Greater Increase In Strength Research Articles

ИССЛЕДОВАНИЕ ВЛИЯНИЯ МОДИФИЦИРУЮЩИХ ДОБАВОК НА СВОЙСТВА БЕТОНА

The problem of improving the efficiency of the quality of concrete and reinforced concrete is a promising direction that cannot be fully realized without the use of chemical additives. Additives are considered a simple way to improve the performance of a cement composite; they allows to reduce the amount of binder and regulate the technological characteristics of the concrete mixture and the physical and mechanical properties of the material, as well as increase the durability of buildings and structures. Currently, a large number of additives are used, introduced into concrete mixtures, which are classified according to their mechanism of action, chemical composition and other characteristics. The purpose of this research was to optimize the compositions of concrete with additives in terms of strength and deformability. The object of the study is fine-grained concrete produced on a cement binder using various modifying additives, for which modifiers such as «Advance Ultra», «Superplast Prima», «Superplast Standard» have been studied. The studied parameters were the compressive strength and elastic modulus of fine-grained concrete. It was revealed that the introduction of modifying additives helped to increase the studied indicators. At the same time, the greatest increase in strength and elastic modulus is achieved when using the Advance Ultra plasticizer

EFFECTS OF 12-WEEK ISOKINETIC TRAINING ON KNEE STABILIZERS STRENGTH AND THE EFFICIENCY OF THE PERFORMANCE OF GYMNASTICS VAULTS

Abstract
 The aim of the research was to examine the effects of isokinetic training on knee stabilizer strength, and whether this increases the efficiency of performing basic gymnastics vaults. A total of 60 respondents, students of the Faculty of Sports and Physical Education (average age 19.7±1.5 years, weight 75.3±2.9 kg, height 179.8±6.7 cm) were included. The subjects were divided into two groups, experimental (EG) (n=30) and control (CG) (n=30). As part of the 12-week program, the experimental group (EG) in addition to exercises within the regular classes at the university had an additional concentric isokinetic training 3 times a week on the Biodex System 3 dynamometer, while the control group (CG) only had exercises within the regular classes at the university. The results showed statistically significant differences (p < 0.05) between (EG) and (CG), both, in increasing the strength of the knee stabilizers and in the performance of gymnastics vaults, and the strength of the knee extensors and flexors in favor of (EG). It can be concluded that the additional isokinetic training resulted in a greater increase in strength, but also a better performance of gymnastics vaults.

Mechanical performance of an elastomeric bearing incorporated within steel ring restrainers

Unseating may be one of the most severe forms of damage to a bridge caused by an earthquake; such an event may lead to catastrophic span falling or collapse. A novel elastomeric bearing incorporated within steel ring restrainers (EB-SRRs) to prevent the unseating of bridges is therefore proposed. The EB-SRRs consists mainly of an elastomeric bearing in the center and multiple steel ring restrainers (SRRs) symmetrically distributed on both sides. The finite element (FE) model of the EB-SRRs is established, and its reliability is validated using data from earlier experiments. A parametric analysis of the EB-SRR performance is undertaken using the FE method. Finally, a method for the prediction of the mechanical behavior of the EB-SRRs is proposed. The results show that EB-SRRs can provide multi-level mechanical properties: compared with traditional EB, EB-SRRs has the same behavior under small horizontal load but provide a slight increase in strength and energy dissipation under moderate horizontal load and a greater increase in strength and energy dissipation under large horizontal load.The cross-section height h and cross-section width w mainly affect the ultimate bearing capacity Fu and the energy dissipation of the EB-SRRs; steel ring radius R, guide pulley diameter D, and straight part length a mainly affect the ultimate displacement δu; the straight part length a significantly affect the activation displacement δa. The method of predicting the force–displacement curves of the EB-SRRs proposed in this study is shown to be accurate.

