Nordic Hamstring Strength of Highly Trained Youth Football Players and Its Relation to Sprint Performance
Bibliographic record
Abstract
Markovic, G, Sarabon, N, Boban, F, Zoric, I, Jelcic, M, Sos, K, and Scappaticci, M. Nordic hamstring strength of highly trained youth football players and its relation to sprint performance. J Strength Cond Res 34(3): 800-807, 2020-We aimed to characterize Nordic hamstring (NH) strength and bilateral NH strength asymmetry in highly trained youth footballers and to investigate the relationship between NH strength and sprint performance. Twenty-two adult and 133 highly trained youth footballers in the age groups U12-U18 participated in this study. Eccentric hamstring strength was assessed using the NH device. Youth footballers (n = 119) also performed 20-m sprint test. Age-related changes in absolute and relative NH strength, and bilateral NH strength asymmetry were analyzed using 1-way analysis of variance. The linear relationship between relative NH strength and sprint performance was established using a Pearson correlation analysis. Significant age-related increases (F = 3.6-18.9; all p < 0.01) in NH strength were reported for all units except N·kg (F = 1.9; p = 0.08). The largest differences in absolute NH strength were seen between U15 and U16 groups. Bilateral NH strength asymmetry varied from 8 to 16% (F = 1.8; p = 0.09) across all age groups. A large correlation between NH strength and sprint performance was observed (r = -0.52; p < 0.01). Our results indicate that NH strength increases nonlinearly with players' age, with the highest values observed in U16 group. Furthermore, bilateral NH strength asymmetry varied nonsignificantly between 8 and 16%. Finally, 27% of variance of sprint performance of youth footballers could be explained by relative NH strength. The reported NH strength data could be used as normative standards during testing and training of youth football players. Present results also suggest that coaches should pay close attention to eccentric hamstring function in youth footballers.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".