{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T04:14:42Z","timestamp":1791951282342,"version":"4.3.4"},"reference-count":56,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,2,27]],"date-time":"2025-02-27T00:00:00Z","timestamp":1740614400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["1R15HD109666"],"award-info":[{"award-number":["1R15HD109666"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["P20GM109090"],"award-info":[{"award-number":["P20GM109090"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Neurol."],"abstract":"<jats:sec><jats:title>Objective<\/jats:title><jats:p>The purposes of this study were to (1) investigate muscle co-contraction during aquatic (Wet) and conventional (Dry) treadmill walking at various speeds in typically developing (TD) and children with cerebral palsy (CP) and (2) explore how the clinical interpretation of co-contraction, using co-contraction indices (CCI), may vary depending on the method employed.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Fifteen TD children (30 limbs, 7\u202fM | 8F, 11.3\u202f\u00b1\u202f4.1\u202fyrs., 1.46\u202f\u00b1\u202f0.18\u202fm, 44.2\u202f\u00b1\u202f16.8\u202fkg) and 10 children with CP (20 limbs, 6\u202fM | 4F, 13.1\u202f\u00b1\u202f3.5\u202fyrs., 1.54\u202f\u00b1\u202f0.18\u202fm, 53.2\u202f\u00b1\u202f26.2\u202fkg, 7 GMFCS I and 3 II) participated in this study. Muscle activity of the tibialis anterior (TA), rectus femoris (RF), medial gastrocnemius (MG), and semitendinosus (ST) was recorded during three 3-min walking trials on a Dry treadmill followed by a Wet treadmill. Muscle co-contraction was calculated using three common CCI calculation methods for the RF\/ST and TA\/MG muscle pairings. Separate linear mixed-effects models examined the influence of population (TD vs. CP), walking speed (Slow, Normal, Fast), and treadmill environment (Dry vs. Wet) on CCI for each equation and muscle pairing.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>CCI<jats:sub>Unnithan<\/jats:sub> and CCI<jats:sub>Rudolph<\/jats:sub> demonstrated that aquatic treadmill walking reduced muscle co-contraction in TD (<jats:italic>p<\/jats:italic>\u202f&amp;lt;\u202f0.001) and CP (<jats:italic>p<\/jats:italic>\u202f&amp;lt;\u202f0.012) populations for the RF\/ST muscle pairing. Additionally, CCI<jats:sub>Unnithan<\/jats:sub> and CCI<jats:sub>Rudolph<\/jats:sub> showed significant differences between speeds in both environments (<jats:italic>p<\/jats:italic>\u202f&amp;lt;\u202f0.001) except for the Slow-Normal comparison in the aquatic treadmill (<jats:italic>p<\/jats:italic>\u202f&amp;gt;\u202f0.423). All methods had a significant CCI reduction in the TA\/MG muscle pairing for both populations. For the RF\/ST muscle pairing, CCI<jats:sub>F&amp;amp;W<\/jats:sub> showed that only TD children had lower muscle co-contraction in the aquatic treadmill (<jats:italic>p<\/jats:italic>\u202f=\u202f0.023). CCI<jats:sub>F&amp;amp;W<\/jats:sub> also showed no speed effect for the muscle pairings.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>This study shows the potential of aquatic treadmill walking to reduce muscle co-contraction; however, caution is recommended as clinical implications can vary due to the computation method. Future studies should aim to report values from multiple methods to account for the variability within methods and validation of results.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fneur.2025.1506326","type":"journal-article","created":{"date-parts":[[2025,2,27]],"date-time":"2025-02-27T05:18:29Z","timestamp":1740633509000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":6,"title":["Differences in lower limb co-contraction calculations vary clinical interpretation of aquatic treadmill walking in typically developing and children with cerebral palsy"],"prefix":"10.3389","volume":"16","author":[{"given":"Joseph W.","family":"Harrington","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brian A.","family":"Knarr","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vivek","family":"Dutt","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David