A comparison of lower limb stiffness and mechanical muscle function in ACL-reconstructed, elite, and adolescent alpine ski racers/ski cross athletes
Bibliographic record
Abstract
The aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed (ACLR), elite (ELITE), and adolescent (ADOL) alpine ski racers and ski cross athletes. Alpine ski racers/ski crossers (ACLR: n = 12, age = 26.7 ± 3.8 years; ELITE: n = 12, age = 23.9 ± 3.0 years; ADOL: n = 12, age = 17.8 ± 0.7 years; females: n = 6 per group, males: n = 6 per group) performed 5 maximal countermovement jumps (CMJs) and 5 squat jumps. The ground reaction forces for each limb were analyzed using dual force plate recording to obtain body center of mass (BCM) velocity, displacement, and power. The eccentric deceleration (ECC) and concentric phases were determined from BCM velocity. CMJ net concentric and ECC impulses were calculated (body mass normalized) along with the peak and mean BCM power and maximal vertical jump height. CMJ lower limb stiffness (LLS) was determined by the slope of the ground reaction forces vs. the BCM displacement curve over the ECC phase. Concentric and ECC asymmetry indices were calculated for each leg, and the left vs. right LLS was compared. Outcome measures (reported as mean ± SD) calculated as a 5-jump mean were normalized to body mass and compared using an analysis of variance. No between-group differences were found for peak and mean power or jump heights. There were no group differences for LLS or net concentric phase impulse, but the net ECC impulse was lower in the ADOL group compared with ELITE skiers (ADOL: 1.33 ± 0.32 Ns/kg; ELITE: 1.59 ± 0.16 Ns/kg; p < 0.05). Although no group differences were found for ECC asymmetry indices, a group × limb interaction was found for LLS (p < 0.01), which was systematically higher in the right vs. the left limb of ADOL skiers (right: 54.1 ± 17.9 N/m/kg; left: 48.7 ± 15.7 N/m/kg; p < 0.01). ADOL skiers demonstrated decreased ECC impulse and systematic right limb dominance in LLS compared with ACLR and ELITE skiers. The implication of these findings for injury and performance are unknown, but further investigation into these potential relationships is warranted.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".