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Background: The appropriate activity of the knee agonist-antagonist muscles is important to resist against abnormal abduction-adduction moments loads around knee joint and reduce the risk of knee injuries. Exercise training has been commonly used as an intervention to improve neuromuscular activity of the synergic and/or agonist-antagonist muscles. However, maximizing the effectiveness of exercise interventions for improving neuromuscular activity between muscle groups has been less investigated. The aim of this study was to investigate the improvement in neuromuscular activity of quadriceps and hamstrings muscles after resistance eccentric training versus concentric training. Methods: 26 male subjects randomly recruited for this controlled laboratory study. Subjects were randomly divided into two groups, eccentric training group (No = 13), and concentric training group (No = 13). Maximal knee extension force and bipolar surface electromyography (EMG) signals from quadriceps and hamstrings muscles were recorded before and after concentric and eccentric strength training. Root mean square (RMS) was computed from raw EMG signals.Results: Percent increase in maximal voluntary isometric contraction (MIVC) of quadriceps muscle after eccentric training was significantly higher than that after concentric training (P < 0.05). Moreover, eccentric training resulted in a greater increase in RMS of EMG for quadriceps and hamstrings muscles compared to concentric exercise training (P < 0.05).Conclusion: The higher increase in neuromuscular activities within the quadriceps and hamstring muscles observed after eccentric exercise may indicate that resistance training using eccentric contraction is more effective in improving neuromuscular activity of the agonist and antagonist muscles.

The effectiveness of eccentric exercise interventions (EEI) has been extensively explored in different populations. The aim of our umbrella review was to combine all systematic reviews about the chronic efficiency of EEI and to summarize the literature on the chronic effects of different types of eccentric exercise protocols, with or without extra loads and devices (e.g., Flywheel device), compared to other therapeutic interventions, exercise interventions, or no intervention. We screened four major electronic scientific databases (PubMed, Scopus, Web of Science, and PEDro), using one combined string for all included databases (eccentric exercise OR flywheel OR isoinertial exercise OR eccentric training). Included reviews needed to be based on any human population, that executed EEI in comparison with any other type of intervention. The methodological quality of the included reviews was assessed using AMSTAR 2 tool. Considering the inclusion criteria, we included 35 reviews. EEI were found suitable for chronic or long-term pain reduction in patient populations. EEI largely improved muscle performance (muscle strength, and muscle power), muscle architecture (e.g., pennation angle, fascicle length, cross-sectional area, muscle thickness, and muscle mass), decreased risk of injury, incidence, and severity of the injury, and increased range of motion of the joints There is less evidence about the effects of EEI in older adult populations, compared to athletes and younger populations, however, eccentric exercise seems promising for these populations as well.

Introduction: The impact of eccentric exercise on mitochondrial function has only been poorly investigated and remains unclear. This study aimed to identify the changes in skeletal muscle mitochondrial respiration, specifically triggered by a single bout of eccentric treadmill exercise. Methods: Male adult mice were randomly divided into eccentric (ECC; downhill running), concentric (CON; uphill running), and unexercised control groups (n = 5/group). Running groups performed 18 bouts of 5 min at 20 cm·s−1 on an inclined treadmill (±15° to 20°). Mice were sacrificed 48 h after exercise for blood and quadriceps muscles collection. Deep proximal (red) and superficial distal (white) muscle portions were used for high-resolution respirometric measurements. Results: Plasma creatine kinase activity was significantly higher in the ECC compared with CON group, reflecting exercise-induced muscle damage (P < 0.01). The ECC exercise induced a significant decrease in oxidative phosphorylation capacity in both quadriceps femoris parts (P = 0.032 in proximal portion, P = 0.010 in distal portion) in comparison with the CON group. This observation was only made for the nicotinamide adenine dinucleotide (NADH) pathway using pyruvate + malate as substrates. When expressed as a flux control ratio, indicating a change related to mitochondrial quality rather than quantity, this change seemed more prominent in distal compared with proximal portion of quadriceps muscle. No significant difference between groups was found for the NADH pathway with glutamate or glutamate + malate as substrates, for the succinate pathway or for fatty acid oxidation. Conclusions: Our data suggest that ECC exercise specifically affects pyruvate mitochondrial transport and/or oxidation 48 h after exercise, and this alteration mainly concerns the distal white muscle portion. This study provides new perspectives to improve our understanding of the mitochondrial adaptation associated with ECC exercise. [ABSTRACT FROM AUTHOR]

Objectives: To compare biceps femoris long head (BFlh) muscle tendon unit and fascicle function during Nordic hamstring exercise (NHE) variations with different hip range of motion.Design: Cross-sectional.Methods: Twelve healthy volunteers (age: 24 ± 4 years; mass: 77 ± 6 kg; height: 177 ± 4 cm) performed two NHE variations: NHE with hips in neutral (fixed) position (conventional NHE); and NHE with hip flexion/extension. BFlh fascicle length behaviour was assessed using a dual transducer ultrasound configuration. BFlh and semitendinosus muscle electromyography, lower limb kinematics and knee flexion moment were also recorded. A biomechanical model was used to estimate BFlh muscle-tendon unit (MTU) length. Statistical Parametric Mapping was used to assess timing differences in outcome variables across the movement.Results: In both variations, during much of the exercise (~30-80% of movement phase), BFlh fascicles undergo little length change (isometric) while the MTU lengthens. Fascicles stretched considerably just in the last ~20% of the exercise, and changes in fascicle length (<2 cm stretch) were smaller in comparison to changes in MTU length (<4 cm stretch). Hip flexion resulted in the muscle tendon unit and fascicles operating at longer lengths until approximately 80% of the movement phase.Conclusions: The decoupling between fascicle and MTU length seen during the NHE variations suggests that stretch of the elastic tissue of the MTU has an important role in absorbing energy during Nordic hamstring exercises. This may be important when considering adaptations to BFlh muscle and connective tissues that might occur from NHE training. [ABSTRACT FROM AUTHOR]

The myotendinous junction (MTJ), a specialized interface for force transmission between muscle and tendon, has a unique transcriptional activity and is highly susceptible to muscle strain injury. Eccentric exercise training is known to reduce this risk of injury, but knowledge of the influence of exercise on the MTJ at the molecular and cellular levels is limited. In this study, 30 subjects were randomized to a single bout of eccentric exercise 1 week prior to tissue sampling (exercised) or no exercise (control). Samples were collected from the semitendinosus as part of reconstruction of the anterior cruciate ligament and divided into fractions containing muscle, MTJ and tendon, respectively. The concentrations of macrophages and satellite cells were counted, and the expression of genes previously known to be active at the MTJ were analyzed by real-time–quantitative PCR. An effect of the single bout of exercise was found on the expression of nestin (NES) and osteocrin (OSTN) mRNA in the MTJ and tendon fractions. Genes earlier identified at the MTJ (COL22A1, POSTN, ADAMTS8, MNS1, NCAM1) were confirmed to be expressed at a significantly higher level in the MTJ compared to muscle and tendon but were unaffected by exercise. In the exercise group a higher concentration of macrophages, but not of satellite cells, was seen in muscle close to the MTJ. The expression of NES and OSTN was higher in human semitendinosus MTJ 1 week after a single session of heavy eccentric exercise. Based on these results, NES and OSTN could have a part in explaining how the MTJ adapts to eccentric exercise. [ABSTRACT FROM AUTHOR]

We investigated whether 20 candidate single nucleotide polymorphisms (SNPs) were associated with in vivo exercise‐induced muscle damage (EIMD), and with an in vitro skeletal muscle stem cell wound healing assay. Sixty‐five young, untrained Caucasian adults performed 120 maximal eccentric knee‐extensions on an isokinetic dynamometer to induce EIMD. Maximal voluntary isometric/isokinetic knee‐extensor torque, knee joint range of motion (ROM), muscle soreness, serum creatine kinase activity and interleukin‐6 concentration were assessed before, directly after and 48 h after EIMD. Muscle stem cells were cultured from vastus lateralis biopsies from a separate cohort (n = 12), and markers of repair were measured in vitro. Participants were genotyped for all 20 SNPs using real‐time PCR. Seven SNPs were associated with the response to EIMD, and these were used to calculate a total genotype score, which enabled participants to be segregated into three polygenic groups: 'preferential' (more 'protective' alleles), 'moderate', and 'non‐preferential'. The non‐preferential group was consistently weaker than the preferential group (1.93 ± 0.81 vs. 2.73 ± 0.59 N ∙ m/kg; P = 9.51 × 10−4) and demonstrated more muscle soreness (p = 0.011) and a larger decrease in knee joint ROM (p = 0.006) following EIMD. Two TTN‐AS1 SNPs in linkage disequilibrium were associated with in vivo EIMD (rs3731749, p ≤ 0.005) and accelerated muscle stem cell migration into the artificial wound in vitro (rs1001238, p ≤ 0.006). Thus, we have identified a polygenic profile, linked with both muscle weakness and poorer recovery following EIMD. Moreover, we provide evidence for a novel TTN gene‐cell‐skeletal muscle mechanism that may help explain some of the interindividual variability in the response to EIMD. [ABSTRACT FROM AUTHOR]

