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  • Author: William C. Byrnes x
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Lauri M. Webber, William C. Byrnes, Thomas W. Rowland and Vicky L. Foster

Although delayed onset muscle soreness and increased serum creatine kinase activity (SCKA) following unaccustomed exercise is common in adults, little is known concerning these responses in children. The perception of muscle soreness and SCKA in children (n = 16) (M age = 10.4±.30 yr) was compared to a control group of adults (n = 15) (M age = 27.1±.87 yr) following a single bout of downhill running (30 min − 10% grade). Preexercise SCKA was not significantly different between the children (91.7±8.5 μmol•L−1•min−1) and the adults (77.1±5.9 μmol•L−1•min−1). The difference in SCKA (pre to 24 hours post) was significantly less (p<.01) for the children (68.6±16.2 μmol•L−1•min−1) than for the adults (188.7±36.8 μmol•L−1•min−1). When the groups were adjusted for weight differences, SCKA was not significantly different between the adults and the children. Regardless of age, males demonstrated a significantly greater increase in SCKA postexercise when compared to females. Soreness ratings (verbally anchored scale from 1 to 10) 24 hours following the downhill run were not significantly different between the children (3.8±.6) and the adults (4.5±.7). Following an eccentrically biased exercise task, children exhibited less of a SCKA response compared to adults that is related to body weight.

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James E. Peterman, Kalee L. Morris, Rodger Kram and William C. Byrnes

Background: In laboratory settings, cycling workstations improve cardiometabolic risk factors. Our purpose was to quantify risk factors following a cycling intervention in the workplace. Methods: Twenty-one office workers who sat at work ≥6 hours per day underwent baseline physiological measurements (resting blood pressure, blood lipid profile, maximum oxygen consumption [V˙O2max], body composition, and 2-h oral glucose tolerance test). Participants were randomly assigned to a 4-week intervention only group (n = 12) or a delayed intervention group (n = 9) that involved a 4-week control condition before beginning the intervention. During the intervention, participants were instructed to use the cycling device a minimum of 15 minutes per hour, which would result in a total use of ≥2 hours per day during the workday. Following the intervention, physiological measurements were repeated. Results: Participants averaged 1.77 (0.48) hours per day of cycling during the intervention with no changes in actigraphy-monitored noncycling physical activity. Four weeks of the workplace intervention increased V˙O2max (2.07 [0.44] to 2.17 [0.44] L·min−1, P < .01); end of V˙O2max test power output (166.3 [42.2] to 176.6 [46.1] W, P < .01); and high-density lipoprotein cholesterol (1.09 [0.17] to 1.17 [0.24] mmol·L−1, P = .04). Conclusions: A stationary cycling device incorporated into a sedentary workplace for 4 weeks improves some cardiometabolic risk factors with no compensatory decrease in noncycling physical activity.