{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T19:36:58Z","timestamp":1780688218043,"version":"3.54.1"},"reference-count":107,"publisher":"The Company of Biologists","issue":"11","license":[{"start":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T00:00:00Z","timestamp":1780272000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/www.biologists.com\/user-licence-1-2\/"}],"funder":[{"name":"National Science Foundation","award":["BCS 0935321 and SMA 1719432"],"award-info":[{"award-number":["BCS 0935321 and SMA 1719432"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,6,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>Knuckle-walking is a terrestrial hand posture used by chimpanzees, bonobos and gorillas alone among primates. Given the relevance of these African apes to human origins, considerable research has sought to understand how forces across the hand and wrist have shaped the morphology underlying this unique hand posture. Yet, data on extrinsic hand and wrist muscle activity during knuckle-walking are incomplete; only three extrinsic hand muscles are documented and no new data have been published in the past 45\u2005years. This incompleteness has led to confusing, and sometimes contradictory assumptions being used in comparative functional analyses. Here, we used electromyography (EMG) to investigate eight extrinsic hand muscles (five wrist muscles and three digital muscles) during knuckle-walking in chimpanzees across four commonly used hand postures. We documented a complex pattern of support and swing phase activity in all wrist flexor and extensor musculature, combined with a near silence of digital flexor muscle activity. As in other mammals, wrist flexor activity typically exceeded extensor activity. Hand posture had some effect on muscle activity, notably a general increase in wrist muscle activity when the hand was orientated posteriorly as opposed to medially. Chimpanzee muscle activity showed general similarities with baboons, although chimpanzees showed slightly more activity in radial side muscles whereas baboons showed more reliance on ulnar muscles. These data help rule out two evolutionary hypotheses concerning the origins of knuckle-walking and whether the earliest known hominin knuckle-walked. More importantly, they form a foundation upon which future modeling and form\u2013function studies can draw.<\/jats:p>","DOI":"10.1242\/jeb.251135","type":"journal-article","created":{"date-parts":[[2026,5,22]],"date-time":"2026-05-22T10:33:25Z","timestamp":1779446005000},"source":"Crossref","is-referenced-by-count":1,"title":["The biomechanics of knuckle-walking II: muscle activity of chimpanzee extrinsic hand and wrist muscles"],"prefix":"10.1242","volume":"229","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9273-3636","authenticated-orcid":false,"given":"Nathan E.","family":"Thompson","sequence":"first","affiliation":[{"name":"NYIT College of Osteopathic Medicine 1 Department of Anatomy , , Old Westbury, NY 11568 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4057-2954","authenticated-orcid":false,"given":"Susan G.","family":"Larson","sequence":"additional","affiliation":[{"name":"Renaissance School of Medicine, Stony Brook University 2 Department of Anatomical Sciences , , Stony Brook, NY 11794 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"suffix":"Jr","given":"Jack T.","family":"Stern","sequence":"additional","affiliation":[{"name":"Renaissance School of Medicine, Stony Brook University 2 Department of Anatomical Sciences , , Stony Brook, NY 11794 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1844-1931","authenticated-orcid":false,"given":"Biren A.","family":"Patel","sequence":"additional","affiliation":[{"name":"Keck School of Medicine, University of Southern California 3 Division of Integrative Anatomical Sciences, Department of Medical Education , , Los Angeles, CA 90033 ,","place":["USA"]},{"name":"University of Southern California 4 Human and Evolutionary Biology Section, Department of Biological Sciences , , Los Angeles, CA 90089 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"237","published-online":{"date-parts":[[2026,6,5]]},"reference":[{"key":"2026060504040508600_JEB251135C1","doi-asserted-by":"publisher","first-page":"503","DOI":"10.1002\/(SICI)1096-8644(200004)111:4&lt;503::AID-AJPA6&gt;3.0.CO;2-J","article-title":"Spatio-temporal gait characteristics of the hind-limb cycles during voluntary bipedal and quadrupedal walking in bonobos (Pan paniscus)","volume":"111","author":"Aerts","year":"2000","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C2","doi-asserted-by":"publisher","first-page":"1199","DOI":"10.1152\/physrev.1989.69.4.1199","article-title":"Optimization and gaits in the locomotion of vertebrates","volume":"69","author":"Alexander","year":"1989","journal-title":"Physiol. Rev."