In research, the accurate and reliable measurement of leg and vertical stiffness could contribute to valid interpretations. The current study aimed at determining the intraparticipant variability (ie, intraday and interday reliabilities) of leg and vertical stiffness, as well as related parameters, during high speed treadmill running, using the “sine-wave” method. Thirty-one males ran on a treadmill at 6.67 m∙s−1, and the contact and flight times were measured. To determine the intraday reliability, three 10-s running bouts with 10-min recovery were performed. In addition, to examine the interday reliability, three 10-s running bouts on 3 separate days with 48-h interbout intervals were performed. The reliability statistics included repeated-measure analysis of variance, average intertrial correlations, intraclass correlation coefficients (ICCs), Cronbach’s α reliability coefficient, and the coefficient of variation (CV%). Both intraday and interday reliabilities were high for leg and vertical stiffness (ICC > 0.939 and CV < 4.3%), as well as related variables (ICC > 0.934 and CV < 3.9%). It was thus inferred that the measurements of leg and vertical stiffness, as well as the related parameters obtained using the “sine-wave” method during treadmill running at 6.67 m∙s−1, were highly reliable, both within and across days.
Panagiotis Pappas, Giorgos Dallas and Giorgos Paradisis
Noah J. Rosenblatt, Christopher P. Hurt and Mark D. Grabiner
Recent experimental findings support theoretical predictions that across walking conditions the motor system chooses foot placement to achieve a constant minimum “margin of stability” (MOSmin)—distance between the extrapolated center of mass and base of support. For example, while step width varies, similar average MOSmin exists between overground and treadmill walking and between overground and compliant/irregular surface walking. However, predictions regarding the invariance of MOSmin to step-by-step changes in foot placement cannot be verified by average values. The purpose of this study was to determine average changes in, and the sensitivity of MOSmin to varying step widths during two walking tasks. Eight young subjects walked on a dual-belt treadmill before and after receiving information that stepping on the physical gap between the belts causes no adverse effects. Information decreased step width by 17% (p = .01), whereas MOSmin was unaffected (p = .12). Regardless of information, subject-specific regressions between step-by-step values of step width and MOSmin explained, on average, only 5% of the shared variance (β = 0.11 ± 0.05). Thus, MOSmin appears to be insensitive to changing step width. Accordingly, during treadmill walking, step width is chosen to maintain MOSmin. If MOSmin remains insensitive to step width across other dynamic tasks, then assessing an individual’s stability while performing theses tasks could help describe the health of the motor system.
Nicholas J. Walters and David A. Brodie
The purpose of this study was to assess the validity of data derived from the Kenz calorie counter during progressive, incremental treadmill exercise. Direct comparisons were made with calories calculated from on-line gas analysis. The subjects were 18 adults, 18 postadolescent children, and 24 preadolescent children. Linear regression (r 2 > .95) showed a progressive deviation away from a 1:1 relationship between Kenz data and V̇O2 data with increasing age of subject which remained when standardized to kcal · kg−1 body mass or kcal · m−2 · hour−1. The Kenz calorie counter, after applying an age group correction factor, can thus be used as a suitable analog for measured energy expenditure.
Gregory B. Dwyer and Anthony D. Mahon
Little is known about the responses to graded exercise in athletes with cerebral palsy (CP). This study compared the ventilatory threshold (VT) and peak VO2 among athletes with CP during treadmill and cycle ergometry exercise. Six (4 men, 2 women) track athletes with CP volunteered to participate in the study. Graded exercise tests on a treadmill and cycle ergometer were performed on separate days to assess VT and peak VO2. Paired t tests were used to compare the two exercise modes. The VT, expressed as a percentage of peak VO2, was significantly higher on the cycle ergometer than on the treadmill. The absolute VO2 at the VT was similar during both testing modes, and peak VO2 was significantly higher on the treadmill than on the cycle ergometer. Similar to responses seen in able-bodied individuals, the VO2 at VT was similar during both modes of exercise, while the peak VO2 was 10% lower on the cycle than on the treadmill. Cycle ergometer peak VO2 in these athletes was higher than previous reports of individuals with CP for the cycle ergometer.
Noemi Serra Paya, Assumpta Ensenyat, Jordi Gatius Real and Alfonso Blanco
This study aimed to evaluate differences between low active overweight and obese children in terms of energy expenditure (EE), ventilation (VE), and cardiac response during graded submaximal treadmill testing at constant speed.
We categorized 20 children into two weight groups according to the International Obesity Task Force criteria: overweight (n = 10; age = 9.7 ±1.34 years) and obese (n = 10; age = 10.4 ± 1.4 years). Children performed treadmill testing at a constant speed (1.53 ms1) and increasing grade (0%, 4%, and 8%). every 3 min.
