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1.
The purpose of this study was to compare the power expressed during the bench press exercise in resistance-trained men following different pre-activation conditions. Twenty-two trained men (age 24.1?±?1.7 years, height 178.6?±?6.1?cm, body mass 81.1?±?10.6?kg) completed a maximal effort bench press (1-RM) test (100.0?kg?±?8.1?kg). In a subsequent assessment, each participant performed concentric bench press movements with loads of 20%, 30%, 40% and 50% of their 1-RM preceded by either a concentric contraction (CC), a low isometric preload (LIP; 70% 1-RM) or a high isometric preload (HIP; 100% 1-RM) conditions. All movements were performed in a Smith machine with a settable quick-release device. Participants performed all three conditions in randomized fashion. Results indicated that power outputs during the bench press exercise following HIP were significantly (p?<?0.05) greater than CC at 20% 1-RM (+9%), 30% 1-RM (+16%) and 40% 1-RM (+14%), and LIP at 20% 1-RM (+4%), 30% 1-RM (+20%) and 40% 1-RM (+15%). No differences were found between conditions at 50% 1-RM. Area under the force–power curve with HIP was greater (p?<?0.05) than with CC and LIP. In conclusion, results of this study indicate that the use of a HIP (100% 1-RM) in trained participants results in significantly greater power output during the concentric phase of a multi-joint exercise when compared to standard concentric movement.  相似文献   

2.
This investigation examined effects of two exercise modes (barbell, BB; bodyweight suspension, BWS) on muscle activation, resistance load, and fatigue. During session one, nine resistance-trained males completed an elbow flexion one-repetition maximum (1RM). During sessions two and three, subjects completed standing biceps curls to fatigue at 70% 1RM utilizing a randomized exercise mode. Surface electromyography (sEMG) recorded muscle activation of the biceps brachii, triceps brachii, anterior deltoid, posterior deltoid, rectus abdominis, and erector spinae. BWS resistance load was measured using a force transducer. Standing maximal voluntary isometric contractions of the elbow flexors recorded at 90° were used to determine the isometric force decrement and rate of fatigue (ROF) during exercise. sEMG and resistance load data were divided into 25% contraction duration bins throughout the concentric phase. BWS resulted in a 67.7?±?7.4% decline in resistance load throughout the concentric phase (p?≤?0.05). As a result, BB elicited higher mean resistance loads (31.4?±?4.0?kg) and biceps brachii sEMG (84.7?±?27.8% maximal voluntary isometric contractions, MVIC) compared with BWS (20.4?±?3.4?kg, 63.4?±?21.6% MVIC). No difference in rectus abdominis or erector spinae sEMG was detected between exercise modes. Isometric force decrement was greater during BWS (?21.7?±?7.0?kg) compared with BB (?14.9?±?4.7?kg); however, BB (?3.0?±?0.8?kg/set) resulted in a steeper decline in ROF compared with BWS (?1.7?±?0.6?kg/set). The variable resistance loading and greater isometric force decrement observed suggest that select BWS exercises may resemble variable resistance exercise more than previously considered.  相似文献   

3.
Abstract

The aim of the study was to examine the sticking region and concomitant neuromuscular activation of the prime movers during six-repetition maximum (RM) bench pressing. We hypothesised that both peak velocities would decrease and that the electromyography (EMG) of the prime movers (deltoid, major pectoralis and triceps) would increase during the pre-sticking and sticking region during the six repetitions due to fatigue. Thirteen resistance-trained males (age 22.8 ± 2.2 years, stature 1.82 ± 0.06 m, body mass 83.4 ± 7.6 kg) performed 6-RM bench presses. Barbell kinematics and EMG activity of pectoralis major, deltoid anterior, and triceps brachii during the pre-, sticking and post-sticking region of each repetition in a 6-RM bench press were analysed. For both the sticking as the post-sticking region, the time increased significantly from the first to the sixth repetition. Vertical barbell height at the start of sticking region was lower, while the height at the end of the sticking region and post-sticking region did not change during the six repetitions. It was concluded that in 6-RM bench pressing performance, the sticking region is a poor mechanical force region due to the unchanged barbell height at the end of the sticking region. Furthermore, when fatigue occurs, the pectoralis and the deltoid muscles are responsible for surpassing the sticking region as indicated by their increased activity during the pre- and sticking region during the six-repetitions bench press.  相似文献   

