Eccentric Contractions Research Articles

Evaluation of A Muscle Damage Marker Titin N‐fragment in Human Skin Interstitial Fluid Using Intradermal Microdialysis

Unfamiliar exercises and/or muscle contractions during intense exercise, especially eccentric exercise, may cause muscle damage. Consequently, muscle protein creatine kinase (CK) and myoglobin (Mb) leaks into the bloodstream and titin N‐fragment is subsequently excreted through urine. Currently, blood (e.g., CK and Mb) and urine (e.g., titin N‐fragment) markers are generally used to monitor muscle damage in individuals who engage in intense training. However, these muscle damage markers in blood and urine have several limitations: 1) they cannot identify local damaged area, 2) several days are required to assess muscle damage thus immediate feedback is not possible, 3) assessment of blood markers requires invasive techniques, which may increase the risk of infection and/or can be painful to some individuals. Therefore, developing a new muscle damage marker without the above limitations is practically important.Interstitial fluid exists between cells. Previous studies reported that glucose concentrations of the interstitial fluid correlate well with those in the blood. Based on the information, minimally invasive wearable devices that can continuously predict blood glucose level by measuring skin interstitial glucose concentrations have been developed and now are available. However, it remains to be determined if muscle damage markers such as CK and titin N‐fragment can be detectable from skin interstitial fluid. Given that CK and titin N‐fragment leak into interstitial fluid before entering lymphatic vessels and blood, concentrations of CK and titin N‐fragment may appear earlier in the skin interstitial fluid relative to blood and/or urine. Furthermore, muscle damage marker concentrations in interstitial fluid appear to be specifically elevated in the muscle‐damaged area. However, these possibilities have never been assessed in human skin interstitial fluid.To assess these possibilities, muscle damage markers in blood, urine, and skin interstitial fluid were assessed in 12 healthy young adults (5 women, age: 26 ± 3 years; height: 168 ± 10 cm; body mass: 64 ± 10 kg) who performed 30 maximal isokinetic (60°/s) eccentric elbow flexor contractions using an isokinetic dynamometer (the non‐dominant arm). Intradermal microdialysis probes were implanted near the brachialis muscle in both the exercising and non‐exercising arms (i.e., 60‐70 % distal to the length between the acromial process and epicondylus lateralis humeri). Urinary and dialysate titin N fragment concentrations were assessed at baseline and 3 hours, 1, 4, and 7 days after the exercise. Serum and dialysate CK activity, serum and dialysate Mb concentrations, MVC torque, ROM, and muscle soreness were also assessed.After the eccentric exercise, titin N‐fragment in urine significantly increased at 4 and 7 days postexercise. Similarly, titin N‐fragment in dialysate significantly increased at 4 and 7 days postexercise. However, titin N‐fragment in dialysate did not increase in the non‐exercising arm at any postexercise periods. We conclude that the skin interstitial fluid can be used to assess a muscle damage marker, titin‐N fragment, and may reflect the site where muscle damage occurs.

Comparing the Electrical Activity of Selected Ankle Muscles in Athletes During Landing from Different Heights

