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1.
This study investigated the autonomic and haemodynamic responses to different aerobic exercise loads, with and without blood flow restriction (BFR). In a crossover study, 21 older adults (8 males and 13 females) completed different aerobic exercise sessions: low load without BFR (LL) (40% VO2max), low load with BFR (LL-BFR) (40% VO2max + 50% BFR) and high load without BFR (HL) (70% VO2max). Heart rate variability and haemodynamic responses were recorded during rest and throughout 30 min of recovery. HL reduced R–R interval, the root mean square of successive difference of R–R intervals and high frequency during 30 min of recovery at a greater magnitude compared with LL and LL-BFR. Sympathetic–vagal balance increased the values for HL during 30 min of recovery at a greater magnitude when compared with LL and LL-BFR. Post-exercise haemodynamic showed reduced values of double product at 30 min of recovery compared to rest in LL-BFR, while HL showed higher values compared to rest, LL-BFR and LL. Reduced systolic blood pressure was observed for LL-BFR (30 min) compared to rest. Autonomic and haemodynamic responses indicate lower cardiovascular stress after LL-BFR compared to HL, being this method, besides the functional adaptations, a potential choice to attenuate the cardiovascular stress after exercise in older adults.  相似文献   

2.
ABSTRACT

Purpose: The purpose of this study was to identify whether post-resistance exercise (REx) blood flow restriction (BFR) can elicit a similar acute training stimulus to that offered by either heavy REx or traditional low-load BFR REx. Method: Ten men completed trials with 30% one-repetition maximum (1RM) for 5 sets of 15 repetitions without BFR (30%), with BFR during exercise (30% RD), and with postexercise BFR (30% RP) and at 75% 1RM for 3 sets of 10 repetitions. Lactate and cortisol were measured before and up to 60 min after exercise. Thigh circumference, ratings of perceived exertion (RPE), and pain were measured before and after exercise. Surface electromyography was measured during exercise. Results: All conditions had a large effect (effect size [ES] > 0.8) on lactate, with the largest effects observed with the 75% condition; no differences were observed between the 30% conditions. All conditions had a moderate effect (ES > 0.25 ≤ 0.4) on increasing thigh circumference. This effect was maintained (ES = 0.35) with the application of BFR after REx (30% RP). Change in RPE, from the first to last set, was significantly greater with 30% RD compared with other conditions (all p < .05). Electromyography amplitude was higher and percentage change was greater for the 75% condition compared with the other conditions (both p < .05). Conclusions: The application of BFR immediately post-REx altered several of the responses associated with REx that is aimed at inducing muscular hypertrophy. Additionally, these changes occurred with less pain and perceived exertion suggesting that this form of REx may offer an alternative, tolerable method of REx.  相似文献   

3.
This study investigated protein kinase activation and gene expression of angiogenic factors in response to low-load resistance exercise with or without blood flow restriction (BFR). In a repeated measures cross-over design, six males performed four sets of bilateral knee extension exercise at 20% 1RM (reps per set?=?30:15:15:continued to fatigue) with BFR (110?mmHg) and without (CON). Muscle biopsies were obtained from the vastus lateralis before, 2 and 4?h post-exercise. mRNA expression was determined using real-time RT–PCR. Protein phosphorylation/expression was determined using Western blot. p38MAPK phosphorylation was greater (p?=?0.05) at 2?h following BFR (1.3?±?0.8) compared to CON (0.4?±?0.3). AMPK phosphorylation remained unchanged. PGC-1α mRNA expression increased at 2?h (5.9?±?1.3 vs. 2.1?±?0.8; p?=?0.03) and 4?h (3.2?±?0.8 vs. 1.5?±?0.4; p?=?0.03) following BFR exercise with no change in CON. PGC-1α protein expression did not change following either exercise. BFR exercise enhanced mRNA expression of vascular endothelial growth factor (VEGF) at 2?h (5.2?±?2.8 vs 1.7?±?1.1; p?=?.02) and 4?h (6.8?±?4.9 vs. 2.5?±?2.7; p?=?.01) compared to CON. mRNA expression of VEGF-R2 and hypoxia-inducible factor 1α increased following BFR exercise but only eNOS were enhanced relative to CON. Matrix metalloproteinase-9 mRNA expression was not altered in response to either exercise. Acute low-load resistance exercise with BFR provides a targeted angiogenic response potentially mediated through enhanced ischaemic and shear stress stimuli.  相似文献   

