System approach to games and competitive playing

Abstract

The force enhancement of muscle twitch contraction after a maximal voluntary contraction (MVC) has been defined as post-activation potentiation. However, the effects of post-activation potentiation on ballistic movements have not been studied extensively, or the underlying neurophysiologycal mechanism. In the current study, we examined post-activation potentiation and spinal H-reflex excitability in the soleus muscle. Mechanical power during explosive ballistic plantar flexions was measured in 14 males before and after 5 s, 4 min, and 10 min of isometric conditioning (EPF_pre, EPF_5s, EPF_4min, EPF_10min, respectively). Four sessions corresponding to four different protocols of isometric conditioning were conducted. The protocols were different in the intensity (10% vs. 100% of MVC) and duration (7 vs. 10 s) of the isometric conditioning. The results showed a significant enhancement in mechanical power in EPF_4min compared with EPF_pre, only when the isometric conditioning was performed at 100% of MVC for 10 s. No significant changes were observed in the H-related parameters (e.g amplitude, threshold, H/M ratio) after the isometric conditioning. Our results show that to obtain a post-activation potentiation during explosive ballistic movements, the intensity and duration of the isometric conditioning must be controlled. Moreover, the improvement in mechanical power is not related to spinal H-reflex excitability.     

对青少年越野滑雪运动员力量和耐力训练的思考

我国运动员在越野滑雪这一体能主导类项目中不具优势,其耐力素质较差,难于在比赛后程及上坡阶段保持充沛的体力;力量素质较差常导致动作技术变形进而影响运动成绩;且缺乏连续参加大型比赛的素质。我国越野滑雪运动员的力量和耐力素质亟待加强,而其训练敏感期在青少年时期,故应充分考虑青少年越野滑雪运动员的生理特点、运动技能形成的年龄规律、身体素质发展的敏感期等因素,制定科学合理的长期训练计划、强化力量和耐力素质训练,以期为我国越野滑雪的发展献计献策。     

Physical structure of winter sports athletes

A review of the results concerning the body size, growth, maturation, shape, composition, and strength of ice hockey players, cross-country skiers, alpine skiers, ski jumpers and Nordic combined skiers is presented. The comparisons of the results in body height, weight, somatotypes, percent fat, LBM and hand grip from various authors are made. Also the differences between ice hockey players and skiers of all disciplines are shown. The review covers all the available results. It may be concluded that the elite athletes in each studied sport form a highly select group which has, from the biomechanical point of view, the best physical structure for their sport discipline.     

Muscle activation characteristics in cross-country skiers with a history of anterior compartment pain

A large proportion of elite cross-country skiers suffer from chronic anterior compartment syndrome (CACS). This study used surface electromyograms (EMGs) to investigate whether differences existed in the activation characteristics of the tibialis anterior muscle between elite cross-country skiers with a history of anterior compartment pain (symptomatic group) and a pain-free control group. Based on self-reported pain symptoms, twelve young, national-level cross-country ski athletes were assigned to a symptomatic group (N = 5), a control group (N = 4), or analyzed individually if their diagnosis was not certain (N = 3). During skating, EMGs were recorded on five lower leg muscles. The relative increase in EMG power per step when increasing the effort level of skating was larger in the symptomatic group than in the control group for tibialis anterior (143 ± 12% vs. 125 ± 23%; Cohen's d = 1.17), peroneus longus (123 ± 24% vs. 107 ± 6%; d = 0.91), and gastrocnemius lateralis (167 ± 51% vs. 117 ± 12%; d = 1.64). The symptomatic group showed more power in the lower frequency bands of the tibialis anterior's EMG spectra (p < 0.001), whereas no group differences were found in other muscles (all p>0.2). Within the step cycle, these differences appeared in the swing phase and in the gliding phase during single leg support. The observed differences in the EMG spectra may serve as an early identification of athletes who are at risk of developing CACS.     

Post-activation potentiation (PAP) in endurance sports: A review

While there is strong support of the usefulness of post-activation potentiation (PAP) phenomenon in power demanding sports, the role that PAP could play in endurance sports has received less attention. The aim of this review is to present evidence for a better understanding of PAP in endurance athletes; and to discuss the physiological basis and methodological aspects necessary for better practices and designing further studies. A search for relevant articles on PAP and endurance trained athletes was carried out using Medline and ISI Web of Knowledge databases. Twenty-two studies were included in the review. The current evidence suggests the possible influence of PAP for performance enhancement after appropriate conditioning activities during warm up. Evaluation of PAP responses during testing, training and competition may be also important for athletes monitoring. There are many unresolved questions about the optimum load parameters for benefiting from PAP in both training and competition; and the role that PAP may exert for optimal performance while interacting with central and peripheral factors associated with muscle fatigue. Further studies should elucidate the association between PAP responses and long-term adaptations in endurance athletes.     