},{"key":"2026060504040508600_JEB251135C3","doi-asserted-by":"publisher","first-page":"7717","DOI":"10.1038\/ncomms8717","article-title":"The evolution of human and ape hand proportions","volume":"6","author":"Alm\u00e9cija","year":"2015","journal-title":"Nat. Commun."},{"key":"2026060504040508600_JEB251135C4","doi-asserted-by":"publisher","first-page":"eabb4363","DOI":"10.1126\/science.abb4363","article-title":"Fossil apes and human evolution","volume":"372","author":"Alm\u00e9cija","year":"2021","journal-title":"Science"},{"key":"2026060504040508600_JEB251135C5","doi-asserted-by":"publisher","first-page":"1","DOI":"10.18637\/jss.v067.i01","article-title":"Fitting linear mixed-effects models using lme4","volume":"67","author":"Bates","year":"2015","journal-title":"J. Stat. Softw."},{"key":"2026060504040508600_JEB251135C6","doi-asserted-by":"publisher","first-page":"107","DOI":"10.1111\/j.1365-2907.1973.tb00178.x","article-title":"The description of mammals II. Limbs and locomotion of terrestial mammals","volume":"3","author":"Brown","year":"1973","journal-title":"Mammal. Rev."},{"key":"2026060504040508600_JEB251135C7","doi-asserted-by":"publisher","first-page":"145","DOI":"10.1038\/nature00879","article-title":"A new hominid from the Upper Miocene of Chad, Central Africa","volume":"418","author":"Brunet","year":"2002","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C8","doi-asserted-by":"publisher","first-page":"1618","DOI":"10.1016\/j.jbiomech.2010.02.008","article-title":"Contributions of individual muscles to hip joint contact force in normal walking","volume":"43","author":"Correa","year":"2010","journal-title":"J. Biomech."},{"key":"2026060504040508600_JEB251135C9","doi-asserted-by":"publisher","first-page":"3127","DOI":"10.1152\/jn.01073.2004","article-title":"Kinematic and EMG determinants in quadrupedal locomotion of a non-human primate (rhesus)","volume":"93","author":"Courtine","year":"2005","journal-title":"J. Neurophysiol."},{"key":"2026060504040508600_JEB251135C10","doi-asserted-by":"publisher","first-page":"94","DOI":"10.1038\/s41586-022-04901-z","article-title":"Postcranial evidence of late Miocene hominin bipedalism in Chad","volume":"609","author":"Daver","year":"2022","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C11","volume-title":"Photographic and Descriptive Musculoskeletal Atlas of Chimpanzees: With Notes on the Attachments, Variations, Innervation, Function and Synonymy and Weight of the Muscles","author":"Diogo","year":"2019"},{"key":"2026060504040508600_JEB251135C12","doi-asserted-by":"publisher","first-page":"103513","DOI":"10.1016\/j.jhevol.2024.103513","article-title":"A comparative study of muscle activity and synergies during walking in baboons and humans","volume":"189","author":"Druelle","year":"2024","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C13","doi-asserted-by":"publisher","first-page":"105","DOI":"10.1242\/jeb.76.1.105","article-title":"An electromyographic analysis of forelimb muscles during overground stepping in the cat","volume":"76","author":"English","year":"1978","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C14","doi-asserted-by":"crossref","DOI":"10.56021\/9781421414898","volume-title":"Primate Comparative Anatomy","author":"Gebo","year":"2014"},{"key":"2026060504040508600_JEB251135C15","doi-asserted-by":"publisher","first-page":"245","DOI":"10.1002\/ar.25674","article-title":"Whole-bone shape of hominoid manual proximal phalanges","volume":"309","author":"Goldstein","year":"2026","journal-title":"Anat. Rec."},{"key":"2026060504040508600_JEB251135C16","doi-asserted-by":"publisher","first-page":"31134","DOI":"10.1038\/s41598-024-82479-4","article-title":"Muscle synergy in several locomotor modes in chimpanzees and Japanese macaques, and its implications for the evolutionary origin of bipedalism through shared muscle synergies","volume":"14","author":"Goto","year":"2024","journal-title":"Sci. Rep."},{"key":"2026060504040508600_JEB251135C17","doi-asserted-by":"publisher","first-page":"267","DOI":"10.1111\/j.1749-6632.1912.tb55164.x","article-title":"Notes on the principles of quadrupedal locomotion and on the mechanism of he limbs in hoofed animals","volume":"22","author":"Gregory","year":"1912","journal-title":"Ann. N. Y. Acad. Sci."},{"key":"2026060504040508600_JEB251135C18","doi-asserted-by":"publisher","first-page":"20160235","DOI":"10.1098\/rspb.2016.0235","article-title":"Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees","volume":"283","author":"Hatala","year":"2016","journal-title":"Proc. R. Soc."