4.
Physical inactivity is a major contributor to low-grade systemic inflammation. Most of the studies characterizing interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) release from exercising legs have been done in young, healthy men, but studies on inactivity in older people are lacking. The impact of 14 days of one-leg immobilization (IM) on IL-6 and TNF-α release during exercise in comparison to the contralateral control (CON) leg was investigated. Fifteen healthy men (age 68.1?±?1.1?year (mean?±?SEM); BMI 27.0?±?0.4 kg·m2; VO2max 33.3?±?1.6 ml·kg?1·min?1) performed 45?min of two-leg dynamic knee extensor exercise at 19.5?±?0.9 W. Arterial and femoral venous blood samples from the CON and the IM legs were collected every 15?min during exercise, and thigh blood flow was measured with ultrasound Doppler. Arterial plasma IL-6 concentration increased with exercise (rest vs. 45?min, main effect p?p?p?=?.085, effect size 0.28) higher in the IM leg compared to the CON leg (288 (95% CI: 213–373) vs. 220 (95% CI: 152–299) pg·min?1, respectively). There was no release of TNF-α in either leg and arterial concentrations remained unchanged during exercise (p?>?.05). In conclusion, exercise induces more pronounced IL-6 secretion in healthy older men. Two weeks of unilateral immobilization on the other hand had only a minor influence on IL-6 release. Neither immobilization nor exercise had an effect on TNF-α release across the working legs in older men.  相似文献   

5.
The purpose of the study was to investigate the current use of blood flow restriction (BFR) by practitioners during exercise/training. A questionnaire was developed and data were obtained from 250 participants, with 115 stating that they had prescribed BFR as an intervention. The most common exercise intervention used in combination with BFR was resistance exercise (99/115), followed by during passive (30/115) conditions, and during aerobic exercise (22/115). The main outcome measure for using the technique was to increase muscle mass (32.6%) followed by rehabilitation from injury (24.2%). Over half of respondents (57.4%) reported that they did not use the same cuff widths for the lower body and upper body, with varying final restriction pressures also being utilised during each different exercise modality. Most practitioners performed the technique for ~10 min each training session, 1–4 times per week. Eighty percent of practitioners rated the use of BFR as very good-excellent. The incidence rate of side effects was largest for delayed onset muscle soreness (39.2%), numbness (18.5%), fainting/dizziness (14.6%) and bruising (13.1%). These results indicate that the use of BFR training is widespread amongst practitioners; however, care should be taken to ensure that practice matches current research to ensure the safety of this technique.  相似文献   

6.
目的:探究冷水浴对延迟性肌肉酸痛(DOMS)患者膝关节本体感觉的干预效果及作用机制。方法:采用随机对照试验,24名男性二级短跑运动员随机分为冷水浴干预组(n=12)和静坐对照组(n=12)。经离心运动诱发下肢肌群出现DOMS,静坐休息5min后进行冷水干预或静坐。分别在运动前、运动后24h、48h、72h、96h测量受试者的左大腿围度、自觉疼痛程度、左腿股四头肌最大等长肌力以及左腿膝关节本体感觉(位置觉+肌肉力觉)。在运动前、运动后即刻(0min)、5min、10min、15min分别测量血乳酸值。结果:(1)离心运动后即刻,两组大腿围度均显著性增加(P<0.05),运动后24h、48h、72h,CWI组的左大腿围度显著低于CON组(P<0.01);(2)离心运动后即刻,两组自觉疼痛程度均显著性增加,运动后24h、72h,CWI组的疼痛程度显著性低于CON组(P<0.01);(3)离心运动后即刻,两组血乳酸值均出现显著性上升(P<0.05),运动后0min~15min,两组间无显著性差异(P>0.05);(4)离心运动后即刻,两组的左腿MVIC均出现显著性下降(P<0.05),运动后24h~96h,CWI组MVIC显著高于CON组(P<0.01),(5)离心运动后即刻,两组左腿的本体感觉(主、被动位置觉、肌肉力觉)均出现显著性下降(P<0.05);运动后24h~96h,CWI组的主动位置觉显著高于CON组(P<0.01),运动后72h,CWI组的被动位置觉显著低于CON组(P<0.01),其他时间点(24h、48h、96h)无显著性差异(P>0.05),运动后24h~96h,CWI组的肌肉力觉显著高于CON组(P<0.01)。结论:冷水浴是运动训练或比赛后快速减轻DOMS症状的有效手段,有利于肌肉肿胀的恢复、减轻疼痛感、促进工作肌肉最大等长肌力及该肌肉所附着关节的本体感觉的恢复,总体有利于减轻DOMS症状。  相似文献   