To determine if eccentric exercise was effective, safe and feasible in increasing function and quality of life in people with heart failure compared to usual care and a waitlist control group. A prospective, three-armed, parallel-design, assessor-blind, pilot randomised controlled trial with 1:1:1 allocation. Forty-seven participants (16 female; mean age 66 years) with mild to moderate heart failure were randomly allocated to either eccentric exercise, concentric exercise or a waitlist control group. Participants in the exercise groups completed twice-weekly exercise for eight weeks. Primary outcome was walking capacity. Secondary outcomes were quality of life, leg strength and fatigue. Outcomes were assessed at baseline, post intervention and three-month follow-up. Attendance, tolerability and adverse events were used to determine safety and feasibility. Intention-to-treat analysis showed no differences between eccentric exercise and either concentric exercise or waitlist for any outcome. Per-protocol analysis found improvements identified by the Minnesota living with heart failure questionnaire were significantly greater post-intervention for eccentric exercise compared to concentric exercise (−17.99 units, 95% confidence interval −35.96 to −0.01). No major adverse events were reported. In this small trial, eccentric exercise did not demonstrate superior outcomes to concentric exercise or a waitlist control group. The protocol for this trial was registered at clinicaltrials.gov, registration number: NCT02223624, registration date: 22 August 2014. Regular physical activity and referral to rehabilitation is recommended for people with chronic heart failure, however exercise can be challenging for this group. Eccentric exercise was safe and tolerable for participants with heart failure. Documentation of exercise progression is important to demonstrate a dose–response relationship. In this study there were no differences between groups who received eccentric exercise, concentric exercise or no exercise. [ABSTRACT FROM AUTHOR]

Purpose: Peripheral and central factors play important roles in the reduction of motor performance following damaging eccentric exercise and delayed onset muscle soreness (DOMS). Following this regime, contralateral limbs could also be affected; however, the factors involved remain inconclusive. The purpose of this study was to distinguish the peripheral and central factors following eccentric contraction and DOMS of the plantar flexors in treated and contralateral homologous limbs. Methods: Ten males (BMI = 25.08 ± 1.69kgm−2; age = 28.70 ± 4.24 years) were randomly assigned to experimental (DOM) or control (CON) groups. The DOM group performed a damaging eccentric exercise, while the CON group rested. Plasma creatine kinase (CK), pain rating scale (PRS), muscle stiffness, maximal voluntary contraction (MVC), and neural voluntary activation (VA) were measured before, after 10 min, and after 24, 48, and 72 hr on treated and contralateral limbs. Results: Following exercise, CK increased until after 48 hr, while PRS increased until after 72 hr compared to the CON group. Importantly, MVC was reduced at all time points, with the greatest reduction observed after 24 hr (−16%), while VA was affected until after 48 hr, with the greatest reduction at after 10 min (−7%). Interestingly, a "cross-over effect" was observed in contralateral limbs when PRS, MVC, and VA were negatively affected following the same pattern (time line) as treated limbs (−13% peak MVC reduction; −3.5% peak VA reduction). Conclusion: These findings suggest a substantial central contribution to the reduction in force immediately following eccentric exercise and to a lesser extent during the latter part of DOMS in both treated and contralateral limbs. [ABSTRACT FROM AUTHOR]

Supplementation with cannabidiol (CBD) may expedite recovery when consumed after exercise. The purpose of this study was to determine if supplementation with CBD reduces inflammation and enhances performance following strenuous eccentric exercise in collegiate athletes. Twenty-four well-trained females (age = 21.2 ± 1.8 years, height = 166.4 ± 8 cm, weight = 64.9 ± 9.1 kg) completed 100 repetitions of unilateral eccentric leg extension to induce muscle damage. In this crossover design, participants were randomized to receive 5 mg/kg of CBD in pill form or a placebo 2 h prior to, immediately following, and 10 h following muscle damage. Blood was collected, and performance and fatigue were measured prior to, and 4 h, 24 h, and 48 h following the muscle damage. Approximately 28 days separated treatment administration to control for the menstrual cycle. No significant differences were observed between the treatments for inflammation, muscle damage, or subjective fatigue. Peak torque at 60°/s (p = 0.001) and peak isometric torque (p = 0.02) were significantly lower 24 h following muscle damage, but no difference in performance was observed between treatments at any timepoint. Cannabidiol supplementation was unable to reduce fatigue, limit inflammation, or restore performance in well-trained female athletes. [ABSTRACT FROM AUTHOR]

PURPOSE This study aimed to examine the effects of eccentric exercise (ECC) on the indices of mechanical properties together with markers of exercise-induced muscle damage (EIMD) in different sites of the biceps brachii (BB) muscle. METHODS ECC using an elbow joint was performed in 13 non-trained, college men. Global symptoms of EIMD were identified through changes in muscle soreness and serum creatine kinase (CK) activity, including muscle function following ECC. To evaluate regional EIMD, muscle swelling and tenderness as well as muscular echo intensity were measured at distal (4 cm above the elbow joint) and middle (30% of the distance from the antecubital crease to the acromion) sites within the BB muscle. A handheld myotonometer was used to estimate changes in mechanical properties, that is, oscillation frequency (F), dynamic stiffness (S), and relaxation time (R), of BB muscles after ECC. RESULTS A significant difference in the major markers of EIMD, such as muscle soreness and serum CK activity, along with parameters of muscle function, was observed after ECC compared to baseline. Although all indirect markers of regional muscle damage demonstrated meaningful differences between before and after ECC, no statistically significant interaction between the distal and middle sites was observed in any of the markers. After ECC, both distal and middle sites showed significant changes in F, S, and R, but no statistical differences in changes in muscle mechanical properties were observed between localized muscle sites within BB muscles. CONCLUSIONS Changes in mechanical properties, including regional muscle damage, seem to be uniformly influenced by different anatomical locations within the BB muscle, such as elbow flexors, following ECC.

PURPOSE This study aimed to examine the effect of hydrotherapy at different temperatures following eccentric exercise on muscle damage and recovery profiles in young men. METHODS Male college students without any cardiovascular or orthopedic disorders were randomly assigned to three hydrotherapy groups: a 5°C group (cold water, COLD), a 15°C group (cool water, COOL), and a control group (CON). Thirty maximal eccentric exercises were performed using the participants’ nondominant elbow flexor muscles. Each treatment consisted of immersion five times for 1 minute, along with a 1-minute rest between each immersion trial. Each intervention was conducted immediately after the eccentric exercise and every 24 hours. Changes in the level of exercise-induced muscle damage (EIMD), circumference, muscle soreness, range of motion (ROM), maximum voluntary isometric contraction (MVIC), muscle dynamic stiffness, and muscular echo intensity (EI) were measured. All parameters were measured at 24, 48, 72, and 96 hours after exercise, as well as immediately before and after exercise. RESULTS Muscle soreness was significantly higher in the COLD group than in the other groups. Moreover, the muscle circumference tended to increase in the COLD group than in the other groups. However, an increase in the dynamic stiffness and EI, promoting the recovery of MVIC, was observed in the COOL group. In addition, ROM tended to return more rapidly in the COOL group than in the other groups. CONCLUSIONS This study suggests that hydrotherapy at moderately low temperatures compared with that at extremely low temperatures may induce relatively positive effects on EIMD and recovery phases following eccentric exercise in the arms.

