Eccentric Exercise Research Articles

Biceps brachii elastography in well-trained men post eccentric exercise-induced muscle damage.

Recent advancements in elastography techniques, specifically supersonic shearwave elastography (SWE), have enabled non-invasive assessment of muscle stiffness. However, there is limited research on the immediate and short-term effects of eccentric exercise-induced muscle damage (EIMD) in well-trained individuals. This study aimed to follow up on the effects of eccentric training on the biceps brachialis stiffness by supersonic shearwave imaging (SSI) as well as the soreness and elbow flexion maximal voluntary isometric contraction (MVIC), immediately post-intervention, at 10min, 48h, and 96h in well-trained men. Thirteen well-trained males participated in the study. Baseline measurements of elastography images, MVIC of the elbow flexors, and muscle soreness were obtained. The participants performed an eccentric exercise protocol (4 sets X 10 repetitions) on the dynamometer isokinetic and elastography measurements were repeated immediately post-exercise, at 10min, 48h, and 96h. Significant reductions in stiffness (measured by shear modulus (µ)) were observed immediately and at 10min post-exercise. MVIC exhibited significant reductions immediately after, 10min, and 48h compared to baseline measurements. Muscle soreness peaked at 48h, persisting until 96h. The BB stiffness and MVIC reduction immediately post-eccentric exercise in well-trained men, suggest the potential involvement of mechanical stress and sarcomere rupture. Trained individuals may exhibit a distinct response to EIMD compared to untrained individuals, highlighting the applicability of elastography in monitoring acute biomechanical changes following high-intensity exercise.

Physiotherapeutic Intervention Techniques for Knee Osteoarthritis: A Systematic Review.

Globally, knee osteoarthritis (KOA) is the leading cause of disability. The most prevalent complaints associated with KOA are knee pain, joint stiffness, and weakness in the muscles of the lower limbs. These symptoms impede movement and result in functional limitations. As a result, people with KOA have a lower quality of life. For all patient groups with knee OA, an effective rehabilitation program focuses on improving knee range of motion, isometric quadriceps strength, and productivity level while reducing discomfort. The American College of Rheumatology (ACR) categorization criteria for KOA, research on KOA physiotherapy, and reviews covering various physical therapy interventions, including exercise, physical modalities, and patient education, were used to narrow down the pool of 180 systematic reviews to 15 articles. Google Scholar, PubMed, the Cochrane Library, and EMBASE were the databases that were used. The following keyword combinations were included in our search: KOA and physiotherapy or interventions or exercises, strengthening and stretching, concentric and eccentric training. Through our analysis, we identified a few methods that, in addition to standard therapy, could be used in clinical settings for people with osteoarthritis in the knee. It has been shown that Mulligan, Pilates, Kinesiotaping, Aquatic Therapy, and other current therapies are effective. The study employed a broad range of results. This review concludes that rather than relying solely on conventional therapy, it is preferable to combine a number of the most current physiotherapy techniques with it.

Age-related blunting of serial sarcomerogenesis and mechanical adaptations following 4 wk of maximal eccentric resistance training.

During aging, muscles undergo atrophy, which is partly accounted for by a loss of sarcomeres in series. Serial sarcomere number (SSN) is associated with aspects of muscle mechanical function including the force-length and force-velocity-power relationships; hence, the age-related loss of SSN contributes to declining performance. Training emphasizing eccentric contractions increases SSN in young healthy rodents; however, the ability for eccentric training to increase SSN in old age is unknown. Ten young (8 mo) and 11 old (32 mo) male Fisher344/BN rats completed 4 wk of unilateral eccentric plantar flexion training. Pre- and posttraining, the plantar flexors were assessed for the torque-frequency, passive torque-angle, and torque-velocity-power relationships. The soleus, lateral gastrocnemius (LG), and medial gastrocnemius (MG) were harvested for SSN assessment via laser diffraction, with the untrained leg used as a control. In the untrained leg/pretraining, old rats had lower SSN in the soleus, LG, and MG, lower maximum torque, power, and shortening velocity, and greater passive torque than young. Young showed increased soleus and MG SSN following training. In contrast, old had no change in soleus SSN and experienced SSN loss in the LG. Pre- to posttraining, young experienced an increase in maximum isometric torque, whereas old had reductions in maximum torque, shortening velocity, and power, and increased passive torque. Our results show that although young muscle has the ability to add sarcomeres in response to maximal eccentric training, this stimulus could be not only ineffective, but also detrimental to aged muscle leading to dysfunctional remodeling.NEW & NOTEWORTHY The loss of sarcomeres in series with age contributes to declining muscle performance. The present study investigated whether eccentric training could improve performance via serial sarcomere addition in old muscle, like in young muscle. Four weeks of maximal eccentric training induced serial sarcomere addition in the young rat plantar flexors and improved in vivo performance, however, led to dysfunctional remodeling accompanied by further impaired performance in old rats.

