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101.
Angus M. Hunter Giuseppe De Vito Claire Bolger Hugh Mullany Stuart D. R. Galloway 《Journal of sports sciences》2013,31(12):1261-1269
Abstract The aim of this study was to determine if inducing metabolic alkalosis would alter neuromuscular control after 50 min of standardized submaximal cycling. Eight trained male cyclists (mean age 32 years, s = 7; [Vdot]O2max 62 ml · kg?1 · min?1, s = 8) ingested capsules containing either CaCO3 (placebo) or NaHCO3 (0.3 g · kg?1 body mass) in eight doses over 2 h on two separate occasions, commencing 3 h before exercise. Participants performed three maximal isometric voluntary contractions (MVC) of the knee extensors while determining the central activation ratio by superimposing electrical stimulation both pre-ingestion and post-exercise, followed by a 50-s sustained maximal contraction in which force, EMG amplitude, and muscle fibre conduction velocity were assessed. Plasma pH, blood base excess, and plasma HCO3 were higher (P < 0.01) during the NaHCO3 trial. After cycling, muscle fibre conduction velocity was higher (P < 0.05) during the 50-s sustained maximal contraction with NaHCO3 than with placebo (5.1 m · s?1, s = 0.4 vs. 4.2 m · s?1, s = 0.4) while the EMG amplitude remained the same. Force decline rate was less (P < 0.05) during alkalosis-sustained maximal contraction and no differences were shown in central activation ratio. These data indicate that induced metabolic alkalosis can increase muscle fibre conduction velocity following prolonged submaximal cycling. 相似文献
102.
Ayako Higashihara Takashi Ono Jun Kubota Toru Okuwaki Toru Fukubayashi 《Journal of sports sciences》2013,31(10):1085-1092
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. 相似文献
103.
Abstract The aim of this study was to characterize forearm muscle fatigue identified by the decrease in electromyogram median frequency and/or fingertip force during intermittent exercise. Nine elite climbers (international competitive level, USA 5.14a on sight) and ten non-climbers were instructed to maintain a fingertip force of 80% of their maximal voluntary contraction force on a dynamometer mimicking a rock climbing grip during a 5 s effort/5 s rest cycle for 36 repetitions (i.e. 6 min of exercise). Elite climbers lasted twice as long as non-climbers (climbers: 3 min; non-climbers: 1 min 30 s) before the force could no longer be maintained (i.e. the failure point). After this moment, fingertip force decreased and stabilized until the end of the exercise around 50% maximum voluntary contraction force in non-climbers and 63% in elite climbers. Electromyogram median frequency showed a greater decrease in non-climbers than in elite climbers before the failure point. No change in median frequency was observed after the failure point in elite climbers or in non-climbers. These results confirm that elite climbers are better adapted than non-climbers for performing the intermittent fingertip effort before the failure point. After this point, the better fingertip force of elite climbers suggests different forearm muscle properties, while the electromyography results do not provide any indication about the fatigue process. 相似文献
104.
Charlotte Apps Mark Lake Thomas D. O’Brien Thorsten Sterzing 《Journal of sports sciences》2013,31(17):1951-1961
ABSTRACTUnstable footwear may enhance training effects to the lower-limb musculature and sensorimotor system during dynamic gym movements. This study compared the instability of an unstable shoe with irregular midsole deformations (IM) and a control shoe (CS) during forward and lateral lunges. Seventeen female gym class participants completed two sets of ten forward and lateral lunges in CS and IM. Ground reaction forces, lower-limb kinematics and ankle muscle activations were recorded. Variables around initial ground contact, toe-off, descending and ascending lunge phases were compared statistically (p < .05). Responses to IM compared to CS were similar across lunge directions. The IM induced instability by increasing the vertical loading rate (p < .001, p = .009) and variability of frontal ankle motion during descending (p = .001, p < .001) and ascending phases (p = .150, p = .003), in forward and lateral lunges, respectively. At initial ground contact, ankle adjustments enhanced postural stability in IM. Across muscles, there were no activation increases, although results indicate peroneus longus activations increased in IM during the ascending phase. As expected, IM provided a more demanding training stimulus during lunge exercises and has potential to reduce ankle injuries by training ankle positioning for unpredictable instability. 相似文献
105.
MATTHEW K. SEELEY TIM L. UHL JEAN MCCRORY PATRICIA MCGINN W. BEN KIBLER ROBERT SHAPIRO 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):248-259
The abbreviated tennis serve is a relatively novel modification of the traditional serve that has been reported to provide performance advantages over the traditional technique. However, there are limited objective data regarding the benefits and biomechanics of the abbreviated serve; no data exist that describe shoulder muscle activations during the abbreviated serve. The purpose of this study was to compare muscle activations between the traditional and abbreviated serves. Electromyographic data were collected for the anterior and posterior deltoid, infraspinatus, middle trapezius, latissimus dorsi, serratus anterior, and pectoralis major. When muscle activations were compared during each serve phase, no significant differences were observed between the traditional and abbreviated tennis serve techniques, indicating that the traditional and abbreviated serves are similar regarding shoulder muscle activations. These results could have implications for performance of and injury related to the abbreviated versus traditional serve technique. Although the abbreviated serve has anecdotally been described as advantageous, the present data do not indicate any significant advantages or disadvantages in performing the abbreviated serve technique versus the traditional serve. 相似文献
106.
