{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T08:11:42Z","timestamp":1771488702930,"version":"3.50.1"},"reference-count":48,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,4,23]],"date-time":"2021-04-23T00:00:00Z","timestamp":1619136000000},"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>Quantitative and qualitative running gait analysis allows the early identification and the longitudinal monitoring of gait abnormalities linked to running-related injuries. A promising calibration- and marker-less video sensor-based technology (i.e., Graal), recently validated for walking gait, may also offer a time- and cost-efficient alternative to the gold-standard methods for running. This study aim was to ascertain the validity of an improved version of Graal for quantitative and qualitative analysis of running. In 33 healthy recreational runners (mean age 41 years), treadmill running at self-selected submaximal speed was simultaneously evaluated by a validated photosensor system (i.e., Optogait\u2014the reference methodology) and by the video analysis of a posterior 30-fps video of the runner through the optimized version of Graal. Graal is video analysis software that provides a spectral analysis of the brightness over time for each pixel of the video, in order to identify its frequency contents. The two main frequencies of variation of the pixel\u2019s brightness (i.e., F1 and F2) correspond to the two most important frequencies of gait (i.e., stride frequency and cadence). The Optogait system recorded step length, cadence, and its variability (vCAD, a traditional index of gait quality). Graal provided a direct measurement of F2 (reflecting cadence), an indirect measure of step length, and two indexes of global gait quality (harmony and synchrony index). The correspondence between quantitative indexes (Cadence vs. F2 and step length vs. Graal step length) was tested via paired t-test, correlations, and Bland\u2013Altman plots. The relationship between qualitative indexes (vCAD vs. Harmony and Synchrony Index) was investigated by correlation analysis. Cadence and step length were, respectively, not significantly different from and highly correlated with F2 (1.41 Hz \u00b1 0.09 Hz vs. 1.42 Hz \u00b1 0.08 Hz, p = 0.25, r2 = 0.81) and Graal step length (104.70 cm \u00b1 013.27 cm vs. 107.56 cm \u00b1 13.67 cm, p = 0.55, r2 = 0.98). Bland\u2013Altman tests confirmed a non-significant bias and small imprecision between methods for both parameters. The vCAD was 1.84% \u00b1 0.66%, and it was significantly correlated with neither the Harmony nor the Synchrony Index (0.21 \u00b1 0.03, p = 0.92, r2 = 0.00038; 0.21 \u00b1 0.96, p = 0.87, r2 = 0.00122). These findings confirm the validity of the optimized version of Graal for the measurement of quantitative indexes of gait. Hence, Graal constitutes an extremely time- and cost-efficient tool suitable for quantitative analysis of running. However, its validity for qualitative running gait analysis remains inconclusive and will require further evaluation in a wider range of absolute and relative running intensities in different individuals.<\/jats:p>","DOI":"10.3390\/s21092977","type":"journal-article","created":{"date-parts":[[2021,4,25]],"date-time":"2021-04-25T02:12:57Z","timestamp":1619316777000},"page":"2977","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Quantitative and Qualitative Running Gait Analysis through an Innovative Video-Based Approach"],"prefix":"10.3390","volume":"21","author":[{"given":"Laura","family":"Simoni","sequence":"first","affiliation":[{"name":"Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37129 Verona, Italy"},{"name":"IRCCS Fondazione Don Carlo Gnocchi ONLUS, 50143 Florence, Italy"}]},{"given":"Alessandra","family":"Scarton","sequence":"additional","affiliation":[{"name":"Microgate SRL, 39100 Bolzano, Italy"}]},{"given":"Claudio","family":"Macchi","sequence":"additional","affiliation":[{"name":"IRCCS Fondazione Don Carlo Gnocchi ONLUS, 50143 Florence, Italy"}]},{"given":"Federico","family":"Gori","sequence":"additional","affiliation":[{"name":"Microgate SRL, 39100 Bolzano, Italy"}]},{"given":"Guido","family":"Pasquini","sequence":"additional","affiliation":[{"name":"IRCCS Fondazione Don Carlo Gnocchi ONLUS, 50143 Florence, Italy"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4394-8550","authenticated-orcid":false,"given":"Silvia","family":"Pogliaghi","sequence":"additional","affiliation":[{"name":"Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, 