分析人体跑、跳、投等与反向动作、“Plyometric”的关系,并以下肢为例从生物力学视角对肌肉收缩的“拉长—缩短周期”(stretch-shortening sycle,SSC)运动的预激活时期、离心收缩期、离心—向心耦联期、向心收缩期四个运动时相进行了...分析人体跑、跳、投等与反向动作、“Plyometric”的关系,并以下肢为例从生物力学视角对肌肉收缩的“拉长—缩短周期”(stretch-shortening sycle,SSC)运动的预激活时期、离心收缩期、离心—向心耦联期、向心收缩期四个运动时相进行了探讨和述评,介绍SSC理论的起源以及相应的生物力学机制,且分析SSC运动与“残余力量增加”(residual force enhancement,RFE)和“残余力量抑制”(residual force depression,RFD)的关系。同时,搜集、整理和追溯“Plyometric”一词的来源,归纳并梳理其在国内爆发力训练理论研究领域的翻译历程,阐述快速伸缩复合训练(plyometric training,PT)导入的生物力学原则。旨在加强教练员、运动员以及广大体育工作者对SSC运动理论的认识,了解PT训练的生物力学原理,为各专项运动员爆发力训练提供一定理论依据和实际参考。展开更多
Background:The isometric steady-state following active lengthening is associated with greater torque production and lower activation,as measured by electromyographic activity(EMG),in comparison with a purely isometric...Background:The isometric steady-state following active lengthening is associated with greater torque production and lower activation,as measured by electromyographic activity(EMG),in comparison with a purely isometric contraction(ISO)at the same joint angle.This phenomenon is termed residual force enhancement(RFE).While there has been a great deal of research investigating the basic mechanisms of RFE,little work has been performed to understand the everyday relevance of RFE.The purpose of this study was to investigate whether neuromuscular control strategies differ between ISO and RFE by measuring torque steadiness of the human ankle plantar flexors.Methods:Following ISO maximal voluntary contractions in 12 males(25±4 years),an active lengthening contraction was performed at 15°/s over a 30°ankle excursion,ending at the same joint angle as ISO(5°dorsiflexion;RFE).Surface EMG of the tibialis anterior and soleus muscles was recorded during all tasks.Torque steadiness was determined as the standard deviation(SD)and coefficient of variation(CV)of the torque trace in the ISO and RFE condition during activation-matching(20%and 60%integrated EMG)and torque-matching(20%and 60%maximal voluntary contraction)experiments.Two-tailed,paired t tests were used,within subjects,to determine the presence of RFE/activation reduction(AR)and whether there was a difference in torque steadiness between ISO and RFE conditions.Results:During the maximal and submaximal conditions,there was 5%-9%RFE with a 9%-11%AR(p<0.05),respectively,with no difference in antagonist coactivation between RFE and ISO(p>0.05).There were no differences in SD and CV of the torque trace for the 20%and60%activation-matching or the 60%and maximal torque-matching trials in either the RFE or ISO condition(p>0.05).During the 20%torquematching trial,there were～37%higher values for SD and CV in the RFE as compared with the ISO condition(p<0.05).A significant moderate-to-strong negative relationship was identified between the reduction in torque steadiness follow展开更多
It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)...It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active stretch.Aside from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element theory.In this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle.Although by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.展开更多
Natural adult aging is associated with many functional impairments of the human neuromuscular system.One of the more observable alterations is the loss of contractile muscle mass,termed sarcopenia.The loss of muscle m...Natural adult aging is associated with many functional impairments of the human neuromuscular system.One of the more observable alterations is the loss of contractile muscle mass,termed sarcopenia.The loss of muscle mass occurs primarily due to a progressive loss of viable motor units,and accompanying atrophy of remaining muscle fibers.Not only does the loss of muscle mass contribute to impaired function in old age,but alterations in fiber type and myosin heavy chain isoform expression also contribute to weaker,slower,and less powerful contracting muscles.This review will focus on motor unit loss associated with natural adult aging,age-related fatigability,and the age-related differences in strength across contractile muscle actions.展开更多