4.
The purpose of this study was to investigate whether using different focus affects electromyographic (EMG) amplitude and contraction duration during bench press performed at explosive and controlled speeds. Eighteen young male individuals were familiarized with the procedure and performed the one-maximum repetition (1RM) test in the first session. In the second session, participants performed the bench press exercise at 50% of the 1RM with 3 different attentional focuses (regular focus on moving the load vs contracting the pectoralis vs contracting the triceps) at 2 speed conditions (controlled vs maximal speed). During the controlled speed condition, focusing on using either the pectoralis or the triceps muscles increased pectoralis normalized EMG (nEMG) by 6% (95% CI 3–8%; p = 0.0001) and 4% nEMG (95% CI 1–7%; p = 0.0096), respectively, compared with the regular focus condition. Triceps activity was increased by 4% nEMG (95% CI 0–7%; p = 0.0308) at the controlled speed condition during the triceps focus. During the explosive speed condition, the use of different focuses had no effect. The different attentional focus resulted in comparable contraction duration for the measured muscles when the exercise was performed explosively. Using internal focus to increase EMG amplitude seems to function only during conditions of controlled speed.  相似文献   

5.
Abstract

The purpose of this study was to examine the relationships among mechanomyographic (MMG) amplitude, power output, and bar velocity during the free-weight bench press exercise. Twenty-one resistance-trained men [one-repetition maximum (1-RM) bench press = 125.4 ± 18.4 kg] performed bench press muscle actions as explosively as possible from 10% to 90% of the 1-RM while peak power output and peak bar velocity were assessed with a TENDO Weightlifting Analyzer. During each muscle action, surface MMG signals were detected from the right and left pectoralis major and triceps brachii, and the concentric portion of the range of motion was selected for analysis. Results indicated that power output increased from 10% to 50% 1-RM, followed by decreases from 50% to 90% 1-RM, but MMG amplitude for each of the muscles increased from 10 to 80%1-RM. The results of this study indicate that during the free-weight bench press exercise, MMG amplitude was not related to power output, but was inversely related to bar velocity and directly related to the external load being lifted. In future research, coaches and sport scientists may be able to estimate force/torque production from individual muscles during multi-joint, dynamic constant external resistance muscle actions.  相似文献   

6.
ABSTRACT

The velocity and magnitude in which the eccentric phase of an exercise is completed directly affects performance during the concentric phase. Therefore, the purpose of this research was to investigate the effects of eccentric phase duration on concentric outcomes at 60% and 80% of one-repetition maximum (1RM) in the squat and bench press. Sixteen college-aged, resistance-trained males completed 1RM testing, established normative eccentric durations, and performed fast (0.75 times normative) and slow (2.0 times normative) metronome-controlled eccentric duration repetitions. Outcome measures assessed during the concentric phase were: average concentric velocity (ACV), peak concentric velocity (PCV), rating of perceived exertion (RPE), range of motion (ROM), and barbell path. Eccentric duration was significantly and inversely correlated with ACV at 60% (r = ?0.408, p = 0.004) and 80% (r = ?0.477, p = 0.001) of 1RM squat. At 60% of 1RM squat, both fast and slow eccentric conditions produced greater (p < 0.001) PCV than normative duration with fast also producing greater PCV than slow (p = 0.044). Eccentric duration had no impact on RPE, ROM, or barbell path. Our results report for the first time that resistance-trained males performing a deliberately faster eccentric phase may enhance their own squat and bench press performance.  相似文献   

7.
The aims of this study were to describe muscular activation patterns and kinematic variables during the complete stroke cycle (SC) and the different phases of breaststroke swimming at submaximal and maximal efforts. Surface electromyography (sEMG) was collected from eight muscles in nine elite swimmers; five females (age 20.3 ± 5.4 years; Fédération Internationale de Natation [FINA] points 815 ± 160) and four males (27.7 ± 7.1 years; FINA points 879 ± 151). Underwater cameras were used for 3D kinematic analysis with automatic motion tracking. The participants swam 25 m of breaststroke at 60%, 80% and 100% effort and each SC was divided into three phases: knee extension, knee extended and knee flexion. With increasing effort, the swimmers decreased their SC distance and increased their velocity and stroke rate. A decrease during the different phases was found for duration during knee extended and knee flexion, distance during knee extended and knee angle at the beginning of knee extension with increasing effort. Velocity increased for all phases. The mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the SC and increased integrated sEMG (except trapezius) with increasing effort. The muscle activation patterns, muscular participation and kinematics assessed in this study with elite breaststroke swimmers contribute to a better understanding of the stroke and what occurs at different effort levels. This could be used as a reference for optimising breaststroke training to improve performance.  相似文献   

