{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,14]],"date-time":"2026-05-14T20:05:05Z","timestamp":1778789105102,"version":"3.51.4"},"reference-count":43,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2023,5,6]],"date-time":"2023-05-06T00:00:00Z","timestamp":1683331200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Joint quasi-stiffness has been often used to inform exoskeleton design. Further understanding of hip quasi-stiffness is needed to design hip exoskeletons. Of interest are wearer responses to walking speed changes with added mass of the exoskeleton. This study analyzed hip quasi-stiffness at 3 walking speed levels and 9 added mass distributions among 13 young and 16 middle-aged adults during mid-stance hip extension and late-stance hip flexion. Compared to young adults, middle-aged adults maintained a higher quasi-stiffness with a smaller range. For a faster walking speed, both age groups increased extension and flexion quasi-stiffness. With mass evenly distributed on the pelvis and thighs or biased to the pelvis, both groups maintained or increased extension quasi-stiffness. With mass biased to the thighs, middle-aged adults maintained or decreased extension quasi-stiffness while young adults increased it. Young adults decreased flexion quasi-stiffness with added mass but not in any generalizable pattern with mass amounts or distributions. Conversely, middle-aged adults maintained or decreased flexion quasi-stiffness with even distribution on the pelvis and thighs or biased to the pelvis, while no change occurred if biased to the thighs. In conclusion, these results can guide the design of a hip exoskeleton\u2019s size and mass distribution according to the intended user\u2019s age.<\/jats:p>","DOI":"10.3390\/s23094517","type":"journal-article","created":{"date-parts":[[2023,5,8]],"date-time":"2023-05-08T02:29:22Z","timestamp":1683512962000},"page":"4517","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Effects of Walking Speed and Added Mass on Hip Joint Quasi-Stiffness in Healthy Young and Middle-Aged Adults"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3019-2977","authenticated-orcid":false,"given":"Shanpu","family":"Fang","sequence":"first","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, University of Dayton, Dayton, OH 45469, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4657-6318","authenticated-orcid":false,"given":"Vinayak","family":"Vijayan","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, University of Dayton, Dayton, OH 45469, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Megan E.","family":"Reissman","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, University of Dayton, Dayton, OH 45469, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3553-0733","authenticated-orcid":false,"given":"Allison L.","family":"Kinney","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, University of Dayton, Dayton, OH 45469, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Timothy","family":"Reissman","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Aerospace Engineering, University of Dayton, Dayton, OH 45469, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"562","DOI":"10.1109\/TBME.2012.2230261","article-title":"The Difference between Stiffness and Quasi-Stiffness in the Context of Biomechanical Modeling","volume":"60","author":"Rouse","year":"2013","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"5568","DOI":"10.1038\/s41598-019-41750-9","article-title":"Comparison of Lower Extremity Joint Mechanics between Healthy Active Young and Middle Age People in Walking and Running Gait","volume":"9","author":"Jin","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/1050-6411(96)00030-2","article-title":"Moment-Angle Relationship at Lower Limb Joints during Human Walking at Different Velocities","volume":"6","author":"Frigo","year":"1996","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1185","DOI":"10.1016\/j.humov.2011.02.009","article-title":"Dynamics of the Ankle Joint Analyzed through Moment-Angle Loops during Human Walking: Gender and Age Effects","volume":"30","author":"Crenna","year":"2011","journal-title":"Hum. Mov. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"311","DOI":"10.1016\/j.gaitpost.2018.03.031","article-title":"Net Ankle Quasi-Stiffness Is Influenced by Walking Speed but Not Age for Older Adult Women","volume":"62","author":"Collins","year":"2018","journal-title":"Gait Posture"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Shamaei, K., Sawicki, G.S., and Dollar, A.M. (2013). Estimation of Quasi-Stiffness of the Human Hip in the Stance Phase of Walking. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0081841"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Shamaei, K., Sawicki, G.S., and Dollar, A.M. (2013). Estimation of Quasi-Stiffness of the Human Knee in the Stance Phase of Walking. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0059993"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Shamaei, K., Sawicki, G.S., and Dollar, A.M. (2013). Estimation of Quasi-Stiffness and Propulsive Work of the Human Ankle in the Stance Phase of Walking. