{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,2]],"date-time":"2026-06-02T09:35:40Z","timestamp":1780392940968,"version":"3.54.1"},"reference-count":50,"publisher":"Public Library of Science (PLoS)","issue":"8","license":[{"start":{"date-parts":[[2024,8,16]],"date-time":"2024-08-16T00:00:00Z","timestamp":1723766400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:p>The purpose of this work was to provide a simple method to determine reactive strength during the 6-meter timed hop test (6mTH) and evaluate its association with isokinetic peak torque in patients following anterior cruciate ligament reconstruction (ACLR). Twenty-nine ACLR patients who were at least four months from surgery were included in this analysis. Participants were brought into the laboratory on one occasion to complete functional testing. Quadriceps and hamstring isokinetic testing was completed bilaterally at 60, 180, and 300 deg\u2219s<jats:sup>-1<\/jats:sup>, using extension peak torque from each speed as the outcome measure. The 6mTH was completed bilaterally using a marker-based motion capture system, and reactive strength ratio (RSR) was calculated from the vertical velocity of the pelvis during the test. An adjustment in RSR was made using the velocity of the 6mTH test to account for different strategies employed across participants. Repeated measures correlations were used to determine associations among isokinetic and hop testing variables. A two-way mixed analysis of variance was used to determine differences in isokinetic and hop testing variables between operated and non-operated legs and across male and female participants. Moderate positive associations were found between RSR (and adjusted RSR) and isokinetic peak torque at all speeds (<jats:italic>r<\/jats:italic> = .527 to .577). Mean comparisons showed significant main effects for leg and sex. Patients showed significant deficits in their operated versus non-operated legs in all isokinetic and hop testing variables, yet only isokinetic peak torque and timed hop time showed significant differences across male and female groups. Preliminary results are promising but further development is needed to validate other accessible technologies available to calculate reactive strength during functional testing after ACLR. Pending these developments, the effects of movement strategies, demographics, and levels of participation on RSR can then be explored to translate this simple method to clinical environments.<\/jats:p>","DOI":"10.1371\/journal.pone.0309003","type":"journal-article","created":{"date-parts":[[2024,8,16]],"date-time":"2024-08-16T17:36:33Z","timestamp":1723829793000},"page":"e0309003","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":2,"title":["A hop testing alternative for functional performance following anterior cruciate ligament reconstruction"],"prefix":"10.1371","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7272-0491","authenticated-orcid":true,"given":"Zachary","family":"Ripic","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Letter","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-0849-6701","authenticated-orcid":true,"given":"Brandon","family":"Schoenwether","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lee D.","family":"Kaplan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael G.","family":"Baraga","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7132-4067","authenticated-orcid":true,"given":"Joseph P.","family":"Costello II","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9465-9401","authenticated-orcid":true,"given":"Jordan","family":"Eskenazi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Molly","family":"Dennison","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas M.","family":"Best","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-8244-4116","authenticated-orcid":true,"given":"Joseph F.","family":"Signorile","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3120-6944","authenticated-orcid":true,"given":"Moataz","family":"Eltoukhy","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2024,8,16]]},"reference":[{"issue":"1","key":"pone.0309003.ref001","doi-asserted-by":"crossref","first-page":"e175","DOI":"10.1016\/j.asmr.2021.10.027","article-title":"Anterior