Background and Aims Ankle injuries are one of the most common musculoskeletal injuries in atheletes. Proper landing after jumping leads to the preparation for the next skill as well as prevention of various ankle injuries. This study aims to compare the electrical activity of selected ankle muscles in athletes duirng landing from different heights. Methods This is a comparative study. Participants were 15 athletes (Mean age= 18.23 ± 2.3 years, mean height= 183.190 ± 6.3 cm, mean weight= 64.72 ±14.12 kg) with 3-5 years of experience in championship competitions. The landing skill was assessed from different heights (50%, 75%, 100% of maximum jump height). Electrical activity of selected ankle joint muscles (Gastrocnemius and Soleus) was recorded using an eight-channel BIOMED electromyography device with 96.34% validity and 91.29% reliability. Mean and standard deviation were used to describe the data, Shapiro-Wilk test was used to evaluate the normality of data distribution, and repeated measures analysis of variance was used to compare the collected data between groups followed by Bonferroni post hoc test. The significance level was set at 0.05. Results There was no significant difference in co-contraction of medial/lateral gastrocnemius and soleus muscles after jumping from three different heights. The peak contraction amplitude of the lateral gastrocnemius muscle was significantly different between the heights 50-75% (P= 0.006) and 50-100% (P= 0.002). The peak contraction amplitude of the medial gastrocnemius muscle was also significantly different between the heights 50-75% (P= 0.002) and 50-100% (P= 0.007). The peak contraction amplitude of soleus muscles was significantly different between the heights 75-100% (P=0.013) and 50-100% (P= 0.17). Conclusion There is an increase in the contractile activity of selected ankle muscles in the anterior-posterior plane caused by the increase in jump height and subsequent landing due to the optimal use of appropriate strategies to control the eccentric muscle contraction and the extensor torque of the ankle joint by increasing the electrical muscle activity during the ground contact, resulted in the prevention of injury to the ankle joint. Coaches and athletes can use these results to adopt training methods to strengthen these ankle muscles by considering the optimal implementation of landing skills with an injury prevention approach.

The Effect of Damaging Electric Muscle Contraction on Mitochondrial Health and Function

High intensity and prolonged exercise have been known to cause at least a temporary reduction in mitochondrial function. However, it is unclear how long mitochondrial function may remain impaired. Electrically stimulated eccentric muscle contractions (EEMC) may offer insights into the mechanisms by which mitochondrial function is restored following damaging muscle contractions like what is seen following high intensity exercise. The effects of EEMC on mitochondrial function have not been investigated. The aim of this study was to determine the impact that EEMC has on mitochondrial function one week following a single bout of the electrical stimulation. Muscle biopsies were taken from the vastus lateralis of female subjects one week prior and one week after EEMC. Muscle fibers were then prepared for High Resolution Respirometry and Fluorometry analysis on an Oroboros O2K Fluo‐Respirometer. This approach allowed for real‐time evaluation of mitochondrial function and production of reactive oxygen species (ROS). We measured mitochondrial function using two different substrate‐uncoupler‐inhibitor‐titrations (SUITs) designed to evaluate carbohydrate‐supported respiration (SUIT‐1) and fatty‐acid supported respiration (SUIT‐2). Under SUIT‐1 conditions, maximum coupled respiration (OXPHOS) was not significantly different between the pre and post EEMC biopsies. Under SUIT‐2 fatty‐acid supported and phosphorylating conditions (with ADP), there was a significant increase in respiratory function in the post EEMC biopsy (p=0.045). Mitochondrial ROS production was not significantly different following recovery than the baseline measures under SUIT‐1 conditions. These data represent the first evaluation of mitochondrial function one week following EEMC. We also show that the previously demonstrated negative effect of high‐intensity exercise on mitochondrial function may be fully recovered one week after damaging contractions and that fatty‐acid supported respiration is improved at the same time point.

Fracture-Separation of the Medial Humeral Epicondyle Caused by Arm Wrestling: A Systematic Review.

Background:Arm wrestling is a popular sport in which various injuries have occurred, even in children.Purpose:To analyze reported fracture-separation of the medial humeral epicondyle (MHE) caused by arm wrestling to determine its mechanism and provide a current overview.Study Design:Systematic review; Level of evidence, 4.Methods:The PubMed and Web of Science databases were searched using the terms “arm wrestling” and “humeral fracture” or “medial humeral epicondyle fracture”; and “sports” and “humeral fracture” or “medial humeral epicondyle fracture,” following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The inclusion criteria were English full-text articles on arm wrestling–induced MHE fracture that described patient characteristics and presented appropriate images. Studies with a lack of appropriate images or detailed description of the injury situation were excluded. The patient characteristics were evaluated, and the ratios of treatment selection and outcomes were evaluated using the chi-square test.Results:Included were 27 studies with a total of 68 patients, all boys with a mean age of 14.6 ± 1.24 years (based on n = 65, with 3 patients excluded from this calculation as no definitive age was provided). Boys aged 14 to 15 years accounted for 72% (49/68) of the cases. Fracture occurred suddenly during arm wrestling in 63 boys, while the other 5 boys experienced antecedent medial elbow pain. The match status at the time of injury, provided for 46 patients, was varied. In 31 boys with known match details, injury occurred when a participant suddenly added more force to change the match status. Eight patients displayed anterior and/or proximal displacement of the MHE fragment. Treatment was nonoperative in 25 patients and operative in 38 patients (n = 63, excluding 5 unknown patients). In 35 patients followed up for ≥3 months (mean, 17.6 ± 12.3 months), outcomes were not significantly different between the operative and nonoperative groups.Conclusion:MHE fracture-separation caused by arm wrestling occurred mostly in boys aged 14 to 15 years regardless of the match status. The likely direct cause is forceful traction of the attached flexor-pronator muscles. A relative mechanical imbalance during adolescence may be an underlying cause. A sudden change from concentric to eccentric contraction of the flexor-pronator muscles increases the likelihood of fracture occurrence.

