Inflammation marker, damage marker and anabolic hormone responses to resistance training with vascular restriction in older males

Systematic review and meta-analysis of the effects of blood flow restriction training on bone health in older adults

While low-intensity blood flow restriction (LI-BFR) training has recently been shown to improve bone health, there remains limited evidence regarding its impact on older adults. This meta-analysis aimed to quantitatively identify the effects of LI-BFR training on bone mineral density (BMD) and bone biomarkers compared with conventional resistance training programs. Studies were identified through searches of four databases: PubMed, Scopus, SPORTDiscus, and Web of Science. R packages were utilized for this meta-analysis. The results indicated that compared to low-intensity (LI) training, LI-BFR significantly increased BMD (ES = 0.25, 95% Confidence Interval [CI]: [0.08, 0.41], p < 0.01), osteotropic hormones (i.e., GH, ES = 1.18, 95%CI: [0.66, 1.70]), p < 0.001; IGF-1, ES = 0.89, 95% CI: [0.44, 1.33], p < 0.001), but resulted in a smaller increase in bone resorption markers (i.e., CTX, ES = -0.77, 95%CI: [-1.16, -0.37], p < 0.001). LI-BFR training demonstrated similar effects on BMD improvement as high-intensity (HI) resistance training (ES = -0.1, 95%CI: [-0.66, 0.41], p = 0.64). Furthermore, sex and training frequency moderated the secretion of osteotropic hormones (male vs. female: IGF-1, 0.51 vs. 1.64, p < 0.01; ≤ 3 times per week vs. > 3 times per week: GH, 1.62 vs. 0.68, p < 0.01, and IGF-1, 1.13 vs. 0.39, p < 0.05). In conclusion, LI-BFR training shows promise for enhancing bone health in older adults, offering benefits comparable to HI training.

Synthesis and Anti-Inflammatory and Analgesic Potentials of Ethyl 2-(2,5-Dioxo-1-Phenylpyrrolidin-3-yl)-2-Methylpropanoate

Background/Objectives: Inflammation and analgesia are two prominent symptoms and often lead to chronic medical conditions. To control inflammation and analgesia, many marketed drugs are in practice but the majority of them have severe side effects. Methods: This study involved the synthesis of a pivalate-based Michael product and evaluated it for in vitro COX-1, COX-2, and 5-LOX inhibitory potentials using specific assays. Molecular docking studies were also assessed. Based on the in vitro results, the compound was also subjected to in vivo anti-inflammatory and antinociceptive studies. Results: The pivalate-based Michael product (MAK01) was synthesized by an organocatalytic asymmetric Michael addition of ethyl isobutyrate to N-phenylmaleimide with an isolated yield of 96%. The structure of the compound was confirmed through 1H and 13C NMR analyses. The observed IC50 values for COX-1, COX-2, and 5-LOX were 314, 130, and 105 μg/mL, respectively. The molecular docking studies on the synthesized compound showed binding interactions with the minimized pockets of the respective enzymes. In a carrageenan model, a percent reduction in edema when administered at 10 mg/kg (a reduction of 33.3 ± 0.77% at the second hour), 20 mg/kg (a reduction of 34.7 ± 0.74% at the second hour), and 30 mg/kg (a reduction of 40.58% ± 0.84% after the fifth hour) was observed. The compound showed a significant response at concentrations of 50, 100, and 150 mg/kg with latency times of 10.32 ± 0.82, 12.16 ± 0.51, and 12.93 ± 0.45 s, respectively. Conclusion: In this study, we synthesized a pivalate-based Michael product for the first time. Moreover, based on its rationality and potency, it was found to be an effective future medicine for the management of analgesia and inflammation.

Effect of resistance training on inflammatory markers in middle-aged and older adults: A meta-analysis

BACKGROUND AND OBJECTIVE

A meta-analysis was conducted to evaluate the impact of resistance training on pro-inflammatory cytokines c-reactive protein (CRP), interleukin 6 (IL 6), and tumor necrosis factor- α (TNF- α) in middle-aged and elderly individuals.

METHODS

The retrieval period for the Web of Science and other large electronic databases is set by default to March 2022. Both included and excluded researchers are independent examination literature on the impact of resistance exercise on markers of inflammation in the elderly. The physical medical care Evidence Database scale (Physical Therapy Evidence Database, PEDro) was used to evaluate the research quality, and Revmen 5.3 was used to end the index analysis.

RESULTS

After a total of four rounds of elimination, 12 items were eventually included. The total sample size for the research was 388 persons. Resistance training substantially reduced CRP levels in middle-aged and older individuals, with SMD = -0.56 and 95 % confidence interval ([-0.78, -0.34], P < 0.00001, correspondingly. Resistance training can successfully lower IL6 concentrations in middle-aged and older adults, although the combined impact is not substantial. SMD = -0.25, 95 % CI [-0.54, 0.04]; P = 0.09. TNF- concentrations did not alter significantly following resistance exercise in middle-aged and older adults. The overall effect was SMD = -0.07, with a 95 % confidence interval [-0.37, 0.23], while P = 0.64.