Background: Oxidative stress and inflammation increase after eccentric exercise. Cold-water immersion after exercise is common among athletes to accelerate recovery. Therefore, the purpose of this study was to investigate the effect of cold-water immersion after eccentric exercise on the oxidative and inflammatory responses in skeletal muscle. Methods: One hundred male Wistar rats (weight 285.11 ± 41.65) were randomly divided into control, eccentric exercise, eccentric exercise + normal water, and eccentric exercise + cold water groups. Half, 24, 48, 72, and 168 hours after eccentric exercise, EDL muscle was removed in sterile conditions. The eccentric exercise involves 90 minutes of interval running on the treadmill at a speed of 16 m/min and a -16-degree slope. Muscle reactive oxygen species (ROS) and tumor necrosis factor-alpha (TNF-α) levels were measured by DCFDA and immunohistochemical staining. Kolmogorov-Smirnov for normality test and repeated measure ANOVA and Tukey’s post-Hoc tests for compare groups were used with a significance level of P≤0.05. Results: After eccentric exercise, ROS and TNF-α levels significantly (P

Objective. Unaccustomed or high-intensity eccentric exercise often leads to delayed onset muscle soreness (DOMS) that presents as pain, soreness, or swelling. Nonsteroidal anti-inflammatory medications (NSAIDs) are often used to treat DOMS. Due to the potential adverse effects of NSAIDs, commerically available supplements have been suggested as a potential alternative treatment of DOMS. The purpose of this review is to examine the effects of commerically available supplements on DOMS and markers of muscle damage and inflammation. Method. Existing publications were examined and summarized regarding the effects of supplements such as curcumin, green tea extract, ginseng, ginger, branch chain amino acids, anatabine, pomegranate juice, and protease on DOMS and markers of both muscle damage and inflammation following eccentric exercise. Results. Consuming branched chain amino acids (BCAA), pomegranate, and curcumin appear to have the greatest effect in preventing and treating DOMS. Anatabine and ginseng do not appear to decrease markers of muscle damage, inflammation, or DOMS. Conclusion. Consuming supplements before or after exercise with anti-inflammatory and analgesia properties may be just as effective as NSAIDs in treating and preventing DOMS. Further studies should be conducted to determine the long-term effects of commerically available supplements and the safest dosage that can be consumed for maximal benefits.

• CWI reduced muscle inflammation post-eccentric exercise (ECC). • CWI suppressed NLRP3 inflammasome pathway and inflammatory cytokine production post-ECC. • CWI altered NLRP3-related ubiquitin proteasome proteins in muscle post-ECC. Eccentric exercise (ECC) can induce NLRP3-related inflammation in skeletal muscle tissue. Limited available data have shown that Cold water immersion (CWI) after ECC can suppress skeletal muscle inflammation. This study aims to investigate the effect of CWI after ECC on the NLRP3 inflammasome pathway, and the expression of ubiquitin–proteasome-related proteins (UPPs) in the skeletal muscle of rats. Twenty-five male Wistar rats were randomly divided into control, ECC, ECC + CWI, ECC + NWI (normal water immersion), and ECC + AR (active recovery) groups. The Eccentric exercise consisted of 90 min of downhill running on a treadmill with a speed of 16 m/min and −16° incline. Animals in the NWI and CWI groups were immersed in water at 25 °C and 10 °C after ECC. Eventually, The soleus muscle was isolated and the expression of NLRP3, caspase-1, FBXL2, TRIM31, and PARKIN was evaluated by western blot. Tissue levels of IL-1β and IL-18 were measured by ELISA assay. ECC significantly increased the expression of NLRP3, caspase-1, and the tissue levels of IL-1β and IL-18 compared to the control group. After ECC, FBXL2, and PARKIN were downregulated, whereas TRIM31 was up-regulated (P < 0.05). CWI after ECC suppressed the NLRP3 inflammasome components and increased the protein levels of FBXL2 and TRIM31 at higher levels than other recovery methods (P < 0.05). CWI and AR had the same increase in PARKIN expression and the same decrease in CK level compared to the ECC group (P < 0.05). Our results indicated that CWI increased the expression of NLRP3-related UPPs in concomitant with suppression of NLRP3 in the soleus muscle of rats after ECC. As a result the beneficial effects of CWI on the attenuation of skeletal muscle inflammation may contribute to an alteration of UPPs expression. [ABSTRACT FROM AUTHOR]

The aim of our study was to assess eccentric-exercise-induced changes in passive knee joint torque, passive knee joint stiffness and shear modulus at of the hamstring muscles. We hypothesized that eccentric exercise would elicit an increase in all outcomes. Fourteen healthy volunteers (age = 25.5±4.7 years) performed eccentric exercise protocol. Before and after 0h, 1h, 24h and 48h, we measured the shear modulus of hamstring muscles using shear-wave elastography and passive knee joint stiffness on isokinetic dynamometer. After eccentric exercise, the shear modulus of biceps femoris increased after 0h (22.4 ± 34.1 %; p = 0.021) and for semitendinosus after 0h (14.5 ± 4.9 %), 1h (16.2 ± 6.5 %) and 24h (16.6 ± 8.3 %) (p = 0.005-0.015). There were no changes for semimembranosus and no changes in passive knee joint moment measures. There were also no correlations between the two methods. Eccentric exercise increased shear modulus of hamstring muscles, while passive joint torque was not affected. This suggests that shear-wave elastography could be more sensitive than torque measures to intra-muscular changes induced by eccentric exercise.

Context: Eccentric exercises are increasingly being used to treat lower-limb musculoskeletal conditions such as Achilles tendinopathy. Despite widespread clinical application and documented efficacy, mechanisms underpinning clinical benefit remain unclear. Positive adaptations in motor performance are a potential mechanism. Objective: To investigate how an eccentric loading intervention influences measures of stretch-shortening-cycle (SSC) behavior during a hopping task. Design: Within-subjects repeated-measures observational study. Setting: University motion-analysis laboratory. Participants: Healthy adults. Interventions: A single intervention of 5 sets of 10 eccentric plantar-flexion contractions at 6 repetitions maximum using a commercial seated calf-raise machine. Main Outcome Measures: Lower-limb stiffness, sagittal-plane ankle kinematics, and temporal muscle activity of the agonist (soleus) and antagonist (tibialis anterior) muscles, measured during submaximal hopping on a custom-built sledge-jump system. Results: Eccentric loading altered ankle kinematics during submaximal hopping; peak angle shifted to a less dorsiflexed position by 2.9° and ankle angle precontact shifted by 4.4° (P < .001). Lower-limb stiffness increased from 5.9 to 6.8 N/m (P < .001), while surface EMG measures of soleus occurred 14--44% earlier (P < .001) after the loading intervention. Conclusions: These findings suggest that eccentric loading alters SSC behavior in a manner reflective of improved motor performance. Decreased ankle excursion, increased lower-limb stiffness, and alterations in motor control may represent a positive adaptive response to eccentric loading. These findings support the theory that mechanisms underpinning eccentric loading for tendinopathy may in part be due to improved "buffering" of the tendon by the neuromuscular system. [ABSTRACT FROM AUTHOR]

Abstracts PURPOSE The present study aimed to investigate the effects of transdermal application of methylsulfonylmethane (MSM) on muscle damage and recovery following eccentric exercise in young men. METHODS Eleven college-aged men without any cardiovascular or orthopedic disorders underwent two sessions consisting of a control session (CS) and an experimental session (ES) in a random order with at least 2 weeks of wash-out between the sessions. The participants performed 30 maximal eccentric exercises involving their non-dominant elbow flexors in each session. Circumference, muscle soreness, range of motion, maximal voluntary isometric contraction (MVIC), and muscular echo intensity (EI) were measured to evaluate the changes in the level of exercise-induced muscle damage (EIMD). All measurements were performed at 24, 48, 72, and 96 hours after exercise and also immediately before and after exercise. RESULTS Transdermal application of MSM in ES attenuated muscle swelling and decreased MVIC after eccentric exercise when compared with CS. Muscle soreness and EI tended to increase less rapidly and decrease more rapidly in ES than in CS. CONCLUSIONS Transdermal application of MSM may induce relatively positive effects on EIMD and recovery following eccentric exercise when compared with the treatment that has been widely used previously.

