The purpose of this study was to examine the effects of knee flexion angles during maximum isometric hip extension. Ten healthy men performed maximum isometric hip extension in prone position at 15° and 90° knee flexion. Then, the hip extension torque was measured, and electromyographic (EMG) data were obtained from the biceps femoris long head, semitendinosus, semimembranosus, adductor magnus, and gluteus maximus muscles. The EMG data were full-wave rectified and integrated (IEMG). The IEMG values obtained during the measurement of isometric hip extension were normalized with the values collected at 90° knee flexion (normalized IEMG [NIEMG]). The hip extension torque at 15° knee flexion was significantly greater than that at 90° knee flexion. The NIEMG values from the hamstrings at 15° knee flexion significantly increased compared with those at 90° knee flexion. Meanwhile, the NIEMG values from the gluteus maximus at 90° knee flexion were significantly greater than those at 15° knee flexion. However, the NIEMG values from the adductor magnus did not significantly differ between 15° and 90° knee flexion. These results indicate that the hamstrings effectively generate contracting force during isometric hip extension and at knee extended position because its fiber length was close to the optimal length.
The extensive use of food additives has increased the phosphorous content of the modern diet, while calcium intake has remained similar to past levels according to the national standards of nutrient intake. Although exercise increase bone mineral content, the intake of phosphorus may change the exercise effect. The purpose of this study was to examine the effects of jump exercise on bone and phosphate-calcium metabolism in rats consuming high levels of dietary phosphorous. Forty-two male Wistar rats aged 8 weeks were fed either a high-phosphorus diet with a 2.0 P/Ca ratio or a normal diet with a 1.0 P/Ca ratio. Rats from each dietary group were then further assigned to undergo 8 weeks of jump exercise or to be sedentary controls. Two-way analysis of variance (ANOVA) revealed that the bone mineral content (P<0.001), strength (P<0.001), transverse thickness (P<0.001), and longitudinal thickness (P<0.001) of the tibial diaphysis were increased by jump exercise in both dietary groups. The concentrations of serum inorganic phosphorus (P<0.001), FGF23 (P<0.001), and 1-25 (OH) vitamin D (P<0.001) were increased by a high phosphorus diet, and the concentrations of serum total calcium (P<0.05) and 1-25 (OH) vitamin D (P<0.05) were increased by jump exercise in both groups. In conclusion, exercise is important to increase bone mass and bone strength in a high phosphorus intake state.
The purpose of this study was to determine the effectiveness of combined aerobic and resistance training circuit on daily physical activity, motor function, and health-related QOL among community-dwelling women aged over 65. Of 102 subjects recruited from the local community, 60 met the inclusion criteria. The subjects were randomly divided into two groups: intervention and control. The intervention group was asked to participate in 60 minutes of combined aerobic and resistance training circuit three times a week for 3 months, while the control group was asked to participate in a study circle once a month for 3 months. Daily physical activity was measured by an activity monitor, and questionnaire, physical functioning, and health related QOL were measured before and after intervention. Daily physical activity as measured by the activity monitor increased significantly in the intervention group but not in the control group, although daily physical activity as measured by questionnaire did not significantly differ between groups. Distance walked over 6 minutes significantly increased in the intervention group than in the control group. No significant difference was found in health related QOL between groups. We conclude that combined aerobic and resistance training circuit is effective for increasing daily activity in community-dwelling older women and for enhancing physical function.
The purpose of this study was to investigate the effects of Lactobacillus gasseri OLL2809 (MG2809) intake on salivary secretory immunoglobulin A (SIgA) secretion and incidence of upper-respiratory tract infection (URTI) symptoms among college rugby athletes. Sixty-seven subjects were assigned to a MG2809 group (n = 33) or a placebo group (n = 34) using a double-blind procedure. Each subject took MG2809 or placebo tablets for 9 weeks. Resting saliva samples were collected before (0 week) and after 2, 4, 6, 8, and 9 weeks of the MG2809 intakes. A log of URTI symptoms was kept every day during the study period. Our results showed that salivary SIgA level was significantly increased at 6 weeks in the MG2809 group (p < 0.05), although the placebo group did not show significant change. The duration of URTI symptoms episode in the MG2809 group was significantly shorter than that in the placebo (p < 0.05). These results suggest that regular intake of MG2809 may enhance oral immune function mediated by SIgA and reduce the risk of URTI in athletes.
The purpose of this study was to examine the association of screen viewing time (SVT) and study time (ST) with physical fitness among second-year high school students. This cross-sectional study was carried out including 678 (boys: n = 322) students enrolled from 2011 to 2013. Physical fitness measurements included muscular fitness, explosive power and endurance performance. Muscular fitness and explosive power were evaluated by grip strength and standing broad jump test, respectively. Endurance performance was evaluated by endurance running speed of 1500 meters (in boys) or 1000 meters (in girls) running. SVT, ST and other lifestyle behaviors were obtained by a self-reported questionnaire. Analysis of covariance was used to examine the association of SVT and ST with grip strength, standing broad jump distance and endurance running speed. After adjustment for potential confounders, longer SVT was associated with poorer endurance running speed in both boys and girls, (p for trend < 0.01). Longer SVT was also associated with lower standing broad jump distance in boys (p for trend = 0.007) and grip strength in girls (p for trend = 0.005). In boys, longer ST was also associated with lower grip strength after adjustment for potential confounders (p for trend = 0.007). In conclusion, these results suggest that differences between SVT and ST may have different effects on physical fitness data 3-year after the earthquake disaster. Further studies are necessary to confirm the findings of this study.