Cruciate Ligament Rehabilitation and Return to Sport: How Fast Is Too Fast?","volume":"4","author":"K Waldron","year":"2022","journal-title":"Arthrosc Sports Med Rehabil"},{"issue":"1","key":"pone.0309003.ref002","doi-asserted-by":"crossref","first-page":"e103","DOI":"10.1016\/j.asmr.2021.11.002","article-title":"Contemporary Principles for Postoperative Rehabilitation and Return to Sport for Athletes Undergoing Anterior Cruciate Ligament Reconstruction","volume":"4","author":"CR Badawy","year":"2022","journal-title":"Arthrosc Sports Med Rehabil"},{"issue":"9","key":"pone.0309003.ref003","doi-asserted-by":"crossref","first-page":"512","DOI":"10.1136\/bjsports-2018-100310","article-title":"How should clinicians rehabilitate patients after ACL reconstruction? A systematic review of clinical practice guidelines (CPGs) with a focus on quality appraisal (AGREE II)","volume":"54","author":"R Andrade","year":"2020","journal-title":"Br J Sports Med"},{"issue":"24","key":"pone.0309003.ref004","doi-asserted-by":"crossref","first-page":"1506","DOI":"10.1136\/bjsports-2015-095898","article-title":"Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus","volume":"50","author":"N van Melick","year":"2016","journal-title":"Br J Sports Med"},{"issue":"3","key":"pone.0309003.ref005","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1177\/1941738113517855","article-title":"Anterior Cruciate Ligament Reconstruction Rehabilitation: MOON Guidelines","volume":"7","author":"RW Wright","year":"2015","journal-title":"Sports Health"},{"issue":"11","key":"pone.0309003.ref006","doi-asserted-by":"crossref","first-page":"A1","DOI":"10.2519\/jospt.2017.0303","article-title":"Knee Stability and Movement Coordination Impairments: Knee Ligament Sprain Revision 2017","volume":"47","author":"DS Logerstedt","year":"2017","journal-title":"J Orthop Sports Phys Ther"},{"issue":"4","key":"pone.0309003.ref007","doi-asserted-by":"crossref","first-page":"379","DOI":"10.3109\/17453674.2012.704563","article-title":"Guideline on anterior cruciate ligament injury","volume":"83","author":"DE Meuffels","year":"2012","journal-title":"Acta orthopaedica"},{"issue":"3","key":"pone.0309003.ref008","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1016\/j.arthro.2022.07.024","article-title":"There Is Substantial Variation in Rehabilitation Protocols Following Anterior Cruciate Ligament Reconstruction: A Survey of 46 American Orthopaedic Surgeons","volume":"39","author":"KE Glattke","year":"2023","journal-title":"Arthroscopy"},{"issue":"2","key":"pone.0309003.ref009","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1177\/19417381211009473","article-title":"Test Batteries After Primary Anterior Cruciate Ligament Reconstruction: A Systematic Review","volume":"14","author":"C Roe","year":"2022","journal-title":"Sports Health"},{"issue":"10","key":"pone.0309003.ref010","doi-asserted-by":"crossref","first-page":"801","DOI":"10.2519\/jospt.2018.8264","article-title":"Rehabilitation Practice Patterns Following Anterior Cruciate Ligament Reconstruction: A Survey of Physical Therapists","volume":"48","author":"EM Greenberg","year":"2018","journal-title":"J Orthop Sports Phys Ther"},{"key":"pone.0309003.ref011","first-page":"4","article-title":"Think outside the box: Incorporating secondary cognitive tasks into return to sport testing after ACL reconstruction","author":"CR Chaaban","year":"2023","journal-title":"Front Sports Act Living"},{"issue":"1","key":"pone.0309003.ref012","doi-asserted-by":"crossref","first-page":"e77","DOI":"10.1016\/j.asmr.2021.10.025","article-title":"Rehabilitation and Return to Sport Testing After Anterior Cruciate Ligament Reconstruction: Where Are We in 2022?","volume":"4","author":"A Gokeler","year":"2022","journal-title":"Arthrosc Sports Med Rehabil"},{"issue":"5","key":"pone.0309003.ref013","doi-asserted-by":"crossref","first-page":"334","DOI":"10.2519\/jospt.2017.7285","article-title":"Limb Symmetry Indexes Can Overestimate Knee Function After Anterior Cruciate Ligament