Proteomic Profiling of Muscular Adaptations to Short-Term Concentric Versus Eccentric Exercise Training in Humans

The molecular mechanisms underlying muscular adaptations to concentric (CON) and eccentric (ECC) exercise training have been extensively explored. However, most previous studies have focused on specifically selected proteins, thus, unable to provide a comprehensive protein profile and potentially missing the crucial mechanisms underlying muscular adaptation to exercise training. We herein aimed to investigate proteomic profiles of human skeletal muscle in response to short-term resistance training. Twenty young males were randomly and evenly assigned to two groups to complete a 4-week either ECC or CON training program. Measurements of body composition and physiological function of the quadriceps femoris were conducted both before and after the training. Muscle biopsies from the vastus lateralis of randomly selected participants (five in ECC and four in CON) of both before and after the training were analyzed using the liquid-chromatography tandem mass spectrometry in combination with bioinformatics analysis. Neither group presented a significant difference in body composition or leg muscle mass; however, muscle peak torque, total work, and maximal voluntary contraction were significantly increased after the training in both groups. Proteomics analysis revealed 122 differentially abundant proteins (DAPs; p value < 0.05 & fold change >1.5 or <0.67) in ECC, of which the increased DAPs were mainly related to skeletal muscle contraction and cytoskeleton and enriched specifically in the pentose phosphate pathway, extracellular matrix–receptor interaction, and PI3K−Akt signaling pathway, whereas the decreased DAPs were associated with the mitochondrial respiratory chain. One hundred one DAPs were identified in CON, of which the increased DAPs were primarily involved in translation/protein synthesis and the mitochondria respiratory, whereas the decreased DAPs were related to metabolic processes, cytoskeleton, and de-ubiquitination. In conclusion, the 4-week CON and ECC training resulted in distinctly different proteomic profiles, especially in proteins related to muscular structure and metabolism.

Cross-education Effects of Wrist Flexor Strengthening on Grip Strength: Comparison of Eccentric and Concentric Training

Introduction: Time away from training and competition from sport injuries may lead to detrimental effects on muscle strength and endurance. The cross-education effect plays an important role in preserving strength during recovery and rehabilitation; however, the effects have been found to be inconclusive. In addition, the distinct impacts of eccentric and concentric strengthening exercises need to be explored. The objective of this study was to compare the cross-education effects of eccentric and concentric wrist flexor strengthening exercises on hand grip strength among recreational athletes. Methods: A total of 39 recreational athletes aged between 18-25 years old were randomly assigned into two groups of wrist flexor strengthening exercise: eccentric (ECC) and concentric (CON) training groups. The training period for the study was 4 weeks with 3 sessions of strengthening exercises per week. Handgrip strength was measured bilaterally, before and after the intervention using the JAMAR handgrip dynamometer. Results: Significant increases in hand grip strength were observed for the ECC and CON groups in both the trained and untrained hands following 4 weeks of training. However, the handgrip strength between the two groups in the untrained hand was not significantly different (p=0.64). The strength gain in the untrained hand was 9.8% and 10.8%, for ECC and CON groups, respectively. Conclusion: The cross-education effect was significant in improving strength in the untrained hand. There was no difference in strength gains between concentric and eccentric strength training.

Eccentric exercise ≠ eccentric contraction.