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0059935"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1889","DOI":"10.1016\/j.knee.2020.09.019","article-title":"Quasi-Stiffness of the Knee Joint Is Influenced by Walking on a Destabilising Terrain","volume":"27","author":"Foster","year":"2020","journal-title":"Knee"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"MacLean, M.K., and Ferris, D.P. (2022). Effects of Simulated Reduced Gravity and Walking Speed on Ankle, Knee, and Hip Quasi-Stiffness in Overground Walking. PLoS ONE, 17.","DOI":"10.1371\/journal.pone.0271927"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"e7487","DOI":"10.7717\/peerj.7487","article-title":"Ankle and Midtarsal Joint Quasi-Stiffness during Walking with Added Mass","volume":"2019","author":"Kern","year":"2019","journal-title":"PeerJ"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"101742","DOI":"10.1016\/j.foot.2020.101742","article-title":"Test-Retest Reliability of a Clinical Foot Assessment Device for Measuring First Metatarsophalangeal Joint Quasi-Stiffness","volume":"45","author":"Leow","year":"2020","journal-title":"Foot"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s13047-016-0173-2","article-title":"A Novel Method of Measuring Passive Quasi-Stiffness in the First Metatarsophalangeal Joint","volume":"9","author":"Heng","year":"2016","journal-title":"J. Foot Ankle Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"381","DOI":"10.1016\/j.isatra.2020.08.036","article-title":"Novel Adaptive Impedance Control for Exoskeleton Robot for Rehabilitation Using a Nonlinear Time-Delay Disturbance Observer","volume":"108","author":"Brahmi","year":"2021","journal-title":"ISA Trans."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1675","DOI":"10.1109\/TIE.2016.2580123","article-title":"Assist-as-Needed Control of an Intrinsically Compliant Robotic Gait Training Orthosis","volume":"64","author":"Hussain","year":"2017","journal-title":"IEEE Trans. Ind. Electron."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1142\/S0219843607001126","article-title":"A Quasi-Passive Leg Exoskeleton for Load-Carrying Augmentation","volume":"4","author":"Walsh","year":"2007","journal-title":"Int. J. Hum. Robot."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Fang, S., Vijayan, V., Reissman, M.E., Kinney, A.L., and Reissman, T. (2022). How Do Joint Kinematics and Kinetics Change When Walking Overground with Added Mass on the Lower Body?. Sensors, 22.","DOI":"10.3390\/s22239177"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Vijayan, V., Fang, S., Reissman, T., Reissman, M.E., and Kinney, A.L. (2022). How Does Added Mass Affect the Gait of Middle-Aged Adults? An Assessment Using Statistical Parametric Mapping. Sensors, 22.","DOI":"10.3390\/s22166154"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"116","DOI":"10.1016\/j.gaitpost.2021.11.026","article-title":"Spatiotemporal and Muscle Activation Adaptations during Overground Walking in Response to Lower Body Added Mass","volume":"92","author":"Vijayan","year":"2022","journal-title":"Gait Posture"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s12984-020-00663-9","article-title":"The Exoskeleton Expansion: Improving Walking and Running Economy","volume":"17","author":"Sawicki","year":"2020","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_21","first-page":"605","article-title":"Mechanics and Energetics of Load Carriage during Human Walking","volume":"217","author":"Huang","year":"2014","journal-title":"J. Exp. Biol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1016\/j.gaitpost.2012.07.031","article-title":"Do Thigh Circumference and Mass Changes Alter Knee Biomechanics during Walking?","volume":"37","author":"Westlake","year":"2013","journal-title":"Gait Posture"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1259","DOI":"10.1016\/j.jbiomech.2011.02.016","article-title":"Effects of Load Carriage and Fatigue on Gait Characteristics","volume":"44","author":"Qu","year":"2011","journal-title":"J. Biomech."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1080\/00140139.2016.1206624","article-title":"Influence of a 12.8-Km Military Load Carriage Activity on Lower Limb Gait Mechanics and Muscle Activity","volume":"60","author":"Rice","year":"2017","journal-title":"Ergonomics"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e15","DOI":"10.1017\/wtc.2022.11","article-title":"Current Developments of Robotic Hip Exoskeleton toward Sensing, Decision, and Actuation: A Review","volume":"3","author":"Yang","year":"2022","journal-title":"Wearable Technol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1796","DOI":"10.1109\/TNSRE.2022.3187056","article-title":"Passive Knee Exoskeleton Increases Vertical Jump Height","volume":"30","author":"Ostraich","year":"2022","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"72","DOI":"10.3389\/frobt.2018.00072","article-title":"Passive Back Support Exoskeleton Improves Range of Motion Using Flexible