Activation of skeletal muscle mechanoreceptors and nociceptors reduces the exercise performance of the contralateral homologous muscles.

INTRODUCTION: Increasing evidence suggests that activation of muscle nerve afferents may inhibit central motor drive, affecting contractile performance of remote exercising muscles. While these effects are well documented for metaboreceptors, very little is known about the activation of mechano- and mechano-nociceptive afferents on performance fatigability. Therefore, the purpose of the present study was to examine the influence of mechanoreceptors and nociceptors on performance fatigability. METHODS: Eight healthy young males undertook four randomized experimental sessions on separate occasions in which the experimental knee extensors were: a) resting (CTRL), b) passively stretched (ST), c) resting with DOMS (DOMS), or d) passively stretched with DOMS (DOMS+ST), while the contralateral leg performed an isometric time to task failure (TTF). Changes in maximal voluntary contraction (ΔMVC), potentiated twitch force (ΔQtw,pot) and voluntary muscle activation (ΔVA) were also assessed. RESULTS: TTF was reduced in DOMS+ST (-43%) and ST (­29%) compared with CTRL. DOMS+ST also showed a greater reduction of VA (-25% vs ­8%, respectively) and MVCcompared with CTRL (­28% vs -45%, respectively). RPE was significantly increased at the initial stages (20-40-60%) of the TTF in DOMS+ST compared with all conditions. CONCLUSION: These findings indicate that activation of mechanosensitive and mechano-nociceptive afferents of a muscle with DOMS reduces TTF of the contralateral homologous exercising limb, in part by reducing VA so accelerating mechanisms of central fatigue.

Changes in Physical Fitness, Muscle Damage and Cognitive Function in Elite Rugby Players over a Season.

This study proposes to monitor the physical, immune and cognitive responses and adaptations of elite rugby players throughout the season based on the loads performed. Anthropometric measurements, physical fitness tests (e.g., muscle strength and power, linear and change-of-direction speed, cardiorespiratory fitness) and analyses of serum concentrations of markers of muscle damage (creatine kinase [CK] and lactate dehydrogenase [LDH]) and brain-derived neurotrophic factor (BDNF) were carried out over a sporting season (24 weeks) for 17 elite rugby players (10 forwards and 7 backs) aged 18.91 ± 0.76 years. The physical fitness test results show improvements in the performance of both forwards and backs over the season (p < 0.05), with an advantage for backs compared with forwards in most tests (p < 0.05). Muscle damage markers decreased at the end of the season compared with the baseline levels for forwards (p < 0.05). CK levels were unchanged for the backs, but there were increased LDH concentrations at the end of the season compared with baseline (p < 0.05). Serum BDNF levels decreased for the total group between the second and third sampling (p < 0.05). The muscular and physical capacities of rugby players differ according to their playing position. Immune responses and adaptations, as well as BDNF levels, vary throughout the season and depend on the physical load performed.

Eccentric exercise-induced delayed onset trunk muscle soreness alters high-density surface EMG-torque relationships and lumbar kinematics.

We aimed to assess high-density surface electromyography (HDsEMG)-torque relationships in the presence of delayed onset trunk muscle soreness (DOMS) and the effect of these relationships on torque steadiness (TS) and lumbar movement during concentric/eccentric submaximal trunk extension contractions. Twenty healthy individuals attended three laboratory sessions (24 h apart). HDsEMG signals were recorded unilaterally from the thoracolumbar erector spinae with two 64-electrode grids. HDsEMG-torque signal relationships were explored via coherence (0-5 Hz) and cross-correlation analyses. Principal component analysis was used for HDsEMG-data dimensionality reduction and improvement of HDsEMG-torque-based estimations. DOMS did not reduce either concentric or eccentric trunk extensor muscle strength. However, in the presence of DOMS, improved TS, alongside an altered HDsEMG-torque relationship and kinematic changes were observed, in a contraction-dependent manner. For eccentric trunk extension, improved TS was observed, with greater lumbar flexion movement and a reduction in δ-band HDsEMG-torque coherence and cross-correlation. For concentric trunk extensions, TS improvements were observed alongside reduced thoracolumbar sagittal movement. DOMS does not seem to impair the ability to control trunk muscle force, however, perceived soreness induced changes in lumbar movement and muscle recruitment strategies, which could alter motor performance if the exposure to pain is maintained in the long term.

