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.

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.

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.

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 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.

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.

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.

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.

Nutritional knowledge, eating habits, factors affecting muscle damage, and antioxidant enzyme levels of Korean wrestlers.

PURPOSE: The aim in this study was to investigate the diet and nutritional knowledge of elite Korean wrestlers and verify the differences in their exercise performance , muscle damage indicators, and antioxidant enzyme levels according to wrestler level. METHODS: A 7-day dietary and nutrition knowledge survey was administered to 30 adult male elite wrestlers (national team: n=11; professional team: n=19). The Wingate test was conducted for 60 seconds to analyze muscle damage indicators and antioxidant levels. Blood and blood lactate concentration analyses were performed four times; the statistical significance level of all data was p<0.05. RESULTS: Significant differences were found in general nutrition knowledge questionnaire (GNKQ) scores (p=0.043), diet (p=0.001), anaerobic performance (p=0.001), muscle damage indicators (p=0.026), antioxidant levels, and blood lactic acid concentrations (30 min after exercise, p=0.007; 90 min after exercise, p=0.038) between the national and the professional groups. CONCLUSION: To the findings confirm the relationship between the differences in diet, nutrition, and motor function for wrestlers of different expertise levels. In a follow-up, a comprehensive study on nutrition knowledge, athlete training , and weight loss is needed that considers a wider scope of subjects and analyzes additional variables.

[Advances in study of surgical approaches and MRI evaluation of total hip arthroplasty].

Objective: To review the research on different surgical approaches and MRI evaluation of total hip arthroplasty (THA), to clarify the possible muscle damage caused by different approaches, and to help clinicians avoid intraoperative muscle damage and identify the causes of certain muscle-related complications after operation. Methods: The research literature on different surgical approaches and MRI evaluation of THA at home and abroad was extensively reviewed to summarize the MRI performance of the posterior approach, modified direct lateral approach, direct anterior approach, and minimally invasive anterolateral approach (also called Orthopadische Chirurgie Munchen approach). Results: The traditional posterior approach mainly damages the short external rotator muscle group and increases the incidence of postoperative dislocation; the piriformis-keeping posterior approach significantly improves the quality of the pyriformis tendon in the postoperative period, but it may lead to damage to the intrapelvic portion of the piriformis muscle. The modified direct lateral approach mainly damages the gluteus medius muscle, which increases the risk of postoperative claudication. The direct anterior approach mainly damages the vastus tensoris muscle and may result in damage to the short external rotator muscle group and the muscles around the incision. The minimally invasive anterolateral approach primarily damages the superior gluteal nerve, which subsequently leads to denervation of the broad fascial tensor fasciae latae, and this approach may also result in injury to the gluteus medius and gluteus minimus muscles. The muscle damage status significantly affects prognosis, and the minimally invasive approach is more suitable for elderly patients. Conclusion: MRI can clarify the different types of muscle damage caused by different surgical approaches. Minimally invasive approaches can reduce muscle damage and improve postoperative function compared with traditional approaches, and can benefit elderly patients more, but due to the small field, forcing to expand the surgical field will lead to unintended muscle damage and reduce postoperative function.

The Influence of a Polyphenol-Rich Red Berry Fruit Juice on Recovery Process and Leg Strength Capacity after Six Days of Intensive Endurance Exercise in Recreational Endurance Athletes.

BACKGROUND: Various nutritional strategies are increasingly used in sports to reduce oxidative stress and promote recovery. Chokeberry is rich in polyphenols and can reduce oxidative stress. Consequently, chokeberry juices and mixed juices with chokeberry content are increasingly used in sports. However, the data are very limited. Therefore, this study investigates the effects of the short-term supplementation of a red fruit juice drink with chokeberry content or a placebo on muscle damage, oxidative status, and leg strength during a six-day intense endurance protocol. METHODS: Eighteen recreational endurance athletes participated in a cross-over high intensity interval training (HIIT) design, receiving either juice or a placebo. Baseline and post-exercise assessments included blood samples, anthropometric data, and leg strength measurements. RESULTS: A significant increase was measured in muscle damage following the endurance protocol in all participants (∆ CK juice: 117.12 ± 191.75 U/L, ∆ CK placebo: 164.35 ± 267.00 U/L; p = 0.001, η2 = 0.17). No group effects were detected in exercise-induced muscle damage (p = 0.371, η2 = 0.010) and oxidative status (p = 0.632, η2 = 0.000). The reduction in strength was stronger in the placebo group, but group effects are missing statistical significance (∆ e1RM juice: 1.34 ± 9.26 kg, ∆ e1RM placebo: -3.33 ± 11.49 kg; p = 0.988, η2 = 0.000). CONCLUSION: Although a reduction in strength can be interpreted for the placebo treatment, no statistically significant influence of chokeberry could be determined. It appears that potential effects may only occur with prolonged application and a higher content of polyphenols, but further research is needed to confirm this.

Clinical presentation and outcomes of patients with rhabdomyolysis: A tertiary care center experience.

