The effects of a high-intensity free-weight back-squat exercise protocol on postural stability in resistance-trained males

The purpose of this study was to investigate the effects of a high-intensity free-weight back-squat exercise on postural stability characteristics in resistance-trained males. Eighteen college-aged (mean ± SD: age = 22.9 ± 2.9 years; height = 175.8 ± 6.4 cm; mass = 86.3 ± 9.3 kg), resistance-trained males performed postural stability testing before and after completing five sets of eight repetitions of back-squat exercises at 80% of one-repetition maximum. A commercial balance testing device was used to assess sway index at pre- and at 0, 5, 10, 15 and 20 min post-exercise. Each balance assessment consisted of four, 20-s static stance conditions: eyes-open firm surface, eyes-closed firm surface, eyes-open soft surface and eyes-closed soft surface. Sway index was greater (P = 0.001–0.020) at Post 0 than at all other time points. No differences (P > 0.05) were observed between any other time phases. Sway index was greater (P < 0.001) for eyes-closed soft surface than all other conditions. These findings revealed sway index for all conditions significantly increased following completion of the back-squat; however, sway index recovered within 5 min of exercise. Higher sway index values as a result of neuromuscular fatigue induced by a back-squat exercise may have performance and injury risk consequences to subsequent activities that rely on postural stability. However, these findings suggest balance impairments may recover in ~5 min following high-intensity lower body resistance exercise.     

The acute angiogenic signalling response to low-load resistance exercise with blood flow restriction

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.     

耐力训练与中枢神经系统细胞凋亡的实验研究

采用实验法，对耐力训练后中枢神经系统细胞凋亡特征进行了研究。结果表明，中等强度耐力训练对CNS细胞凋亡的影响不大，而大强度耐力训练后CNS细胞凋亡明显增加，对其与CNS功能变化的分析能为体育运动实践提供指导。     

The metabolic and temporal basis of muscle hypertrophy in response to resistance exercise

Constituting ～40% of body mass, skeletal muscle has essential locomotory and metabolic functions. As such, an insight into the control of muscle mass is of great importance for maintaining health and quality-of-life into older age, under conditions of cachectic disease and with rehabilitation. In healthy weight-bearing individuals, muscle mass is maintained by the equilibrium between muscle protein synthesis (MPS) and muscle protein breakdown; when this balance tips in favour of MPS hypertrophy occurs. Despite considerable research into pharmacological/nutraceutical interventions, resistance exercise training (RE-T) remains the most potent stimulator of MPS and hypertrophy (in the majority of individuals). However, the mechanism(s) and time course of hypertrophic responses to RE-T remain poorly understood. We would suggest that available data are very much in favour of the notion that the majority of hypertrophy occurs in the early phases of RE-T (though still controversial to some) and that, for the most part, continued gains are hard to come by. Whilst the mechanisms of muscle hypertrophy represent the culmination of mechanical, auto/paracrine and endocrine events, the measurement of MPS remains a cornerstone for understanding the control of hypertrophy – mainly because it is the underlying driving force behind skeletal muscle hypertrophy. Development of sophisticated isotopic techniques (i.e. deuterium oxide) that lend to longer term insight into the control of hypertrophy by sustained RE-T will be paramount in providing insights into the metabolic and temporal regulation of hypertrophy. Such technologies will have broad application in muscle mass intervention for both athletes and for mitigating disease/age-related cachexia and sarcopenia, alike.     

The time-frame of acute resistance exercise effects on football skill performance: The impact of exercise intensity

Abstract

The purpose of this study was to determine the recovery rate of football skill performance following resistance exercise of moderate or high intensity. Ten elite football players participated in three different trials: control, low-intensity resistance exercise (4 sets, 8–10 repetitions/set, 65–70% 1 repetition maximum [1RM]) and high-intensity resistance exercise (4 sets, 4–6 repetitions/set, 85–90% 1RM) in a counterbalanced manner. In each experimental condition, participants were evaluated pre, post, and at 24, 48, 72 h post exercise time points. Football skill performance was assessed through the Loughborough Soccer Passing Test, long passing, dribbling, shooting and heading. Delayed onset muscle soreness, knee joint range of motion, and muscle strength (1RM) in squat were considered as muscle damage markers. Blood samples analysed for creatine kinase activity, C-reactive protein, and leukocyte count. Passing and shooting performance declined (P < 0.05) post-exercise following resistance exercise. Strength declined post-exercise following high-intensity resistance exercise. Both trials induced only a mild muscle damage and inflammatory response in an intensity-dependent manner. These results indicate that football skill performance is minimally affected by acute resistance exercise independent of intensity suggesting that elite players may be able to participate in a football practice or match after only 24 h following a strength training session.     