8.
The aim of the study was to quantify the activation of arm and shoulder muscles during a static therapeutic climbing exercise and to investigate the possibility of altering the muscle activation through arm position (Jug, Undercling, Sidepull internal rotated, Sidepull external rotated), hand support (one-handed, double-handed) and wall inclination (0°, 12°). Electromyographic (EMG) activity of 14 healthy, climbing unexperienced males for the right m. biceps brachii (BB), m. serratus anterior (SA), m. upper, middle and lower trapezius (UT, MT, LT) showed mainly low to moderate EMG activation levels (BB: 4.1–40.1% maximum voluntary isometric contraction (MVIC), SA: 4.5–24.5% MVIC, UT: 1.3–28.0% MVIC, MT: 8.6–47.1% MVIC, LT: 3.8–47.3% MVIC). Significant differences occurred between the four arm positions for the UT and LT. The one-handed support revealed significant higher muscle activation than the double-handed support in every condition except for SA in Undercling arm position at 12° wall inclination. Increasing the wall inclination (from 0° to 12° overhang) led to a significant increase in muscle activation in nearly every exercise variation and muscle. These findings suggest that arm position, hand support and wall inclination are appropriate possibilities of altering muscle activation patterns in therapeutic climbing.  相似文献   

9.
Understanding how loading affects power production in resistance training is a key step in identifying the most optimal way of training muscular power – an essential trait in most sporting movements. Twelve elite male sailors with extensive strength-training experience participated in a comparison of kinematics and kinetics from the upper body musculature, with upper body push (bench press) and pull (bench pull) movements performed across loads of 10–100% of one repetition maximum (1RM). 1RM strength and force were shown to be greater in the bench press, while velocity and power outputs were greater for the bench pull across the range of loads. While power output was at a similar level for the two movements at a low load (10% 1RM), significantly greater power outputs were observed for the bench pull in comparison to the bench press with increased load. Power output (P max) was maximized at higher relative loads for both mean and peak power in the bench pull (78.6 ± 5.7% and 70.4 ± 5.4% of 1RM) compared to the bench press (53.3 ± 1.7% and 49.7 ± 4.4% of 1RM). Findings can most likely be attributed to differences in muscle architecture, which may have training implications for these muscles.  相似文献   

10.
The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE), and pain perception (PP) in resistance-trained men. Seventeen volunteers (mean?±?SD: age?=?26?±?6 years, stature?=?182?±?9?cm, body mass?=?84?±?9?kg, resistance training experience?=?7?±?3 years) consumed placebo or 6?mg?kg?1 of anhydrous caffeine 1?h before testing. Muscular power was assessed with seated medicine ball throw and vertical jump exercises, muscular strength with one-repetition maximum (1RM) barbell back squat and bench press exercises, and muscular endurance with repetitions of back squat and bench press exercises (load corresponding to 60% of 1RM) to momentary muscular failure. RPE and PP were assessed immediately after the completion of the back squat and bench press exercises. Compared to placebo, caffeine intake enhanced 1RM back squat performance (+2.8%; effect size [ES]?=?0.19; p?=?.016), which was accompanied by a reduced RPE (+7%; ES?=?0.53; p?=?.037), and seated medicine ball throw performance (+4.3%, ES?=?0.32; p?=?.009). Improvements in 1RM bench press were not noted although there were significant (p?=?.029) decreases in PP related to this exercise when participants ingested caffeine. The results point to an acute benefit of caffeine intake in enhancing lower-body strength, likely due to a decrease in RPE; upper-, but not lower-body power; and no effects on muscular endurance, in resistance-trained men. Individuals competing in events in which strength and power are important performance-related factors may consider taking 6?mg?kg?1 of caffeine pre-training/competition for performance enhancement.  相似文献   