Performance of eco-friendly polymers for soil stabilization and their resistance to freeze–thaw action

Soil improvement methods using environmentally friendly additives have gained popularity with increased environmental awareness. In the future, environmentally friendly polymers can be preferred in the stabilization of many geotechnical applications like the base of roads, landfills, and sub-base of foundations. This means the mechanical properties of these eco-friendly polymers should be investigated in detail. For this purpose, changes in the mechanical properties of specimens treated with different polymer types under freeze–thaw action were investigated. Three types of polymers which are xanthan gum, guar gum, and anionic polyacrylamide polymer were used to improve the strength properties of kaolin clay. The specimens were prepared in 3 different anionic polymer contents and 4 different biopolymer content. After 7, 14, and 28-day curing periods specimens were subjected to 5 and 10 cycles of freezing–thawing to observe freeze–thaw action by conducting unconfined compression tests and the control specimens were directly subjected to unconfined compression tests after the curing period. Regarding the outcomes obtained, both synthetic and biological polymer use induced strength gain. Guar gum which is a biological polymer is the most effective that improves the strength by around 8 times than pure clay. This increment ratio varied between 2 and 3.5 times in polyacrylamide polymer, which is a greater strength increase than in previous studies. In addition, curing time has no significant effect on strength gain in anionic polyacrylamide-contained specimens. It was also observed that freezing–thawing caused a drastic reduction in strength by around 5 to 60%, however, the anionic polymer is the most resistant to freeze–thaw considering the strength loss. As a result, eco-friendly polymers are suitable in regions exposed to freeze–thaw action between the seasons.

Effect of three MWCNTs-COOH (chiral, zigzag and armchair) on the mechanical properties and water absorption of cement-based composites

In this study, multi-walled nanotubes (MWCNTs) functionalized with carboxyl group are used as additives with different morphologies of chiral, zigzag and armchair to investigate the effects of three MWCNTs on the mechanical and water absorption properties of cement-based composites. Accordingly, two different concentrations of 0.05 and 0.1 wt.% of MWCNTs are incorporated in the cement paste with a water-to-cement ratio of 0.4. The results indicate that the chiral sample for 0.05 wt.% at the age of 7 and 28 days and 0.1 wt.% at 7 days, and the armchair sample with 0.1 wt.% at the age of 28 days have the highest compressive strength. The flexural strength at 7 and 28 days show that the chiral MWCNT composite has the greatest increase in strength for both 0.05 and 0.1%. The ranking of water absorption is chiral < zigzag < armchair < PC and armchair < chiral < zigzag < PC for 0.05 and 0.1 wt.% MWCNT at 28 days, respectively. The results, thus, show that the lowest percentage of water absorption is obtained by 0.05% chiral MWCNT-COOH and 0.1% armchair MWCNT-COOH at the age of 28 days. The effect of bridging, connecting MWCNTs and hydration products provided by MWCNTs-COOH, is, thus, confirmed by SEM.

Mechanical properties and degradation mechanism of LNG containment concrete material under cryogenic conditions

• Compressive strength and tensile strength of the concretes at cryogenic temperature were studied. • The damage degree of the concretes after cryogenic freezing-thawing cycles was investigated. • The mechanism of mechanical properties of the concretes at cryogenic temperatures was analyzed. • The degradation mechanism of damaged concrete under freezing-thawing cycles was discussed. • Application of the HCC for on all-concrete LNG storage tanks is appropriate. The mechanical properties and deterioration of concrete under cryogenic conditions are unclear. Here, high-strength and cryogenic temperature-resistant concrete (HCC) was developed for Liquefied natural gas (LNG) inner tank applications. Influences including compressive and tensile concrete strength under different temperatures (25 °C ∼ -165 °C) and freezing-thawing cycles were investigated. The results showed that lower temperatures result in higher compressive strengths, the tensile strength increases and then decreases, and the greatest increase in strength occurs at −45 °C. The tensile strength of HCC and C60 concrete decreases below −105 °C and −45 °C, respectively; more freezing-thawing cycles result in greater mechanical property degradation. Furthermore, compared to C60 concrete, HCC has a significantly lower rate of strength loss. The mechanical property mechanisms at different cryogenic temperatures and deterioration due to the freezing-thawing cycles were investigated by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). HCC is an ideal material for LNG inner tanks.