Injury","volume":"47","author":"E Wellsandt","year":"2017","journal-title":"J Orthop Sports Phys Ther"},{"issue":"6","key":"pone.0309003.ref014","doi-asserted-by":"crossref","first-page":"947","DOI":"10.1016\/j.otsr.2017.02.015","article-title":"A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: A case control study","volume":"103","author":"A Gokeler","year":"2017","journal-title":"Orthop Traumatol Surg Res"},{"issue":"3","key":"pone.0309003.ref015","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1136\/bjsports-2018-099918","article-title":"Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: a systematic review and meta-analysis","volume":"54","author":"A Kotsifaki","year":"2020","journal-title":"Br J Sports Med"},{"issue":"5","key":"pone.0309003.ref016","doi-asserted-by":"crossref","first-page":"249","DOI":"10.1136\/bjsports-2020-103677","article-title":"Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?","volume":"56","author":"A Kotsifaki","year":"2022","journal-title":"Br J Sports Med"},{"issue":"2","key":"pone.0309003.ref017","doi-asserted-by":"crossref","first-page":"393","DOI":"10.26603\/001c.21140","article-title":"Which Hop Tests Can Best Identify Functional Limb Asymmetry in Patients 9\u201312 Months After Anterior Cruciate Ligament Reconstruction Employing a Hamstrings Tendon Autograft","volume":"16","author":"JR Ebert","year":"2021","journal-title":"Int J Sports Phys Ther"},{"key":"pone.0309003.ref018","article-title":"Reactive Strength Index as a Key Performance Indicator in Different Athlete Populations \u2013 A Systematic Review","author":"B Southey","year":"2023","journal-title":"Science & Sports"},{"issue":"4","key":"pone.0309003.ref019","doi-asserted-by":"crossref","first-page":"548","DOI":"10.1123\/ijspp.2016-0216","article-title":"The relationship between maximal strength and reactive strength","volume":"12","author":"K Beattie","year":"2017","journal-title":"Int J Sports Physiol Perform"},{"issue":"2","key":"pone.0309003.ref020","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1007\/s40279-021-01566-y","article-title":"Reactive Strength Index and its Associations with Measures of Physical and Sports Performance: A Systematic Review with Meta-Analysis","volume":"52","author":"P Jarvis","year":"2022","journal-title":"Sports Med"},{"issue":"1","key":"pone.0309003.ref021","first-page":"65","article-title":"Influence of Sex and Maximum Strength on Reactive Strength Index-Modified","volume":"18","author":"GK Beckham","year":"2019","journal-title":"J Sports Sci Med"},{"issue":"5","key":"pone.0309003.ref022","doi-asserted-by":"crossref","first-page":"1310","DOI":"10.1519\/JSC.0000000000000761","article-title":"A comparison of reactive strength index-modified between six U.S. Collegiate athletic teams","volume":"29","author":"TJ Suchomel","year":"2015","journal-title":"J Strength Cond Res"},{"issue":"5","key":"pone.0309003.ref023","doi-asserted-by":"crossref","first-page":"1201","DOI":"10.1519\/JSC.0000000000003102","article-title":"Reactive Strength Index and Knee Extension Strength Characteristics Are Predictive of Single-Leg Hop Performance After Anterior Cruciate Ligament Reconstruction","volume":"33","author":"T Birchmeier","year":"2019","journal-title":"J Strength Cond Res"},{"issue":"5","key":"pone.0309003.ref024","doi-asserted-by":"crossref","first-page":"1357","DOI":"10.1016\/j.knee.2020.07.003","article-title":"Individual hop analysis and reactive strength ratios provide better discrimination of ACL reconstructed limb deficits than triple hop for distance scores in athletes returning to sport","volume":"27","author":"RS Lloyd","year":"2020","journal-title":"The Knee"},{"issue":"2","key":"pone.0309003.ref025","doi-asserted-by":"crossref","first-page":"60","DOI":"10.2519\/jospt.1994.20.2.60","article-title":"The relationship between subjective knee scores, isokinetic testing, and functional testing in the ACL-reconstructed knee","volume":"20","author":"KE Wilk","year":"1994","journal-title":"J Orthop Sports Phys Ther"},{"issue":"3","key":"pone.0309003.ref026","doi-asserted-by":"crossref","first-page":"141","DOI":"10.2519\/jospt.2010.3168","article-title":"Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction","volume":"40","author":"EH