Neuromuscular electrical stimulation (NMES) can improve physical function in different populations. NMES-related outcomes may be influenced by muscle length (i.e., joint angle), a modulator of the force generation capacity of muscle fibers. Nevertheless, to date, there is no comprehensive synthesis of the available scientific evidence regarding the optimal joint angle for maximizing the effectiveness of NMES. We performed a systematic review to investigate the effect of muscle length on NMES-induced torque, discomfort, contraction fatigue, and strength training adaptations in healthy and clinical adult populations (PROSPERO: CRD42022332965). We conducted searches across seven electronic databases: PUBMED, Web of Science, EMBASE, PEDro, BIREME, SCIELO, and Cochrane, over the period from June 2022 to October 2023, without restricting the publication year. We included cross-sectional and longitudinal studies that used NMES as an intervention or assessment tool for comparing muscle lengths in adult populations. We excluded studies on vocalization, respiratory, or pelvic floor muscles. Data extraction was performed via a standardized form to gather information on participants, interventions, and outcomes. Risk of bias was assessed using the Revised Cochrane risk-of-bias tool for cross-over trials and the Physiotherapy Evidence Database scale. Out of the 1185 articles retrieved through our search strategy, we included 36 studies in our analysis, that included 448 healthy young participants (age: 19-40 years) in order to investigate maximum evoked torque (n = 268), contraction fatigability (n = 87), discomfort (n = 82), and muscle strengthening (n = 22), as well as six participants with spinal cord injuries, and 15 healthy older participants. Meta-analyses were possible for comparing maximal evoked torque according to quadriceps muscle length through knee joint angle. At optimal muscle length 50° - 70° of knee flexion, where 0° is full extension), there was greater evoked torque during nerve stimulation compared to very short (0 - 30°) (p<0.001, CI 95%: -2.03, -1.15 for muscle belly stimulation, and -3.54, -1.16 for femoral nerve stimulation), short (31° - 49°) (p = 0.007, CI 95%: -1.58, -0.25), and long (71° - 90°) (p<0.001, CI 95%: 0.29, 1.02) muscle lengths. At long muscle lengths, NMES evoked greater torque than very short (p<0.001, CI 95%: -2.50, -0.67) and short (p = 0.04, CI 95%: -2.22, -0.06) lengths. The shortest quadriceps length generated the highest perceived discomfort for a given current amplitude. The amount of contraction fatigability was greater when muscle length allowed greater torque generation in the pre-fatigue condition. Strength gains were greater for a protocol at the optimal muscle length than for short muscle length. The quality of evidence was very high for most comparisons for evoked torque. However, further studies are necessary to achieve certainty for the other outcomes. Optimal muscle length should be considered the primary choice during NMES interventions, as it promotes higher levels of force production and may facilitate the preservation/gain in muscle force and mass, with reduced discomfort. However, a longer than optimal muscle length may also be used, due to possible muscle lengthening at high evoked tension. Thorough understanding of these physiological principles is imperative for the appropriate prescription of NMES for healthy and clinical populations.

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) is a common orthopedic surgery procedure whose incidence has increased over the past few decades. Nevertheless, it is believed that neuromuscular control remains altered from the early stages after ACLR to later years. Therefore, the aim of this study was to systematically evaluate the magnitude of co-contraction during functional tasks in subjects with unilateral ACLR.
METHODS: A systematic review design was followed. The search strategy was conducted in PubMed, Scopus, EBSCO, PEDro, Cochrane Library, and Web of Science databases from inception to March 2024. The inclusion criteria involved studies using electromyography (EMG) data to calculate muscle pair activation via the co-contraction index (CCI) in ACLR individuals during functional tasks. The Preferred Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and study quality was evaluated using National Institutes of Health (NIH) Study Quality Assessment Tools.
RESULTS: The search strategy found a total of 792 studies, of which 15 were included in this systematic review after reviewing the eligibility criteria. The magnitude of co-contraction was assessed in a total of 433 ACLR individuals and 206 controls during functional tasks such as hop, drop-land, step-up/step-down, and gait. Overall, approximately 79.6% of individuals who had undergone ACLR exhibited increased levels of co-contraction magnitude in the ACLR limb, while 8.5% showed low co-contraction levels.
CONCLUSIONS: The findings of the review suggest that, during functional tasks, most individuals who have undergone ACLR exhibit changes of co-contraction magnitude in the involved limb.