7.
目的:探讨急性离心运动伴4种不同程度的血流限制对年轻女性外周疲劳及心脏自主神经功能的影响,综合评价各方案的安全性,为长期血流限制运动干预提供参考。方法:将40名女大学生随机分为4组,分别进行小强度抗阻(30%1RM)伴0%(CON组)、40%(BFR40组)、60%(BFR60组)和80%(BFR80组)动脉闭塞压(AOP)的血流限制运动。各小组进行4组伸膝离心运动,第1组重复30次,后3组重复15次,组间休息30 s。检测运动前、运动后即刻、15 min、30 min、1 h以及24 h的骨骼肌收缩性能(最大径向位移、收缩速度)、最大等长力量和心脏自主神经功能。结果:1)与CON组相比,BFR40组的副交感神经活性受到轻微抑制(P<0.05),可在运动后30 min内恢复(P>0.05);2)BFR60组的最大等长力量在运动后显著下降(P<0.01),副交感神经活性进一步抑制(P<0.01),交感神经支配增强(P<0.05),运动后30 min内恢复交感—副交感神经的平衡性(P>0.05);3)BFR80组运动后诱发显著的外周疲劳(P<0.01),使副交感恢复显著延迟,交感活性大幅增强(P<0.05),需更长时间恢复交感—副交感神经的平衡性(24 h内);4)相关性分析显示,副交感神经活性分别与最大径向位移(r=0.65)、收缩速度(r=0.62)和最大等长力量(r=0.55)呈正相关(P<0.05),交感神经活性与上述3个指标呈负相关(P<0.05)。结论:血流限制运动中,40%AOP会抑制迷走神经活性;60%AOP可明显影响交感神经活性和交感—副交感调控的平衡性;80%AOP可诱发显著的外周疲劳,且与心脏自主神经调控密切相关。综上所述,不建议心血管风险高的患者使用80%AOP训练。  相似文献   

8.
目的:探讨正弦波振动(HFV)对制动大鼠肌肉萎缩的对抗作用。方法:以大鼠后肢制动为废用模型,对振动组大鼠施以不同频率的HFV,观察大鼠比目鱼肌(SOL)湿重体重比、肌纤维横截面积、梭外肌纤维构成比以及梭内肌纤维肌球蛋白重链(MHC)的表达的变化。结果:(1)制动14 d后,SOL湿重体重比、肌纤维横截面积以及梭外肌Ⅰ型肌纤维的构成比明显下降,Ⅱ型肌纤维的构成比明显增加,梭内肌纤维MHC的表达有所增强;(2)施加HFV后,SOL湿重体重比、肌纤维横截面积和Ⅰ型肌纤维的构成比明显上升,Ⅱ型肌纤维的构成比明显下降,梭内肌纤维MHC的表达正常。结论:HFV可对抗废用后SOLⅠ型肌纤维向Ⅱ型肌纤维的转化和梭内肌MHC表达有增强的趋势,且以200 Hz HFV组最为显著。  相似文献   

9.
就少年短跑运动员大腿后侧肌群力量训练比重失调 ,而引起大腿力量发展不均衡 ,使运动员在比赛中肌肉易受损伤并影响运动成绩 ,进行深入的分析。指出在少年短跑训练中应高度重视对大腿后侧肌群的力量训练 ,要根据少年选手的具体情况 ,采用相应的力量训练方法与手段进行针对性训练 ,以尽快缩小大腿前后侧肌群力量的差异 ,提高肌肉力量训练的整体水平 ,为提高短跑运动成绩预防肌肉拉伤打下良好基础。  相似文献   

