Strength training: Isometric training at a range of joint angles versus dynamic training

Strength training with isometric contractions produces large but highly angle-specific adaptations. To contrast the contractile mode of isometric versus dynamic training, but diminish the strong angle specificity effect, we compared the strength gains produced by isometric training at four joint angles with conventional dynamic training. Thirty-three recreationally active healthy males aged 18?–?30 years completed 9 weeks of strength training of the quadriceps muscle group three times per week. An intra-individual design was adopted: one leg performed purely isometric training at each of four joint angles (isometrically trained leg); the other leg performed conventional dynamic training, lifting and lowering (dynamically trained leg). Both legs trained at similar relative loads for the same duration. The quadriceps strength of each leg was measured isometrically (at four angles) and isokinetically (at three velocities) pre and post training. After 9 weeks of training, the increase in isokinetic strength was similar in both legs (pooled data from three velocities: dynamically trained leg, 10.7%; isometrically trained leg, 10.5%). Isometric strength increases were significantly greater for the isometrically trained leg (pooled data from four angles: dynamically trained leg, 13.1%; isometrically trained leg, 18.0%). This may have been due to the greater absolute torque involved with isometric training or a residual angle specificity effect despite the isometric training being divided over four angles.     

Effects of isometric quadriceps strength training at different muscle lengths on dynamic torque production

This study aims to (1) determine whether isometric training at a short vs. long quadriceps muscle length affects concentric torque production; (2) examine the relationship between muscle hypertrophy and concentric torque; and (3) determine whether changes in fascicle length are associated with changes in concentric torque.

Sixteen men performed isometric training at a short (SL, n = 8) or a long muscle length (LL, n = 8). Changes in maximal concentric torque were measured at 30, 60, 90, 120, 180, 240 and 300 rad · s^?1. The relationships between the changes in concentric torque, cross-sectional area, volume and fascicle length were tested.

Concentric torque increased significantly after training only in LL and at angular velocities of 30 and 120 rad · s^?1 by 12–13% (P < 0.05). Muscle size increased in LL only, the changes were correlated (r = 0.73–0.93, P < 0.05) with the changes in concentric torque. Vastus lateralis (VL) fascicle length increased in both groups (5.4 ± 4.9%, P = 0.001) but the change was not correlated with changes in concentric torque in either group.

Isometric training-induced increases in muscle size and concentric torque were best elicited by training at long muscle lengths. These results highlight a clear muscle length dependence of isometric training on dynamic torque production.     

Effects of dynamic resistance training on fascicle length and isometric strength

The aims of this study were to assess changes in muscle architecture, isometric and dynamic strength of the leg extensor muscles, resulting from dynamic resistance training, and the relationships between strength and muscle architecture variables. The participants (n = 30) were randomly assigned to one of two groups. The training group (n = 16; age 21.8 +/- 2.3 years, body mass 74.8 +/- 9.2 kg, height 1.75 +/- 0.08 m) performed dynamic resistance training for 13 weeks. The control group (n = 14; age 19.9 +/- 1.5 years, body mass 74.0 +/- 8.5 kg, height 1.76 +/- 0.05 m) did not perform any resistance training. Maximal dynamic and isometric strength were tested in both groups, before and after the training period. The members of the training group used the free-weight squat lift (90 degrees ) as their training exercise. The concentric phase of the squat was performed explosively. Skeletal muscle architecture of the vastus lateralis was visualized using ultrasonography. At the end of the study, significant increases in vastus lateralis muscle thickness (+6.9%, P < 0.001), fascicle length (+10.3%, P < 0.05), one-repetition maximum (+8.2%, P < 0.05), rate of force development (+23.8%, P < 0.05) and average force produced in the first 500 ms (+11.7%, P < 0.05) were seen only in the training group. Adaptations to the muscle architecture in the training group limited the loss of fibre force, and improved the capacity for developing higher velocities of contraction. The architectural changes in the training group were similar to those seen in studies where high-speed training was performed. In conclusion, dynamic resistance training with light loads leads to increases in muscle thickness and fascicle length, which might be related to a more efficient transmission of fibre force to the tendon.     