},{"key":"2026060504040508600_JEB251135C19","doi-asserted-by":"publisher","first-page":"398","DOI":"10.1152\/jn.00803.2018","article-title":"Locomotor kinematics and EMG activity during quadrupedal versus bipedal gait in the Japanese macaque","volume":"122","author":"Higurashi","year":"2019","journal-title":"J. Neurophysiol."},{"key":"2026060504040508600_JEB251135C20","first-page":"65","article-title":"A simple sequentially rejective multiple test procedure","volume":"6","author":"Holm","year":"1979","journal-title":"Scand. J. Stat."},{"key":"2026060504040508600_JEB251135C21","doi-asserted-by":"publisher","first-page":"233","DOI":"10.1016\/0003-9969(93)90033-I","article-title":"Modelling relative masseter force from surface electromyograms during mastication in non-human primates","volume":"38","author":"Hylander","year":"1993","journal-title":"Arch. Oral Biol."},{"key":"2026060504040508600_JEB251135C22","doi-asserted-by":"publisher","first-page":"103600","DOI":"10.1016\/j.jhevol.2024.103600","article-title":"A cadaveric study of wrist-joint moments in chimpanzees and orangutans with implications for the evolution of knuckle-walking","volume":"197","author":"Ito","year":"2024","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C23","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1515\/9783110803808.213","article-title":"Knuckle-walking and the functional anatomy of the wrists in living apes","volume-title":"Primate Functional Morphology and Evolution","author":"Jenkins","year":"1975"},{"key":"2026060504040508600_JEB251135C24","doi-asserted-by":"publisher","first-page":"2037","DOI":"10.1249\/MSS.0b013e3181a8c6e5","article-title":"Is bone's response to mechanical signals dominated by gravitational loading","volume":"41","author":"Judex","year":"2009","journal-title":"Med. Sci. Sports Exerc."},{"key":"2026060504040508600_JEB251135C25","doi-asserted-by":"publisher","first-page":"2","DOI":"10.1002\/ajpa.21183","article-title":"\u201cLucy\u201d redux: a review of research on Australopithecus afarensis","volume":"140","author":"Kimbel","year":"2009","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C26","doi-asserted-by":"publisher","first-page":"197","DOI":"10.1111\/joa.14277","article-title":"The locomotor ecology of wild western lowland gorillas: how does the largest ape exploit complex arboreal environments?","volume":"248","author":"King","year":"2026","journal-title":"J. Anat."},{"key":"2026060504040508600_JEB251135C27","doi-asserted-by":"publisher","first-page":"1411","DOI":"10.1126\/science.1202625","article-title":"Australopithecus sediba hand demonstrates mosaic evolution of locomotor and manipulative abilities","volume":"333","author":"Kivell","year":"2011","journal-title":"Science"},{"key":"2026060504040508600_JEB251135C28","doi-asserted-by":"publisher","first-page":"2050","DOI":"10.1249\/MSS.0b013e3181a8c717","article-title":"Muscle forces or gravity: what predominates mechanical loading on bone?","volume":"41","author":"Kohrt","year":"2009","journal-title":"Med. Sci. Sports Exerc."},{"key":"2026060504040508600_JEB251135C29","doi-asserted-by":"publisher","first-page":"1108","DOI":"10.1098\/rspb.2011.1435","article-title":"Muscle power attenuation by tendon during energy dissipation","volume":"279","author":"Konow","year":"2012","journal-title":"Proc. R. Soc. B Biol. Sci."},{"key":"2026060504040508600_JEB251135C30","doi-asserted-by":"publisher","first-page":"15716","DOI":"10.1073\/pnas.1211740109","article-title":"Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution","volume":"109","author":"Langergraber","year":"2012","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"2026060504040508600_JEB251135C31","doi-asserted-by":"publisher","first-page":"103751","DOI":"10.1016\/j.jhevol.2025.103751","article-title":"Chimpanzee hind limb muscle electromyographic activity patterns during locomotion","volume":"208","author":"Larson","year":"2025","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C32","doi-asserted-by":"publisher","first-page":"629","DOI":"10.1111\/j.1469-7998.1987.tb05961.x","article-title":"EMG of chimpanzee shoulder muscles during knuckle-walking: problems of terrestrial locomotion in a suspensory adapted primate","volume":"212","author":"Larson","year":"1987","journal-title":"J. Zool."