10.
ABSTRACT

The systematic review and meta-analysis evaluated the effect of aerobic, resistance and combined exercise on RMR (kCal·day-1) and performed a methodological assessment of indirect calorimetry protocols within the included studies. Subgroup analyses included energy/diet restriction and body composition changes. Randomized control trials (RCTs), quasi – RCTs and cohort trials featuring a physical activity intervention of any form and duration excluding single exercise bouts were included. Participant exclusions included medical conditions impacting upon RMR, the elderly (≥65 years of age) or pregnant, lactating or post-menopausal women. The review was registered in the International Prospective Register of Systematic Reviews (CRD 42,017,058,503). 1669 articles were identified; 22 were included in the qualitative analysis and 18 were meta-analysed. Exercise interventions (aerobic and resistance exercise combined) did not increase resting metabolic rate (mean difference (MD): 74.6 kCal·day-1[95% CI: ?13.01, 161.33], P = 0.10). While there was no effect of aerobic exercise on RMR (MD: 81.65 kCal·day-1[95% CI: ?57.81, 221.10], P = 0.25), resistance exercise increased RMR compared to controls (MD: 96.17 kCal·day-1[95% CI: 45.17, 147.16], P = 0.0002). This systematic review effectively synthesises the effect of exercise interventions on RMR in comparison to controls; despite heterogenous methodologies and high risk of bias within included studies.  相似文献   

11.
BackgroundIt remains unclear whether studies comparing maximal oxygen uptake (VO2max) response to sprint interval training (SIT) vs. moderate-intensity continuous training (MICT) are associated with a high risk of bias and poor reporting quality. The purpose of this study was to evaluate the risk of bias and quality of reporting in studies comparing changes in VO2max between SIT and MICT.MethodsWe conducted a comprehensive literature search of 4 major databases: AMED, CINAHL, EMBASE, and MEDLINE. Studies were excluded if participants were not healthy adult humans or if training protocols were unsupervised, lasted less than 2 weeks, or utilized mixed exercise modalities. We used the Cochrane Collaboration tool and the CONSORT checklist for non-pharmacological trials to evaluate the risk of bias and reporting quality, respectively.ResultsTwenty-eight studies with 30 comparisons (3 studies included 2 SIT groups) were included in our meta-analysis (n = 360 SIT participants: body mass index (BMI) = 25.9 ± 3.7 kg/m2, baseline VO2max = 37.9 ± 8.0 mL/kg/min; n = 359 MICT participants: BMI = 25.5 ± 3.8 kg/m2, baseline VO2max = 38.3 ± 8.0 mL/kg/min; all mean ± SD). All studies had an unclear risk of bias and poor reporting quality.ConclusionAlthough we observed a lack of superiority between SIT and MICT for improving VO2max (weighted Hedge's g = ?0.004, 95% confidence interval (95%CI): ?0.08 to 0.07), the overall unclear risk of bias calls the validity of this conclusion into question. Future studies using robust study designs are needed to interrogate the possibility that SIT and MICT result in similar changes in VO2max.  相似文献   

12.
The aim of this study was to compare the effect of low-load resistance exercise (LLRE) with continuous and intermittent blood flow restriction (BFR) on the creatine kinase (CK), lactate dehydrogenase (LDH), protein carbonyl (PC), thiobarbituric acid-reactive substance (TBARS) and uric acid (UA) levels in military men. The study included 10 recreationally trained men aged 19 ± 0.82 years who underwent the following experimental protocols in random order on separate days (72–96 h): 4 LLRE sessions at a 20% 1RM (one-repetition maximum [1RM]) with continuous BFR (LLRE + CBFR); 4 LLRE sessions at 20% 1RM with intermittent BFR (LLRE + IBFR) and 4 high-intensity resistance exercise (HIRE) sessions at 80% 1RM. The CK and LDH (markers of muscle damage) levels were measured before exercise (BE), 24 h post-exercise and 48 h post-exercise, and the PC, TBARS and UA (markers of oxidative stress) levels were measured BE and immediately after each exercise session. There was a significant increase in CK in the HIRE 24 post-exercise samples compared with the LLRE + CBFR and LLRE + IBFR (P = 0.035, P = 0.036, respectively), as well as between HIRE 48 post-exercise and LLRE + CBFR (P = 0.049). Additionally, there was a significant increase in CK in the LLRE + CBFR samples BE and immediately after each exercise (Δ = 21.9%) and in the HIRE samples BE and immediately after each exercise, BE and 24 post-exercise, and BE and 48 post-exercise (Δ values of 35%, 177.6%, and 177.6%, respectively). However, there were no significant changes in LDH, PC, TBARS, and UA between the protocols (P > 0.05). Therefore, a physical exercise session with continuous or intermittent BFR did not promote muscle damage; moreover, neither protocol seemed to affect the oxidative stress markers.  相似文献   