BACKGROUND: Hypopressive exercises have been mainly used in the treatment of pelvic floor dysfunctions. Recently it has started to spread among healthy women. However, no comprehensive review is available in this population.
OBJECTIVE: Assess the current evidence of the effects of hypopressive exercises on healthy women.
METHODS: This study was registered on PROSPERO (CRD42020203103). The search was performed in Scielo, Pubmed, Lilacs, Embase, Scopus, Pedro, Trip Database, Web of Science, and Google Scholar. The last search was performed on November 1st, 2021. Inclusion criteria were randomized controlled trials and single-arm trials, healthy women, acute or late effects of hypopressive exercises, and pre and post-training analysis. Exclusion criteria included non-original research, conference proceedings, dissertations and theses. Downs and Black checklist were used to assess the methodological quality. Study design, participants characteristics, description of the intervention, follow-up period, variables, instruments, and outcomes were extracted and recorded.
RESULTS: From the 410 studies, five were selected. The variable of major interest was waist circumference, which showed a decrease with exercise. It also seemed to have plausible positive effects on height, lower back mobility, abdominal and pelvic floor muscle contraction, respiratory flow and apnea, and hemodynamic responses.
CONCLUSIONS: This study suggests that the current literature on the effects of hypopressive exercise on healthy women is very limited. Despite the plausible positive effects identified, we cannot recommend its practice due to the serious methodological problems. Therefore, more studies are needed to elucidate the benefits and adverse effects of hypopressive exercises.

OBJECTIVE: Surface electromyography is commonly applied to measure the electrophysiological activity of the neuromuscular system. However, there is no consensus regarding the best protocol to assess pelvic floor muscles.
METHODS: A scoping literature review was carried out in six databases, using MeSH descriptors. It included studies with electromyographic assessment in adult women presenting or not with pelvic floor dysfunction. The results were presented in categories to contribute to the development of a protocol considering the most used parameters for non-invasive assessment of myoelectric activity of pelvic floor muscles.
RESULTS: A total of 1,074 articles were identified, and 146 studies were selected for analysis. The intravaginal probe was used in 80.8% of the studies, the bipolar sensor with metallic plates placed on both sides of the vagina was the most frequent (71.3%), with a reference electrode positioned on the anterior superior iliac spine (33.5%). The supine position with hip and knee flexed (45.2%) was the most frequent position used. Of the studies, 44.5% normalized the data by maximum voluntary contraction (MVC) whereas 44.5% performed an average of 3 MVCs.
CONCLUSIONS: The most frequently used protocol for the pelvic floor is the bipolar intracavitary probe with metal plates positioned at 3-9 o\'clock and introduced distally to the vaginal introitus with the volunteer in the supine position and the hip and knee flexed with the reference placed on the anterior-superior iliac spine.

Fatty acid translocase (FAT/CD36) is a transmembrane glycoprotein belonging to the scavenger class B receptor family and is encoded by the cluster of differentiation 36 (CD36) gene. This receptor has a high affinity for fatty acids and is involved in lipid metabolism. An abundance of FAT/CD36 during exercise occurs in mitochondria and solitary muscles. As such, we aimed to systematically review the evidence for the relationship FAT/CD36 and adipose tissue lipolysis during exercise training. Five electronic databases were selected for literature searches until June 2022: PubMed, Web of Science, Scopus, science direct, and Google Scholar. We combined the different synonyms and used the operators (\"AND\", \"OR\", \"NOT\"): (CD36 gene) OR (CD36 polymorphism) OR (cluster of differentiation 36) OR (FAT/CD36) OR (fatty acid translocase) OR (platelet glycoprotein IV) OR (platelet glycoprotein IIIb) AND (adipose tissue lipolysis) OR (fatty acids) OR (metabolism lipid) OR (adipocytes) AND (physical effort) OR (endurance exercise) OR (high-intensity training). All published cross-sectional, cohort, case-control, and randomized clinical trials investigating CD36 polymorphisms and adipose tissue lipolysis during exercise in subjects (elite and sub-elite athletes, non-athletes, sedentary individuals and diabetics), and using valid methods to measure FAT/CD36 expression and other biomarkers, were considered for inclusion in this review. We initially identified 476 publications according to the inclusion and exclusion criteria, and included 21 studies investigating FAT/CD36 and adipose tissue lipolysis during exercise in our systematic review after examination of titles, abstracts, full texts, and quality assessments using the PEDro scale. There were nine studies with male-only participants, three with female-only participants, and nine studies included both female and male participants. There were 859 participants in the 21 selected studies. Studies were classified as either low quality (n = 3), medium quality (n = 13), and high quality (n = 5). In general, the data suggests an association between FAT/CD36 and adipose tissue lipolysis during exercise training. Improvements in FAT/CD36 were reported during or after exercise in 6 studies, while there were no changes reported in FAT/CD36 in 4 studies. An association between fat oxidation and FAT/CD36 expression during exercise was reported in 7 studies. No agreement was reached in 5 studies on FAT/CD36 content after dietary changes and physical interventions. One study reported that FAT/CD36 protein expression in muscle was higher in women than in men, another reported that training decreased FAT/CD36 protein in insulin-resistant participants, while another study reported no differences in FAT/CD36 in young, trained individuals with type 2 diabetes. Our analysis shows an association between FAT/CD36 expression and exercise. Furthermore, an association between whole-body peak fat oxidation and FAT/CD36 expression during exercise training was demonstrated. Systematic Review Registration: [PROSPERO], identifier [CRD42022342455].