Beams","volume":"5","author":"Koopman","year":"2018","journal-title":"Front. Robot. AI"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2026","DOI":"10.1109\/TNSRE.2018.2872889","article-title":"Reducing the Energy Cost of Human Running Using an Unpowered Exoskeleton","volume":"26","author":"Nasiri","year":"2018","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1186\/s12984-019-0599-4","article-title":"Reducing the Energy Cost of Walking in Older Adults Using a Passive Hip Flexion Device","volume":"16","author":"Panizzolo","year":"2019","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"jeb202895","DOI":"10.1242\/jeb.202895","article-title":"Connecting the Legs with a Spring Improves Human Running Economy","volume":"222","author":"Simpson","year":"2019","journal-title":"J. Exp. Biol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1242\/jeb.017269","article-title":"Powered Ankle Exoskeletons Reveal the Metabolic Cost of Plantar Flexor Mechanical Work during Walking with Longer Steps at Constant Step Frequency","volume":"212","author":"Sawicki","year":"2009","journal-title":"J. Exp. Biol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Kim, D.-S., Lee, H.-J., Lee, S.-H., Chang, W.H., Jang, J., Choi, B.-O., Ryu, G.-H., and Kim, Y.-H. (2018). A Wearable Hip-Assist Robot Reduces the Cardiopulmonary Metabolic Energy Expenditure during Stair Ascent in Elderly Adults: A Pilot Cross-Sectional Study. BMC Geriatr., 18.","DOI":"10.1186\/s12877-018-0921-1"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Kim, J., Heimgartner, R., Lee, G., Karavas, N., Perry, D., Ryan, D.L., Eckert-Erdheim, A., Murphy, P., Choe, D.K., and Galiana, I. (2018, January 21\u201325). Autonomous and Portable Soft Exosuit for Hip Extension Assistance with Online Walking and Running Detection Algorithm. Proceedings of the 2018 IEEE International Conference on Robotics and Automation (ICRA), Brisbane, Australia.","DOI":"10.1109\/ICRA.2018.8460474"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1128","DOI":"10.1109\/TNSRE.2014.2324153","article-title":"Human-Robot Interaction: Kinematics and Muscle Activity inside a Powered Compliant Knee Exoskeleton","volume":"22","author":"Knaepen","year":"2014","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"380","DOI":"10.1109\/TNSRE.2005.848628","article-title":"Patient-Cooperative Strategies for Robot-Aided Treadmill Training: First Experimental Results","volume":"13","author":"Riener","year":"2005","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"360","DOI":"10.1109\/TNSRE.2008.925074","article-title":"The Effects on Kinematics and Muscle Activity of Walking in a Robotic Gait Trainer during Zero-Force Control","volume":"16","author":"Veneman","year":"2008","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_37","first-page":"26","article-title":"Recent Developments and Challenges of Lower Extremity Exoskeletons","volume":"5","author":"Chen","year":"2016","journal-title":"J. Orthop. Transl."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"936","DOI":"10.1109\/LRA.2021.3136240","article-title":"Underactuated Soft Hip Exosuit Based on Adaptive Oscillators to Assist Human Locomotion","volume":"7","author":"Tricomi","year":"2022","journal-title":"IEEE Robot. Autom. Lett."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1783","DOI":"10.1038\/s41591-021-01515-2","article-title":"Powered Hip Exoskeleton Improves Walking Economy in Individuals with Above-Knee Amputation","volume":"27","author":"Ishmael","year":"2021","journal-title":"Nat. Med."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"625","DOI":"10.1007\/978-3-319-14418-4_32","article-title":"Interpreting Joint Moments and Powers in Gait","volume":"Volume 1\u20133","author":"Sloot","year":"2018","journal-title":"Handbook of Human Motion"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1093\/gerona\/50A.Special_Issue.11","article-title":"Human Aging, Muscle Mass, and Fiber Type Composition","volume":"50A","author":"Evans","year":"1995","journal-title":"J. Gerontol. Ser. A Biol. Sci. Med. Sci."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/j.jbiomech.2018.11.036","article-title":"Lower-Limb Joint Work and Power Are Modulated during Load Carriage Based on Load Configuration and Walking Speed","volume":"83","author":"Lenton","year":"2019","journal-title":"J. Biomech."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1177\/0018720819868122","article-title":"Exoscore: A Design Tool to Evaluate Factors Associated with Technology Acceptance of Soft Lower Limb Exosuits by Older Adults","volume":"62","author":"Shore","year":"2020","journal-title":"Hum. Factors"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/9\/4517\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:30:10Z","timestamp":1760124610000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/9\/4517"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,5,6]]},"references-count":43,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2023,5]]}},"alternative-id":["s23094517"],"URL":"https:\/\/doi.org\/10.3390\/s23094517","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,5,6]]}}}