短跑运动员股后肌群力量练习的下肢肌电特征分析

采用芬兰产Mega6000肌电仪和肌电仪器自带的Megawin2.4软件系统,让实验对象在做大腿后部肌群的力量练习手段如直腿后摆拉橡皮条、俯卧屈小腿拉橡皮条、俯卧后摆腿、俯卧跪起和仰卧挺髋力量练习手段的状态下,对实验对象的臀大肌、股二头肌、半腱半膜肌、腓肠肌内侧、阔筋膜张肌、股直肌和胫骨前肌进行肌电测试,并结合高速摄影技术分析肌电特征和肌肉的工作机制。结果表明,各块肌肉在力量练习过程中放电顺序、放电强度、放电时间、肌电积分值都不相同。因此,在力量训练时,应根据动作结构、肌肉收缩方式、收缩速度和力量大小等方面进行训练,使训练手段更能符合专项运动的规律。     

我国优秀双人滑男运动员落冰及模仿训练肌电特征研究

目的：探讨花样滑冰跳跃动作落冰过程中肌肉的工作特征及相关陆地模仿的训练效果。方法：以我国优秀双人滑男运动员张某为研究对象,利用 Mega ME6000肌电测试仪对其完成后外点冰两周跳、陆地两周跳、凳上跃起动作落地过程支撑腿落地后0.8 s内双侧胫骨前肌、腓肠肌外侧头、股直肌、股二头肌、臀大肌、竖脊肌、腹外斜肌和腹直肌的表面肌电信号进行采集,通过MegaWin2.4对原始数据进行处理分析。结果：完成专项动作时积分面积较大的8块肌肉依次为右侧股二头肌、右侧股直肌、右侧腓肠肌外侧头、左侧股二头肌、右侧胫骨前肌、右侧臀大肌、左侧臀大肌和右侧竖脊肌,多数工作肌的积分肌电峰值出现在落冰后的0.4 s左右;完成专项动作各肌肉积分面积与凳上跃起动作具有较高相关性（r=0.578,P=0.019）,与 陆地两周跳动作不相关;肌肉贡献度较大的肌肉中,专项动作与两种陆地模仿动作相比,支撑腿股二头肌、股直肌和腓肠肌外侧头的平均积分肌电 值明显偏高,积分肌电峰值出现时间不同。结论：完成后外点冰两周跳落冰动作的主要工作肌为支撑腿各肌群、同侧竖脊肌及摆动腿的股二头肌、臀大肌;凳上跃起和陆地两周跳两种陆地模仿练习的肌肉工作特征与专项动作有一定差异,可作为辅助训练手段,但不宜过多采用。     

优秀自由泳运动员水槽游泳技术及其肌电个案研究

利用表面肌电图和同步摄像技术,在游泳水槽实验条件下对优秀自由泳运动员的动作技术进行测试与分析.结果显示:表面肌电图和同步摄像技术能较好地检测游泳运动员动作技术;在游泳动作中,股直肌、胸大肌、肚二头肌、肚三头肌和屈腕肌的激活程度较大,在专项力量训练中应加强练习;运动员的动作协调性好,但动作技术仍需改善.     

现代短跑下肢力量的训练特点

现代短跑力量训练是以速度为核心，以肌肉专项收缩形式为依据而进行的专项力量训练。根据运动员下肢力量的特点，首先应该选择伸髋、伸踝、屈膝、屈髋、仲膝的力量进行练习；练习的肌肉首先应选择臀大肌、股二头肌、髂腰肌、半腱肌、半膜肌和小腿三头肌；练习的部位依次是髋关节、足关节和膝关节。     

基于膝关节静力学分析的杠铃力量训练专项化研究

通过膝关节载荷静力学分析，进一步认识了杠铃力量训练过程中膝关节的力学特点和变化规律。并基于膝关节载荷静力学分析，探讨了杠铃力量训练在力量练习结构、练习方式和练习动作方面的专项化问题。认为杠铃力量训练可以帮助运动员建立专项最需要的力量结构；可以通过不同的练习方式使那些对专项技术最具影响的肌肉或肌群得到训练；力量训练需要紧密结合专项特点，才能获得更好的效果。     