13.
Previous studies have shown that cycling can directly influence neuromuscular control during subsequent running in some highly trained triathletes, despite these triathletes' years of practice of the cycle-run transition. The aim of this study was to determine whether cycling has the same direct influence on neuromuscular control during running in moderately trained triathletes. Fifteen moderately trained triathletes participated. Kinematics of the pelvis and lower limbs and recruitment of 11 leg and thigh muscles were compared between a control run (no prior exercise) and a 30 min run that was preceded by a 15 min cycle (transition run). Muscle recruitment was different between control and transition runs in only one of 15 triathletes (<7%). Changes in joint position (mean difference of 3°) were evident in five triathletes, which persisted beyond 5 min of running in one triathlete. Our findings suggest that some moderately trained triathletes have difficulty reproducing their pre-cycling movement patterns for running initially after cycling, but cycling appears to have little influence on running muscle recruitment in moderately trained triathletes.  相似文献   

14.
通过对运动员股四头肌、股后肌群不同断面面积及髋关节屈伸力矩的测量,探索不同项目运动员大腿肌肉不同断面的面积大小与髋关节屈伸力量相关的内在规律。肌肉横断面积采用螺旋CT进行断层扫描,影像分析采用MoticImagesAdvanced3.0测试系统软件,力量测试采用美国Cybex-Norm等速测力系统,数据处理采用SPSS8.0软件。结果表明:1)运动员股四头肌、股后肌群不同断面面积与髋关节屈伸力矩的相关性主要体现在大腿的中、上段,髋关节屈时的相关以上段为主,伸时的相关以上、中段为主。2)足球运动员在中、高速运动左髋屈时,其屈肌的力量与大腿上段肌肉的横断面积密切相关,而右侧在低、高速也具有同样的相关;而足球运动员在中、高速运动左髋伸时,其伸肌的力量与大腿中段肌肉的横断面积密切相关。速滑运动员的相关性以右侧伸肌相关最明显。  相似文献   

15.
目的了解七叶皂甙钠对肢体制动大鼠骨骼肌萎缩的作用。方法将60只健康、体重150-200 g的雌性SD大鼠按体重配对原则随机分为对照组(CON)、大鼠右后肢石膏固定组(IB)、七叶皂甙钠 大鼠右后肢石膏固定(SA)三组,每组20只。将IB及SA组大鼠右后肢石膏固定,SA组每日腹腔注射β-七叶皂甙钠10 mg/kg,CON及IB腹腔注射等体积生理盐水,共治疗3 w。试验结束处死三组大鼠,取双后肢比目鱼肌,分别称重。于比目鱼肌中段切取部分肌肉组织,HE染色后用自动图像分析仪测定肌细胞直径及截面积。将部分比目鱼肌制成匀浆,取匀浆液上清液用于超氧化物歧化酶(SOD)、丙二醛(MDA)的检测。结果大鼠右后肢石膏固定3 w后,IB组大鼠右后肢比目鱼肌湿重、肌细胞直径及肌纤维截面积明显低于CON及SA组。与IB组相比,SA组比目鱼肌SOD活性明显升高,MDA水平明显降低。结论七叶皂甙钠可提高大鼠骨骼肌的抗氧化能力,对肢体制动大鼠骨骼肌萎缩有预防作用。  相似文献   

16.
BackgroudBlood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training.MethodsA total of 7 healthy young men performed squats, and between sets BFR was carried out on one leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mmHg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training.ResultsDoppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. microRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-β serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg.ConclusionBFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.  相似文献   

