{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T06:58:26Z","timestamp":1785308306144,"version":"3.55.0"},"reference-count":35,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T00:00:00Z","timestamp":1785283200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Bioeng. Biotechnol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Reactive strength index (RSI) is widely used in drop-jump testing, but the score alone does not show how the landing-to-take-off phase is organized.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This study examined whether RSI in male volleyball drop jumps can be interpreted more clearly by combining field-accessible performance metrics with time-continuous knee-joint biomechanical waveforms.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Forty-four male volleyball participants were classified as trained athletes (n = 22) or recreational participants (n = 22). Each completed 30-cm drop jumps using force platforms and three-dimensional motion capture. Field outcomes included jump height, contact time, RSI, and countermovement depth. Laboratory outcomes included dominant-limb knee angle, moment, and power waveforms, with supplementary lower-limb peak joint and work-distribution outcomes. Discrete outcomes were analyzed with mixed models and covariate-adjusted models; waveforms were compared in Python using one-dimensional statistical parametric mapping, with supplementary body mass-normalized kinetic waveform analyses.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Compared with recreational participants, trained athletes had shorter contact time (adjusted \u03b2 = \u22120.093\u00a0s, 95% CI: \u22120.157 to \u22120.030), smaller countermovement depth (adjusted \u03b2 = \u22127.03 cm, 95% CI: \u221211.98 to \u22122.08), and higher RSI (adjusted \u03b2 = 0.273\u00a0m\/s, 95% CI: 0.131\u20130.415). Knee propulsive work was higher before anthropometric adjustment, whereas the adjusted result was statistically inconclusive. Waveform analysis showed less knee flexion across most of contact, greater knee moment during middle-to-late contact, and phase-specific knee-power differences.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Higher RSI in trained male volleyball athletes was associated with a compact field-level landing-rebound pattern, defined by shorter contact time and smaller countermovement depth, supported by lower-limb discrete outcomes and knee-joint waveform features rather than a single biomechanical feature. Combining field-accessible metrics with lower-limb biomechanical analysis may provide a more interpretable profile of reactive strength in volleyball drop jumps.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fbioe.2026.1886944","type":"journal-article","created":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T05:58:34Z","timestamp":1785304714000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Field-to-laboratory biomechanical profiling of reactive strength index in male volleyball drop jumps"],"prefix":"10.3389","volume":"14","author":[{"given":"Di","family":"Lu","sequence":"first","affiliation":[{"name":"School of Physical Education, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yueming","family":"Li","sequence":"additional","affiliation":[{"name":"Sports Training Institute, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tianyuan","family":"He","sequence":"additional","affiliation":[{"name":"Sports Training Institute, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiaxin","family":"He","sequence":"additional","affiliation":[{"name":"Sports Training Institute, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Key Laboratory of Human-Computer Intelligent Interaction for Athletic Performance and Health Promotion, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Guangdong Provincial Key Laboratory of Human Sports Performance Science","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jian","family":"Sun","sequence":"additional","affiliation":[{"name":"Sports Training Institute, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Key Laboratory of Human-Computer Intelligent Interaction for Athletic Performance and Health Promotion, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Guangdong Provincial Key Laboratory of Human Sports Performance Science","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Duanying","family":"Li","sequence":"additional","affiliation":[{"name":"Sports Training Institute, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Key Laboratory of Human-Computer Intelligent Interaction for Athletic Performance and Health Promotion, Guangzhou Sport University","place":["Guangzhou, Guangdong, China"]},{"name":"Guangdong Provincial Key Laboratory of Human Sports Performance Science","place":["Guangzhou, Guangdong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,29]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"217","DOI":"10.2165\/00007256-199826040-00002","article-title":"Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine","volume":"26","author":"Atkinson","year":"1998","journal-title":"Sports Med."},{"key":"B2","doi-asserted-by":"publisher","first-page":"437","DOI":"10.1097\/00005768-199903000-00013","article-title":"A comparison of methods for analyzing drop jump performance","volume":"31","author":"Baca","year":"1999","journal-title":"Med. 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