Whether eccentric exercise involves active fascicle stretch is unclear due to muscle-tendon unit (MTU) series compliance. Therefore, this study investigated the impact of changing the activation timing and level (i.e., preactivation) of the contraction on muscle fascicle kinematics and kinetics of the human tibialis anterior during dynamometer-controlled maximal voluntary MTU-stretch-hold contractions. B-mode ultrasound and surface electromyography were used to assess muscle fascicle kinematics and muscle activity levels, respectively. Although joint kinematics were similar among MTU-stretch-hold contractions (∼40° rotation amplitude), increasing preactivation increased fascicle shortening and stretch amplitudes (9.9-23.2 mm, P ≤ 0.015). This led to increasing positive and negative fascicle work with increasing preactivation. Despite significantly different fascicle kinematics, similar peak fascicle forces during stretch occurred at similar fascicle lengths and joint angles regardless of preactivation. Similarly, residual force enhancement (rFE) following MTU stretch was not significantly affected (6.5-7.6%, P = 0.559) by preactivation, but rFE was strongly correlated with peak fascicle force during stretch (rrm = 0.62, P = 0.003). These findings highlight that apparent eccentric exercise causes shortening-stretch contractions at the fascicle level rather than isolated eccentric contractions. The constant rFE despite different fascicle kinematics and kinetics suggests that a passive element was engaged at a common muscle length among conditions (e.g., optimal fascicle length). Although it remains unclear whether different fascicle mechanics trigger different adaptations to eccentric exercise, this study emphasizes the need to consider MTU series compliance to better understand the mechanical drivers of adaptation to exercise.NEW & NOTEWORTHY Apparent eccentric exercises do not result in isolated eccentric contractions, but shortening-stretch contractions at the fascicle level. The amount of fascicle shortening and stretch depends on the preactivation during the exercise and cannot be estimated from the muscle-tendon unit (MTU) or joint kinematics. As different fascicle mechanics might trigger different adaptations to eccentric exercise, muscle-tendon unit series compliance and muscle preactivation need to be considered when eccentric exercise protocols are designed.

Submaximal, Low-Dose Eccentric vs Traditional Cycling Exercise: Reduced Oxygen Uptake and Pulmonary Artery Pressure Assessed by Echocardiography in Healthy Middle-aged Adults. A Randomized Controlled, Crossover Trial

ObjectiveTo investigate the ventilatory and circulatory differences between eccentric (ECC) and concentric (CON) cycling exercise at submaximal, low-dose intensity from onset to end-exercise in healthy middle-aged participants. DesignRandomized controlled crossover trial. SettingThe participants underwent 1 ECC and 1 CON test according to stepwise incremental exercise protocols at identical, submaximal intensities. Breath-by-breath analyses of ventilatory gas exchange and echocardiography were used to assess cardiopulmonary function during exercise. Participants24 healthy middle-aged, untrained participants (14 women, 10 men, 50±14 years) were included. Interventions1 ECC and 1 CON test at submaximal intensities. Main Outcome MeasureThe main outcome was oxygen uptake (V'O2). ResultsThe V'O2 increase was reduced by -422 mL/min (-52%, 95% confidence interval: -513 to -292, P<.001) during ECC, as well as the ventilatory drive. Echocardiographic parameters, heart rate (-14%), cardiac output (-21%), stroke volume (-15%), and pulmonary artery pressure by tricuspid regurgitation pressure gradient (TRPG) (-26%) were also significantly reduced during ECC compared with CON at identical intensities. Participants reported significantly less dyspnea and unchanged perceived leg fatigue in ECC. ConclusionECC was well tolerated, and significant reductions were observed in V'O2, ventilation, and right ventricular load compared with CON, even at low intensity levels. This study, conducted on healthy middle-aged participants, did not raise concerns that would hinder further investigation of the effects of ECC in patients with severely limited cardiopulmonary disease, and it calls for further research on this topic.

