The Efect of Motorized vs Non-Motorized Treadmills on Exercise Economy during Acute Sub-maximal Bouts in Collegiate Cross-Country Female Athletes Nicole C. Dabbs*, Miranda J. Reid, Jasmine Wimbish, Jason Ng Department of Kinesiology, California State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407 Corresponding Author: Nicole C. Dabbs, E-mail: ndabbs@csusb.edu ABSTRACT Background: Fitness equipment manufacturers have developed non-motorized treadmills (NMT) to better replicate overground running, a characteristic which motorized treadmills (MT) purportedly lack. Because NMTs are novel, limited empirical evidence exists regarding acute physiological and neuromuscular activity responses to its use. Objectives: The purpose of this investigation was to examine the efect of walking and running on an NMT and MT on exercise economy (EE), cardiometabolic responses, lower-body muscle activity, and rating of perceived exertion (RPE) in division II female cross-country athletes. Methods: Thirteen female cross- country athletes volunteered to complete a treadmill protocol that consisted of a warm-up walk, a 5-min walk, a 5-min run, and a 5-min cool-down walk on an NMT and MT on two separate occasions. During both treadmill conditions, VO 2 , RER, neuromuscular activity, HR, and RPE were recorded and analyzed every minute. Results: VO 2 (NMT= 36.8 ± 10.0 ml/kg/min; MT= 27.4 ± 6.7 ml/kg/min), RER (NMT= 1.02 ± 0.14; MT= 0.89 ± 0.08), HR (NMT= 167 ± 18 bpm; MT= 142 ± 21 bpm), and RPE (NMT= 12 ± 2; MT= 9 ± 2) measures were signifcantly (p<0.05 for all) greater on the NMT than the MT in walking and running. Conclusions: The greater VO 2 , RER, and HR experienced on the NMT indicates higher physical exertion, and the greater RPE on the NMT indicates the participants’ perception of exertion correspond to the physiological responses. While cardiometabolic demand was greater on the NMT, thereby suggesting exercise economy was greater with the MT. Key words: Aerobic, Running, Electromyography, Oxygen Uptake, Walking INTRODUCTION Practitioners have available to them a variety of training modes and protocols to enhance their clients’ health or ath- letes’ performance. Exercise on treadmills ofers a consistent, accessible, and reliable form of aerobic training commonly used when outdoor areas are not accessible due to inclem- ent weather or limited space availability. Fitness equip- ment manufacturers have introduced curved non-motorized treadmills (NMT) in general ftness, laboratory, and athlet- ic settings. Compared to running on a motorized treadmill (MT), which allows an individual to run on a belt at diferent speeds determined by an external motor, NMTs have been shown to better mimic overground locomotion, allowing in- dividuals to voluntarily manipulate speed, gait, and pace (De Witt, Lee, Wilson, & Hagan, 2009; Fullenkamp, Matthew Laurent, & Campbell, 2015; Stevens et al., 2015). Recent in- vestigations have examined NMT exercise on anaerobic per- formance (Gonzalez et al., 2013; Highton, Lamb, Twist, & Nicholas, 2012; Mangine et al., 2014), maximal oxygen up- take (VO 2max ) (Bacon, Carter, Ogle, & Joyner, 2013; Morgan, Laurent, & Fullenkamp, 2016), cardiometabolic demand (Edwards, Tofari, Cormack, & Whyte, 2017; Li, Xue, Hong, Published by Australian International Academic Centre PTY.LTD. Copyright (c) the author(s). This is an open access article under CC BY license (https://creativecommons.org/licenses/by/4.0/) http://dx.doi.org/10.7575/aiac.ijkss.v.9n.2p.1 Song, & He, 2020; Schoenmakers, Crisell, & Reed, 2020), and muscular strength (Franks, Brown, Coburn, Kersey, & Bottaro, 2012). However, there is minimal research that un- derstands exercise economy (EE) and neuromuscular activi- ty while using an NMT. During running, the human body experiences sever- al physiological changes, including an increase in cardiac output and ventilation. This subsequently increases blood volume delivery throughout the body, increasing oxygen availability to the exercising skeletal muscle, thereby al- lowing an increase in oxygen uptake (VO 2 ). The capacity to convert oxygen to work is known as EE, which is normally expressed as pulmonary oxygen uptake for the mechanical work completed (Gaesser & Brooks, 1975). An increase in EE translates to greater oxidative phosphorylation of adenos- ine triphosphate (ATP) to fuel the muscle force generation required for a given external workload (Burton, Stokes, & Hall, 2004). Additionally, during a sustained exercise inten- sity, the body reaches a steady state; a concept implying that cardiovascular and respiratory gas responses are sufcient to meet the metabolic demand of the exercise stress (Ferret- ti, Fagoni, Taboni, Bruseghini, & Vinetti, 2017) leading to International Journal of Kinesiology & Sports Science ISSN: 2202-946X www.ijkss.aiac.org.au ARTICLE INFO Article history Received: January 11, 2021 Accepted: March 01, 2021 Published: April 30, 2021 Volume: 9 Issue: 2 Conficts of interest: None. Funding: None.