Seasonal Changes in Strength and Power in Elite Rugby League: A Systematic Review and Meta-Analysis.

The ability of a rugby league player to express high levels of strength and power is crucial for success in competition. Although researchers have shown relationships between physical attributes and performance, there is a lack of information related to changes in strength and power across various phases of the season. The purpose of this review was to identify the magnitude of change in muscular strength and power during different phases of an elite rugby league season. Percentage change and effect size were calculated to evaluate the magnitude of changes in strength and power. Meta-analyses were conducted to provide pooled estimates and 95% confidence intervals. Twelve studies were included; six reported changes following pre-season training, two during the competition phase and four examined changes over multiple seasons. Pooled estimates indicated large increases in upper and lower body strength 0.81 [0.43-1.19] and 1.35 [0.79-1.91], respectively, following pre-season training. Studies incorporating predominantly heavier loads (p 80% 1 RM) in training reported greater increases in maximal strength than studies completing lighter loads. Four studies used a wave-like programming strategy to obtain large improvements in strength and power 0.91 [0.36-1.45] and 0.90 [0.22-1.57], over multiple seasons. The results of this review highlight the limited current evidence and provides a preliminary reference point for strength and conditioning coaches aiming to develop and maintain strength and power across various stages, and over multiple seasons. Importantly, the results also indicate that higher loads result in greater increases in strength than lower loads.

Influence of the Addition of Silica Nanoparticles on the Compressive Strength of Cement Slurries under Elevated Temperature Condition

Drilling ever deeper, and thus in increasingly difficult conditions, is associated with restrictive requirements that must be met by cement slurries. This implies the need to use advanced, innovative measures that will significantly improve the performance parameters of the cement slurry and cement stone. Due to its unique properties, an admixture of nanosilica improves the properties of the cement stone and allows for appropriate zone insulation. The article presents the results of strength tests of cement stone samples with the addition of silica nanoparticles deposited in an environment of increased temperature of 90 °C. In all three cases of modification with an admixture of nanosilica (type 1, 2 and 3, concentration 0.5%, 1% and 5%), the cement stone shows an improvement in mechanical properties, which is manifested by an increase in compressive strength. The most homogeneous results of strength measurements are for cement slurries with an admixture of type 3 nanosilica (the highest average strength: 132–149% in relation to the base sample). They show the smallest stretch marks and deviations from the average. The highest average increase in strength is for the sample with the addition of 1% nanosilica (on average 124% in relation to the base sample). This amount causes the greatest increase in strength with no significant deterioration of rheological parameters.

Enhancing the performance of light-frame wood studs using glass fibre-reinforced polymers

An experimental program was undertaken to investigate the flexural performance of forty-eight unreinforced and glass fibre-reinforced polymer (GFRP) reinforced Spruce-Pine-Fir No. 2 grade individual wood studs. In general, it was found that the GFRP contributed to reducing the damage region, especially when both reinforcement and confinement were utilized. The simple tension reinforcement did not provide any significant improvement to the post-peak behaviour and resulting in a brittle failure, similar to that observed in the unreinforced studs. Other reinforcement options, particularly those consisting of U-shaped reinforcement on the tension face with and without confinement, significantly increased the average flexural strength and stiffness of the stud by a factor of 2.4 and 1.8 times those obtained in the unreinforced studs, respectively. Significant ductility ratios, in the range of 1.4–3.9, were also observed in these reinforced configurations. Weaker specimens experienced greater increases in strength and reduction in variability when reinforced. Based on these observations, six full-scale light-frame stud walls reinforced with FRP were tested dynamically under simulated blast loading. The results showed that the walls reinforced with FRP performed better and had relatively less damage while dissipating, on average, twice the energy dissipated by the unreinforced walls. The observed failure modes of the reinforced walls were consistent with the static failure modes of the individual reinforced studs.

