Sprint running mechanics are associated with hamstring strain injury: a 6-month prospective study

Key points

1. 01Each one-point increase in S-MAS was associated with a 33% increase in hamstring strain injury rate (adjusted IRR 1.33, 95% CI 1.01 to 1.76, p=0.044)
2. 02S-MAS scores of 5.5 or above provided a sensitivity of 78.6% and specificity of 65.4% for identifying players who went on to sustain a new injury
3. 03Players with a previous hamstring strain injury had significantly higher S-MAS scores than uninjured players (median 6 vs 5, p=0.007)
4. 04Prospectively injured players had a median S-MAS of 7 compared with 4 in uninjured players (p=0.006)
5. 05The S-MAS is a practical 2D slow-motion video tool with good inter-tester (ICC 0.799) and intra-tester (ICC 0.828) reliability, making it usable in team settings

How it was conducted

Design

Prospective cohort study, 6-month follow-up (June 2022 to March 2024)

Participants

126 professional male outfield footballers from 8 English Football League clubs (Premier League to National League)

Exposure measure

Sprint Mechanics Assessment Score (S-MAS): 12-item qualitative 2D video scoring tool; higher score = more suboptimal mechanics

Primary outcome

New MRI-confirmed sprint-related hamstring strain injury during the 6-month follow-up

Statistical analysis

Poisson regression to calculate incidence rate ratios; adjusted for age and previous hamstring injury; ROC curve for cut-off threshold

Data collection

Maximal 35 m sprint trials filmed at 240 fps; assessed by a single blinded biomechanist

What they found

• 14 of 92 participants (15.2%) sustained a new sprint-related hamstring strain injury during the 6-month follow-up
• Unadjusted IRR for each one-point increase in S-MAS: 1.38 (95% CI 1.06 to 1.79, p=0.017)
• Adjusted IRR (for age and previous injury) for each one-point increase in S-MAS: 1.33 (95% CI 1.01 to 1.76, p=0.044)
• S-MAS cut-off of 5.5: sensitivity 78.6%, specificity 65.4%, area under the ROC curve 0.732
• Median S-MAS in prospectively injured group: 7 (IQR 6 to 7) vs 4 (IQR 2 to 6) in uninjured group (p=0.006, Hedges g=0.22 to 1.37)
• Retrospective analysis: median S-MAS was 5 in previously injured group vs 6 in uninjured group (p=0.007, Hedges g=0.17 to 1.1)
• Categorical S-MAS above 5.5 as predictor: IRR 2.8 (95% CI 0.94 to 8.35, p=0.065) - non-significant

Limitations

• Training and match sprint exposure was not individually monitored; players sustaining non-hamstring severe injuries were excluded from the uninjured group, which may have inadvertently removed players with optimal mechanics who remained injury-prone due to other reasons
• The power calculation used internal pilot data that overlapped with the final analysis sample, introducing a post-hoc element that may slightly inflate effect size precision
• S-MAS validity against 3D motion capture has not yet been formally established
• The specificity of 65.4% at the recommended cut-off means a substantial proportion of uninjured players would screen positive, limiting standalone clinical utility

Why it matters

For patients

Footballers with poor sprint mechanics may face a meaningfully higher risk of hamstring injury, and targeted rehabilitation of running technique could be a worthwhile prevention strategy.

For clinicians

Incorporating S-MAS screening into pre-season and rehabilitation assessments may help identify at-risk players, but sprint mechanics should be evaluated alongside strength, load, and other injury risk factors rather than in isolation.

For readers

This study provides the first prospective evidence from elite football that a simple field-based sprint quality score is independently associated with future hamstring strain injury, supporting its use in practice.