Abstract Background To explore the value of magnetic resonance quantitative analysis using diffusion tensor imaging, T2 mapping, and intravoxel incoherent motion in the evaluation of eccentric exercise-induced muscle damage and to compare the effects of various eccentric exercise modes at different time points in rats. Methods A total of 174 Sprague-Dawley male rats were randomly divided into five groups: control, once-only exercise, continuous exercise, intermittent exercise, and once-fatigue exercise groups. Each experimental group was divided into seven time-subgroups: 0.5 h, 24 h, 48 h, 72 h, 96 h, 120 h and 168 h after exercise. The quadriceps femoris muscles were then scanned using magnetic resonance imaging. The apparent diffusion coefficient and fractional anisotropy values of diffusion tensor imaging, T2 values of T2 mapping, D and D* values of intravoxel incoherent motion and optical density values of desmin were measured. Associations among different eccentric exercise programmes, magnetic resonance imaging findings, and histopathological results were evaluated. Dunnett’s test, two-way repeated measures analysis of variance, and Pearson correlation analysis were used for statistical analysis. Results Diffusion tensor imaging showed that the number of muscle fibre bundles decreased to varying degrees with different time points and eccentric exercises. Apparent diffusion coefficient values of the exercise groups showed a trend that first increased and then decreased, the opposite of fractional anisotropy. The specimens in all eccentric exercise programmes showed high signal T2 values after exercise, the highest among which was in the once-fatigue exercise group. D and D* in the experimental groups were significantly higher than those in the control group at 0.5–48 h after exercise. The apparent diffusion coefficient, fractional anisotropy, T2, D and D* values correlated with the optical density values of desmin. Conclusions Diffusion tensor imaging, T2 mapping, and intravoxel incoherent motion technology accurately reflect the degree of skeletal muscle damage and recovery associated with eccentric exercise. The degree of muscle damage was the lowest in the continuous exercise group and the highest in the once-fatigue exercise group, which may provide more information and guidance for the formulation of physical and athletic training programmes.

Investigation of the contralateral repeated bout effect (CL-RBE) in women is scarce. Therefore, this study aimed at examining whether CL-RBE exists in women. Twelve healthy women (age: 20.9 ± 2.5 years) performed two bouts of maximal elbow flexor eccentric exercise (3 sets × 15 repetitions per bout) separated by 14 days, using the opposite arms. Surface Electromyography (EMG) was recorded during both exercise bouts. The isokinetic muscle strength (60°/s), muscle soreness, range of motion (ROM), limb girth, and blood creatine kinase activity were measured pre-exercise, and at 24 and 48 h post-exercise with the muscle strength being measured immediately post-exercise as well. Significant main effects of time were observed for muscle strength, muscle soreness and ROM (p < 0.05). There were no significant differences between bouts for all the measured variables including the EMG median frequency (p > 0.05). These results suggest that the CL-RBE of elbow flexors was not evident in young healthy women. This was because the mild muscle damage induced by the initial bout of exercise was either not enough to initiate the CL-RBE or the CL-RBE in women lasted shorter than two weeks. This study provides important information for future studies on CL-RBE in women.

In this study, we aimed to assess acute changes occurring on atrial function following single bouts of eccentric resistance exercise (ECC-RE) performed at two different loads. Twenty-five patients with chronic heart failure with middle range ejection fraction (HFmrEF) participated in three experimental sessions in a randomized order and on separate days: two sessions of ECC RE at 20% (ECC-20) of one-repetition maximum (1-RM) and 50% (ECC-50) 1-RM, and one session of control, without exercise. Each session lasted three minutes. Before and immediately after the sessions, patients underwent echocardiography and blood pressure and heart rate measurement. Peak atrial longitudinal strain (PALS) and peak atrial contractile strain (PACS) significantly increased after both ECC-20 (+16.3%) and ECC-50 (+18.1%) compared to control (between sessions p = 0.022). Peak atrial contractile strain (PACS) significantly increased after ECC-50 (+28.4%) compared to ECC-20 (+17.0%) and control (between sessions p = 0.034). The ratio of transmitral and annular velocities (E/E') increased significantly after ECC-20 (+10.4%) and ECC-50 (+19.0%) compared to control (between groups p = 0.003). EF, left ventricular longitudinal strain, and stroke volume did not change after ECC-RE sessions compared to control. Cardiac output increased significantly after ECC-20 and ECC-50 compared to control, (between groups p = 0.025). In conclusion, both ECC-RE sessions were well tolerated, and LA functional reserve was properly mobilized in response to ECC-RE in patients with HFmrEF. Cardiac output increased at the cost of an increased LV filling pressure, but no detrimental changes of LV function occurred. [ABSTRACT FROM AUTHOR]

• Repeated bout effect resulted in a better preservation of neural drive that led to an attenuated MVC loss after second bout of downhill running. • Repeated bout effect after downhill running was observed on some level running biomechanical variables such as center of mass excursion. • The observed repeated bout effect on running biomechanics did not substantially translate to energy cost of running. This study used downhill running as a model to investigate the repeated bout effect (RBE) on neuromuscular performance, running biomechanics, and metabolic cost of running. Ten healthy recreational male runners performed two 30-min bouts of downhill running (DR1 and DR2) at a –20% slope and 2.8 m/s 3 weeks apart. Neuromuscular fatigue, level running biomechanics during slow and fast running, and running economy parameters were recorded immediately before and after the downhill bouts, and at 24 h, 48 h, 72 h, 96 h, and 168 h thereafter (i.e., follow-up days). An RBE was confirmed by attenuated muscle soreness and serum creatine kinase rise after DR2 compared to DR1. An RBE was also observed in maximum voluntary contraction (MVC) force loss and voluntary activation where DR2 resulted in attenuated MVC force loss and voluntary activation immediately after the run and during follow-up days. The downhill running protocol significantly influenced level running biomechanics; an RBE was observed in which center of mass excursion and, therefore, lower-extremity compliance were greater during follow-up days after DR1 compared to DR2. The observed changes in level running biomechanics did not influence the energy cost of running. This study demonstrated evidence of adaptation in neural drive as well as biomechanical changes with the RBE after DR. The higher neural drive resulted in attenuated MVC force loss after the second bout. It can be concluded that the RBE after downhill running manifests as changes to global and central fatigue parameters and running biomechanics without substantially altering the energy cost of running. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: The neuromuscular system is able to quickly adapt to exercise-induced muscle damage (EIMD), such that it is less affected by subsequent damaging exercise, a phenomenon known as the repeated bout effect (RBE). The objective was to determine whether the mechanical properties of the quadriceps, as evaluated by shear wave elastography (SWE), were less affected when a second bout of eccentric-biased exercise was performed 2 weeks later. It was hypothesized that the first bout would confer protection against extensive muscle damage through an adaptation of the muscle stiffness before the second bout (i.e., higher muscle stiffness). Methods: Sixteen males performed two identical bouts of downhill walking separated by 2 weeks (45 min at 4.5 km.h−1; gradient: 25%; load: 30% of the body mass). Rectus femoris (RF) and vastus lateralis (VL) resting shear elastic modulus (µ) and EIMD symptoms were measured before and up to 7 days following the exercise bouts. Changes in neuromuscular function was evaluated by maximal voluntary contraction torque, voluntary activation level, evoked mechanical response to single and double (10 and 100 Hz doublets) electrical stimulation. An index of protection (IP) was calculated for EIMD symptoms to assess magnitude the RBE. Results: EIMD symptoms were less affected after the second than the first exercise bout. RF and VL-µ increased (p < 0.001) only after the first exercise. RF µ was elevated up to 2 weeks after the end of the first exercise (p < 0.001) whereas VL µ was only increased up to 24 h. The increase in µ observed 2 weeks after the end of the first exercise was correlated with the IP; i.e., attenuation of alterations in muscle µ, 10 Hz-doublet amplitude and rate of torque development after the second exercise bout (p < 0.05). Conclusion: We showed that muscle µ assessed by SWE was sensitive to the RBE, with a differential effect between VL and RF. The persistent increase in µ was associated with the attenuation of neuromuscular impairments observed after the second bout, suggesting that the increased muscle stiffness could be a "protective" adaptation making muscles more resistant to the mechanical strain associated to eccentric contractions. [ABSTRACT FROM AUTHOR]

The aim of our study was to assess eccentric-exercise-induced changes in passive knee joint torque, passive knee joint stiffness and shear modulus at of the hamstring muscles. We hypothesized that eccentric exercise would elicit an increase in all outcomes. Fourteen healthy volunteers (age = 25.5±4.7 years) performed eccentric exercise protocol. Before and after 0h, 1h, 24h and 48h, we measured the shear modulus of hamstring muscles using shear-wave elastography and passive knee joint stiffness on isokinetic dynamometer. After eccentric exercise, the shear modulus of biceps femoris increased after 0h (22.4 ± 34.1 %; p = 0.021) and for semitendinosus after 0h (14.5 ± 4.9 %), 1h (16.2 ± 6.5 %) and 24h (16.6 ± 8.3 %) (p = 0.005-0.015). There were no changes for semimembranosus and no changes in passive knee joint moment measures. There were also no correlations between the two methods. Eccentric exercise increased shear modulus of hamstring muscles, while passive joint torque was not affected. This suggests that shear-wave elastography could be more sensitive than torque measures to intra-muscular changes induced by eccentric exercise. [ABSTRACT FROM AUTHOR]