Age-specific response of skeletal muscle extracellular matrix to acute resistance exercise: A pilot study

The extracellular matrix (ECM) plays an essential role in the development, growth and repair of skeletal muscles and serves to transmit contractile force. However, its regulation is poorly understood. This study investigates the age-specificity of the effects of acute resistance exercise on ECM gene expression. To this purpose, five young (YM, 23.8?±?2.2 yrs.) and 5 elderly (EM, 66.8?±?4.1 yrs.) men performed one session of unilateral leg press and leg extension exercises. Six hours post-exercise, biopsies were taken from the vastus lateralis muscles of both legs. A PCR array was used to profile the expression of 84 ECM-related genes, of which 6 were validated by qPCR. The PCR array found 9 and 4 ECM-associated genes to be selectively altered (>1.5-fold change) in YM or EM only. Four further genes were upregulated in YM but downregulated in EM. Of the 6 genes validated on individual samples MMP9 expression increased in YM (9.7-fold) and decreased (0.2-fold) in EM. MMP15 was downregulated in EM only (0.6-fold). A significant correlation between leg extension 1 RM and changes in COL7A1 expression (ρ?=?0.71) suggests a potential influence of fitness levels. In conclusion, acute resistance exercise affects ECM gene expression at least partly in an age-specific manner. The altered expression of genes encoding matrix metalloproteinases (MMP3, MMP9, MMP15) highlights the role of remodelling processes in the response to an acute bout of resistance exercise. Larger studies are required to verify the age-associated differences in gene expression profiles and establish their functional implications.     

运动训练中疲劳与恢复的研究

结合竞技体育训练方面的实践，阐述了疲劳与恢复之间的关禾及其对提高训练成绩的影响，以便广大教练员、运动员、体育管理人员对疲劳与恢复方面的问题有一个进一步的认识和了解，从而更好地指导运动训练与竞赛。     

The acute effects of resistance exercise on the main determinants of blood rheology

The aim of this study was to examine short-term changes in blood rheological variables after a single bout of resistance exercise. Twenty-one healthy males completed three sets of 5?–?7 repetitions of six exercises at an intensity corresponding to 80% of one-repetition maximum (1-RM). The average duration of the exercise bout was 35?min. Venous blood samples were obtained before exercise, immediately after exercise and after 30?min of recovery and analysed for lactate, red blood cell count, haematocrit, haemoglobin, plasma viscosity, fibrinogen, total protein and albumin concentration. Plasma volume decreased 10.1% following resistance exercise. This occurred in parallel with an increase of 5.6%, 5.4% and 6.2% in red blood cell count, haemoglobin and haematocrit; respectively. Plasma viscosity increased from 1.55?±?0.01 to 1.64?±?0.01 mPa?·?s immediately after resistance exercise before decreasing to 1.57?±?0.01 mPa?·?s at the end of the recovery period. Similarly, fibrinogen, albumin and total protein increased significantly following resistance exercise. However, the rises in all these rheological parameters were transient and returned to pre-exercise values by the end of recovery. We conclude that a single session of heavy resistance exercise performed by normal healthy individuals alters blood rheological variables and that these changes are transient and could be attributed to exercise-induced haemoconcentration.     

Caffeine and resistance exercise: the effects of two caffeine doses and the influence of individual perception of caffeine

Abstract

Although caffeine is a widely used ergogenic resource, some information regarding its effects on resistance exercises is still lacking. The objective of the present study was to verify the acute effect of the ingestion of two different doses of caffeine on performance during a session of resistance exercises and to analyze the perception of the subjects in relation to the intake of caffeine. Following a double-blind, randomised, cross-over, controlled, and non-placebo design, 14 trained and healthy men (24.7?±?6.8 years; 79.8?±?9.8?kg; 177.3?±?8.5?cm) performed a training session in chest-press, shoulder-press, and biceps curl exercises (3 sets until exhaustion; 70% 1RM; 3 min rest interval; 2?s for each concentric and eccentric phase) on three non-consecutive days after ingestion of 3?mg.kg^?1 caffeine (CAF3), 6?mg.kg^?1 caffeine (CAF6), or no substance (CON). Subjects were informed that one of the caffeine doses would be placebo. The total number of repetitions performed in CON (93.6?±?22.4) was significantly lower than in CAF3 (108.0?±?19.9, P?=?0.02) and in CAF6 (109.3?±?19.8, P?=?0.03) and there were no differences between caffeine doses. Eight subjects noticed that caffeine was in CAF3 and six in CAF6 and there were no differences in the number of repetitions between sessions in which the subjects perceived and did not perceive caffeine. In conclusion, caffeine doses of 3 or 6?mg.kg^?1 similarly increased performance in resistance upper limb exercises, independent of the subject's perception of substance ingestion.     