冬奥会北欧两项运动员年龄和身体形态特征

研究目的：为北欧两项在中国的开展奠定理论基础,为运动员的科学选材提供理论依据。研究方法：文献资料法、数理统计法和对比分析法。研究结果：北欧两项运动员的年龄25．35±0．32岁,身高177．40±5．28cm,体重为67．12±6．01kg,体重指数37．48±2．12kg／cm。结论：北欧两项属于冬季项目中的混合型项目,既需要运动员有较好的耐力,又需要运动员能够出色地完成高难度的跳台动作,北欧两项世界优秀运动员的年龄偏大,身材比例适中,身高较高。     

Torque–velocity characteristics and contractile rate of force development in elite badminton players

Abstract

Elite badminton requires muscular endurance combined with appropriate maximal and explosive muscle strength. The musculature of the lower extremities is especially important in this context since rapid and forceful movements with the weight of the body are performed repeatedly throughout a match. In the present study, we examined various leg-strength parameters of 35 male elite badminton players who had been performing resistance exercises as part of their physical training for several years. The badminton players were compared with an age-matched reference group, the members of whom were physically active on a recreational basis, and to the same reference group after they had performed resistance training for 14 weeks. Maximal muscle strength of the knee extensor (quadriceps) and flexor muscles (hamstrings) was determined using isokinetic dynamometry. To measure explosive muscle strength, the contractile rate of force development was determined during maximal isometric muscle contractions. In general, the badminton players showed greater maximal muscle strength and contractile rate of force development than the reference group: mean quadriceps peak torque during slow concentric contraction: 3.69 Nm · kg^?1, s=0.08 vs. 3.26 Nm · kg^?1, s=0.8 (P<0.001); mean hamstring peak torque during slow concentric contraction: 1.86 Nm · kg^?1, s=0.04 vs. 1.63 Nm · kg^?1, s=0.04 (P<0.001); mean quadriceps rate of force development at 100 ms: 24.4 Nm · s^?1·kg^?1, s=0.5 vs. 22.1 Nm·s^?1 · kg^?1, s=0.6 (P<0.05); mean hamstring rate of force development at 100 ms: 11.4 Nm · s^?1·kg^?1, s=0.3 vs. 8.9 Nm · s^?1 · kg^?1, s=0.4 (P<0.05). However, after 14 weeks of resistance training the reference group achieved similar isometric and slow concentric muscle strength as the badminton players, although the badminton players still had a higher isometric rate of force development and muscle strength during fast (240° · s^?1) quadriceps contractions. Large volumes of concurrent endurance training could have attenuated the long-term development of maximal muscle strength in the badminton players. The badminton players had a higher contractile rate of force development than the reference group before and after resistance training. Greater explosive muscle strength in the badminton players might be a physiological adaptation to their badminton training.     

沈阳体育学院部分优秀足球运动员膝关节屈伸肌群形态与力量的相关研究

通过对沈阳体育学院部分优秀足球运动员膝关节屈伸肌群形态及力学相关指标的测定,探讨运动员膝关节屈伸肌群形态特征与肌肉收缩效应的特点以及两者间的内在规律,为运动员训练水平的评估及科学选材等方面提供理论指导。肌肉形态测量采用螺旋CT断层扫描,影像分析采用Motic Images Advanced 3.0测试系统软件,力量测试采用美国Cybex—Norm等速测力系统,数据处理采用SPSS.8.0软件。结果:足球运动员两侧大腿肌肉各相应断面面积间无明显差异,但一定程度上也体现了专项训练对运动员大腿肌肉形态的良好影响;峰力矩等力量指标在测试过程中的变化规律与Hill的肌肉收缩理论基本一致;肌肉形态与力量的相关性表现在低速伸膝时相关明显。     

