ABSTRACT
Keeping upright stance is important to other complex motions like locomotion and running for human beings. The mechanism of balance-keeping control in upright standing is still unknown. This study was conducted to analyze the body sway by using a simple PID (proportional, integral, derivative) control model and to investigate the influence of vision on its gains. Ten healthy subjects took part in the study. The upright body was modeled as one-link inversed pendulum model. While determining the model parameters according to subject's physical statue, the gain of PID parameters, (<i>K<sub>P</sub></i>, <i>K<sub>D</sub></i>, <i>K<sub>I</sub></i> are gains of proportion, derivative, and integral respectively.) could be estimated. Four kinds of visual patterns, (three for central visual field stimulation, one is eyes closed) were designed for visual stimulation. The results showed that the gain of <i>K<sub>D</sub></i> was decreased significantly in eyes closed (131.5±37.6 Nms/rad in eyes open and 90.4±26.0 Nms/rad in eyes closed, p<0.001), and, <i>K<sub>P</sub></i>, <i>K<sub>I</sub></i> were not changed. The results suggested that the PID control model was a promising means for individual balance ability analysis and that the visual effect on balance-keeping control in upright standing was analogized to a damper in the mechanical system.
ABSTRACT
Masked obesity is the presence of obesity based on percent body fat (%BF) when the body mass index (BMI) shows an absence of obesity. To examine the relationship between masked obesity and arteriosclerosis risk factors, we compared both serum lipid levels and the prevalence of hyperlipidemia in male and female high school freshmen with and without masked obesity. Subjects consisted of 403 male and 326 female high school students aged 15∼16 years. Of these, 34(8.4%) males and 36(11.0%) females had masked obesity, defined as 17≤BMI<23.60 and %BF≥25% in males, and 17≤BMI<24.17 and %BF≥30% in females, while the remaining 300 males and 246 females were not obese, having 17≤BMI<23.60 and %BF<25% and 17≤BMI<24.17 and %BF<30%, respectively. For both sexes, serum total-cholesterol (TC), low-density lipoprotein cholesterol (LDLC), triglycerides and the arteriosclerotic index (AI) were significantly higher (p<0.05∼0.01) in those with masked obesity. And many of the subjects with masked obesity had abnormal levels of TC, LDLC and AI, compared with those who were not obese (p<0.05∼0.01). Additionally, we compared both serum lipid levels and the prevalence of hyperlipidemia between subjects with masked obesity and control groups with the same BMI values. As a result, subjects with masked obesity had high serum lipid levels and a prevalence of hyperlipidemia. These results support the existence of masked obesity and suggest that masked obesity is associated with increased serum lipid levels, and thus could be a risk factor for arteriosclerosis in male and female high school freshmen.
ABSTRACT
The purpose of this study was to identify the relationships between trunk sway (TS) and the motion of center of pressure (COP) during quiet upright stance. Eight young healthy subjects (averaged 24±6.7 years) including 3 females were recruited for this study. By comparing TS with COP, we found that TS is moving in phase with COP both in lateral and sagittal plane. On the basis of observations that the COP-TS error signal is very similar to the changes of friction between the feet and floor. We also found that the friction is the impetus of trunk sway obeying the Newton's law. Then, a dynamic model between TS and COP can be identified. The results showed that TS and the motion of COP are in accordance with a specific differential equation. Supporting TS is <I>v</I> and COPS is <I>u</I>, then <I>u</I> can be expressed as : <I>u=-Hm/k v+hv</I>, where <I>H, k, h</I> are constants, <I>m</I> is the body mass. The simulation results fitted the experimental findings very well. The results suggested that TS instead of COP is a promising index for human standing ability assessment.
ABSTRACT
The purpose of this study was to investigate the effects of short-term living and training at an altitude of 1, 300 to 1, 800 m on physiological responses of high school elite endurance athletes. Fifteen male and seven female senior high school elite athletes, aged from 15 to 18, from three different sports (cross-country skiing, long-distance running and endurance cycling), participated in our study. The short-term (6 days) altitude exposure did not elicit abnormal responses of body tempera-ture, body weight, blood pressure or urine samples. There were also no significant changes in blood parameters examined before and after altitude exposure. Resting heart rate (HR) increased at altitude and presented an initial peak value followed by a steady decline on the following days of altitude exposure. Blood lactate concentration and exercise peak llR examined by submaximal 20-m shuttle run test decreased after the ascent to altitude and still showed lower values at postaltitude than at prealtitude. We conclude that 6-day living and training at an altitude of 1, 300 to 1, 800 m elicits positive decrements of exercise blood lactate and exercise peak HR as well as adaptive changes of resting IlR for these high school elite endurance athletes, which are probably related to an attenuation of muscle glycogen utilization and alterations in the autonomic neural system taken at altitude.
ABSTRACT
The purpose of this study was to ascertain whether exercise training cardiac adaptation exists in student rugby athletes, to define an adaptive pattern and to observe the student rugby athletics cardiac adaptive process. Subjects consisted of 42 male senior high school student rugby athletes, who participated in sports in junior high school, and a control group of sedentary students from the same senior high school who were matched for age. Student athletes were measured once a year over a three-year period. Left ventricular internal dimension at the end-diastole (LVIDd) and left ventricular posterior wall thickness at the end-diastole (PWT) were both measured by echocardiography. Because all subjects were growing adolescents, allometric scaling data (which is LVIDd/BSA<SUP>0.5</SUP> and PWT/BSA<SUP>0.5</SUP>) was used for comparison, to preclude the effect of differences in body size on LVIDd and PWT. Cross-sectional comparisons of athletic students with controls were conducted for each of the three senior high school grades, respectively. The data of student athletes during the three-year study was used for longitudinal comparisons. The results of cross-sectional comparisons showed that LVIDd/BSA<SUP>0, 5</SUP> in a student athlete group consisting of the three grades combined was greater than the corresponding control group (P<0.05, P<0.01, respectively) . PWT/BSA<SUP>0.5</SUP> in the athletic group was greater than the control group for the third grade level (P<0.05) . The results of the longitudinal comparison revealed that no significant differences were present in LVIDd/BSA<SUP>0.5</SUP> during the three-year investigation (P>0.05, respectively) . PWT/BSA<SUP>0.5</SUP> at the second and third grade level were obviously greater than at the first grade level (P<0.05, respectively) ; however, no dif. ference between the second and third grade levels existed. The results of this present study suggest that regular rugby exercise training during senior high school obviously induced left ventricular posterior wall thickening in the athletic students. An enlarged left ventricular cavity was observed at the first grade level of senior high school and did not significantly change during three years of senior high school.
ABSTRACT
A 32-year-old woman was referred to our hospital during the 35th week of pregnancy because of chest pain and dyspnea. The cesarean section was performed and a healthy infant was delivered. On the 16th hospital day, she developed heart failure. Echocardiograms revealed protrusion of the mitral valve into the left atrium in systole, vegetation and worsening of mitral regurgitation. CT showed splenic infarction. Mitral valve replacement was performed after inflammatory findings were improved by antibiotics. We reported here a case of infective endocarditis during the perinatal period.