The EE across all grades was significantly higher (p < .001) in obese than in overweight children. Differences at each grade disappeared when EE was adjusted by body mass; however, several differences remained when the EE was adjusted by fat-free mass or body surface area. The increase in EE with increasing grade was greater in obese children (effect size between 0% and 8% for EE was 1.17). BMI z-score and fat mass (kg) were the main predictors of EE (Kcal·min1) and contributed to explaining 66%, 70%, and 83.4% of the variance in EE at 0%, 4% and 8% gradients respectively.
We suggest that when assessing EE response to exercise, the degree of obesity should be taken into consideration.
Viswanath B. Unnithan and Roger G. Eston
Previous studies have consistently shown that the body mass/relative oxygen cost of submaximal treadmill running is greater in children than in young adults. It has been suggested that the obligatory increased stride frequency in children might be at least partly responsible. This hypothesis was investigated by examining the association between stride frequency and oxygen demand characteristics in 10 aerobically fit prepubescent boys (ages 9-10 yrs) and 10 fit young men (ages 18-25 yrs) while running at fixed submaximal speeds on an electronically driven treadmill. The oxygen demand was higher at all running speeds in the boys’ group. To compensate for a shorter stride length, the boys demonstrated higher stride frequency at all speeds. To determine if the inferior running economy in the boys was partly due to the greater stride frequency, the relative oxygen demand per stride was compared between groups at all speeds. This value was similar in both groups. It is concluded that the apparently greater oxygen demand of running in boys may be due in part to the greater stride frequency required to maintain similar running speeds.
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.
Jennifer M. DiNallo, Danielle Symons Downs and Guy Le Masurier
To effectively promote physical activity (PA) and quantify the effects of PA interventions for pregnant women, PA measurement during pregnancy needs improvement. The purpose of this study was to assess PA monitor output during a controlled, treadmill walking protocol among pregnant women at 20- and 32-weeks gestation.
Women (N = 43) wore an Actigraph accelerometer, NL1000, and Yamax pedometer during a 20-minute treadmill walking test [5-minute periods at 4 different speeds (54, 67, 80, and 94 m·min−1)] at 20- and 32-weeks gestation.
Repeated-measures ANOVAs indicated that Actigraph total counts/minute and minutes of moderate-vigorous PA (MVPA), NL1000 steps and minutes MVPA, and Yamax steps decreased from 20- to 32-weeks gestation (P ≤ .05), while body girth circumference and activity monitor tilt increased (P ≤ .05). Repeated measures ANCOVAs, controlling for changes in body girth and monitor tilt, yielded no significant differences in any outcome measures from 20- to 32-weeks gestation.
Preliminary results suggest physical changes during pregnancy impact activity monitor output in controlled settings. Accurately measuring and statistically controlling for changes in body girth at monitor placement site and monitor tilt may improve the accuracy of activity monitors for use with pregnant populations.
Ian Rollo, Clyde Williams, Nicholas Gant and Maria Nute
The purpose of this study was to examine the influences of a carbohydrate (CHO) mouth rinse on self-selected running speeds during a 30-min treadmill run. Ten endurance-trained men performed 2 trials, each involving a 10-min warm-up at 60% VO2max followed by a 30-min run. The run was performed on an automated treadmill that allowed the spontaneous selection of speeds without manual input. Participants were asked to run at speeds that equated to a rating of perceived exertion of 15, mouth rinsing with either a 6% CHO or taste-matched placebo (PLA) solution. In addition to recording self-selected speeds and total distance covered the authors assessed the runners’ subjective feelings. The total distance covered was greater during the CHO than during the PLA trial (p < .05). Faster speeds selected during the first 5 min of exercise corresponded with enhanced feelings of pleasure when mouth rinsing with the CHO solution. Mouth rinsing with a CHO solution increased total distance covered during a self-selected 30-min run in comparison with mouth rinsing with a color- and tastematched placebo.
Steven P. Singleton, James T. Fitzgerald and Anne Victoria Neale
This study was conducted to determine the exercise habits and fitness status of healthy older black and white adults, ages 50 to 80 years. The 384 subjects were enrolled in a health promotion project conducted by a midwestern medical school. Self-reported exercise levels were higher for men than for women and were higher for whites compared with blacks. Age had the greatest impact on treadmill performance for both sexes. Activity levels declined with age for men but not for women. Self-reported exercise levels were highly predictive of fitness status for men but not for women. The relationship in older adults between activity levels and both measured fitness and health status needs further investigation.