Evaluation of Two Methods of the Jump Float Serve in Volleyball
Bibliographic record
Abstract
A novel jump-focused (JF) technique of the jump float serve was compared with the conventionally used contact-focused (CF) method. Seven elite male (height: 195 ± 6 cm) and two elite female (height: 181 and 182 cm) volleyball players were videoed at 60 Hz performing both techniques. Horizontal and vertical ball contact coordinates, pre- and postcontact ball velocities, and initial projection angles were determined. The JF technique resulted in a significantly higher mean contact height, t(8) = 4.12, p = .006, d = 0.72, initial serve speed, t(8) = 4.71, p = .006, d = 2.03, and significantly flatter initial projection angle, t(8) = 2.53, p = .036, d = 0.63, relative to the CF technique. The precontact vertical ball velocity was also significantly higher, t(8) = 8.04, p = .004, d = 2.86. The higher precontact vertical ball velocity suggests it is more difficult to make accurate contact with the ball during the JF technique. However, this method promotes a more favorable ball trajectory and a greater initial serve speed. When combining the random lateral movement patterns inherent in any float serve, with the reduced flight time associated with the JF technique, a more challenging passing scenario can be presented to the defensive team in comparison with the current CF technique.
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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 | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".