Pre-exercise hot water immersion increased circulatory heat shock proteins but did not alter muscle damage markers or endurance capacity after eccentric exercise

ABSTRACT Pre-exercise passive heating attenuates muscle damage caused by eccentric exercise in rats where the induction of heat shock proteins (HSPs) confers a myoprotective effect. We investigated whether pre-exercise hot water immersion (HWI) confers similar benefits in humans. Eleven recreational male athletes were immersed in 41°C water up to 60 min or until rectal temperatures reached 39.5°C. After a 6 h rest, the participants performed an eccentric downhill run for 1 h at −4% gradient to induce muscle damage. An endurance capacity test at 75% VO2max was conducted 18 h later. The control trial was similar except that participants were immersed at 34°C. Blood samples were collected to assess HSPs levels, creatine kinase, and lactate dehydrogenase activities. Plasma eHSP70 was higher post-immersion in HWI trials (1.3 ± 0.4 vs 1.1 ± 0.4; p = 0.005). Plasma eHSP27 was higher before (p = 0.049) and after (p = 0.015) endurance test in HWI. Leukocytic p-HSP27 was increased 18 h after HWI (0.97 ± 0.14 vs 0.67 ± 0.11; p = 0.04). Creatine kinase and lactate dehydrogenase activities were increased by 3-fold and 1.5-fold, respectively, after endurance test in HWI but did not differ across trials (p > 0.05). Mean heart rates were higher during eccentric run and endurance test in HWI as compared to control (p < 0.05). Endurance capacity was similar between trials (57.3 ± 11.5 min vs 55.0 ± 13.5 min; p = 0.564). Pre-exercise heating increased the expression of plasma eHSPs and leukocytic p-HSP27 but did not reduce muscle damage nor enhance endurance capacity.

A 6-week randomized-controlled field study: effect of isokinetic eccentric resistance training on strength, flexibility and muscle structure of the shoulder external rotators in male junior handball players.

Background: Team handball involves a tremendous amount of shoulder motion with high forces during repeated extended external range of motion. This causes shoulder complaints and overuse injuries. While eccentric training for the lower extremity shows preventive effects by improving strength, range of motion and fascicle length, there is a research gap for the shoulder joint and for advanced tissue characterization using diffusion tensor imaging. Objectives: To investigate the effects of 6-week eccentric isokinetic resistance training on strength, flexibility, and fiber architecture characteristics of the external rotators compared to an active control group in junior male handball players. Methods: 15 subjects were randomly assigned to the eccentric training group and 14 subjects to the active control group (conventional preventive training). Primary outcome measures were eccentric and concentric isokinetic strength of the external rotators, range of motion, and muscle fascicle length and fascicle volume. Results: The intervention group, showed significant changes in eccentric strength (+15%). The supraspinatus and infraspinatus muscles showed significant increases in fascicle length (+13% and +8%), and in fractional anisotropy (+9% and +6%), which were significantly different from the control group. Conclusion: Eccentric isokinetic training has a significant effect on the function and macroscopic structure of the shoulder external rotators in male junior handball players. While strength parameters and muscle structure improved, range of motion did not change. This research helps understanding the physiology of muscle and the role of eccentric training on shoulder function and muscle structure. Furthermore, DTI was found to be a promising tool for advanced tissue characterization, and the in vivo derived data can also serve as model input variables and as a possibility to extend existing ex-vivo muscle models. Future research is needed for functional and structural changes following convenient eccentric field exercises.

Cross-Education Effects of Isokinetic Eccentric Plantarflexor Training on Flexibility, Strength, and Muscle-Tendon Mechanics.

Large increases in joint range of motion (ROM) have been reported after eccentric resistance training; however, limited data exist describing the associated mechanisms or potential cross-education effects in the contralateral limb. Therefore, the effects of a 6-wk isokinetic eccentric plantarflexor training program were examined in 26 participants. Before and after the training program, dorsiflexion ROM, plantarflexor strength, and muscle-tendon unit (MTU) morphology and mechanics were measured in control ( n = 13) and experimental ( n = 13) young adult groups. Training consisted of 5 sets of 12 maximal isokinetic eccentric plantarflexor contractions twice weekly on the right limb. Significant ( P < 0.05) increases in dorsiflexion ROM (4.0-9.5°), stretch tolerance (40.3-95.9%), passive elastic energy storage (47.5-161.3%), and isometric (38.1-40.6%) and eccentric (46.7-67.0%) peak plantarflexor torques were detected in both trained and contralateral limbs in the experimental group. Significant increases in gastrocnemius medialis and soleus thickness (5.4-6.1%), gastrocnemius medialis fascicle length (7.6 ± 8.5%), passive plantarflexor MTU stiffness (30.1 ± 35.5%), and Achilles tendon stiffness (5.3 ± 4.9%) were observed in the trained limb only. Significant correlations were detected between the changes in trained and contralateral limbs for dorsiflexion ROM ( r = 0.59) and both isometric ( r = 0.79) and eccentric ( r = 0.73) peak torques. No significant changes in any metric were detected in the control group. Large ROM increases in the trained limb were associated with neurological, mechanical, and structural adaptations, with evidence of a cross-education effect in the contralateral limb being primarily driven by neurological adaptation (stretch tolerance). The large improvements in ROM, muscle size, and strength confirm that isokinetic eccentric training is a highly effective training tool, with potential for use in athletic and clinical populations where MTU function is impaired and current therapies are ineffective.

