As a Part 2 of a blog post about High-Speed Running and Sprinting in Professional Football, I would like to go further and discuss about the impact of injuries on these crucial parameters of the football game. Due to the great interest of Strength & Conditioning, Football and Rehab coaches in this topic, a series of blogs dedicated to high intensity activities in football, among which high-speed running and sprinting take a special place, continues. This time I would like to draw your attention to a phenomenal study by Whiteley et al. (2020): Match High-Speed Running Distances are often suppressed after return form hamstring strain injury in professional footballers published in Sports Health.
Hamstring Strain Injuries (HSI) are known as “the biggest enemy” of professional football players. With an incidence of 3.7 injuries per 1000 hours of play and 0.92 injuries per 1000 hours of training, HSIs represent the most common muscle injuries in football. In addition to significant squad and financial losses for the club, injuries could highly affect performance and motivation of the injured player. Due to the high incidence, rehabilitation and prevention of HSI have a special attention of sports scientists and sports practitioners who work with football players on a daily basis. The quality and success of these treatments are usually evaluated through the (1) time-loss and (2) re-injury rate. Time-loss defines the time frame from the moment the injury occurs to the return to team training or competition. However, with the advancement of technology for monitoring training and competition performance (GPS, LPS and Video-based analysis), it is now possible to take a deeper look at the effects of injury even after returning to the competition. Tracking the time lost from training (as the main representative of the injury impact on the player) excludes the negative effects of the injury after returning to training and playing (residual injury effect as we like to call it), which misinterprets the real level of physical abilities of the player. Although the player is back to training and competition and does not require any additional medical care, it is necessary to determine whether his performance is at the pre-injury level. Therefore, the idea of Return to High Performance encompasses a longer time frame and more adequately defines the negative effects of injury, as players can “carry” an injury over an extended period of time. This way of treating the problem could be especially important in severe injuries and chronic conditions.
Sprinting is a reported mechanism of HSI in about 70% of cases. For this reason, it would be very logical to pay special attention to High-Speed running (HSR) and Sprinting during the rehabilitation process as well as after returning to team sessions. High-intensity activities, including running at velocities close to maximal, are activities during which key moments of the game take place and which can differentiate between winners and losers. The inability of an individual to successfully and sufficiently participate in these activities during the match, can significantly affect team performance. For that reason, football coaches are primarily interested in returning the player to the pre-injury level, and not just returning to the team work. HSR and sprinting are an important part of this puzzle due to their undeniable impact on performance but also as a significant factor in HSI prevention. Due to all the above, the total distances covered (in meters) at speeds that meet criteria of HSR (>19.8 km/h) and sprinting (>25.2 km/H) could be considered as important parameters in the assessment of long-term effects of HSI and other injuries.
Whiteley et al. (2020) observed 15 professional football players with HSI. Total distances of HSR (>19.8 km/h) of each player before injury during at least 5 games (median 15 games) were collected and analyzed (average and cummulative values). Due to the large variability among players, the results were observed individually. It is interesting that the results ranged from 75 to as much as 1000m, indicating the differences in abilities, positional differences, the influence of tactics, opponent, etc. The results obtained, especially for players who did not show much variability in results from match to match, were used to predict the results in subsequent games (as if the injury had not occurred). After comparing the hypothetically predicted results and the real post-injury values, almost 50% of the players (7 out of 15) achieved significantly less total HSR distance, during the next 15 games! Also, the duration of the residual injury effects has not been determined, since the players failed to regain their initial values by the end of the study! There is a possibility that the values after the injury became their “new normal”, and that the injury left long-term consequences that affect the entire career of the athlete. The results clearly indicate that a “ability to perform” might be a more appropriate approach when making a decision to return to play and evaluating rehabilitation process, compared to a “no need for additional medical care” approach. Although the study has several limiting factors, such as the duration of the study, the number of subjects, ignorance of rehabilitation treatments, severity of injury, etc., it is still possible to draw certain conclusions about the impact of HSI after returning to competition.
Simple take-home messages from this blog:
1. Approximately half of professional footballers can reduce their competitive performance after hamstring strain injury, when the volume of running at high intensity is observed.
2. Monitoring high-intensity training and match activities (GPS, LPS, Video-based analysis) can give a clearer picture of the real situation to S&C coaches and Athletic trainers, and help them make decisions about returning to competition.
3. In the late stages of recovery, special attention should be paid to high-intensity activities, bearing in mind that HSR and Sprint represent the most common mechanism of HSI. It is realistic to expect that players consciously or unconsciously avoid these activities, which are of key importance in football.
4. Players’ fear of participating in high-intensity activities may exist long after the rehabilitation process is complete. Player education and adequate progression can help in the returning player to pre-injury level.
5. S&C and AT can view the volume of HSR and Sprint during the match as another tool to evaluate rehabilitation process and, in accordance with the outcome, make the necessary changes and additions to late-phase rehab. However, individual differences should be taken into account.
6. Keep in mind that the rehabilitation process is not completely over after the player returns to team sessions. Additional individual work, especially in the first weeks after returning to the team, can significantly shorten the time to return to the pre-injury level.
7. The last phase of rehabilitation is not identical for every injured player. With the understanding that this is the phase in which the player prepares to successfully participate in the competition, it is necessary to individualize the approach while respecting its previous values. So, another important function of load monitoring is to obtain the reference values (considering on-field conditioning) that could be used as guidance if an injury occurs.