文摘分析人体跑、跳、投等与反向动作、“Plyometric”的关系,并以下肢为例从生物力学视角对肌肉收缩的“拉长—缩短周期”(stretch-shortening sycle,SSC)运动的预激活时期、离心收缩期、离心—向心耦联期、向心收缩期四个运动时相进行了探讨和述评,介绍SSC理论的起源以及相应的生物力学机制,且分析SSC运动与“残余力量增加”(residual force enhancement,RFE)和“残余力量抑制”(residual force depression,RFD)的关系。同时,搜集、整理和追溯“Plyometric”一词的来源,归纳并梳理其在国内爆发力训练理论研究领域的翻译历程,阐述快速伸缩复合训练(plyometric training,PT)导入的生物力学原则。旨在加强教练员、运动员以及广大体育工作者对SSC运动理论的认识,了解PT训练的生物力学原理,为各专项运动员爆发力训练提供一定理论依据和实际参考。
基金supported by the Natural Sciences and Engineering Research Council of Canada
文摘Background:The isometric steady-state following active lengthening is associated with greater torque production and lower activation,as measured by electromyographic activity(EMG),in comparison with a purely isometric contraction(ISO)at the same joint angle.This phenomenon is termed residual force enhancement(RFE).While there has been a great deal of research investigating the basic mechanisms of RFE,little work has been performed to understand the everyday relevance of RFE.The purpose of this study was to investigate whether neuromuscular control strategies differ between ISO and RFE by measuring torque steadiness of the human ankle plantar flexors.Methods:Following ISO maximal voluntary contractions in 12 males(25±4 years),an active lengthening contraction was performed at 15°/s over a 30°ankle excursion,ending at the same joint angle as ISO(5°dorsiflexion;RFE).Surface EMG of the tibialis anterior and soleus muscles was recorded during all tasks.Torque steadiness was determined as the standard deviation(SD)and coefficient of variation(CV)of the torque trace in the ISO and RFE condition during activation-matching(20%and 60%integrated EMG)and torque-matching(20%and 60%maximal voluntary contraction)experiments.Two-tailed,paired t tests were used,within subjects,to determine the presence of RFE/activation reduction(AR)and whether there was a difference in torque steadiness between ISO and RFE conditions.Results:During the maximal and submaximal conditions,there was 5%-9%RFE with a 9%-11%AR(p<0.05),respectively,with no difference in antagonist coactivation between RFE and ISO(p>0.05).There were no differences in SD and CV of the torque trace for the 20%and60%activation-matching or the 60%and maximal torque-matching trials in either the RFE or ISO condition(p>0.05).During the 20%torquematching trial,there were～37%higher values for SD and CV in the RFE as compared with the ISO condition(p<0.05).A significant moderate-to-strong negative relationship was identified between the reduction in torque steadiness follow
文摘It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active stretch.Aside from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element theory.In this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle.Although by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.
基金supported by an operating grant to Dr.Charles Rice from the Natural Sciences and Engineering Research Council of Canada (NSERC)supported by the Canadian Institutes of Health Research (CIHR)+1 种基金the Michael Smith Foundation for Health Research (MSFHR)supported by Alberta Innovates Health Solutions (AIHS)
文摘Natural adult aging is associated with many functional impairments of the human neuromuscular system.One of the more observable alterations is the loss of contractile muscle mass,termed sarcopenia.The loss of muscle mass occurs primarily due to a progressive loss of viable motor units,and accompanying atrophy of remaining muscle fibers.Not only does the loss of muscle mass contribute to impaired function in old age,but alterations in fiber type and myosin heavy chain isoform expression also contribute to weaker,slower,and less powerful contracting muscles.This review will focus on motor unit loss associated with natural adult aging,age-related fatigability,and the age-related differences in strength across contractile muscle actions.