Key summary points: Aim: To systematically review the literature on the effectiveness of eccentric exercise interventions in reducing falls and improving the functional performance in older adults. Findings: The existing literature was of mixed quality and suggested that eccentric exercises can be as effective as conventional exercises in improving functional performance in healthy older adults. There was limited evidence focussing on the aspect of incidence of falls. Message: Eccentric exercises may be as effective as conventional exercises in improving geriatric function, although evidence remains limited. More research is needed to explore any adverse effects of such exercises in older adults. Background: Exercise has been known to preserve and enhance functional performance in older adults. Eccentric exercise involves muscle contractions characterised by unique features such as lengthening of the muscle–tendon complex by a greater opposing force. Aims: To systematically review randomised-controlled trials (RCTs) investigating the effectiveness of eccentric exercises in reducing the incidence of falls and improving the functional performance in older adults. Key methods: We conducted a systematic review of RCTs following the PRISMA-P guidelines. Searches were completed in the Cochrane Central Register of Controlled Trials, Embase, CINAHL, Medline, and Global Health CABI. We included RCTs reporting at least one of the following outcomes—falls, Berg balance scale, timed-up and go test, chair stand test, stair climb test, maximal walking speed, and minute walking distance. Two reviewers screened papers for eligibility and assessed the quality of included papers using the Cochrane Collaborative risk-of-bias tool for randomised trials. Data were extracted by a single reviewer and cross-checked by the second reviewer. A narrative synthesis was undertaken, given the high level of heterogeneity across studies. Results: Ten studies were assessed as eligible for inclusion in the review. Overall, eccentric exercises were as effective as conventional resistance exercises in improving the selected outcomes by most studies. Additionally, when pre-exercise and post-eccentric exercise functional performance measures were compared, there was a statistically significant improvement in nearly all measures. The quality of trials was mixed (one high, four moderate, two low–moderate, and three low risk of bias). Conclusions: Our systematic review suggests that eccentric exercises can be as effective as conventional exercises in older adults. Evidence suggests that such exercise interventions can lead to an improvement in geriatric function. [ABSTRACT FROM AUTHOR]

Introduction Nigella sativa is known to have potent anti-inflammatory effects. Thus, the present study investigated the hypothesis that Nigella sativa ingestion would reduce muscle damage and inflammation after eccentric exercise. Material and methods Twenty sedentary men aged 19 to 27 years were assigned to 2 groups, either Nigella sativa (N) or control (C). N group was administered 2000mg/day of Nigella sativa from 2 weeks before exercise to 4 days post-exercise and C group was administered a placebo. They underwent 10 sets X 10 repetitions of counter-movement jump (CMJ) with 30-second rest between each set, employing squat in starting and landing position to facilitate muscle damage. A set of tests were conducted to measure indirect muscle damage and inflammation markers (muscular power, range of motion (ROM), thigh circumference, soreness, creatine kinase [CK]; interleukin-6 [IL6] and interleukin-1β [IL-1β]) at pre-exercise, 30 minutes, 1-, 2-, 3- and 4-days post-exercise. Changes in these parameters over time were compared between N and C groups by two-way repeated-measures ANOVA. Results Significant changes were noted in muscular power, ROM, thigh circumference, soreness and CK from pre-exercise at most of the measurement sessions for N and C groups (p<0.05), but no significant changes were marked in IL-6 and IL-1β at all measurement sessions for N and C groups (p>0.05). There were also no significant differences between groups for all markers of muscle damage and inflammation at all measurement sessions (p>0.05). Discussions and conclusion Significant changes in muscular power, ROM, thigh circumference, soreness and CK from pre-exercise at most of the measurement sessions for both groups suggested that the eccentric exercise model used in this study was enough to induce muscle damage, but it might be too mild to activate the inflammatory cytokines. No significant differences between groups for all markers of muscle damage and inflammation at all measurement sessions suggested that Nigella sativa ingestion does not attenuate indirect markers of muscle damage and inflammation following mild eccentric exercise model. [ABSTRACT FROM AUTHOR]

Peak eccentric force during the Nordic hamstring exercise (NHE) is recognized as a predictive factor for hamstring strain injury (HSI). During the NHE, the knee flexor muscles are eccentrically contracting to resist the knee joint extension. Therefore, it is thought that the action of the gastrocnemius muscle, and thus the ankle position, influences peak eccentric force during the NHE. However, the effect of ankle position on peak eccentric force during the NHE remains unclear. Therefore, we investigated the effect of ankle position on peak eccentric force during the NHE in a cohort of 50 healthy young male rugby players (mean age, 18.7 ± 1.2 years; mean body mass, 81.7 ± 15.2 kg; height, 1.72 ± 0.06 m) with no history of HSI. Each participant performed NHE strength testing with the ankle dorsiflexed or plantarflexed position and was instructed to fall forward as far as possible within 3 s. Peak eccentric force, reported relative to body mass (N/kg), of both legs was recorded, and the mean values of both legs were compared in both ankle positions. The mean peak eccentric force was significantly greater with the ankle plantarflexed position than the dorsiflexed position (3.8 ± 1.1 vs. 3.5 ± 1.1 N/kg, respectively, p = 0.049). These results indicate that ankle position should be carefully considered when measuring peak eccentric force during the NHE and performing NHE training. [ABSTRACT FROM AUTHOR]

Upper-body resistance exercise effectively increases muscular strength, but may concomitantly increase arterial stiffness. Eccentric exercise can lead to muscle soreness and arterial stiffness in untrained participants. However, it is unclear if upper-body eccentric exercise could reduce arterial stiffness in a single session for participants that have undergone progressive training. Our purpose was to compare acute responses to upper-body eccentric (novel, ECCarm) and concentric (traditional, CONarm) steady state arm cycling. We hypothesized that arm arterial stiffness would be reduced after both ECCarm and CONarm. Twenty-two young healthy individuals performed either ECCarm (n = 11) or CONarm (n = 11) at ~70% of peak heart rate for 20 min after a training period. Heart rate, central pulse wave velocity (cPWV), and peripheral pulse wave velocity (pPWV; i.e., arm arterial stiffness) were assessed before, 10 min, and 30 min after exercise. Heart rate was not elevated at 10 min post ECCarm, but was elevated at 10- and 30-min post CONarm (p < 0.01). After exercise, pPWV was decreased at 10 min post for both ECCarm (7.1 ± 0.3 vs. 6.5 ± 0.2 m/s) and CONarm (7.0 ± 0.2 vs. 6.5 ± 0.2 m/s; p < 0.05), while both groups returned to baseline values 30 min post. cPWV did not change in either group. Our results indicate that acute ECCarm provides a high-force, low energy cost form of resistance exercise that acutely reduces arm arterial stiffness. The reduction in pPWV and rapid heart rate recovery suggests that ECCarm is a safe form of exercise for overall and cardiovascular health. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of elastic tape compared to placebo tape and static stretching on recovery of anaerobic power after intensive exercise in untrained females. Thirty-two untrained female volunteers were randomized into an elastic tape (n= 11), a placebo tape (n = 11) or a stretching group (n =10). Prior to, and for up to 7 days after exhaustive eccentric exercise, Kinesio elastic tape and placebo tape were applied to the dominant quadriceps of taping groups, while the stretching group performed static stretching on the quadriceps for 30s x 10 sets 3 times a day. There was no significant difference in muscle pain, creatine kinase, maximum isometric voluntary contraction, jump height and anaerobic power between the three groups over the course of the study. In untrained females, elastic tape did not improve recovery of anaerobic power after exhaustive eccentric exercise compared to placebo tape or static stretching with no tape.