Omega-3 Fatty Acid Supplementation on Post-Exercise Inflammation, Muscle Damage, Oxidative Response, and Sports Performance in Physically Healthy Adults-A Systematic Review of Randomized Controlled Trials.

Omega-3 is a family of n-3 polyunsaturated fatty acids (PUFAs), which have been used to treat a wide variety of chronic diseases, due mainly to their antioxidant and anti-inflammatory properties, among others. In this context, omega-3 could be post-exercise recovery agent and sports supplement that could improve performance by preserving and promoting skeletal muscle mass and strength. No conclusive evidence, however, exists about the potential effects of omega-3 on post-exercise biomarkers and sports performance in physically healthy adults. Based on the PRISMA in Exercise, Rehabilitation, Sports Medicine, and Sports Science (PERSiST) guidelines, we systematically reviewed studies indexed in Web of Science, Scopus, and Medline to assess the effects of omega-3 on post-exercise inflammation, muscle damage, oxidant response, and sports performance in physically healthy adults. The search was performed on original articles published in the last 10 years up to 5 May 2024, with a controlled trial design in which omega-3 supplementation was compared with a control group. Among 14,971 records identified in the search, 13 studies met the selection criteria. The duration of the interventions ranged from 1 day to 26 weeks of supplementation and the doses used were heterogeneous. Creatine kinase (CK) and lactate dehydrogenase (LDH) were significantly higher (p < 0.05) in the control group in 3 of the 4 studies where these markers were analyzed. C-reactive protein (CRP) was significantly higher (p < 0.05) in the control group of 2 of the 13 studies where this marker was analyzed. The delayed onset muscle soreness (DOMS) gave mixed results. Interleukin 6 (IL-6) showed improvements with supplementation, but tumor necrosis factor-α (TNF-α) displayed no differences. The consumption of n-3 PUFAs improved some indicators of oxidative stress such as reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio. Additional evidence is needed to establish clear recommendations regarding the dose and length of n-3 PUFA supplements. These may benefit the post-exercise inflammatory response, mitigate muscle damage, and decrease oxidative stress caused by exercise. However, studies did not evaluate omega-3 status at baseline or following supplementation and therefore the observations must be treated with caution.

Japanese encephalitis virus infection causes reactive oxygen species-mediated skeletal muscle damage.

Skeletal muscle wasting is a clinically proven pathology associated with Japanese encephalitis virus (JEV) infection; however, underlying factors that govern skeletal muscle damage are yet to be explored. The current study aims to investigate the pathobiology of skeletal muscle damage using a mouse model of JEV infection. Our study reveals a significant increment in viral copy number in skeletal muscle post-JEV infection, which is associated with enhanced skeletal muscle cell death. Molecular and biochemical analysis confirms NOX2-dependent generation of reactive oxygen species, leading to autophagy flux inhibition and cell apoptosis. Along with this, an alteration in mitochondrial dynamics (change in fusion and fission process) and a decrease in the total number of mitochondria copies were found during JEV disease progression. The study represents the initial evidence of skeletal muscle damage caused by JEV and provides insights into potential avenues for therapeutic advancement.

Does the Repeated-Bout Effect Influence Post-Activation Performance Enhancement in Recreational Runners?

