A Systematic Review of the Relationship between Workload and Injury Risk of Professional Male Soccer Players

Match workload and international travel associated with (ACL) injuries in professional women's football

Women's football has grown in popularity, competitiveness and professionalism, increasing the demands placed on players and their injury risk. This study aimed to identify differences in the match workload and international travel between injured and non-injured professional women's footballers. The study was conducted as an observational, retrospective, case-control study over two football seasons (2021/2022 and 2022/2023) in four top-tier European women's football leagues. Fifty-eight professional women football players (81 injuries) formed the injury group and were matched with 81 elite women football players (162 non-injuries), from the same league, to form the control group. For each injury, cumulative match workload (minutes played, appearances, days between matches, rest) and international travel (distances, time, time zones crossed) were calculated over a 28-day period preceding the injury, for both the injured players and matched controls. The injured group had a higher number of instances of less than 5 days between matches compared to the controls (p = 0.03, effect size = 0.3, small). The anterior cruciate ligament injury group made more appearances (p = 0.09, effect size = 0.8, moderate), had more instances of less than 5 days between matches (p = 0.09, effect size = 0.8, moderate) and had less rest time (p = 0.12, effect size = 0.8, moderate) than the control group. No meaningful differences were observed between the hamstring injury group and the control group. These findings underscore the importance of careful consideration when developing match fixture schedules in elite women's football, particularly concerning the number of matches scheduled in a short period. Strategies to increase rest and recovery are recommended to safeguard players against injuries.

Potential financial loss and risk factors for hamstring muscle injuries in elite male Brazilian soccer players: a season-long prospective cohort pilot study

Purpose

The aim of this pilot study was to analyze the potential financial loss and a range of potential risk factors for hamstring muscle injuries in elite Brazilian soccer.

Methods

Thirty-four male players (age: 25 ± 6 years; stature: 180 ± 8 cm; body mass: 78 ± 9 kg; minutes played in matches: 2243 ± 1423 min) from an elite professional soccer club were monitored during a 12-month season. Muscle injury was identified by magnetic resonance imaging and the severity was defined according to the number of days away: minimal (1-3 days), mild (4-7 days), moderate (8-28 days), severe (>28 days). Potential financial loss due to the team's under achievements was determined. Dorsiflexion range of motion, eccentric knee flexor strength and isokinetic tests were performed during the pre-season. Association between dependent variables and the occurrence of injury was evaluated.

Results

Nine hamstring muscle injuries with moderate severity were found in 8 athletes. Recovery time was 22 days off the field on average. Potential financial loss was $-43.2 million USD and earnings on merit money was 21%. Previous injury, increased flexor deficit 60° /sec and increased flexor fatigue index 300°/sec were all associated with a greater chance of hamstring muscle injury. Ankle dorsiflexion range of motion was significantly lower in the injured group (35.6 ± 3° vs. 39.1 ± 4.9°; p = 0.017, effect size = -0.74).

Conclusion

High financial burden was found in elite Brazilian soccer during one full season. Injured athletes had high hamstring fatigue index, knee flexor strength deficit, ankle range of motion restriction and previous hamstring muscle injury when compared to non-injured athletes. Therefore, preventive approaches in professional soccer players with previous hamstring injuries should be a priority.

Analyzing activity and injury risk in elite curling athletes: seven workload monitoring metrics from session-RPE

Objective

The study aimed to compare the differences in the performance of seven session-rating of perceived exertion (RPE)-derived metrics (coupled and uncoupled acute: chronic workload ratio (ACWR), weekly ratio of workload change, monotony, standard deviation of weekly workload change, exponentially weighted moving average (EWMA), and robust exponential decreasing index (REDI)) in classifying the performance of an injury prediction model after taking into account the time series (no latency, 5-day latency, and 10-day latency).

Design

The study documented the RPE of eight curlers in their daily training routine for 211 days prior to the Olympic Games.

Methods

Seven Session-RPE (sRPE)-derived metrics were used to build models at three time series nodes using logistic regression and multilayer perceptron. Receiver operating characteristic plots were plotted to evaluate the model's performance.

Results

Among the seven sRPE-derived metrics multilayer perceptron models, the model without time delay (same-day load corresponding to same-day injury) exhibited the highest average classification performance (86.5%, AUC = 0.773). EMWA and REDI demonstrated the best classification performance (84.4%, p < 0.001). Notably, EMWA achieved the highest classifying accuracy in the no-delay time series (90.0%, AUC = 0.899), followed by the weekly load change rate under the 5-day delay time series (88.9%, AUC = 0.841).

