{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T03:59:16Z","timestamp":1776916756211,"version":"3.51.2"},"reference-count":57,"publisher":"Public Library of Science (PLoS)","issue":"5","license":[{"start":{"date-parts":[[2024,5,16]],"date-time":"2024-05-16T00:00:00Z","timestamp":1715817600000},"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>\n                    Capturing human locomotion in nearly any environment or context is becoming increasingly feasible with wearable sensors, giving access to commonly encountered walking conditions. While important in expanding our understanding of locomotor biomechanics, these more variable environments present challenges to identify changes in data due to person-level factors among the varying environment-level factors. Our study examined foot-specific biomechanics while walking on terrain commonly encountered with the goal of understanding the extent to which these variables change due to terrain. We recruited healthy adults to walk at self-selected speeds on stairs, flat ground, and both shallow and steep sloped terrain. A pair of inertial measurement units were embedded in both shoes to capture foot biomechanics while walking. Foot orientation was calculated using a strapdown procedure and foot trajectory was determined by double integrating the linear acceleration. Stance time, swing time, cadence, sagittal and frontal orientations, stride length and width were extracted as discrete variables. These data were compared within-participant and across terrain conditions. The physical constraints of the stairs resulted in shorter stride lengths, less time spent in swing, toe-first foot contact, and higher variability during stair ascent specifically (\n                    <jats:italic>p<\/jats:italic>\n                    &lt;0.05). Stride lengths increased when ascending compared to descending slopes, and the sagittal foot angle at initial contact was greatest in the steep slope descent condition (\n                    <jats:italic>p<\/jats:italic>\n                    &lt;0.05). No differences were found between conditions for horizontal foot angle in midstance (p\u22650.067). Our results show that walking on slopes creates differential changes in foot biomechanics depending on whether one is descending or ascending, and stairs require different biomechanics and gait timing than slopes or flat ground. This may be an important factor to consider when making comparisons of real-world walking bouts, as greater proportions of one terrain feature in a data set could create bias in the outcomes. Classifying terrain in unsupervised walking datasets would be helpful to avoid comparing metrics from different walking terrain scenarios.\n                  <\/jats:p>","DOI":"10.1371\/journal.pone.0293691","type":"journal-article","created":{"date-parts":[[2024,5,16]],"date-time":"2024-05-16T13:31:42Z","timestamp":1715866302000},"page":"e0293691","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":3,"title":["Foot orientation and trajectory variability in locomotion: Effects of real-world terrain"],"prefix":"10.1371","volume":"19","author":[{"given":"Emma","family":"Gibson","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Greg","family":"Douglas","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Katelyn","family":"Jeffries","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Julianne","family":"Delaurier","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Taylor","family":"Chestnut","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4709-7666","authenticated-orcid":true,"given":"Jesse M.","family":"Charlton","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2024,5,16]]},"reference":[{"issue":"1","key":"pone.0293691.ref001","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1093\/ptj\/72.1.45","article-title":"Foot trajectory in human gait: A precise and multifactorial motor control task","volume":"72","author":"DA Winter","year":"1992","journal-title":"Phys Ther"},{"issue":"8","key":"pone.0293691.ref002","doi-asserted-by":"crossref","first-page":"2752","DOI":"10.1093\/cercor\/bhx155","article-title":"Electrocorticographic encoding of human gait in the leg primary motor cortex","volume":"28","author":"CM McCrimmon","year":"2018","journal-title":"Cereb Cortex"},{"issue":"11","key":"pone.0293691.ref003","doi-asserted-by":"crossref","first-page":"1483","DOI":"10.1002\/mds.25669","article-title":"Neurophysiology