排序方式： 共有117条查询结果，搜索用时 15 毫秒
51.
Stability of pedalling mechanics during a prolonged cycling exercise performed at different cadences
The aim of this study was to analyse the effect of pedalling rate on the pattern of mechanical torque application and on neuromuscular fatigue during prolonged cycling exercise. Eleven well-trained individuals performed three 1-h pedalling sessions, at 50 rev?·?min?1, 110 rev?·?min?1 and a freely chosen cadence, at an intensity corresponding to 65% of their maximal aerobic power. The mechanical torque applied on the right pedal was recorded for 30?s every 5?min while pedalling. Contractile and neural properties of the quadriceps and hamstring muscles were analysed before and immediately after each of the three pedalling sessions. The post-exercise reduction in knee extensors maximal voluntary contraction was significant (P <?0.01) irrespective of the cadence, but no difference was found between cadences. The use of a particular cadence did not lead to preferentially central or peripheral fatigue. An increase in cadence resulted in greater positive and negative work generated during pedalling. The mechanical pattern was not altered during the exercise, whatever the selected cadence. The present study demonstrates that despite the occurrence of neuromuscular fatigue, trained individuals maintained a stable pedalling pattern throughout an endurance cycling exercise for cadences ranging from 50 to 110 rev?·?min?1. 相似文献
52.
Abstract We examined the effect of recovery pattern on mechanical and neuromuscular responses in active men during three repeated-sprint ability tests consisting of ten 6-s cycling sprints. Within each test, the recovery duration was manipulated: constant, increasing, and decreasing recovery pattern. Maximal voluntary contractions of the knee extensors were performed before and after the repeated-sprint ability tests to assess strength and electromyographic activity [root mean square (RMS)] of the quadriceps muscle. We observed different fatigue patterns for peak and mean power output between recovery patterns, with earlier decrements recorded during the increasing recovery pattern. Total work performed over the ten sprints was also lower in the increasing recovery pattern (43.8 ± 5.4 kJ; P < 0.05). However, the decreasing recovery pattern induced a greater overall power output decrement across the sprints (?15.8%; P < 0.05), compared with the increasing recovery pattern (?5.1%) but not the constant recovery pattern (?10.1%). The decreasing recovery pattern was also associated with higher post-sprint RMS values (+16.2%; P < 0.05). Therefore, the recovery pattern within successive short sprints may influence repeated-sprint ability, and may lead to greater post-sprint neuromuscular adjustments when recovery intervals decrease between sprints. We conclude that peripheral impairments caused the major differences in repeated-sprint ability between recovery patterns. 相似文献
53.
Eric D. Ryan Trent J. Herda Pablo B. Costa Jason M. Defreitas Travis W. Beck Jeffrey Stout 《Journal of sports sciences》2013,31(9):957-961
Abstract In this study, we examined the minimum number of constant-torque passive stretches necessary to reduce musculotendinous stiffness. Thirteen healthy individuals (mean age 22 years, s = 3; stature 1.67 m, s = 0.1; mass 66 kg, s = 13 kg) volunteered to participate in the investigation and underwent four 30-s constant-torque passive stretches of the plantar flexor muscles. Musculotendinous stiffness was examined from the angle–torque curves generated prior to the passive stretches, at the beginning of each 30-s stretch, and immediately following the four 30-s passive stretches. The results indicated that musculotendinous stiffness of the plantar flexors was reduced following two 30-s constant-torque passive stretches (P < 0.05) compared with the pre- musculotendinous stiffness assessment. Musculotendinous stiffness remained depressed following the third and fourth stretches, but did not decrease further. These findings suggest that two 30-s bouts of constant-torque passive stretching may be necessary to cause a significant decrease in musculotendinous stiffness of the plantar flexor muscles. 相似文献
54.
Gavin R. Devereux Damian Coleman Jonathan D. Wiles Ian Swaine 《Journal of sports sciences》2013,31(11):1141-1148
Abstract The purpose of this study was (a) to assess lactate accumulation during isometric exercise, and to quantify the shifts in accumulation following isometric training; and (b) to relate any training-induced changes in lactate accumulation to reductions in resting blood pressure. Eleven male participants undertook isometric training for a 4-week period using bilateral-leg exercise. Training caused reductions in systolic, diastolic, and mean arterial resting blood pressure (of ?4.9 ± 6.3 mmHg, P = 0.01; ?2.6 ± 3.0 mmHg, P = 0.01; and ?2.6 ± 2.3 mmHg, P = 0.001 respectively; mean ± s). These were accompanied by changes in muscle activity, taken as electromyographic activity to reach a given lactate concentration (from 114 ± 22 to 131 ± 27 mV and from 136 ± 25 to 155 ± 34 mV for 3 and 4 mmol · L?1 respectively. Training intensity expressed relative to peak lactate was correlated with reduced resting systolic and mean arterial blood pressure. Training caused significant shifts in lactate accumulation, and reductions in resting blood pressure are strongly related to training intensity, when expressed relative to pre-training peak lactate. This suggests that higher levels of local muscle anaerobiosis may promote the training-induced reductions in resting blood pressure. 相似文献
55.