Conclusion

EWMA without delay is a more sensitive indicator for detecting injury risk.

The Impact of Match Workload and International Travel on Injuries in Professional Men's Football

There are concerns over the impact of the congested international match calendar on professional footballers' physical and mental well-being, and injury susceptibility. This study aimed to determine whether there were differences in match workload and international travel between injured and non-injured male football players over two elite competition seasons. An observational, retrospective, case-control study was conducted using data from the 2021/2022 and 2022/2023 seasons of five top-tier European men's football leagues. Student t-tests were used to compare cumulative match workload and international travel data over a 28-day period preceding 1270 injuries and 2540 controls. There were significant differences in match workload and international travel variables between the injured groups (all injuries and hamstring injuries) and the control group. Match workload variables were higher (p < 0.01), recovery variables lower (p < 0.01), and international travel variables higher (p < 0.01). An overload of match workload and international travel contribute to increased injury susceptibility in professional men's football. This emphasizes the need to address international match calendar concerns, including the number of games per season, the frequency of back-to-back games, and international travel requirements. Additionally, the findings highlight the importance of monitoring player match workloads, and implementing squad rotations and tailored training programs to mitigate injury risks.

Economic impact of muscle injury rate and hamstring strain injuries in professional football clubs. Evidence from LaLiga

The aims of this study were: 1) to describe the total muscular injuries, and specifically HSIs, and their corresponding missed matches; 2) to analyse their economic impact; and 3) to estimate the loss of incomes due to TV rights, in first division clubs from LaLigaTM depending on the expected and actual ranking position during the 2018/2019 season. To do that, a cross-sectional study for season 18/19 and for all players of the 20 Spanish professional football clubs was performed. The economic impact of injuries was estimated considering the missed matches and salary cost of all players and the audio-visual income loss was estimated considering the Spanish Royal Decree of Law (RDL 5/2015). The high number of muscular (270) and hamstring injuries (57) implies a high cost for professional first division football clubs, specifically € 365,811 per month for the former and € 47,388 per month for the latter. In addition, reaching a worse than expected position in LaLigaTM ranking involved a loss of 45,2 million € in TV rights incomes. The high cost of muscle injuries in first division teams justifies the need for multidisciplinary teams that are capable of reducing the number of injuries as well as recovery times.

Workload Risk Factors for Pitching-Related Injuries in High School Baseball Pitchers

BACKGROUND

Pitch counts are only one measure of the true workload of baseball pitchers. Newer research indicates that workload measurement and prevention of injury must include additional factors. Thus, current monitoring systems gauging pitcher workload may be considered inadequate.

PURPOSE/HYPOTHESIS

The purpose of this study was to develop a novel method to determine workload in baseball pitchers and improve processes for prevention of throwing-related injuries. It was hypothesized that our pitching workload model would better predict throwing-related injuries occurring throughout the baseball season than a standard pitch count model.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This prospective observational study was conducted at an academic medical center and community baseball fields during the 2019 to 2023 seasons. Pitchers aged 13 to 18 years were monitored for pitching-related injuries and workload (which included pitching velocity; intensity, using preseason and in-season velocity as a marker of effort; and pitch counts).

RESULTS

A total of 71 pitchers had 313 recorded pitcher outings, 11 pitching-related injuries, and 24,228 pitches thrown. Gameday pitch counts for all pitchers ranged from 19 to 219 (mean, 77.5 ± 41.0). Velocity ranged from 46.8 to 85.7 mph (mean, 71.3 ± 5.8 mph). Intensity ranged from 0.7 to 1.3 (mean, 1.0 ± 0.08). The mean workload was 74.7 ± 40.1 for all pitchers. Risk factors significant for injury included throwing at a higher velocity in game (P = .001), increased intensity (eg, an increase in mean velocity thrown from preseason to in-season; P < .001), and being an older pitcher (P = .014). No differences were found for workload between injured and noninjured pitchers because the analysis was underpowered.

CONCLUSION

Our workload model indicated that throwing at a higher velocity, throwing at a higher intensity, and older age were risk factors for injury. Thus, this novel workload model should be considered as a means to identify pitchers who may be at greater risk for injury.