},{"key":"2026060504040508600_JEB251135C33","doi-asserted-by":"publisher","first-page":"369","DOI":"10.1002\/ajpa.1330790313","article-title":"Role of supraspinatus in the quadrupedal locomotion of vervets (Cercopithecus aethiops): implications for interpretation of humeral morphology","volume":"79","author":"Larson","year":"1989","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C34","doi-asserted-by":"publisher","first-page":"1204","DOI":"10.1242\/jeb.002337","article-title":"Humeral retractor EMG during quadrupedal walking in primates","volume":"210","author":"Larson","year":"2007","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C35","doi-asserted-by":"publisher","first-page":"71","DOI":"10.1002\/ajpa.1330850109","article-title":"EMG of serratus anterior and trapezius in the chimpanzee: scapular rotators revisited","volume":"85","author":"Larson","year":"1991","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C36","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1007\/978-94-017-7429-1_7","article-title":"The thoracic cage of KSD-VP-1\/1","volume-title":"The Postcranial Anatomy of Australopithecus Afarensis","author":"Latimer","year":"2016"},{"key":"2026060504040508600_JEB251135C37","doi-asserted-by":"publisher","first-page":"jeb236604","DOI":"10.1242\/jeb.236604","article-title":"Kinematic and dynamic aspects of chimpanzee knuckle walking: finger flexors likely do not buffer ground impact forces","volume":"224","author":"Leijnse","year":"2021","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C39","doi-asserted-by":"publisher","first-page":"S70","DOI":"10.1097\/01.PHM.0000029771.92757.2F","article-title":"Mechanisms of muscle injury gleaned from animal models","volume":"81","author":"Lieber","year":"2002","journal-title":"Am. J. Phys. Med. Rehabil."},{"key":"2026060504040508600_JEB251135C41","doi-asserted-by":"publisher","first-page":"3139","DOI":"10.21105\/joss.03139","article-title":"performance: an R package for assessment, comparison and testing of statistical models","volume":"6","author":"L\u00fcdecke","year":"2021","journal-title":"J. Open Source Softw."},{"key":"2026060504040508600_JEB251135C42","doi-asserted-by":"publisher","first-page":"54","DOI":"10.1002\/evan.20046","article-title":"Hunter-gatherers and human evolution","volume":"14","author":"Marlowe","year":"2005","journal-title":"Evol. Anthropol."},{"key":"2026060504040508600_JEB251135C43","doi-asserted-by":"publisher","first-page":"44","DOI":"10.1002\/ajpa.22325","article-title":"Manual pressure distribution patterns of knuckle-walking apes","volume":"152","author":"Matarazzo","year":"2013","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C44","doi-asserted-by":"publisher","first-page":"20221189","DOI":"10.1098\/rspb.2022.1189","article-title":"Humans trade off whole-body energy cost to avoid overburdening muscles while walking","volume":"289","author":"McDonald","year":"2022","journal-title":"Proc. R. Soc. B Biol. Sci."},{"key":"2026060504040508600_JEB251135C45","doi-asserted-by":"publisher","first-page":"468","DOI":"10.1038\/s41586-021-04187-7","article-title":"Footprint evidence of early hominin locomotor diversity at Laetoli, Tanzania","volume":"600","author":"McNutt","year":"2021","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C46","doi-asserted-by":"publisher","first-page":"103355","DOI":"10.1016\/j.jhevol.2023.103355","article-title":"Knuckle-walking in Sahelanthropus? Locomotor inferences from the ulnae of fossil hominins and other hominoids","volume":"179","author":"Meyer","year":"2023","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C47","doi-asserted-by":"publisher","first-page":"897","DOI":"10.1007\/s10914-021-09566-5","article-title":"Ulna curvature in arboreal and terrestrial primates","volume":"28","author":"Milne","year":"2021","journal-title":"J. Mamm. Evol."},{"key":"2026060504040508600_JEB251135C48","doi-asserted-by":"publisher","first-page":"103311","DOI":"10.1016\/j.jhevol.2022.103311","article-title":"An updated analysis of hominin phylogeny with an emphasis on re-evaluating the phylogenetic relationships of Australopithecus sediba","volume":"175","author":"Mongle","year":"2023","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C49","doi-asserted-by":"publisher","first-page":"944","DOI":"10.1038\/s41586-025-09594-8","article-title":"New fossils reveal the hand of Paranthropus boisei","volume":"647","author":"Mongle","year":"2025","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C50","unstructured":"Nengo, I.\n           (1993). Integrating mechanical and historical approaches to organismal design: the case of the shaft structure in the hands and feet of Catarrhines. PhD Dissertation, Harvard University, Cambridge, MA."