Impact of curcumin supplementation on exercise performance and muscle damage after a soccer match: a double-blind placebo-controlled cross-over study.

Curcumin ingestion can mitigate muscle damage, soreness, and inflammation following a laboratory-based eccentric exercise. Similar effects were observed in recent field-based studies wherein responses were evaluated after a soccer match. However, various potential confounding factors, such as matching opponent skill levels and daily training conditions, may have influenced the outcomes. In the present study, we investigated whether curcumin intake ameliorates changes in muscle damage markers following a soccer match while controlling for the potential confounding factors. Fifteen collegiate athletes were tested in a randomized, double-blind, cross-over manner. They were recruited from the same college soccer team and thus followed the same daily training regimen and competition levels. Furthermore, athletes positioning during matches were counterbalanced. They consumed either 180mg/day of curcumin or a placebo starting 1h before the match and continuing for 2days after a match (two 45-min plays and a 15-min half-time). Muscle soreness, jump performance (including countermovement jump and rebound jump index), and inflammatory and muscle damage markers (high-sensitive C-reactive protein, serum creatine kinase activity, and urinary N-terminal fragment of titin concentration) were evaluated before and after the match. The washout period between matches was set at 1week. After the match, all markers showed similarity between the placebo and curcumin conditions (all P > 0.208). These findings indicate that ingesting 180mg/day of curcumin may not expedite recovery from muscle damage elicited by soccer matches in collegiate soccer players.

The combined effectiveness of therapeutic ultrasound, electrical stimulations, and blood flow restriction to treat symptoms of muscle damage

ABSTRACT This study assessed whether symptoms of muscle damage could be reduced by a combination of therapeutic ultrasound and electrical stimulations, and whether this could be enhanced by blood flow restriction. Before and 48 h after performing eccentric elbow flexion exercises, individuals completed assessments of muscle damage. A 10-min therapeutic ultrasound and electrical stimulation treatment was then applied with and without blood flow restriction to assess short (5 min) and long-term (24 h) improvements. Twenty-three individuals completed the study (11 females). Data were analysed using Bayesian repeated measures ANOVAs. The damaging exercise increased discomfort (BF10 = 2.93e14) and relaxed joint angle (BF10 = 2425.90) while decreasing pain pressure threshold (BF10 = 289.71). Each of these variables was acutely improved with the combination treatment protocol (all BF10 ≥ 74) with no added effect of blood flow restriction. A combination of therapeutic ultrasound and interferential electrical stimulations appeared effective at acutely alleviating symptoms of muscle damage with no additive effect of blood flow restriction.

MRI T2 mapping and shear wave elastography for identifying main pain generator in delayed-onset muscle soreness: muscle or fascia?