Manipulating resistance training program variables is a commonly used tool for optimizing maximum muscle strength in rehabilitation and/or exercise training programs. The current study purposed to compare the effects of 12 weeks of concentric and eccentric resistance training on neuromuscular adaptation of quadriceps muscle. Methods Twenty-six male subjects (age, mean ± SD, 22.1 ± 2.4 yr; body mass, 72.3 ± 9.9 kg; height, 1.75 ± 0.08 m) were recruited for this controlled laboratory study. Subjects were randomly divided into two groups: the eccentric training group (No = 13) and the concentric training group (No = 13). The maximal isometric voluntary contraction (MVIC) of quadriceps muscles, vertical jumping, and surface electromyography (EMG) signals were recorded before and after 12 weeks of resistance concentric and eccentric training. Repeated-measures Analysis of Variance (ANOVA) was used to test differences between means before and after resistance training. Results The maximal isometric voluntary contraction of the quadriceps muscle and vertical jumping were significantly increased after eccentric and concentric training (p

Abstract This study examined the effects of low-intensity eccentric exercise training performed before high-intensity eccentric exercise on muscle damage markers, oxidative stress and antioxidant defense. Twenty-two rats were divided into 3 groups; control (CON; n = 6), high-intensity eccentric exercise (HE; n = 8) and low-intensity eccentric exercise training plus high-intensity eccentric exercise (LET + HE; n = 8). Rats in the HE group performed HE at once. Rats in the LET + HE group performed LET and then HE protocol was applied. Blood and vastus intermedius muscle samples were taken 24 hours after the last exercise session for analyses of muscle damage, oxidative stress, and antioxidant defense markers. Muscle damage markers were higher in the HE group than the CON (137%-488%) and the LET + HE groups (82%-110%) (P < 0.05). Oxidative stress marker was higher in the HE group than the CON (65%) and the LET + HE (50%) groups (P < 0.05). Antioxidant defense markers were higher in the LTE + HE group than the HE group (39%-51%) (P < 0.05). In conclusion, low-intensity eccentric exercise training performed before high-intensity eccentric exercise conferred a protective effect against muscle damage by reducing oxidative stress and increasing antioxidant defense.

Background: The neuromuscular system is able to quickly adapt to exercise-induced muscle damage (EIMD), such that it is less affected by subsequent damaging exercise, a phenomenon known as the repeated bout effect (RBE). The objective was to determine whether the mechanical properties of the quadriceps, as evaluated by shear wave elastography (SWE), were less affected when a second bout of eccentric-biased exercise was performed 2 weeks later. It was hypothesized that the first bout would confer protection against extensive muscle damage through an adaptation of the muscle stiffness before the second bout (i.e., higher muscle stiffness).Methods: Sixteen males performed two identical bouts of downhill walking separated by 2 weeks (45 min at 4.5 km.h−1; gradient: 25%; load: 30% of the body mass). Rectus femoris (RF) and vastus lateralis (VL) resting shear elastic modulus (µ) and EIMD symptoms were measured before and up to 7 days following the exercise bouts. Changes in neuromuscular function was evaluated by maximal voluntary contraction torque, voluntary activation level, evoked mechanical response to single and double (10 and 100 Hz doublets) electrical stimulation. An index of protection (IP) was calculated for EIMD symptoms to assess magnitude the RBE.Results: EIMD symptoms were less affected after the second than the first exercise bout. RF and VL-µ increased (p < 0.001) only after the first exercise. RF µ was elevated up to 2 weeks after the end of the first exercise (p < 0.001) whereas VL µ was only increased up to 24 h. The increase in µ observed 2 weeks after the end of the first exercise was correlated with the IP; i.e., attenuation of alterations in muscle µ, 10 Hz-doublet amplitude and rate of torque development after the second exercise bout (p < 0.05).Conclusion: We showed that muscle µ assessed by SWE was sensitive to the RBE, with a differential effect between VL and RF. The persistent increase in µ was associated with the attenuation of neuromuscular impairments observed after the second bout, suggesting that the increased muscle stiffness could be a “protective” adaptation making muscles more resistant to the mechanical strain associated to eccentric contractions.

The effects of eccentric exercise (ECC) in older adults have received limited scientific attention, considering the ample evidence for its effectiveness in general and athletic populations. The purpose of this paper is to review the effects of ECC exercise modalities vs. traditional or concentric (CON) exercise on muscle strength, body composition and functional performance in older adults. Inclusion criteria regarding the age was >55 years. Three major scientific literature databases (PubMed, Scopus and Web of Science) were screened for trials comparing the effect of ECC and CON exercise programs, and 19 papers were included in the meta-analysis. ECC and CON training programs were typically matched by the duration of each session. The difference between ECC and CON was expressed as standardized mean difference (SMD). Regarding isometric knee strength, the pooled effect favored ECC (SMD = 0.50), but was not statistically significant (p = 0.160). ECC exercise elicited greater improvements in timed up and go test (SMD = −0.68; p = 0.004), 2-min sit-stand test (SMD = 0.53; p = 0.030) and 30-s sit-stand test (SMD = 0.81; p = 0.002), but not in 6-min walking test (SMD = 0.01; p = 0.960). The effects on body composition and muscle architecture were unclear (SMD = −1.44 to 1.95; p = 0.060–0.689). In conclusion, our literature review indicates that ECC exercise is superior to, or at least as good as CON exercise for preserving health and overall function in older adults.

Exercise is important for prevention of sarcopenia in the elderly population. We tested two training modalities, ascending or descending stair walking, representing concentric (CON) and eccentric (ECC) exercise, respectively. We also tested the effects of additional weight during eccentric exercise (ECC+). Thirty-two healthy men and women (70 ± 3 [mean ± SE] yrs.) were randomly assigned to CON, ECC, or ECC+ (carrying +15% of body weight in a vest) in a 3 (n = 32) or 6 (n = 21) week intervention (3 sessions/week). Data was analysed by mixed models approach. Rate of perceived exertion (RPE; Borg scale 6-20; mean values from 3 and 6 weeks) during training did not differ between CON (12.3 ± 0.4), ECC (11.5 ± 0.3), and ECC+ (11.7 ± 0.4). After 6 weeks, leg muscle mass increased more in ECC+ (+0.29 ± 0.09 kg) vs CON (+0.08 ± 0.05 kg) (P<0.05) but not different from ECC (+0.16 ± 0.06 kg). 6-minute walk test (6MWT) increased after 6 weeks more (P<0.05) in ECC+ (+85 ± 23 m) compared with ECC (+37 ± 13 m) and CON (+27 ± 12 m). Intramyocellular glycogen content increased from 359 ± 19 nmol/mg d.w. in CON (to 511 ± 65 and 471 ± 44 after 3 and 6 wks, respectfully (P<0.05)), but not in ECC (to 344 ± 28 after 6 weeks) or in ECC+ (to 389 ± 20 after 6 weeks). Conclusion: carrying extra weight while descending stair walking do not increase RPE, but the ECC+ training resulted in greater muscle responses compared with CON, but glycogen synthesis was stimulated only in CON. Descending stairs is a simple model for prevention and treatment of sarcopenia and the stimulus is enhanced by carrying extra weights. [ABSTRACT FROM AUTHOR]

Our aim was to investigate whether hyperthermia before exercise protects against exercise-induced skeletal muscle damage. Two hyperthermia protocols were evaluated. In the first, male ICR mice were exposed to 30 min of whole-body heat in an environmental chamber at an ambient temperature of 42 °C. Heat-exposed and non-heat-exposed mice subsequently completed 60 min of downhill running on a treadmill, 24 h after exposure. Heat exposure significantly increased HSP70 and HSP25 content in the soleus muscle compared to controls. Plasma creatine kinase, muscle β-glucuronidase, and histochemical (hematoxylin and eosin stain) analysis demonstrated that muscle damage was lower in the heatexposed mice than in the non-heat-exposed mice. In the second, the effect of regional heating of the legs, by microwave diathermy, on the prevention of exercise-induced muscle damage was evaluated in male Wistar rats. Microwave-treated and nonmicrowave- treated rats again completed the running protocol 24 h after exposure. Microwave diathermy increased the muscle temperature to 40 °C, significantly increased HSP70 and HSP25 content in the soleus muscle, and significantly attenuated exercise-induced muscle damage. Therefore, hyperthermia before exercise increases skeletal muscle HSPs and attenuates the risk of exercise-induced muscle injury. [ABSTRACT FROM AUTHOR]

Active recovery offers an efficient method to relieve delayed onset muscle soreness and recover from exercise-induced muscle damage (EIMD). The main aim of this systematic review is to identify and compare different active recovery protocols after EIMD. Six databases were searched, and 17 eligible studies were selected. Results showed alleviation of soreness, prevention of muscle strength loss, improvement in flexibility, and a decrease in inflammation after one or more recovery protocols such as isolated muscle contractions, aqua exercise, yoga, and combined jogging and running. A better strategy should focus on prevention of symptoms after EIMD through a precise training periodization and adjustment of load used in exercises. [ABSTRACT FROM AUTHOR]