},{"key":"2026060504040508600_JEB251135C51","doi-asserted-by":"publisher","first-page":"32","DOI":"10.1016\/j.jhevol.2015.05.012","article-title":"Three-dimensional kinematics of the pelvis and hind limbs in chimpanzee (Pan troglodytes) and human bipedal walking","volume":"86","author":"O'Neill","year":"2015","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C52","doi-asserted-by":"publisher","first-page":"20180205","DOI":"10.1098\/rsif.2018.0205","article-title":"Three-dimensional kinematics and the origin of the hominin walking stride","volume":"15","author":"O'Neill","year":"2018","journal-title":"J. R. Soc. Interface"},{"key":"2026060504040508600_JEB251135C53","doi-asserted-by":"publisher","first-page":"639","DOI":"10.1002\/ajpa.20192","article-title":"Knuckle-walking anteater: a convergence test of adaptation for purported knuckle-walking features of African Hominidae","volume":"128","author":"Orr","year":"2005","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C54","doi-asserted-by":"publisher","first-page":"382","DOI":"10.1002\/ar.23507","article-title":"Locomotor hand postures, carpal kinematics during wrist extension, and associated morphology in anthropoid primates","volume":"300","author":"Orr","year":"2017","journal-title":"Anat. Rec."},{"key":"2026060504040508600_JEB251135C55","doi-asserted-by":"publisher","first-page":"102","DOI":"10.1016\/j.jhevol.2017.10.002","article-title":"Kinematics of the anthropoid os centrale and the functional consequences of scaphoid-centrale fusion in African apes and hominins","volume":"114","author":"Orr","year":"2018","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C56","doi-asserted-by":"publisher","first-page":"e24728","DOI":"10.1002\/ajpa.24728","article-title":"Carpal kinematics and morphological correlates of wrist ulnar deviation in nonhuman anthropoid primates","volume":"183","author":"Orr","year":"2023","journal-title":"Am. J. Biol. Anthropol."},{"key":"2026060504040508600_JEB251135C57","doi-asserted-by":"publisher","first-page":"401","DOI":"10.1146\/annurev-bioeng-070909-105259","article-title":"Muscle and joint function in human locomotion","volume":"12","author":"Pandy","year":"2010","journal-title":"Annu. Rev. Biomed. Eng."},{"key":"2026060504040508600_JEB251135C58","doi-asserted-by":"publisher","first-page":"92","DOI":"10.1002\/ajpa.21039","article-title":"Not so fast: speed effects on forelimb kinematics in cercopithecine monkeys and implications for digitigrade postures in primates","volume":"140","author":"Patel","year":"2009","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C59","doi-asserted-by":"publisher","first-page":"222","DOI":"10.1002\/ajpa.21138","article-title":"The interplay between speed, kinetics, and hand postures during primate terrestrial locomotion","volume":"141","author":"Patel","year":"2010","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C60","doi-asserted-by":"publisher","first-page":"320","DOI":"10.1016\/j.jhevol.2010.01.001","article-title":"Functional morphology of cercopithecoid primate metacarpals","volume":"58","author":"Patel","year":"2010","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C61","doi-asserted-by":"publisher","first-page":"130","DOI":"10.1016\/j.jhevol.2006.08.007","article-title":"Bone density spatial patterns in the distal radius reflect habitual hand postures adopted by quadrupedal primates","volume":"52","author":"Patel","year":"2007","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C62","doi-asserted-by":"publisher","first-page":"191","DOI":"10.1007\/s10764-010-9394-6","article-title":"Distal forelimb kinematics in Erythrocebus patas and Papio anubis during walking and galloping","volume":"31","author":"Patel","year":"2010","journal-title":"Int. J. Primatol."},{"key":"2026060504040508600_JEB251135C63","doi-asserted-by":"publisher","first-page":"115","DOI":"10.1242\/jeb.063107","article-title":"Electromyography of wrist and finger flexor muscles in olive baboons (Papio anubis)","volume":"215","author":"Patel","year":"2012","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C64","first-page":"245","article-title":"Limbs in mammalian evolution","volume-title":"Fins into Limbs: Evolution, Development, and Transformation","author":"Polly","year":"2007"},{"key":"2026060504040508600_JEB251135C65","doi-asserted-by":"publisher","first-page":"295","DOI":"10.1007\/s10764-005-9011-2","article-title":"Ontogeny of ranging in wild chimpanzees","volume":"27","author":"Pontzer","year":"2006","journal-title":"Int. J. Primatol."