青少年中长跑训练后疲劳消除的方法与措施

青少年运动员中长跑大运动量训练后,增加了负荷,并加深加重了机体的疲劳.本文是以文献资料为基础,结合教学训练中的实际情况,分析了中长跑训练后肌肉疲劳和神经系统疲劳两大主要因素并对其恢复的手段及措施进行了探讨.     

浅谈运动训练中疲劳与恢复的运动生理过程

采用文献资料法,分析了人体疲劳产生的生理过程,提出了相应的恢复人体疲劳过程的方法与手段。研究表明,消除与恢复疲劳,对于提高运动成绩,增进健康有着十分重要的意义。     

一次性耐力运动对大鼠间脑单胺类神经递质变化及代谢能力的影响

为运动性中枢疲劳的研究提供理论依据,建立持续游泳的动物模型,探讨一次性耐力运动对大鼠间脑单胺类神经递质变化及代谢能力的影响。结果为①3h游泳后即刻,间脑5-HT增加23.15%,至少可通过神经-内分泌调节、体温调节、情绪变化等因素影响机体的运动能力;②一次性耐力运动期间,间脑5-HT合成过程占优势,分解过程变化不明显,而恢复期分解代谢过程占优势;③一次性耐力运动可显著降低间脑DA水平,5-HT与DA比率亦显著性升高(P<0.05),20h恢复期间脑DA浓度增高,5-HT与DA比值降低(-27.51%)。     

再竭运动恢复期大鼠纹状体微透析液中Glu和GABA含量的变化

目的：观察大鼠力竭运动恢复期纹状体细胞外液谷氨酸（Glu）、γ-氨基丁酸（GABA）含量的动态变化,分析它们的变化特点与相互关系,为探索运动性中枢疲劳产生和恢复机制提供实验依据。方法：将12只SD雄性大鼠随机分为安静对照组（6只）和力竭运动组（6只）,于运动后4h、5h、6h、8h、24h收集微透析样品并采用毛细管电泳一激光诱导荧光法直接进样检测。结果：力竭运动恢复期大鼠纹状体细胞外液中Glu含量高于安静水平,其恢复期变化呈先上升后下降的趋势,运动后8h达峰值,运动后24h仍显著高于安静水平（P〈0．05）;GABA含量高于安静水平,其恢复期变化呈先上升后下降的趋势,运动后6h达峰值,运动后24h仍显著高于安静水平（P〈0．05）;Glu／GABA比值显著低于安静水平（P〈0．05）,运动后24h仍显著低于安静水平（P〈0.05）。结论：运动性中枢疲劳产生时,机体同时促进Glu、GABA的释放,但是GABA释放量更高,抑制性神经递质释放占优势,通过直接通路和间接通路抑制运动。恢复期后期两者均逐渐下降,纹状体兴奋性逐渐升高,疲劳得以逐渐恢复。力竭运动恢复期大鼠纹状体细胞外液Glu、GABA含量升高及恢复均有延迟性,力竭运动后24h恢复仍未完成;大鼠纹状体细胞外Glu／GABA显著低于安静水平,24h恢复期抑制性神经递质仍起主导作用。     

The compatibility of concurrent high intensity interval training and resistance training for muscular strength and hypertrophy: a systematic review and meta-analysis

The purpose of this systematic review and meta-analysis is to assess the effect of concurrent high intensity interval training (HIIT) and resistance training (RT) on strength and hypertrophy. Five electronic databases were searched using terms related to HIIT, RT, and concurrent training. Effect size (ES), calculated as standardised differences in the means, were used to examine the effect of concurrent HIIT and RT compared to RT alone on muscle strength and hypertrophy. Sub-analyses were performed to assess region-specific strength and hypertrophy, HIIT modality (cycling versus running), and inter-modal rest responses. Compared to RT alone, concurrent HIIT and RT led to similar changes in muscle hypertrophy and upper body strength. Concurrent HIIT and RT resulted in a lower increase in lower body strength compared to RT alone (ES = ?0.248, p = 0.049). Sub analyses showed a trend for lower body strength to be negatively affected by cycling HIIT (ES = ?0.377, p = 0.074) and not running (ES = ?0.176, p = 0.261). Data suggests concurrent HIIT and RT does not negatively impact hypertrophy or upper body strength, and that any possible negative effect on lower body strength may be ameliorated by incorporating running based HIIT and longer inter-modal rest periods.     