三种深蹲动作模式肌电特征的研究

目的：对3种不同深蹲模式进行肌电测试,以期探讨不同模式下动作的合理性,为教学、训练提供一定的理论依据。方法：本文运用文献资料法、实验法和数理统计法对不同模式的肌电测试进行对比分析研究。结果：动作模式1与动作模式2相比,股内侧肌、股直肌、股外侧肌、臀大肌有非常显著性差异（P〈0.01）,股二头肌有显著性差异（P〈0.05）。动作模式1与动作模式3相比,股内侧肌、股直肌、股外侧肌、臀大肌有非常显著性差异（P〈0.01）,股二头肌有显著性差异（P〈0.05）。动作模式2与动作模式3相比,股内侧肌、臀大肌有非常显著性差异（P〈0.01）,股直肌、股外侧肌有显著性差异（P〈0.05）,股二头肌没有显著性差异（P〉0.05）。结论：3种不同模式深蹲动作的股外侧肌、股直肌、股内侧肌、股二头肌、臀大肌的积分肌电数值表现出显著性差异,动作模式3优于其它两种动作模式。在深蹲训练中强调臀部肌肉的主动收缩,才能更好的提高下肢力量的作用。     

力量素质训练的专项化探讨

发展运动员力量素质的训练,必须遵循针对专项的力量素质特征。力量训练任务、手段和要求也日趋细化、结构化。能量代谢、动作力学、神经——肌肉系统专项化构成了力量训练专项化的内在结构与基本特征,力量训练专项化是练习设计、次数、组数、强度、速度、频率应与专项的能量、动作、神经——肌肉系统的需要保持一致,力量训练手段、负荷、要求只有在满足这些基本特征条件下才能有效保证专项化训练水平。强有力的核心肌群对运动中的身体姿势、运动技能和专项技术动作起着稳定和支持作用。     

柔道运动员投技中大外刈技术的表面肌电分析

以北京体育大学8名柔道运动员为研究对象,分为优秀组和普通组各4名,采用表面肌电测试方法并结合运动解剖学的基本理论对两组运动员柔道投技大外刈技术进行量化分析和评价,得出以下结论与建议:(1)sEMG信号分析中时域指标RMS和贡献率(work/loading)能较好反映柔道等复杂技术动作中肌肉的用力情况.(2)大外刈技术中两侧腹直肌、右侧腹外斜肌、肱二头肌、肱三头肌、臀大肌、股二头肌、腓肠肌内侧以及左侧三角肌后束、臀大肌、股直肌是主要用力肌肉,运动员在训练中应加强以上肌肉的练习.(3)普通组运动员左侧三角肌后束、左侧腹直肌、右侧肱二头肌力量过于薄弱,这可能是造成其技术不够成熟的因素之一,今后训练中应注意加强.(4)运动员在强化针对性肌肉力量练习的同时,除选择一般力量训练方法外,应多尝试采用适合柔道大外刈技术的专项力量训练方法,如拉滑车、爬绳、立卧撑等.     

非稳定支撑面上自由负重练习的肌电分析

为探究非稳定支撑面和自由负重对肌肉的刺激效果,选择13名体育院校大一男生(19.4±1.2yrs,176.9±4.8cm,67.9±4.9kg)在稳定支撑面(地面)和非稳定支撑面(Reebok Core Board,RCB)上进行3种负重(徒手、30%最大力量和60%最大力量,0,30%RM和60%RM)深蹲,并采集了比目鱼肌(SO)、股外侧肌(VL)、股内侧肌(VM)、股直肌(RF)、股二头肌(BF)、臀大肌(GMa)、臀中肌(GMe)和腰部竖脊肌(ULES)的表面肌电信号。研究结果表明,3种负重下,非稳定支撑面增加了大部分肌肉的活动量,但是,所有变化都不具有显著性;负重引起了大部分肌肉活动量的显著增加(P<0.05)。研究结论,非稳定支撑面不能有效增加对身体表层肌肉的刺激程度,不能替代负重对于发展肌肉横断面、最大力量和爆发力的作用;自由负重可以有效增加对身体表层肌肉的刺激程度,可能同样具有提高身体稳定性的作用;非稳定支撑面上的徒手或低负重练习和稳定支撑面上的自由负重练习不存在对立关系,二者可以作为一个完整力量训练计划的组成部分。     

我国女子速度滑冰运动员冰陆专项力量练习主要工作肌肉特点的比较研究

利用肌电图测试技术测试分析我国两名优秀女子短距离速滑运动员冰上过程中以及主要陆上专项力量练习动作下肢主要肌肉的用力规律,通过对比分析确定我国两名女子重点运动员速滑过程和陆上专项力量练习的肌肉发力特点,指出陆上专项力量练习与实际速滑过程中肌肉用力特点的差异,进而对陆上专项力量训练提出相关建议,旨在为教练员和运动员提高专项力量训练质量提供参考。     

Changes in transverse relaxation time of quadriceps femoris muscles after active recovery exercises with different intensities

Abstract

The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT were significantly lower than those in either inactive recovery or 100%LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in either inactive recovery or 100%LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in 100%LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.     

