УДК 612.821
CARDIORESPIRATORY POWER ACROSS ADOLESCENCE IN MALE SOCCER PLAYERS © 2011 P. T. Nikolai'dis
Laboratory of Human Performance and Rehabilitation, Department of Physical and Cultural Education, Hellenic Army
Academy, Greece Recived 18.03.2011
Despite the recognition of the beneficial role of cardiorespiratory power (CRP) for health and sport performance, the development of this physical fitness parameter in adolescent soccer players was not well studied. Aim of this cross-sectional study was to investigate the effect of age on CRP of adolescent soccer players, the influence of anthropometric characteristics and body composition on it, and to establish normative data. Male adolescent (N = 274; aged 12.07—20.98 y), classified in nine one-year age-groups, child (N = 12, aged 7.71—11.8 y) and adult players (N = 22; aged 21.12—31.59 y), all members of competitive soccer clubs, were examined for anthropometric characteristics and body composition and they performed Physical Working Capacity in heart rate 170 test (PWC170) on cycle ergometer. Analysis of variance revealed significant difference between age groups with respect to PWC170 in absolute (F10 297 = 29.58, P < 0.001, n2 = 0.5), relative to body mass (F10.297 = 5.28, P < 0.001, n2 = 0.15) and relative to fat free mass values (F10.297 = 4.98, P < 0.001, П2 = 0.14). In addition, age was in positive association with these parameters (r = 0.6, P < 0.001, r = 0.24, P< 0.001 and r = 0.23, P< 0.001, correspondingly). The main finding of this study was that CRP increased during developmental period in soccer players, even when it was adjusted to body mass or FFM, which increased during development. This documentation of the development of CRP provided useful tool for coaches and fitness trainers in order to apply optimal exercise interventions for health and performance.
Keywords: aerobic capacity, age, chronic diseases, development, sport performance.
While the lower spectrum of cardiorespiratory power (CRP) was associated with heart and pulmonary diseases (chronic obstructive pulmonary disease, coronary heart disease, chronic heart failure and intermittent claudication) [1], its higher spectrum might be linked not only to the absence of the aforementioned diseases, but also to well-being. In addition, training aiming to ameliorate the CRP was recommended by many national and international organizations focusing on health, e.g. American College of Sports Medicine [2] and World Health Organization [3]. CRP was inversely associated with BMI, it was lower in children and adolescents with higher BMI [4—7] and it was in close relationship with the parameters consisting the pediatric metabolic syndrome [8]. Increased risk for cardiovascular disease was found among adolescents with low CRP [9]. Children with chronic diseases had lower CRP than healthy controls [10]. In female and male adolescents, aged 12—14 y, power working capacity either expressed in absolute or in relative to body mass values was correlated with level of physical health (r = 0.46, P < 0.001 and r = 0.73, P < 0.001) [11].
Particular levels of physical activity should be attained in order to have healthy CRP [12], but since it was shown that aerobic adaptations to exercise intervention was influenced partially (approximately 50%) by heredity [13], it should be taken for graded that the outcome of an exercise intervention, e.g. to improve
CRP, could not be predicted accurately, and consequently it should monitored periodically. In addition to the aforementioned relationship with health, CRP was also closely linked to sport performance, e.g. there were indications that soccer players had higher values than their less efficient counterparts. Elite 13 y, 14 y, 15 y and 16 y players had higher CRP than their subelite and non-elite counterparts [14], while international U14, U15 and U16 had non-significantly higher CRP than their professional and amateur counterparts [15].
Whereas there was extended research regarding the development of this physical fitness parameter in general population [16—18] covering most of the period corresponding to adolescence, there was luck of studies that covered a wide range of adolescence in soccer. For example investigations of CRP on one [19], three [15, 20] or four yearly age groups [14, 21] were reported. With respect to other physical fitness parameters larger studies were conducted in soccer (anaerobic power in 11—18 y [22]; coordination skills in 11—19 y [23]). Therefore, considering the significance of CRP for both health and performance, a comprehensive study of this parameter on a large sample of soccer players was needed.
