Upper and lower limb loading during weight-bearing activity in children: reaction forces and influence of body weight

Weight bearing (WB) activity is important for healthy skeletal development. The magnitude of loading during WB activities, especially upper limb impacts, has yet to be quantified in children. This study quantifies ground reaction forces (GRF) experienced by children performing WB activities and examines the contribution of body weight (BW) to GRF. Fifty children, aged 8–12 were recruited (34 males). GRF were measured using force plates during 20 upper and lower limb activities (such as landing on the feet and hands). Sex differences in GRF and associations between peak force and BW were examined using independent sample t-tests and linear regressions (p < 0.05), respectively. Lower limb GRF varied from 2-6x BW with no significant sex differences. GRF during upper limb activities varied from 1/3–1.7x BW with males experiencing significantly greater GRF for 25% of activities. BW was significantly associated with peak force in almost all activities; however, GRF variation explained by BW was wide-ranging across activities and not dependent on limb or activity type (static vs dynamic). Therefore, factors other than BW, such as technique, may be important in determining forces experienced by children performing WB activity and should be considered when choosing activities for WB activity interventions.     

我国高中学生学业成就与家庭背景关系的实证研究

本文通过2003年对10个城市40所高中在校生的问卷调查,分析普通高中学生学业成就与家庭背景之间的关系。结果显示学生学业成就与父亲职业、文化程度和家庭经济收入均无显著性差异。     

长江上游赤水河示范区水生态修复的成效与挑战

“深入开展绿色发展示范，推进赤水河流域生态环境保护”是《中华人民共和国国民经济和社会发展第十四个五年规划和2035年远景目标纲要》提出的重大决策部署。加强赤水河水生态环境保护对于维系长江上游鱼类多样性、促进区域高质量发展、开创生态文明和美丽中国建设新局面均具有示范和引领作用。文章分析了赤水河在长江上游的生态功能，阐述了近年来赤水河实施的全面禁渔、支流小水电清理整改等保护修复措施的成效，从流域整体保护与系统修复角度提出了进一步加强赤水河水生态保护修复的对策建议。