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  • Author: Donald R. Dengel x
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Christopher Reiff, Kara Marlatt and Donald R. Dengel

Background:

Traditional desks require students to sit; however, recently schools have provided students with nontraditional standing desks. The purpose of this study was to investigate differences in caloric expenditure of young adults while sitting at a standard classroom desk and standing at a nontraditional standing classroom desk.

Methods:

Twenty (10 male/10 female) young (22.8 ± 1.9 y), healthy participants reported to the laboratory between the hours of 7:00 AM and 2:00 PM following a 12-h fast and 48-h break in exercise. Participants were randomly assigned to perform a series of mathematical problems either sitting at a normal classroom desk or standing at a nontraditional standing desk. Inspired and expired gases were collected for 45-min for the determination of oxygen consumption (VO2), carbon dioxide production (VCO2), and minute ventilation (VE) using a metabolic gas system.

Results:

There were significant increases from sitting to standing in VO2 (0.22 ± 0.05 vs. 0.28 ± 0.05 L·min−1, P ≤ .0001), VCO2 (0.18 ± 0.05 vs. 0.24 ± 0.050 L·min−1, P ≤ .0001), VE (7.72 ± 0.67 vs. 9.41 ± 1.20 L·min−1, P ≤ .0001), and kilocalories expended per minute (1.36 ± 0.20 kcal/ min, P ≤ .0001 vs. 1.02 ± 0.22 kcal/min, P ≤ .0001).

Conclusions:

Results indicate a significant increase in caloric expenditure in subjects that were standing at a standing classroom desk compared with sitting at a standard classroom desk.

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Mary O. Hearst, John R. Sirard, Leslie Lytle, Donald R. Dengel and David Berrigan

Background:

The association of physical activity (PA), measured 3 ways, and biomarkers were compared in a sample of adolescents.

Methods:

PA data were collected on 2 cohorts of adolescents (N = 700) in the Twin Cities, Minnesota, 2007–2008. PA was measured using 2 survey questions [Modified Activity Questionnaire (MAQ)], the 3-Day Physical Activity Recall (3DPAR), and accelerometers. Biomarkers included systolic (SBP) and diastolic blood pressure (DBP), lipids, percent body fat (%BF), and body mass index (BMI) percentile. Bivariate relationships among PA measures and biomarkers were examined followed by generalized estimating equations for multivariate analysis.

Results:

The 3 measures were significantly correlated with each other (r = .22–.36, P < .001). Controlling for study, puberty, age, and gender, all 3 PA measures were associated with %BF (MAQ = −1.93, P < .001; 3DPAR = −1.64, P < .001; accelerometer = −1.06, P = .001). The MAQ and accelerometers were negatively associated with BMI percentile. None of the 3 PA measures were significantly associated with SBP or lipids. The percentage of adolescents meeting the national PA recommendations varied by instrument.

Conclusions:

All 3 instruments demonstrated consistent findings when estimating associations with %BF, but were different for prevalence estimates. Researchers must carefully consider the intended use of PA data when choosing a measurement instrument.

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Christopher Kaufman, Aaron S. Kelly, Dan R. Kaiser, Julia Steinberger and Donald R. Dengel

The objective of this study was to investigate the effect of an 8-week aerobic-exercise training program on ventilatory threshold and ventilatory efficiency in overweight children. Twenty overweight children (BMI > 85th percentile) performed a graded cycle exercise test at baseline and were then randomly assigned to 8 weeks of stationary cycling (n = 10) or a nonexercising control group (n = 10). Ventilatory variables were examined at ventilatory threshold (VT), which was determined via the Dmax method. After 8 weeks, significant improvements occurred in the exercise group compared with the control group for oxygen uptake at VT (exercise = 1.03 ± 0.13 to 1.32 ± 0.12 L/min vs. control = 1.20 ± 0.10 to 1.11 ± 0.10 L/min, p < .05) and ventilatory equivalent of carbon dioxide (VE/VCO2) at VT (exercise = 32.8 ± 0.80 to 31.0 ± 0.53 vs. control = 30.3 ± 0.88 to 31.7 ± 0.91, p < .05). Aerobic-exercise training might help reverse the decrements in cardiopulmonary function observed over time in overweight children.

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Donald R. Dengel, Peter G. Weyand, Donna M. Black and Kirk J. Cureton

To investigate the effects of varying levels of hypohydration on ratings of perceived exertion (RPE) during moderate and heavy submaximal exercise, and at the lactate threshold (LT) and ventilatory threshold (VT), 9 male subjects cycled under states of euhydration (EU), moderate hypohydration (MH), and severe hypohydration (SH). The desired level of hypohydration was achieved over a 36-hr period by having subjects cycle at 50% VO2max in a 38°C environment on two occasions while controlling fluid intake and diet. During submaximal exercise, oxygen uptake, ventilation, heart rate, blood lactate, and RPE were not significantly different among treatments. Hypohydration did not significantly alter LT or VT, or perceptual responses at LT or VT. It is concluded that hypohydration of up to 5.6% caused by fluid manipulation and exercise in the heat over a 36-hr period does not alter RPE or the lactate or ventilatory threshold, nor RPE at the lactate and ventilatory thresholds measured during moderate and heavy submaximal cycling in a neutral (22°C) environment.

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Danielle L. Templeton, Aaron S. Kelly, Julia Steinberger and Donald R. Dengel

We assessed relative bone mineral content (BMC) in normal-weight (BMI < 85th percentile), overweight (BMI ≥ 85th—< 95th percentile), and obese (BMI ≥ 95th percentile) adolescents and evaluated the impact of nonweight bearing stationary cycle exercise training in a subset of obese participants. Obese and overweight adolescents had higher (p = .001) BMC than normal-weight counterparts, but after adjusting for total body mass the overweight and obese adolescents had a significantly lower (p < .001) BMC than normal-weight subjects. Although aerobic training such as cycling would seem optimal for caloric expenditure in obese adolescents, this study showed that eight weeks of cycle training did not improve BMC in obese adolescents. Weight-bearing aerobic exercise would be a better option for optimizing bone health in this population.