3周1550 m亚高原训练对优秀青年男子越野滑雪运动员生理机能和身体成分影响研究

目的:探究3周海拔1550 m亚高原训练对优秀青年男子越野滑雪运动员生理机能和身体成分的影响,并且提出针对性的备战训练建议。方法:国家越野滑雪集训队10名优秀青年男子越野滑雪运动员[年龄(18.7±1.5)岁,身高(78.5±5.8)cm,体质量(66.6±4.7)kg]在亚高原(海拔1550 m)进行3周训练,并在亚高原训练前后对运动员的生理机能和身体成分进行系列测试。使用重复方差分析对运动员数据进行自身比较。结果:运动员由平原初上亚高原时,乳酸阈测试血乳酸浓度显著提升(P<0.05),最大摄氧量和红细胞浓度显著降低(P<0.05)。经过3周训练后,运动员的乳酸阈测试血乳酸浓度和最大摄氧量显著下降(P<0.05),全身总质量、上肢肌肉质量和下肢脂肪质量显著提升(P<0.05)。结论:由平原初上亚高原时,运动员乳酸阈能力和最大摄氧能力显著降低。3周亚高原训练后,运动员的乳酸阈能力和上肢肌肉水平显著提升,最大摄氧能力下降幅度明显。建议:在进行亚高原训练时,我国优秀青年越野滑雪运动员应当注重对心肺摄氧能力的训练,并且注意提升周平均高强度训练(high intensity training,HIT)训练总时间,以维持和提升最大摄氧能力。     

3周1550 m亚高原训练对优秀青年男子越野滑雪运动员生理机能和身体成分影响研究

目的:探究3周海拔1550 m亚高原训练对优秀青年男子越野滑雪运动员生理机能和身体成分的影响,并且提出针对性的备战训练建议。方法:国家越野滑雪集训队10名优秀青年男子越野滑雪运动员[年龄(18.7±1.5)岁,身高(78.5±5.8)cm,体质量(66.6±4.7)kg]在亚高原(海拔1550 m)进行3周训练,并在亚高原训练前后对运动员的生理机能和身体成分进行系列测试。使用重复方差分析对运动员数据进行自身比较。结果:运动员由平原初上亚高原时,乳酸阈测试血乳酸浓度显著提升(P<0.05),最大摄氧量和红细胞浓度显著降低(P<0.05)。经过3周训练后,运动员的乳酸阈测试血乳酸浓度和最大摄氧量显著下降(P<0.05),全身总质量、上肢肌肉质量和下肢脂肪质量显著提升(P<0.05)。结论:由平原初上亚高原时,运动员乳酸阈能力和最大摄氧能力显著降低。3周亚高原训练后,运动员的乳酸阈能力和上肢肌肉水平显著提升,最大摄氧能力下降幅度明显。建议:在进行亚高原训练时,我国优秀青年越野滑雪运动员应当注重对心肺摄氧能力的训练,并且注意提升周平均高强度训练(high intensity training,HIT)训练总时间,以维持和提升最大摄氧能力。     

预激活增强效应与耐力运动:表现、应用及调节

目的旨在探讨耐力运动预激活增强效应的研究进展,从生理学表现和研究方法方面为耐力项目运动训练方案设计提供理论依据。方法检索、整理和分析耐力运动预激活增强效应相关的文献。结果和结论预激活增强效应的生理机制为肌球蛋白调节轻链磷的酸化及神经肌肉特征的变化;预激活增强效应可用于优化耐力运动热身方案,提升运动成绩;耐力运动引发的神经肌肉特征变化可用于调节耐力运动中外周疲劳所带来的负面影响。未来的研究应进一步明确各专项的热身方案,在耐力训练或竞赛中的作用,最大限度地发挥预激活增强效应在各专项运动中的用作,热身活动中最佳的负荷强度也需进一步地研究,便于研究者们更好地探究用以提升运动成绩的训练方案。     

急性不同强度训练对越野滑雪男运动员脑α波的影响研究

了解我国越野滑雪男运动员的脑a波类型及不同负荷方式对运动员大脑自组织适应(熵值)的影响。方法:选取越野滑雪国家集训队18名男性运动员(一级以上)为被试,采用2(训练前测、训练后测)×4[高强度间歇训练(High-intensity Interval Training,HIT)、中等强度有氧运动(Moderate-intensity Aerobic Exercise,MAE)、低强度有氧运动(Low intensity Aerobic Exercise,LAE)和中等强度力量训练(Moderate-intensity Strength Training,MST)]单组交互设计的准实验研究。所有被试均分别按随机分配顺序执行四种不同强度训练任务,并在每次训练任务前后完成ET测试。结果:①我国越野滑雪运动员脑α波认知型所占的比例为认知型占38.9%,优化型占22.2%,其他类型占比较少;②不同强度训练前后测比较,HIT组和MAE组训练熵值升高差异显著(P<0.01),而LAE组和MST组的前后测熵值无显著差异(P>0.05);③组间差异比较显示HIT组熵值后测值相对于LAE组和MST组熵值后测值显著升高(P<0.01)。结论:①认知及优化型是我国越野滑雪男队员的主要脑功能类型;②1小时HIT、MAE训练导致运动员大脑功能有序化程度降低。     

