Comparison of Skeletal Muscle Tissue Oxygen Saturation Responses between Genders

Special attention should be given to subcutaneous thigh fat accrual and its impact on the amount of skeletal muscle blood flow and accumulation when using different initial restrictive pressure (IRP) during blood flow restriction (BFR) training. Due to different patterns of fat distribution and deposition in males and females, it is important to test the effects of subcutaneous fat on tissue oxygenation and lactate production during exercises with BFR. PURPOSE: The present study investigated the importance of thigh subcutaneous fat as a variable that may be associated with affecting the magnitude of initial pressure (tightness of cuffs before inflation with air) on skeletal muscle tissue oxygen saturation and lactate between males and females. METHODS: Twenty healthy volunteers, 10 males (25 ± 4.83 yr) and 10 females (20.7 ± 1.06 yr), performed exercises with an IRP of 40mmHg. The following procedures were performed in order: a) subcutaneous fat thickness, b) pre-maximal isometric force (MVC), c) 4 sets (1 × 30 reps and 3 × 15 reps) of dynamic knee extension exercises performed at 20% MVC, d) post-MVC. Skeletal muscle tissue oxygen saturation was continuously monitored before, during, and after exercises with near-infrared spectroscopy placed to a mark that was made at 50% on the line from the anterior superior iliac spine to the superior part of the patella. Plasma lactate levels were assessed prior to, in between the first and second set, immediately after post MVC, 5min-post, 10 min-post, and 20 min-post. RESULTS: Thigh subcutaneous fat thickness was significantly greater in females than males (p\u3c0.01). Tissue oxygenation significantly decreased (p\u3c0.03) throughout exercise in both genders with an observed significant time × gender interaction (p\u3c0.01). Both male and females responded to the BFR similarly with a significant decrease (p\u3c0.01) in peak force production from pre to post exercise, while plasma lactate levels significantly differed (p\u3c0.01) throughout the exercise with no time × gender interaction (p\u3c0.3). CONCLUSION: The observed gender difference in tissue oxygenation in response to BFR with an IRP of 40mmHg underline the necessity for future studies to consider subcutaneous fat as a variable to influence the magnitude of physiological adaptations between genders and adjust the IRP accordingly

Neuromuscular Responses during Knee Extension Exercise in Combination with Different Blood Flow Restriction Initial Pressures

Specifications of blood flow restriction training technique have been widely discussed to create a valid and reliable protocol. One of the unexplored variables is the effect of different initial restrictive pressures (tightness of cuffs, IRP) in combination with resistance exercise on neuromuscular responses and strength. PURPOSE: The purpose of this study was to determine any differences in amplitude (RMS) and median frequency (MDF) of electromyography (EMG) signals, as well as changes in strength during knee extension exercises with IRPs of 40-45 mmHg and 60-65 mmHg. METHODS: Twenty male subjects (age = 25.7 ± 4.3 yrs), participated in this study. They were required to attend the lab on 3 different occasions, with the first one being a familiarization session. On the subsequent sessions, participant\u27s upper leg was measured starting from the lateral epicondyle to the greater trochanter of the femur. An EMG electrode was placed at one-third the distance over the longitudinal axis of the vastus lateralis (VL) after shaving, abrading and cleaning with isopropyl alcohol. Initial restrictive pressure was randomly selected and participants completed a pre-exercise maximum voluntary contraction (MVC) test to determine their torque. For dynamic exercises, load was set at 20% MVC and each participant performed one set of 30 repetitions and three sets of 15 repetitions, separated by one minute rest. Post-exercise MVC was performed to assess the changes in leg strength following exercises. RESULTS: Results showed significant main effects (p\u3c0.01) in leg strength for condition (40-45 mmHg vs. 60-65 mmHg) and trial (pre vs. post MVC). A significant main effect was observed for condition for MVC EMG amplitude (p\u3c0.01). In addition, there were significant main effects for contractions (p\u3c0.01) in both EMG amplitude and MDF during dynamic exercises. CONCLUSION: The significant decreases in knee extension strength at IRP of 60-65 mmHg compared to IRP of 40-45mmHg from pre- to post-exercise suggest that subjects experienced more fatigue at 60-65 mmHg because of the decreased availability of oxygen to the working muscle. The use of different IRP will affect the level of blood flow and oxygen supply to skeletal muscle possibly causing variation in neuromuscular adaptation due to changes in total and type of muscle fiber recruitment

A Comparison of Hypertrophy Potential between the Vastus Lateralis and Rectus Femoris during Level Walking in Combination with Vascular Restriction.