of gait: from the spinal cord to the frontal lobe","volume":"28","author":"K. Takakusaki","year":"2013","journal-title":"Mov Disord"},{"issue":"4","key":"pone.0293691.ref004","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/0966-6362(96)82849-9","article-title":"Human balance and posture control during standing and walking.","volume":"3","author":"DA Winter","year":"1995","journal-title":"Gait Posture"},{"issue":"8","key":"pone.0293691.ref005","doi-asserted-by":"crossref","first-page":"2329","DOI":"10.1007\/s00221-017-4967-7","article-title":"Online adjustments of leg movements in healthy young and old","volume":"235","author":"Z Potocanac","year":"2017","journal-title":"Exp Brain Res"},{"issue":"12","key":"pone.0293691.ref006","doi-asserted-by":"crossref","first-page":"3349","DOI":"10.1007\/s00221-015-4401-y","article-title":"Quick foot placement adjustments during gait: direction matters","volume":"233","author":"W Hoogkamer","year":"2015","journal-title":"Exp Brain Res"},{"issue":"9","key":"pone.0293691.ref007","doi-asserted-by":"crossref","first-page":"917","DOI":"10.1177\/02783649922066655","article-title":"Stabilization of lateral motion in passive dynamic walking","volume":"18","author":"AD Kuo","year":"1999","journal-title":"Int J Robot Res"},{"key":"pone.0293691.ref008","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/j.gaitpost.2022.12.015","article-title":"Comparison of over-ground and treadmill perturbations for simulation of real-world slips and trips: A systematic review.","volume":"100","author":"T Siragy","year":"2023","journal-title":"Gait Posture."},{"key":"pone.0293691.ref009","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1016\/j.gaitpost.2018.04.047","article-title":"The use of wearable devices for walking and running gait analysis outside of the lab: A systematic review.","volume":"63","author":"LC Benson","year":"2018","journal-title":"Gait Posture."},{"issue":"1","key":"pone.0293691.ref010","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1016\/j.gaitpost.2014.03.189","article-title":"Quantified self and human movement: a review on the clinical impact of wearable sensing and feedback for gait analysis and intervention.","volume":"40","author":"PB Shull","year":"2014","journal-title":"Gait Posture."},{"key":"pone.0293691.ref011","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/j.gaitpost.2017.10.024","article-title":"Moving from laboratory to real life conditions: Influence on the assessment of variability and stability of gait.","volume":"59","author":"P Tamburini","year":"2018","journal-title":"Gait Posture."},{"issue":"6","key":"pone.0293691.ref012","doi-asserted-by":"crossref","first-page":"e0269567","DOI":"10.1371\/journal.pone.0269567","article-title":"The placement of foot-mounted IMU sensors does affect the accuracy of spatial parameters during regular walking.","volume":"17","author":"A K\u00fcderle","year":"2022","journal-title":"PloS ONE"},{"issue":"9","key":"pone.0293691.ref013","doi-asserted-by":"crossref","first-page":"1940","DOI":"10.3390\/s17091940","article-title":"Benchmarking foot trajectory estimation methods for mobile gait analysis.","volume":"17","author":"J Hannink","year":"2017","journal-title":"Sensors"},{"issue":"3","key":"pone.0293691.ref014","doi-asserted-by":"crossref","first-page":"486","DOI":"10.1109\/TBME.2004.840727","article-title":"Assessment of walking features from foot inertial sensing","volume":"52","author":"AM Sabatini","year":"2005","journal-title":"IEEE Trans Biomed Eng"},{"key":"pone.0293691.ref015","article-title":"A review of foot pose and trajectory estimation methods using inertial and auxiliary sensors for kinematic gait analysis.","author":"N Okkalidis","year":"2020","journal-title":"Biomed Tech."},{"issue":"37","key":"pone.0293691.ref016","first-page":"1","article-title":"Foot progression angle estimation using a single foot-worn inertial sensor.","volume":"18","author":"FJ Wouda","year":"2021","journal-title":"J Neuroeng Rehabil"},{"key":"pone.0293691.ref017","doi-asserted-by":"crossref","first-page":"110","DOI":"10.1016\/j.gaitpost.2016.01.014","article-title":"Estimation of foot trajectory during human walking by a wearable inertial measurement unit mounted to the foot.","volume":"45","author":"N Kitagawa","year":"2016","journal-title":"Gait Posture."