Sex-Based Differences in the Myogenic Response and Inflammatory Gene Expression Following Eccentric Contractions in Humans.

After muscle injury, the interaction between muscle satellite cells (SC) and the immune response is instrumental for the repair and regeneration of skeletal muscle tissue. Studies have reported sex-based differences in the skeletal muscle inflammatory and regenerative response following injury. However, many of these studies investigated such differences by manipulating the concentration of estradiol, in rodents and humans, without directly comparing males to females. We sought to explore differences in the myogenic and inflammatory response following unaccustomed eccentric exercise in males and females. We hypothesized that females would have a blunted myogenic and inflammatory response as compared to males. Methods: 26 (13 male, 13 female) healthy young adults (22 ± 0.4 years [mean ± SEM]) performed 300 maximal eccentric contractions (180°/s) of the knee extensors. Muscle biopsies were taken before (pre) and 48 h (post) following eccentric damage. SC content and activation were determined by immunohistochemical and real time-polymerase chain reaction (rt-PCR) analysis. Inflammatory markers were analyzed using rt-PCR. Results: Following eccentric damage, males had a greater expansion of type I-associated SC (p < 0.05), and there was a trend for a greater expansion in total SC (type I + II fibers) (p = 0.06) compared to females. There was a trend for a greater increase in Pax7 and CCL2 gene expression in males compared to females (p = 0.09). Conclusion: We conclude that there are sex-based differences in the myogenic and inflammatory response, where females have a blunted SC and inflammatory response.

Muscle Shear Elastic Modulus Provides an Indication of the Protection Conferred by the Repeated Bout Effect.

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.

Mechanisms of weakness in Mdx muscle following in vivo eccentric contractions.

Skeletal muscle of the dystrophin-deficient mdx mouse is hypersensitive to eccentric (ECC) contraction-induced strength loss due to plasmalemmal electrical dysfunction. Despite plasmalemmal inexcitability being a logical mechanism responsible for weakness, it remains unclear if processes up- and/or down-stream remain functionally intact in injured mdx muscle. The purpose of this study was to analyze additional processes necessary for excitation-contraction coupling that are potentially disrupted by ECC contractions. Anterior crural muscles (tibialis anterior, extensor digitorum longus [EDL], and extensor hallucis muscles) of wildtype (WT) and mdx mice were injured in vivo with 50 ECC contractions and torque was measured immediately before and after the contraction bout. Following the in vivo assessment, EDL ex vivo isometric and caffeine forces were analyzed. In vivo isometric torque and ex vivo force in WT muscle were reduced 38 and 30% (p < 0.001), while caffeine force was also reduced (p = 0.021), albeit to a lesser degree (9%). In contrast, in vivo isometric torque, ex vivo isometric force and ex vivo caffeine-induced force were all reduced 56-67% (p < 0.001) in mdx muscle and did not differ from one another (p = 0.114). Disproportional reductions in isometric strength and caffeine-induced force confirm that ECC contractions uncoupled the plasmalemma from the ryanodine receptors (RyRs) in WT muscle. In mdx muscle, the proportional reductions in isometric strength and caffeine-induced force following ECC contractions reveal that dysfunction occurs at and/or distal to the RyRs immediately post-injury. Thus, weakness in injured mdx muscle cannot be isolated to one mechanism, rather several steps of muscle contraction are disrupted.