Effects of low volume isometric leg press complex training at two knee angles on force-angle relationship and rate of force development

This study compared knee angle-specific neuromuscular adaptations after two low-volume isometric leg press complex training programmes performed at different muscle lengths. Fifteen young males were divided into two groups and trained three times per week for 6 weeks. One group (n?=?8) performed 5–7 sets of 3 s maximum isometric leg press exercise, with 4?min recovery, with knee angle at 85°?±?2° (longer muscle-tendon unit length; L-MTU). The other group (n?=?7) performed the same isometric training at a knee angle of 145°?±?2° (180°^?=?full extension; shorter muscle-tendon unit length; S-MTU). During the recovery after each set of isometric exercise, participants performed two CMJ every minute, as a form of complex training. Maximum isometric force (MIF) and rate of force development (RFD) were measured over a wide range of knee angles. Countermovement jump (CMJ) performance and maximum half-squat strength (1RM) were also assessed. Training at S-MTU induced a large increase of MIF (22–58%, p?p?p?=?0.001). In contrast, training at L-MTU, resulted in a moderate and similar (≈12.3%, p?=?0.028) improvement of force at all knee angles. CMJ performance and 1RM were equally increased in both groups after training by 10.4%?±?8.3% and 7.8%?±?4.7% (p?相似文献   

动态平衡训练对膝关节位置觉干预效果的研究

目的:研究动态平衡训练对膝关节位置觉的干预效果及其预防损伤机制,比较平衡板、平衡气囊、瑞士球训练方法改善下肢本体感觉功能的效果,为预防运动损伤提供理论依据和实践指导.方法:41名受试者分成平衡板平衡气囊训练组(n=13),瑞士球训练组(n=14),对照组(n=14),训练时间共8周,每周3次,每次练习50分钟,8周训练前后测试膝关节主动和被动位置觉.结果:①8周平衡板气囊训练和瑞士球训练后,男女受试者右膝关节位置觉(主动和被动)比训练前减小但无显著性差异(P＞0.05);②平衡板气囊组与瑞士球组在改善膝关节位置觉无显著差异(P ＞0.05).结论:8周动态平衡训练时间较短不足以使膝关节位置觉显著改变,但训练后位置觉平均误差减小,表明平衡板气囊训练和瑞士球训练对改善膝关节位置觉感知能力有积极意义.     

Effects of dynamic upper-body exercise on lower-limb isometric endurance

Following preliminary indications that in some individuals arm exercise enhanced rather than reduced simultaneous leg endurance, ten young men and women performed three forms of intermittent work to volitional exhaustion, under duty cycles of 45 s work, 15 s rest. The protocols were as follows: (A) knee extensions at 30% maximum voluntary contraction (MVC); (B) 30% MVC knee extensions combined with arm cranking at 130% of their own lactate threshold; (C) combined 30% MVC knee extensions and arm cranking at 20% of their own lactate threshold. Heart rate, oxygen uptake (VO(2)), and blood lactate concentration were among the variables recorded throughout. All physiological indicators of demand were substantially higher in protocol B than in protocols A or C [heart rate: (A) 154 beats . min(-1), (B) 171 beats . min(-1), (C) 150 beats . min(-1); VO(2): (A) 11.9 ml . kg(-1) . min(-1), (B) 21.7 ml . kg(-1) . min(-1), (C) 14.2 ml . kg(-1) . min(-1); blood lactate concentration: (A) 3.3 mmol . l(-1), (B) 5.1 mmol . l(-1), (C) 2.8 mmol . l(-1)], yet there were no significant differences (P > 0.05) in the endurance times between the three conditions [(A) 11.43 min, (B) 11.1 min, (C) 10.57 min] and seven participants endured longest in protocol B. Results from protocol (C) cast doubt on explanations in terms of psychological distraction. We suggest that lactic acid produced by the arms is shuttled to the legs and acts there either as a supplementary fuel source or as an antagonist to the depressing effects of increased potassium concentration.     

训练学视角下短跑运动员力量训练的思考

力量素质是短跑运动员最重要的身体素质,也是短跑训练最重要的组成部分.但是,目前我国在力量素质的宏观训练思想和具体训练方法方面认识不足,已经对我国短跑运动的发展产生严重的制约作用.以训练学视角,运用文献资料法、专家调查法、逻辑分析法分析了短跑力量训练应遵循的基本原理和规律,在此基础上指出目前短跑力量训练中存在的问题,进一步提出短跑力量训练中的若干对策,希望对中国短跑运动员备战2012年英国伦敦奥运会有一定的启示.     