},{"key":"pone.0293691.ref018","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1109\/TNSRE.2020.3047402","article-title":"Magnetometer-free, IMU-based foot progression angle estimation for real-life walking conditions","volume":"29","author":"T Tan","year":"2021","journal-title":"IEEE Trans Neural Syst Rehabil Eng"},{"issue":"4","key":"pone.0293691.ref019","doi-asserted-by":"crossref","first-page":"974","DOI":"10.1016\/j.gaitpost.2013.05.012","article-title":"Measurement of foot placement and its variability with inertial sensors.","volume":"38","author":"JR Rebula","year":"2013","journal-title":"Gait Posture."},{"key":"pone.0293691.ref020","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1016\/j.gaitpost.2018.12.028","article-title":"What features of the built environment matter most for mobility? Using wearable sensors to capture real-time outdoor environment demand on gait performance","volume":"68","author":"E Twardzik","year":"2019","journal-title":"Gait Posture"},{"issue":"19","key":"pone.0293691.ref021","doi-asserted-by":"crossref","first-page":"6559","DOI":"10.3390\/s21196559","article-title":"An inertial sensor-based gait analysis pipeline for the assessment of real-world stair ambulation parameters.","volume":"21","author":"N Roth","year":"2021","journal-title":"Sensors"},{"issue":"4","key":"pone.0293691.ref022","doi-asserted-by":"crossref","first-page":"885","DOI":"10.1109\/TBME.2017.2724543","article-title":"An ambulatory gait monitoring system with activity classification and gait parameter calculation based on a single foot inertial sensor","volume":"65","author":"M Song","year":"2018","journal-title":"IEEE Trans Biomed Eng"},{"issue":"1","key":"pone.0293691.ref023","doi-asserted-by":"crossref","first-page":"e0228682","DOI":"10.1371\/journal.pone.0228682","article-title":"Human walking in the real world: Interactions between terrain type, gait parameters, and energy expenditure.","volume":"16","author":"DB Kowalsky","year":"2021","journal-title":"PloS ONE"},{"issue":"8","key":"pone.0293691.ref024","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/j.jbiomech.2017.07.012","article-title":"Validation of a smart shoe for estimating foot progression angle during walking gait","volume":"61","author":"H Xia","year":"2017","journal-title":"J Biomech"},{"key":"pone.0293691.ref025","doi-asserted-by":"crossref","first-page":"1566","DOI":"10.1109\/TNSRE.2023.3250612","article-title":"The number of steps for representative real-world, unsupervised walking data using a shoe-worn inertial sensor","volume":"31","author":"JM Charlton","year":"2023","journal-title":"IEEE Trans Neural Syst Rehabil Eng"},{"key":"pone.0293691.ref026","doi-asserted-by":"crossref","first-page":"105957","DOI":"10.1016\/j.clinbiomech.2023.105957","article-title":"Multi-day monitoring of foot progression angles during unsupervised, real-world walking in people with and without knee osteoarthritis.","volume":"105","author":"JM Charlton","year":"2023","journal-title":"Clin Biomech"},{"issue":"2","key":"pone.0293691.ref027","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/j.gaitpost.2012.07.012","article-title":"Quantitative estimation of foot-flat and stance phase of gait using foot-worn inertial sensors.","volume":"37","author":"B Mariani","year":"2013","journal-title":"Gait Posture"},{"key":"pone.0293691.ref028","first-page":"8","article-title":"Drift-free foot orientation estimation in running using wearable IMU.","author":"M Falbriard","year":"2020","journal-title":"Front Bioeng Biotechnol."},{"key":"pone.0293691.ref029","doi-asserted-by":"crossref","DOI":"10.3389\/fdgth.2021.736418","article-title":"Calibration-free gait assessment by foot-worn inertial sensors.","volume":"3","author":"D Laidig","year":"2021","journal-title":"Front Digit Health."},{"issue":"2","key":"pone.0293691.ref030","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1093\/biomet\/75.2.383","article-title":"A stagewise rejective multiple test procedure based on a modified bonferroni test","volume":"75","author":"G. Hommel","year":"1988","journal-title":"Biometrika"},{"issue":"4","key":"pone.0293691.ref031","doi-asserted-by":"crossref","first-page":"677","DOI":"10.1080\/00140139608964489","article-title":"The influence of surface slope on human gait characteristics: a study of urban pedestrians walking on an inclined surface.","volume":"39","author":"JIE Sun","year":"1996","journal-title":"Ergonomics."