Comparison of hip abductor and adductor muscle performance between healthy and osteitis pubis professional footballers.

The study aimed to compare the concentric and eccentric muscle performance of the hip abductor and adductor muscles at a high angular velocity in football players with osteitis pubis and healthy players. A total number of 32 male football players with osteitis pubis and 20 healthy footballers were tested using an isokinetic dynamometer at a speed of 180°/s. Hip abductor and adductor peak torque/body weight, time to peak torque, acceleration, and deceleration times produced during concentric and eccentric muscle contraction modes were measured using a Biodex dynamometer. Football players with osteitis pubis demonstrated a significantly higher time to peak torque, acceleration, and deceleration times (p < 0.05); however, when compared to healthy athletes, there was no significant change in muscle strength. The present study showed that football players with osteitis pubis had a reduction in neuromuscular reaction. Therefore, the reaction time of these muscles is critical, and the reduction could result in magnified stresses and/or poorly distributed loads across the musculotendinous structure of the anterior pelvis, which presumably could lead to the development of osteitis pubis. Incorporate findings of the current study in clinical practice could afford critical information when evaluating the hip muscles in football players with osteitis pubis, for pre-screening, enhancing the rehabilitation programs, and guiding the decision of returning to sports after injury.

A Comparative Study of Sports-specific Balance Training versus Plyometric Balance Training

Introduction: Football is a sport that involves running as the foremost part in which the lower limb plays a vital role in participation. Balance training is vital to athletic performance and should be integrated into an athlete’s daily training. Plyometric represents the performance of stretch-shortening cycle (SSC) activities that involve a high-intensity eccentric contraction straightaway after a rapid and powerful concentric contraction.Method: It is an experimental study with 30 college male football players in the age group of 18-25 years. Based on inclusion and exclusion criteria, they were divided into 2 groups. Group A consisted of 15 individuals who were trained with sports-specific balance training programmes. Group B consisted of 15 individuals who were trained with plyometric balance training. The individuals were trained for 4 weeks with 3 sessions per week (12 sessions). The pre-test and post-test measurements were measured using the triple hop test, stork balance test, and modified star excursion balance test (MSEBT).Results: Pre-test and post-test results of both groups were compared. The results showed a highly significant difference in mean values at p ≤ 0.001.Conclusion: 4 weeks of sports-specific balance training and plyometric balance training showed significant improvement in lower limb muscle strength in collegiate football players.

How to Improve the Reactive Strength Index among Male Athletes? A Systematic Review with Meta-Analysis.

The reactive strength index (RSI) describes the individual’s capability to quickly change from an eccentric muscular contraction to a concentric one and can be used to monitor, assess, and reduce the risk of athlete’s injury. The purpose of this review is to compare the effectiveness of different training programs on RSI. Electronic searches were conducted in MEDLINE, PubMed, Scopus, SPORTDiscus, and Web of Science from database inception to 11 February 2022. This meta-analysis was conducted in accordance with the recommendations of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). The search returned 5890 records, in which 39 studies were included in the systematic review and 30 studies were included in the meta-analysis. Results from the randomized studies with the control group revealed that plyometric training improved RSI in adult athletes (0.84, 95% CI 0.37 to 1.32) and youth athletes (0.30, 95% CI 0.13 to 0.47). Evidence withdrawn from randomized studies without a control group revealed that resistance training also improved the RSI (0.44, 95% CI 0.08 to 0.79) in youth athletes but not in adults. Interventions with plyometric training routines have a relatively large, statistically significant overall effect in both adult and youth athletes. This supports the implementation of this type of interventions in early ages to better cope with the physical demands of the various sports. The impact of resistance training is very low in adult athletes, as these should seek to have a more power-type training to see improvements on the RSI. More interventions with sprint and combined training are needed.

