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Richard R. Rosenkranz, Sara K. Rosenkranz and Casey Weber

This study sought to assess criterion validity of the Actical monitor step-count function in children via ankle and waist placement, compared with observed video recordings. Children attending a summer program (12 boys, 7 girls, mean age = 9.6yrs, range 7–11yrs) wore two synchronized Acticals, attached at the ankle (AA) and waist (AW). Children performed treadmill walking at varying speeds, and two research assistants counted steps using observed video recordings (OVR). Results showed high correlations for AW-OVR (r = .927, p < .001) and AA-OVR (r = .854, p < .001), but AW and AA were significantly lower than OVR (t > 11.2, p < .001). AW provided better step estimates than AA for step rates above 130 steps per minute. In contrast, AA was superior to AW for slow walking, and measured more steps during the (nontreadmill) program time. Overall, the Actical monitor showed good evidence of validity as a measure of steps in children for population-based studies.

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Kathleen M. Shuleva, Gary R. Hunter, Donna J. Hester and Donna L. Dunaway

This study compared submaximal and maximal oxygen uptake (V̇O2 max) in children ages 3–4 and 5–6 years. Methods appropriate for this age group were developed to elicit maximal performance on the exercise tests. Subjects (N = 22) performed progressive treadmill walking tests. The criteria used to determine whether V̇O2 max was reached were a plateauing of oxygen uptake, HR > 195, and an R > 1.00. The V̇O2 max for the 3- and 4-year-olds (44.5 ml•kg−1•min−1) was not significantly different from that of the 5- and 6-year-olds (44.1 ml•kg−1•min−1). At submaximal levels, 5- and 6-year-olds had significantly lower relative oxygen uptake, indicating better economy in walking. A large proportion of children met testing criteria for V̇O2 max. Test-retest results indicated that the tests were reliable.

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Meaghan Nolan, J. Ross Mitchell and Patricia K. Doyle-Baker

Background:

The popularity of smartphones has led researchers to ask if they can replace traditional tools for assessing free-living physical activity. Our purpose was to establish proof-of-concept that a smartphone could record acceleration during physical activity, and those data could be modeled to predict activity type (walking or running), speed (km·h−1), and energy expenditure (METs).

Methods:

An application to record and e-mail accelerations was developed for the Apple iPhone®/iPod Touch®. Twentyfive healthy adults performed treadmill walking (4.0 km·h−1 to 7.2 km·h1) and running (8.1 km·h−1 to 11.3 km·h−1) wearing the device. Criterion energy expenditure measurements were collected via metabolic cart.

Results:

Activity type was classified with 99% accuracy. Speed was predicted with a bias of 0.02 km·h−1 (SEE: 0.57 km·h−1) for walking, –0.03 km·h−1 (SEE: 1.02 km·h−1) for running. Energy expenditure was predicted with a bias of 0.35 METs (SEE: 0.75 METs) for walking, –0.43 METs (SEE: 1.24 METs) for running.

Conclusion:

Our results suggest that an iPhone/iPod Touch can predict aspects of locomotion with accuracy similar to other accelerometer-based tools. Future studies may leverage this and the additional features of smartphones to improve data collection and compliance.

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Herman-J. Engels and Emily M. Haymes

This study examined the effects of a single dose of caffeine (5 mg:kg−1) on energy metabolism during 60-min treadmill walking at light (30% VO2max) and moderate (50% VO2max) aerobic intensities in eight sedentary (VO2max 39.6 ±t3.1 ml.kg−1.min−1) males. Caffeine intake 60 min prior to walking exercise increased pre- and postexercise FFA, glycerol, and lactate concentrations (p < 0.05). Blood glucose levels following walking trials were lower than preexercise values (p < 0.05). Gas exchange indicated that caffeine did not change exercise oxygen uptake, RER values, and carbon dioxide production (p0.05). In contrast, a small but statistically significant effect of caffeine on exercise minute ventilation was noted (p~0.01). It is concluded that ingestion of 5 mg.kg−1 caffeine increases the mobilization of energy substrate from fat sources; however, the present data do not provide evidence of a caffeineinduced shift in energy substrate usage. Caffeine is not an effective means for enhancing the energy cost of prolonged walking.

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David A. Rowe, David McMinn, Leslie Peacock, Arjan W. P. Buis, Rona Sutherland, Emma Henderson and Allan Hewitt

Background:

Walking cadence has shown promise for estimating walking intensity in healthy adults. Auditory cues have been shown to improve gait symmetry in populations with movement disorders. We investigated the walking cadence-energy expenditure relationship in unilateral transtibial amputees (TTAs), and the potential of music cues for regulating walking cadence and improving gait symmetry.

Methods:

Seventeen unilateral TTAs performed 2 5-min treadmill walking trials, followed by 2 5-min overground walking trials (self-regulated “brisk” intensity, and while attempting to match a moderate-tempo digital music cue).

Results:

Walking cadence significantly (P < .001) and accurately (R 2 = .55, SEE = 0.50 METs) predicted energy expenditure, and a cadence of 86 steps·min−1 was equivalent to a 3-MET intensity. Although most participants were able to match cadence to prescribed music tempo, gait symmetry was not improved during the music-guided condition, compared with the self-regulated condition.