IntroductionThe main generator of delayed onset muscle soreness (DOMS) is still unknown. This study aimed to clarify the main generator of DOMS.MethodsTwelve participants performed eccentric exercise (EE) on lower legs. MRI and ultrasound were used to assess changes of calf muscle and deep fascia before and after EE. These results were then compared to the muscle pain level.ResultsCompared to baseline, muscle pain peaked at 24–48 h after EE (downstairs 22.25 ± 6.196, 57.917 ± 9.298, F = 291.168, p < 0.01; resting 5.833 ± 1.899, 5.083 ± 2.429, F = 51.678, p < 0.01). Shear wave speed (SWE) of the deep fascia and T2 values of the gastrocnemius muscle and deep fascia all increased and peaked at 48 h after EE (1.960 ± 0.130, F = 22.293; 50.237 ± 2.963, F = 73.172; 66.328 ± 2.968, F = 231.719, respectively, p < 0.01). These measurements were positively correlated with DOMS (downstairs: r = 0.46, 0.76, 0.87, respectively, p < 0.001; resting: r = 0.42, 0.70, 0.77, respectively, p < 0.001). There was a significant positive correlation between SWE and T2 values of deep fascia (r = 0.54, p < 0.01).ConclusionDOMS is a common result of muscle and fascia injuries. Deep fascia edema and stiffness play a crucial role in DOMS, which can be effectively evaluated MR-T2 and SWE.Critical relevance statementDelayed-onset muscle soreness is a common result of muscle and deep fascia injuries, in which the edema and stiffness of the deep fascia play a crucial role. Both MRI and shear wave elastography can be effectively used to evaluate soft tissue injuries.Key points• The deep fascia is the major pain generator of delayed-onset muscle soreness.• There is a significant correlation between fascia injury and delayed-onset muscle soreness.• MRI and shear wave elastography are preferred methods for assessing fascia injuries.Graphical

Physical Activity Training Methods to Improve the Physical Condition of Volleyball Players: A Systematic Review

Study purpose. The study was aimed to identify exercise techniques used to improve the physical condition of volleyball players through literature studies. Materials and methods. A systematic review of these previous studies was conducted. We studied articles published between 2014 and 2023 that explained how to prepare volleyball players to have better physical condition. Scopus, Web of Science, Google Scholar, and PubMed were used for the electronic search. We collected all the articles that discussed how to improve physical performance through exercise. Results. To improve the physical condition of volleyball players, 50 publications used exercise techniques, which were categorized based on the physical condition that was evaluated and repaired. The following techniques are some of the ones that can be used: Neuromuscular, unilateral and bilateral, ballistic, plyometric exercises, combined weight and plyometric, mixed training with optimal load, COD &amp; plyometric complex, strength, combined strength, eccentric trainings, repetitive sprint, resistant/non-resistant sprint, resistance training, exercises with elastic band, core training, combined core training; small-sided games training, aerobic interval training, blood flow restriction, intermittent training, and anaerobic speed endurance. Conclusions. Following a thorough analysis, a number of training regimens were found to be effective in enhancing volleyball players’ physical attributes, including muscular strength, aerobic and anaerobic endurance, speed and acceleration, explosive power, flexibility, agility, and balance.

The effects of eccentric training on hamstring flexibility and strength in young dance students

The objective of this research is to examine the impact of eccentric training on hamstring flexibility and strength in young dancers during the concluding stages of their foundational dance training program. A total of 24 female, second-year dance students from Hebei Normal University were selected as participants. They were divided into three distinct groups: Nordic hamstring exercise and single-leg deadlift group (NHE&SLD), forward bending exercises and standing leg lift group (FBE&SLL), and a control group (CG). The study was designed around a 6-week training regimen. An isokinetic dynamometer was used to measure seated knee flexor–extensor strength, while electronic goniometry was employed to measure hamstring flexibility in the supine position. Paired sample t-tests were conducted within each group, and one-way analysis of covariance (ANCOVA) was utilized for comparisons between groups. In the NHE&SLD group, significant disparities were observed in both concentric (T = − 5.687, P = 0.001) and eccentric (T = − 3.626, P = 0.008) hamstring strength pre and post-intervention. The pre-intervention dominant leg concentric strength test values significantly influenced the post-intervention outcomes (F = 5.313, P = 0.001, η2 = 0.840). Similarly, the pre-intervention dominant leg eccentric strength test values impacted the post-intervention results (F = 4.689, P = 0.043, η2 = 0.190). Following the intervention, the NHE&SLD group displayed marked changes in the active straight leg raising angle on both left (T = − 4.171, P = 0.004) and right (T = − 6.328, P = 0.001) sides. The FBE&SLL group also revealed significant changes in the active straight leg raising angle on both left (T = − 4.506, P = 0.003) and right (T = − 4.633, P = 0.002) sides following the intervention. The pre-intervention left leg concentric strength test value significantly influenced the post-intervention outcomes (F = 25.067, P = 0.001, η2 = 0.556). Likewise, the pre-intervention right leg eccentric strength test value significantly influenced the post-intervention results (F = 85.338, P = 0.01, η2 = 0.810). Eccentric training can better enhance the flexibility and strength of hamstring muscles in dance students. Traditional stretching training significantly improves the flexibility of the hamstring muscles. Eccentric training has more training benefits than traditional stretching training. It is recommended for dance students to use eccentric training when increasing hamstring flexibility and strength.