37129 Verona, Italy"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1186\/1743-0003-11-162","article-title":"Contributions of lower extremity kinematics to trunk accelerations during moderate treadmill running","volume":"11","author":"Lindsay","year":"2014","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1177\/0363546509347985","article-title":"Predictors of Running-Related Injuries in Novice Runners Enrolled in a Systematic Training Program A Prospective Cohort Study","volume":"38","author":"Buist","year":"2010","journal-title":"Am. J. Sports Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1017","DOI":"10.1007\/s40279-015-0333-8","article-title":"Incidence of Running-Related Injuries Per 1000 h of running in Different Types of Runners: A Systematic Review and Meta-Analysis","volume":"45","author":"Bueno","year":"2015","journal-title":"Sports Med."},{"key":"ref_4","first-page":"469","article-title":"Incidence and determinants of lower extremity running injuries in long distance runners: A systematic review","volume":"41","author":"Siem","year":"2007","journal-title":"Sport En Geneeskunde"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"651","DOI":"10.1016\/j.pmr.2005.02.002","article-title":"Etiology, prevention, and early intervention of overuse injuries in runners: A biomechanical perspective","volume":"16","author":"Hreljac","year":"2005","journal-title":"Phys. Med. Rehabil. Clin. N. Am."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"828","DOI":"10.1016\/j.jbiomech.2012.12.008","article-title":"Harmonic Ratios: A quantification of step to step symmetry","volume":"46","author":"Bellanca","year":"2013","journal-title":"J. Biomech."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"222","DOI":"10.1016\/j.gaitpost.2016.11.004","article-title":"Variability of segment coordination using a vector coding technique: Reliability analysis for treadmill walking and running","volume":"51","author":"Hafer","year":"2017","journal-title":"Gait Posture"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1016\/j.gaitpost.2019.12.018","article-title":"Does fatigue alter step characteristics and stiffness during running?","volume":"76","year":"2020","journal-title":"Gait Posture"},{"key":"ref_9","first-page":"1","article-title":"Coordinative variability and overuse injury","volume":"4","author":"Joseph","year":"2012","journal-title":"Sports Med. Arthrosc. Rehabil. Ther. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/j.gaitpost.2009.12.003","article-title":"Variability and fluctuation in running gait cycle of trained runners and non-runners","volume":"31","author":"Yosuke","year":"2010","journal-title":"Gait Posture"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"832","DOI":"10.1249\/01.MSS.0000126779.65353.CB","article-title":"The effects of knee contact angle on impact forces and accelerations","volume":"36","author":"Derrick","year":"2004","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1016\/j.gaitpost.2010.09.020","article-title":"Running injury and stride time variability over a prolonged run","volume":"33","author":"Meardon","year":"2011","journal-title":"Gait Posture"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1016\/j.pmr.2015.08.006","article-title":"An evidence-based videotaped running biomechanics analysis","volume":"27","author":"Souza","year":"2016","journal-title":"Phys. Med. Rehabil. Clin."},{"key":"ref_14","first-page":"25","article-title":"Aerial and terrestrial patterns: A novel approach to analyzing human running","volume":"37","author":"Gindre","year":"2016","journal-title":"Int. J. Sports Med."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Zhang, A., Yang, S., Zhang, X., Zhang, J., and Zhang, W. (2017, January 13\u201315). Abnormal Gait Detection in Surveillance Videos with FFT-Based Analysis on Walking Rhythm. Proceedings of the International Conference on Image and Graphics, Shanghai, China.","DOI":"10.1007\/978-3-319-71607-7_10"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/j.gaitpost.2011.03.027","article-title":"Efficacy of clinical gait analysis: A systematic review","volume":"34","author":"Wren","year":"2011","journal-title":"Gait Posture"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"347","DOI":"10.1016\/j.csm.2010.03.013","article-title":"Kinematics and kinetics of gait: From lab to clinic","volume":"29","author":"Dicharry","year":"2010","journal-title":"Clin. Sports Med."