11.
The present study assessed neuromuscular and corticospinal changes during and after a fatiguing submaximal exercise of the knee extensors in different modes of muscle contraction. Twelve subjects performed two knee extensors exercises in a concentric or eccentric mode, at the same torque and with a similar total impulse. Exercises consisted of 10 sets of 10 repetitions at an intensity of 80% of the maximal voluntary isometric contraction torque (MVIC). MVIC, maximal voluntary activation level (VAL) and responses of electrically evoked contractions of the knee extensors were assessed before and after exercise. Motor evoked potential amplitude (MEP) and cortical silent period (CSP) of the vastus medialis (VM) and rectus femoris (RF) muscles were assessed before, during and after exercise. Similar reductions of the MVIC (?13%), VAL (?12%) and a decrease in the peak twitch (?12%) were observed after both exercises. For both VM and RF muscles, MEP amplitude remained unchanged during either concentric or eccentric exercises. No change of the MEP amplitude input–output curves was observed post-exercise. For the RF muscle, CSP increased during the concentric exercise and remained lengthened after this exercise. For the VM muscle, CSP was reduced after the eccentric exercise only. For a similar amount of total impulse, concentric and eccentric knee extensor contractions led to similar exercise-induced neuromuscular response changes. For the two muscles investigated, no modulation of corticospinal excitability was observed during or after either concentric or eccentric exercises. However, intracortical inhibition showed significant modulations during and after exercise.  相似文献   

12.
目的：探讨肌肉疲劳后，被动(Passive Recovery，PR)、主动(Active Recovery，AR)、振动(Vibration Recovery，VR)和冰敷(Cryotherapy Recovery，CR)等不同恢复方式对肌肉表现(最大肌力MVC、爆发力MP、肌肉激活程度sEMG)和力学特性(肌肉硬度MS、肿胀程度SD)的影响及差异。方法：20名身体健康的普通男性大学生为受试者，平均年龄(20.4±2.3 yrs.)，平均身高(173.5±3.4 cm)，平均体重(68.7±3.9 kg)。先测量非惯用手肱二头肌的SD、MS、MVC和sEMG，之后进行肘关节屈曲45°/s向心与离心收缩运动直至疲劳，再进行后测。其后以随机方式进行其中1种恢复，10 min恢复后立即进行后测，各恢复方式间隔7天。以单因素重复测量方差分析检验SD、MS、MVC和sEMG在不同检测时间点的差异及恢复效果。结果：10 min VR和CR均有约15%的力量恢复效果，其中VR介入后sEMG的恢复效果显著高达(32.50±16.10%)。另外，CR可以缓解疲劳后的SD，但AR后SD(28.51±2.79 cm)显著高于疲劳前(27.93±2.93 cm)，且MS(11.14±1.58 mm/2kg)相较于疲劳后(11.59±1.40 mm/2kg)也显著下降。结论：CR与VR均可有效帮助疲劳后的肌力恢复，2组间恢复效果无显著差异；同比之下AR则无法改善肌肉疲劳的恢复，甚至造成SD增加且MS降低。  相似文献   

13.
This study examined the effect of hypoxia on growth hormone (GH) release during an acute bout of high-intensity, low-volume resistance exercise. Using a single-blinded, randomised crossover design, 16 resistance-trained males completed two resistance exercise sessions in normobaric hypoxia (HYP; inspiratory oxygen fraction, (FiO2) 0.12, arterial oxygen saturation (SpO2) 82?±?2%) and normoxia (NOR; FiO2 0.21, SpO2 98?±?0%). Each session consisted of five sets of three repetitions of 45° leg press and bench press at 85% of one repetition maximum. Heart rate, SpO2, and electromyographic activity (EMG) of the vastus lateralis muscle were measured throughout the protocol. Serum lactate and GH levels were determined pre-exposure, and at 5, 15, 30 and 60?min post-exercise. Differences in mean and integrated EMG between HYP and NOR treatments were unclear. However, there was an important increase in the peak levels and area under the curve of both lactate (HYP 5.8?±?1.8 v NOR 3.9?±?1.1?mmol.L?1 and HYP 138.7?±?33.1 v NOR 105.8?±?20.8?min.mmol.L?1) and GH (HYP 4.4?±?3.1 v NOR 2.1?±?2.5?ng.mL?1 and HYP 117.7?±?86.9 v NOR 72.9?±?85.3?min.ng.mL?1) in response to HYP. These results suggest that performing high-intensity resistance exercise in a hypoxic environment may provide a beneficial endocrine response without compromising the neuromuscular activation required for maximal strength development.  相似文献   

14.
通过高速摄影、表面肌电图（sEMG）测量以及等速肌力测试等方法对12名体育专业男生进行研究，获取踝关节主要屈伸肌（胫骨前肌和腓肠肌）等速肌力与sEMG之间的关系，以此说明用sEMG来直接评价肌肉用力情况时需进行标准化的必要性及最佳标准化方式。结果表明：相同肌肉收缩过程中，肌力矩值与平均振幅（MA）的变化趋势呈现高度相关，相关系数r在0.6以上；不同收缩形式、不同收缩速度下，均方根振幅（RMS）、积分肌电（iEMG）值会随着收缩速度的增加而减小；跳深动作下肢肌肉sEMG标准化后的值与跳深腾起速度之间均有一定的相关性，标准化后以最大随意等长收缩（MVIC）的标准化值与跳深腾起速度的相关性最高。  相似文献   