离心收缩训练对肌肉力量和肌电图RMS值的影响

为了研究离心训练对肌肉机能的影响,对18名运动员进行不同负荷的离心收缩训练,研究股四头肌和股二头肌肌肉力量和肌电图RMS值的变化,发现离心收缩训练对改善运动员的肌肉力量有明显效果,采用150%离心收缩训练和120%离心收缩训练对运动员肌电图RMS值也有一定的改善作用。     

Mechanics of the muscles crossing the hip joint during sprint running

Abstract

We aimed to demonstrate the changes over time in the lengths and forces of the muscles crossing the hip joint during overground sprinting and investigate the relationships between muscle lengths and muscle–tendon unit forces – particularly peak biceps femoris force. We obtained three-dimensional kinematics during 1 running cycle from 8 healthy sprinters sprinting at maximum speed. Muscle lengths and muscle–tendon unit forces were calculated for the iliacus, rectus femoris, gluteus maximus, and biceps femoris muscles of the target leg as well as the contralateral iliacus and rectus femoris. Our results showed that during sprinting, the muscles crossing the hip joint demonstrate a stretch-shortening cycle and 1 or 2 peak forces. The timing of peak biceps femoris force, expressed as a percentage of the running cycle (mean [SD], 80.5 [2.9]%), was synchronous with those of the maximum biceps femoris length (82.8 [1.9]%) and peak forces of the gluteus maximus (83.8 [9.1]%), iliacus (81.1 [5.2]%), and contralateral iliacus (78.5 [5.8]%) and also that of the peak pelvic anterior tilt. The force of the biceps femoris appeared to be influenced by the actions of the muscles crossing the hip joint as well as by the pelvic anterior tilt.     

Electromyographic analysis of thigh muscles during track cycling on a velodrome

We aimed to investigate neuromuscular activation of thigh muscles during track cycling at various speeds. Eight male competitive cyclists volunteered to participate in this study. Surface electromyography of the vastus lateralis, biceps femoris and adductor magnus muscles of the bilateral legs was recorded during track cycling on velodromes with a 250-m track. The participants were instructed to maintain three different lap times: 20, 18 and 16 s. The average rectified value (ARV) was calculated from the sampled surface electromyography. Significantly higher ARVs were observed in the right compared to left leg for the biceps femoris muscle during both straight and curved sections at 18- and 16-s lap times (P < 0.05). In the biceps femoris muscle, significant changes in ARVs during the recovery phase with an increase in speed were seen in the right leg only (P < 0.05). There were no significant differences in ARVs between the straight and curved sections for all three muscles (P > 0.05). From our findings, it was suggested that during track cycling on a velodrome the laterality of the biceps femoris muscle activity is a key strategy to regulate the speed, and fixed neuromuscular strategies are adopted between straight and curved sections for thigh muscles.     

Functional differences in the activity of the hamstring muscles with increasing running speed

Abstract

In this study, we examined hamstring muscle activation at different running speeds to help better understand the functional characteristics of each hamstring muscle. Eight healthy male track and field athletes (20.1 ± 1.1 years) performed treadmill running at 50%, 75%, 85%, and 95% of their maximum velocity. Lower extremity kinematics of the hip and knee joint were calculated. The surface electromyographic activities of the biceps femoris and semitendinosus muscles were also recorded. Increasing the running speed from 85% to 95% significantly increased the activation of the hamstring muscles during the late swing phase, while lower extremity kinematics did not change significantly. During the middle swing phase, the activity of the semitendinosus muscle was significantly greater than that of the biceps femoris muscle at 75%, 85%, and 95% of running speed. Statistically significant differences in peak activation time were observed between the biceps femoris and semitendinosus during 95%max running (P < 0.05 for stance phase, P < 0.01 for late swing phase). Significant differences in the activation patterns between the biceps femoris and semitendinosus muscles were observed as running speed was increased, indicating that complex neuromuscular coordination patterns occurred during the running cycle at near maximum sprinting speeds.     

Effects of forward trunk lean on hamstring muscle kinematics during sprinting

This study aimed to investigate the effects of forward trunk lean on hamstring muscle kinematics during sprinting. Eight male sprinters performed maximal-effort sprints in two trunk positions: forward lean and upright. A three-dimensional musculoskeletal model was used to compute the musculotendon lengths and velocity of the biceps femoris long head, semitendinosus, and semimembranosus muscles during the sprinting gait cycle. The musculotendon lengths of all the three hamstring muscles at foot strike and toe-off were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. In addition, a positive peak musculotendon lengthening velocity was observed in the biceps femoris long head and semimembranosus muscles during the late stance phase, and musculotendon lengths at that instant were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. The present study provides significant evidence that a potential for hamstring muscle strain injury involving forward trunk lean sprinting would exist during the stance phase. The results also indicate that the biceps femoris long head and semimembranosus muscles are stretched during forward trunk lean sprinting while contracting eccentrically in the late stance phase; thus, the elongation load on these muscles could be increased.     