Biomechanical validation of a specific upper body training and testing drill in cross‐country skiing
Thomas Stöggl Stefan Lindinger Erich Müller 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):23-46
The aim of this study was to perform a biomechanical validation of a double poling imitation drill on a rollerboard. Six elite cross‐country skiers performed three imitation drill trials at maximal speed at 13° inclination and in double poling on roller skis on a paved road of 3°. Pole and strap forces, elbow and hip angles and EMG activity of eight upper body muscles were measured. Force curves showed similar characteristics, except for impact force occurring only at pole plant in double poling on roller skis. Double poling on a rollerboard includes an eccentric roll‐down phase not appearing in double polling on roller skis. Forces on the rollerboard were similar to those on roller skis. Courses of the elbow angles indicated similar shapes, except for the angle at the start of the propulsion phase and, consequently, during flexion (p < 0.01). Propulsion time and cycle duration were longer and frequency lower on the rollerboard (all p < 0.001). Muscle activities were not significantly different, except for stronger biceps brachii (p < 0.01) and weaker erector spinae activation (p < 0.05) on the rollerboard. Muscle coordination patterns showed similar onset and offset points of each muscle and comparable activations in both activities, except for biceps brachii. Two movement strategies on the rollerboard were found, which led to small differences in measured variables. The biomechanical validity of double poling on a rollerboard can be judged as moderately high, being aware of the differences in some variables that might be considered in training sessions on the rollerboard, particularly when using intervals with high number of repetitions. 相似文献
107.
《Research quarterly for exercise and sport》2012,83(4):641-650
ABSTRACTA quick, well-timed pelvic-floor muscle contraction during physical effort is recommended for active women to prevent urine leakage. Purpose: We address two research questions: how well do future female exercise professionals contract the pelvic-floor muscles, and whether the biofeedback session is necessary to train them to contract pelvic-floor muscles? Method: Participants were 84 nulliparous future exercise professionals (age 23 ± 3 years, mean ± SD), randomly allocated into biofeedback (n = 27), usual-advice (n = 26), and control (no advice, n = 21) groups. Contraction of pelvic-floor muscles on a 4-point scale (1 = incorrect through 4 = correct) was assessed in all groups by surface electromyography (sEMG) with a vaginal probe before and after 6 weeks of intervention. Results: In pretest, almost one in five participants (17%) could not activate the pelvic floor and less than half of them (45%) presented correct technique. The technique score for the three groups was 3.1 ± 1.1 (mean ± SD). After training, both intervention groups presented better technique score by 0.6 (90% confidence limits ± 0.5) relative to the control group, and two-thirds (65%) of the intervention groups presented the correct technique. Conclusions: Future exercise professionals displayed poor skills in contracting pelvic-floor muscles. Both training interventions (with and without biofeedback) were effective for this study group. 相似文献
108.
通过对攀岩运动员的上肢主要做功肌肉左右腕屈肌、左右腕伸肌的表面肌电信号(sEMG)进行分析,探讨不同负荷的运动诱发肌肉疲劳过程中sEMG信号变化特征及其与肌肉耐力运动的关系. 相似文献
109.
sEMG信号分析及其应用研究进展 总被引：83，自引：7，他引：76
表面肌电信号是从肌肉表面通过电极引导,记录下来的神经肌肉系统活动时的一维时间序列信号,其变化与参与活动的运动单位数量,运动单位活动模式和代谢状态等因素有关,能够实时地,准确地和在非损伤状态下反映肌肉活动状态和功能状态。本文拟就ｓＥＭＧ信号分析及其应用研究进展进行系统回顾。 相似文献
110.
目的:1)建立量化分析肌肉协调性的方法;2)分析肌肉协调性对运动技术的影响。研究方法:以我国六名优秀20 km竞走运动员研究对象,同步采集运动员在3.6 m/s和4.3 m/s直线运动时膝关节角度与股二头肌和股直肌表面肌电信号,并建立了肌电时序特征的定性分析和肌电数组和肌电模型相关性的定量分析肌肉协调性的方法。研究结果:股直肌和股二头肌在肌电的时序特征上表现出明显的协调性特征,而且二者的肌电数组和肌电模型与膝角相关性较高(r>0.70),但运动员间肌电模型一致性较差(r=0.339)。结论:1)本研究采用的对竞走运动中股直肌和股二头肌肌电时序的相关性分析方法是可以作为一种分析肌肉协调性的手段。2)竞走速度的提高引起了股直股和股二头肌的协调性下降。对膝关节技术的影响表现为:摆动腿在后摆阶段时膝角增大、着地瞬间膝角减小。 相似文献