Original researchIncreased physiologic intensity during walking and running on a non-motorized, curved treadmill
Introduction
Treadmills are a key piece of training equipment utilized by a diversity of populations, ranging from disabled patients undergoing rehabilitation to elite athletes aiming to maximize sports performance. Non-motorized treadmills allow users to naturally self-select speed and have demonstrated utility in fitness assessment (Janaudis-Ferreira, Sundelin, & Wadell, 2010), simulation of competitive sports (Sirotic & Coutts, 2008), and strength and conditioning (Highton, Lamb, Twist, & Nicholas, 2012). One recent innovation in non-motorized treadmill design has been a modified treadmill deck with a concave curved surface (Curve and Curve XL, Woodway USA Inc., Waukesha, WI). The non-motorized, curved treadmill (NMCT) is designed such that the user controls the treadmill belt speed dynamically, by changing where on the curved surface the user chooses to walk or run. The curved design introduces a slight incline to the front aspect of the treadmill creating not only the feeling of having to run uphill but also the need for greater speed to maintain the exact location on the treadmill. In theory, having to manually propel the treadmill belt especially on an incline creates a greater metabolic expenditure.
According to the treadmill manufacturer, exercise performed on NMCT can result in as much as a 30% increase in caloric expenditure compared to a standard motorized treadmill (SMT). This greater energy expenditure is important to quantify as an evidence-based practitioner looking to condition athletes as part of a comprehensive return to sport intervention. While the manufacturer provides two research abstracts on its website indicating greater physiologic intensity on NMCT compared to SMT (Snyder et al., 2010a, Snyder et al., 2010b), such claims are not accompanied by supporting peer-reviewed, published research. Previous research has evaluated NMCT for anaerobic performance (Gonzalez et al., 2013) and sprinting (Mangine et al., 2014). However, only one known peer-reviewed publication has investigated the use of such a treadmill for aerobic fitness, which reported a greater heart rate when the Rockport walk test was performed on NMCT compared to overground walking (Seneli, Ebersole, O'Connor, & Snyder, 2013). Additionally, this test, as performed on the NMCT, underestimated maximal oxygen consumption (Seneli et al., 2013) which suggests this unique treadmill design does elicit physiologic differences, but the extent of these differences is currently not known.
Given the potential for NMCT to increase metabolic demand during exercise, we aimed to compare cardiometabolic responses and rating of perceived exertion (RPE) of healthy subjects between NMCT and SMT during walking and running. We hypothesized that at a matched speed, subjects exercising on NMCT would experience greater metabolic demand compared to SMT for both walking and running.
Section snippets
Subjects
A heterogeneous group of healthy recreationally active (e.g. general fitness participants) and competitive (e.g. lacrosse players, cyclists, track and field athletes) individuals, ages 18 through 50 years, were recruited from the university community to participate in this study. Ten participants (5 male and 5 female) were enrolled in this study and all completed the study (Age = 28.1 ± 9.8 y; Height = 1.77 ± 0.13 m; Mass = 70.3 ± 12.4 kg; BMI = 22.3 ± 2.3 kg m−2). All subjects underwent
Results
A summary of all relevant variables is presented in Table 1. Measured treadmill speed on NMCT was 1.39 ± 0.03 m s−1 during walking and 2.26 ± 0.04 m s−1 during running.
Discussion
The key finding of this study is that walking and running on NMCT elicits a greater physiologic stimulus than that on SMT at comparable speeds. Walking at 1.34 m s−1 on an SMT is categorized as “moderate intensity” activity (American College of Sports Medicine, 2013). The results of this study reveal that, for many individuals, walking on NMCT at 1.34 m s−1 is > 6 METs, which is classified as “vigorous intensity” activity (American College of Sports Medicine, 2013). While RPE was statistically
Conclusion
In summary, walking and running on NMCT does consistently increase physiologic intensity, and thus metabolic rate, substantially above that achieved on SMT. These increases are likely partially related to the incline at which the user must run to move the treadmill belt. Although RPE was significantly greater on NMCT than SMT, the magnitude of these differences was relatively small, especially in light of the large differences in measured physiologic intensity. These findings suggest exercising
Conflict of interest
None declared.
Ethics approval
All procedures in this study were approved by the university's Institutional Review Board and all participants underwent written informed consent.
Funding
None declared.
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