以下文章内容都属实，值得一看，只是带有作者微妙立场
In Search of the Quad Axel
http://www.iceskatingintnl.com/archive/features/QuadAxel.htmGeorge S. Rossano针对4A、4Lutz建模后，对4A进行深入的数据分析及探讨可行性。
他认为4A很难跳出，因为他认为现在pre-rotation、under-rotation的问题泛滥，绝大部分选手连idealized jumps 、textbook jumps都跳不出了，更遑论4A
节录文章片段
We call them idealized jumps because in the real world most skatersexecute jumps with technique different from the ideal descriptions, and fortriple Axel and above very different.
Further, certain jumps even when executed in textbook fashion never havehad an integer number of rotations. Loops and Salchow, for example, havealways been executed with about one-quarter rotation short of integer rotation,as the skaters jump not only upwards, but also somewhat to the side for thesejumps.
大意：
1.许多3A执行不标准
2 Loops和Salchow带有些许天然的pre-rotation，即使是textbook jumps都无可避免
Looking at ISU competition specifically, many skaters have up toone-half rotation missing on the takeoff and up to one quarter rotation on thelanding, and ISU Technical Panels will call those jumps fully rotated, giving fullbase value.
This means a full value jump can often be missing a total of three-quartersof a rotation for toe loop through Lutz, and one-half for Axels (Axels tend tohave no more than one-quarter missing rotation on the takeoff, one-third at worst).
This is the method the Russian wunderkind (and others) now use to getcredit for triple Axel and quads. Most Russian girls do it the same way,and as the most successful ones are all taught by the same coach, it appearsthis is the technique they are taught, and not a coincidence, knowing the ISUwill not penalize them.
大意：
因为ISU不罚，3A、4Lutz的pre-rotation、under-rotation满天飞，尤其是俄国女单选手
Given the skill level needed to achieve a fully rotated quad Axel (Table2), it seems unlikely we will ever see one of these. It would probably requirea revolutionary improvement in technique, training and/or equipment for askater to outperform the assumptions built into Table 2, particular the time ittakes to get over the right side and pulled in; i.e., an air rotationefficiency approaching 0.9. A dynamical model of a true quadAxel can be found here. A dynamical model of a true quadLutz can be found here.
大意：
考虑到要真正做到没有pre-rotation、under-rotation的4A很难，除非要能突破现阶段的技术、训练方式及装备，不然真正的4A很难实现。
这篇我还有话要说，只是先不在这里谈
），以下开始介绍一些不错看的内容吧。