Purpose: This study examined how a low dose of an eccentric-oriented lunge exercise could induce the repeated-bout effect (RBE) and affect the subsequent post-activation performance enhancement (PAPE) in recreational runners. Methods: Twenty male recreational runners (32.1 ± 2.8 years; 173.4 ± 6.1 cm; 73.3 ± 11.5 kg; 57.8 ± 7.2 mL·kg-1·min-1) were divided into control (N = 10) and experimental (N = 10) groups. In the first and fourth weeks, the groups were assessed for jump capacity, dynamic balance, and submaximal running kinematics before and after an incremental shuttle-run test until exhaustion. The experimental group was also submitted to two sessions of the eccentric-oriented lunge exercise (3 sets of 10 repetitions with 2 min of passive recovery) in the second and third weeks. Results: We observed that the first session promoted muscle damage, which was significantly (p < .05) reduced after the second training session, thus indicating an RBE. Meanwhile, there was no effect of the RBE on dynamic balance and submaximal running kinematics in the post-intervention. However, there was a significant increase in countermovement jump height (p = .008) for the experimental group when compared to the control group, although no PAPE was observed. Conclusions: The current results demonstrate that a simple, low-dose eccentric-oriented exercise may induce an RBE, leading to reduced muscle damage and a possibly improved lower limbs' muscle power in recreational runners. However, the absence of PAPE effects suggests that the RBE may not directly influence the potentiation/fatigue balance after fatiguing running exercises.

Effect of different Volumes of exercise on skin temperature responses over the following 24 hours.

Skin temperature responses have been advocated to indicate exercise-induced muscle soreness and recovery status. While the evidence is contradictory, we hypothesize that the presence of muscle damage and the time window of measurement are confounding factors in the skin temperature response. The objective was to determine whether skin temperature is influenced by different workloads and the time course of temperature measurements over the following 24 h. 24 trained male military were assigned to one of three groups: GC group (n = 8) serving as control not performing exercises, GE group (n = 8) performing a simulated military combat protocol in an exercise track with different obstacles but designed not to elicit muscle damage, and the GEMD group (n = 8) performing the simulated military combat protocol plus 5 sets of 20 drop jumps, with 10-sec between repetitions and with 2-min of rest between sets aiming to induce muscle damage. Skin temperature was measured using infrared thermography before exercise (Pre) and 4 (Post4h), 8 (Post8h) and 24h (Post24h) post-exercise. Perception of pain (DOMS) was evaluated Pre, Post24h, and Post48h, and countermovement jump height was evaluated at Pre and Post24h. DOMS did not differ between groups in the Pre and Post24h measures but GEMD presented higher DOMS than the other groups at Post48h (p < 0.001 and large effect size). Jump height did not differ for GEMD and GC, and GE presented higher jump height at Post24h than GC (p = 0.02 and large effect size). Skin temperature responses of GEMD and GG were similar in all measurement moments (p > 0.22), and GE presented higher skin temperature than the GC and the GEMD groups at Post24h (p < 0.01 and large effect sizes). In conclusion, although physical exercise elicits higher skin temperature that lasts up to 24 h following the efforts, muscle soreness depresses this response.

Acute inflammatory response following lower-and upper-body Wingate anaerobic test in elite gymnasts in relation to iron status.

Introduction: Artistic gymnastics is one of the most demanding sports disciplines, with the athletes demonstrating extremely high levels of explosive power and strength. Currently, knowledge of the effect of gymnastic training adaptation on exercise-induced inflammatory response is limited. The study aimed to evaluate inflammatory response following lower- and upper-body high-intensity exercise in relation to the iron status in gymnasts and non-athletes. Methods: Fourteen elite male artistic gymnasts (EAG, 20.6 ± 3.3 years old) and 14 physically active men (PAM, 19.9 ± 1.0 years old) participated in the study. Venous blood samples were taken before and 5 min and 60 min after two variants of Wingate anaerobic test (WAnT), upper-body and lower-body WAnT. Basal iron metabolism (serum iron and ferritin) and acute responses of selected inflammatory response markers [interleukin (IL) 6, IL-10, and tumour necrosis factor α] were analysed. Results: EAG performed significantly better during upper-body WAnT than PAM regarding relative mean and peak power. The increase in IL-6 levels after upper-body WAnT was higher in EAG than in PAM; the opposite was observed after lower-body WAnT. IL-10 levels were higher in EAG than in PAM, and tumour necrosis factor α levels were higher in PAM than those in EAG only after lower-body WAnT. The changes in IL-10 correlated with baseline serum iron and ferritin in PAM. Discussion: Overall, gymnastic training is associated with the attenuation of iron-dependent post-exercise anti-inflammatory cytokine secretion.

