Elite Football Injury Risk Explained
Sprinting x Hamstring Injuries
By Dr. Martin Buchheit, Head of Performance Research, Maxime Settembre, Data Scientist, Karim Hader, Performance Strategist and Dr. Derek McHugh, Head of Data Science
Earlier this year, we shared a paper titled Elite Football Injury Risk Explained followed by a piece focusing on hamstring strains as part of an on-going series related to injury risk from the Performance Intelligence Research Initiative (PIRI).
Hamstring strain injuries remain the most prevalent time loss injuries in professional soccer. While their relative occurrence may have decreased slightly in relation to the likely increased match demands over the past decade, practitioners are still seeking mitigation strategies both in the gym and on the pitch.
Next in our research series, we study the association between the occurrence of near-to-maximal sprinting speed (MSS) running bouts during training and hamstring injury rate during the consecutive match of the same turnaround in elite soccer.
Recent studies have shown relationships between hamstring strain injuries and near-to-MSS exposures both in Australian Rules Football and Gaelic Football players, where both under- and over near-to-MSS exposures were associated with higher injury rates, suggesting the existence of an optimal chronic “dose” (i.e., number of weekly exposure) and/or monthly cumulative distance. However, this optimal chronic dose is likely specific to each population and context and without clear programming guidelines, it is difficult to offer recommendations for all practitioners based on these two studies.
To our knowledge, our new research study is the first study to examine both the occurrence of near-to-MSS running bouts within typical turnaround in elite football, and the association between the programming of near-to-maximal speed exposures and match non-contact time loss hamstring injury rates.
Our study analyzed data from 36 team-seasons belonging to 16 elite teams (total of 627 players participating in 5052 training session days) performing in top leagues including the English Premier League (EPL), the Italian Serie A, the Bundesliga, the Scottish Premiership, the Major Soccer league (MLS) and the Dutch Eredivisie from January 2018 to December 2022.
In our research paper, we openly share our approach and methodology and provide results based on varying MSS exposure rates and turnaround levels.
We found linear correlations between the number of training sequences with near-to-MSS exposures and the length of the turnarounds – with the lower the speed thresholds, the greater the number (and proportion) of near-to-MSS exposures (Figure 1).
Figure 1: Correlations coefficients were 0.98 (0.82;1.00), 0.98 (0.82;1.00) and 0.95 (0.60;0.99) for >85%, >90% and >95% MSS running bouts occurrences, respectively.
For some of the turnarounds, there were no match hamstring injuries when players were exposed to running bouts >95% MSS during the training session days leading to matches, vs. when there was no exposures. In contrast, this was not apparent when considering running bouts only >85% or >90% MSS (see more details in the full paper).
Finally, there were no hamstring injuries when >95% MSS exposures occurred at D-2, while in contrast, injuries still happened when players were not exposed at all, or when these exposures occurred at D-3 and/or earlier within the turnaround (Figure 2).
Figure 2. Match hamstring injury rate (with 95% confidence intervals, and per 1000 player-turnarounds) in relation to the training session day(s) of the turnaround when running bouts >95% MSS occurred. *Note that D-3 is an aggregation of all training session days of the turnaround before D-3 included (e.g., D-3 summarizes occurrences from D-6 to D-3 for a 7-d turnaround, see methods). Data presented here are from 4- to 8-d turnarounds pooled together; since there is no D-3 data during 3-d turnarounds, data from the entire 3-d turnarounds is excluded from this analysis.
The full paper is currently under review for publishing but the complete text can be accessed now on the free archives. In it, we discuss our findings, areas of debate, limitations, and practical applications.
Here is an overview of the main findings:
- The large majority of players arrived at the match without having been exposed to near-to-MSS running bouts during the training days of the current turnaround (60% for >85% MSS, 76% for >90% MSS and 90% for >95% MSS).
- There were linear correlations between the number of training-sequences including near-to-MSS running exposures, and the length of the turnarounds.
- Reaching >95% of MSS during training was more frequently associated with lower rates of match hamstring injuries than when only reaching >85% or >90%.
- While association doesn’t imply causality, programming 95% exposures at D-2 may be the more relevant strategy to decrease the incidence of non-contact match hamstring injuries than no programming exposures at all, or having those exposures at D-3 and/or earlier in week.
- If D-2 was to be the most appropriate day for near-to-MSS exposures, the programming of the other days of the week needs to be tailored accordingly (i.e., D-4 and D-3), so that players don’t reach D-2 with excessive levels of neuromuscular fatigue – not to be at higher risk of hamstring injuries during the exposures themselves.
If you haven’t yet read the first part of our series on injury risk, you can find them here: Elite Football Injury Risk Explained (part 1) and Elite Football Injury Risk Explained, Part 2: Further Insights into Hamstring Strains (part 2).
You can read the final research paper here.