Strength Level of Professional Elite Soccer Players after the COVID-19 Lockdown Period: A Retrospective Double-Arm Cohort Study.

Background It is well known that periods of inactivity generate a loss of muscle strength, a fundamental component of sports performance in soccer. However, little information is available on the decrease in strength levels in professional soccer players after the quarantine lockdown that occurred during the COVID-19 pandemic. Aim To compare the isokinetic peak torque profiles of professional soccer players from different teams before and after the quarantine period generated by COVID-19. Methods A retrospective observational study was performed using data collected from two different professional elite-level soccer teams just before and immediately after the COVID-19 quarantine period. One team gave individual instructions to its players for conditioning maintenance at home during the quarantine period, while the other team used regular video calls to maintain the player's conditioning status on home training. The main outcomes were the mean peak torque of knee extensors and flexors, from concentric and eccentric contractions of each playing position. Analysis. A two-way ANOVA analysis was used to compare peak torque before and after the quarantine period and between both teams' strategies, showing a statistically significant reduction in eccentric knee flexor peak torque from the team that did not have remote monitoring. Conclusions Remote monitoring programs are recommended so that athletes are less affected by the deleterious effects of confinement.

Effects of Bilateral and Unilateral Eccentric Exercise on Muscle Damage and Muscular Physiological Indices in Healthy Men

PURPOSE: This study aimed to determine the effects of bilateral and unilateral eccentric exercises on muscle damage and muscular physiological indices in healthy men.METHODS: Using a randomized crossover design, nine adult males without musculoskeletal disorders were divided into a bilateral eccentric exercise group (BEG, n=9) and a unilateral eccentric exercise group (UEG, n=9). Bilateral and unilateral eccentric exercises involved five sets of six repetitions of the rhythm metronome speed eccentric contraction 3 seconds at 110% one repetition maximum (1RM) using bilateral of BEG and the dominant and non-dominant of UEG separated by four weeks, respectively. Muscle damage (flexed and extended ROM, CIR, and VAS) and muscular physiological indices (muscle activity, muscle fatigue, and muscle tone) were measured before, immediately after (0 hour), 24, 48, 72, and 96 hours following bilateral and unilateral eccentric exercises.RESULTS: The flexed ROM, CIR, VAS, muscle activity, and muscle tone were significantly increased after both bilateral and unilateral eccentric exercises (p&lt;.05, respectively). Extended ROM and muscle activity significantly decreased after both bilateral and unilateral eccentric exercises (p&lt;.05, respectively). However, there was no significant interaction between side (S) and time and side (T×S).CONCLUSIONS: These results showed that there was no difference in muscle damage and physiological indices after measuring and setting the 1RM muscle strength separated by bilateral and unilateral eccentric exercises.

Association between Concentric and Eccentric Isokinetic Torque and Unilateral Countermovement Jump Variables in Professional Soccer Players.

Isokinetic tests have been highly valuable to athletic analysis, but their cost and technical operation turn them inaccessible. The purpose of this study was to verify the correlation between unilateral countermovement jump variables and isokinetic data. Thirty-two male professional soccer players were subjected to the isokinetic testing of both knee extensors and flexors in concentric and eccentric muscle contractions. They also executed unilateral countermovement vertical jumps (UCMJ) to compare maximum height, ground reaction force, and impulse power with isokinetic peak torque. Data analysis was conducted through Pearson correlation and linear regression. A high correlation was found between dominant unilateral extensor concentric peak torque and the UCMJ maximum height of the dominant leg. The non-dominant leg jump showed a moderate correlation. No other variable showed statistical significance. Linear regression allowed the generation of two formulae to estimate the peak torque from UCMJ for dominant and non-dominant legs. Although few studies were found to compare our results, leading to more studies being needed, a better understanding of the unilateral countermovement jump may be used in the future as a substitute to the expensive and technically demanding isokinetic testing when it is unavailable, allowing the assessment of lower limb physical asymmetries in athletic or rehabilitation environments.

The role of protein aggregation in the pathogenesis of inclusion body myositis.