The Contrasting Effects of Two Distinct Exercise Training Modalities on Exhaustive Exercise-Induced Muscle Damage in Mice May Be Associated with Alterations in the Gut Microbiota.

Exhaustive exercise is known to induce muscle damage characterized by inflammation and oxidative stress. Although "regular" and "weekend warrior" exercise regimens have been shown to confer comparable health benefits in human studies, such as reduced risks of all-cause, cardiovascular disease (CVD), and cancer mortality, their differential impacts on muscle damage post-exhaustive exercise remain unclear. This study aimed to compare the effects of long-term, moderate-intensity (LTMI) and short-term, high-intensity (STHI) training modalities, matched for total exercise volume, on gut microbiota, short-chain fatty acids (SCFAs), and exhaustive exercise-induced muscle damage in mice, as well as to evaluate the correlation between these factors. LTMI is considered a regular exercise regimen, while STHI shares some similarities with the "weekend warrior" pattern, such as promoting exercise intensity and condensing training sessions into a short period. Our findings indicate that LTMI training significantly enhanced the abundance of SCFA-producing bacteria, including Akkermansia, Prevotellaceae_NK3B31_group, Odoribacter, Alistipes, and Lactobacillus, thereby increasing SCFA levels and attenuating muscle damage following exhaustive swimming. In contrast, STHI training increased the abundance of opportunistic pathogens such as Staphylococcus and Bilophila, without altering SCFA levels, and was associated with exacerbated muscle damage. Moreover, we observed a significant negative correlation between the abundance of SCFA-producing bacteria and SCFA levels with the expression of inflammatory cytokines in the muscle of mice post-exhaustive exercise. Conversely, the abundance of Staphylococcus and Bilophila showed a notable positive correlation with these cytokines. Additionally, the effects of LTMI and STHI on exhaustive exercise-induced muscle damage were transmissible to untrained mice via fecal microbiota transplantation, suggesting that gut microbiota changes induced by these training modalities may contribute to their contrasting impacts on muscle damage. These results underscore the significance of selecting an appropriate training modality prior to engaging in exhaustive exercise, with implications for athletic training and injury prevention.

Bioimpedance analysis for identifying new indicators of exercise-induced muscle damage.

A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = - 0.56 to - 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies.

Pre-exercise cryotherapy reduces myoglobin and creatine kinase levels after eccentric muscle stress in young women.

Introduction: The aim of this study was to investigate the effect of pre-exercise whole-body cryotherapy (WBC) on muscle damage indicators following eccentric treadmill exercise in young women. Methods: Twenty-seven participants underwent two 1-h downhill treadmill runs, replicating 60% of their maximal oxygen uptake, with a 4-week intermission for recovery and treatment application. In this intermission, one group underwent 20 sessions of WBC, delivered five times a week at -120°C for 3 min each, while the comparison group received no such treatment. Markers of muscle injury-serum myoglobin concentration, creatine kinase and lactate dehydrogenase activity and also uric acid, and cell-free DNA concentration-were measured before and after downhill runs. Results: The study observed a notable reduction in post-exercise myoglobin and CK levels in the WBC group after the second running session. Discussion: The results suggest that WBC can have a protective effects against muscle damage resulting from eccentric exercise.

