Background： Preventing anterior cruciate ligament（ACL） injuries is very important for athletes, and dynamic knee valgus is considered a risk factor for non-contact ACL injury. However, little is known about whether...Background： Preventing anterior cruciate ligament（ACL） injuries is very important for athletes, and dynamic knee valgus is considered a risk factor for non-contact ACL injury. However, little is known about whether the functions of the hip abductor and rear-foot increase dynamic knee valgus. A two-dimensional（2D） video-based screening test focused on hip abductor and rear-foot functions among factors involved in dynamic knee valgus. The present study determined associations between hip and rear-foot dynamic alignment and dynamic knee valgus.Methods： This cross-sectional study recruited 130 female basketball players（258 legs） from nine high-school teams. The players performed single-leg squats and single-leg drop landings to provide knee-in（KID） and hip-out（HOD） distances on 2D video images. Hip and rear-foot dynamic alignment was evaluated using a dynamic Trendelenburg test（DTT） and a dynamic heel-floor test（HFT）.Results： The Chi-square test revealed no significant difference in the prevalence of DTT-positivity between single-leg squats（28.7%） and singleleg drop landings（23.3%）. The prevalence of HFT-positivity was significantly greater during landings（51.4%） than during single-leg squats（31.0%, p 〈 0.01）. The KID values for both single-leg squats and single-leg drop landings were greater in the DTT-positive than in the DTTnegative group（15.1 5.4 cm and 20.2 7.5 cm, p 〈 0.001）. The HOD values were similarly greater in the DTT-positive group（15.2 1.9 cm and 17.6 2.8 cm, p 〈 0.001）. The KID values for both single-leg squats and single-leg drop landings were greater in the HFT-positive than in the HFT-negative group（12.2 5.1 cm, p 〈 0.01; 14.7 7.2 cm, p 〈 0.001）, whereas HOD values for these tasks did not significantly differ between the two groups.Conclusion： Dynamic hip mal-alignment might be associated with both greater KID and HOD, whereas rear-foot eversion is associated only with greater KID. Hip abductor and rear-foot dysfunction are important factors for dynamic knee valgus and thus evaluating DTT and HFT will help to prevent dynamic knee valgus.展开更多
We investigate theoretically the temperature effects on the evolutions of both bright and dark screening spatial solitons in biased two-photon photorefractive crystals.For a stable bright or dark two-photon screening ...We investigate theoretically the temperature effects on the evolutions of both bright and dark screening spatial solitons in biased two-photon photorefractive crystals.For a stable bright or dark two-photon screening spatial soliton originally formed in a crystal at a given temperature,when the crystal temperature changes,it will evolve into another stable screening soliton if the temperature change is quite small,while it will become unstable or break down if the temperature change is large enough.The spatial shape of a stable two-photon screening spatial soliton can be changed by appropriately adjusting the crystal temperature.展开更多
文摘Background： Preventing anterior cruciate ligament（ACL） injuries is very important for athletes, and dynamic knee valgus is considered a risk factor for non-contact ACL injury. However, little is known about whether the functions of the hip abductor and rear-foot increase dynamic knee valgus. A two-dimensional（2D） video-based screening test focused on hip abductor and rear-foot functions among factors involved in dynamic knee valgus. The present study determined associations between hip and rear-foot dynamic alignment and dynamic knee valgus.Methods： This cross-sectional study recruited 130 female basketball players（258 legs） from nine high-school teams. The players performed single-leg squats and single-leg drop landings to provide knee-in（KID） and hip-out（HOD） distances on 2D video images. Hip and rear-foot dynamic alignment was evaluated using a dynamic Trendelenburg test（DTT） and a dynamic heel-floor test（HFT）.Results： The Chi-square test revealed no significant difference in the prevalence of DTT-positivity between single-leg squats（28.7%） and singleleg drop landings（23.3%）. The prevalence of HFT-positivity was significantly greater during landings（51.4%） than during single-leg squats（31.0%, p 〈 0.01）. The KID values for both single-leg squats and single-leg drop landings were greater in the DTT-positive than in the DTTnegative group（15.1 5.4 cm and 20.2 7.5 cm, p 〈 0.001）. The HOD values were similarly greater in the DTT-positive group（15.2 1.9 cm and 17.6 2.8 cm, p 〈 0.001）. The KID values for both single-leg squats and single-leg drop landings were greater in the HFT-positive than in the HFT-negative group（12.2 5.1 cm, p 〈 0.01; 14.7 7.2 cm, p 〈 0.001）, whereas HOD values for these tasks did not significantly differ between the two groups.Conclusion： Dynamic hip mal-alignment might be associated with both greater KID and HOD, whereas rear-foot eversion is associated only with greater KID. Hip abductor and rear-foot dysfunction are important factors for dynamic knee valgus and thus evaluating DTT and HFT will help to prevent dynamic knee valgus.
基金supported by the Science and Technology Development Foundation of Higher Education of Shanxi Province,China (No.200611042)
文摘We investigate theoretically the temperature effects on the evolutions of both bright and dark screening spatial solitons in biased two-photon photorefractive crystals.For a stable bright or dark two-photon screening spatial soliton originally formed in a crystal at a given temperature,when the crystal temperature changes,it will evolve into another stable screening soliton if the temperature change is quite small,while it will become unstable or break down if the temperature change is large enough.The spatial shape of a stable two-photon screening spatial soliton can be changed by appropriately adjusting the crystal temperature.
