Monitoring training load in youth soccer players: effects of a six-week preparatory training program and the association between external and internal loads

Sandra Lechner; Achraf Ammar; Omar Boukhris; Khaled Trabelsi; Jordan M Glenn; Jesper Schwarz; Omar Hammouda; Piotr Zmijewski; Hamdi Chtourou; Tarak Driss; Anita Hoekelmann

doi:10.5114/biolsport.2023.112094

Monitoring training load in youth soccer players: effects of a six-week preparatory training program and the association between external and internal loads

Biol Sport. 2023 Jan;40(1):63-75. doi: 10.5114/biolsport.2023.112094. Epub 2022 Jan 3.

Authors

Sandra Lechner¹, Achraf Ammar^{1

2

3}, Omar Boukhris^{4

5}, Khaled Trabelsi^{4

6}, Jordan M Glenn⁷, Jesper Schwarz⁸, Omar Hammouda^{3

9}, Piotr Zmijewski¹⁰, Hamdi Chtourou^{4

5}, Tarak Driss³, Anita Hoekelmann¹

Affiliations

¹ Institute of Sport Science, Otto-von-Guericke University, 39106, Magdeburg, Germany.
² Department of Training and Movement Science, Institute of Sport Science, Johannes Gutenberg-University Mainz, 55099 Mainz, Germany.
³ Interdisciplinary Laboratory in Neurosciences, Physiology and Psychology: Physical Activity, Health and Learning (LINP2), UPL, UFR STAPS (Faculty of Sport Sciences), Paris Nanterre University, Nanterre, France.
⁴ High Institute of Sport and Physical Education of Sfax, University of Sfax, Sfax, Tunisia.
⁵ Research Unit, "Physical Activity, Sport and Health", UR18JS01, National Observatory of Sport, Tunis, Tunisia.
⁶ Research Laboratory: Education, Motricity, Sport and Health, EM2S, LR19JS01, University of Sfax, Sfax, Tunisia.
⁷ Department of Health, Exercise Science Research Center Human Performance and Recreation, University of Arkansas, Fayetteville, Arkansas, USA.
⁸ Braunschweiger Turn- und Sportverein Eintracht von 1895 e.V., Braunschweig, Lower Saxony, Germany.
⁹ "Research Laboratory, Molecular Bases of Human Pathology, LR19ES13, Faculty of Medicine, University of Sfax, Sfax, Tunisia.
¹⁰ Jozef Pilsudski University of Physical Education in Warsaw, Warsaw, Poland.

Abstract

This study examined the effects of a six-week preparatory training program on physical performance and physiological adaptations in junior soccer players. Additionally, we investigated whether a relationship existed between external and internal loads. Youth soccer players (aged 16 years old) from a youth football academy participated in six weeks of pre-conditioning training. Wireless Polar Team Pro and Polar heart rate sensors (H10) were used to monitor physical performance indicators (sprint and acceleration scores, covered distance, maximum and average speed and duration), physiological responses (maximum and average heart rate [HR] and R-R interval, time in HR zones 4+5, and heart rate variability [HRV]), and training load score. Additionally, muscle status and rating of perceived exertion (RPE) scores were measured using digital questionnaires. Significant increases were observed in the majority of physical performance indicators [i.e., sprints (p = 0.015, ES = 1.02), acceleration (p = 0.014, ES = 1), total distance (p = 0.02, ES = 0.87), as well as maximum speed (p = 0.02, ES = 0.87)]. A trend towards improvement was observed in the remaining performance indicators (i.e., distance/min and avg speed; ES = 0.6), training load (ES = 0.2), muscle status (ES = 0.3)), and all physiological responses parameters (ES = 0.1 to 0.6). Significant correlations were found between the majority of external load parameters (i.e., performance indicators) and objective (i.e., physiological responses) and subjective (i.e., RPE, muscle status) internal load parameters (p < 0.001). The highest number of moderate-large correlations were registered between performance indicators and time in HR zone 4+5 (0.58 < r < 0.82), training load (0.53 < r < 0.83), average HR (0.50 < r < 0.87), maximal HR (0.51 < r < 0.54) and average R-R interval (0.58 < r < 0.76). HR zone 4+5, average and maximal HR, average R-R interval, and training load score may help control training parameters and reduce the risk of under- or over-training in youth soccer players. However, these conclusions should be confirmed and replicated in future studies with more diverse subject populations.

Keywords: External parameters; Internal parameters; Training monitoring; Youth football.