Skeletal muscle necrosis is a common clinical manifestation of snakebite envenoming. The predominant myotoxic components in snake venoms are catalytically-active phospholipases A2 (PLA2) and PLA2 homologs devoid of enzymatic activity, which have been used as models to investigate various aspects of muscle degeneration. This review addresses the changes in the contractile apparatus of skeletal muscle induced by these toxins. Myotoxic components initially disrupt the integrity of sarcolemma, generating a calcium influx that causes various degenerative events, including hypercontraction of myofilaments. There is removal of specific sarcomeric proteins, owing to the hydrolytic action of muscle calpains and proteinases from invading inflammatory cells, causing an initial redistribution followed by widespread degradation of myofibrillar material. Experiments using skinned cardiomyocytes and skeletal muscle fibers show that these myotoxins do not directly affect the contractile apparatus, implying that hypercontraction is due to cytosolic calcium increase secondary to sarcolemmal damage. Such drastic hypercontraction may contribute to muscle damage by generating mechanical stress and further sarcolemmal damage.

UNASSIGNED: Doma, K, Matoso, B, Protzen, G, Singh, U, and Boullosa, D. The repeated bout effect of multiarticular exercises on muscle damage markers and physical performances: a systematic review and meta-analyses. J Strength Cond Res 37(12): 2504-2515, 2023-This systematic review and meta-analysis compared muscle damage markers and physical performance measures between 2 bouts of multiarticular exercises and determined whether intensity and volume of muscle-damaging exercises affected the outcomes. The eligibility criteria consisted of (a) healthy male and female adults; (b) multiarticular exercises to cause muscle damage across 2 bouts; (c) outcome measures were compared at 24-48 hours after the first and second bouts of muscle-damaging exercise; (d) at least one of the following outcome measures: creatine kinase (CK), delayed onset of muscle soreness (DOMS), muscle strength, and running economy. Study appraisal was conducted using the Kmet tool, whereas forest plots were derived to calculate standardized mean differences (SMDs) and statistical significance and alpha set a 0.05. After screening, 20 studies were included. The levels of DOMS and CK were significantly greater during the first bout when compared with the second bout at T24 and T48 (p < 0.001; SMD = 0.51-1.23). Muscular strength and vertical jump performance were significantly lower during the first bout compared with the second bout at T24 and T48 (p ≤ 0.05; SMD = -0.27 to -0.40), whereas oxygen consumption and rating of perceived exertion were significantly greater during the first bout at T24 and T48 (p < 0.05; SMD = 0.28-0.65) during running economy protocols. The meta-analyses were unaffected by changes in intensity and volume of muscle-damaging exercises between bouts. Multiarticular exercises exhibited a repeated bout effect, suggesting that a single bout of commonly performed exercises involving eccentric contractions may provide protection against exercise-induced muscle damage for subsequent bouts.