},{"key":"2026060504040508600_JEB251135C66","doi-asserted-by":"publisher","first-page":"64","DOI":"10.1016\/j.jhevol.2013.10.002","article-title":"Bipedal and quadrupedal locomotion in chimpanzees","volume":"66","author":"Pontzer","year":"2014","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C67","first-page":"34","article-title":"Functional anatomy of the upper extremity","volume-title":"The Chimpanzee","author":"Preuschoft","year":"1973"},{"key":"2026060504040508600_JEB251135C68","doi-asserted-by":"publisher","first-page":"333","DOI":"10.1111\/j.1469-7793.2001.00333.x","article-title":"Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications","volume":"537","author":"Proske","year":"2001","journal-title":"J. Physiol."},{"key":"2026060504040508600_JEB251135C69","doi-asserted-by":"publisher","first-page":"3526","DOI":"10.1038\/s41598-020-60590-6","article-title":"The biomechanical importance of the scaphoid-centrale fusion during simulated knuckle-walking and its implications for human locomotor evolution","volume":"10","author":"P\u00fcschel","year":"2020","journal-title":"Sci. Rep."},{"key":"2026060504040508600_JEB251135C70","doi-asserted-by":"publisher","first-page":"808","DOI":"10.1038\/s41559-021-01431-1","article-title":"Divergence-time estimates for hominins provide insight into encephalization and body mass trends in human evolution","volume":"5","author":"P\u00fcschel","year":"2021","journal-title":"Nat. Ecol. Evol."},{"key":"2026060504040508600_JEB251135C72","doi-asserted-by":"publisher","first-page":"382","DOI":"10.1038\/35006045","article-title":"Evidence that humans evolved from a knuckle-walking ancestor","volume":"404","author":"Richmond","year":"2000","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C73","doi-asserted-by":"publisher","first-page":"70","DOI":"10.1002\/ajpa.10019","article-title":"Origin of human bipedalism: the knuckle-walking hypothesis revisited","volume":"116","author":"Richmond","year":"2001","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C74","doi-asserted-by":"publisher","first-page":"312","DOI":"10.1093\/icb\/icn056","article-title":"Interpreting muscle function from EMG: lessons learned from direct measurements of muscle force","volume":"48","author":"Roberts","year":"2008","journal-title":"Integr. Comp. Biol."},{"key":"2026060504040508600_JEB251135C75","doi-asserted-by":"publisher","first-page":"2044","DOI":"10.1249\/MSS.0b013e3181a8c702","article-title":"Is bone's response to mechanical signals dominated by muscle forces","volume":"41","author":"Robling","year":"2009","journal-title":"Med. Sci. Sports Exerc."},{"key":"2026060504040508600_JEB251135C76","doi-asserted-by":"publisher","first-page":"jeb170910","DOI":"10.1242\/jeb.170910","article-title":"Hand pressures during arboreal locomotion in captive bonobos (Pan paniscus)","volume":"221","author":"Samuel","year":"2018","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C77","doi-asserted-by":"publisher","first-page":"29","DOI":"10.1002\/ajpa.24477","article-title":"The ontogeny of knuckle-walking and dorsal metacarpal ridge prominence in chimpanzees","volume":"178","author":"Sarringhaus","year":"2022","journal-title":"Am. J. Biol. Anthropol."},{"key":"2026060504040508600_JEB251135C78","doi-asserted-by":"publisher","first-page":"2780","DOI":"10.1016\/j.jbiomech.2010.06.011","article-title":"Individual muscle contributions to the axial knee joint contact force during normal walking","volume":"43","author":"Sasaki","year":"2010","journal-title":"J. Biomech."},{"key":"2026060504040508600_JEB251135C79","doi-asserted-by":"publisher","first-page":"1141","DOI":"10.1111\/2041-210X.13434","article-title":"Robustness of linear mixed-effects models to violations of distributional assumptions","volume":"11","author":"Schielzeth","year":"2020","journal-title":"Methods Ecol. Evol."},{"key":"2026060504040508600_JEB251135C80","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1007\/978-1-4939-3646-5_13","article-title":"Patterns, variability, and flexibility of hand posture during locomotion in primates","volume-title":"The Evolution of the Primate Hand","author":"Schmitt","year":"2016"},{"key":"2026060504040508600_JEB251135C81","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/j.cub.2015.08.016","article-title":"Humans can continuously optimize energetic cost during walking report humans can continuously optimize energetic cost during walking","volume":"25","author":"Selinger","year":"2015","journal-title":"Curr. Biol."},{"key":"2026060504040508600_JEB251135C82","doi-asserted-by":"publisher","first-page":"177","DOI":"10.1002\/(SICI)1096-8644(199702)102:2&lt;177::AID-AJPA3&gt;3.0.CO;2-W","article-title":"Interlimb coordination, gait, and neural control of quadrupedalism in chimpanzees","volume":"102","author":"Shapiro","year":"1997","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C83","doi-asserted-by":"publisher","first-page":"293","DOI":"10.1126\/science.259.5093.293.b","article-title":"Knuckle-walking ancestors","volume":"259","author":"Shea","year":"1993","journal-title":"Science"},{"key":"2026060504040508600_JEB251135C84","doi-asserted-by":"publisher","first-page":"496","DOI":"10.1002\/ar.23743","article-title":"Why do knuckle-walking African apes knuckle-walk","volume":"301","author":"Simpson","year":"2018","journal-title":"Anat. Rec."