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1575","DOI":"10.3109\/02699052.2010.523053","article-title":"Temporospatial characteristics of gait in patients with lower limb muscle hypertonia after traumatic brain injury","volume":"24","author":"Chow","year":"2010","journal-title":"Brain Inj."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3362","DOI":"10.3390\/s140203362","article-title":"Gait analysis methods: An overview of wearable and non-wearable systems, highlighting clinical applications","volume":"14","author":"Alvaro","year":"2014","journal-title":"Sensors"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"409","DOI":"10.1177\/1941738119844795","article-title":"Validity and reliability of 2-dimensional video-based assessment to analyze foot strike pattern and step rate during running: A systematic review","volume":"11","author":"Fredette","year":"2019","journal-title":"Sports Health"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"19498","DOI":"10.2196\/19498","article-title":"Agreement Between Spatiotemporal Gait Parameters Measured by a Markerless Motion Capture System and Two Reference Systems\u2014A Treadmill-Based Photoelectric Cell and High-Speed Video Analyses: Comparative Study","volume":"8","author":"Hermoso","year":"2020","journal-title":"JMIR mHealth uHealth"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"556","DOI":"10.2519\/jospt.2016.6280","article-title":"Reliability of a qualitative video analysis for running","volume":"46","author":"Pipkin","year":"2016","journal-title":"J. Orthop. Sports Phys. Ther."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"961","DOI":"10.1016\/j.nmd.2019.11.003","article-title":"GNE myopathy\u2014A cross-sectional study on spatio-temporal gait characteristics","volume":"29","author":"Gomez","year":"2019","journal-title":"Neuromuscul. Disord."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"265","DOI":"10.23736\/S1973-9087.18.05306-6","article-title":"Inertial sensors versus standard systems in gait analysis: A systematic review and meta-analysis","volume":"55","author":"Petraglia","year":"2019","journal-title":"Eur. J. Phys. Rehabil. Med."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1186\/s40798-018-0139-y","article-title":"A review of the evolution of vision-based motion analysis and the integration of advanced computer vision methods towards developing a markerless system","volume":"4","author":"Colyer","year":"2018","journal-title":"Sports Med. Open"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1016\/j.jbiomech.2019.06.017","article-title":"Agreement between spatiotemporal parameters from a photoelectric system with different filter settings and high-speed video analysis during running on a treadmill at comfortable velocity","volume":"93","year":"2019","journal-title":"J. Biomech."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1002\/mds.22352","article-title":"Walking stability using harmonic ratios in Parkinson\u2019s disease","volume":"24","author":"Lowry","year":"2009","journal-title":"Mov. Disord. Off. J. Mov. Disord. Soc."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1007\/s40846-016-0178-0","article-title":"Stability and harmony of gait in patients with subacute stroke","volume":"36","author":"Iosa","year":"2016","journal-title":"J. Med. Biol. Eng."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1844","DOI":"10.1177\/0363546506288753","article-title":"Knee angular impulse as a predictor of patellofemoral pain in runners","volume":"34","author":"Stefanyshyn","year":"2006","journal-title":"Am. J. Sports Med."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1055\/s-0033-1336016","article-title":"Ability and stability of running and walking in children with cerebral palsy","volume":"44","author":"Iosa","year":"2013","journal-title":"Neuropediatrics"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1016\/j.gaitpost.2016.11.005","article-title":"Asymmetry between lower limbs during rested and fatigued state running gait in healthy individuals","volume":"51","author":"Radzak","year":"2017","journal-title":"Gait Posture"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1768","DOI":"10.1080\/02640414.2017.1416974","article-title":"Coordination in gait: Demonstration of a spectral approach","volume":"36","author":"Williams","year":"2018","journal-title":"J. Sports Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"262","DOI":"10.3389\/fpsyg.2016.00262","article-title":"Uniqueness of human running coordination: The integration of modern and ancient evolutionary