Short- and long-term reliability of leg extensor power measurement in middle-aged and older adults     

Christopher Hurst  Alan M Batterham  Kathryn L Weston  Matthew Weston 《Journal of sports sciences》2018,36(9):970-977

Muscular power is important for maintaining physical functioning with aging. Proper quantification of the reliability of muscular power tests is crucial to inform monitoring of individuals and sample size planning for interventional studies. This study evaluated short- and long-term reliability of leg extensor power measurement in 72 adults (age 62.7 ± 8.6 years). Participants completed four repeat trials on the Nottingham leg extensor power rig, with a further trial twelve weeks later. Mean change, typical error, and intraclass correlation coefficients (ICC) were calculated. For short-term reliability, mean change in power output was trivial after two trials (1.2–4.8%). Typical errors were small following four trials in the dominant leg of males (10.9–5.8%), three in the non-dominant leg of males (9.9–6.2%) and the dominant leg of females (10.0–9.6%) and two in the non-dominant leg in females (8.3%). Intraclass correlation coefficients (ICCs) were very high (0.88–0.96). For long-term reliability, mean change remained trivial (1.0–2.5%), typical errors remained small (5.8–8.6%), and ICCs very high (0.94–0.96). The leg extensor power rig is a reliable method for assessing lower body muscular power, both short- and long-term, with only minimal habituation effects.  相似文献   

Specific muscle synergies in national elite female ice hockey players in response to unexpected external perturbation     

Minhee Kim  Yushin Kim  Hyeyoung Kim 《Journal of sports sciences》2018,36(3):319-325

This study aimed to investigate specific muscle synergies in elite ice hockey players indicating highly developed postural control strategies used to restore balance against unexpected external perturbations. Seven elite athletes (EA) on the women’s national ice hockey team and 7 non-athletes (NA) participated in this study. Based on trajectories of centre of mass (COM), analysis periods were divided into an initial phase (a balance disturbance after perturbation onset) and a reversal phase (a balance recovery response), respectively. Muscle synergies were extracted at each phase by using non-negative matrix factorization. k-means cluster analysis was performed to arrange similar muscle synergies in all participants. EA showed significantly shorter recovery period of COM and smaller body sway than NA. In the initial phase, we identified 2 EA-specific synergies related to ankle plantar flexors or neck extensors. In the case of an NA-specific synergy, co-activation of the ankle plantar flexors and dorsiflexors was found. In the reversal phase, no specific muscle synergies were identified. As the results, EA-specific muscle synergies showed low co-activation strategy of agonists and antagonists in ankle and neck extensors. Our results could provide critical information for rehabilitation strategies in athletes requiring high postural stability.  相似文献   

Acupuncture on Intracellular Ionic Distribution inMuscle Injury and Its Mechanism     

QU Zhuqing  LU Dinghou  WANG Yirun 《北京体育大学学报》1995,(Z2)

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A new linearly-combined bi-exponential model for kinetic analysis of the isometric relaxation process of <Emphasis Type="Italic">Bufo gastrocnemius</Emphasis> under electric stimulation in vitro     

Guo R  Li SB  Zhao LN  Zhao YS  Lu W  Yuan P  Deng P  Liao F 《Journal of Zhejiang University. Science. B》2007,8(12):867-874

There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca^2＋-pump by cyclopiazonic acid （CPA）. Herein, a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro, in comparison to the single exponential model and the classical bi-exponential model. During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency （DC）, the isometric tension of Bufo gastrocnemius was recorded at 100 Hz. The relaxation curve with tensions falling from 90% of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5. Both the goodness of fit and the distribution of the residuals for the best fitting supported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles. After CPA treatment, however, this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process, and it gave the estimated rest tension consistent to that by experimentation, whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions. Moreover, after the treatment of muscles by CPA, both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates, nevertheless, this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions. These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca2^＋-pumping activity.  相似文献   

Modeling of musculoskeletal structure and function using a modular bond graph approach     

Laura A. Wojcik 《Journal of The Franklin Institute》2003,340(1):63-76

The dynamic effects of muscle strength, timing of muscle activations, and body geometry have been modeled for a wide variety of human activities. These types of models require the development of complex system equations that account for the effects of rigid-body dynamics, musculotendon actuators, passive and active resistance to motion, and other physiological structures. One way in which model refinement can be expedited is through the use of bond graph modeling techniques. While bond graph techniques have been used extensively in a broad variety of applications, they have been used only sparingly in the field of biomechanics, despite the potential suitability of a modular, multidomain approach to the modeling of musculoskeletal function. In the current paper, bond graph modules representing muscle function and rigid-body motions of underlying bone structures are introduced. The system equations generated with the use of these models are equivalent to those developed with more traditional techniques, but the modules can be more easily used in conjunction with control models of neuromuscular function for the simulation of overall dynamic motor performance.  相似文献   

优秀棒球投手的等速肌力与投球运动学参数间关联研究     

孙逊  罗炯  张庭然  秦春莉  宋吉祥 《成都体育学院学报》2016,(2):82-87

目的：：探讨棒球投手运动学与等速肌力参数间关联关系,并比较不同类型投手各类参数的差异性。方法：采用德国ISOMED2000等速肌力测试系统及三台高速摄像机获取相关参数。结果：( a)肩关节外、内旋峰力矩及屈、伸峰力矩两个比值高度相关,两者均与挥肘速度、棒球出手及触垒速度高度正相关;( b)与“非衡型”棒球投手相比,“均衡型”投手在许多关键参数上存有显著差异,表现为投球动作总时间、提膝时间、伸踏时间及动作加速时间显著变短;肘关节屈伸幅度、棒球出手等及触垒速度则显著增大;( c)挥肘速度与肩关节最大外展角存有显著正相关,而与投球动作总时间呈负相关;动作加速时间与肩关节最大外展角成负相关,却与躯干扭转角成正相关;( d)棒球出手及触垒速度均与肩关节最大外展角等呈显著正相关。结论：目前我国大学生优秀棒球投手与国外同级别投手相比,在众多运动学测试指标上存有显著差距,而投掷臂肌力发展不均衡是问题的关键所在。  相似文献   

