerning the mean values of duration of foot-ball contact (DFBC), the mean values achieved 
by hitting the ball after approach of subjects at angles of 0, 30 and 60 degrees, were almost 
equal (0.0174, 0.0173 and 0.0175 s, respectively). Based on results of one-way ANOVA, it can 
be concluded, that in all analyzed variables, except in LVBAK (p=0.22) and DFBC (p=0.77), 
there was a statistically significant difference between the arithmetic mean values achieved after 
different angles of approach.
DISCUSSION
The obtained results of the variable AASF, i.e the ratio between mean values in different angles 
of approach, was expected, but the small range of mean values of the AASF (7.83 deg) indicates 
that the subjects almost automatically set their swing foot in a nearly identical position before 
the kick, regardless to the different angles of approach. The ratio between mean values of the 
Table 1. Descriptive Statistics and One Way ANOVA of kicking technique after different angles 
of approach of soccer player (0, 30 and 60 deg).
Variables N
0 deg 30 deg 60 deg
Sig. 
(ANOVA)
Mean SD Mean SD Mean SD
AASF (deg) 100 74.77 11.34 72.45 8.11 66.94 16.46 .00*
AVSF (m · s
–1
) 100 12.59 1.66 13.12 1.76 14.03 1.78 .00*
LVBAK (m · s
–1
) 100 16.37 2.51 15.79 2.25 16.09 2.23 .22
AVBAK (deg · s
–1
) 100 1511.55 772.81 1569.90 828.17 1865.19 872.48 .01*
ADBAK (deg) 100 19.31 11.64 24.77 11.53 27. 6 6 8.35 .00*
NRBAK (rotation) 100 4.20 2.15 4.36 2.30 5.18 2.42 .01*
PCF (%) 100 .50 .07 .52 .08 .54 .08 .00*
DFBC (s) 100 .0174 .00 .0173 .00 .0175 .00 .77
* Indicates a statistically significant difference (P ≤ 0.05) 

Kinematics of foot kick 81 Kinesiologia Slovenica, 16, 1-2, 75–83 (2010)
variable LVBAK, in the different angles of approach, is in accordance with the ratio in the results 
of research, conducted by Kellis and colleagues (Kellis, Katis, & Gissis, 2004), Isokawa and Lees 
(1988), Opavsky (1988), and Roberts et al. (1974). This research was conducted in conditions in 
which the ball was stationary before impact. It usually is not the case in terms of a soccer game: 
the ball is usually moving towards the player just before the shot. Nevertheless, the results of 
research conducted by Тol et al. (2002) do not indicate statistically significant differences in the 
velocity of the ball after the kick, i.e., the ball that was stationary before impact, compared to 
the ball that was moving at a velocity of 2.2 m · s
–1 
before impact. By observing the mean values 
column, it is obvious that, as the approach angle of subjects increased in such a manner, the 
AVBAK and NRBAK variables increased, while on the contrast the attack angle of the swing 
foot AASF decreased. This is in accordance with the ratio between the mean values of research 
conducted by Ozaki and Aoki (2008). The ratio between mean values of the variable NRBAK in 
different angles of approach is in accordance with the ratio in the results of research conducted 
by Asai et al. (2002), Carre et al. (2002), and Wesson (2002). The ratio between the mean values 
of the variable PCF in different angles of approach is in accordance with the ratio in the results 
of research conducted by Ozaki and Aoki (2008). According to these authors, the mean value of 
point of impact, after approach abreast is nearer to the distal end of foot (heel), compared with 
angled approach. The mean values of variable DFBC in different angles of approach are close to 
duration of contact time in research conducted by Tsaousidis and Zatsiorsky (1996). According 
to these authors, the duration of impact time, i.e. the duration of contact between the swing foot 
and the ball was long (about 16 ms). The results of the one-way ANOVA, are in accordance with 
results of research conducted by Scurr and Hall (2009), in regard to differences in velocity of ball 
motion, after hitting the ball at different angles of approach. According to their mentioned study, 
statistically significant differences in the velocity of the ball after a kick did not exist.
Concerning this research, there was no statistically significant difference in linear ball velocity 
after the kick and in contact time between foot and ball, after different angles of approach. 
However, there are certain ranges in values of examined variables, within which the accuracy 
was achieved: mean value of linear ball velocity after kick ranged between 15.79 m · s
–1
 and 
16.37 m · s
–1
 and mean value of contact time between foot and ball ranged between .0173s and 
.0175s. Furthermore, although the angle of attack of the swing foot significantly differed, com-
pared to angle of approach of soccer player (0, 30 and 60 degrees), subjects automatically set their 
swing foot in an almost similar position before the kick and hit the target. Therefore, in addition 
to previously mentioned mean value of angle of attack swing foot is ranged between 66.94 deg and 
74.77 deg. However, conflicting findings, various factors, and different values of the examined 
variables reported in the literature do not allow safe conclusions about general conditions that 
need to be accomplished in order to increase the accuracy of in inside-foot soccer kick.
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APPENDIX
Figure 5. The platform.
Figure 6. The side view of platform.