AIM: To evaluate if static stretching influences peak and end-range functional hamstring-to-quadriceps(H/Q) strength ratios in elite women athletes. METHODS: Eleven healthy female athletes in an elite competitive leve...AIM: To evaluate if static stretching influences peak and end-range functional hamstring-to-quadriceps(H/Q) strength ratios in elite women athletes. METHODS: Eleven healthy female athletes in an elite competitive level participated to the study. All the participants fulfilled the static stretching or non-stretching(control) intervention protocol in a randomized design on different days. Two static unassisted stretching exercises, one in standing and one in sitting position, were used to stretch both the hamstring and quadriceps muscles during these protocols. The total time for the static stretching was 6 ± 1 min. The isokinetic peak torque measurements for the hamstring and quadriceps muscles in eccentric and concentric modes and the calculations for the functional H/Q strength ratios at angular velocities of 60°/s and 180°/s were made before(pre) and after(post) the control or stretching intervention. The strength measurements and functional strength ratio calculations were based during the entire- and end-range of knee extension.RESULTS: The pre-test scores for quadriceps and hamstring peak torque and end range values were not significantly different between the groups(P > 0.05). Subsequently, although the control group did notexhibit significant changes in quadriceps and hamstring muscle strength(P > 0.05), static stretching decreased eccentric and concentric quadriceps muscle strength at both the 60°/s and 180°/s test speeds(P < 0.01). Similarly, static stretching also decreased eccentric and concentric hamstring muscle strength at both the 60°/s and 180°/s test speeds(P < 0.01). On the other hand, when the functional H/Q strength ratios were taken into consideration, the pre-intervention values were not significant different between the groups both during the entire and end range of knee extension(P > 0.05). Furthermore, the functional H/Q strength ratios exhibited no significant alterations during the entire and end ranges of knee extension both in the static stretching or the control intervention(P > 0.05). CONCLUSION: According to our results, static stretching routine does not influence functional H/Q ratio. Athletes can confidently perform static stretching during their warm-up routines.展开更多
Purpose: Stretching exercise and gymnastics both have beneficial effects, such as improvement of autonomic nervous system activity and mood. Additionally, studies on the effects of exercise on cognitive function have ...Purpose: Stretching exercise and gymnastics both have beneficial effects, such as improvement of autonomic nervous system activity and mood. Additionally, studies on the effects of exercise on cognitive function have been conducted covering a wide range of age groups and have attracted much attention. However, conventional studies have set up programs with implementation times of 20 to 30 minutes. Therefore, shorter stretching programs are needed in order to fit them more easily into one’s free time. We examined the effects of a short 7-minute stretching gymnastics regime on the autonomic nervous system activity and cognitive function in 21 healthy participants. Methods: In this study, the participants performed a 10-minute cognitive task, followed by either Stretch Well Gymnastics, Stretch Band Gymnastics, or Radio Gymnastics sessions on different days. The participants then performed the cognitive task again. Heart rate was measured continuously throughout the experiment and we analyzed the heart rate variability. The cognitive tasks completed by all of the participants were evaluated for inhibitory control and cognitive flexibility. Results: A significant increase was shown in the sympathetic nerve activity during the Stretch Well Gymnastics, compared to the Radio Gymnastics and Stretch Band Gymnastics. Parasympathetic nerve levels were significantly increased after the gymnastics, compared to during the gymnastics, although there were no significant differences between any of the tasks. Additionally, in both the Stroop task and the number-Letter task, reaction times were faster in all of the sessions. In particular, the Stroop task showed the highest values for the Radio Gymnastics sessions, with marginally significantly lower scores for the Stretch Well Gymnastics sessions. Conclusion: The results showed that these heart rate variability responses supported the effects of autonomic activity associated with conventional low-intensity exercise. Additionally, stretching gymnastics for less than 10 minutes showed a positive effect on inhibitory function and cognitive flexibility.展开更多
The effect of radiation on the flow over a stretching plate of an optically thin gray, viscous and incompressible fluid is studied. The fluid viscosity is assumed to vary as an inverse linear function of the temperatu...The effect of radiation on the flow over a stretching plate of an optically thin gray, viscous and incompressible fluid is studied. The fluid viscosity is assumed to vary as an inverse linear function of the temperature. The partial differential equations (PDEs) and their boundary conditions, describing the problem under consideration, are dimensionalized and the numerical solution is obtained by using the finite volume discretization methodology which is suitable for fluid mechanics applications. The numerical results for the velocity and temperature profiles are shown for different dimensionless parameters entering the problem under consideration, such as the temperature parameter, θr, the radiation parameter, S, and the Prandtl number, Pr. The numerical results indicate a strong influence of these parameters on the non-dimensional velocity and temperature profiles in the boundary layer.展开更多
