Inertial measurement units (IMU) provide a convenient tool for gait stability assessment. However, it is unclear how various gait characteristics relate to each other and whether gait characteristics can be obtained from resultant acceleration. Therefore, step duration variability was measured in treadmill walking from 39 young ambulant volunteers (age 24.2 [± 2.5] y; height 1.79 [± 0.09] m; mass 71.6 [± 12.0] kg) using motion capture. Accelerations and gyrations were simultaneously recorded with an IMU. Harmonic ratio, maximum Lyapunov exponents, and multiscale sample entropy (MSE) were calculated. Step duration variability was positively associated with MSE with coarseness levels = 3–6 (r = –.33 to –.42, P ≤ .045). Harmonic ratio and MSE with all coarseness levels were negatively associated (r = –.45 to –.57, P ≤ .004). The MSE with coarseness level = 2 was negatively associated with short-term maximum Lyapunov exponents (r = –.32, P = .047). The agreement between resultant and vertical acceleration derived gait characteristics was excellent (ICC = 0.97–0.99). In conclusion, MSE with varying coarseness levels was associated with the other gait characteristics evaluated in the study. Resultant and vertical acceleration derived results had excellent agreement, which suggests that resultant acceleration is a viable alternative to considering the acceleration dimensions independently.
Timo Rantalainen, Nicolas H. Hart, Sophia Nimphius and Daniel W. Wundersitz
Gisela Kobberling, Louis W. Jankowski and Luc Leger
The oxygen consumption (VO2) of 30 (10 females, 20 males) legally blind adolescents and their sighted controls were compared for treadmill walking (3 mph, 4.8 km/h) and running (6 mph, 9.6 km/h). The VO2 of the visually impaired subjects averaged 24.4% and 10.8% higher than those of their same-sex age-matched controls, and 42.8% and 11.2% higher than the American College of Sports Medicine (ACSM) norms for walking (p<.01) and running (p<.05), respectively. The normal association between aerobic capacity and locomotor energy costs was evident among the sighted controls (r= .44, p<.05) but insignificant (r=.35, p>.05) for the visually impaired subjects. The energy costs of both walking and running were highest among the totally blind subjects, and decreased toward normal as a function of residual vision among the legally blind subjects. The energy costs of walking and running for blind adolescents are higher than both those of sighted controls and the ACSM norm values.
Cynthia M. Ferrara, Susan H. McCrone, David Brendle, Alice S. Ryan and Andrew P. Goldberg
The metabolic changes associated with the addition of 4 months of resistive exercise to an existing aerobic exercise program (AEX+RT, n = 7) were compared to a maintenance aerobic exercise program (AEX, n = 8) in overweight, older men. The subjects in this study had recently completed a 6-month aerobic exercise program (treadmill walking, 45 min/d, 2 d/wk). The AEX+RT group added 6 exercises on upper- and lower-body pneumatic-resistance machines (2 sets, 15 repetitions each, 2 d/wk) to an aerobic exercise program at ≥ 70% heart rate reserve for 30–40 min, 2 d/wk on treadmill, while the AEX group continued the same maintenance treadmill AEX program. There were no baseline differences in body weight, VO2max, or glucose metabolism between groups. The AEX+RT group increased upper- and lower-extremity strength by 28 ± 4% and 46 ± 6%, respectively (p < .05), despite a 9% decrease in VO2max (p < .05). VO2max did not change in the AEX group. There was no change in the fasting glucose or insulin levels, or the 3-h glucose responses to an oral glucose load in either group. The insulin responses decreased by 25 ± 4% in the AEX+RT group (p < .01) but did not change in the AEX group. In conclusion, the addition of resistive exercise training to an existing aerobic exercise program may improve insulin sensitivity in overweight, older men, and thus prevent the development of type 2 diabetes.