Immediate crossover fatigue after unilateral submaximal eccentric contractions of the knee flexors involves peripheral alterations and increased global perceived fatigue.

After a unilateral muscle exercise, the performance of the non-exercised contralateral limb muscle can be also impaired. This crossover fatigue phenomenon is still debated in the literature and very few studies have investigated the influence of eccentric contractions. This study was designed to assess neuromuscular adaptations involved in the crossover fatigue of the non-exercised contralateral knee flexor muscles. Seventeen healthy young men performed a unilateral submaximal eccentric exercise of the right knee flexors until a 20% reduction in maximal voluntary isometric contraction torque was attained in the exercised limb. Before (PRE), immediately after exercise cessation (POST) and 24 hours later (POST24), neuromuscular function and perceived muscle soreness were measured in both the exercised limb and non-exercised limb. In addition, global perceived fatigue was assessed at each measurement time. At POST, significant reductions in maximal voluntary isometric contraction were observed in the exercised limb (-28.1%, p < 0.001) and in the non-exercised limb (-8.5%, p < 0.05), evidencing crossover fatigue. At POST, voluntary activation decreased in the exercised limb only (-6.0%, p < 0.001), while electrically evoked potentiated doublet torque was impaired in both the exercised limb and the non-exercised limb (-11.6%, p = 0.001). In addition, global perceived fatigue significantly increased at POST (p < 0.001). At POST24, all measured variables returned to PRE values, except for perceived muscle soreness scores exhibiting greater values than PRE (p < 0.05). A possible cumulative interaction between peripheral alterations and global perceived fatigue may account for the immediate crossover fatigue observed in the non-exercised limb.

Glutamine Accelerates Post-Exercise Recovery of Arms Power, Leg Power, and Smash Velocity at 48 Hours for Non-Elite Badminton Athletes

Badminton is a sport that is characterized by long-lasting muscle contractions in continuous smash movements which lead to fatigue and glutamine can potentially reduce the incidence of muscle fatigue. The aim of the study is to investigate glutamine affecting post-exercise recovery in non-elite badminton athletes. It was a randomized group pre-test and post-test design. Twenty male students were involved and divided into 2 groups: The placebo (Plac) group was only given instruction for jumping smash activities and mineral water, while the glutamine (Glut) group was jumping smash activities and mineral water containing glutamine. The jumping smash activities were carried out in 10 sets with 20 repetitions with a rest period of 30 seconds per set. Glutamine was given 3 times after 1 hour of jumping smash activities, 24 hours, and 48 hours with a dose of 0.4 grams/KgBW. There were significant differences in the vertical jump, leg power, arm power, and smash velocity in pre-post-2 between the Placebo and Glutamine groups with p&lt;0.05. Meanwhile, no difference was observed in the vertical jump, leg power, arm power, and smash velocity (p&gt;0.05) between the Placebo and Glutamine groups 72 hours after the jumping smash activities (post 3). The administration of glutamine at a dose of 0.4 gram/Kg BW given three times post-jumping smash (eccentric) exercise can accelerate the 48-hour post-exercise recovery of vertical jump, arm power, leg power, and smash velocity. Badminton athletes who play matches daily are expected to consume glutamine to speed up recovery. Keywords: Glutamine; physical exercise; badminton; non-elite athletes

Hypoxic, blood flow restriction, or eccentric cycling: Which training intervention is the most effective in elderly individuals?