Acute pre- and post-competitive soccer match-play changes in neuromuscular factors, physical performance, and muscle response in youth male players

There is a paucity of literature analyzing the impact of fatigue from actual competitive soccer match-play on measures of neuromuscular function and muscle damage markers in youth players. Aims The main purpose was to analyze the acute pre- and post-competitive soccer match-play changes in measures of landing mechanics, stretch-shortening cycle capability, physical performance, muscle damage, and match intensity. A secondary purpose was to explore whether the players' maturity status and chronological age were associated with post-soccer match-play responses. Methods Thirty-two male youth outfield soccer players from two chronological competition age groups (U14 and U16) were assessed pre-and post-competitive soccer match-play for 2D dynamic knee valgus at landing (DKV), leg stiffness, reactive strength index, 20 m sprint time, CMJ-Abalakov jump height, creatine kinase and urea activity and visual analogue scale for muscle soreness (VAS). Players' maturity status was also estimated using a previously validated regression equation. Results There were statistically significant (p < 0.05) post-competitive soccer match-play impairments in all measures of stretch-shortening cycle capability and muscle damage markers assessed irrespective of the age group. Likewise, significant post-match play alterations in landing mechanics (DKV of the dominant leg) and physical performance (sprint time and jump height) scores were documented for the U14 players. Significant interactions between maturity and landing mechanics and VAS responses to competitive soccer match-play were also found whereby more mature players demonstrated larger post-match changes. Conclusion The findings of this study suggest the existence of a negative influence of competitive match-play on neuromuscular function and muscle damage in youth soccer.

Monitoring load, wellness, and psychological variables in female and male youth national team football players during international and domestic playing periods

Aim

To study differences in total load exposure, wellness, and psychological variables in youth female (N = 19) and male (N = 20) national team football players during domestic and international playing periods, respectively.

Procedures

The players filled out questionnaires on well-being, stress, and resilience before and after both playing periods lasting 8 days each. The Hooper index was used to monitor daily wellness levels during both playing periods. The number of training sessions and matches were recorded, and the session rating of perceived exertion was collected. Training load, monotony, and strain were calculated. Daily measurements were used to evaluate in-period changes, and composite scores were used to describe differences between periods.

Results

The international compared to the domestic playing period was for both groups characterized by more matches played, longer field training session durations, and of fewer gym-based sessions (P < 0.05). The male players increased total exposure time (25%; P < 0.05), monotony (P < 0.001), and strain (P < 0.001), which was not changed in the female players. Well-being decreased (P < 0.05) during the international playing period in male players. Stress levels were higher (P < 0.05) for both genders during the international compared to the domestic playing period. During the international playing period, positive correlations were found between the initial levels of stress, and the change in stress (P = 0.03; r2 = 0.12), and between the changes in total load and changes in well-being (P = 0.02; r2 = 0.12), whereas a negative correlation was found between the changes in wellness and stress (P = 0.03; r2 = 0.14).

Conclusion

A playing period characterized by increased match focus, longer field training sessions, and fewer gym-based training activities may lead to changes in the physical and mental profiles of youth national team football players. Alterations to load exposure and wellness may influence mental health. Players with high initial stress levels may be subjected to greater changes compared to other players. Sports scientists and medical staff may benefit from initiating structured monitoring systems to track alterations in physical load and mental health in youth national team players.

Weekly External Load Performance Effects on Sports Injuries of Male Professional Football Players

One of the most challenging issues professional football players face throughout their careers is injuries. Those injuries often result from suboptimal training programs that were not designed according to the players' individual needs. This prospective study aimed to examine in detail the effects of sports injuries on professional football players' weekly external load performances. Thirty-three male professional football players were monitored using 10-Hz Global Positioning System (GPS) units (Apex pro series, StatSports) during an entire season. The variables considered in the analysis were total distance (TD), high-speed running (HSR), accelerations (ACC), and decelerations (DEC). The comparisons were made between the four-week block before injury (-4T), four-week block after return (+4T), and players' season averages (S). Players displayed significantly higher values of TD, HSR, ACC, and DEC in the -4T, compared to the other two moments (+4T and S). Furthermore, the comparison between the +4T and S showed no significant variations in the GPS metrics. It was shown that a significant increase in players' weekly external load performance over a four-week period may have a negative effect on the occurrence of injuries from a professional football standpoint. Future research should consider the effects of injury severity on players' external load variations.