Obesity is associated with muscle atrophy in rotator cuff tear.

Objective: The primary goal of this study is to evaluate the relationship between Body Mass Index (BMI) and muscle atrophy in individuals with rotator cuff tears. Methods: This study consists of patients with rotator cuff tears identified by MRI from two independent cohorts, the Rotator Cuff Outcomes Workgroup (ROW) and the Multicenter Orthopaedic Outcomes Network (MOON). Presence of atrophy (yes/no) and severity of atrophy (as an ordinal variable) were assessed on MRI by expert physicians. We used multivariable regression models to evaluate the relationship between BMI and muscle atrophy while adjusting for age and sex in each study, conducted sensitivity analyses for full-thickness tear and combined results using inverse variance-weighted meta-analysis. Results: A total of 539 patients (MOON=395, ROW=144) from the combined cohorts had MRI data available on muscle atrophy. Among these patients, 246 (46%) had atrophy of at least one of the muscles of the rotator cuff and 282 (52%) had full-thickness tears. In meta-analysis across both cohorts, each 5 kg/m2 increase in BMI was associated with a 21% (aOR=1.21, 95% CI=1.02, 1.43) increased odds of having muscle atrophy among individuals with any tear size, and 36% (aOR=1.36, 95% CI=1.01-1.81) increased odds among individuals with full-thickness tear. Conclusions: Higher BMI was associated with significantly higher odds of muscle atrophy in patiens with rotator cuff tears. More study is needed to unders1tand why and how this relationship exists, as well as whether interventions to reduce BMI may help improve outcomes for these patients. Level of Evidence: III.

Changes in protein fluxes and gene expression in non-injured muscle tissue distant from an acute myotoxic injury in male mice.

The response to acute myotoxic injury requires stimulation of local repair mechanisms in the damaged tissue. However, satellite cells in muscle distant from acute injury have been reported to enter a functional state between quiescence and active proliferation. Here, we asked whether protein flux rates are altered in muscle distant from acute local myotoxic injury and how they compare to changes in gene expression from the same tissue. Broad and significant alterations in protein turnover were observed across the proteome in the limb contralateral to injury during the first 10 days after. Interestingly, mRNA changes had almost no correlation with directly measured protein turnover rates. In summary, we show consistent and striking changes in protein flux rates in muscle tissue contralateral to myotoxic injury, with no correlation between changes in mRNA levels and protein synthesis rates. This work motivates further investigation of the mechanisms, including potential neurological factors, responsible for this distant effect. KEY POINTS: Previous literature demonstrates that stem cells of uninjured muscle respond to local necrotic muscle tissue damage and regeneration. We show that muscle tissue that was distant from a model of local necrotic damage had functional changes at both the gene expression and the protein turnover level. However, these changes in distant tissue were more pronounced during the earlier stages of tissue regeneration and did not correlate well with each other. The results suggest communication between directly injured tissue and non-affected tissues that are distant from injury, which warrants further investigation into the potential of this mechanism as a proactive measure for tissue regeneration from damage.

Changes in protein fluxes in skeletal muscle during sequential stages of muscle regeneration after acute injury in male mice.

Changes in protein turnover play an important role in dynamic physiological processes, including skeletal muscle regeneration, which occurs as an essential part of tissue repair after injury. The inability of muscle tissue to recapitulate this regenerative process can lead to the manifestation of clinical symptoms in various musculoskeletal diseases, including muscular dystrophies and pathological atrophy. Here, we employed a workflow that couples deuterated water (2H2O) administration with mass spectrometry (MS) to systematically measure in-vivo protein turnover rates across the muscle proteome in 8-week-old male C57BL6/J mice. We compared the turnover kinetics of over 100 proteins in response to cardiotoxin (CTX) induced muscle damage and regeneration at unique sequential stages along the regeneration timeline. This analysis is compared to gene expression data from mRNA-sequencing (mRNA-seq) from the same tissue. The data reveals quantitative protein flux signatures in response to necrotic damage, in addition to sequential differences in cell proliferation, energy metabolism, and contractile gene expression. Interestingly, the mRNA changes correlated poorly with changes in protein synthesis rates, consistent with post-transcriptional control mechanisms. In summary, the experiments described here reveal the signatures and timing of protein flux changes during skeletal muscle regeneration, as well as the inability of mRNA expression measurements to reveal changes in directly measured protein turnover rates. The results of this work described here provide a better understanding of the muscle regeneration process and could help to identify potential biomarkers or therapeutic targets.