Hartigan","year":"2010","journal-title":"J Orthop Sports Phys Ther"},{"issue":"3","key":"pone.0309003.ref027","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1111\/j.1600-0838.2008.00816.x","article-title":"Performance-based functional evaluation of non-operative and operative treatment after anterior cruciate ligament injury","volume":"19","author":"H Moksnes","year":"2009","journal-title":"Scand J Med Sci Sports"},{"issue":"4","key":"pone.0309003.ref028","doi-asserted-by":"crossref","first-page":"859","DOI":"10.1007\/s00167-012-1929-2","article-title":"Symmetry restoration and functional recovery before and after anterior cruciate ligament reconstruction","volume":"21","author":"D Logerstedt","year":"2013","journal-title":"Knee Surg Sports Traumatol Arthrosc"},{"issue":"5","key":"pone.0309003.ref029","doi-asserted-by":"crossref","first-page":"513","DOI":"10.1177\/036354659101900518","article-title":"Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture","volume":"19","author":"FR Noyes","year":"1991","journal-title":"Am J Sports Med"},{"issue":"10","key":"pone.0309003.ref030","doi-asserted-by":"crossref","DOI":"10.3390\/s18103460","article-title":"Inertial Sensor Angular Velocities Reflect Dynamic Knee Loading during Single Limb Loading in Individuals Following Anterior Cruciate Ligament Reconstruction","volume":"18","author":"KA Pratt","year":"2018","journal-title":"Sensors (Basel)"},{"issue":"4","key":"pone.0309003.ref031","doi-asserted-by":"crossref","first-page":"942","DOI":"10.1177\/03635465231152899","article-title":"The Associations Between Quadriceps Tendon Graft Thickness and Isokinetic Performance","volume":"51","author":"MI Letter","year":"2023","journal-title":"Am J Sports Med"},{"issue":"3","key":"pone.0309003.ref032","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1519\/JSC.0000000000002998","article-title":"Variations in Verbal Encouragement Modify Isokinetic Performance","volume":"33","author":"NK Rendos","year":"2019","journal-title":"J Strength Cond Res"},{"key":"pone.0309003.ref033","doi-asserted-by":"crossref","first-page":"111793","DOI":"10.1016\/j.jbiomech.2023.111793","article-title":"A comparison of three-dimensional kinematics between markerless and marker-based motion capture in overground gait","volume":"159","author":"Z Ripic","year":"2023","journal-title":"J Biomech"},{"issue":"1","key":"pone.0309003.ref034","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1136\/bjsports-2019-101245","article-title":"Better reporting standards are needed to enhance the quality of hop testing in the setting of ACL return to sport decisions: a narrative review","volume":"55","author":"R Paul","year":"2021","journal-title":"Br J Sports Med"},{"issue":"4","key":"pone.0309003.ref035","doi-asserted-by":"crossref","first-page":"595","DOI":"10.1123\/jsr.2020-0154","article-title":"The 6-m Timed Hop Is Not a Suitable Clinical Assessment Tool for Use Following Anterior Cruciate Ligament Reconstruction","volume":"30","author":"PJ Read","year":"2020","journal-title":"J Sport Rehabil"},{"issue":"4","key":"pone.0309003.ref036","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1123\/jab.2017-0145","article-title":"The Effects of Filter Cutoff Frequency on Musculoskeletal Simulations of High-Impact Movements","volume":"34","author":"SS Tomescu","year":"2018","journal-title":"J Appl Biomech"},{"issue":"1","key":"pone.0309003.ref037","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1519\/JSC.0000000000004193","article-title":"Comparison of Vertical and Horizontal Reactive Strength Index Variants and Association With Change of Direction Performance","volume":"37","author":"N \u0160arabon","year":"2023","journal-title":"J Strength Cond Res"},{"issue":"12","key":"pone.0309003.ref038","doi-asserted-by":"crossref","first-page":"3502","DOI":"10.1016\/j.jbiomech.2015.07.036","article-title":"A kinematic method to detect foot contact during running for all foot strike patterns","volume":"48","author":"CE Milner","year":"2015","journal-title":"J