To sum up what was known so far regarding the development of CRP in soccer players two remarks should be highlighted: (a) There was evidence from a
Table 1. Anthropometric characteristics and body composition of participants
Age groups
U12 U13 U14 U15 U16 U17 U18 U19 U20 U21 Control
N 12 26 32 53 50 37 35 15 15 12 22
Age (y) 9.95 12.6 13.53 14.56 15.45 16.51 17.44 18.37 19.52 20.55 25.5
(1.53) (.24) (.26) (.27) (.28) (.3) (.28) (.32) (.32) (.27) (2.94)
Body mass (kg) 41.1 49.2 57.2 61.4 65.9 69.6 69.5 70.6 73.8 (6) 75.5 76.7
(10.7) (8.7) (7.6) (9.3) (9) (10.7) (10.5) (6.5) (7) (7.1)
Stature (m) 1.418 1.576 1.671 1.702 1.731 1.76 1.753 1.76 1.77 1.769 1.791
(.075) (.089) (.072) (.08) (.062) (.064) (.055) (.066) (.053) (.074) (.06)
BMI (kg m-2) 20.31 19.68 20.46 21.16 21.96 22.42 22.55 22.77 23.56 24.13 23.86
(3.93) (2.13) (2.15) (2.53) (2.54) (2.99) (2.62) (1.62) (1.61) (1.43) (1.25)
Body fat (%) 19 16.9 15.7 16.5 16.6 15.9 15.8 14.8 15.3 14.6 15.2
(6.9) (5.4) (3.6) (4.2) (4) (3.5) (3.6) (3) (3.1) (1.9) (3.4)
FM (kg) 8.4 8.6 9.1 10.3 11.2 11.3 11.2 10.4 11.4 11 11.8
(5.8) (3.6) (2.8) (3.8) (4) (3.9) (4.2) (2.4) (3) (1.9) (3.2)
FFM (kg) 32.7 40.7 48.1 51.1 54.7 58.3 58.2 60.2 62.4 64.5 64.9
(5.2) (6.4) (5.8) (6.7) (6) (7.4) (7) (5.8) (3.8) (5.9) (5.5)
"Vklues were presented as mean with standard deviation in brackets. BMI, body mass index.
few studies on small samples indicating that adolescent soccer players had superior values than their nonsport or lower level counterparts, and (b) there was inconsistency between findings on the development of CRP across adolescence. Therefore, aim of the present study was to investigate the development of CRP across adolescence in soccer players with reference to general population and to examine the research hypothesis that age groups in the higher spectrum of adolescence scored better than those in the lower spectrum.
METHODS
In this investigation, a non-experimental, descriptive-correlation design was used to examine the effect of age on CRP across adolescence. Testing procedures were performed during competition season 2009— 2010. Oral informed consent was received from all players or parents after verbal explanation of the experimental design and potential risks of study. Adolescence, though difficult period to define in terms of chronological age, because of variation in time of its onset and termination, it was suggested to range between 10 and 22 y in boys [24], and it was the period that consists a foundation stone for future athletic excellence. Male adolescent (N = 274; aged 12.0720.98 y), classified in nine one-year age-groups (group under thirteen U13, aged 12.07-13 y; U14, 13.06-14 y; U15, 14.03-14.99 y; U16, 15.01-15.98 y; U17, 16.02-16.99 y; U18, 17.01-17.96 y; U19, 18.02-19 y; U20, 19.03-19.96 y; U21, 20.01-20.98 y), child (N= 12, aged 7.71-11.8 y) and adult players (N = 22; aged 21.12-31.59 y), all members of competitive soccer clubs, volunteered for this study (Table 1). The players
were familiarized with the testing procedures used in this study through pre-investigation familiarization sessions. They visited our laboratory once; anthropo-metric and body composition data were obtained followed by a standardised 15 min warm-up and the Physical Working Capacity in heart rate 170 test (PWC170).
Height and body mass were measured using a stadi-ometer (SECA, Leicester, UK) and an electronic scale (HD-351, Tanita, Illinois, USA), respectively. Percentage of body fat (BF) was calculated from the sum of 10 skinfolds using a skinfold calliper (Harpenden, West Sussex, UK), based on the formula proposed by Parizkova [25]. PWC170 performed according to Eurofit guidelines [26] in a cycle ergometer (828 Ergo-medic, Monark Sweden). Seat height was adjusted to each participant's satisfaction, and toe clips with straps were used to prevent the feet from slipping off the pedals. Participants were instructed before the tests that they should pedal with steady cadence 80 revolutions per minute, which was given by both visual (screen showing cadence) and audio means (metronome set at 80 beats per minute). Figure 1 depicted the procedures and data analysis of this test. Briefly, this test comprised by three stages, each lasting 3 min, against incremental braking force in order to elicit heart rate between 120 and 170 beats per minute.
Results were presented as mean ± s (standard deviation). Data sets were checked for normality using the Shapiro-Wilks normality test and visual inspection. The effect age on CRP was examined by Pearson moment correlation coefficient (r), and partial correlations between the adjusted for anthropometric data (body mass, height and BF) CRP and age were calcu-
lated. Differences between age-groups were assessed using one-way analysis of variance (ANOVA). Correction for multiple comparisons was undertaken using the Bonferroni method. Student t-test was employed to examine differences in CRP between participants with lower and higher BMI, as well as between those with lower and higher BF. Significance level was set at alpha = 0.05. Statistical analyses were performed using SPSS v.17.0 statistical software (SPSS Inc., Chicago, IL, USA).
RESULTS
PWC170 was in positive association with body mass (r = 0.6, P < 0.001) and fat free mass (r =
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