Ann F. Maliszewski, Patty S. Freedson, Chris J. Ebbeling, Jill Crussemeyer and Kari B. Kastango
The Caltrac accelerometer functions as either an activity monitor that provides activity counts based on vertical acceleration as the individual moves about, or as a calorie counter in which the acceleration units are used in conjunction with body size, age, and sex to estimate energy expenditure. This study compared VO2 based energy expenditure with Caltrac estimated energy expenditure during three speeds of treadmill walking in children and adults. It also tested the validity of the Caltrac to differentiate between high and low levels of walking activity (activity counts). Ten boys and 10 men completed three randomly assigned walks while oxygen consumption was monitored and Caltrac estimates were obtained. The results indicate that the Caltrac does not accurately predict energy expenditure for boys and men across the three speeds of walking. Although there were no significant differences between actual and predicted energy expenditure values, the standard errors of estimate were high (17-25%) and the only significant correlation was found for men at the fastest walking speed (r=.81). However, the 95% confidence intervals of the activity counts and energy expenditure estimates from the Caltrac support its use as an activity monitor during walking.
Dinesh John, David Bassett, Dixie Thompson, Jeffrey Fairbrother and Debora Baldwin
Although using a treadmill workstation may change the sedentary nature of desk jobs, it is unknown if walking while working affects performance on office-work related tasks.
To assess differences between seated and walking conditions on motor skills and cognitive function tests.
Eleven males (24.6 ± 3.5 y) and 9 females (27.0 ± 3.9 y) completed a test battery to assess selective attention and processing speed, typing speed, mouse clicking/drag-and-drop speed, and GRE math and reading comprehension. Testing was performed under seated and walking conditions on 2 separate days using a counterbalanced, within subjects design. Participants did not have an acclimation period before the walking condition.
Paired t tests (P < .05) revealed that in the seated condition, completion times were shorter for mouse clicking (26.6 ± 3.0 vs. 28.2 ± 2.5s) and drag-and-drop (40.3 ± 4.2 vs. 43.9 ± 2.5s) tests, typing speed was greater (40.2 ± 9.1 vs. 36.9 ± 10.2 adjusted words · min−1), and math scores were better (71.4 ± 15.2 vs. 64.3 ± 13.4%). There were no significant differences between conditions in selective attention and processing speed or in reading comprehension.
Compared with the seated condition, treadmill walking caused a 6% to 11% decrease in measures of fine motor skills and math problem solving, but did not affect selective attention and processing speed or reading comprehension.
Ya-Ting Yang, Yasuyuki Yoshida, Tibor Hortobágyi and Shuji Suzuki
We determined the angular range of motion and the relative timing of displacement in the thorax, lumbar spine, and pelvis in the transverse plane during treadmill walking at three velocities. Nine healthy young females walked on a treadmill for three minutes at 0.40, 0.93, and 1.47 m/s. The position of seven reflective markers and three rigs placed on the thorax, lumbar spine, and pelvis were recorded at 200 Hz by an eight-camera motion capture system. As gait velocity increased, stride length increased, cycle time decreased, and angular displacement in the thorax and L1 decreased but increased at the pelvis and L5 (all P < .05). The time of maximal angular rotation occurred in the following sequence: pelvis, L5, L3, L1, and thorax (P < .001). The thorax and L1 and L3 were in-phase for shorter duration as gait velocity increased, and this reduction was especially large, approx. 32% (P < .05), between thorax and pelvis. As gait velocity increased, the pelvis rotated earlier, causing the shortening of in-phase duration between thorax and pelvis. These data suggest that, as gait velocity increases, pelvis rotation dictates trunk rotation in the transverse plane during gait in healthy young females.
Yuri Feito, David R. Bassett, Dixie L. Thompson and Brian M. Tyo
Activity monitors are widely used in research, and are currently being used to study physical activity (PA) trends in the US and Canada. The purpose of this study was to determine if body mass index (BMI) affects the step count accuracy of commonly used accelerometer-based activity monitors during treadmill walking.
Participants were classified into BMI categories and instructed to walk on a treadmill at 3 different speeds (40, 67, and 94 m·min−1) while wearing 4 accelerometer-based activity monitors (ActiGraph GT1M, ActiCal, NL-2000, and StepWatch).