The aim was to investigate the potential differences in muscle (vastus lateralis) and cerebral (prefrontal cortex) oxygenation levels as well as in the number of repetitions and total work output between isokinetic eccentric and concentric exercise at a moderate relative intensity until exhaustion. Ten recreationally active young men underwent two isokinetic exercise sessions either concentric or eccentric, one on each randomly selected leg. The protocols were performed at 60°/s and an intensity corresponding to 60% of the maximal voluntary contraction (MVC) of each contraction type. Concentric torque was significantly lower compared to eccentric torque in both peak values and at values corresponding to 60% of MVC [230 ± 18 Nm vs. 276 ± 19 Nm (P =.014) and 137 ± 12 Nm vs. 168 ± 11 Nm, respectively (P =.010)]. The participants performed 40% more contractions during eccentric compared to concentric exercise [122 ± 15 vs. 78 ± 7, respectively]. No differences were found in the levels of oxyhaemoglobin, deoxyhemoglobin, total haemoglobin and tissue saturation index when eccentric and eccentric exercise regimes were compared (all P >.05). Our results demonstrate that eccentric exercise of moderate intensity leads to greater resistance to fatigue and more work output compared to concentric exercise, despite the comparable muscle and cerebral oxygenation levels. [ABSTRACT FROM AUTHOR]

Purpose: Recently, it has been suggested that a cellular pathway composed of integrin, integrin-linked kinase (ILK), rapamycin-insensitive companion of mTOR (RICTOR), and Akt may facilitate long-term structural and functional adaptations associated with exercise, independent of the mTORC1 pathway. Therefore, we examined changes in integrin-ILK-RICTOR-Akt protein in vastus lateralis (VL) before and after 8 wk of eccentric cycling training (ECC), which was expected to increase muscle function and VL cross-sectional area (CSA). Methods : Eleven men (23 +/- 4 yr) completed 24 sessions of ECC with progressive increases in intensity and duration, resulting in a twofold increase in work from the first three (75.4 +/- 14.1 kJ) to the last three sessions (150.7 +/- 28.4 kJ). Outcome measures included lower limb lean mass, VL CSA, static strength, and peak and average cycling power output. These measures and VL samples were taken before and 4-5 d after the last training session. Results : Significant (P < 0.05) increases in integrin-[beta]1 (1.64-fold) and RICTOR (2.99-fold) protein as well as the phosphorylated-to-total ILK ratio (1.70-fold) were found, but integrin-[alpha]7 and Akt did not change. Increases in lower limb, thigh, and trunk lean mass (2.8%-5.3%, P < 0.05) and CSA (13.3% +/- 9.0%, P < 0.001) were observed. Static strength (18.1% +/- 10.8%) and both peak (8.6% +/- 10.5%) and average power output (7.4% +/- 8.3%) also increased (P < 0.05). However, no significant correlations were found between the magnitude of increases in protein and the magnitude of increases in CSA, static strength, or power output. Conclusions: In addition to increased muscle mass, strength, and power, we demonstrate that ECC increases integrin-[beta]1 and RICTOR total protein and p-ILK/t-ILK, which may play a role in protection against muscle damage as well as anabolic signaling to induce muscle adaptations. [ABSTRACT FROM AUTHOR]

Introduction: Deficiency in the neural control of movement is associated with poor posture and skeletal muscle injuries. Exercise training is commonly reported as an intervention to improve neuromuscular activity. However, maximizing the effectiveness of exercise interventions for improving neural control of movement has been less investigated. The purpose of the current study was to examine improvement in neuromuscular activity (e.g., muscle fiber conduction velocity) and quadriceps function after eccentric resistance training versus concentric training. Materials and Methods: A total of 24 men participated in this study and were randomly divided into eccentric training (n=12) and concentric training groups (n=12). Maximal voluntary isometric contraction (MIVC) of quadriceps, vertical jumping, and multichannel surface electromyography (EMG) signals were recorded before and 12 weeks after resistance eccentric and concentric training. Muscle fiber conduction velocity (MFCV) and root mean square (RMS) were computed using raw EMG signals. Results: The percentage increases in MVIC and vertical jumping after eccentric resistance training were significantly higher than those after concentric training (P<0.05). Likewise, eccentric exercise resulted in a higher increase in MFCV and RMS of EMG than concentric exercise (P<0.05). Conclusion: A higher increase in neuromuscular activity and quadriceps performance observed after eccentric exercise may indicate that eccentric resistance training is more effective in improving neuromuscular activity and muscle function. [ABSTRACT FROM AUTHOR]

Randomized controlled study. Lateral epicondylitis (LE) causes pain and loss of function in the affected limb. Different exercises have been used for the treatment of LE. In recent years, the technique of neuromobilization has been frequently used to treat tendinopathy. However, there is no study that demonstrates the effects of neuromobilization techniques on patients with LE. The aim of the present study was to determine the effects of neuromobilization techniques on pain, grip strength, and functional status in LE patients and to compare them with conservative rehabilitation treatment. A total of 40 patients (26 females and 14 males; age: 42.80 ± 8.91 years) with a history of LE participated in the study. The patients were randomly assigned to two groups: the neuromobilization group and the control group. The neuromobilization group completed a 6-week conservative rehabilitation and radial nerve mobilization program, whereas the control group received conservative rehabilitation therapy only. Both groups underwent a 7-day weekly conservative home rehabilitation program. Pain severity, grip strength, pinch strength, joint motions, and upper extremity functional level were assessed before treatment, at the third week after treatment, and at the sixth week after treatment. There was a significant decrease in all pain scores in favor of the neuromobilization group at week 6 after treatment (at rest: P =.001, effect size (ES) = 0.84; at night: P =.001, ES = 0.91 and during activity: P =.004, ES = 1.06). No significant differences were found for grip strength, pinch strength, joint motions, and functional level in the neuromobilization group, although trends toward better improvement were observed. Radial nerve mobilization techniques are more effective on pain than conservative rehabilitation therapy in LE patients, and this effect continues after treatment. • Neuromobilization is more effective on pain than eccentric exercises. • The effect of neuromobilization on pain lasts longer than eccentric exercises. • We concluded that neuromobilization combined with a conservative treatment program might be more effective in the treatment of lateral epicondylitis. [ABSTRACT FROM AUTHOR]

There is a need to investigate the role of muscle architecture on muscle damage responses induced by exercise. The aim of this study was to determine the effect of muscle architecture and muscle length on eccentric exercise-induced muscle damage responses. Eccentric exercise-induced muscle damage was performed randomly to the elbow flexor (EF), knee extensor (KE), and knee flexor (KF) muscle groups with two week intervals in 12 sedentary male subjects. Before and after each eccentric exercise (immediately after, on the 1st, 2nd, 3rd, and 7th days) range of motion, delayed onset muscle soreness, creatine kinase activity, myoglobin concentration and isometric peak torque in short and long muscle positions were evaluated. Furthermore, muscle volume and pennation angle of each muscle group was evaluated before initiating the eccentric exercise protocol. Pennation angle and muscle volume was significantly higher and the workload per unit muscle volume was significantly lower in the KE muscles compared with the KF and EF muscles (p < 0.01). EF muscles showed significantly higher pain levels at post-exercise days 1 and 3 compared with the KE (p < 0.01 - 0.001) and KF (p < 0.01) muscles. The deficits in range of motion were higher in the EF muscles compared to the KE and KF muscles immediately after (day 0, p < 0.01), day 1 (p < 0.05 - 0.01), and day 3 (p < 0.05) evaluations. The EF muscles represented significantly greater increases in CK and Mb levels at day 1, 3, and 7 than the KE muscles (p < 0.05 - 0.01). The CK and Mb levels were also significantly higher in the KF muscles compared with the KE muscles (p < 0.05, p < 0.01 respectively). The KF and EF muscles represented higher isometric peak torque deficits in all the post-exercise evaluations at muscle short position (p < 0.05 - 0.001) compared with the KE muscle after eccentric exercise. Isometric peak torque deficits in muscle lengthened position was significantly higher in EF in all the post-exercise evaluations compared with the KE muscle (p < 0.05 - 0.01). According to the results of this study it can be concluded that muscle structural differences may be one of the responsible factors for the different muscle damage responses following eccentric exercise in various muscle groups. [ABSTRACT FROM AUTHOR]

