EQOL Journal (2022) 14(1): 25-32
The relations between body mass index, motor skills, and physical self-
concept in determining physical activities of junior karatekas
Miroljub Ivanović
Uglješa Ivanović
Received: 15
March, 2022 DOI: 10.31382/eqol.220603
Accepted: 13
May, 2022
© The Author(s) 2022. This article is published with open access.
The aim of this research was to examine the
contribution of body mass index (BMI), motor skills
and physical self-concept in explaining the physical
activity (PA) of adolescent karatekas (N=148). The
average age of participants was 16,56 years (± 1,14).
The following measuring instruments were used:
Body Mass Index (BMI), Eurofit Physical Fitness
Test Battery, Physical Self-Description
Questionnaire (PSDQ), and Physical Activity
Questionnaire for Adolescents (PAQ-A). The
Cronbach's alpha coefficient was used to determine
the internal consistency of the questionnaires. The
results of the hierarchical analysis showed that the
predictor variables explained 18,5% of the total
variance of the criterion PA of junior karatekas.
With their positive direction, the independent
variables of the physical self-concept strength =
0.049; p < 0.01), flexibility (β = 0.037; p < 0.01) and
self-respect = 0.019; p< 0.05) showed the
maximum statistically significant contribution to
predicting the variability of the participants' PA,
which means that junior karatekas who manifest the
higher level of perception on those variables exhibit
the higher level of PA. This study confirmed that the
applied instruments are valid and suitable to predict
PA among adolescent athletes in Serbia.
Keywords karatekas adolescence eurofit
battery • PSDQ • PAQ-A.
The World Health Organization (WHO, 2010)
believes that increasing the level of PA (physical
activity) is the most relevant determinant for
improving the health of the population.
The optimal dosage of PA, prompted by
skeletal muscles and energy spending has a
positive effect on health, maintenance and
improvement of bio-psycho-social components,
and prevention of various diseases (Kljajević,
Stanković, Đorđević, Trkulja-Petković, Jovanović
& Sporiš, 2022). The study (Katsanis,
Hatyopoulos, Barkoukis, Afroditi, Chatyelli &
Paraschos, 2021) has confirmed that physical
inactivity causes the incr ease in body mass and
can lead to obesity. The authors (Kapsis, Tsoukos,
Psarraki, Douda, Smilios & Bogdanis, 2022)
believe that an intensive one-hour physical
exercise each day is necessary for good health and
active lifestyle.
The authors (Marsh & Redmayne, 1994)
established a hypothetical multidimensional
hierarchical model PSDQ, as self-perception
which is influenced by individual experiences and
the assessment by other people, and which
includes emotions such as self-acceptance, self-
respect, and competence. Self-concept is based on
this construct, and it includes academic and non-
academic self-concept. The component non-
academic self-concept, or physical self-concept,
includes perception of one’s physical skills and
Serbian Academy of Innovation Sciences,
Belgrade, Serbia
Telecom Serbia, Belgrade, Serbia
EQOL Journal (2022) 14(1): 25-32
body constitution. So, the nature of this measuring
instrument includes nine characteristic elements of
self-concept (such as health, motor coordination, PA,
BMI, athletic competence, physical appearance,
strength, flexibility, and endurance) and two general
elements (general physical self-concept and self-
The study (Palenzuela-Luis, Duarte-Clíments,
Gómez-Salgado, Rodríguez-Gómez & nchez-
Gómez 2022) points out that the multidimensional
structure of the physical self-concept includes many
variables, such as physical characteristics health,
BMI, physical appearance and general body shape on
the one hand, and flexibility, endurance and strength
on the other. Research (Jorga, Mastrappas &
Damigos, 2018; Wong, Chung & Leung, 2022) has
found the relationship between physical self-concept
and self-perception of one’s body.