Tendons transmit the muscle contraction forces to bones and drive joint movement throughout life. While extensive research have indicated the essentiality of mechanical forces on tendon development, a comprehensive understanding of the fundamental role of mechanical forces still needs to be impaerted. This scoping review aimed to summarize the current knowledge about the role of mechanical forces during the tendon developmental phase. The electronic database search using PubMed, performed in May 2023, yielded 651 articles, of which 16 met the prespecified inclusion criteria. We summarized and divided the methods to reduce the mechanical force into three groups: loss of muscle, muscle dysfunction, and weight-bearing regulation. In contrast, there were few studies to analyze the increased mechanical force model. Most studies suggested that mechanical force has some roles in tendon development in the embryo to postnatal phase. However, we identified species variability and methodological heterogeneity to modulate mechanical force. To establish a comprehensive understanding, methodological commonality to modulate the mechanical force is needed in this field. Additionally, summarizing chronological changes in developmental processes across animal species helps to understand the essence of developmental tendon mechanobiology. We expect that the findings summarized in the current review serve as a groundwork for future study in the fields of tendon developmantal biology and mechanobiology.

BACKGROUND: The International Continence Society (ICS) recommends the use of perineometry and digital palpation to assess the pelvic floor muscles (PFM). Exploring the degree of correlation between both assessment strategies will serve to improve safety for clinical practice. Therefore, we performed a systematic review and meta-analysis on the correlation between assessment strategies.
METHODS: Observational studies were included. Bias risk assessment based on Downs and Black scale and the evidence\'s level were assessed using the GRADE. The random effect model measured the correlation values and were quantitatively analyzed through meta-analysis. Registration in PROSPERO database - CRD42021253775.
RESULTS: Six studies were selected. There was a high positive correlation between perineometry and MOS (r = 0.74; 95%-IC 0.61-0.83; I2: 81%, p < 0.01). Subgroup analysis was performed with 3 studies with continent women, and revealed a high positive correlation (r = 0.80; 95%-IC 0.62-0.90; I2: 90%, p < 0.01), while 2 studies with incontinent women revealed a moderate positive correlation (r = 0.64; 95%-IC 0.48-0.75; I2: 0%, p = 0.40). GRADE analysis revealed a low strength of evidence.
CONCLUSIONS: The high positive correlation between perineometry and MOS suggests that if the assessment strategies are applied in a standardized way, these tests can be used together or separately to assess the functionality of PFMs in clinical practice. However, the results should be interpreted with caution due to the low strength of GRADE evidence.

The association between pelvic pain and pelvic floor muscle (PFM) tone in women with persistent noncancer pelvic pain (PNCPP) is unclear.
To synthesize the evidence of the association between pelvic pain and PFM tone in women with PNCPP.
A systematic review was conducted via MEDLINE, Emcare, Embase, CINAHL, PsycINFO, and Scopus to identify relevant studies. Studies were eligible if pelvic pain and PFM tone outcome measures were reported among women aged >18 years. The National Heart, Lung, and Blood Institute\'s Quality Assessment Tool for Observational Cohort and Cross-sectional Studies was used to assess study quality. Studies were pooled by assessment of PFM tone via a random effects model. Associations between the presence of pelvic pain and PFM tone were assessed with odds ratio (OR), while linear associations were assessed with Pearson or Spearman correlation.
Pelvic pain measures (intensity, threshold, and frequency) and resting PFM tone in women with PNCPP, as evaluated by any clinical assessment method or tool.
Twenty-four studies were included in this review. The presence of pelvic pain was significantly associated with increased PFM tone as assessed by digital palpation (OR, 2.85; 95% CI, 1.66-4.89). Pelvic pain intensity was inversely but weakly associated with PFM flexibility when evaluated through dynamometry (r = -0.29; 95% CI, -0.42 to -0.17). However, no significant associations were found between pelvic pain and PFM tone when measured with other objective assessment methods.
Pelvic pain and increased PFM tone may not be directly associated; alternatively, a nonlinear association may exist. A range of biopsychosocial factors may mediate or moderate the association, and clinicians may need to consider these factors when assessing women with PNCPP.
This review was reported according to the PRISMA guidelines. All possible findings from relevant theses and conference abstracts were considered in our search. However, nonlinear associations between pelvic pain and increased PFM tone were not assessed as part of this review.
Pelvic pain may be linearly associated with increased PFM tone and decreased PFM flexibility when measured with digital palpation or dynamometry; however, this association was not observed when other aspects of PFM tone were assessed through objective methods. Future studies are required using robust assessment methods to measure PFM tone and analyses that account for other biopsychosocial factors that may influence the association.