Background: Exercise-induced muscle damage (EIMD) results in transient muscle inflammation, strength loss, muscle soreness and may cause subsequent exercise avoidance. Omega-3 (n-3) supplementation may minimise EIMD via its anti-inflammatory properties, however, its efficacy remains unclear. Methods: Healthy males (n = 14, 25.07 ± 4.05 years) were randomised to 3 g/day n-3 supplementation (N-3, n = 7) or placebo (PLA, n = 7). Following 4 weeks supplementation, a downhill running protocol (60 min, 65% V̇O2max, − 10% gradient) was performed. Creatine kinase (CK), interleukin (IL)-6 and tumour necrosis factor (TNF)-α, perceived muscle soreness, maximal voluntary isometric contraction (MVIC) and peak power were quantified pre, post, and 24, 48 and 72 h post-EIMD. Results: Muscle soreness was significantly lower in N-3 vs PLA group at 24 h post-EIMD (p = 0.034). IL-6 was increased in PLA (p = 0.009) but not in N-3 (p = 0.434) following EIMD, however, no significant differences were noted between groups. Peak power was significantly suppressed in PLA relative to pre-EIMD but not in N-3 group at 24 h post-EIMD. However, no significant difference in peak power output was observed between groups. MVIC, CK and TNF-α were altered by EIMD but did not differ between groups. Conclusion: N-3 supplementation for 4 weeks may successfully attenuate minor aspects of EIMD. Whilst not improving performance, these findings may have relevance to soreness-associated exercise avoidance. [ABSTRACT FROM AUTHOR]

The purpose of this study is to identify if participation in an eccentric exercise protocol altered the Cole-impedance model parameters that represent localized bicep tissue bioimpedance. This supports continued efforts to identify which features of tissue bioimpedance may be effective markers to non-invasively identify skeletal muscle damage. Here, the Cole-impedance model parameters that best fit the localized electrical impedance of exercised (using an eccentric stimulus) and unexercised biceps of 6 participants (collected before, immediately after and at 24 h, 48 h, 72 h and 96 h) are determined using a numerical optimization technique. Statistical tests comparing the pre-exercise and post-exercise model parameters report significant decreases in R∞ and R1 with significant increases in C at 72 h and 96 h post-exercise for exercised biceps (aligning with noted periods of peak swelling). These changes in R∞,R1, and C were not observed in the unexercised biceps. These results support that the C parameter of the Cole-impedance model fit to bioimpedance data may be a suitable marker for identifying skeletal muscle damage.

Abstract Purpose Motivated by the goal of developing new methods to detect early signs of sarcopenia, we investigated if surface electromyographic (SEMG) data recorded during the performance of cyclic, submaximal back extensions are marked by age-specific differences in their time and frequency characteristics. Furthermore, day-to-day retest reliability of the EMG measures was examined. Methods A total of 86 healthy volunteers used a back dynamometer to perform a series of three maximal voluntary contractions (MVC) consisting of isometric back extensions, followed by an isometric back extension at 80% MVC, and finally 25 slow cyclic back extensions at 50% MVC. SEMG data was recorded bilaterally at L1, L2, and L5 from the iliocostalis lumborum, longissimus, and multifidus muscles, respectively. Tests were repeated two days and six weeks later. A linear mixed-effects model with fixed effects “age, sex, test number” and the random effect “person” was performed to investigate age-specific differences in both the initial value and the time-course (as defined by the slope of the regression line) of the root mean square (RMS-SEMG) values and instantaneous median frequency (IMDF-SEMG) values calculated separately for the shortening and lengthening phases of the exercise cycles. Generalizability Theory was used to examine reliability of the EMG measures. Results Back extensor strength was comparable in younger and older adults. The initial value of RMS-SEMG and IMDF-SEMG as well as the RMS-SEMG time-course did not significantly differ between the two age groups. Conversely, the IMDF-SEMG time-course showed more rapid changes in younger than in older individuals. Absolute and relative reliability of the SEMG time-frequency representations were comparable in older and younger individuals with good to excellent relative reliability but variable absolute reliability levels. Conclusions The IMDF-SEMG time-course derived from submaximal, cyclic back extension exercises performed at moderate effort showed significant differences in younger vs. older adults even though back extension strength was found to be comparable in the two age groups. We conclude that the SEMG method proposed in this study has great potential to be used as a biomarker to detect early signs of sarcopenic back muscle function.

Objective: The localized bicep tissue bioimpedance was measured from participants who completed an eccentric exercise protocol with one arm and no exercise with the other arm to compare changes that occur as a result of the exercise protocol over a 96h observation period. Methods: The localized bicep bioimpedance, bicep circumference, and self-reports of bicep pain were collected from 6 volunteers at pre, post, 24h, 48h, 72h, and 96h timepoints after completing an eccentric exercise protocol of the elbow flexor muscles. Results: The unexercised bicep showed no statistically significant differences between the pre-exercise and post-exercise measures at any timepoints for all impedance measures and circumference. The exercised bicep showed statistically significant decreases (p

N-terminal fragments of titin in urine have been proposed as a noninvasive marker of muscle damage, but there are no data on its time course after 96 h. The aims of this study were to investigate the time course of urinary titin N-terminal fragment (UTF) following eccentric exercise and the subsequent correlations between UTF and other muscle damage indices. Seventeen healthy young men performed 30 maximal isokinetic eccentric exercises at the elbow flexors. Muscle soreness (SOR), range of motion (ROM), maximal voluntary isometric contraction (MVIC), creatine kinase (CK), and UTF were sampled before, immediately after, and 24–144 h after exercise. The changes and correlations were analyzed with one-way ANOVA and Spearman’s rank correlation analysis. All the measured parameters showed significant differences from their pre-exercise values at 24 h or later after exercise (P < 0.05). UTF showed significant correlation with MVIC (r ≤ –0.485) at 24 h and later, with SOR (r ≥ 0.549) at 48 h and later, with ROM (r ≤ –0.485) at 48 h and later, and with CK (r ≥ 0.647) at all time points. UTF reached peak value at 96 h after the exercise and had not recovered completely at 144 h. Because UTF was highly correlated with the other muscle damage indices, especially CK, throughout the measurement period, it may be as useful an indicator of muscle damage as CK obtained from blood.

Eccentric and concentric actions produce distinct mechanical stimuli and result in different adaptations in skeletal muscle architecture. Cycling predominantly involves concentric activity of the gastrocnemius muscles, while playing basketball requires both concentric and eccentric actions to support running, jumping, and landing. The aim of this study was to examine differences in the architecture of gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) between elite basketballers and cyclists. A trained sonographer obtained three B-mode ultrasound images from GM and GL muscles in 44 athletes (25 basketballers and 19 cyclists; 24 ± 5 years of age). The images were digitized and average fascicle length (FL), pennation angle (θ), and muscle thickness were calculated from three images per muscle. The ratio of FL to tibial length (FL/TL) and muscle thickness to tibial length (MT/TL) was also calculated to account for the potential scaling effect of stature. In males, no significant differences were identified between the athletic groups in all parameters in the GM, but a significant difference existed in muscle thickness in the GL. In basketballers, GL was 2.5 mm thicker (95% CI: 0.7–4.3 mm, p = 0.011) on the left side and 2.6 mm thicker (95% CI: 0.6–5.7 mm, p = 0.012) on the right side; however, these differences were not significant when stature was accounted for (MT/TL). In females, significant differences existed in the GM for all parameters including FL/TL and MT/TL. Female cyclists had longer FL in both limbs (MD: 11.2 and 11.3 mm), narrower θ (MD: 2.1 and 1.8°), and thicker muscles (MD: 2.1 and 2.5 mm). For the GL, female cyclists had significantly longer FL (MD: 5.2 and 5.8 mm) and narrower θ (MD: 1.7 and 2.3°) in both limbs; no differences were observed in absolute muscle thickness or MT/TL ratio. Differences in gastrocnemius muscle architecture were observed between female cyclists and basketballers, but not between males. These findings suggest that participation in sport-specific training might influence gastrocnemius muscle architecture in elite female athletes; however, it remains unclear as to whether gastrocnemius architecture is systematically influenced by the different modes of muscle activation between these respective sports.

Introduction: Deficiency in the neural control of movement is associated with poor posture and skeletal muscle injuries. Exercise training is commonly reported as an intervention to improve neuromuscular activity. However, maximizing the effectiveness of exercise interventions for improving neural control of movement has been less investigated. The purpose of the current study was to examine improvement in neuromuscular activity (e.g., muscle fiber conduction velocity) and quadriceps function after eccentric resistance training versus concentric training. Materials and Methods: A total of 24 men participated in this study and were randomly divided into eccentric training (n=12) and concentric training groups (n=12). Maximal voluntary isometric contraction (MIVC) of quadriceps, vertical jumping, and multichannel surface electromyography (EMG) signals were recorded before and 12 weeks after resistance eccentric and concentric training. Muscle fiber conduction velocity (MFCV) and root mean square (RMS) were computed using raw EMG signals. Results: The percentage increases in MVIC and vertical jumping after eccentric resistance training were significantly higher than those after concentric training (P