艺术体操运动员的力量训练

艺术体操对弹跳力、腰腿的控制力(如向前、向侧和向后的控腿，各种平衡和转体)具有特殊的要求。良好的力量素质使艺术体操运动员跳得高、站得稳，而且幅度大、动作美。     

Markers of isometric training intensity and reductions in resting blood pressure

Abstract

In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torque_peak) and peak heart rate peak (HR_peak) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HR_peak), heart rate (HR_train), torque (Torque_train), and changes in EMG amplitude (ΔEMG_amp) and frequency (ΔEMG_freq) were determined. The markers of training intensity were: Torque_train relative to the 2min-torque_peak (%2min-torque_peak), EMG relative to EMG_peak (%EMG_peak), HR_train ΔEMG_amp, ΔEMG_freq, and %MVC. Mean systolic (?4.9 mmHg) and arterial blood pressure (?2.7mmHg) reductions correlated with %2min-torque_peak (r = ?0.65, P = 0.02 and r = ?0.59, P = 0.03), ΔEMG_amp (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMG_freq (r = ?0.67, P = 0.01 and r = ?0.64, P = 0.02), and %EMG_peak (systolic blood pressure only; r = ?0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.     

Markers of isometric training intensity and reductions in resting blood pressure

In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torque(peak)) and peak heart rate peak (HR(peak)) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4?×?2?min bilateral leg isometric exercise at 95% HR(peak)), heart rate (HR(train)), torque (Torque(train)), and changes in EMG amplitude (ΔEMG(amp)) and frequency (ΔEMG(freq)) were determined. The markers of training intensity were: Torque(train) relative to the 2min-torque(peak) (%2min-torque(peak)), EMG relative to EMG(peak) (%EMG(peak)), HR(train) ΔEMG(amp), ΔEMG(freq), and %MVC. Mean systolic (-4.9 mmHg) and arterial blood pressure (-2.7mmHg) reductions correlated with %2min-torque(peak) (r?=?-0.65, P?=?0.02 and r?=?-0.59, P?=?0.03), ΔEMG(amp) (r?=?0.66, P?=?0.01 and r?=?0.59, P?=?0.03), ΔEMG(freq) (r?=?-0.67, P?=?0.01 and r?=?-0.64, P?=?0.02), and %EMG(peak) (systolic blood pressure only; r?=?-0.63, P?=?0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.     

The effect of short-term isometric training on core/torso stiffness

“Core” exercise is a basic part of many physical training regimens with goals ranging from rehabilitation of spine and knee injuries to improving athletic performance. Core stiffness has been proposed to perform several functions including reducing pain by minimising joint micro-movements, and enhancing strength and speed performance. This study probes the links between a training approach and immediate but temporary changes in stiffness. Passive and active stiffness was measured on 24 participants; 12 having little to no experience in core training (inexperienced), and the other 12 being athletes experienced to core training methods; before and after a 15 min bout of isometric core exercises. Passive stiffness was assessed on a “frictionless” bending apparatus and active stiffness assessed via a quick release mechanism. Short-term isometric core training increased passive and active stiffness in most directions for both inexperienced and experienced participants, passive left lateral bend among experienced participants being the exception (P < 0.05). There was no difference between the inexperienced and experienced groups. The results confirm that the specific isometric training exercise approach tested here can induce immediate changes in core stiffness, in this case following a single session. This may influence performance and injury resilience for a brief period.     

优秀越野滑雪运动员的力量训练

优秀越野滑雪运动员提高竞技水平重要途径之一是长期有效系统地进行力量训练。针对我国越野滑雪传统教学训练中普遍存在的问题,论述越野滑雪力量训练的目的、特点,以及方法手段,旨在促进我国越野滑雪运动水平的尽快提高。     

The effects of imagery training on fast isometric knee extensor torque development

Abstract

We hypothesized that imagery training would improve the fast onset of neuromuscular activation and thereby fast knee extensor isometric torque development. Forty young healthy participants, not involved in strength training, were assigned to one of four groups: physical training, imagery training, placebo training or control. The three training groups had three 15 min sessions per week for 4 weeks, with a 90° knee angle but were tested also at 120°. At 90° knee angle, maximal torque increased (～8%) similarly in all three training groups. The torque–time integral (contractile impulse) over the first 40 ms after torque onset (TTI40) increased (P < 0.05) after physical training (by ～100%), but only at 90°. This increase was significantly different from the delta values (change pre to post) in the control and placebo groups, whereas delta values in the imagery group were similar to those in the placebo group. The increases in TTI40 following physical training were related (r ² = 0.81, P < 0.05) to significant increases of knee extensor rectified surface EMG at torque onset (EMG40). In conclusion, only physical training led to a knee angle specific increase of contractile impulse that was significantly different from placebo and controls and that was related to improved onset of neuromuscular activation.     