15.
BackgroundFemales are typically less fatigable than males during sustained isometric contractions at lower isometric contraction intensities. This sex difference in fatigability becomes more variable during higher intensity isometric and dynamic contractions. While less fatiguing than isometric or concentric contractions, eccentric contractions induce greater and longer lasting impairments in force production. However, it is not clear how muscle weakness influences fatigability in males and females during sustained isometric contractions.MethodsWe investigated the effects of eccentric exercise-induced muscle weakness on time to task failure (TTF) during a sustained submaximal isometric contraction in young (18–30 years) healthy males (n = 9) and females (n = 10). Participants performed a sustained isometric contraction of the dorsiflexors at 35° plantar flexion by matching a 30% maximal voluntary contraction (MVC) torque target until task failure (i.e., falling below 5% of their target torque for ≥2 s). The same sustained isometric contraction was repeated 30 min after 150 maximal eccentric contractions. Agonist and antagonist activation were assessed using surface electromyography over the tibialis anterior and soleus muscles, respectively.ResultsMales were ∼41% stronger than females. Following eccentric exercise both males and females experienced an ∼20% decline in maximal voluntary contraction torque. TTF was ∼34% longer in females than males prior to eccentric exercise-induced muscle weakness. However, following eccentric exercise-induced muscle weakness, this sex-related difference was abolished, with both groups having an ∼45% shorter TTF. Notably, there was ∼100% greater antagonist activation in the female group during the sustained isometric contraction following exercise-induced weakness as compared to the males.ConclusionThis increase in antagonist activation disadvantaged females by decreasing their TTF, resulting in a blunting of their typical fatigability advantage over males.  相似文献   

16.
Recently, addition of a gymnastics glide kip to a standard pull-up (SPU) has resulted in the kipping pull-up (KPU). Changes in muscle activation and kinematics were evaluated with eleven athletes performing sets of 5 SPU and 5 KPU. Surface electromyography of upper body and lower body muscles was recorded along with movement kinematics obtained via markers and motion tracking software. Most kinematic variables were significantly higher in the KPU including (KPU minus SPU deg): Max hip angle (48.8° ± 6.8°, p < 0.001) and max knee angle (56.5° ± 11.3°, p < 0.001). The recruitment of core and lower body muscles was significantly higher in the KPU (% MVIC increase): rectus abdominis (28.7 ± 4.7%, p < 0.001), external oblique (21.8 ± 4.1%, p < 0.001), iliopsoas (26.1 ± 5.5%, p = 0.001) and tensor fasciae latae (13.5 ± 2.3%, p < 0.001). Correspondingly, the biceps brachii had lower activation in the KPU (% MVIC decrease): (26.7 ± 0.6%, p = 0.006). Depending on the athlete’s goal, they may elect to perform an SPU for higher upper body muscle activation; or the KPU for more full-body activation with the potential to perform more repetitions through reduced upper body fatigue.  相似文献   

17.
The aim of the present study was to investigate the acute effect of the aerobic exercise volume on maximum strength and strength-endurance performance; and possible causes of strength decrements (i.e. central and peripheral fatigue). Twenty-one moderately trained men were submitted to a maximal incremental test to determine anaerobic threshold (AnT) and maximum dynamic strength (1RM) and strength-endurance (i.e. total volume load [TV]) tests to determine their baseline strength performance. Following, subjects performed six experimental sessions: aerobic exercise sessions (continuous running at 90% AnT) with different volumes (3?km, 5?km or 7?km) followed by 1RM or strength-endurance test in the 45° leg press exercise. Maximum voluntary isometric contraction (MVIC), voluntary activation (VA) level, contractile properties, and electromyographic activity (root mean square [RMS]) of the knee extensor muscles were assessed before and after aerobic exercises and after strength tests. TV was lower after 5?km and 7?km runs than in the control condition (12% and 22%, respectively). Additionally, TV was lower after 7?km than 3?km (14%) and 5?km (12%) runs. MVIC, VA, RMS, and contractile properties were reduced after all aerobic exercise volumes (～8%, ～5%, ～11% and ～6–14%, respectively). Additionally, MVIC, VA, and contractile properties were lower after strength tests (～15%, ～6%, ～9–26%, respectively). In conclusion, strength-endurance performance is impaired when performed after aerobic exercise and the magnitude of this interference is dependent on the aerobic exercise volume; and peripheral and central fatigue indices could not explain the different TV observed.  相似文献   