},{"key":"2026060504040508600_JEB251135C85","doi-asserted-by":"publisher","first-page":"12265","DOI":"10.1073\/pnas.0703267104","article-title":"Chimpanzee locomotor energetics and the origin of human bipedalism","volume":"104","author":"Sockol","year":"2007","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"2026060504040508600_JEB251135C86","doi-asserted-by":"publisher","first-page":"72","DOI":"10.1038\/nature04113","article-title":"Computer optimization of a minimal biped model discovers walking and running","volume":"439","author":"Srinivasan","year":"2005","journal-title":"Nature"},{"key":"2026060504040508600_JEB251135C87","doi-asserted-by":"publisher","first-page":"11335","DOI":"10.1038\/s41598-021-90058-0","article-title":"A three-dimensional musculoskeletal model of the dog","volume":"11","author":"Stark","year":"2021","journal-title":"Sci. Rep."},{"key":"2026060504040508600_JEB251135C88","doi-asserted-by":"publisher","first-page":"279","DOI":"10.1002\/ajpa.1330600302","article-title":"The locomotor anatomy of Australopithecus afarensis","volume":"60","author":"Stern","year":"1983","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C89","first-page":"498","article-title":"Electromyography of some muscles of the upper limb in Ateles and Lagothrix","volume":"20","author":"Stern","year":"1977","journal-title":"Yearb. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C90","doi-asserted-by":"publisher","first-page":"13","DOI":"10.1002\/ajpa.1330520104","article-title":"An electromyographic study of the pectoralis major in Atelines and Hylobates, with special reference to the evolution of a pars clavicularis","volume":"52","author":"Stern","year":"1980","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C91","doi-asserted-by":"publisher","first-page":"311","DOI":"10.1002\/ajpa.1330510303","article-title":"Functional and morphological affinities of the subadult hand (O.H. 7) from Olduvai Gorge","volume":"51","author":"Susman","year":"1979","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C92","doi-asserted-by":"publisher","first-page":"565","DOI":"10.1002\/ajpa.1330500408","article-title":"Telemetered electromyography of flexor digitorum profundus and flexor digitorum superficialis in Pan troglodytes and implications for interpretation of the O. H. 7 hand","volume":"50","author":"Susman","year":"1979","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C93","doi-asserted-by":"publisher","first-page":"389","DOI":"10.1002\/aja.1001570407","article-title":"EMG of the interosseous and lumbrical muscles in the chimpanzee (Pan troglodytes) hand during locomotion","volume":"157","author":"Susman","year":"1980","journal-title":"Am. J. Anat."},{"key":"2026060504040508600_JEB251135C94","doi-asserted-by":"publisher","first-page":"477","DOI":"10.1002\/ajpa.1330830409","article-title":"Curvature of the forelimb bones of anthropoid primates: overall allometric patterns and specializations in suspensory species","volume":"83","author":"Swartz","year":"1990","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C95","doi-asserted-by":"publisher","first-page":"jeb224360","DOI":"10.1242\/jeb.224360","article-title":"The biomechanics of knuckle-walking: 3-D kinematics of the chimpanzee and macaque wrist, hand, and fingers","volume":"223","author":"Thompson","year":"2020","journal-title":"J. Exp. Biol."},{"key":"2026060504040508600_JEB251135C96","doi-asserted-by":"publisher","first-page":"84","DOI":"10.1002\/ajpa.23404","article-title":"Unexpected terrestrial hand posture diversity in wild mountain gorillas","volume":"166","author":"Thompson","year":"2018","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C97","doi-asserted-by":"publisher","first-page":"15","DOI":"10.1016\/j.jhevol.2018.09.005","article-title":"Great ape thorax and shoulder configuration\u2014an adaptation for arboreality or knuckle-walking?","volume":"125","author":"Thompson","year":"2018","journal-title":"J. Hum. Evol."