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.     

Thermoneutral immersion exercise accelerates heart rate recovery: A potential novel training modality

This study compared heart rate recovery (HRR) after incremental maximal exercise performed at the same external power output (P_ext) on dry land ergocycle (DE) vs. immersible ergocycle (IE). Fifteen young healthy participants (30?±?7 years, 13 men and 2 women) performed incremental maximal exercise tests on DE and on IE. The initial P_ext on DE was 25?W and was increased by 25?W/min at a pedalling cadence between 60 and 80?rpm, while during IE immersion at chest level in thermoneutral water (30°C), the initial P_ext deployment was at a cadence of 40?rpm which was increased by 10?rpm until 70?rpm and thereafter by 5?rpm until exhaustion. Gas exchange and heart rate (HR) were measured continuously during exercise and recovery for 5?min. Maximal HR (DE: 176?±?15 vs. IE 169?±?12?bpm) reached by the subjects in the two conditions did not differ (P?>?.05). Parasympathetic reactivation parameters (ΔHR from 10 to 300?s) were compared during the DE and IE HR recovery recordings. During the IE recovery, parasympathetic reactivation in the early phase was more predominant (HRR at Δ10–Δ60?s, P?<?.05), but similar in the late phase (HRR at Δ120–Δ300?s, P?>?.05) when compared to the DE condition. In conclusion, incremental maximal IE exercise at chest level immersion in thermoneutral water accelerates the early phase parasympathetic reactivation compared to DE in healthy young participants.     

短期力量练习对老年人肌肉力量和身体功能的影响

为了充分证实不同的力量练习计划对老年人体质健康影响的效果,通过对比高速率的变阻训练(HV)、由慢到快速率的等阻训练(CT)以及高速率的变阻练习与身体功能练习相结合(CB)的3种不同的短期力量练习计划对老年人的肌肉功能和身体活动能力的影响进行了实证性研究。研究结果显示:与控制组(CO)相比,HV组、CT组以及CB组的肌肉力量都有显著性的提高,而CO的力量呈轻微的下降趋势;每周两次的HV练习在提高力量和爆发性身体功能时,要优于CT和CB组;与HV和CT组相比,CB组对增加老年人的力量也是有效的,这个结果对于那些不愿意或不能频繁参加力量练习的老年人是一个重要提示。     

花剑运动员技术训练与模拟比赛训练课的心率特征分析

以福建省花剑运动员为研究对象,对花剑运动员的技术训练课和模拟比赛课全程进行实时心率测试分析,认为模拟比赛训练课能达到实战训练强度的要求,有利于高水平运动员提高技战术的实战能力,技术训练课负荷强度较低,适合于技术水平较低的运动员,应根据不同技术水平的运动员合理安排技术训练课与模拟比赛训练课的比重。     

幼儿乳酸阈值及无氧阈心率的初步研究

对33名幼儿乳酸阈及其心率值进行测定,结果显示:3～5岁幼儿AT时血乳酸水平显著低于成人及青少年;幼儿亚极量强度运动后乳酸峰值大多出现在负荷后1min,反映了幼儿机体代谢的特异性.此实验结果可为幼儿有关生理机能和能量代谢的研究提供参数,所测得的乳酸阈心率值将为幼儿健身、减肥、增高等运动处方中运动强度控制提供科学依据.     

间歇性低氧训练对气体代谢影响的实验研究

间歇性低氧训练是 90年代初在俄罗斯率先发展的一种新的科学训练方法 ,在运动训练中发挥了积极有效的作用。笔者通过人体实验 ,探讨间歇性低氧训练对气体代谢及运动耐力的影响 ,为该训练方法在我国的推广应用提供必要的理论 ,实践依据。实验结果表明 :间歇性低氧训练可有效提高呼吸系统功能 ,提高气体代谢效率 ,促进运动能力提高 ,是一种科学有效的训练方法     

Biomechanical differences of arm swing countermovement jumps on sand and rigid surface performed by elite beach volleyball players

The purpose of this study was to investigate the possible arm swing effect on the biomechanical parameters of vertical counter movement jump due to differences of the compliance of the take-off surface. Fifteen elite male beach-volleyball players (26.2 ± 5.9 years; 1.87 ± 0.05 m; 83.4 ± 6.0 kg; mean ± standard deviation, respectively) performed counter movement jumps on sand and on a rigid surface with and without an arm swing. Results showed significant (p < .05) surface effects on the jump height, the ankle joint angle at the lowest height of the body center of mass and the ankle angular velocity. Also, significant arm swing effects were found on jump height, maximum power output, temporal parameters, range of motion and angular velocity of the hip. These findings could be attributed to the instability of the sand, which resulted in reduced peak power output due to the differences of body configuration at the lowest body position and lower limb joints’ range of motion. The combined effect of the backward arm swing and the recoil of the sand that resulted in decreased resistance at ankle plantar flexion should be controlled at the preparation of selected jumping tasks in beach-volleyball.     

论背越式跳高摆动腿动作的技术原理

依据背越式跳高技术的动作方法，运用运动生物力学的基本理论，从运动学和动力学的角度，对背越式跳高技术中，摆动腿在起跳阶段的3个不同时段内的技术原理进行了分析与讨论。     

对不同等级男子110m跨栏运动员速度利用率及绝对速度的比较分析

采用查阅献、问卷调查的方法，采集国内外部分运动员的技术数据，从跨栏运动员速度利用率及绝对速度的角度，分析国内外运动员的跨栏技术水平、跨栏速度以及跨栏运动成绩，发现不同运动技术等级的跨栏运动员的速度利用率不是等同的，跨栏技术与速度存在着各种差距。要利用跨栏跑的速度利用率，处理好跨栏跑中的速度与技术的关系，既要提高跨栏运动员的技术水平，又要发展跨栏运动员的绝对速度，以此促进跨栏运动员成绩的提高，发展我国跨栏运动的整体水平。     

赛艇运动员稳态心率的研究

探讨了赛艇运动员在赛艇测功仪上作中等强度匀速运动时的稳态心率。