OBJECTIVES: To evaluate the clinical and laboratory features, complications, and outcomes of patients with rhabdomyolysis in the Saudi population. METHODS: Retrospectives descriptive study of adult patients who presented to King Abdulaziz Medical City (KAMC) withrhabdomyolysis between January 2016 and December 2022. RESULTS: Most of the participants (84.5%) were male, with a median age of 41 years and a body mass index of 26.5 kg/m2. Medications, mainly statins (22.4%) and illicit drugs (15.5%), constituted the root causes of rhabdomyolysis in the cohort (44.8%). The most common presenting complaints were myalgia (63.8%) and fatigue (37.9%). More than one-third of the participants (32.8%) developed AKI, with 3 patients requiring temporary hemodialysis, and only 8.6% developed acute liver failure (ALF). Intensive care unit (ICU) admission was required for 10 patients (17.2%), and the overall mortality rate was 8.6%. Patients who developed complications (composite outcomes of AKI, ALF, multiorgan failure, or death) had significantly reduced kidney function and higher levels of blood urea nitrogen, anion gap, and uric acid upon admission than those who did not. CONCLUSION: This study offers a thorough understanding of clinical and laboratory features, causes, complications, and outcomes of rhabdomyolysis among Saudi patients. The insights gained enhance our understanding of rhabdomyolysis within this population, providing a foundation for future research and improvements in clinical management.

Muscle ultrasound to identify prednisone-induced muscle damage in adults with nephrotic syndrome.

Steroid myopathy is a non-inflammatory toxic myopathy that primarily affects the proximal muscles of the lower limbs. Due to its non-specific symptoms, it is often overshadowed by patients' underlying conditions. Prolonged or high-dosage use of glucocorticoids leads to a gradual decline in muscle mass. There are no tools available to identify the course of steroid myopathy before the patient displays substantial clinical symptoms. In this study, we investigated individuals with nephrotic syndrome receiving prednisone who underwent muscle ultrasound to obtain cross-sectional and longitudinal pictures of three major proximal muscles in the lower limbs: the vastus lateralis, tibialis anterior, and medial gastrocnemius muscles. Our findings revealed that grip strength was impaired in the prednisolone group, creatine kinase levels were reduced within the normal range; echo intensity of the vastus lateralis and medial gastrocnemius muscles was enhanced, the pennation angle was reduced, and the tibialis anterior muscle exhibited increased echo intensity and decreased thickness. The total dose of prednisone and the total duration of treatment impacted the degree of muscle damage. Our findings indicate that muscle ultrasound effectively monitors muscle structure changes in steroid myopathy. Combining clinical symptoms, serum creatine kinase levels, and grip strength improves the accuracy of muscle injury evaluation.

Optimization of the Diagnostic Capacity of Traditional Biomarkers in Muscle Damage and Its Use in the Diagnosis of Dermatomyositis and Polymyositis.

BACKGROUND-AIM: Creatine kinase (CK) and aldolase are markers traditionally used in the study of muscle damage (MD). As CK determination is more specific to muscle damage, the demand for both determinations in routine laboratory tests would entail an extra cost. METHODS: Retrospective observational study conducted between 2019-2020. CK and aldolase concentrations from 218 patients were studied.ROC curves were analyzed for CK and aldolase for muscle damage detection. Cut-off values were selected for both strategies. Specifity of CK and aldolase for dermatomyositis or polymyositis diagnosis in our population was studied using the McNemar's test. RESULTS: The area under the ROC curve (AUC) for total CK was 0.716 (95%CI: 0.651-0.775), for CK in males it was 0.703 (95%CI: 0.592-0.799), and for CK in females was 0.719 (95%CI: 0.636-0.793). For aldolase, AUC was 0.505 (95%CI: 0.437-0.573). Optimized cut-off points for each determination were: 112 U/L for CK in men, with a sensitivity of 73.9% (95%CI: 51.6-89.8) and a specificity of 49.2% (95%CI: 35.9-62.5); 88 U/L for CK in women, with a sensitivity of 75.0% (95%CI: 57.8-87.9) and specificity of 50.5% (95%CI: 40.4-60.6); and 5.6 U/L for aldolase, with a sensitivity of 61.0% (95%CI: 53.2-68.8) and a specificity of 38.8% (95%CI: 26.5-52.6).Regarding the individuals diagnosed with dermatomyositis or polymyositis, 66.7% and 44.4% of them were correctly classified as pathological by CK and aldolase results, respectively. McNemar's test did not reveal significant differences. CONCLUSION: The determination of CK offers a better diagnostic performance of MD and, in addition, does not present significant differences regarding the determination of aldolase in cases of polymyositis and dermatomyositis. Therefore, the single determination of CK would be sufficient for MD screening.

Optimizing strength training protocols in young females: A comparative study of velocity-based and percentage-based training programs.

The purpose of this study was to compare the effects of velocity-based strength training (VBT) and percentage-based strength training (PBT) on absolute strength, explosive strength, speed, and agility, as well as markers of muscle damage after 6 weeks of exercise programs. The study included 30 young female individuals, divided into three groups of 10 participants: VBT, PBT, and control group. The main findings indicated that the VBT group and PBT group showed significant improvement in 1RM squat exercise (Δ% 27.87 and Δ% 8.98, respectively) and 1RM bench press (Δ% 14.47 and Δ% 8.65, respectively), but a greater enhancement was observed in the VBT group. In addition, VBT induced substantial changes in SJ (Δ% 14.32) and CMJ height (Δ% 7.69), while PBT had an improvement only in the SJ test (Δ% 6.72). The improvement noted in the VBT group could be attributed to its ability to tailor training intensity according to the speed of movement execution. This approach allows athletes to perform each repetition as fast as possible, thus maintaining an optimal intensity for explosive strength development. The capacity of VBT to adapt training intensity based on the speed of movement execution may be the key factor contributing to these results. Therefore, coaches and athletes should consider implementing VBT as a valuable tool to optimize strength and power development. In conclusion, VBT induced greater improvement in the 1RM squat, 1RM bench press, SJ, and CMJ compared to the group that performed the traditional strength training modality. Therefore, VBT is considered a more effective training tool regarding the development of absolute and explosive strength in young women.