Angle-specific knee muscle torques of ACL-reconstructed subjects and determinants of functional tests after reconstruction     

Özge Çınar-Medeni  Gulcan Harput  Gul Baltaci 《Journal of sports sciences》2019,37(6):671-676

The purposes of this study were to analyse (a) if “angle-specific” (AS) flexor and extensor torques were different between ACL-reconstructed and uninvolved limbs, (b) the difference in peak torque occurrence angles for concentric and eccentric knee flexor and extensor torques between involved and uninvolved limbs and (c) if AS concentric and eccentric knee flexor and extensor torques are determinants of performance in the “single-leg hop test” (SLHT) and “vertical jump and reach test” (VJRT) in ACL-reconstructed legs. Twenty-seven male ACL-reconstructed volunteers were included in the study. Isokinetic knee muscle strength, SLHT and VJRT were performed 6 months after ACL reconstruction. No difference was found in extremity and knee joint angle interaction for concentric and eccentric flexor and extensor torques (p > 0.05). Peak torque occurrence angles were not different between involved and uninvolved limbs (p > 0.05). In involved extremities, concentric knee extensor strength at 90° was a determinant of SLHT performance (R² = 0.403, p < 0.05), and concentric knee extensor strength at 60° was a determinant of VJRT (R² = 0.224, p < 0.05). Assessment of AS concentric knee extensor strength at 60° and 90° might be important, because these were determinants of functional test performance.  相似文献   

Exercise-induced muscle damage: What is it,what causes it and what are the nutritional solutions?     

Daniel J. Owens  Craig Twist  James N. Cobley  Glyn Howatson 《European Journal of Sport Science》2019,19(1):71-85

Abstract

Exercise-induced muscle damage (EIMD) is characterized by symptoms that present both immediately and for up to 14 days after the initial exercise bout. The main consequence of EIMD for the athlete is the loss of skeletal muscle function and soreness. As such, numerous nutrients and functional foods have been examined for their potential to ameliorate the effects of EIMD and accelerate recovery, which is the purpose of many nutritional strategies for the athlete. However, the trade-off between recovery and adaptation is rarely considered. For example, many nutritional interventions described in this review target oxidative stress and inflammation, both thought to contribute to EIMD but are also crucial for the recovery and adaptation process. This calls into question whether long term administration of supplements and functional foods used to target EIMD is indeed best practice. This rapidly growing area of sports nutrition will benefit from careful consideration of the potential hormetic effect of long term use of nutritional aids that ameliorate muscle damage. This review provides a concise overview of what EIMD is, its causes and consequences and critically evaluates potential nutritional strategies to ameliorate EIMD. We present a pragmatic practical summary that can be adopted by practitioners and direct future research, with the purpose of pushing the field to better consider the fine balance between recovery and adaptation and the potential that nutritional interventions have in modulating this balance.  相似文献   

男子健美运动员Heath-Carter体型特征及与肌力的相关性     

井兰香 《哈尔滨体育学院学报》2020,(2):23-28

目的:计算健美运动员Heath-Carter体型三因子值,统计三因子与肌肉力矩及输出功率的相关性,并分析影响因素。方法:确定60名男子健美运动员的体型类型;测量上、下肢及躯干肌的峰值屈、伸力矩;分别以2.5、5、7.5、10、12.5、15%体重比递增负荷完成自行车蹬车运动,记录每种负荷下的最大输出功率。结果:健美运动员体型三因子平均值为4.40-7.21-1.31(0.31-1.07-0.12),坐标值为(-3.11,8.61),属于远离外因子、偏内胚层的中胚层类型。肌肉力矩和输出功率均与内因子不相关,与中因子呈正相关,与外因子呈负相关。结论:中、外因子影响肌肉力矩和功率输出,对肌肉造型起主要作用。由于内因子值较高且与肌肉收缩能力并不相关,提示不宜将健美训练作为减脂的主要手段。  相似文献   

Upper limb and trunk muscle activity patterns during seated and standing cycling     

Nicolas A. Turpin  Antony Costes  Pierre Moretto  Bruno Watier 《Journal of sports sciences》2017,35(6):557-564

The objective of this study is to clarify the functional roles of upper limb muscles during standing and seated cycling when power output increases. We investigated the activity of seven upper limb and trunk muscles using surface electromyography (EMG). Power outputs ranged from ~100–700 W with a pedalling frequency of 90 revolution per minute. Three-dimensional handle and pedal forces were simultaneously recorded. Using non-negative matrix factorisation, we extracted muscle synergies and we analysed the integrated EMG and EMG temporal patterns. Most of the muscles showed tonic activity that became more phasic as power output increased. Three muscle synergies were identified, associated with (i) torso stabilisation, (ii) compensation/generation of trunk accelerations and (iii) upper body weight support. Synergies were similar for seated and standing positions (Pearson’s r > 0.7), but synergy #2 (biceps brachii, deltoidus and brachioradialis) was shifted forward during the cycle (~7% of cycle). The activity levels of synergy #1 (latissimus dorsi and erector spinae) and synergy #2 increased markedly above ~500 W (i.e., ~+40–70% and +130–190%) and during periods corresponding to ipsi- and contralateral downstrokes, respectively. Our study results suggest that the upper limb and trunk muscles may play important roles in cycling when high power outputs are required.  相似文献