Inclusion body myositis (IBM) is characterised by infiltration of CD8+ T-cells and signs of protein aggregation such as rimmed vacuoles and inclusion bodies. Aggregated proteins include those present in neurodegenerative diseases, and also those involved in protein homeostasis. The aim of this review is to discuss the pathological effects of protein aggregates and the process of aggregation following immune attack in IBM. Immune attack is likely to cause protein aggregation by impairing endoplasmic reticulum (ER) and mitochondrial function. Apoptotic and necrotic pathways are activated, possibly leading to nucleo-cytoplasmic coagulation. Overexpression of nuclear and ribosomal proteins in rimmed vacuoles suggests that the vacuoles develop from the collapse of myonuclei and the surrounding ER. Aggregated proteins can activate the NLR family pyrin domain containing 3 (NLRP3) inflammasome or provoke a humoral immune response. Heat shock proteins, ribosomal proteins and protein fragments may provoke interferon-gamma and cytotoxic T-cell responses in a similar manner to Mycobacterium tuberculosis antigens. Persistent provocation can lead to T-cell large granular lymphocytic leukaemia which is resistant to immunosuppression, and would explain the progression from polymyositis to IBM. Protein aggregates may impair the cellular machinery, and proteins may propagate along a myocyte in a prion-like manner. These pathological mechanisms may prevent myocyte regeneration following damage from eccentric muscle contraction, causing weakness and atrophy in a characteristic pattern. Further understanding of the mechanisms of protein aggregation in IBM may lead to additional therapies as well as novel muscle and blood biomarkers. Earlier diagnosis and treatment may result in improved outcomes when effective therapies are available.

Mitochondria-targeted antioxidant supplementation does not affect muscle soreness or recovery of maximal voluntary isometric contraction force following muscle-damaging exercise in untrained men: a randomized clinical trial.

Unaccustomed exercise causes muscle damage resulting in loss of muscle function, which may be attributable to exercise-induced increases in skeletal muscle reactive oxygen species. This study examined the effect of mitochondria-targeted antioxidant supplementation on recovery of muscle function following exercise. Thirty-two untrained men received MitoQ (20mg/day) or a placebo for 14 days before performing 300 maximal eccentric contractions of the knee extensor muscles of 1 leg. Muscle function was assessed using isokinetic dynamometry before, immediately after, and 24, 48, 72, and 168 hours after exercise. Muscle soreness was assessed using a visual analogue scale 24, 48, 72, and 168 hours after exercise. Blood samples were collected before, immediately after, and 2, 24, 48, 72, and 168 hours after exercise and urine samples were collected before and during the 48 hours after exercise. The reduction in maximal voluntary isometric contraction force and peak concentric torque following exercise was unaffected by MitoQ while recovery of peak eccentric torque was delayed in the MitoQ group. Exercise-induced increases in urine F2-isoprostanes were unaffected by MitoQ. MitoQ augmented exercise-induced increases in plasma creatine kinase levels, while plasma IL-6 was similar between groups. Muscle soreness was not affected by MitoQ. These results indicate that MitoQ does not attenuate post-exercise muscle soreness and may delay recovery of muscle function following eccentric exercise. Trial registration number: ACTRN12620001089921. Novelty: Post-exercise recovery of maximal voluntary isometric contraction force and peak concentric torque were unaffected by MitoQ. MitoQ delayed post-exercise recovery of peak eccentric torque. Post-exercise muscle soreness was unaffected by MitoQ.

Effects of Eccentric vs. Concentric Sports on Blood Muscular Damage Markers in Male Professional Players.