Recent research has found that by compressing blood flow to working muscle during lower body exercise involving short bouts of walk training results in an increased muscle volume and improved quadriceps strength. However, the effects of vascular restriction (VR) during walking on neuromuscular adaptations as assessed by electromyography (EMG) activity may provide insight on how low intensity training with vascular restriction can be applied to various modes of exercise. PURPOSE: The purpose of this study was to explore and compare muscle activation changes of the quadriceps muscles during walking using EMG with and without blood flow restriction. METHODS: EMG electrodes were placed along the longitudinal axis of the vastus lateralis (VL) and rectus femoris (RF) of the right thigh of seven male volunteers (mean ± SD age = 22.7 ± 6.8 years; height = 178 ±5.4 cm; weight = 82.6 ± 7.7 kg). Placement of the electrode was marked at a point of 33.3% on VL, and RF 50% of the distance between the lateral femoral epicondyle and the greater trochanter. On two separate testing sessions, subjects walked on a treadmill for two, 10 minutes bouts separated by a 5 min rest period at a speed of 80.4 m*min-1 with and without blood flow restriction. RESULTS: There were significant main effects for both condition (with and without VR) and muscles (VL and RF), as well as an interaction between condition and muscles (condition*muscle) for EMG amplitude (RMS). On the other hand, there were no significant main effects or interactions for EMG median frequency (MDF). CONCLUSION: The findings suggest that walking with VR might cause neural adaptation in both VL and RF, but the VL might have a better potential for hypertrophic response when performing slow walking with blood flow restriction. Walking speed and the pressure used for compression during walking might change the pattern of response, therefore, both need to be given careful consideration in the design of future studies

Cost-effectiveness analysis of a pragmatic randomized trial evaluating surgical reconstruction versus rehabilitation in patients with long-standing anterior cruciate ligament injury

Aims The aim of this study was to estimate the incremental use of resources, costs, and quality of life outcomes associated with surgical reconstruction compared to rehabilitation for long-standing anterior cruciate ligament (ACL) injury in the NHS, and to estimate its cost-effectiveness. Methods A total of 316 patients were recruited and randomly assigned to either surgical reconstruction or rehabilitation (physiotherapy but with subsequent reconstruction permitted if instability persisted after treatment). Healthcare resource use and health-related quality of life data (EuroQol five-dimension five-level health questionnaire) were collected in the trial at six, 12, and 18 months using self-reported questionnaires and medical records. Using intention-to-treat analysis, differences in costs, and quality-adjusted life years (QALYs) between treatment arms were estimated adjusting for baseline differences and following multiple imputation of missing data. The incremental cost-effectiveness ratio (ICER) was estimated as the difference in costs divided by the difference in QALYs between reconstruction and rehabilitation. Results At 18 months, patients in the surgical reconstruction arm reported higher QALYs (0.052 (95% confidence interval (CI) -0.012 to 0.117); p = 0.177) and higher NHS costs (£1,017 (95% CI 557 to 1,476); p < 0.001) compared to rehabilitation. This resulted in an ICER of £19,346 per QALY with the probability of surgical reconstruction being cost-effective of 51% and 72% at a willingness-to-pay threshold of £20,000 and £30,000 per QALY, respectively. Conclusion Surgical reconstruction as a management strategy for patients with long-standing ACL injury is more effective, but more expensive, at 18 months compared to rehabilitation management. In the UK setting, surgical reconstruction is cost-effective

El efecto del nivel de proteína y lípidos sobre la acción dinámica específica y la excreción postprandial en sub-adultos del camarón blanco Litopenaeus vannamei

The study aimed to evaluate the effect of 4 levels of dietary protein (20, 30, 40 and 50%) and lipids (2, 4, 8 and 16%) on the magnitude and duration of specific dynamic action (SDA) and postprandial nitrogen excretion in the subadult white shrimpLitopenaeus vannameiusing computer-controlled metabolic chambers (continuous-flow respirometer). We determined the oxygen consumption rate at 1 h intervals until the postprandial oxygen consumption rate returned to the pre-feeding level. Shrimp fed all the diets had significantly higher respiration rates after feeding due to the SDA. Oxygen consumption, the SDA coefficient and the SDA magnitude increased notably with increasing dietary protein content. Shrimp fed the 20% protein diet had the lowest levels of pre- and post-feeding respiration and the smallest SDA. A significant change in the SDA coefficient relative to each lipid level was not demonstrable. Additionally, nitrogenous excretion increased with an increase of dietary protein but not with an increase of lipid level. By estimating the SDA of subadults, the response to standard metabolic rate (SMR) was lower than that reported for juveniles and postlarva white shrimp

Evolution of protein complexes by duplication of homomeric interactions.

