Differences between Seated and Standing Low-Speed Treadmill Walking

Objective: The purpose of this study was to compare the Energy Expenditure (EE) during very low-speed (< 2.0 mph) treadmill walking while seated to EE during upright treadmill walking. Design: A convenience sample cohort study of nine volunteer participants (4 males; 5 females) M age 63.4 (± 10.5) years performed both seated (MuV) and standing walking (STW), across 0.5 mph, 1.1 and 1.5 mph velocities. Setting: Institutional, University of Oklahoma Human Performance Laboratory in Tulsa. Participants: Elderly adults with no contra-indications for low speed walking, recruited from the University of Oklahoma staff, faculty and a local YMCA. Main outcome measures: Differences between MuV and STW O2 Consumption (VO2), Rating of perceived exertion (RPE10), and heart rate (HR). Results: Mean HR and VO2 differences between MuV (Seated) and STW (standing) walking at very low intensities were small but statistically significant at p < 0.05. Effect sizes were moderate to high (0.61-0.85) for VO2 at 0.5 and 1.1 mph respectively and low to moderate (0.23-0.61) for HR and RPE for 1.1 mph speed. Conclusions: For people unable to stand or walk, the seated treadmill is a suitable alternative to an upright treadmill. Additional studies in larger and more diverse populations are required in order to confirm this studies initial findings to the general population. Clinical relevance: This form of exercise may have value for those seeking very low intensity (subliminal) exercise while seated at a desk or for those individuals who have a low orthopedic tolerance.


Introduction
For many people who are unable to jog or run, walking is a viable substitute for cardio/pulmonary and leg strengthening exercise. Hindrances to walking, however, such as lower extremity weakness, neuromuscular disorders and vision impairment effect many people. Others have vocations that require sitting at a desk or table for most of the workday are at risk for the negative health effects of inactivity [1][2][3]. Prolonged sitting has been associated with an increased risk of cardiovascular events [4][5][6] and may be considered the "New Smoking" [7]. Excessive sitting is positively related to the development of type II diabetes and a major contributor to the high rates of obesity in the general population [8,9]. Some corporate wellness programs permit desk workers and others to work while walking on a low-speed treadmill [5]. Standing desk treadmills are the most popular among participants. However, several drawbacks have limited the wide acceptance of the standing machines including comfort, cost, and size [2,10]. The MuV is a small low speed seated treadmill is designed to fit under a work surface or desk. This study examines the physiological differences between seated treadmill and standing walking across three predetermined walking speeds, 0.5 mph, 1.1 mph and 1.5 mph.

Specific Aims
This pilot study compared very-low speed walking while sitting (MuV) to very-low speed walking while standing (STW). The Energy Expenditure (EE) of nine physically active adults (4 males and 5 females), were stages first followed by standing treadmill walking.

Results
Four males and five females, mean Age 63.4 (± 7.41), BMI 32.1 (± 10.5), performed MuV and STW portions of the graduated walk test. Assumptions for normal distribution and homogeneity of variance (α > 0.05) for VO2, HR, CAD, age and BMI were met. MuV and STW means (± SD) across three walking speeds of 0.5 mph, 1.1 mph and 1.5 mph were calculated for VO2, HR, RPE and Cadence mean values and standard deviations are presented in Table 1.

Methods
A small convenience sample of four physically active males and five physically active females (M = 63.4 (± 10.5) years of age, were recruited from University of Oklahoma Health Sciences Center students, physicians, employees and Tandy YMCA staff and members. This study was approved by, the University of Oklahoma Institutional Review Board. Exclusion criterion included; 1) Any yes response on the Physical Activity Readiness Questionnaire (PAR-Q) [11], or 2) Any cardiac, pulmonary, or musculoskeletal contraindications to exercise. All participants were injury free for the past 3 months, and had some previous experience walking on a motorized treadmill.

Physiological measures
Physiological measures for EE included VO2 (ml/kg -1 / min -1 ), Heart Rate (HR) (beats/min), Cadence (Steps/ minute -1 ) and a subjective Rating of Perceived Exertion (RPE 10 ) for both lungs and legs. Metabolic rates were determined by indirect calorimetry using a computerized metabolic system (Parvo Medics, TrueOne 2400, Sandy, UT, USA). Samples of expired gases were collected during walking while sitting or standing. Collection occurred through a one-way breathing valve and tubing that directed flow first through a pneumotach for measurement of volume flow rates, and then into a mixing chamber. Rates of oxygen uptake (VO2) and were determined from the average value during the minute of each five-minute trial. Standing walking tests were performed on a calibrated motorized treadmill (STW). S seated walking was performed on a calibrated MuV™ mini-treadmill. These measures have shown in the past to be stable and reliable variables to compare energy expenditure specifically for walking or running energy expenditure [12][13][14][15]. This study compared the individual EE differences between seated walking (MuV) and upright walking (STW). Paired T-Test were performed along with an Omnibus ANOVA. The minimum alpha significance level was set at 0.05. In order to conduct a power analysis, Cohen's d-statistic values for small (0.40), moderate (0.60), and large (0.80) effects were calculated [16].

Graded Exercise Test (GXT)
Participants were randomly assigned to one of two groups to control for the ordering effect. After a 2-3minute warm-up/familiarization at a self-selected pace.

RPE and Cadence
There were no statistically significant differences between MuV and STW conditions for Rating of Perceived Exertion (RPE) (p > 0.05) for both lungs and

Conclusion
At very low intensities energy expenditure (HR and VO 2 ) for standing walking was slightly higher than seated walking and were statistically significant (p < 0.05). Effect sizes were moderate to high for VO 2 at 0.5 and 1.1 mph respectively and low to moderate for HR and RPE at 1.1 mph. These findings align with results reported by previous studies. Wang, et al., 2018 explored the difference between resting seated and standing energy expenditure and reported a 16.8% greater mean VO 2 for standing (M = 4.04 ± 0.38 ml/kg -1 /min -1 ) resting energy when compared to resting VO 2 for sitting (M = 4.72 ± 0.42 ml/kg -1 /min -1 ) p < 0.01 [3]. Ludlow, et al. also reported modest differences between with mean VO 2 measures of 3.16 ± 0.08 ml/kg -1 /min -1 and 3.51 ± 0.08 for seated and standing values respectively [17].
For this current study VO 2 , and HR values were statistically higher across 0.5, 1.1 and 1.5 mph walking for both MuV and STW conditions. Higher cadences observed for the MuV condition compared to the standing 1.5 mph walking speeds is most likely due participants adopting a shorter stride pattern in order to accommodate the higher treadmill velocity. Seated treadmill walking (MuV) may have value for those seeking "subliminal exercise" while seated at a desk or for those individuals who have a low orthopedic tolerance or other disabilities preventing them from walking while standing. This current study should guide future, cohort studies in order to determine if MuV walking at very low intensity levels would be a valid surrogate for low-intensity treadmill walking. Additional research should focus on developing appropriate walking speeds for "subliminal exercise" in larger more diverse populations.