C.","family":"Kingston","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,2,27]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"45","DOI":"10.1016\/j.pcl.2019.09.002","article-title":"Pediatric Neuromuscular Disorders","volume":"67","author":"Michel","year":"2020","journal-title":"Pediatr Clin N Am"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"462","DOI":"10.1016\/j.ridd.2010.12.042","article-title":"Prevalence and functioning of children with cerebral palsy in four areas of the United States in 2006: a report from the autism and developmental disabilities monitoring network","volume":"32","author":"Kirby","year":"2011","journal-title":"Res Dev Disabil"},{"key":"ref3","doi-asserted-by":"publisher","first-page":"214","DOI":"10.1111\/j.1469-8749.1997.tb07414.x","article-title":"Development and reliability of a system to classify gross motor function in children with cerebral palsy","volume":"39","author":"Palisano","year":"1997","journal-title":"Develop Med Child Neuro"},{"key":"ref4","doi-asserted-by":"publisher","first-page":"135","DOI":"10.3109\/09638288.2015.1095950","article-title":"Isometric muscle strength and mobility capacity in children with cerebral palsy","volume":"39","author":"Dallmeijer","year":"2017","journal-title":"Disabil Rehabil"},{"key":"ref5","doi-asserted-by":"publisher","first-page":"834","DOI":"10.1177\/1545968318796333","article-title":"Children with cerebral palsy have greater stride-to-stride variability of muscle synergies during gait than typically developing children: implications for motor control complexity","volume":"32","author":"Kim","year":"2018","journal-title":"Neurorehabil Neural Repair"},{"key":"ref6","doi-asserted-by":"crossref","DOI":"10.1002\/9780470549148","volume-title":"Biomechanics and motor control of human movement","author":"Winter","year":"2009"},{"key":"ref7","doi-asserted-by":"publisher","first-page":"859","DOI":"10.1016\/j.pmrj.2009.05.017","article-title":"Aquatic therapy: scientific foundations and clinical rehabilitation applications","volume":"1","author":"Becker","year":"2009","journal-title":"PM & R"},{"key":"ref8","doi-asserted-by":"publisher","first-page":"256","DOI":"10.1016\/S0268-0033(99)00070-4","article-title":"Determination of hydrodynamic drag forces and drag coefficients on human leg\/foot model during knee exercise","volume":"15","author":"P\u00f6yh\u00f6nen","year":"2000","journal-title":"Clin Biomech"},{"key":"ref9","doi-asserted-by":"publisher","first-page":"68","DOI":"10.1097\/PEP.0b013e318196eb37","article-title":"An aquatic physical therapy program at a pediatric rehabilitation hospital: a case series","volume":"21","author":"Fragala-Pinkham","year":"2009","journal-title":"Pediatr Phys Ther"},{"key":"ref10","first-page":"1","article-title":"Comparing the effects of aquatic and land-based exercises on balance and walking in spastic Diplegic cerebral palsy children","volume":"84","author":"Badawy","year":"2016","journal-title":"Med J Cairo Univ"},{"key":"ref11","doi-asserted-by":"publisher","first-page":"1854","DOI":"10.3390\/ijerph20031854","article-title":"Muscle activity and co-activation of gait cycle during walking in water and on land in people with spastic cerebral palsy","volume":"20","author":"Phothirook","year":"2023","journal-title":"IJERPH"},{"key":"ref12","doi-asserted-by":"publisher","first-page":"102737","DOI":"10.1016\/j.jelekin.2022.102737","article-title":"Muscle activation and rating of perceived exertion of typically developing children during DRY and aquatic treadmill walking","volume":"68","author":"Harrington","year":"2023","journal-title":"J Electromyogr Kinesiol"},{"key":"ref13","doi-asserted-by":"publisher","first-page":"6","DOI":"10.1016\/j.gaitpost.2023.07.002","article-title":"Muscle co-contraction and co-activation in cerebral palsy during gait: a scoping review","volume":"105","author":"Mohammadyari Gharehbolagh","year":"2023","journal-title":"Gait Posture"},{"key":"ref14","doi-asserted-by":"publisher","first-page":"1","DOI":"10.3389\/fbioe.2020.588908","article-title":"How well do commonly used co-contraction indices