Background:Mathematical models propose leg length as a limiting factor in determining the maximum walking velocity.This study evaluated the effectiveness of a leg length-based model in predicting maximum walking veloc...Background:Mathematical models propose leg length as a limiting factor in determining the maximum walking velocity.This study evaluated the effectiveness of a leg length-based model in predicting maximum walking velocity in an applied race walking situation,by comparing experienced and novice race walkers during conditions where strictly no flight time(FT)was permitted and in simulated competition conditions(i.e.,FT<40 ms).Methods:Thirty-four participants(18 experienced and l6 novice race walkers)were recruited for this investigation.An Optojump Next system(8 m)was used to determine walking velocity,step frequency,step length,ground contact time,and FT during race walking over a range of velocities.Comparisons were made between novice and experienced participants in predicted maximum velocity and actual velocities achieved with no flight and velocities with FT<40 ms.The technical effectiveness of the participants was assessed using the ratio of maximum velocity to predicted velocity.Results:In novices,no significant difference was found between predicted and maximum walking speeds without FT but there was a small 5.8%gain in maximum speed when FT≤40 ms.In experienced race walkers,there was a significant reduction in maximum walking speed compared with predicted maximum(p<0.01)and a 11.7%gain in maximum walking speed with FT<40 ms.Conclusion:Leg length was a good predictor of maximal walking velocity in novice walkers but not a good predictor of maximum walking speed in well-trained walkers who appear to have optimised their walking technique to make use of non-visible flight periods of less than 40 ms.The gain in velocity above predicted maximum may be a useful index of race walking proficiency.展开更多
Kr1基因是小麦远缘杂交不亲和的主效基因。为探究Kr1基因的特性,根据已公布的Kr1基因c DNA部分序列,采用染色体步移(Genome Walking)和c DNA末端快速扩增技术(rapid amplification of c DNA ends,RACE)克隆小麦显性Kr1基因和隐性kr1基因...Kr1基因是小麦远缘杂交不亲和的主效基因。为探究Kr1基因的特性,根据已公布的Kr1基因c DNA部分序列,采用染色体步移(Genome Walking)和c DNA末端快速扩增技术(rapid amplification of c DNA ends,RACE)克隆小麦显性Kr1基因和隐性kr1基因,并进行序列分析。结果表明,小麦Kr1基因全长4 006 bp,含有4个外显子和3个内含子,ORF全长1 671 bp,编码557个氨基酸,可形成一条完整肽链,有基因活性,Kr1蛋白三级结构与植物S位点受体激酶具有较高的相似性。kr1基因全长3 945bp,第3、第4外显子中因含有大量终止密码子,不能通读,表明kr1基因无基因活性。同时对小麦×黑麦、小麦×球茎大麦、小麦×玉米等不同远缘杂交系统的亲和性差异进行探讨,认为Kr1基因在小麦×玉米中失活可能与玉米转座子的插入有关。本研究结果为进一步阐明Kr1基因的功能及其作用机制奠定了基础。展开更多
文摘Background:Mathematical models propose leg length as a limiting factor in determining the maximum walking velocity.This study evaluated the effectiveness of a leg length-based model in predicting maximum walking velocity in an applied race walking situation,by comparing experienced and novice race walkers during conditions where strictly no flight time(FT)was permitted and in simulated competition conditions(i.e.,FT<40 ms).Methods:Thirty-four participants(18 experienced and l6 novice race walkers)were recruited for this investigation.An Optojump Next system(8 m)was used to determine walking velocity,step frequency,step length,ground contact time,and FT during race walking over a range of velocities.Comparisons were made between novice and experienced participants in predicted maximum velocity and actual velocities achieved with no flight and velocities with FT<40 ms.The technical effectiveness of the participants was assessed using the ratio of maximum velocity to predicted velocity.Results:In novices,no significant difference was found between predicted and maximum walking speeds without FT but there was a small 5.8%gain in maximum speed when FT≤40 ms.In experienced race walkers,there was a significant reduction in maximum walking speed compared with predicted maximum(p<0.01)and a 11.7%gain in maximum walking speed with FT<40 ms.Conclusion:Leg length was a good predictor of maximal walking velocity in novice walkers but not a good predictor of maximum walking speed in well-trained walkers who appear to have optimised their walking technique to make use of non-visible flight periods of less than 40 ms.The gain in velocity above predicted maximum may be a useful index of race walking proficiency.
文摘Kr1基因是小麦远缘杂交不亲和的主效基因。为探究Kr1基因的特性,根据已公布的Kr1基因c DNA部分序列,采用染色体步移(Genome Walking)和c DNA末端快速扩增技术(rapid amplification of c DNA ends,RACE)克隆小麦显性Kr1基因和隐性kr1基因,并进行序列分析。结果表明,小麦Kr1基因全长4 006 bp,含有4个外显子和3个内含子,ORF全长1 671 bp,编码557个氨基酸,可形成一条完整肽链,有基因活性,Kr1蛋白三级结构与植物S位点受体激酶具有较高的相似性。kr1基因全长3 945bp,第3、第4外显子中因含有大量终止密码子,不能通读,表明kr1基因无基因活性。同时对小麦×黑麦、小麦×球茎大麦、小麦×玉米等不同远缘杂交系统的亲和性差异进行探讨,认为Kr1基因在小麦×玉米中失活可能与玉米转座子的插入有关。本研究结果为进一步阐明Kr1基因的功能及其作用机制奠定了基础。
