ABSTRACT
Recently, a standing desk is being installed as a behavior change strategy to reduce sitting time in the workplace. However, the standing posture has been suggested to decrease forehead oxygenated hemoglobin (oxy-Hb), which might impair task performances. Therefore, we examined whether prolonged standing impairs speed and accuracy of computer subtraction task associated with a decrease in forehead oxy-Hb. Nine healthy young males completed 4 × 15-min computer tasks under two conditions, i.e., sitting and standing. In the computer tasks, all subjects were required to subtract a two-digit number from a four digit number written on the paper and to input the answer to the answer colomn on the computer. Task performances were evaluated as the number of achievements and accuracy rate every 15 minutes. Moreover, oxy-Hb and deoxygenated-hemoglobin (deoxy-Hb) in the site of left forehead area and lower limb were monitored throughout the experimental period by near-infrared spectroscopy. Forehead oxy-Hb was significantly associated with the number of achievements during computer tasks (p < 0.001). In addition, forehead oxy-Hb and task performances did not differ between sitting and standing. The number of achievements of subtraction task under standing condition was significantly decreased as time proceeds. Our results demonstrate that prolonged standing might impair computer subtraction task performances irrespective of the change in forehead oxy-Hb.
ABSTRACT
The purpose of this study was to investigate the effect of attenuation of exercise-induced oxidative stress by antioxidant administration on brain-derived neurotrophic factor (BDNF) expression in the rat hippocampus. Wistar rats were assigned to four groups: non-exercise (Cont), exercise (Ex), or the combination of exercise with antioxidant administration (small dose: SP, large dose: LP) group. Exercise groups were subjected to treadmill running for 10 consecutive days. The exercise load increased gradually by 5 m/min per day for the first 5 days (10 m/min-30 m/min), and maintained at 30 m/min for the last 5 days. In addition, SP and LP were injected with N-tert butyl-a-phenyl nitrone (PBN) 1h prior to exercise. High-intensity exercise resulted in increased hippocampal 4-hydroxy-2-nonenal (4-HNE) contents compared with Cont. But this elevation was completely suppressed by a large dose of PBN. In Ex and SP, serum total antioxidative power were significantly decreased compared with Cont, whereas no changes were observed in LP. There was a significant negative correlation between hippocampal 4-HNE contents and serum total antioxidative power in SP and LP, suggesting the hypothesis that exercise-induced reduction in total antioxidant power might lead hippocampal 4-HNE accumulation. Furthermore, there was a significant increase of hippocampal BDNF level in LP compared with Cont and Ex. These findings indicate that an increase of oxidative stress might not have a beneficial effect on hippocampal BDNF expression. Our results of this study also suggest that attenuation of exercise-induced oxidative stress by some antioxidants contributes to BDNF expression in the hippocampus.
ABSTRACT
The purpose of this study was to investigate heme oxygenase-1 (HO-1) mRNA expression and bilirubin concentration alteration in humans exposed to acute hypoxia. Fourteen healthy adult males were randomly assigned to a sea level group and a hypoxia group, and then exposed to normoxia (400 m, 20.0 %O<sub>2</sub>) and hypoxia (3,000 m, 14.5 %O<sub>2</sub>) respectively, in a hypoxic chamber for 3 hours. SpO<sub>2</sub> during hypoxia were significantly lower than those at sea level (P＜0.05). Indirect bilirubin levels after hypoxia were significantly higher than those at sea level (P＜0.05). However, HO-1 mRNA expression was unaltered by hypoxia. In conclusion, our data indicate that an acute exposure to hypoxia at resting state for 3 hours might lead to antioxidative cytoprotective response without any increase in HO-1 gene expression.
ABSTRACT
The college years are an opportune timepoint of intervention in the primary prevention of osteoporosis. However, the effects of anthropometrical measures and lifestyle-related factors on the changes in bone mass during college years are unclear. The purpose of this study was thus to identify the determinants of the changes in calcaneal quantitative ultrasound (QUS) bone parameters (stiffness index: SI, speed of sound: SOS, broadband ultrasound attenuation: BUA) over 2 years in healthy Japanese college women (n=128). Correlation analysis revealed several significant relationships between the change rates in QUS parameters and anthropometry. Particularly, the changes in SI and BUA are highly correlated with the 2-year change in lean body mass (LBM). The subsequent multiple liner regression analysis also supported that the change in LBM was the significant predictor for the incremental rate of SI and BUA. All subjects then categorized into some grades, concerning about following lifestyle-related and physical variables during the last 2 years, living condition, sleeping time, alcohol consumption, smoking, meal skipping, dairy foods intake, instant foods intake, regular physical activity, regularity of menstruation, history of fracture, and history of dieting to reduce body weight. The incremental rates of all QUS parameters (i. e., SI, SOS, BUA) were positively associated with participation in regular physical activity. In addition, women who have continuously participated in regular physical activity from high school to college showed significant increases in SI and SOS compared with those who are not physically active or whose level of physical activity decline during college years. In conclusion, our study indicates that changes in QUS parameters in college-aged women were influenced by changes in anthropometric measures, especially LBM. It might suggest the importance of participation in regular physical activity to increase skeletal muscle mass. Our results also support the view that college women should maintain or increase regular physical activity before and after entering the college to maximize peak bone mass or lessen the age-related loss in bone mass in adulthood.
ABSTRACT
The purpose of this study was to examine the effects of anthropometric measures, including body height, body weight, body mass index (BMI), fat mass (FM), and lean body mass (LBM), on quantitative ultrasound (QUS) parameters of calcaneus in 358 Japanese university women. Ultrasonic bone densitometer (Achilles, Lunar corp.) was utilized to measure broadband ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index (SI) of the right calcaneus. The average of SI in this study showed a slight lower value (84, 3±12.1, mean±SD) compared with that in age-matched university women as previously reported. The contradictive finding may suggest the need for a large-scale further investigation on SI in young women. Correlation analysis revealed that both BUA and SI are significantly correlated with all anthropometric measures. However SOS had only weak correlation with LBM. In consideration of the high colinearities of body weight and BMI with FM and LBM, the multiple liner regression analysis was conducted with BUA, SOS, and SI as dependent variables. Body height, FM, and LBM were then entered to a forward stepwise regression model. The analysis proved that the significant predictor of BUA, SOS, and SI is LBM. It also suggested BUA to be stronger correlated with LBM than the other QUS parameters, SOS and SI. In conclusion, our re sults support the view that QUS parameters appear to be influenced by anthropometric measures, especially by LBM in Japanese university women. It is conceivable that an increase in skeletal mus cle mass chiefly induced by physical exercise contributes to the improvement of bone mass as measured by QUS in young women.