Electromyographical Differences Between the Hyperextension and Reverse-Hyperextension.

Cuthbert, M, Ripley, NJ, Suchomel, TJ, Alejo, R, McMahon, JJ, and Comfort, P. Electromyographical differences between the hyperextension and reverse-hyperextension. J Strength Cond Res 35(6): 1477-1483, 2021-The aims of this study were to compare muscle activation of the erector spinae (ES), gluteus maximus (GMax), and biceps femoris (BF) during the hyperextension (HE) and reverse-HE (RHE) exercises. Ten subjects (age, 23 ± 4 years; height, 175.9 ± 6.9 cm; mass, 75.2 ± 9.7 kg) had electromyography (EMG) electrodes placed on the ES, GMax, and BF muscles in accordance with SENIAM (Surface EMG for Non-Invasive Assessment of Muscles) guidelines. Subjects performed 3 maximum voluntary isometric contraction trials of lumbar extension and hip extension using a handheld and isokinetic dynamometer, respectively, to normalize the EMG during the HE and RHE exercises. Three repetitions of each exercise were executed in a randomized order. High reliability (intraclass correlation coefficient ≥0.925) was observed with low variability (coefficient of variation [CV] < 10%) in all but the GMax during the extension phase of the HE (CV = 10.64%). During the extension and flexion phases, the RHE exhibited significantly greater (p ≤ 0.024; 34.1-70.7% difference) peak EMG compared with the HE in all muscles tested. Similarly, the RHE resulted in significantly greater mean EMG compared with the HE (p ≤ 0.036; 28.2-65.0% difference) in all muscles except the BF during the flexion phase (p = 9.960). Therefore, the RHE could be considered as a higher-intensity exercise for the posterior chain muscles compared with the HE, potentially eliciting greater increases in strength of the posterior chain muscles.

Comparative study on the effect of outrigger on seismic response of tall buildings with braced and Wall Core. II: Determining seismic design parameters

SummaryIn this paper, the effect of outrigger on key seismic design parameters of tall buildings with braced or shear wall core is studied. Based on the results of modal response spectrum (MRS) and nonlinear time history (NLTH) analyses of 44 models with braced or wall core, discussed in the companion paper and pushover analysis and presented in this part, the effect of outrigger and its placement level on parameters of seismic design including response modification factor R, overstrength factor Ω0, deflection amplification factor Cd, and damping ratio of structures are studied. New local measures for Cd and Ω0 are proposed based on the NLTH results. It is observed that outrigger results in greater increase in strength and stiffness of structures with wall core than buildings with braced core, but decreases the ductility of both systems. The obtained R is less than the values given by the code in most cases. For the main structures without outrigger, using the code prescribed value for Cd underestimates the real displacement of the structures with wall core and overestimates it for those with braced core. Outrigger results in increasing Cd of structures with braced core and reduction of Cd in those with wall core. The considerable variation of two proposed measures for Cd shows the inappropriateness of application of a single value of Cd for all stories. Outrigger increased the damping ratio of buildings with shear wall core considerably.

Effects of Resistance Training Performed to Failure or Not to Failure on Muscle Strength, Hypertrophy, and Power Output: A Systematic Review With Meta-Analysis.