Introduction&#x0D; The global rise in the elderly population is accompanied by an increased incidence of non-communicable diseases, including cancers, cardiovascular conditions, or sarcopenia. Therefore, it becomes crucial to find effective strategies to delay the onset or slow down the progression of these diseases. Hypoxic (HYP), blood flow restriction (BFR), and eccentric (ECC) training are promising modalities to mitigate the effects of aging. However, these training strategies have never been compared. Thus, this study aimed to evaluate whether moderate-intensity intermittent training (MIIT) combined with HYP, BFR, or ECC can induce similar or greater effects in strength and muscle mass in the elderly, compared to traditional cycling training (CON).&#x0D; Methods&#x0D; Fifty-five elderly participants completed a four-week MIIT protocol on cycle ergometers, divided into HYP, BFR, ECC, and CON groups. The HYP group trained under hypoxic conditions (inspired oxygen fraction ~14%), BFR group used occlusion cuffs applied proximally on thighs (~350 mmHg occlusion pressure), ECC group trained with an eccentric cycle-ergometer, and the CON group underwent standard cycling training. The first week consisted of 3 sets of 5 min exercise followed by 5 min rest and an additional set was added each week. All groups maintained a 60-rpm cadence, with intensity set at a 14-perceived exertion level on the 6-20 Borg scale.&#x0D; Strength parameters were assessed via isokinetic tests at angular velocities of 30°/s, 90°/s, and 180°/s, as well as isometric and endurance tests. Endurance strength was calculated as a percentage decrement score during 30 repetitions at 180°/s and the rate of force development was calculated on the isometric test.&#x0D; Muscle-bone cross-sectional area (CSA) was measured by integrating thigh circumference measured using a measuring tape, and anterior and posterior adipose tissue thickness assessed with a B-mode ultrasound.&#x0D; Results&#x0D; Post-training, all groups showed increased isometric quadriceps strength (14 ± 15%, p &lt; 0.001) and strength at all angular velocities: 18 ± 17% and 15 ± 21% (30°/s), 17 ± 20% and 20 ± 26% (90°/s), 10 ± 14% and 10 ± 16% (180°/s) for quadriceps and hamstrings respectively, all P &lt; 0.001. No significant group interaction effects were noted, except for hamstring strength at 30°/s (P = 0.038), with no improvements in the ECC group. No changes in the rate of force development or dynamic endurance post-training were noted. Thigh circumference increased (1 ± 2%, p = 0.008), without difference between training modalities.&#x0D; No significant variations in adipose tissue thickness or muscle-bone CSA occurred. The ECC group had higher training intensity (173.2 ± 7.5 W) than HYP (169.6 ± 9.8 W), BFR (169.9 ± 11.6 W), and CON (169.6 ± 8.4 W) groups (p &lt; 0.001). Training heart rate was lower in ECC (104.5 ± 6.6 bpm) compared to BFR (117.5 ± 10.5 bpm; p = 0.007) and CON (122.2 ± 12.3 bpm; p = 0.001), but similar to HYP (112.2 ± 9.4 bpm).&#x0D; Discussion/Conclusion&#x0D; MIIT, regardless of modality, effectively improves muscle strength in the elderly. Unexpectedly, no single training method was superior. Power output reduction has been proposed as an advantage of HYP and BFR modalities but was not observed in the present study. These results advocate for a personalized approach to training prescriptions, considering individual preferences and health conditions. Future research should explore longer training durations and impacts on other health outcomes such as cardiovascular and respiratory health.

The effects of eccentric arm crank training on upper body performance in elite athletes with a spinal cord injury

The effects of eccentric arm crank training on upper body performance in elite athletes with a spinal cord injury

Resistance Training Practices of Brazilian Olympic Sprint and Jump Coaches: Toward a Deeper Understanding of Their Choices and Insights (Part III).

In the final part of this three-article collection on the training strategies of Brazilian Olympic sprint and jump coaches, we provide a detailed description of the resistance training methods and exercises most commonly employed by these speed experts. Always with the objective of maximizing the sprint and jump capabilities of their athletes, these experienced coaches primarily utilize variable, eccentric, concentric, machine-based, isometric, complex, and isoinertial resistance training methods in their daily practices. Squats (in their different forms), Olympic weightlifting, ballistics, hip thrusts, lunges, calf raises, core exercises, leg curls, stiff-leg deadlifts, and leg extension are the most commonly prescribed exercises in their training programs, during both the preparatory and competitive periods. Therefore, the current manuscript comprehensively describes and examines these methods, with the additional aim of extrapolating their application to other sports, especially those where sprint speed is a key performance factor.