Simple SummaryMuscle eccentric contractions produce a higher degree of damage compared to concentric contractions. However, during sport practice (training and competition), eccentric as well as concentric actions appear at different levels. The presence of muscle-specific proteins in circulation is indicative of damage. The present report compares three sport disciplines: cycling, mainly concentric, volleyball, mainly eccentric in the legs and concentric in the arms, and basketball, mainly eccentric. The aim was to analyze the pattern of muscular injury blood markers in professional players in two moments of the season: after a training period and after a competition period. Results show that after a training period, muscle damage blood markers are higher in basketball and volleyball players, as expected due to their dominant eccentric component. However, during competition, these markers are higher in cyclists as a result of frequent eccentric actions. Therefore, the component eccentric–concentric is not defined exclusively by the sport discipline. The moment of the season (training vs. competition) has to be considered as well. This information could help sport professional to planify more specific training programs, preparations for competition, as well as post-exercise recovery.Background: Repetitive eccentric contractions can lead to higher degree of damage compared to repetitive concentric contractions. However, this type of exercise does not reproduce the real situations during the season in competitive sport disciplines. Methods: We analyzed the pattern of muscle damage blood markers in male professionals from three disciplines: cycling (n = 18), mainly concentric, vs. basketball (n = 12) and volleyball (n = 14), both mainly eccentric. Circulating muscle markers were analyzed in two moments of the regular season: after a 20-day training (no competition) period (T1) and after a 20-day period of high demanding competition (T2). Results: Blood levels of creatine kinase and myoglobin (muscle markers) increased in all groups at T2 compared to T1 as a result of competition intensity. The lower increases were noticed in cyclists at the end of both periods. Testosterone levels decreased at T2 compared to T1 in all disciplines, with lower levels found in cyclists. However, cortisol plasma levels decreased in basketball and volleyball players at T2, but increased significantly in cyclists, suggesting a limited adaptation to the effort. Conclusions: The pattern of circulating muscle markers is different depending of the demanding efforts (training vs. competition) of each particular discipline.

Effect of daily 3-s maximum voluntary isometric, concentric, or eccentric contraction on elbow flexor strength.

The present study compared a 3-s isometric maximal voluntary contraction (MVC), concentric MVC and eccentric MVC of the elbow flexors performed daily for 5days a week for 4weeks for changes in muscle strength and thickness. Young sedentary individuals were assigned to one of three training groups (n=13 per group) that performed either 3-s isometric, concentric, or eccentric MVC once a day for 20days, or to a control group (n=10) that had measurements without training. The participants in the isometric group performed isometric MVC at 55° (0.96rad) elbow flexion, and those in the concentric or eccentric group performed concentric MVC or eccentric MVC between 10° (0.17rad) and 100° (1.75rad) elbow flexion at 30°/s (0.52rad/s) on an isokinetic dynamometer. MVC isometric torque at 20° (0.35rad), 55° (0.96rad), and 90° (1.57rad) elbow flexion, MVC concentric and eccentric torque at 30°/s (0.52rad/s) and 180°/s (3.14rad/s), and muscle thickness (MT) of biceps brachii and brachialis were measured before and several days after the 20th exercise session. The control group did not show any changes. The eccentric group showed increases (p<0.01) in isometric (three angle average: 10.2±6.4%), concentric (two velocity average: 12.8±9.6%), and eccentric MVC torque (12.2±7.8%). An increase (p<0.05) was limited for isometric MVC torque (6.3±6.0%) in the concentric group, and for eccentric MVC torque (7.2±4.4%) in the isometric group. No significant changes in MT were evident for all groups. Performing one 3-s MVC a day increased muscle strength, but eccentric MVC produced more potent effects than isometric or concentric MVC.

Comparison between side-lying and standing positions for hip abductor strength assessment

BackgroundThe hip abductor muscles control the pelvis in the frontal plane and allow the maintenance of trunk position and dynamic balance during weight-bearing activities. ObjectiveTo compare the side-lying and standing positions for hip abductor strength assessment with regards to torque production and myolectric activity. MethodConcentric and eccentric hip abductor peak torque and total work, and myoelectric activity of the tensor fascia lata, gluteus medius, and inferior and superior portions of the gluteus maximus muscles were measured during maximal isokinetic tests for hip abductor strength in the side-lying and standing positions. The Wilcoxon test was used to compare variables between the positions. ResultsPeak torque values did not differ between side-lying and standing positions for both concentric and eccentric contraction modes (p > .05). During standing position, greater concentric total work was observed (p = .013). This position resulted in a lower activity of the tensor fascia lata muscle (p = .005) compared to side lying position. Myoelectric activity of gluteus medius, and inferior and superior portions of the gluteus maximus was similar between positions (p > .05). ConclusionBoth positions presented similar peak torque values and, during the standing position, a greater concentric total work and lesser activation of the tensor fascia lata was observed. Standing position can be used when emphasis on the superior portion of gluteus maximus over the tensor fascia lata is intended.