Vieira, AF, Umpierre, D, Teodoro, JL, Lisboa, SC, Baroni, BM, Izquierdo, M, and Cadore, EL. Effects of resistance training performed to failure or not to failure on muscle strength, hypertrophy, and power output: A systematic review with meta-analysis. J Strength Cond Res 35(4): 1165-1175, 2021-The aim of this review was to summarize the evidence from longitudinal studies assessing the effects induced by resistance training (RT) performed to failure (RTF) vs. not to failure (RTNF) on muscle strength, hypertrophy, and power output in adults. Three electronic databases were searched using terms related to RTF and RTNF. Studies were eligible if they met the following criteria: randomized and nonrandomized studies comparing the effects of RTF vs. RTNF on muscle hypertrophy, maximal strength, and muscle power in adults, and RT intervention ≥6 weeks. Results were presented as standardized mean differences (SMDs) between treatments with 95% confidence intervals, and calculations were performed using random effects models. Significance was accepted when p < 0.05. Thirteen studies were included in this review. No difference was found between RTF and RTNF on maximal strength in overall analysis (SMD: -0.08; p = 0.642), but greater strength increase was observed in RTNF considering nonequalized volumes (SMD: -0.34; p = 0.048). Resistance training performed to failure showed a greater increase in muscle hypertrophy than RTNF (SMD: 0.75; p = 0.005), whereas no difference was observed considering equalized RT volumes. No difference was found between RTF and RTNF on muscle power considering overall analysis (SMD: -0.20; p = 0.239), whereas greater improvement was observed in RTNF considering nonequalized RT volumes (SMD: -0.61; p = 0.025). Resistance training not to failure may induce comparable or even greater improvements in maximal dynamic strength and power output, whereas no difference between RTF vs. RTNF is observed on muscle hypertrophy, considering equalized RT volumes.

Suction-Controlled Detachment of Mushroom-Shaped Adhesive Structures

Abstract Experimental evidence suggests that suction may play a role in the attachment strength of mushroom-tipped adhesive structures, but the system parameters which control this effect are not well established. A fracture mechanics-based model is introduced to determine the critical stress for defect propagation at the interface in the presence of trapped air. These results are compared with an experimental investigation of millimeter-scale elastomeric structures. These structures are found to exhibit a greater increase in strength due to suction than is typical in the literature, as they have a large tip diameter relative to the stalk. The model additionally provides insight into differences in expected behavior across the design space of mushroom-shaped structures. For example, the model reveals that the suction contribution is length-scale dependent. It is enhanced for larger structures due to increased volume change, and thus the attainment of lower pressures, inside of the defect. This scaling effect is shown to be less pronounced if the tip is made wider relative to the stalk. An asymptotic result is also provided in the limit that the defect is far outside of the stalk, showing that the critical stress is lower by a factor of 1/2 than the result often used in the literature to estimate the effect of suction. This discrepancy arises as the latter considers only the balance of remote stress and pressure inside the defect and neglects the influence of compressive tractions outside of the defect.

The use of nanosized additives in the modification of brick loam

The effect of nanosized additives on the strength properties of ceramics based on fusible brick loam of the Klyuchischenskoye deposit has been studied. In general, all nanosized additives selected for the study had a positive effect on the strength properties of ceramics. The greatest increase in strength, when using nanosized silica ash Laksil 30, was 70 %, in relation to the control sample. When using silica ash, an increase in the content of the amorphous phase in the shard after firing is noted against the background of a decrease in its porosity, which causes an increase in strength characteristics. The nature of the destruction of the samples also differed. The destruction of the control sample was accompanied by the formation and gradual opening of cracks. The destruction of the modified samples was more fragile in comparison with the control. Thus, the effectiveness of nanosized additives on the strength properties of ceramics is shown.

Blood Flow Restriction Training in Clinical Musculoskeletal Rehabilitation: A Critically Appraised Paper

Focused Clinical Question: Is low-load exercise training with blood flow restriction (LL-BFR) more effective at increasing muscle strength compared to low-level (LL) or high-level (HL) exercise training in individuals with muscle weakness? Clinical Bottom Line: The results of the systematic review with meta-analysis concluded that there is evidence to support the belief that LL-BFR may increase muscle strength beyond LL exercise training alone, while HL training will produce greater strength increases compared to both LL-BFR and LL training.

