{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T23:15:28Z","timestamp":1790810128032,"version":"4.1.0"},"reference-count":78,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2017,11,1]]},"abstract":"<jats:p>The metabolic energy that human walking requires can vary by more than 10-fold, depending on the speed, surface gradient, and load carried. Although the mechanical factors determining economy are generally considered to be numerous and complex, we tested a minimum mechanics hypothesis that only three variables are needed for broad, accurate prediction: speed, surface grade, and total gravitational load. We first measured steady-state rates of oxygen uptake in 20 healthy adult subjects during unloaded treadmill trials from 0.4 to 1.6 m\/s on six gradients: \u22126, \u22123, 0, 3, 6, and 9\u00b0. Next, we tested a second set of 20 subjects under three torso-loading conditions (no-load, +18, and +31% body weight) at speeds from 0.6 to 1.4 m\/s on the same six gradients. Metabolic rates spanned a 14-fold range from supine rest to the greatest single-trial walking mean (3.1\u2009\u00b1\u20090.1 to 43.3\u2009\u00b1\u20090.5 ml O<jats:sub>2<\/jats:sub>\u00b7kg<jats:sub>-body<\/jats:sub><jats:sup>\u22121<\/jats:sup>\u00b7min<jats:sup>\u22121<\/jats:sup>, respectively). As theorized, the walking portion (V\u0307o<jats:sub>2-walk<\/jats:sub>\u2009=\u2009 V\u0307o<jats:sub>2-gross<\/jats:sub>\u2013 V\u0307o<jats:sub>2-supine-rest<\/jats:sub>) of the body\u2019s gross metabolic rate increased in direct proportion to load and largely in accordance with support force requirements across both speed and grade. Consequently, a single minimum-mechanics equation was derived from the data of 10 unloaded-condition subjects to predict the pooled mass-specific economy (V\u0307o<jats:sub>2-gross<\/jats:sub>, ml O<jats:sub>2<\/jats:sub>\u00b7kg<jats:sub>-body + load<\/jats:sub><jats:sup>\u22121<\/jats:sup>\u00b7min<jats:sup>\u22121<\/jats:sup>) of all the remaining loaded and unloaded trials combined ( n = 1,412 trials from 90 speed\/grade\/load conditions). The accuracy of prediction achieved ( r<jats:sup>2<\/jats:sup>\u2009=\u20090.99, SEE\u2009=\u20091.06 ml O<jats:sub>2<\/jats:sub>\u00b7kg<jats:sup>\u22121<\/jats:sup>\u00b7min<jats:sup>\u22121<\/jats:sup>) leads us to conclude that human walking economy is predictably determined by the minimum mechanical requirements present across a broad range of conditions.<\/jats:p><jats:p>NEW &amp; NOTEWORTHY Introduced is a \u201cminimum mechanics\u201d model that predicts human walking economy across a broad range of conditions from only three variables: speed, surface grade, and body-plus-load mass. The derivation\/validation data set includes steady-state loaded and unloaded walking trials ( n = 3,414) that span a fourfold range of walking speeds on each of six different surface gradients (\u22126 to +9\u00b0). The accuracy of our minimum mechanics model ( r<jats:sup>2<\/jats:sup>\u2009=\u20090.99; SEE\u2009=\u20091.06 ml O<jats:sub>2<\/jats:sub>\u00b7kg<jats:sup>\u22121<\/jats:sup>\u00b7min<jats:sup>\u22121<\/jats:sup>) appreciably exceeds that of currently used standards.<\/jats:p>","DOI":"10.1152\/japplphysiol.00504.2017","type":"journal-article","created":{"date-parts":[[2017,7,21]],"date-time":"2017-07-21T01:10:23Z","timestamp":1500599423000},"page":"1288-1302","source":"Crossref","is-referenced-by-count":44,"title":["Walking economy is predictably determined by speed, grade, and gravitational load"],"prefix":"10.1152","volume":"123","author":[{"given":"Lindsay W.","family":"Ludlow","sequence":"first","affiliation":[{"name":"Locomotor Performance Laboratory, Department of Applied Physiology and Wellness, Southern Methodist University, Dallas, Texas"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter 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