The effects of resistance exercise with and without different degrees of blood-flow restriction on perceptual responses

The aim was to compare exercise with and without different degrees of blood-flow restriction on perceived exertion (RPE) and discomfort. Participants were assigned to Experiment 1, 2, or 3. Each completed protocols differing by pressure, load, and/or volume. RPE and discomfort were taken before and after each set. For pressure and RPE, the 20% one repetition maximum (1RM) blood-flow restriction conditions were affected by increasing the pressure from 40% to 50% blood-flow restriction (~12 vs. ~14). This did not appear to happen within the 30% 1RM blood-flow restriction conditions or the higher pressures in the 20% 1RM conditions. The similar RPE between 20% and 30% 1RM to failure was expected given both were to failure. For discomfort, ratings were primarily affected by load at the lowest pressure. Increasing pressure to 50% blood-flow restriction increased discomfort at 20% 1RM (~2.6 vs. ~4). There was a further increase when increasing to 60% blood-flow restriction (~4 vs. ~4.8). The high-load condition had the lowest discomfort, while ratings were highest with 20% 1RM to failure. In conclusion, exercise with blood-flow restriction does not appear to augment the perceptual response observed with low-load exercise to failure.     

力竭运动恢复期大鼠纹状体微透析液中DA、5-HT及其代谢物的动态变化

通过微透析采样技术,观察大鼠力竭运动后恢复期不同时段纹状体细胞外液多巴胺(DA)、5-羟色胺(5-HT)含量及其代谢的动态变化,分析运动恢复期DA和5-HT的变化特点与相互关系,为探索运动性中枢疲劳和恢复机制提供实验依据。研究发现:力竭运动恢复期不仅大鼠纹状体DA、5-HT和5-HIAA的代谢恢复具有延迟性,其释放恢复也都具有延迟性,力竭运动后24h恢复仍未完成;力竭运动恢复期中大鼠纹状体细胞外5-HIAA含量变化与细胞外5-HT含量变化具有同步性,但变化没有5-HT显著;大鼠纹状体细胞外DA/5-HT显著低于安静水平,24h恢复期抑制性神经递质仍起主导作用;运动疲劳产生时纹状体细胞外DA和5-HT含量的变化较其总量变化更加敏感,提示使用微透析监控中枢细胞外液中DA和5-HT含量的变化可以更加敏感、可靠地评价运动性中枢疲劳。     

The acute effects of bodyweight suspension exercise on muscle activation and muscular fatigue

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.     

A pilot study on quantification of training load: The use of HRV in training practice

Recent laboratory studies have suggested that heart rate variability (HRV) may be an appropriate criterion for training load (TL) quantification. The aim of this study was to validate a novel HRV index that may be used to assess TL in field conditions. Eleven well-trained long-distance male runners performed four exercises of different duration and intensity. TL was evaluated using Foster and Banister methods. In addition, HRV measurements were performed 5 minutes before exercise and 5 and 30 minutes after exercise. We calculated HRV index (TL_HRV) based on the ratio between HRV decrease during exercise and HRV increase during recovery. HRV decrease during exercise was strongly correlated with exercise intensity (R = ?0.70; p < 0.01) but not with exercise duration or training volume. TL_HRV index was correlated with Foster (R = 0.61; p = 0.01) and Banister (R = 0.57; p = 0.01) methods. This study confirms that HRV changes during exercise and recovery phase are affected by both intensity and physiological impact of the exercise. Since the TL_HRV formula takes into account the disturbance and the return to homeostatic balance induced by exercise, this new method provides an objective and rational TL index. However, some simplification of the protocol measurement could be envisaged for field use.     

力竭运动后大鼠外周血mir-24与大脑皮质Bax表达运动性中枢疲劳

目的:探讨一次性力竭游泳运动后大鼠外周血mir-24和大脑皮质bax基因表达变化与运动性中枢疲劳的关系。方法:健康雄性Wista大鼠48只,随机分为对照组(C组)、一次性力竭运动组(E组)。力竭运动后即刻和24h取各组外周血和大脑皮质分别采用real-time PCR和TUNEL法等技术检测各组外周血mir-24和大脑皮质内bax基因表达情况和凋亡情况。结果:1次性力竭运动后即刻,大鼠外周血mir-24和大脑皮质内bax基因的表达均升高(P<0.05),24小时后均基本恢复到安静水平(P>0.05),这与TUNEL检测到凋亡情况一致。结论:凋亡可能是运动性疲劳发生的机制之一,外周血mir-24可能作为运动性疲劳的监测指标。