The effects of imagery training on fast isometric knee extensor torque development

We hypothesized that imagery training would improve the fast onset of neuromuscular activation and thereby fast knee extensor isometric torque development. Forty young healthy participants, not involved in strength training, were assigned to one of four groups: physical training, imagery training, placebo training or control. The three training groups had three 15 min sessions per week for 4 weeks, with a 90 ° knee angle but were tested also at 120 °. At 90 ° knee angle, maximal torque increased (-8%) similarly in all three training groups. The torque-time integral (contractile impulse) over the first 40 ms after torque onset (TTI40) increased (P < 0.05) after physical training (by -100%), but only at 90 °. This increase was significantly different from the delta values (change pre to post) in the control and placebo groups, whereas delta values in the imagery group were similar to those in the placebo group. The increases in TTI40 following physical training were related (r (2) = 0.81, P < 0.05) to significant increases of knee extensor rectified surface EMG at torque onset (EMG40). In conclusion, only physical training led to a knee angle specific increase of contractile impulse that was significantly different from placebo and controls and that was related to improved onset of neuromuscular activation.     

远距离单手肩上投篮训练方法探讨

讨论影响投篮命中率有7个因素:手法、瞄准的方向、球的旋转、抛物线、协调性、判断反应和心理因素,并提出提高远距离投篮命中率的训练方法.     

Glenohumeral joint rotation range of motion in competitive swimmers

Much research has examined shoulder range of motion adaptations in overhead-unilateral athletes. Based on the void examining overhead-bilateral athletes, especially competitive swimmers, we examined shoulder external rotation, isolated internal rotation, composite internal rotation, and total arc of motion range of motion of competitive swimmers. The range of motion of registered competitive swimmers (n = 144, age = 12-61 years) was compared by limb (dominant, non-dominant), sex, and age group (youth, high school, college, masters). Significantly (P < 0.05) greater dominant external rotation was observed for both men and women high school and college swimmers, youth women swimmers, and men masters swimmers compared with the non-dominant limb. The isolated internal rotation (glenohumeral rotation), composite internal rotation (glenohumeral rotation plus scapulothoracic protraction), and total arc of motion (external rotation plus composite internal rotation) of the non-dominant limb was significantly greater than that of the dominant limb by sex and age group. Youth and high school swimmers demonstrated significantly greater composite internal rotation than college and masters swimmers. Youth swimmers displayed significantly greater total arc of motion than all other age groups. These data will aid in the interpretation of shoulder range of motion values in competitive swimmers during preseason screenings, injury evaluations and post-rehabilitation programmes, with the results suggesting that differences exist in bilateral external rotation, isolated internal rotation, composite internal rotation, and total arc of motion range of motion.     

高校铁饼运动员力量素质的训练方法

高校铁饼比赛不是单一的技术与力量的竞争，而是技术、体能与心理状态等方面的综合较量，是运动员力量素质在比赛中的充分发挥。因而，运动员力量素质的训练是各种训练活动的关键。论述了铁饼运动员进行力量训练的方法。     

少年儿童身体发育特征及力量训练

分析了少年儿童身体发育的特点,阐述了少年儿童身体力量训练的特点,提出了少年儿童力量训练的原则：逐渐增加负荷和超负荷的原则,负荷顺序的原则,专门性原则,合理的训练间隔原则,稳定肌群优先发展的原则,全面性原则,经常性原则,整体控制的训练负荷的原则,及身体力量训练中应注意的事项。     

基于“Plyometrics”理论的WCBA运动员力量训练

"Plyometrics"练习是一种把退让练习和克制练习结合在一起的训练方法,对提高运动员爆发力有着重要的作用,对运动员的基础力量也有要求.WCBA教练员对运动员的力量要求偏低;WCBA运动员无论是上肢的卧推,还是下肢的深蹲都不能达到"Plyometries"练习理论上的要求.在此力量的基础上,WCBA运动员应较多地进行"Upper Body Plyometrics"练习,有利于运动员爆发力和灵敏性的提高.对有下肢肌腱劳损的WCBA运动员,也可进行"Upper Body Plyometrics"练习,提高其爆发力.