文摘AIM: To evaluate if static stretching influences peak and end-range functional hamstring-to-quadriceps(H/Q) strength ratios in elite women athletes. METHODS: Eleven healthy female athletes in an elite competitive level participated to the study. All the participants fulfilled the static stretching or non-stretching(control) intervention protocol in a randomized design on different days. Two static unassisted stretching exercises, one in standing and one in sitting position, were used to stretch both the hamstring and quadriceps muscles during these protocols. The total time for the static stretching was 6 ± 1 min. The isokinetic peak torque measurements for the hamstring and quadriceps muscles in eccentric and concentric modes and the calculations for the functional H/Q strength ratios at angular velocities of 60°/s and 180°/s were made before(pre) and after(post) the control or stretching intervention. The strength measurements and functional strength ratio calculations were based during the entire- and end-range of knee extension.RESULTS: The pre-test scores for quadriceps and hamstring peak torque and end range values were not significantly different between the groups(P > 0.05). Subsequently, although the control group did notexhibit significant changes in quadriceps and hamstring muscle strength(P > 0.05), static stretching decreased eccentric and concentric quadriceps muscle strength at both the 60°/s and 180°/s test speeds(P < 0.01). Similarly, static stretching also decreased eccentric and concentric hamstring muscle strength at both the 60°/s and 180°/s test speeds(P < 0.01). On the other hand, when the functional H/Q strength ratios were taken into consideration, the pre-intervention values were not significant different between the groups both during the entire and end range of knee extension(P > 0.05). Furthermore, the functional H/Q strength ratios exhibited no significant alterations during the entire and end ranges of knee extension both in the static stretching or the control intervention(P > 0.05). CONCLUSION: According to our results, static stretching routine does not influence functional H/Q ratio. Athletes can confidently perform static stretching during their warm-up routines.
文摘Purpose: Stretching exercise and gymnastics both have beneficial effects, such as improvement of autonomic nervous system activity and mood. Additionally, studies on the effects of exercise on cognitive function have been conducted covering a wide range of age groups and have attracted much attention. However, conventional studies have set up programs with implementation times of 20 to 30 minutes. Therefore, shorter stretching programs are needed in order to fit them more easily into one’s free time. We examined the effects of a short 7-minute stretching gymnastics regime on the autonomic nervous system activity and cognitive function in 21 healthy participants. Methods: In this study, the participants performed a 10-minute cognitive task, followed by either Stretch Well Gymnastics, Stretch Band Gymnastics, or Radio Gymnastics sessions on different days. The participants then performed the cognitive task again. Heart rate was measured continuously throughout the experiment and we analyzed the heart rate variability. The cognitive tasks completed by all of the participants were evaluated for inhibitory control and cognitive flexibility. Results: A significant increase was shown in the sympathetic nerve activity during the Stretch Well Gymnastics, compared to the Radio Gymnastics and Stretch Band Gymnastics. Parasympathetic nerve levels were significantly increased after the gymnastics, compared to during the gymnastics, although there were no significant differences between any of the tasks. Additionally, in both the Stroop task and the number-Letter task, reaction times were faster in all of the sessions. In particular, the Stroop task showed the highest values for the Radio Gymnastics sessions, with marginally significantly lower scores for the Stretch Well Gymnastics sessions. Conclusion: The results showed that these heart rate variability responses supported the effects of autonomic activity associated with conventional low-intensity exercise. Additionally, stretching gymnastics for less than 10 minutes showed a positive effect on inhibitory function and cognitive flexibility.
文摘The effect of radiation on the flow over a stretching plate of an optically thin gray, viscous and incompressible fluid is studied. The fluid viscosity is assumed to vary as an inverse linear function of the temperature. The partial differential equations (PDEs) and their boundary conditions, describing the problem under consideration, are dimensionalized and the numerical solution is obtained by using the finite volume discretization methodology which is suitable for fluid mechanics applications. The numerical results for the velocity and temperature profiles are shown for different dimensionless parameters entering the problem under consideration, such as the temperature parameter, θr, the radiation parameter, S, and the Prandtl number, Pr. The numerical results indicate a strong influence of these parameters on the non-dimensional velocity and temperature profiles in the boundary layer.