18.
This investigation examined the effects of three pre-match and half-time cooling manoeuvres on physical performance and associated physiological and perceptual responses in eight University soccer players during a non-motorised treadmill based individualised soccer-specific simulation [intermittent soccer performance test (iSPT)] at 30°C. Four randomised experimental trials were completed; following 30-min (pre-match) and 15-min (half-time) cooling manoeuvres via (1) ice slurry ingestion (SLURRY); (2) ice-packs placed on the quadriceps and hamstrings (PACKS); (3) mixed-methods (MM; PACKS and SLURRY concurrently); or no-cooling (CON). In iSPT first half, a moderate increase in total (Mean?±?Standard Deviation: 108?±?57 m, qualitative inference: most likely, Cohen’s d: 0.87, 90%CL: ±0.31), high-speed (56?±?46 m, very likely, 0.68?±?0.38) and variable run (15?±?5 m, very likely, 0.81?±?0.47) distance covered was reported in MM compared with CON. Additionally, pre-match reductions in thermal sensation (–1.0?±?0.5, most likely, –0.91?±?0.36), rectal (–0.6?±?0.1°C, very likely, –0.86?±?0.35) and skin temperature (–1.1?±?0.3°C, very likely, –0.88?±?0.42) continued throughout iSPT first half. Physical performance during iSPT first half was unaltered in SLURRY and PACKS compared to CON. Rectal temperature was moderately increased in SLURRY at 45-min (0.2?±?0.1°C, very likely, 0.67?±?0.36). Condition did not influence any measure in iSPT second half compared to CON. Only MM pre-match cooling augmented physical performance during iSPT first half, likely due to peripheral and central thermoregulatory factors favourably influencing first half iSPT performance. Further practical half-time cooling manoeuvres which enhance second half performance are still required.  相似文献   

19.
The aim of this study was to examine the occurrence of the sticking region by examining how three different grip widths affect the sticking region in powerlifters’ bench press performance. It was hypothesised that the sticking region would occur at the same joint angle of the elbow and shoulder independent of grip width, indicating a poor mechanical region for vertical force production at these joint angles. Twelve male experienced powerlifters (age 27.7 ± 8.8 years, mass 91.9 ± 15.4 kg) were tested in one repetition maximum (1-RM) bench press with a narrow, medium and wide grip. Joint kinematics, timing, bar position and velocity were measured with a 3D motion capture system. All participants showed a clear sticking region with all three grip widths, but this sticking region was not found to occur at the same joint angles in all three grip widths, thereby rejecting the hypothesis that the sticking region would occur at the same joint angle of the elbow and shoulder independent of grip width. It is suggested that, due to the differences in moment arm of the barbell about the elbow joint in the sticking region, there still might be a poor mechanical region for total force production that is joint angle-specific.  相似文献   

20.
The aims of this study were to investigate the differences in peak muscle activity and recruitment patterns during high- and low-velocity, concentric and eccentric, internal and external isokinetic shoulder rotations. Electromyographic activity of the rotator cuff and eight superficial muscles of the shoulder girdle was recorded on 25 healthy adults during isokinetic internal and external shoulder rotation at 60°/s and 240°/s. Peak muscle activity, electromyographic envelopes and peak isokinetic moments were analyzed using three-factor ANOVA and statistical parametric mapping. The subscapularis and serratus anterior showed moderate to high peak activity levels during each conditions, while the middle and posterior deltoids, upper, middle and lower trapezius, infraspinatus and supraspinatus showed higher peak activity levels during external rotations (+36.5% of maximum voluntary activation (MVA)). The pectoralis major and latissimus dorsi were more active during internal rotations (+40% of MVA). Only middle trapezius and pectoralis major electromyographic activity decreased with increasing velocity. Peak muscle activity was similar or lower during eccentric contractions, although the peak isokinetic moment increased by 35% on average. The subscapularis and serratus anterior appear to be important stabilizers of the glenohumeral joint and scapula. Isokinetic eccentric training at high velocities may allow for faster recruitment of the shoulder girdle muscles, which could improve joint stability during shoulder internal and external rotations.  相似文献   

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