越野滑雪运动员运动性疲劳的恢复

越野滑雪是周期性耐力项目,运动时间多、距离长,能量消耗大,对运动员的心理和机体能力要求较高。越野滑雪运动员的运动训练恢复是运动训练中的重要组成部分,良好的消除疲劳方法,能提高运动水平。结合越野滑雪运动训练实践,运用理论分析方法阐述越野滑雪运动疲劳产生的机理和检测方法,并提出恢复训练、营养补充和心理训练等方法,旨在为促进越野滑雪运动员运动疲劳的积极恢复提供理论依据。     

不同频率全身振动刺激对运动员下肢肌群力量训练效果的对比研究

采用PHYSIO PLATE振动训练台,对北京优秀垒球、女子游泳及女子跳水运动员进行同振幅下不同频率振动刺激力量训练,并采用MERAC等速肌力测试系统,对实验前后以及实验中运动员下肢肌力变化情况进行对比研究。研究发现,抗负荷力量训练附加振动刺激可以有效地提高力量训练的效果,能够以相对较小的负荷有效地提高肌肉的最大力量、爆发力以及肌肉耐力;同振幅下,次高频(35Hz～50Hz)振动刺激对肌肉最大力量、快速力量、爆发力以及肌肉耐力的训练效果显著高于中低频(25Hz～35Hz)振动刺激。     

Neuromuscular fatigue induced by an isotonic heavy-resistance loading protocol in knee extensors

Abstract

The main aim of this study was to assess neuromuscular fatigue during a typical high-load, low-repetition loading protocol. Muscle stimulations were used to assess maximum voluntary contraction, resting single- and double-pulse twitch characteristics, and superimposed double-pulse twitch force (used to calculate voluntary activation) before and after an acute knee extension loading protocol. In our participants, who had previous resistance training experience, the mean voluntary activation level was 96.2% in an unfatigued state. Maximum voluntary contraction (?11.8%), resting double-pulse twitch force (?10.6%), and voluntary activation (?2.1%) were markedly decreased as a consequence of loading (P < 0.05). In addition, although potentiated twitch characteristics were observed during the loading protocol, this was short-lived, as fatigue surpassed the potentiation mechanisms. Our results show that both central and peripheral mechanisms contributed to neuromuscular fatigue during the present loading protocol.     

Effects of external loading on power output in a squat jump on a force platform: A comparison between strength and power athletes and sedentary individuals

The aim of this study was to determine the effects of external loading on power output during a squat jump on a force platform in athletes specializing in strength and power events (6 elite weight-lifters and 16 volleyball players) and in 20 sedentary individuals. Instantaneous power was computed from time-force curves during vertical jumps with and without an external load (0, 5 or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Peak instantaneous power corresponded to the highest value of instantaneous power during jumping. Average power throughout the push phase of the jump was also calculated. A two‐way analysis of variance showed significant interactions between the load and group effects for peak instantaneous power ( P < 0.01) and average power ( P < 0.001). Peak instantaneous power decreased significantly in sedentary individuals when moderate external loads were added. The peak instantaneous power at 0 kg was greater than that at 5 and 10 kg in the sedentary individuals. In contrast, peak instantaneous power was independent of load in the strength and power athletes. Mean power at 0 kg was significantly lower than at 5 kg in the athletes; at 0 kg it was significantly higher than at 10 kg in the sedentary males and at 5 and 10 kg in the sedentary females. In all groups, the force corresponding to peak instantaneous power increased and the velocity corresponding to peak instantaneous power decreased with external loading. The present results suggest that the effects of external loading on peak instantaneous power are not significant in strength and power athletes provided that the loads do not prevent peak velocity from being higher than the velocity that is optimal for maximal power output.     

Effects of external loading on power output in a squat jump on a force platform: a comparison between strength and power athletes and sedentary individuals

The aim of this study was to determine the effects of external loading on power output during a squat jump on a force platform in athletes specializing in strength and power events (6 elite weight-lifters and 16 volleyball players) and in 20 sedentary individuals. Instantaneous power was computed from time-force curves during vertical jumps with and without an external load (0, 5 or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Peak instantaneous power corresponded to the highest value of instantaneous power during jumping. Average power throughout the push phase of the jump was also calculated. A two-way analysis of variance showed significant interactions between the load and group effects for peak instantaneous power (P< 0.01) and average power (P< 0.001). Peak instantaneous power decreased significantly in sedentary individuals when moderate external loads were added. The peak instantaneous power at 0 kg was greater than that at 5 and 10 kg in the sedentary individuals. In contrast, peak instantaneous power was independent of load in the strength and power athletes. Mean power at 0 kg was significantly lower than at 5 kg in the athletes; at 0 kg it was significantly higher than at 10 kg in the sedentary males and at 5 and 10 kg in the sedentary females. In all groups, the force corresponding to peak instantaneous power increased and the velocity corresponding to peak instantaneous power decreased with external loading. The present results suggest that the effects of external loading on peak instantaneous power are not significant in strength and power athletes provided that the loads do not prevent peak velocity from being higher than the velocity that is optimal for maximal power output.     