approximate lower limb joint stiffness trends during gait for individuals post-stroke?","volume":"8","author":"Li","year":"2021","journal-title":"Front Bioeng Biotechnol"},{"key":"ref15","first-page":"23","article-title":"Analysis of an EMG method for quantification of muscular co-contraction","volume":"9","author":"Fonseca","year":"2001","journal-title":"Rev Bras Ci Mov"},{"key":"ref16","first-page":"135","article-title":"Quantitative assessment of co-contraction at the ankle joint in walking","volume":"25","author":"Falconer","year":"1985","journal-title":"Electromyogr Clin Neurophysiol"},{"key":"ref17","doi-asserted-by":"publisher","first-page":"497","DOI":"10.1016\/S0966-6362(98)90226-0","article-title":"Quantification of cocontraction in spastic cerebral palsy","volume":"38","author":"Ikeda","year":"1998","journal-title":"Electromyogr Clin Neurophysiol"},{"key":"ref18","doi-asserted-by":"publisher","first-page":"186","DOI":"10.1159\/000421492","article-title":"Pathophysiological profile of gait in children with cerebral palsy","volume":"36","author":"Crenna","year":"1992","journal-title":"Med Sport Sci"},{"key":"ref19","doi-asserted-by":"publisher","first-page":"407","DOI":"10.1016\/S1050-6411(00)00028-6","article-title":"Coactivation during gait as an adaptive behavior after stroke","volume":"10","author":"Lamontagne","year":"2000","journal-title":"J Electromyogr Kinesiol"},{"key":"ref20","first-page":"487","article-title":"Cocontraction and phasic activity during GAIT in children with cerebral palsy","volume":"36","author":"Unnithan","year":"1996","journal-title":"Electromyogr Clin Neurophysiol"},{"key":"ref21","doi-asserted-by":"publisher","first-page":"262","DOI":"10.1007\/s001670000130","article-title":"Dynamic stability after ACL injury: who can hop?","volume":"8","author":"Rudolph","year":"2000","journal-title":"Knee Surg Sports Traumatol Arthrosc"},{"key":"ref22","doi-asserted-by":"publisher","first-page":"312","DOI":"10.1016\/j.clinbiomech.2013.01.002","article-title":"The influence of gait speed on co-activation in unilateral spastic cerebral palsy children","volume":"28","author":"Gross","year":"2013","journal-title":"Clin Biomech"},{"key":"ref23","article-title":"European recommendations for surface electro Myo Graphy","author":"Hermens","year":"1999","journal-title":"Roessingh Res Develop"},{"key":"ref24","doi-asserted-by":"publisher","first-page":"361","DOI":"10.1016\/S1050-6411(00)00027-4","article-title":"Development of recommendations for SEMG sensors and sensor placement procedures","volume":"10","author":"Hermens","year":"2000","journal-title":"J Electromyogr Kinesiol"},{"key":"ref25","doi-asserted-by":"publisher","first-page":"270","DOI":"10.1016\/S0966-6362(03)00071-7","article-title":"Speed related changes in muscle activity from normal to very slow walking speeds","volume":"19","author":"Den Otter","year":"2004","journal-title":"Gait Posture"},{"key":"ref26","doi-asserted-by":"publisher","first-page":"974","DOI":"10.1016\/j.joca.2012.05.014","article-title":"Knee effusion affects knee mechanics and muscle activity during gait in individuals with knee osteoarthritis","volume":"20","author":"Rutherford","year":"2012","journal-title":"Osteoarthr Cartil"},{"key":"ref27","doi-asserted-by":"publisher","first-page":"334","DOI":"10.1016\/j.jelekin.2012.12.002","article-title":"Reliability of surface electromyographic recordings during walking in individuals with knee osteoarthritis","volume":"23","author":"Hubley-Kozey","year":"2013","journal-title":"J Electromyogr Kinesiol"},{"key":"ref28","doi-asserted-by":"publisher","first-page":"607","DOI":"10.1016\/j.jelekin.2012.02.001","article-title":"Comparison of electromyography and joint moment as indicators of co-contraction","volume":"22","author":"Knarr","year":"2012","journal-title":"J Electromyogr Kinesiol"},{"key":"ref29","doi-asserted-by":"publisher","first-page":"699","DOI":"10.3389\/fneur.2017.00699","article-title":"Electromyography exposes heterogeneity in muscle co-contraction following stroke","volume":"8","author":"Banks","year":"2017","journal-title":"Front