BACKGROUND: Cellular functions are accomplished by the concerted actions of functional modules. The mechanisms driving the emergence and evolution of these modules are still unclear. Here we investigate the evolutionary origins of protein complexes, modules in physical protein-protein interaction networks. RESULTS: We studied protein complexes in Saccharomyces cerevisiae, complexes of known three-dimensional structure in the Protein Data Bank and clusters of pairwise protein interactions in the networks of several organisms. We found that duplication of homomeric interactions, a large class of protein interactions, frequently results in the formation of complexes of paralogous proteins. This route is a common mechanism for the evolution of complexes and clusters of protein interactions. Our conclusions are further confirmed by theoretical modelling of network evolution. We propose reasons for why this is favourable in terms of structure and function of protein complexes. CONCLUSION: Our study provides the first insight into the evolution of functional modularity in protein-protein interaction networks, and the origins of a large class of protein complexes

3D complex: a structural classification of protein complexes.

Most of the proteins in a cell assemble into complexes to carry out their function. It is therefore crucial to understand the physicochemical properties as well as the evolution of interactions between proteins. The Protein Data Bank represents an important source of information for such studies, because more than half of the structures are homo- or heteromeric protein complexes. Here we propose the first hierarchical classification of whole protein complexes of known 3-D structure, based on representing their fundamental structural features as a graph. This classification provides the first overview of all the complexes in the Protein Data Bank and allows nonredundant sets to be derived at different levels of detail. This reveals that between one-half and two-thirds of known structures are multimeric, depending on the level of redundancy accepted. We also analyse the structures in terms of the topological arrangement of their subunits and find that they form a small number of arrangements compared with all theoretically possible ones. This is because most complexes contain four subunits or less, and the large majority are homomeric. In addition, there is a strong tendency for symmetry in complexes, even for heteromeric complexes. Finally, through comparison of Biological Units in the Protein Data Bank with the Protein Quaternary Structure database, we identified many possible errors in quaternary structure assignments. Our classification, available as a database and Web server at http://www.3Dcomplex.org, will be a starting point for future work aimed at understanding the structure and evolution of protein complexes

Neuromuscular Responses of the Vastus Lateralis to Slow Walking With Vascular Restriction.

Motor unit recruitment of individual muscles could substantially differ with changes in speed and load. However, the recruitment patterns associated with low intensity walk training with vascular restriction at sustained loads and constant speed could be different than normal walking. Vascular restricted (VR) walk training is an effective method for increasing muscular strength; however the changes in motor unit recruitment and firing frequency have not been investigated to understand the mechanisms underlying the neuromuscular adaptations. Purpose: The purpose of this study was to analyze differences in electrical activity of the vastus lateralis during VR and non vascular restricted (non-VR) walking sessions. Methods: Seven healthy males [means ± (SD): age 22.7±(6.8) yrs, height 178±(5.4) cm, weight 181.7±(16.9) lbs.] performed both a VR walking session and a non-VR walking session for 20 minutes on a treadmill at a speed of 80.4 m-minˉ¹. During each walking period the subjects wore surface EMG electrodes that were placed along the longitudinal axis of the vastus lateralis (VL) of the right thigh at a distance of 33.3% between the lateral femoral epicondyle and the greater trochanter. A repeated measures ANOVA was used to determine the differences in both EMG amplitude (RMS) and median frequency of firing (MDF). Results: The VR walking session resulted in significantly greater RMS values compared to the non-VR walking session (p \u3c 0.05); however there was no main effect for time or interaction between condition and time. For EMG MDF, there were no significant main effects for condition or time, and no significant interaction. Conclusion: The results indicate that walking during VR of the lower limbs may have a greater impact on neural adaptation of the VL due to increased motor unit activation as indicated by an increased RMS value. This might occur because blood flow restriction affects motor unit recruitment patterns resulting in the recruitment of more high-threshold, fast-twitch muscle fibers

Searching for network modules

When analyzing complex networks a key target is to uncover their modular structure, which means searching for a family of modules, namely node subsets spanning each a subnetwork more densely connected than the average. This work proposes a novel type of objective function for graph clustering, in the form of a multilinear polynomial whose coefficients are determined by network topology. It may be thought of as a potential function, to be maximized, taking its values on fuzzy clusterings or families of fuzzy subsets of nodes over which every node distributes a unit membership. When suitably parametrized, this potential is shown to attain its maximum when every node concentrates its all unit membership on some module. The output thus is a partition, while the original discrete optimization problem is turned into a continuous version allowing to conceive alternative search strategies. The instance of the problem being a pseudo-Boolean function assigning real-valued cluster scores to node subsets, modularity maximization is employed to exemplify a so-called quadratic form, in that the scores of singletons and pairs also fully determine the scores of larger clusters, while the resulting multilinear polynomial potential function has degree 2. After considering further quadratic instances, different from modularity and obtained by interpreting network topology in alternative manners, a greedy local-search strategy for the continuous framework is analytically compared with an existing greedy agglomerative procedure for the discrete case. Overlapping is finally discussed in terms of multiple runs, i.e. several local searches with different initializations.Comment: 10 page