},{"key":"2026060504040508600_JEB251135C98","doi-asserted-by":"publisher","first-page":"179","DOI":"10.1002\/(SICI)1096-8644(199910)110:2&lt;179::AID-AJPA5&gt;3.0.CO;2-Z","article-title":"Dimensions and moment arms of the hind- and forelimb muscles of common chimpanzees (Pan troglodytes)","volume":"110","author":"Thorpe","year":"1999","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C99","doi-asserted-by":"publisher","first-page":"433","DOI":"10.1292\/jvms1939.35.433","article-title":"Electromyographic and joint-mechanical studies in quadrupedal locomotion I. walk","volume":"35","author":"Tokuriki","year":"1973","journal-title":"Jpn. J. Vet. Sci."},{"key":"2026060504040508600_JEB251135C100","doi-asserted-by":"publisher","first-page":"171","DOI":"10.1002\/ajpa.1330260207","article-title":"Knuckle-walking and the evolution of hominoid hands","volume":"26","author":"Tuttle","year":"1967","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C101","doi-asserted-by":"publisher","first-page":"953","DOI":"10.1126\/science.166.3908.953","article-title":"Knuckle-walking and the problem of human origins","volume":"166","author":"Tuttle","year":"1969","journal-title":"Science"},{"key":"2026060504040508600_JEB251135C102","first-page":"293","article-title":"Electromyography of forearm musculature in gorilla and problems related to knuckle-walking","volume-title":"Primate Locomotion","author":"Tuttle","year":"1974"},{"key":"2026060504040508600_JEB251135C103","doi-asserted-by":"publisher","first-page":"255","DOI":"10.1002\/ajpa.1330370210","article-title":"Electromyography of knuckle-walking: results of four experiments on the forearm of Pan gorilla","volume":"37","author":"Tuttle","year":"1972","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C104","doi-asserted-by":"publisher","first-page":"75","DOI":"10.1002\/ajpa.1330610108","article-title":"Electromyography of brachial muscles in Pan troglodytes and Pongo pygmaeus","volume":"61","author":"Tuttle","year":"1983","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C105","doi-asserted-by":"publisher","first-page":"197","DOI":"10.1002\/(SICI)1520-6505(1999)7:6&lt;197::AID-EVAN4&gt;3.0.CO;2-T","article-title":"The new hominid species Australopithecus anamensis","volume":"7","author":"Ward","year":"1999","journal-title":"Evol. Anthropol."},{"key":"2026060504040508600_JEB251135C106","doi-asserted-by":"publisher","first-page":"4877","DOI":"10.1073\/pnas.1403659111","article-title":"Neither chimpanzee nor human, Ardipithecus reveals the surprising ancestry of both","volume":"112","author":"White","year":"2015","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"2026060504040508600_JEB251135C107","first-page":"96","article-title":"Aspects of the anthropoid wrist and hand","volume-title":"Postcranial Adaptations in Nonhuman Primates","author":"Whitehead","year":"1993"},{"key":"2026060504040508600_JEB251135C108","doi-asserted-by":"publisher","first-page":"58","DOI":"10.1002\/ajpa.24684","article-title":"African apes and the evolutionary history of orthogrady and bipedalism","volume":"181","author":"Williams","year":"2023","journal-title":"Am. J. Biol. Anthropol."},{"key":"2026060504040508600_JEB251135C109","doi-asserted-by":"publisher","first-page":"394","DOI":"10.1002\/ajpa.20994","article-title":"Manual digital pressures during knuckle-walking in chimpanzees (Pan troglodytes)","volume":"139","author":"Wunderlich","year":"2009","journal-title":"Am. J. Phys. Anthropol."},{"key":"2026060504040508600_JEB251135C110","doi-asserted-by":"publisher","first-page":"755","DOI":"10.1038\/nature03397","article-title":"Virtual cranial reconstruction of Sahelanthropus tchadensis","volume":"434","author":"Zollikofer","year":"2005","journal-title":"Nature"}],"container-title":["Journal of Experimental Biology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.biologists.com\/jeb\/article-pdf\/doi\/10.1242\/jeb.251135\/3700591\/jeb251135.pdf","content-type":"application\/pdf","content-version":"am","intended-application":"syndication"},{"URL":"https:\/\/journals.biologists.com\/jeb\/article-pdf\/doi\/10.1242\/jeb.251135\/3702433\/jeb251135.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/journals.biologists.com\/jeb\/article-pdf\/doi\/10.1242\/jeb.251135\/3702433\/jeb251135.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T08:04:18Z","timestamp":1780646658000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.biologists.com\/jeb\/article\/229\/11\/jeb251135\/371898\/The-biomechanics-of-knuckle-walking-II-muscle"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,1]]},"references-count":107,"journal-issue":{"issue":"11","published-print":{"date-parts":[[2026,6,1]]}},"URL":"https:\/\/doi.org\/10.1242\/jeb.251135","relation":{},"ISSN":["0022-0949","1477-9145"],"issn-type":[{"value":"0022-0949","type":"print"},{"value":"1477-9145","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,1]]},"article-number":"jeb251135"}}