Effects of official youth taekwondo competitions on jump and strength performance

Abstract

The aim of this study was to investigate differences in athletes’ (7 females, 10 males) motor performances (countermovement jump and handgrip) before and after official youth (13–14 years) taekwondo matches. Exercise load was evaluated by means of the heart rate responses during the match. Independent of round and gender, during the competitions mean heart rate was 187 beats·min^?1 (s=11). During the match, the frequency of heart rate responses above 85% of an individual's maximum heart rate was 77% (s=27). Jump performances showed differences for gender (P=0.044; ES = 0.47) and its interaction with session (P=0.045; ES = 0.49). Female athletes’ post-match countermovement performances were no different from their pre-match performances (pre and post: 22 cm, s=2), whereas male athletes post-match performances (28 cm, s=6) were better than their pre-match performances (25 cm, s=6). Handgrip performances related to the body mass of the athletes showed main effects for session (P=0.017; ES = 0.20) and for gender (P=0.026; ES = 0.47), with no significant interaction. Male athletes showed higher handgrip values (5.8 N·kg^?1, s=0.6) than their female counterparts (5.1 N·kg^?1, s=0.7). For absolute grip strength performances, values were higher pre-match (290.3 N, s=61.4) than post-match (272.4 N, s = 58.3). The heart rate responses indicate that official youth taekwondo competition imposes a high load on athletes. In particular, post-match decreases in isometric grip strength suggest that coaches should better prepare their very young athletes to prevent reductions in muscle force during fighting. Considering that lower limb power remained unaffected or increased depending on gender, further research in this area is strongly recommended.     

Hamstring rate of torque development is more affected than maximal voluntary contraction after a professional soccer match

Abstract

Match-induced fatigue of knee muscle strength and agonist-antagonist strength-ratios may affect both performance and risk of injury in soccer players. Once explosive tasks are imperative in soccer as well as hamstring strain injuries occur during high-velocity moments, rapid force capacity of this muscle group is especially important. This study evaluated the effect of match-induced fatigue on knee muscle strength and strength-ratio parameters after a single professional soccer match. Male professional soccer players (n?=?16; 24.2?±?3.9 years) were tested before and after a soccer match (56.2?±?22.6?min of playing) for knee flexors (hamstring) and extensors (quadriceps) isometric peak torque (MVC) and rate of torque development (RTD) – as well as the hamstring-to-quadriceps ratio (H:Q) – at 30° of knee flexion. Knee injuries often occur at this joint angle, which is common in sprinting, pivoting, sidecutting, and jumping. Match-induced fatigue caused a left shift in the knee extensors torque-time curve with no significant change in both early (i.e. 0–50?ms) and late (i.e. 0–200?ms) RTD, and a right shift in the knee flexors torque-time curve with a decrease in early RTD (～16%, p?=?.029) and late RTD (～11%, p?=?.011). Knee extensors and knee flexors peak torque remained unchanged (p?>?.05). Early RTD H:Q decreased by～24% (p?=?.027), while late RTD H:Q and MVC H:Q remained unchanged (p?>?.05). In conclusion, match-induced fatigue impaired the ability to rapidly produce force at an angle where injuries are most susceptible to occur. Important information is missed if only the traditional H:Q is considered.     

高中生野外远足活动距离和时间问题的研究

在建立高中三年级男、女性能量系统和野外远足日生活,两个活动模型的基础上,运用生理学,生物力学和营养学理论对高中三年级学生野外远足的合适距离和合理的净运动时间进行了分析。认为高中三年级学生野外远足合适距离为２０—２５公里,步行时间在４—５小时。     

影响中国女子冰壶队投壶成功率因素分析

本文运用文献资料法、录像观察法和数理统计法,对影响中国女子冰壶队投壶成功率进行分析,结果表明：技战术水平高低是关键因素;心理素质是另一主要因素;魔鬼赛程是影响投壶成功率的另一障碍因素。     

健身俱乐部不同消费动机会员服务满意度调查

运用问卷调查法、数理统计法对健身俱乐部不同消费动机会员服务满意度进行调查,结果表明:生存需要型会员与娱乐享受型会员的消费行为特征存在差别,对健身服务质量的诉求明显不同。针对不同动机类型会员提出了侧重点不同的服务营销策略,为健身俱乐部的经营提供参考。     

高原运动员在次高原比赛期间静息心率及体重变化状况的分析

本文通过青海业余运动员云南昆明比赛期间晨静息心率、晨空腹体重和问卷调查的分析,发现：高原地区运动员即使向高原地区较低海拔移动较少的高度,也会产生有利于心血管方面的影响,运动员本体感觉好于原居住地;返回原居住地后,缺氧对机体也有刺激作用;在身体机能的变化中,机体对心血管系统的变化更为敏感,     

2010年世界女排大奖赛总决赛接发球到位率及阵型的比较研究

通过现场拍摄2010年世界女排大奖赛总决赛的15场比赛,对各队接发球到位率及阵型进行研究,结果表明:接发球到位率方面,中国女排偏低,且失误率最高;巴西女排到位率最高,且失误率最低;日本女排到位率较高且防反能力较强。接发球阵型方面,中日女排人员配备相同,但负责接一传的主攻前后位置不一,使得日本队自由人处于后排中间位置接发球轮次比中国队多1轮,且阵型分布相对合理。     

4周下肢间歇负压干预对优秀赛艇运动员心率变异性和儿茶酚胺的影响

目的探讨下肢间歇负压干预对赛艇运动员心率变异性(HRV)相关指标和儿茶酚胺的影响。方法将国家赛艇队的14名运动员分为试验组和对照组,试验组运动员每周用间歇负压干预5 d,持续4周,对照组无其他干预方式。试验期间均对2组运动员进行HRV相关指标和儿茶酚胺的测试。结果试验前2组运动员各指标均无统计学差异。开始干预后2组的变化如下:①在时域指标中,试验组正常窦性R-R间期标准差(SDNN)在第3周时高于对照组(P<0.05)。②在频域指标中,试验组高频(HF)值在第2周和第3周时高于对照组(P<0.05),而其高频与低频比(LF/HF)在第1、3和4周时低于对照组(P<0.05)。③2组儿茶酚胺组内、组间比较均无统计学差异,但试验组儿茶酚胺下降程度比对照组高。结论 4周的间歇负压干预对运动员自主神经系统功能的恢复有明显促进作用,对儿茶酚胺的分泌也具有抑制趋势;这有利于降低运动员心脏负荷,促进运动后的生理恢复。     

世界男子排球强队失分环节的技术统计研究

通过对2000年奥运会、2002年世界男子排球锦标赛比赛技术统计资料的研究,进行分 类归纳并建立数学模型,然后对比分析,找出世界男子排球强队在失分率方面的统计学特征,供 各级运动队用来指导训练和比赛。     

老年体育与人口健康

根据研究表明,我国体育人口年龄结构呈现“马鞍型”分布,老年人口是体育人口的重要组成部分。同时,我国人口健康风险人群不断增加,老年人所占比重高;老年失能人口绝对数量大,健康预期寿命较低,女性的程度较男性更为明显,而体育锻炼作为促进健康的重要作用已经得到了普遍的认同,本文通过对2000年进行的“中国城乡老年人口状况一次性抽样调查”数据进行分析,反映目前我国老年人口参与体育锻炼的现状,对老年人参与体育锻炼方式提出建议,借以提高老年人整体的健康素质。