Based on the results of the previous studies and the
fact that this topic has not been sufficiently explored
in the Serbian population, the aim of this transversal
research was to examine the relations and direction of
the determinants of motor skills based on Eurofit
battery and physical self-concept (as determinants) in
predicting the part of variance of PA in junior
karatekas. In accordance with the aforementioned
research findings, it is expected that the influence of
predictor variables (as presumed cause) in evaluating
the criteria of junior karatekas’ PA (as a consequence)
is statistically significant, and the higher predictive
intensity of motor variables (strength and flexibility)
is also expected, as well as the significance of the
dimensions self-respect of physical self-concept in
explaining the variance of PA of karatekas in the
period of early adolescence. Since the previous
studies did not provide the full insight into the
relations of the aforementioned variables (within the
population of adolescent karatekas), testing these
hypotheses can have influence on further empirical
research, as well as for sports practice in Serbia
Participants and procedure
Using the method of transverse cross-section, 148
junior karatekas were included in this research. The
average age of the participants was 16.56 years (SD
= 1.14). The convenience sampling included
karatekas from Kolubara district: KC “Shodan”
(Valjevo), KC 014 Valjevo (Valjevo), and KC
“Kizame” (Valjevo). All participants had minimum
two years of training, at least three times a week. The
research was conducted in 2022, during the month of
The authors of this research conducted the testing,
with the supervision of a psychologist. The
participants gave informed consent, with the approval
from parents and club managers. The participants first
had to fill in the questionnaire. Their anthropometric
measures were taken and general physical condition
was tested before their practice in the school gym.
The instructions were explained to the participants
and the subject of the research was presented; the
importance of answering truthfully was emphasized,
and they were told that they could quit at any time
without consequences and that the data would solely
be used for scientific purposes. Participation in this
research was voluntary and anonymous. The testing
lasted 45 minutes.
Measuring instruments
BMI was used as an indicator of the level of
nutritional status and is based on the international
classification which measures the anthropometric
measurements body height and body mass. This was
calculated by dividing body mass (in kilograms) by
the body height in meters (squared). The formula is
(Bubanja, Jovanović & Vuković,
The participants’ measures were taken as is
recommended by The International Biological
Program (IBP). Body mass was measured using the
standard decimal scale with the accuracy of 0,1kg,
while height was measured using the Martin
anthropometer with the precision of 0,1 cm and the
“Frankfort horizontal plane” head position.
Standardized EUROFIT Battery (Adams,
Klissouras, Ravazzolo, Renson & Tuxworth, 1988)
was used to examine the general PA, which meant
that the following four tests were measured: seated
forward bend (SFB), 30 s lying forward bend
(LFB30), standing long jump (SLJ), and 20m
progressive overload sprinting (POS).
Physical Self-Description Questionnaire (Marsh,
Redmayne, 1994)
The physical self-concept consists of 70 claims on a
six-point Likert scale (1 completely untrue, 2
mostly untrue, 3 somewhat untrue, 4 somewhat
true, 5 mostly true, 6 completely true) separated
into 11 subscales, where nine include specific
dimensions of physical self-concept: strength (3
items), obesity (3 items), PA (4 items), endurance (3
EQOL Journal (2022) 14(1): 25-32
items), athletic competence (3 items), motor
coordination (5 items), health (8 items), physical
appearance (3 items) and flexibility (3 items); and
two general components: general physical self-
concept (3 items) and self-respect (5 items). The
reliability coefficients (Cronbach's alpha) vary from
α = 0.72 for self-respect to α = 0.93 for athletic
competence, which is in accordance with the study
recommendation (McNeish, 2017).
Physical Activity Questionnaire for Adolescents
PAQ-A (Kowalski, Crocker & Kowalski, 2004)
PAs during the school year, excluding holidays. With
item one (PA during leisure), the participants assess
the level of agreement with the given statement and
give average assessment of the time they spent on PA
during the previous week, using the scale that ranges
from 1 (“no”) to 5 (“7 times or more”). Claims 2 to 7
include time (gym classes, time around lunch, right
after school, in the evening, during the weekend). On
the claim number 8 the participants assess the mean
value of all days, where the scale ranges from 1 (“no
activity”) to 5 (“very often”). The last 9th claim is
used for checking if the partic