Neurol"},{"key":"ref30","doi-asserted-by":"publisher","first-page":"110","DOI":"10.1016\/j.gaitpost.2017.01.010","article-title":"Functional implications of muscle co-contraction during gait in advanced age","volume":"53","author":"Lo","year":"2017","journal-title":"Gait Posture"},{"key":"ref31","author":"Pinheiro","year":"2024"},{"key":"ref32","doi-asserted-by":"publisher","first-page":"346","DOI":"10.1002\/bimj.200810425","article-title":"Simultaneous inference in general parametric models","volume":"50","author":"Hothorn","year":"2008","journal-title":"Biom J"},{"key":"ref33","doi-asserted-by":"publisher","first-page":"104092","DOI":"10.1016\/j.jml.2020.104092","article-title":"Best practice guidance for linear mixed-effects models in psychological science","volume":"112","author":"Meteyard","year":"2020","journal-title":"J Mem Lang"},{"key":"ref34","doi-asserted-by":"publisher","first-page":"135","DOI":"10.1214\/12-STS410","article-title":"Model selection in linear mixed models","volume":"28","author":"M\u00fcller","year":"2013","journal-title":"Stat Sci"},{"key":"ref35","doi-asserted-by":"publisher","first-page":"1175","DOI":"10.2193\/2009-367","article-title":"Uninformative parameters and model selection using Akaike\u2019s information criterion","volume":"74","author":"Arnold","year":"2010","journal-title":"J Wildl Manag"},{"key":"ref36","doi-asserted-by":"publisher","first-page":"631","DOI":"10.1890\/13-1452.1","article-title":"Model selection for ecologists: the worldviews of AIC and BIC","volume":"95","author":"Aho","year":"2014","journal-title":"Ecology"},{"key":"ref37","doi-asserted-by":"publisher","first-page":"101","DOI":"10.1111\/j.1469-8749.2007.00101.x","article-title":"Partial body-weight-supported treadmill training can improve walking in children with cerebral palsy: a clinical controlled trial","volume":"49","author":"Dodd","year":"2007","journal-title":"Dev Med Child Neurol"},{"key":"ref38","doi-asserted-by":"publisher","first-page":"87","DOI":"10.3109\/17518423.2011.552459","article-title":"Body weight supported treadmill training improves the regularity of the stepping kinematics in children with cerebral palsy","volume":"14","author":"Kurz","year":"2011","journal-title":"Dev Neurorehabil"},{"key":"ref39","doi-asserted-by":"publisher","first-page":"69","DOI":"10.3109\/09593985.2013.825825","article-title":"Aquatic aerobic exercise for children with cerebral palsy: a pilot intervention study","volume":"30","author":"Fragala-Pinkham","year":"2014","journal-title":"Physiother Theory Pract"},{"key":"ref40","doi-asserted-by":"publisher","first-page":"297","DOI":"10.1080\/14763141.2017.1409255","article-title":"The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking","volume":"18","author":"Jung","year":"2019","journal-title":"Sports Biomech"},{"key":"ref41","doi-asserted-by":"publisher","first-page":"39","DOI":"10.2478\/hukin-2022-0030","article-title":"A study comparing gait and lower limb muscle activity during aquatic treadmill running with different water depth and land treadmill running","volume":"82","author":"So","year":"2022","journal-title":"J Hum Kinet"},{"key":"ref42","doi-asserted-by":"publisher","first-page":"327","DOI":"10.1016\/j.gaitpost.2008.01.014","article-title":"Influence of light handrail use on the biomechanics of stair negotiation in old age","volume":"28","author":"Reeves","year":"2008","journal-title":"Gait Posture"},{"key":"ref43","doi-asserted-by":"publisher","first-page":"70","DOI":"10.1186\/s12984-015-0051-3","article-title":"Effects of handrail hold and light touch on energetics, step parameters, and neuromuscular activity during walking after stroke","volume":"12","author":"IJmker","year":"2015","journal-title":"J Neuro Eng Rehabil"},{"key":"ref44","doi-asserted-by":"publisher","first-page":"107","DOI":"10.1123\/JSR.2013-0003","article-title":"Lower-extremity muscle activity during aquatic and land treadmill running at the same speeds","volume":"23","author":"Silvers","year":"2014","journal-title":"J Sport Rehabil"},{"key":"ref45","doi-asserted-by":"publisher","first-page":"579","DOI":"10.2114\/jpa2.26.579","article-title":"Gait