Biomech"},{"key":"pone.0309003.ref039","first-page":"8","article-title":"Repeated Measures Correlation","author":"JZ Bakdash","year":"2017","journal-title":"Front Psych"},{"issue":"6977","key":"pone.0309003.ref040","doi-asserted-by":"crossref","first-page":"446","DOI":"10.1136\/bmj.310.6977.446","article-title":"Statistics notes: Calculating correlation coefficients with repeated observations: Part 1\u2014correlation within subjects","volume":"310","author":"JM Bland","year":"1995","journal-title":"Bmj"},{"issue":"6980","key":"pone.0309003.ref041","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1136\/bmj.310.6980.633","article-title":"Calculating correlation coefficients with repeated observations: Part 2\u2014Correlation between subjects","volume":"310","author":"JM Bland","year":"1995","journal-title":"Bmj"},{"issue":"3","key":"pone.0309003.ref042","first-page":"69","article-title":"Statistics corner: A guide to appropriate use of correlation coefficient in medical research","volume":"24","author":"MM Mukaka","year":"2012","journal-title":"Malawi Med J"},{"issue":"4","key":"pone.0309003.ref043","doi-asserted-by":"crossref","first-page":"1149","DOI":"10.3758\/BRM.41.4.1149","article-title":"Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses","volume":"41","author":"F Faul","year":"2009","journal-title":"Behav Res Methods"},{"issue":"2","key":"pone.0309003.ref044","doi-asserted-by":"crossref","first-page":"175","DOI":"10.3758\/BF03193146","article-title":"G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences","volume":"39","author":"F Faul","year":"2007","journal-title":"Behav Res Methods"},{"key":"pone.0309003.ref045","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.ptsp.2021.07.004","article-title":"Knee strength outcomes in adolescents by age and sex during late-stage rehabilitation after anterior cruciate ligament reconstruction","volume":"51","author":"DP Roman","year":"2021","journal-title":"Phys Ther Sport"},{"issue":"2","key":"pone.0309003.ref046","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.jcm.2016.02.012","article-title":"A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research","volume":"15","author":"TK Koo","year":"2016","journal-title":"J Chiropr Med"},{"issue":"2","key":"pone.0309003.ref047","doi-asserted-by":"crossref","first-page":"E35","DOI":"10.1055\/a-0608-4280","article-title":"Landing Styles Influences Reactive Strength Index without Increasing Risk for Injury","volume":"2","author":"D Guy-Cherry","year":"2018","journal-title":"Sports Med Int Open"},{"issue":"1","key":"pone.0309003.ref048","article-title":"Sex Differences in Countermovement Jump Phase Characteristics","volume":"5","author":"JJ McMahon","year":"2017","journal-title":"Sports (Basel)"},{"key":"pone.0309003.ref049","doi-asserted-by":"crossref","first-page":"921","DOI":"10.1007\/s00167-018-5215-9","article-title":"Demographic and surgical factors affect quadriceps strength after ACL reconstruction","volume":"27","author":"C Kuenze","year":"2019","journal-title":"Knee Surg Sports Traumatol Arthrosc"},{"issue":"3","key":"pone.0309003.ref050","doi-asserted-by":"crossref","first-page":"142","DOI":"10.2519\/jospt.2022.10693","article-title":"Quadriceps and Hamstrings Strength Reference Values for Athletes With and Without Anterior Cruciate Ligament Reconstruction Who Play Popular Pivoting Sports, Including Soccer, Basketball, and Handball: A Scoping Review","volume":"52","author":"N van Melick","year":"2022","journal-title":"J Orthop Sports Phys Ther"}],"container-title":["PLOS ONE"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0309003","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,8,16]],"date-time":"2024-08-16T17:37:08Z","timestamp":1723829828000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0309003"}},"subtitle":[],"editor":[{"given":"Luciana","family":"Labanca","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2024,8,16]]},"references-count":50,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2024,8,16]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0309003","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,8,16]]}}}