17.
Abstract

In this study, we examined the time course of changes in the blood volume and oxygenation of accessory respiratory (RM) and locomotor (LM) muscles, and the interrelationships of changes in these parameters during maximal incremental intermittent exercise in 15 non-endurance-trained active men. Blood volume and oxygenation of the serratus anterior and of vastus lateralis were measured simultaneously by near-infrared spectroscopy. The respiratory compensation point, and the breakpoints where abrupt changes were apparent in RM and LM blood volume and oxygenation versus time were identified. During exercise, the decreases in RM and LM oxygenation were accentuated in the vicinity of the respiratory compensation point. This was concomitant with a reduction in LM, but not RM, blood volume. The time at which the respiratory compensation point and the breakpoints in RM and LM blood volume and oxygenation were detected (70.2–75.0% exercise time) did not differ, and were inter-correlated (r=0.56 to 0.95). Moreover, the rate of the accelerated fall of oxygenation in the locomotor muscles was correlated with that of the decline in blood volume in that area (r=0.73), and with that of the accelerated fall of oxygenation in the respiratory muscles (r=0.71). The results suggest that the high ventilatory demand, which occurs naturally during intense intermittent exercise in non-endurance-trained individuals, may precipitate an accelerated fall in RM oxygenation, concomitant with a reduction in LM blood volume and an accentuated decline in LM oxygenation. Such responses are likely to occur above the respiratory compensation point during intermittent exercise.  相似文献   

18.
Abstract

The purpose of this study was to examine the changes in the metabolic state of quadriceps femoris muscles using transverse relaxation time (T2), measured by muscle functional magnetic resonance (MR) imaging, after inactive or active recovery exercises with different intensities following high-intensity knee-extension exercise. Eight healthy men performed recovery sessions with four different conditions for 20 min after high-intensity knee-extension exercise on separate days. During the recovery session, the participants conducted a light cycle exercise for 20 min using a cycle (50%, 70% and 100% of the lactate threshold (LT), respectively: active recovery), and inactive recovery. The MR images of quadriceps femoris muscles were taken before the trial and after the recovery session every 30 min for 120 min. The percentage changes in T2 for the rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT were significantly lower than those in either inactive recovery or 100%LT. There were no significant differences in those for vastus lateralis and vastus intermedius muscles among the four trials. The percentage changes in T2 of rectus femoris and vastus medialis muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in either inactive recovery or 100%LT. Those of vastus lateralis and vastus intermedius muscles after the recovery session in 50%LT and 70%LT decreased to the values before the trial faster than those in 100%LT. Although the changes in T2 after active recovery exercises were not uniform in exercised muscles, the results of this study suggest that active recovery exercise with the intensities below LT are more effective to recover the metabolic state of quadriceps femoris muscles after intense exercise than with either intensity at LT or inactive recovery.  相似文献   

19.
Abstract

Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low-intensity exercise likely requires more repetitions and individuals with injuries may be incapable of sustaining the mechanical stress to reach failure. The aim of this study was to determine if knee wraps provide a stimulus to decrease time to failure. Twenty healthy individuals participated in a randomized crossover study consisting of three trials. The first trial was used to determine one-repetition maximum (1-RM) on leg extension. Participants were then assigned to a blood flow restriction or control group. After trial 2, participants crossed over to the opposite trial. Knee wraps were placed around the upper thigh of each leg during blood flow restriction. Leg extensions were completed at 30% 1-RM until failure. A rating of perceived exertion was taken after exercise and whole blood samples were taken before, after, and 3 min after exercise for the determination of lactate. Repetitions until failure and total work were significantly lower with practical blood flow restriction compared with the control trial. Metabolic stress as measured by whole blood lactate was higher immediately after muscular failure in the control compared with the blood flow restriction trial, but not so 3 min after exercise. There were no differences in ratings of perceived exertion. In conclusion, knee wraps provide a stimulus for blood flow restriction allowing failure to occur sooner with similar metabolic stress after reperfusion. However, similar perceptual responses despite the lower workload with blood flow restriction may limit its application to the highly motivated.  相似文献   

20.
During the earliest stages of resistance exercise training, initial muscular strength gains occur too rapidly to be explained solely by muscle-based mechanisms. However; increases in surface-based EMG amplitude as well as motor unit discharge rate provide some insight to the existence of neural mechanisms in the earliest phases of resistance exercise training. Moreover, other phenomena such as the cross transfer of strength following unilateral exercise and neural changes following limb immobilization also support a role for neural control in muscular strength. While studies to date have focused on the phenomenon of neural change, future studies will need to focus on the many motoneuron influences as well as intrinsic motoneuronal properties that may be responsible for these neural adaptations.  相似文献   

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