patterns and muscle activity in the lower extremities of elderly women during underwater treadmill walking against water flow","volume":"26","author":"Shono","year":"2007","journal-title":"J Physiol Anthropol"},{"key":"ref46","doi-asserted-by":"publisher","first-page":"119","DOI":"10.2114\/jpa.23.119","article-title":"Electromyographic analysis of walking in water in healthy humans","volume":"23","author":"Masumoto","year":"2004","journal-title":"J Physiol Anthropol"},{"key":"ref47","doi-asserted-by":"publisher","first-page":"581","DOI":"10.1016\/j.jelekin.2006.12.009","article-title":"Muscle activation, cardiorespiratory response, and rating of perceived exertion in older subjects while walking in water and on dry land","volume":"18","author":"Masumoto","year":"2008","journal-title":"J Electromyogr Kinesiol"},{"key":"ref48","doi-asserted-by":"publisher","first-page":"480","DOI":"10.1123\/mcj.16.4.480","article-title":"Effect of gait speed on muscle activity patterns and magnitude during stance","volume":"16","author":"Sousa","year":"2012","journal-title":"Mot Control"},{"key":"ref49","doi-asserted-by":"publisher","first-page":"272","DOI":"10.1002\/jor.1100020309","article-title":"Kinematic and EMG patterns during slow, free, and fast walking","volume":"2","author":"Murray","year":"1984","journal-title":"J Orthop Res"},{"key":"ref50","doi-asserted-by":"publisher","first-page":"1639","DOI":"10.1016\/j.jbiomech.2008.03.015","article-title":"The effect of walking speed on the gait of typically developing children","volume":"41","author":"Schwartz","year":"2008","journal-title":"J Biomech"},{"key":"ref51","doi-asserted-by":"publisher","first-page":"724","DOI":"10.1080\/09638280410001704313","article-title":"Effect of the walking speed to the lower limb joint angular displacements, joint moments and ground reaction forces during walking in water","volume":"26","author":"Miyoshi","year":"2004","journal-title":"Disabil Rehabil"},{"key":"ref52","doi-asserted-by":"publisher","first-page":"e0138105","DOI":"10.1371\/journal.pone.0138105","article-title":"Gait kinematic analysis in water using wearable inertial magnetic sensors","volume":"10","author":"Fantozzi","year":"2015","journal-title":"PLoS One"},{"key":"ref53","doi-asserted-by":"publisher","first-page":"6","DOI":"10.1016\/j.gaitpost.2020.08.112","article-title":"Effect of walking speed during gait in water of healthy elderly","volume":"82","author":"Fantozzi","year":"2020","journal-title":"Gait Posture"},{"key":"ref54","doi-asserted-by":"publisher","first-page":"141","DOI":"10.1016\/j.jbiomech.2017.03.029","article-title":"Comparison of methodologies to assess muscle co-contraction during gait","volume":"57","author":"Souissi","year":"2017","journal-title":"J Biomech"},{"key":"ref55","doi-asserted-by":"publisher","first-page":"202","DOI":"10.3389\/fneur.2020.00202","article-title":"Surface electromyography normalization affects the interpretation of muscle activity and Coactivation in children with cerebral palsy during walking","volume":"11","author":"Gagnat","year":"2020","journal-title":"Front Neurol"},{"key":"ref56","doi-asserted-by":"publisher","first-page":"179","DOI":"10.1016\/j.jelekin.2013.11.003","article-title":"Methodologies to assess muscle co-contraction during gait in people with neurological impairment \u2013 a systematic literature review","volume":"24","author":"Rosa","year":"2014","journal-title":"J Electromyogr Kinesiol"}],"container-title":["Frontiers in Neurology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fneur.2025.1506326\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,3,3]],"date-time":"2025-03-03T16:00:57Z","timestamp":1741017657000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fneur.2025.1506326\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,2,27]]},"references-count":56,"alternative-id":["10.3389\/fneur.2025.1506326"],"URL":"https:\/\/doi.org\/10.3389\/fneur.2025.1506326","relation":{},"ISSN":["1664-2295"],"issn-type":[{"value":"1664-2295","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,2,27]]},"article-number":"1506326"}}