Gender influence on the adaptation of atrial performance to training

Background: High-intensity training has been associated with atrial remodelling and arrhythmias in men. Our purpose was to analyse atrial performance in female endurance athletes, compared to male athletes and controls. Methods: This was a cross-sectional study. We included four groups: female athletes, females controls, male athletes and male controls. Left (LA) and right atrial (RA) volumes and function were assessed using 2D and speckle-tracking echocardiography to determine peak atrial strain-rate at atrial (SRa) and ventricular contraction (SRs), as surrogates of atrial contractile and reservoir function, respectively. ANOVA and Bonferroni’s statistical tests were used to compare variables among groups. Results: We included 82 subjects, 39 women (19 endurance athletes, 20 controls) and 43 men (22 endurance athletes, 21 controls). Mean age was similar between groups (36.6?±?5.6 years). Athletes had larger bi-atrial volumes, compared to controls (women, LA 27.1 vs. 15.8?ml/m², p?<?0.001; RA 22.31 vs. 14.2?ml/m², p?=?0.009; men, LA: 25.0 vs. 18.5?ml/m², p?=?0.003; RA 30.8 vs. 21.9?ml/m², p?<?0.001) and lower strain-rate (women, LASRa ?1.60 vs. ?2.18?s^?1, p?<?0.001; RASRa ?1.89 vs. ?2.38?s^?1, p?=?0.009; men, LASRa ?1.21 vs. ?1.44?s^?1, p?=?1; RASRa ?1.44 vs. ?1.60?s^?1, p?=?1). However, RA indexed size was lower and bi-atrial deformation greater in female athletes, compared to male athletes. Conclusions: The atria of both male and female athletes shows specific remodelling, compared to sedentary subjects, with larger size and less deformation at rest, particularly for the RA. Despite a similar extent of remodelling, the pattern in women had greater bi-atrial myocardial deformation and smaller RA size.     

青少年越野滑雪运动员运动损伤特征及预防

青少年越野滑雪运动员是我国越野滑雪事业的后备力量,承载着我国越野滑雪运动的未来和希望,出现运动损伤将破坏运动训练的系统性,影响青少年越野滑雪运动员的长远发展。如何避免运动损伤就成为青少年越野滑雪运动员提升训练质量、提高比赛成绩、保证竞技能力可持续发展的关键因素。运用文献资料法、专家访谈法、问卷调查法与数理统计法对我国部分青少年越野滑雪运动员和教练员进行了调查研究。通过调查结果,分析了青少年越野滑雪运动员的伤病特征和致伤原因,总结了常见损伤的发生规律,并从训练学角度提出了相应的预防措施。     

Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males

Abstract

Muscle fiber type composition in the vastus lateralis and knee extension isometric strength fatigue patterns were assessed in eight endurance-trained and eight power-trained males. Two different 25-trial isometric contraction exercise regimens were administered: a 10-second contraction, 5-second intertrial rest condition designed to induce a fast rate of fatigue and a 10-second contraction, 20-second intertrial rest condition designed to induce a slower rate of fatigue. The power group fatigued almost four times faster than the endurance group in the 10:5 exercise condition. In the 10:20 exercise condition, the endurance group showed no fatigue pattern while the power group had a significant strength decrement of 32%. In both exercise conditions, the power group exhibited more complex fatigue patterns in terms of statistically significant trend components. Maximum isometric strength correlated positively with slow twitch (ST) percent number in power (r = .80) and endurance (r = .48) groups, but negatively with linear trend coefficients in endurance (r = -.62) and power (r = -.80) groups. Maximum isometric strength also correlated higher with fatigue curve trend coefficients than did muscle fiber type composition. Thus, a faster rate of fatigue was associated with higher maximum isometric strength and with higher ST percent number and area. Since maximum isometric strength correlated with body weight (r = .86 for groups combined), both maximum isometric strength and muscle mass appear to be more important determinants of knee extension isometric strength fatigue patterns than muscle fiber type composition.