Author Identifier (ORCID)
Abstract
Background: Peak braking velocity (PBV) during the countermovement jump (CMJ) is used to describe descent strategy, but its interpretation is affected by countermovement depth. This study introduced free-fall normalised peak braking velocity (PBVFF), a dimensionless index expressing PBV relative to the displacement-specific theoretical free-fall velocity limit, and evaluated its reliability, performance associations and ranking consequences. Methods: Seventy injury-free male academy footballers (18.7 ± 1.6 years) performed three maximal hands-on-hips CMJs on dual force plates. Using retrospective observational routine monitoring data, one representative testing day per athlete was analysed. Two PBVFF variants were examined: PBVFF normalised to countermovement depth (PBVFFCMD) and PBVFF normalised to displacement at PBV (PBVFFPBV_d). Reliability was assessed using coefficient of variation and two-way mixed-effects intraclass correlation coefficients. Associations with modified reactive strength index (mRSI) and jump height (JH) were assessed using Pearson correlations, Benjamini–Hochberg false discovery rate correction and partial correlations controlling for JH. Ranking effects were examined using Spearman rank correlations, Kendall’s coefficient of concordance and absolute rank shifts. Results: PBVFFCMD showed reliability comparable to raw PBV, with a pooled coefficient of variation of 5.81% versus 6.75% and three-trial intraclass correlation coefficients of 0.865 versus 0.888, respectively. PBVFFCMD was more strongly associated with mRSI than raw PBV (r = 0.573 versus r = 0.231). After controlling for JH, the association between raw PBV and mRSI reversed direction (partial r = − 0.266), whereas the association for PBVFFCMD remained positive (partial r = 0.531). PBVFFPBV_d showed similar but weaker associations with mRSI (r = 0.430; partial r = 0.438). Switching from raw PBV to PBVFFCMD reclassified 46% of athletes by at least 10 ranking positions. Conclusions: PBVFF provides a depth-contextualised interpretation of CMJ descent strategy without compromising within-session reliability. PBVFFCMD appears particularly practical because it can be derived from commonly exported variables and may improve athlete monitoring by reducing misinterpretation driven by countermovement-depth and anthropometric differences. It should complement, rather than replace, established force–time and performance metrics. Trial registration: Not applicable.
Keywords
Countermovement depth, Eccentric velocity, Force plate monitoring, Negative velocity, Vertical jump
Document Type
Journal Article
Date of Publication
12-1-2026
Article Number
369
E-ISSN
20521847
Volume
18
Issue
1
Publication Title
BMC Sports Science, Medicine and Rehabilitation
Publisher
Springer
School
School of Medical and Health Sciences
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
Kruczek, K., Rebelo, A., Lake, J., & Nowak, M. (2026). Free-fall normalised peak braking velocity for countermovement jump monitoring. BMC Sports Science, Medicine and Rehabilitation, 18, Article 369. https://doi.org/10.1186/s13102-026-01920-5