Immediate voluntary activation deficits following submaximal eccentric contractions of knee extensors are associated with alterations of the sense of movement

The mechanisms underlying movement sense alterations following repeated eccentric contractions remain unclear. This study concomitantly investigated the effects of unilateral eccentric contractions on movement sense and on neuromuscular function at the knee before, immediately after (POST), 24 (POST24) and 48 (POST48) h after the exercise. Twelve participants performed sets of submaximal knee extensors (KE) eccentric contractions until a 20% decrease in maximal voluntary isometric contraction (MVIC) torque was reached. Threshold to detect passive movement (TTDPM) tasks were used to assess movement sense during both knee flexion (TTDPMFLEX) and extension (TTDPMEXT). KE fatigability was assessed using the interpolated twitch technique. TTDPM values expressed in seconds and the percentage of unsuccessful trials only increased at POST during TTDPMFLEX and TTDPMEXT. The 20%-MVIC decrease was associated with significant decreases in voluntary activation level (− 12.7%, p < 0.01) and potentiated doublet torque at 100 Hz (− 18.1%, p < 0.001). At POST24, despite persistent reductions of maximal voluntary and electrically evoked torques associated with increased perceived muscle soreness, TTDPM values and the percentage of unsuccessful trials returned to baseline values. Consequently, movement sense alterations were only observed in the presence of voluntary activation deficits, suggesting that some exercise-induced central alterations may affect the somatosensory function.

Midterm outcome and strength assessment after quadriceps tendon refixation with suture anchors

PurposeQuadriceps tendon ruptures (QTR) occur predominantly in middle-aged patients through violent eccentric contraction that occurs either when trying to regain balance or during a fall on the hyperflexed knee. The aim of this study was to quantify midterm postoperative results, including strength potential measured via standardized strength tests following acute (< six weeks) quadriceps tendon refixation using suture anchors.MethodsAll consecutive patients with QTR who underwent surgical suture anchor refixation between 2012 and 2019 at a single institution with a minimum follow-up of 12 months were retrospectively evaluated. Outcome measures included Tegner Activity Scale (TAS), Lysholm score, International Knee Documentation Committee subjective knee form (IKDC), Knee injury and Osteoarthritis Outcome Score (KOOS) subscales, return to work rates, and Visual Analog Scale (VAS) for pain. Additionally, a standardized clinical examination and an isometric strength assessment of knee extension and flexion were performed.ResultsA total of 17 patients (median age 61.0 [25–75% IQR 50.5–72.5]) were available for final assessment at a mean follow-up of 47.1 ± SD 25.4 months. The majority of patients were male (82.4%) and most injuries occurred due to a fall on the hyperflexed knee (76.5%). The average time interval between trauma and surgery was 12.7 ± 7.5 days. Patients achieved a moderate level of activity postoperatively with a median TAS of 4 (3–5.5) and reported good to excellent outcome scores (Lysholm score: 97 (86.5–100); IKDC: 80.7 ± 13.5; KOOS subscales: pain 97.2 (93.1–100), symptoms 92.9 (82.5–100), activities of daily living 97.1 (93.4–100), sport and recreation function 80 (40–97.5) and knee-related quality of life 87.5 (62.5–100). All patients were able to fully return to work and reported little pain [VAS: 0 (0–0)]. No postoperative complications were reported. Strength measurements revealed a significant deficit of knee extension strength in comparison to the contralateral side (p = 0.011).ConclusionSuture anchor refixation of acute QTR leads to good functional results and high patient satisfaction without major complications. Isometric knee extension strength, however, may not be fully restored compared to the unaffected side.