Conclusions:

This is the first study to investigate the utility of walking cadence for monitoring and regulating walking intensity in adults with lower limb prosthesis. Cadence has similar or superior accuracy as an indicator of walking intensity in this population, compared with the general population, and adults with a unilateral TTA are capable of walking at moderate intensity and above for meaningful bouts of time.

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Christopher McCrum, Katrin Eysel-Gosepath, Gaspar Epro, Kenneth Meijer, Hans H.C.M. Savelberg, Gert-Peter Brüggemann and Kiros Karamanidis

Posturography is used to assess balance in clinical settings, but its relationship to gait stability is unclear. We assessed if dynamic gait stability is associated with standing balance in 12 patients with unilateral vestibulopathy. Participants were unexpectedly tripped during treadmill walking and the change in the margin of stability (MoSchange) and base of support (BoSchange) relative to nonperturbed walking was calculated for the perturbed and first recovery steps. The center of pressure (COP) path during 30-s stance with eyes open and closed, and the distance between the most anterior point of the COP and the anterior BoS boundary during forward leaning (ADist), were assessed using a force plate. Pearson correlations were conducted between the static and dynamic variables. The perturbation caused a large decrease in the BoS, leading to a decrease in MoS. One of 12 correlations was significant (MoSchange at the perturbed step and ADist; r = −.595, P = .041; nonsignificant correlations: .068 ≤ P ≤ .995). The results suggest that different control mechanisms may be involved in stance and gait stability, as a consistent relationship was not found. Therefore, posturography may be of limited use in predicting stability in dynamic situations.

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Leslie Peacock, Allan Hewitt, David A. Rowe and Rona Sutherland

Purpose:

The study investigated (a) walking intensity (stride rate and energy expenditure) under three speed instructions; (b) associations between stride rate, age, height, and walking intensity; and (c) synchronization between stride rate and music tempo during overground walking in a population of healthy older adults.

Methods:

Twenty-nine participants completed 3 treadmill-walking trials and 3 overground-walking trials at 3 self-selected speeds. Treadmill VO2 was measured using indirect calorimetry. Stride rate and music tempo were recorded during overground-walking trials.

Results:

Mean stride rate exceeded minimum thresholds for moderate to vigorous physical activity (MVPA) under slow (111.41 ± 11.93), medium (118.17 ± 11.43), and fast (123.79 ± 11.61) instructions. A multilevel model showed that stride rate, age, and height have a significant effect (p < .01) on walking intensity.

Conclusions:

Healthy older adults achieve MVPA with stride rates that fall below published minima for MVPA. Stride rate, age, and height are significant predictors of energy expenditure in this population. Music can be a useful way to guide walking cadence.

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Amanda Hickey, Dinesh John, Jeffer E. Sasaki, Marianna Mavilia and Patty Freedson

Background:

There is a need to examine step-counting accuracy of activity monitors during different types of movements. The purpose of this study was to compare activity monitor and manually counted steps during treadmill and simulated free-living activities and to compare the activity monitor steps to the StepWatch (SW) in a natural setting.

Methods:

Fifteen participants performed laboratory-based treadmill (2.4, 4.8, 7.2 and 9.7 km/h) and simulated free-living activities (eg, cleaning room) while wearing an activPAL, Omron HJ720-ITC, Yamax Digi-Walker SW-200, 2 ActiGraph GT3Xs (1 in “low-frequency extension” [AGLFE] and 1 in “normal-frequency” mode), an ActiGraph 7164, and a SW. Participants also wore monitors for 1-day in their free-living environment. Linear mixed models identified differences between activity monitor steps and the criterion in the laboratory/free-living settings.

Results:

Most monitors performed poorly during treadmill walking at 2.4 km/h. Cleaning a room had the largest errors of all simulated free-living activities. The accuracy was highest for forward/rhythmic movements for all monitors. In the free-living environment, the AGLFE had the largest discrepancy with the SW.

Conclusion:

This study highlights the need to verify step-counting accuracy of activity monitors with activities that include different movement types/directions. This is important to understand the origin of errors in step-counting during free-living conditions.

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Daniel A. Jacobs and Daniel P. Ferris

Instrumented insoles could benefit locomotion research on healthy and clinical populations by providing data in natural settings outside of the laboratory. We designed a low-cost, instrumented insole with 8 pneumatic bladders to measure localized plantar pressure information. We collected gait data during treadmill walking at 1.0 m/s and 1.5 m/s and for sit-to-stand and stand-tosit tasks for 10 subjects. We estimated a common representation of ground kinetics (3-component force vector, 2-component center of pressure position vector, and a single-component torque vector) from the insole data. We trained an intertask neural network for each component of the kinetic data. For the walking tasks at 1.0 m/s and 1.5 m/s, the normalized root mean square error was between 3.1% and 12.9% and for the sit-to-stand and stand-to-sit tasks, the normalized root mean square error was between 3.3% and 21.3% Our findings suggest that the proposed low-cost, instrumented insoles could provide useful data about movement kinetics during real-world activities.

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Timo Rantalainen, Nicolas H. Hart, Sophia Nimphius and Daniel W. Wundersitz

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.