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Yuri Feito, David R. Bassett, Dixie L. Thompson and Brian M. Tyo

Background:

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.

Methods:

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).

Results:

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.

Conclusion:

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.

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Randall J. Bergman, Justin W. Spellman, Michael E. Hall and Shawn M. Bergman

Background:

This study examined the validity of a selected free pedometer application (iPedometer; IP) for the iPhone that could be used to assess physical activity.

Methods:

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).

Results:

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).

Conclusion:

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.

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Scott W. Ducharme and Richard E.A. van Emmerik

clear consensus has not been agreed upon. Finally, treadmill versus overground walking may produce differences in scaling exponents, as treadmill walking generally reduces the scaling exponent ( Terrier & Deriaz, 2011 ). In addition to preferred speed walking conditions, long-range correlations in young

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Danielle R. Bouchard, K. Ashlee McGuire, Lance Davidson and Robert Ross

One hundred forty-six abdominally obese adults age 60–80 yr were studied to investigate the interaction between cardiorespiratory fitness (CRF) and obesity on functional limitation. Obesity was determined by fat mass (FM), CRF was determined by a maximal treadmill test, and functional limitation was based on 4 different tasks that are predictive of subsequent disability. Both FM (r = –.34, p ≤ .01) and CRF (r = .54, p ≤ .01) were independently associated with functional limitation in bivariate analysis. After further control for sex, age, and the interaction term (CRF × FM), FM was no longer independently associated with functional limitation (p = .10). Analyses were also based on sex-specific tertiles of FM and CRF. The referent group demonstrated significantly lower functional limitation than the low-CRF/low-FM and the low-CRF/high-FM groups (both p ≤ .05). These results highlight the value of recommending exercise for abdominally obese adults.

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James B. Dear, Michelle M. Porter and A. Elizabeth Ready

This study compared the intensity and energy cost of playing 9 holes of golf with 40 min of lawn mowing in older men and determined whether both met the current recommendations for health benefits. Eighteen men (age 71.2 ± 4.4 yr, BMI 27.3 ± 2.3; M ± SD) completed a graded treadmill test. During golfing and lawn-mowing field tests, oxygen consumption and walking velocity and distance were measured using a portable metabolic system and global positioning system receiver. The net energy costs of golfing and lawn mowing were 310 and 246 kcal, respectively. The average intensities in metabolic equivalents of golfing and lawn mowing were 2.8 ± 0.5 and 5.5 ± 0.9, respectively. Both lawn mowing and golfing met the original intensity and energy expenditure requirements for health benefits specified by the American College of Sports Medicine in 1998, but only lawn mowing met the 2007 intensity recommendations.

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Regina R. Buccello-Stout, Ronita L. Cromwell, Jacob J. Bloomberg and Elbert B. Whorton

The goal of this study was to determine if exposure to sensorimotor adaptation training improved head stabilization in older adults. Sixteen participants, age 66–81 yr, were assigned at random to the control group (n = 8) or the experimental group (n = 8). Both groups first completed 6 trials of walking a foam pathway consisting of a moveable platform that induced a lateral perturbation during walking. Head-in-space and trunk-in-space angular velocities were collected. Participants from both groups then trained twice per week for 4 wk. Both groups walked on a treadmill for 20 min. The control group viewed a static scene. The experimental group viewed a rotating visual scene that provided a perceptual-motor mismatch. After training, both groups were retested on the perturbation pathway test. The experimental group used a movement strategy that preserved head stabilization compared with the controls (p < .05). This training effect was not retained after 4 wk.

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Nora E. Miller, Scott J. Strath, Ann M. Swartz and Susan E. Cashin

This study examined the predictive validity of accelerometers (ACC) to estimate physical activity intensity (PAI) across age and differences in intensity predictions when expressed in relative and absolute PAI terms. Ninety adults categorized into 3 age groups (20–29, 40–49, and 60–69 yr) completed a treadmill calibration study with simultaneous ACC (7164 Actigraph) and oxygen-consumption assessment. Results revealed strong linear relations between ACC output and measured PAI (R 2 = .62–.89) across age and similar ACC cut-point ranges across age delineating absolute PAI ranges compared with previous findings. Comparing measured metabolic equivalents (METs) with estimated METs derived from previously published regression equations revealed that age did not affect predictive validity of ACC estimates of absolute PAI. Comparing ACC output expressed in relative vs. absolute terms across age revealed substantial differences in PAI ACC count ranges. Further work is warranted to increase the applicability of ACC use relative to PAI differences associated with physiological changes with age.

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Eric D. Vidoni, Anna Mattlage, Jonathan Mahnken, Jeffrey M. Burns, Joe McDonough and Sandra A. Billinger

The purpose of this study was to determine the validity of a submaximal exercise test, the Step Test Exercise Prescription (STEP), in a broad age range and in individuals in the earliest stages of Alzheimer’s disease (AD). Individuals (n = 102) underwent treadmill-based maximal exercise testing and a STEP. The STEP failed to predict peak oxygen consumption (VO2peak), and was a biased estimate of VO2peak (p < .0001). Only 43% of subjects’ STEP results were within 3.5 ml · kg–1 · min–1 of VO2peak. When categorized into fitness levels these 2 measures demonstrated moderate agreement (kappa = .59). The validity of the STEP was not supported in our participants, including those with AD. The STEP may not be appropriate in the clinic as a basis for exercise recommendations in these groups, although it may continue to have utility in classifying fitness in research or community health screenings.

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K. Fiona Iredale and Myra A. Nimmo

Thirty-three men (age 26–55 years) who did not exercise regularly were exercised to exhaustion using an incremental treadmill protocol. Blood lactate concentration was measured to identify lactate threshold (LT, oxygen consumption at which blood lactate concentration begins to systematically increase). The correlation coefficient for LT (ml · kg−1 · min−1) with age was not significant, but when LT was expressed as a percentage of peak oxygen consumption (VO2 peak), the correlation was r = +.69 (p < .01). This was despite a lack of significant correlation between age and VO2 peak (r = −.33). The correlation between reserve capacity (the difference between VO2 peak and LT) and age was r = −.73 (p < .01 ), and reserve capacity decreased at a rate of 3.1 ml · kg−1 · min−1 per decade. It was concluded that the percentage of VO2 peak at which LT occurs increases progressively with age, with a resultant decrease in reserve capacity.

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Nobuo Takeshima, Masatoshi Nakata, Fumio Kobayashi, Kiyoji Tanaka and Michael L. Pollock

The purpose of this study was to determine the effects of head-out-of-water immersion (HOI) on elderly subjects’ heart rate (HR) and oxygen uptake (V̇O2) responses to graded walking exercise. Subjects were 15 elderly participants. who selected three walking speeds and exercised for 6 min at each intensity on land and in the water. HOI exercise was carried out with subjects immersed to the level of the axilla. HR response at a given V̇O2 during walking with HOI was similar to the values found for walking on land, in contrast to published data on young subjects. The findings are consistent with the hypothesis that water immersion-induced central redistribution of blood volume changes with advancing age and may lead to a difference in the HR–V̇O2 relationship during HOI walking in the elderly compared to the young. This has important implications for prescribing exercise to the elderly when using treadmill HR values for HOI walking training.