Tarak Driss Virgile Serrau David George Behm Ethelle Lesne-Chabran Armande Le Pellec-Muller Henry Vandewalle 《Journal of sports sciences》2013,31(1):60-69
AbstractThe present investigation verified that strength is improved by a training programme consisting of repetitions of maximal isometric voluntary co-contractions without increasing co-activations during contractions against external resistances. Ten participants performed 12 training sessions (four sets of 6 × 4 second maximal isometric co-contraction of the elbow flexor and extensors, 3 days a week for 4 weeks). Surface electromyograms of triceps and biceps brachii were collected during maximal voluntary isometric elbow flexion and extension against a force transducer. Maximal voluntary isometric force increased significantly after training, by 13.8 ± 6.0% (extension) and 9.6 ± 9.5% (flexion), but the observed increases in EMG of agonist muscles during maximal voluntary contraction were not significant. No significant changes in the levels of co-activation of the elbow flexors and extensors were observed. No significant change was observed for all the parameters in a control group of ten participants. These results indicated that the strength improvements after co-contraction training occur without increases in co-activation level. 相似文献
56.
Kohei Watanabe Hiroyuki Nunome Koichiro Inoue Takahiro Iga Hiroshi Akima 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(3):295-306
ABSTRACTA possible link between soccer-specific injuries, such as groin pain and the action of hip adductor muscles has been suggested. This study aimed to investigate neuromuscular activation of the adductor magnus (AM) and longus (AL) muscles during instep and side-foot soccer kicks. Eight university soccer players performed the two types of kick at 50%, 75% and 100% of the maximal ball speed. Surface electromyography (EMG) was recorded from the AM, AL, vastus lateralis (VL) and biceps femoris (BF) muscles of both kicking and supporting legs and the kicking motions were three-dimensionally captured. In the kicking leg, an increase in surface EMG with an increase in ball speed during instep kicking was noted in the AM muscle (p < 0.016), but not in AL, VL or BF muscles (p > 0.016). In the supporting leg, surface EMG of both AM and AL muscles was significantly increased with an increase in the ball speed before ball impact during both instep and side-foot kicks (p < 0.016). These results suggest that hip adductor muscles markedly contribute to either the kicking or supporting leg to emphasise the action of soccer kicks. 相似文献
57.
旋转推铅球过渡阶段肌肉用力特征的sEMG分析 总被引：2，自引：0，他引：2
采用遥测肌电测试,同时结合影像解析,分析了我国优秀男子铅球运动员张竣过渡阶段的主要用力肌肉及其用力顺序、用力范围和主要用力肌肉之间的协调关系,其目的是为了改进张竣过渡阶段存在的技术问题和寻找出肌肉用力的内部动因,同时建立起来一整套适合张竣本人肌肉用力特征的肌电模型,并且为改进张竣专项力量训练的手段,优化训练方法提供技术性和理论性指导。 相似文献
58.
目的：检索全身振动对神经肌肉功能影响的研究文献,探讨全身不同振动特性(频率、振幅及振动方法)和运动方案对神经肌肉功能的影响。方法：1）检索中国知网、PubMed、Embase和Web of science数据库进行文献检索;2）24篇文献进行分析,根据排除和纳入标准,最终筛选5篇文献;3）运动方式有膝关节伸展、膝关节屈曲、下蹲跳(CMJ)、跳高 (JH)等;4）依据ISMNI文献质量进行分级。结果：1）全身振动可提高肌肉力量、功率和柔韧性。2）改善肌肉功能的主要因素有振幅、频率、振动类型及使用方法、运动强度、运动方案和受试者的特征。结论：全身振动结合运动训练更有效地改善神经肌肉功能。 相似文献
59.
This paper is concerned with a control method for an exoskeleton ankle with electromyography (EMG) signals. The EMG signals
of human ankle and the exoskeleton ankle are introduced. Then a control method is proposed to control the exoskeleton ankle
using the EMG signals. The feed-forward neural network model applied here is composed of four layers and uses the back-propagation
training algorithm. The output signals from neural network are processed by the wavelet transform. Finally the control orders
generated from the output signals are passed to the motor controller and drive the exoskeleton to move. Through experiments,
the equality of neural network prediction of ankle movement is evaluated by giving the correlation coefficient. It is shown
from the experimental results that the proposed method can accurately control the movement of ankle joint.
Project supported by the National High-Tech R&D Program (Grant No.2006AA04Z224), the Innovation Program of Shanghai Municipal
Education Commission (Grant No.08ZZ48), and the Shanghai Leading Academic Discipline Project (Grant No.Y0102) 相似文献
60.
Timothy C. Mauntel Tyler R. Cram Barnett S. Frank Rebecca L. Begalle Marc F. Norcross J. Troy Blackburn 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(2):273-284
Lower extremity injuries have immediate and long-term consequences. Lower extremity movement assessments can assist with identifying individuals at greater injury risk and guide injury prevention interventions. Movement assessments identify similar movement characteristics and evidence suggests large magnitude kinematic relationships exist between movement patterns observed across assessments; however, the magnitude of the relationships for electromyographic (EMG) measures across movement assessments remains largely unknown. This study examined relationships between lower extremity kinematic and EMG measures during jump landings and single leg squats. Lower extremity three-dimensional kinematic and EMG data were sampled from healthy adults (males = 20, females = 20) during the movement assessments. Pearson correlations examined the relationships of the kinematic and EMG measures and paired samples t-tests compared mean kinematic and EMG measures between the assessments. Overall, significant moderate correlations were observed for lower extremity kinematic (ravg = 0.41, rrange = 0.10–0.61) and EMG (ravg = 0.47, rrange = 0.32–0.80) measures across assessments. Kinematic and EMG measures were greater during the jump landings. Jump landings and single leg squats place different demands on the body and necessitate different kinematic and EMG patterns, such that these measures are not highly correlated between assessments. Clinicians should, therefore, use multiple assessments to identify aberrant movement and neuromuscular control patterns so that comprehensive interventions can be implemented. 相似文献