Football Movement Profile-Based Creatine-Kinase Prediction Performs Similarly to Global Positioning System-Derived Machine Learning Models in National-Team Soccer Players.

PURPOSE: The relationship between external load and creatine-kinase (CK) response at the team/position or individual level using Global Positioning Systems (GPS) has been studied. This study aimed to compare GPS-derived and Football Movement Profile (FMP) -derived CK-prediction models for national-team soccer players. The second aim was to compare the performance of general and individualized CK prediction models. METHODS: Four hundred forty-four national-team soccer players (under 15 [U15] to senior) were monitored during training sessions and matches using GPS. CK was measured every morning from whole blood. The players had 19.3 (18.1) individual GPS-CK pairs, resulting in a total of 8570 data points. Machine learning models were built using (1) GPS-derived or (2) FMP-based parameters or (3) the combination of the 2 to predict the following days' CK value. The performance of general and individual-specific prediction models was compared. The performance of the models was described by R2 and the root-mean-square error (RMSE, in units per liter for CK values). RESULTS: The FMP model (R2 = .60, RMSE = 144.6 U/L) performed similarly to the GPS-based model (R2 = .62, RMSE = 141.2 U/L) and the combination of the 2 (R2 = .62, RMSE = 140.3 U/L). The prediction power of the general model was better on average (R2 = .57 vs R2 = .37) and for 73% of the players than the individualized model. CONCLUSIONS: The results suggest that FMP-based CK-prediction models perform similarly to those based on GPS-derived metrics. General machine learning models' prediction power was higher than those of the individual-specific models. These findings can be used to monitor postmatch recovery strategies and to optimize weekly training periodization.

Cell-free DNA kinetics in response to muscle-damaging exercise: A drop jump study.

A significant increase in circulating cell-free DNA (cfDNA) occurs with physical exercise, which depends on the type of exertion and the duration. The aims of this study were as follows: (1) to investigate the time course of cfDNA and conventional markers of muscle damage from immediately after to 96 h after muscle-damaging exercise; and (2) to investigate the relationship between cfDNA and indicators of primary (low-frequency fatigue and maximal voluntary isometric contraction) and secondary (creatine kinase and delayed-onset muscle soreness) muscle damage in young healthy males. Fourteen participants (age, 22 ± 2 years; weight, 84.4 ± 11.2 kg; height, 184.0 ± 7.4 cm) performed 50 intermittent drop jumps at 20 s intervals. We measured cfDNA and creatine kinase concentrations, maximal voluntary isometric contraction torque, low-frequency fatigue and delayed-onset muscle soreness before and at several time points up to 96 h after exercise. Plasma cfDNA levels increased from immediately postexercise until 72 h postexercise (P < 0.01). Elevation of postexercise cfDNA was correlated with both more pronounced low-frequency fatigue (r = -0.52, P = 3.4 × 10-11) and delayed-onset muscle soreness (r = 0.32, P = 0.00019). Levels of cfDNA change in response to severe primary and secondary muscle damage after exercise. Levels of cfDNA exhibit a stronger correlation with variables related to primary muscle damage than to secondary muscle damage, suggesting that cfDNA is a more sensitive marker of acute loss of muscle function than of secondary inflammation or damaged muscle fibres.

Exploring the Role of Extracellular Vesicles in Skeletal Muscle Regeneration.