There was no significant main effect of BMI on pedometer accuracy. At the slowest speed, all waist-mounted devices significantly underestimated actual steps (P < .001), with the NL-2000 recording the greatest percentage (72%). At the intermediate speed, the ActiGraph was the least accurate, recording only 80% of actual steps. At the fastest speed, all of the activity monitors demonstrated a high level of accuracy.
Our data suggest that BMI does not greatly affect the step-counting accuracy of accelerometer-based activity monitors. However, the accuracy of the ActiGraph, ActiCal, and NL-2000 decreases at slower speeds. The ankle-mounted StepWatch was the most accurate device across a wide range of walking speeds.
Randall J. Bergman, Justin W. Spellman, Michael E. Hall and Shawn M. Bergman
This study examined the validity of a selected free pedometer application (iPedometer; IP) for the iPhone that could be used to assess physical activity.
Twenty college students (10 men, 10 women; mean age: 21.85 ± 1.57 yrs) wore an iPhone at 3 locations (pocket, waist, arm) and a StepWatch 3 Step Activity Monitor (SW) on their right ankle while walking on a treadmill at 5 different speeds (54, 67, 80, 94, 107 m·min−1). A research assistant counted steps with a tally counter (TC).
Statistical significance between the TC, SW, and IP was found during every condition except IP in the pocket at 107 m·min−1 (F 2,38 = .64, P = .54). Correlations involving the IP revealed only 1 positive correlation (IP on arm at 54 m·min−1) for any of the conditions (r = .46, P = .05).
The IP application was not accurate in counting steps and recorded significantly lower step counts than the SW and TC. Thus, the free pedometer application used is not a valid instrument for monitoring activity during treadmill walking.
James J. McClain, Teresa L. Hart, Renee S. Getz and Catrine Tudor-Locke
This study evaluated the utility of several lower cost physical activity (PA) assessment instruments for detecting PA volume (steps) and intensity (time in MVPA or activity time) using convergent methods of assessment.
Participants included 26 adults (9 male) age 27.3 ± 7.1 years with a BMI of 23.8 ± 2.8 kg/m2. Instruments evaluated included the Omron HJ-151 (OM), New Lifestyles NL-1000 (NL), Walk4Life W4L Pro (W4L), and ActiGraph GT1M (AG). Participants wore all instruments during a laboratory phase, consisting of 10 single minute treadmill walking bouts ranging in speed from 40 to 112 m/min, and immediate following the laboratory phase and during the remainder of their free-living day (11.3 ± 1.5 hours). Previously validated AG MVPA cutpoints were used for comparison with OM, NL, and W4L MVPA or activity time outputs during the laboratory and free-living phase.
OM and NL produced similar MVPA estimates during free-living to commonly used AG walking cutpoints, and W4L activity time estimates were similar to one AG lifestyle cutpoint evaluated.
Current findings indicate that the OM, NL, and W4L, ranging in price from $15 to $49, can provide reasonable estimates of free-living MVPA or activity time in comparison with a range of AG walking and lifestyle cutpoints.
Mark Abel, James Hannon, David Mullineaux and Aaron Beighle
Current recommendations call for adults to be physically active at moderate and/or vigorous intensities. Given the popularity of walking and running, the use of step rates may provide a practical and inexpensive means to evaluate ambulatory intensity. Thus, the purpose of this study was to identify step rate thresholds that correspond to various intensity classifications.
Oxygen consumption was measured at rest and during 10 minute treadmill walking and running trials at 6 standardized speeds (54, 80, 107, 134, 161, and 188 m·min-1) in 9 men and 10 women (28.8 ± 6.8 yrs). Two observers counted the participants’ steps at each treadmill speed. Linear and nonlinear regression analyses were used to develop prediction equations to ascertain step rate thresholds at various intensities.
Nonlinear regression analysis of the metabolic cost versus step rates across all treadmill speeds yielded the highest R 2 values for men (R 2 = .91) and women (R 2 = .79). For men, the nonlinear analysis yielded 94 and 125 step·min-1 for moderate and vigorous intensities, respectively. For women, 99 and 135 step·min-1 corresponded with moderate and vigorous intensities, respectively.
Promoting a step rate of 100 step·min-1 may serve as a practical public health recommendation to exercise at moderate intensity.