Electromechanical delay of the knee flexor muscles after anterior cruciate ligament reconstruction using semitendinosus tendon

The purpose of the study was to evaluate whether using only the semitendinosus as a tripled short graft would affect the electromechanical delay (EMD) of the knee flexors. EMD was evaluated in volunteers (N = 15) after they had undergone surgery for anterior cruciate ligament (ACL) reconstruction where the semitendinosus tendon alone was used as a graft. The results were compared with the intact leg and healthy controls (N = 15). After warming up, each subject performed four maximally explosive isometric contractions on an isokinetic dynamometer. Torques were measured by the dynamometer, while the electrical activity of the semitendinosus and biceps femoris muscles was detected using surface electromyography. EMD was found to be significantly increased (p = 0.001) in patients who had undergone ACL reconstruction compared to the controls. On the contrary, no significant differences (p = 0.235) were found for the biceps femoris muscle between the two groups. Similar results were found when the study group was compared with the intact leg group (p = 0.027 for semitendinosus and p = 0.859 for biceps femoris). Harvesting the semitendinosus tendon increases the EMD for the semitendinosus muscle but does not influence the EMD outcomes for the biceps femoris muscle.     

Corticospinal changes induced by fatiguing eccentric versus concentric exercise

The present study assessed neuromuscular and corticospinal changes during and after a fatiguing submaximal exercise of the knee extensors in different modes of muscle contraction. Twelve subjects performed two knee extensors exercises in a concentric or eccentric mode, at the same torque and with a similar total impulse. Exercises consisted of 10 sets of 10 repetitions at an intensity of 80% of the maximal voluntary isometric contraction torque (MVIC). MVIC, maximal voluntary activation level (VAL) and responses of electrically evoked contractions of the knee extensors were assessed before and after exercise. Motor evoked potential amplitude (MEP) and cortical silent period (CSP) of the vastus medialis (VM) and rectus femoris (RF) muscles were assessed before, during and after exercise. Similar reductions of the MVIC (?13%), VAL (?12%) and a decrease in the peak twitch (?12%) were observed after both exercises. For both VM and RF muscles, MEP amplitude remained unchanged during either concentric or eccentric exercises. No change of the MEP amplitude input–output curves was observed post-exercise. For the RF muscle, CSP increased during the concentric exercise and remained lengthened after this exercise. For the VM muscle, CSP was reduced after the eccentric exercise only. For a similar amount of total impulse, concentric and eccentric knee extensor contractions led to similar exercise-induced neuromuscular response changes. For the two muscles investigated, no modulation of corticospinal excitability was observed during or after either concentric or eccentric exercises. However, intracortical inhibition showed significant modulations during and after exercise.     

Effect of the level of effort during resistance training on intraocular pressure

Background: We aimed to evaluate the influence of the level of effort during four basic resistance exercises leading to muscular failure on intraocular pressure (IOP) and ocular perfusion (OPP), as well as the role of exercise type and sex. Methods: Twenty-five young adults (12 women) performed 10 repetitions against their 10-RM (repetition maximum) load in the squat, military press, biceps curl and calf raise exercises. IOP was measured before, during and after exercise, whereas OPP was indirectly assessed before and after each exercise. Results: There was a progressive IOP rise during exercise (p?η²?=?0.531), which was dependent on exercise type (p?=?0.020, η²?=?0.125). The squat exercise induced higher IOP increments in comparison to the other exercises (corrected p-values?p-values?=?0.012 and 0.002). OPP exhibited a significant reduction when leading to muscular failure (p?=?0.001, η²?=?0.364), being statistically significant for the squat and military press exercises (corrected p-values?=?0.037 and 0.047). No effect of sex was found for IOP and OPP (p?>?0.05). Conclusions: A single set of resistance training leading to muscular failure causes an instantaneous and progressive IOP rise in healthy young individuals. These IOP rises depend on exercise type (squat?>?military press?=?biceps curl?>?calf raise), but not on participant´s sex. OPP diminished as a consequence of performing resistance training exercise, being statistically significant for the squat and military press exercises. Future studies should include glaucoma patients aiming to corroborate the generalizability of our findings.