The purpose of this study was to investigate the characteristics of running on self-driven treadmill equipped with curve-shaped bed (TM) from kinematics and kinetics variables by comparing with those obtained on overground running (OG). Eight healthy male subjects run on TM and OG under constant speed condition of 3m/s. Thirty five reflective anatomical landmarkers were attached on the subject according to Plug-in-gait model. Kinematics and kinetics data were recorded during stance phase using VICON MX (200fps) motion capture system and Kistler force plate (1kHz). Running spatio-temporal parameters such as stride length /stride frequency, lower limb joint kinematics and ground reaction force were compared between TM and OG conditions. Significant high stride frequency on TM running was indicated compare with OG condition (P<0.05). Contact time were almost same between TM and OG, whereas in vertical ground reaction force, non-first impact force as well as lower average loading rate were indicated in TM compared to OG (P<0.05). Lower joint kinematics were significantly different between TM and OG running during first 20% stance phase of normalized stance time. Hip and knee flexion angular velocities were larger in OG than TM (P<0.05). These results suggest that TM running causes lowed intensity for lower limb joints during stance phase, which might be applicable for prevention of running injury.
The purpose of this study was to investigate the characteristics of the past injuries of female junior high and high school soccer players in comparison with those of male junior high and high school soccer players. 41 female and 60 male players were examined for the past injuries that they had experienced. The incidence of injuries in females was 0.21±1.69 injuries per player per year compared to 0.28±0.41 injuries per player per year in males. There was not significant difference in the incidence of past injuries between males and females. The most frequently injured region was the ankle in females and the upper extremities in males. Females experienced frequent ligament injuries while males experienced frequent fractures. It was unusual that females experienced a higher rate of Osgood-Schlatter disease. Females also had more traumatic injuries caused by non-contact incidents. We conclude that it is important for female soccer players in junior high and high school to take measures to prevent ligament injuries in the lower leg and traumatic injuries caused by non-contact incidents. We need to conduct further research to reveal why the females experienced a higher rate of Osgood-Schlatter disease.
No consensus exists regarding the effects of electromagnetic waves from cell phones on the human body, and no studies have investigated effects on the locomotor system. To elucidate the effects on muscle strength during cell phone use, the present study investigated changes in hip abduction strength, visual analog scale (VAS) scores, surface electromyogram (EMG), and Root Mean Square (RMS) value. Hip abduction strength did not differ from the NORMAL when the cell phone was powered off, but significantly decreased when it was powered on. Moreover, no differences were observed in RMS and VAS during muscle exertion between states in which the cell phone was powered on or off. Even if there had been a placebo effect or effects of pressure on the temporal bone, the finding that some form of environmental change associated with reproducing the state in which one talks on a cell phone affects the human body is unable to be dismissed. The findings in this case were attributed to reduced function of the central nervous system rather than peripheral muscles or the peripheral nervous system. However, the cause of these findings cannot be identified from the present study. In view of the facts that “muscle strength decreases under conditions in which electromagnetic waves, however small, are emitted from cell phones” and “there are no changes in ease of exerting strength in the subjects themselves”, it was considered necessary both to investigate the causes of these findings and to implement measures in response to these facts.
This study examined the physiological response to different water depths in recreational synchronized swimming. Nine middle-aged, female, recreational swimmers carried out the same team free routines in deep water (deep-water synchronized swimming: DWS) and shallow water (shallow-water synchronized swimming: SWS). Heart rate (HR) was measured continuously during each performance, combined with estimation of metabolic equivalent (MET) values using individual linear regression equations of HR-oxygen uptake. These equations were created using the results of 12 water activities. Blood lactate concentration and systolic blood pressure were measured at the 1/3 and 2/3 stages and immediately after each performance period. HR and estimated METs during DWS (mean±SD, 152.9±7.5 beats·min-1 and 7.3±1.2) were significantly higher than those measured during SWS (131.8±11.3 beats·min-1 and 5.7±0.8). Blood lactate concentration and systolic blood pressure measured immediately after DWS were significantly higher than those measured after SWS. With DWS, blood lactate concentration at the 2/3 stage and immediately after the performance were significantly higher than those measured at the 1/3 stage, whereas in SWS no significant difference was found in these values at any time period. In conclusion, the exercise intensity of DWS was high and SWS moderate. The predominant sources of energy may be phosphocreatine stores and aerobic metabolism during these performances. It is possible that glycolysis may also play an important role in energy requirements during the 2/3 stage and immediately after a DWS performance.