Upper-extremity blood flow restriction: the proximal, distal, and contralateral effects—a randomized controlled trial

Blood flow restriction (BFR) training with low weight is purported to induce similar physiological changes to high-weight regimens with the benefit of less tissue stress. We hypothesized that low-weight training with BFR would produce increased gains in strength and hypertrophy for muscle groups proximal, distal, and contralateral to tourniquet placement compared with low-weight training alone. In this prospective, randomized controlled trial, healthy subjects were randomized into a 6-week low-weight training program either with or without BFR on 1 extremity. Outcome measures included limb circumference and strength. Comparisons were made between the BFR and non-BFR extremities, BFR and control groups, and non-BFR extremity and control groups. A total of 24 subjects (14 BFR and 10 control subjects) completed the protocol. Significantly greater gains were observed in dynamometric strength both proximal (shoulder scaption [30% greater], flexion [23%], and abduction [22%]) and distal (grip strength [13%]) to the tourniquet in the BFR limb compared with both the non-BFR extremity and the control group (P < .05). Arm and forearm circumferences significantly increased in the BFR limb compared with the non-BFR limb and control group(P = .01). The non-BFR extremity demonstrated greater grip strength than the control group (9%, P < .01). No adverse events were reported. Low-weight BFR training provided a greater increase in strength and hypertrophy in the upper-extremity proximal and distal muscle groups compared with the control group. The non-BFR extremity showed a significant increase in grip strength compared with the control group, indicating a potential systemic effect.

The effects of leucine and whey protein supplementation with eight weeks of resistance training on strength and body composition.

In past few decades, supplementation has become very popular within professional and recreational athletes. Most interested among supplements are protein and amino acids. Therefore, the purpose of this study was to examine the effects of leucine supplementation in comparison to whey protein supplementation with placebo group on strength and body composition during 8 weeks of resistance training program. Thirty male college athletes (mean age±SD =23.92±1.54 years) participated in this investigation and were randomly assigned to one of three groups: whey protein (WP, N.=10), leucine (LEU, N.=10) or placebo (PLA, N.=10). The WP, LEU and PLA performed resistance training for 8 weeks. Strength (1RM bench press, squat, shoulder press) and maximum pull-ups and body composition has been assessed and data was analyzed with mixed-design analysis of variance (P≤0.01). The WP group achieved significantly greater (P≤0.01) increases in 1RM bench press than the LEU and PLA groups (+16 kg for WP; + 7.5 kg for LEU and + 5 kg for PLA). The LEU group achieved significantly greater gains (P≤0.01) in fat free mass, muscle mass and significantly decreases (P≤0.01) in fat mass compared to WP and PLA groups. Whey protein supplementation in male collegiate athletes during resistance training achieved greater increase in strength than leucine and placebo groups, and leucine group achieved significantly greater improvement in body composition than whey protein and placebo groups.

Outcomes of Reconstructive Surgery in Traumatic Brachial Plexus Injury with Concomitant Vascular Injury

To investigate functional outcome from reconstructive surgery in adult traumatic brachial plexus injury (AT-BPI) with associated vascular lesions. A retrospective review was performed of 325 patients with AT-BPI who underwent reconstructive surgery between 2001 and 2012. Patients with (vascular group) and without (control group) vascular injuries were identified by review of medical documentation. Patient presentation, characteristics of nerve and associated lesions, and surgical management were evaluated to identify prognostic variables. Postoperative muscle strength, range of motion, and patient-reported disability scores were analyzed to determine long-term outcome. Sixty-eight patients had a concomitant vascular injury. There were no significant differences in age or sex between the control and vascular groups. The vascular group was more likely to have pan-plexus lesions (P < 0.0001), with significantly more associated upper extremity injuries (P < 0.0001). The control group underwent more nerve transfers, whereas the vascular group underwent more nerve grafting (P= 0.003). Complete outcome data were obtained in 139 patients, which included 111 control (43% of all control subjects) and 28 vascular patients (41%). There was no significant difference in patient-reported disability scores between the 2 groups. However, 73% of control subjects had grade 3 or greater postoperative elbow flexion, whereas only 43% of vascular patients achieved this strength (P= 0.003). Control patients demonstrated a greater increase in strength of shoulder abduction as well (P= 0.004). Shoulder external rotation strength was grade 0 in most patients, with no difference between the 2 groups. Concomitant vascular injury leads to worse functional outcome after reconstructive surgery of traumatic brachial plexus injury.

