1 Helgerud et al. (2001) showed that an increase in maximal oxygen uptake (VO 2max ) may improve the tactical and technical performance of the players by 7%. This also means more efficient ball contacts and more and longer sprints during a game (Chamari et al., 2005). It has been well established that body dimensions (i.e., body weight, body height, shoulder width, chest circum- ference) significantly affect cardiorespiratory performance, and strong correlations have been reported between car- diorespiratory indicators and anthropometric measures (Osborne et al., 1992). The role of body dimensions in cardiorespiratory endur- ance is more relevant in adolescents (Ostojic et al., 2014). According to Liyanage and Jayamanne (2017) body height, chest circumference and fat-free mass predict respiratory parameters in children aged 8–16 years. Previous results also suggest that there is a strong positive relationship * Corresponding author: Bettina Béres, e-mail tanczos.bettina@tf.hu Article history: Received 3 August 2020, Accepted 5 January 2020, Published 10 March 2021 Copyright: © 2021 The Author(s). Published by Palacký University Olomouc. This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This license does not cover any third-party material that may appear with permission in the article. ORIGINAL RESEARCH Relationship between biological age, body dimensions and cardiorespiratory performance in young soccer players Bettina Béres * , István Györe, Leonidas Petridis, Katinka Utczás, Irina Kalabiska, Gergely Pálinkás, and Tamás Szabó Research Centre for Sport Physiology, University of Physical Education, Budapest, Hungary Abstract Background: During adolescence, performance in competitive sport is influenced not only by the levels of physical activity, but also by the biological state and body dimensions. Objective: The purpose of our study was to compare cardiorespiratory performance between groups with different biological age in male adolescent soccer players. Methods: Eighty-eight young soccer players (age = 15.9 ± 0.5 years, body height = 176.1 ± 5.6 cm, body weight = 65.4 ± 7.2 kg) performed a vita-maxima protocol on a treadmill. Starting speed was 6 km/h and inclination 1.4%, which were increased linearly every minute, to 11 km/h and to 3.5% respectively (first 5 minutes). Then we increased inclination by 2% every minute until exhaustion. The effect of the biological age on functional indices was exam- ined based on two grouping methods. First, the participants were classified into sub-groups by their morphological (or developmen- tal) age, which is an expression of biological age and evaluates the developmental state of specific body dimensions (body height, body weight, shoulder width, lower arm girth, and hand circumference). Then, from anthropometric and body composition measures three clusters were created, according to the participants’ developmental state. For both grouping methods, the groups were: late- maturing, average-maturing, early-maturing. Results: Based on the morphological age grouping method, biologically more advanced athletes achieved greater cardiorespiratory performance (late-maturing: 337 ± 33 W, average maturing: 363 ± 48 W, early maturing: 386 ± 43 W) with higher oxygen uptake (late-maturing: 3529 ± 336 ml/min, average-maturing: 3798 ± 436 ml/min, early-maturing: 3983 ± 541 ml/min) and oxygen pulse (late-maturing: 18.1 ± 1.8 ml/beat, average-maturing: 19.6 ± 2.5 ml/beat, early-maturing: 20.8 ± 2.8 ml/beat). There were no differences in time spent on the treadmill, maximal lactic acid levels, relative power, maximal heart rate, respiratory rate, tidal volume, relative maximal oxygen uptake, maximal ventilation. There were significant differences in weight, plastic index and muscle mass between all the three groups. Differences in cardiorespiratory indices between groups of dif- ferent maturity status were larger when we grouped the athletes based on cluster analysis compared to the morphological age-based grouping method. Conclusions: During growth and maturation Body dimensions and body (and muscle) mass significantly affect maximal oxygen uptake in young athletes. The inclusion of body composition components in addition to body dimensions increases the explanatory power of biological age on cardiorespiratory performance. Keywords: maturity, spiroergometry, oxygen uptake, cluster analysis, football ACTA GYMNICA, 2021, Volume 51, Article e2021.001 https://doi.org/10.5507/ag.2021.001 Introduction In soccer, players have to meet significant physical, techni- cal, tactical and mental expectations (Stølen et al., 2005). Fitness requirements during official competitions include a high level of aerobic and anaerobic capacities. Depend- ing on their playing position, the players cover approxi- mately 10–13 kilometres with varying intensity, averaging 85–98% of their maximum heart rate and 70% of their maximum oxygen uptake during a single game (Bangsbo et al., 2006). Measurements indicate that both aerobic and anaerobic metabolic pathways contribute significantly to performance during the match (Alghannam, 2012; Red- kva et al., 2018). Thus, existing evidence suggests that an advanced cardiorespiratory system is an important ele- ment of game performance at the elite level (Chamari et al., 2005). OPEN ACCESS