Abstract
This study aimed to determine whether spikes in acute:chronic workload ratio (ACWR) are associated with injury incidence, and to examine the differences in external load due to greater or lesser exposure to matches and the long-term effects of the load during a chronic seasonal period. Fifteen professional soccer players belonging to the squad of a European Champions League club were enrolled in this study. External training and match load were assessed from all athletes using a global positioning system (GPS). We calculated the uncoupled ACWR for 10 consecutive competitive microcycles. Injuries were identified and determined by the days of absence. The differences in external load were determined using a linear mixed-model approach. In addition to the null hypothesis testing, the effect size was calculated. Thirteen athletes who did not suffer an injury exceeded several times the critical threshold of an ACWR > 1.5. This is equivalent to 1 player exceeding the critical threshold for ACWR in total distance (TD), 2 players for ACWR at distance covered above moderate speed (MSD), 2 players for ACWR at distance covered above high speed (HSD), 2 players for ACWR at distance covered above very high speed (VHSD), and 2 players for ACWR in DC at sprint per week. One athlete experienced a non-contact muscle strain injury and another a contact -injury manifested as a concussion; both athletes document an ACWR <1.5 within the 4 weeks prior to the injury event. Players with lesser participation in official games covered lower TD (−19.6%, very-large ES), MSD (−24.8%, very-large ES), HSD (−25.1%, moderate ES), VHSD (−25.5%, moderate ES), and DC at sprint (−30.6%, moderate ES) over the course of the 10-weeks period in comparison with the players with greater participation in official games. The present study demonstrated that spikes in the ACWR were not related to a subsequent injury occurrence in professional soccer players. Differences in participation in official games caused significant imbalances in the chronic external loads between players in a squad, which should be minimized in training sessions in order to prevent substantial changes in workload for those who usually do not play.
Highlights
Injuries are an important issue in professional football and they can negatively affect team performance, representing a significant cost to professional football clubs (Hagglund et al, 2013)
Two players were injured at the beginning of the 10 full competitive microcycles analyzed: the first athlete returned to full training in week 5 after meniscus surgery, and the second athlete returned to full training in week 6 after a groin injury
The results of the present study showed that participation in official games caused imbalances in the chronic external loads between players in a squad, with a significant reduction in the external chronic load of players with fewer minutes in competition
Summary
Injuries are an important issue in professional football and they can negatively affect team performance, representing a significant cost to professional football clubs (Hagglund et al, 2013). Players availability is associated with team success; the protection of players’ health by preventing injuries is claimed as essential by professional football clubs and international sports federations and is a crucial task for medical and trainer teams (Engebretsen et al, 2008; Hagglund et al, 2013). Measurements of internal training load quantify/assess the physiological and perceptual responses experienced during training sessions, and external training loads describe the running activity profiles of players during training sessions (Campos-Vazquez et al, 2014; Impellizzeri et al, 2019). The results of training are the consequence of both stimuli, and the monitoring of players’ workload is crucial to understand the individual physiological responses and biological adaptations to training for optimal training load management (Campos-Vazquez et al, 2014; Coppalle et al, 2019). The use of global positioning system (GPS) technology to measure players’ locomotor activity profiles during matches and training has become prevalent in professional football (SuarezArrones et al, 2015; Torreno et al, 2016; Bowen et al, 2020), and GPS-based parameters (i.e., distance, speed) are established to objectively quantify external loads
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