Moderate Increase in Protein Intake Promotes a Small Additional Improvement in Functional Capacity, But Not in Muscle Strength and Lean Mass Quality, in Postmenopausal Women Following Resistance Exercise: A Randomized Clinical Trial.

The aim of this study was to evaluate the effect of a moderate increase in protein intake on muscle strength, functional capacity and lean mass quality improvements in postmenopausal women following resistance exercise. Forty-seven postmenopausal women were randomized in two groups: Normal protein (NP, n = 25), who received a dietary plan containing ~0.8 g protein·kg−1·d−1 (recommended dietary allowance—RDA recommendations); and higher protein (HP, n = 22), which a moderate increase in protein intake was recommended (~1.2 g protein·kg−1·d−1). Resistance training was performed for 10 weeks, three times/week. Muscle strength (handgrip strength and one repetition maximum test—1-RM), functional capacity and lean mass (LM) quality (muscle strength to lean mass ratio) were evaluated. Dietary intake was assessed by nine 24 h food recalls. After intervention, both groups increased similarly the leg extension 1-RM and handgrip strength. Regarding functional capacity tests, both groups increased the balance test score (SPPB) and 10 m walk test speed, with no differences between the groups. In addition, an increase in speed to perform the 6 min and 400 m walk tests was observed over the time, with an additional improvement in the HP group (time × group interaction; p = 0.007 and p = 0.004, respectively). About LM quality, leg extension 1-RM/leg LM improved over the time in both groups (p = 0.050), with no time × group interaction. All these significant changes had a low effect size. In conclusion, a moderate increase in protein intake promoted a small additional improvement in functional capacity, but it did not induce a greater increase in strength and LM quality after 10 weeks of resistance exercise in postmenopausal women. This trial was registered at ClinicalTrials.gov as NCT03024125.

B.F.R. For Proximal Benefit: Blood Flow Restriction Therapy For The Shoulder?

Blood flow restriction (BFR) therapy has been observed to improve post-operative recovery in the limbs when combined with low intensity resistance exercise (LIX). Little data exists regarding use of BFR for proximal benefit of the upper limbs (shoulders). PURPOSE: (1) Determine if rotator cuff (RC) exercises combined with BFR (BFR-Rx) promote greater increases in strength, muscular endurance, and lean mass compared to exercise alone (NoBFR-Rx); (2) Determine if BFR applied to the arm during acute LIX increases activation of RC muscles. METHODS: Eighteen healthy adults (♂11, 32±5yr, 92.3±15.2kg | ♀7, 34±7yr, 81.9±6.3kg) were recruited and randomized into 2 groups (BFR-Rx, NoBFR-Rx). Each performed 8wks of LIX (2/wk) using 4 RC exercises: cable external rotation (ER), cable internal rotation (IR), dumbbell scaption, and side-lying dumbbell ER; 20%1RM; 1set/30reps followed by 3sets/15reps (30s rest between sets, 2min rest between exercises, ^1lb resistance each week all repetitions achieved). For the BFR-Rx group, BFR was applied to using an tourniquet system (Delfi®) that maintained 50% limb occlusion pressure during each exercise with pressure released between exercises. A group x time ANCOVA (co-varied on baseline) followed by a tukey’s post hoc test was used to detect absolute & relative changes in strength (pre/post training), lean mass (pre/post training; DEXA, GE®), and achieved weekly exercise volume (sets x reps x resistance). A two-tailed paired samples t-test was used to detect differences in RC muscle activation (EMG, Delsys®) recorded during acute ER and IR fatigue tests in all subjects. Type I error was set at α=0.05. CONCLUSIONS: Combined BFR-Rx using RC exercises may yield greater increases in shoulder/arm lean mass, strength, and muscular endurance compared to exercise alone. These findings may be partially due to a greater activation of shoulder musculature while using BFR. Data collection is ongoing and will be completed prior to conference.