},{"issue":"23","key":"pone.0293691.ref032","doi-asserted-by":"crossref","first-page":"3717","DOI":"10.1242\/jeb.205.23.3717","article-title":"Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking.","volume":"205","author":"JM Donelan","year":"2002","journal-title":"J Exper Bio."},{"issue":"2","key":"pone.0293691.ref033","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1080\/14763140508522865","article-title":"Effect of walking speed on lower extremity joint loading in graded ramp walking.","volume":"4","author":"H Schwameder","year":"2005","journal-title":"Sport Biomech."},{"issue":"4","key":"pone.0293691.ref034","doi-asserted-by":"crossref","first-page":"293","DOI":"10.1007\/BF00430237","article-title":"Optimization of energy expenditure during level walking","volume":"33","author":"MY Zarrugh","year":"1974","journal-title":"Eur J Appl Physiol Occup Physiol"},{"issue":"1","key":"pone.0293691.ref035","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/S0966-6362(01)00181-3","article-title":"Postural adaptation to walking on inclined surfaces: I.","volume":"15","author":"A Leroux","year":"2002","journal-title":"Normal strategies. Gait Posture"},{"issue":"11","key":"pone.0293691.ref036","doi-asserted-by":"crossref","first-page":"1433","DOI":"10.1016\/S0021-9290(00)00101-9","article-title":"Active control of lateral balance in human walking","volume":"33","author":"CE Bauby","year":"2000","journal-title":"J Biomech"},{"issue":"6","key":"pone.0293691.ref037","doi-asserted-by":"crossref","first-page":"935","DOI":"10.1016\/j.jbiomech.2003.11.012","article-title":"Step width variability, but not step length variability or step time variability, discriminates gait of healthy young and older adults during treadmill locomotion","volume":"37","author":"TM Owings","year":"2004","journal-title":"J Biomech"},{"issue":"1","key":"pone.0293691.ref038","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1186\/1743-0003-2-21","article-title":"Too much or too little step width variability is associated with a fall history in older persons who walk at or near normal gait speed.","volume":"2","author":"JS Brach","year":"2005","journal-title":"J Neuroeng Rehabil."},{"issue":"11","key":"pone.0293691.ref039","doi-asserted-by":"crossref","first-page":"e0188500","DOI":"10.1371\/journal.pone.0188500","article-title":"Electrocortical correlates of human level-ground, slope, and stair walking.","volume":"12","author":"TP Luu","year":"2017","journal-title":"PloS ONE"},{"issue":"13","key":"pone.0293691.ref040","doi-asserted-by":"crossref","first-page":"1138","DOI":"10.1080\/00140130110085547","article-title":"Biomechanics of slips.","volume":"44","author":"MS Redfern","year":"2001","journal-title":"Ergonomics."},{"issue":"3","key":"pone.0293691.ref041","doi-asserted-by":"crossref","first-page":"352","DOI":"10.1080\/00140130601053479","article-title":"Kinematics of heelstrike during walking and carrying: implications for slip resistance testing.","volume":"50","author":"MA Holbein-Jenny","year":"2007","journal-title":"Ergonomics."},{"issue":"4","key":"pone.0293691.ref042","doi-asserted-by":"crossref","first-page":"1833","DOI":"10.1007\/s10694-023-01402-x","article-title":"Gait biomechanics while walking down an incline after exhaustion.","volume":"59","author":"A Halder","year":"2023","journal-title":"Fire Tech"},{"issue":"1","key":"pone.0293691.ref043","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/S0966-6362(01)00162-X","article-title":"Stair ascent and descent at different inclinations.","volume":"15","author":"R Riener","year":"2002","journal-title":"Gait Posture"},{"key":"pone.0293691.ref044","doi-asserted-by":"crossref","first-page":"315","DOI":"10.1016\/j.gaitpost.2021.12.002","article-title":"Foot kinematics and leg muscle activation patterns are altered in those with limited ankle dorsiflexion range of motion during incline walking.","volume":"92","author":"Y Kwon","year":"2022","journal-title":"Gait Posture"},{"key":"pone.0293691.ref045","doi-asserted-by":"crossref","first-page":"426","DOI":"10.1016\/j.gaitpost.2016.08.004","article-title":"The rotational profile: A study of lower limb axial torsion, hip rotation, and the foot progression angle in healthy adults","volume":"49","author":"D. Hudson","year":"2016","journal-title":"Gait Posture"},{"issue":"3","key":"pone.0293691.ref046","doi-asserted-by":"crossref","first-page":"436","DOI":"10.1016\/j.gaitpost.2006.10.008","article-title":"The influence of foot progression angle on the knee adduction moment during walking and stair climbing in pain free individuals with knee osteoarthritis","volume":"26","author":"M Guo","year":"2007","journal-title":"Gait Posture"},{"issue":"6","key":"pone.0293691.ref047","doi-asserted-by":"crossref","first-page":"779","DOI":"10.1016\/j.clinbiomech.2008.01.012","article-title":"Effect of foot rotation on knee kinetics and hamstring activation in older adults with and without signs of knee osteoarthritis.","volume":"23","author":"SK Lynn","year":"2008","journal-title":"Clin Biomech."