Skeletal muscle regeneration entails a multifaceted process marked by distinct phases, encompassing inflammation, regeneration, and remodeling. The coordination of these phases hinges upon precise intercellular communication orchestrated by diverse cell types and signaling molecules. Recent focus has turned towards extracellular vesicles (EVs), particularly small EVs, as pivotal mediators facilitating intercellular communication throughout muscle regeneration. Notably, injured muscle provokes the release of EVs originating from myofibers and various cell types, including mesenchymal stem cells, satellite cells, and immune cells such as M2 macrophages, which exhibit anti-inflammatory and promyogenic properties. EVs harbor a specific cargo comprising functional proteins, lipids, and nucleic acids, including microRNAs (miRNAs), which intricately regulate gene expression in target cells and activate downstream pathways crucial for skeletal muscle homeostasis and repair. Furthermore, EVs foster angiogenesis, muscle reinnervation, and extracellular matrix remodeling, thereby modulating the tissue microenvironment and promoting effective tissue regeneration. This review consolidates the current understanding on EVs released by cells and damaged tissues throughout various phases of muscle regeneration with a focus on EV cargo, providing new insights on potential therapeutic interventions to mitigate muscle-related pathologies.

Effect of Spirulina Nigrita® Supplementation on Indices of Exercise-Induced Muscle Damage after Eccentric Protocol of Upper Limbs in Apparently Healthy Volunteers.

Spirulina is a supplement with antioxidant and anti-inflammatory properties that may enhance performance and recovery after intense exercise. The present study aimed to investigate the effects of Spirulina Nigrita® on physical performance, and recovery markers after intense eccentric exercise in healthy moderately physically active volunteers. In a double-blind crossover design, participants were supplemented either with spirulina (42 mg Kg-1 BW per day) or a placebo for 15 days before conducting an eccentric exercise protocol using the non-dominant arm. A six-week washout period was required between conditions. Performance and mobility markers such as isometric peak torque (PTQ), ligament range of motion (ROM), and perceived muscle discomfort (VAS) were assessed and blood samples (CK, LDH) were obtained at 1, 24, 48, and 72 h post-exercise. No significant differences were noticed between the two conditions on any of the investigated markers, indicating that spirulina supplementation has no positive effect on isometric muscle performance or alleviation of exercise-induced muscle damage (EIMD) symptoms in the specific population.

Effects of Omega-3 Supplementation on the Delayed Onset Muscle Soreness after Cycling High Intensity Interval Training in Overweight or Obese Males.

People with overweight or obesity preferred high-intensity interval training (HIIT) due to the time-efficiency and pleasure. However, HIIT leads to delayed onset muscle soreness (DOMS). The present study aimed to investigate the effects of omega-3 supplementation on DOMS, muscle damage, and acute inflammatory markers induced by cycling HIIT in untrained males with overweight or obesity. A randomized, double-blinded study was used in the present study. Twenty-four males with a sedentary lifestyle were randomly assigned to either receive omega-3 (O3) (4 g fish oil) or placebo (Con). Subjects consumed the capsules for 4 weeks and performed cycling HIIT at the 4th week. After 4 weeks-intervention, the omega-3 index of O3 group increased by 52.51% compared to the baseline. All subjects performed HIIT at 4th week. The plasma creatine kinase (CK) level of Con group increased throughout 48h after HIIT. While the CK level of O3 group increased only immediately and 24h after HIIT and decreased at 48h after HIIT. The white blood cell count (WBC) of Con group increased immediately after the HIIT, while O3 group did not show such increase. There was no change of CRP in both groups. O3 group had a higher reduction of calf pain score compared to Con group. O3 group also showed a recovery of leg strength faster than Con group. Omega-3 supplementation for 4 weeks lower increased CK level, reduced calf pain score, and recovery leg strength, DOMS markers after cycling HIIT.

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

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.