Introduction: There is controversy in the literature in regards of the link between training load and injury rate. Thus, the aims of this non-interventional study were to evaluate relationships between pre-season training load with biochemical markers, injury incidence and performance during the first month of the competitive period in professional soccer players. Materials and Methods: Healthy professional soccer players were enrolled in this study over two pre-season periods. Data sets were available from 26 players during the first season (2014–2015) and 24 players during the second season (2015–2016) who completed two pre-season periods (6 weeks each). External training load was assessed from all athletes during training using Global Positioning System (GPS). Internal training load was monitored after each training session using rate of perceived exertion (RPE). Before and after each pre-season, blood samples were taken to determine plasma lactate dehydrogenase (LDH), creatine kinase (CK) and C-reactive protein (CRP). Injury incidence and overall performance (ranking of the team after the first five official games of the championship) were recorded for both seasons separately. Results: There was no statistically significant difference in mean RPE values of the two-preparation periods (2737 ± 452 and 2629 ± 786 AU, p = 0.492). The correlational analysis did not reveal significant associations between internal and external training load (RPE and GPS data) and biological markers. There was a significant positive correlation between RPE and LDH during the 2015/2016 season (r = 0.974, p = 0.001). In addition, a significant negative correlation was found between total distance >20 km/h and CRP during the 2015–2016 season (r = -0.863, p = 0.027). The injury rates for the two seasons were 1.76 and 1.06 per 1000 h exposure for the 2014–2015 and 2015–2016 seasons, respectively (p = 0.127). Conclusion: Our study showed that pre-season training load is not associated with overall team performance. This association is most likely multifactorial and other factors (e.g., technical and tactical level of the team, opponents, environment) may play an important role for the collective team performance. Our findings may help coaches to better prepare their athletes during pre-season.

On physical fitness parameters and injuries occurrence in young elite soccer players. Fifty-two elite young soccer players (13–14 years) were divided on a randomized order into experimental group (EG, n = 26) and control group (CG, n = 26). For EG, 2 to 3 sessions of strength training (90 minutes) were introduced weekly in their training program for 12 weeks (4 × 3 weeks separated by 1-week recovery). Sprint tests (10-20-30 m), T-test time, and jumping tests were measured at the start (T0), at the middle (T1), and at the end of the experiment period (T2). The injury rate was recorded by the medical and fitness training staff throughout the soccer season. Compared to CG, EG performed significantly better in sprint running and T-test time at T2 (p < 0.01). Similarly, the improvement amount for jumping tests was significantly greater (p ≤ 0.05) in EG than in CG. A total of 17 injuries were recorded over the soccer season. The rate was higher in CG (13 injuries) than in training group (4 injuries). This study showed that strength training accurately and efficiently scheduled in youth soccer players, induced performance improvement, and reduced the rate of injuries....

This study is aimed to perform and compare maximal concentric isokinetic trunk extension and flexion torques and powers between high-level athletes and a control population. In addition, the ratio of isokinetic trunk extension and flexion torques was measured, and compared between groups. Eighteen high-level male athletes and 15 male nonathletes without low back pain were recruited. Subjects performed isokinetic trunk extension and flexion at 60°/sec, 90°/sec, and 120°/sec through a maximal range of motion in a dynamometer. Trunk extension torque of athletes was significantly higher than in nonathletes at 60°/sec and 90°/sec but not at 120°/sec. Trunk extension power of athletes was significantly higher than the control group at 90°/sec and 120°/sec but not at 60°/sec. There was no difference between the athlete and nonathlete groups in respect of trunk flexion torque or power at any angular velocity. Consequently, the ratio of trunk flexion to extension strength was greater in nonathletes than in athletes. Trunk extension and flexion torques tended to decrease, and trunk extension and flexion powers tended to increase, with increasing angular velocity. High-level athletes seem to display preferentially greater trunk extension strength and power in comparison with trunk flexion strength, compared to nonathletes. This could be caused by the use of strength training exercises such as squats and deadlifts, or it may be associated with greater athletic performance.