},{"issue":"1","key":"pone.0293691.ref048","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.clinbiomech.2013.10.015","article-title":"Biomechanical mechanisms of toe-out gait performance in people with and without knee osteoarthritis.","volume":"29","author":"CK Cochrane","year":"2014","journal-title":"Clin Biomech"},{"issue":"2","key":"pone.0293691.ref049","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1038\/nrrheum.2010.212","article-title":"Conservative biomechanical strategies for knee osteoarthritis.","volume":"7","author":"ND Reeves","year":"2011","journal-title":"Nat Rev Rheumatol"},{"issue":"2","key":"pone.0293691.ref050","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1002\/acr.20380","article-title":"Gait modification strategies for altering medial knee joint load: A systematic review.","volume":"63","author":"M Simic","year":"2011","journal-title":"Arthrit Care Res"},{"issue":"4","key":"pone.0293691.ref051","doi-asserted-by":"crossref","first-page":"457","DOI":"10.1111\/j.1748-1716.1985.tb07612.x","article-title":"Changes in leg movements and muscle activity with speed of locomotion and mode of progression in humans","volume":"123","author":"J Nilsson","year":"1985","journal-title":"Acta Physiol Scand"},{"issue":"4","key":"pone.0293691.ref052","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1007\/s12283-012-0093-8","article-title":"Gyroscope-based assessment of temporal gait parameters during treadmill walking and running.","volume":"15","author":"D McGrath","year":"2012","journal-title":"Sports Eng"},{"issue":"12","key":"pone.0293691.ref053","doi-asserted-by":"crossref","first-page":"1372","DOI":"10.4236\/health.2010.212203","article-title":"Comparison of gait properties during level walking and stair ascent and descent with varying loads.","volume":"2","author":"T Demura","year":"2010","journal-title":"Health"},{"issue":"10","key":"pone.0293691.ref054","doi-asserted-by":"crossref","first-page":"950","DOI":"10.1016\/S0268-0033(03)00179-7","article-title":"Frontal and sagittal plane analyses of the stair climbing task in healthy adults aged over 40 years: what are the challenges compared to level walking?","volume":"18","author":"S Nadeau","year":"2003","journal-title":"Clin Biomech."},{"issue":"1","key":"pone.0293691.ref055","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/j.gaitpost.2014.09.022","article-title":"Age-related differences when walking downhill on different sloped terrains.","volume":"41","author":"P Scaglioni-Solano","year":"2015","journal-title":"Gait Posture"},{"issue":"4","key":"pone.0293691.ref056","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1016\/j.gaitpost.2007.09.005","article-title":"Age-related changes in gait for multi-surface terrain.","volume":"27","author":"DS Marigold","year":"2008","journal-title":"Gait Posture"},{"key":"pone.0293691.ref057","first-page":"2023.06.12.544651","article-title":"Understanding the Influence of Context on Real-World Walking Energetics.","author":"L Baroudi","year":"2023","journal-title":"bioRxiv"}],"container-title":["PLOS ONE"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0293691","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,5,16]],"date-time":"2024-05-16T13:32:07Z","timestamp":1715866327000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0293691"}},"subtitle":[],"editor":[{"given":"Ryan T.","family":"Roemmich","sequence":"first","affiliation":[],"role":[{"role":"editor","vocabulary":"crossref"}]}],"short-title":[],"issued":{"date-parts":[[2024,5,16]]},"references-count":57,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2024,5,16]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0293691","relation":{"has-preprint":[{"id-type":"doi","id":"10.1101\/2023.10.18.562999","asserted-by":"object"}]},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,5,16]]}}}