MethodThe study was a cross sectional survey, sampling the whole group aged 80 years and above, who live in Jiajian country, Bama County.
方法截断面调查，整群抽取巴马县甲篆乡80岁以上老人。
Secondly, the whole vehicle rigid-flexible coupling modal equipped with the frame is built and analyzed to obtain the load histories through driving on cross-country path and strengthen-road .
其次建立该整车的刚柔耦合动力学模型，并进行越野路、强化路等路面的整车动力学仿真，得到相应的模态位移时间历程；
The major findings are as follows: 1, cross-country skiing as a kind of speed and skill projects, training and competition in the whole process, the right knee strength and flexibility are demanding.
研究结果如下：1、越野滑雪作为一种速度和技能性项目，在整个训练和比赛过程中，对膝关节的力量和柔韧性要求很高。
The major findings are as follows: 1, cross-country skiing as a kind of speed and skill projects, training and competition in the whole process, the right knee strength and flexibility are demanding.
研究结果如下：1、越野滑雪作为一种速度和技能性项目，在整个训练和比赛过程中，对膝关节的力量和柔韧性要求很高。
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