Brief Summary
Hamstring strains are common in soccer (24% of injuries) and haven't decreased. Sprinting, stressing hamstrings during late swing, is a major cause, especially at high speeds (>25 km/h, >80% max sprint speed). Consistent maximal sprint speed (MSS) training may prevent these injuries like a "vaccine," as sprinting uniquely activates hamstrings. Too little or too much MSS exposure increases injury risk, especially sudden increases in high-speed running. Understanding how high-speed running affects risk is key to prevention, as it mimics the injury mechanism. Prior studies on sprint-related activity showed hamstring function and running changes but focused on single risk factors and included fatigue. In this study, the authors examine how repeated high-speed sprints (without significant fatigue) acutely affect sprint performance and multiple hamstring injury risk factors in amateur soccer players.
The authors observed how a single group of amateur soccer players, 15 players in total (age, 21.0 ± 1.3 years), responded to a high-volume maximal sprint speed effort (H-VMSSE) over 72 hours. Players were familiarised with all assessments used the week prior to the H-VMSSE. Changes were assessed in sprint performance (10/30m times, horizontal force/velocity), modifiable hamstring injury risk factors (strength, hip/hamstring flexibility, dynamic lumbo-pelvic control), and muscle damage indicators (soreness, creatine kinase) using a comprehensive soccer-specific approach. Measurements were taken before and at 24, 48, and 72 hours post-H-VMSSE by the same person. The 72-hour recovery period was chosen due to the potentially high demands of the sprinting. Figure 1 illustrates the study design. For more information on the H-VMSSE or any of the assessments, please visit the article.
Results
H-VMSSE
During the protocol, 30-meter time performances indicated low fatigue levels, which aligned with the author’s expectations (players repeatedly reached >95% max speed due to 3min rest between sprints).
Muscle Damage Proxy Markers
Every time point assessed showed significant large-to-moderate increases in serum CK levels, with a peak observed 24 hours after H-VMSSE. Perceived hamstring muscle soreness increased significantly after H-VMSSE and peaked at 48 hours.
HSI Risk Factors
Nonsignificant reductions in ROM were observed whilst small-to-moderate decreases in posterior chain muscle strength were detected until 48hrs post. Dynamic lumbo-pelvic control, measured as an increase in anterior pelvic tilt during maximal speed phase of sprint, showed nonsignificant persistent small changes from baseline to 72 hours post.
Sprint Performance Related Factors
Statistically significant small-to-moderate increases from baseline were found in 10 and 30-meter sprint times at 48 hours after H-VMSSE. At 72 hours, moderate quasi-significant and significant increases from baseline were found in 10 and 30-meter sprint times.
This study uniquely examined how multiple hamstring injury risk factors changed after a high-volume maximal sprint speed protocol, which mimics a key injury mechanism in soccer. This protocol likely exposed players to potentially risky levels of maximal sprinting. The H-VMSSE led to reduced sprint performance and altered hamstring injury risk factors. Specifically, players showed decreased sprint speed and force production at high speeds for days afterward. Hamstring strength also declined, and muscle damage indicators rose, suggesting muscle damage occurred. Finally, players showed a trend towards increased anterior pelvic tilt during sprinting post-exercise, indicating potential structural changes. High-volume sprinting can thus impact both performance and anatomical alignment during sprinting.
Since consistent maximal sprint training is crucial for preparing players for high-speed game situations, understanding these individual reactions is vital. The authors suggest adopting a soccer-specific, multi-faceted approach allowing for personalised recovery and injury prevention plans that optimise both performance and safety. In turn, this could enable tailored maximal sprint training based on individual risk profiles, acting as a precise "vaccine" rather than a potentially harmful “poison." Measuring and monitoring the posterior chain strength of an athlete is key when individualising both on-field and off-field exercise prescription. KT360 provides clinicians with the ability to not only assess overall posterior chain strength but also segment force vectors to pinpoint asymmetries and deficiencies associated with HSI risk. To learn more about how KT360 could be utilised in HSI risk mitigation, please contact info@kangatech.com.