innovations","volume":"7","author":"Kiely","year":"2016","journal-title":"Front. Psychol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/j.jsams.2012.08.002","article-title":"Differences in kinetic variables between injured and noninjured novice runners: A prospective cohort study","volume":"16","author":"Bredeweg","year":"2013","journal-title":"J. Sci. Med. Sport"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Simoni, L., Scarton, A., Gerli, F., Macchi, C., Gori, F., Pasquini, G., and Pogliaghi, S. (2020). Testing the Performance of an Innovative Markerless Technique for Quantitative and Qualitative Gait Analysis. Sensors, 20.","DOI":"10.3390\/s20226654"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2321","DOI":"10.1080\/02640414.2020.1782567","article-title":"Time-course of running treadmill adaptation in novice treadmill runners","volume":"38","author":"Simoni","year":"2020","journal-title":"J. Sports Sci."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Simoni, L., Pancani, S., Vannetti, F., Macchi, C., and Pasquini, G. (2020). Relationship between Lower Limb Kinematics and Upper Trunk Acceleration in Recreational Runners. J. Healthc. Eng.","DOI":"10.1155\/2020\/8973010"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"475","DOI":"10.4085\/1062-6050-44.5.475","article-title":"Jogging kinematics after lumbar paraspinal muscle fatigue","volume":"44","author":"Hart","year":"2009","journal-title":"J. Athl. Train."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"766","DOI":"10.1080\/02640414.2017.1340657","article-title":"Acute kinematics changes in marathon runners using different footwear","volume":"36","author":"Soares","year":"2018","journal-title":"J. Sports Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1589\/jpts.26.81","article-title":"Concurrent validity and test-retest reliability of the OPTOGait photoelectric cell system for the assessment of spatio-temporal parameters of the gait of young adults","volume":"26","author":"Lee","year":"2014","journal-title":"J. Phys. Ther. Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"02NT02","DOI":"10.1088\/1361-6579\/aaa74d","article-title":"Prediction of sustained harmonic walking in the free-living environment using raw accelerometry data","volume":"39","author":"Urbanek","year":"2018","journal-title":"Physiol. Meas."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1186\/1743-0003-11-131","article-title":"Measures of gait stability: Performance on adults and toddlers at the beginning of independent walking","volume":"11","author":"Bisi","year":"2014","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_43","unstructured":"Sergey, B., Bourov, P., and Ilinih, D. (2007). Brightness calculation in digital image processing. International Symposium on Technologies for Digital Photo Fulfillment, Society for Imaging Science and Technology."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Winter, D.A. (2009). Biomechanics and Motor Control of Human Movement, John Wiley & Sons.","DOI":"10.1002\/9780470549148"},{"key":"ref_45","first-page":"1067","article-title":"Is the relationship between stride length, frequency, and velocity influenced by running on a treadmill or overground?","volume":"10","author":"Bailey","year":"2017","journal-title":"Int. J. Exerc. Sci."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1080\/00140136608964399","article-title":"The relationships between length of stride, step frequency, time of swing and speed of walking for children and adults","volume":"9","author":"Grieve","year":"1966","journal-title":"Ergonomics"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"136","DOI":"10.1016\/j.ptsp.2020.12.023","article-title":"Low back pain among Italian runners: A cross-sectional survey","volume":"48","author":"Maselli","year":"2021","journal-title":"Phys. Ther. Sport"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.humov.2008.10.001","article-title":"Steady and transient coordination structures of walking and running","volume":"28","author":"Lamoth","year":"2009","journal-title":"Hum. Mov. Sci."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/9\/2977\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:52:09Z","timestamp":1760161929000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/9\/2977"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,23]]},"references-count":48,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2021,5]]}},"alternative-id":["s21092977"],"URL":"https:\/\/doi.org\/10.3390\/s21092977","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,23]]}}}