CONCLUSION

Resistance training reduces CRP, IL6, and TNF-α levels among middle-aged and elderly people. However, it has no significant anti-inflammatory effects on TNF-α. Resistance exercise at a moderate level for 3 times / week with a duration of 6-12 weeks or 16-32 weeks, significantly reduced CRP levels. This work contributing to exploring the resistance training program for the elderly to reduce inflammatory markers, and further, providing suggestions for the elderly to participate in resistance training and reduce the concentration of inflammatory markers.

Blood Flow Restriction Resistance Training in Tendon Rehabilitation: A Scoping Review on Intervention Parameters, Physiological Effects, and Outcomes

Objective

To identify current evidence on blood flow restriction training (BFRT) in tendon injuries and healthy tendons, evaluating physiological tendon effects, intervention parameters, and outcomes.

Methods

This scoping review was reported in accordance with the PRISMA Extension for Scoping Reviews (PRISMA-ScR). Databases searched included MEDLINE, CINAHL, AMED, EMBase, SPORTDiscus, Cochrane library (Controlled trials, Systematic reviews), and five trial registries. Two independent reviewers screened studies at title/abstract and full text. Following screening, data was extracted and charted, and presented as figures and tables alongside a narrative synthesis. Any study design conducted on adults, investigating the effects of BFRT on healthy tendons or tendon pathology were included. Data were extracted on physiological tendon effects, intervention parameters and outcomes with BFRT.

Results

Thirteen studies were included, three on tendinopathy, two on tendon ruptures, and eight on healthy Achilles, patellar, and supraspinatus tendons. A variety of outcomes were assessed, including pain, function, strength, and tendon morphological and mechanical properties, particularly changes in tendon thickness. BFRT intervention parameters were heterogeneously prescribed.

Conclusion

Despite a dearth of studies to date on the effects of BFRT on healthy tendons and in tendon pathologies, preliminary evidence for beneficial effects of BFRT on tendons and clinical outcomes is encouraging. As BFRT is a relatively novel method, definitive conclusions, and recommendations on BFRT in tendon rehabilitation cannot be made at present, which should be addressed in future research, due to the potential therapeutic benefits highlighted in this review.

Acute and Chronic Bone Marker and Endocrine Responses to Resistance Exercise With and Without Blood Flow Restriction in Young Men

In this study, we compared acute and chronic bone marker and hormone responses to 6 weeks of low intensity (20% 1RM) blood flow restriction (BFR20) resistance training to high intensity (70% 1RM) traditional resistance training (TR70) and moderate intensity (45% 1RM) traditional resistance training (TR45) in young men (18–35 years). Participants were randomized to one of the training groups or to a control group (CON). The following training programs were performed 3 days per week for 6 weeks for knee extension and knee flexion exercises: BFR20, 20%1RM, 4 sets (30, 15, 15, 15 reps) wearing blood flow restriction cuffs around the proximal thighs; TR70, 70% 1RM 3 sets 10 reps; and TR45, 45% 1RM 3 sets 15 reps. Muscle strength and thigh cross-sectional area were assessed at baseline, between week 3 and 6 of training. Acute bone marker (Bone ALP, CTX-I) and hormone (testosterone, IGF-1, IGFBP-3, cortisol) responses were assessed at weeks 1 and 6, with blood collection done in the morning after an overnight fast. The main findings were that the acute bone formation marker (Bone ALP) showed significant changes for TR70 and BFR20 but there was no difference between weeks 1 and 6. TR70 had acute increases in testosterone, IGF-1, and IGFBP-3 (weeks 1 and 6). BFR20 had significant acute increases in testosterone (weeks 1 and 6) and in IGF-1 at week 6, while TR45 had significant acute increases in testosterone (week 1), IGF-1 (week 6), and IGFBP-3 (week 6). Strength and muscle size gains were similar for the training groups. In conclusion, low intensity BFR resistance training was effective for stimulating acute bone formation marker and hormone responses, although TR70 showed the more consistent hormone responses than the other training groups.

Dose- and Intensity-Response Associations Between Leisure-Time Physical Activity and Markers of Inflammation and Oxidative Stress in Older Adults

This study aimed to investigate the dose- and intensity-response associations between leisure-time physical activity (LTPA) and markers of inflammation and oxidative stress in older adults. Multivariable linear regression was performed to evaluate the associations among 3,559 older adults in 2015-2018 National Health and Nutrition Examination Survey. LTPA was negatively associated with inflammatory markers including C-reactive protein, segmented neutrophil count and alkaline phosphatase, and positively associated with one marker of antioxidants albumin in older adults. Compared with vigorous LTPA, moderate LTPA could provide more benefits through further decreasing white blood cell count and alkaline phosphatase, and increasing serum bilirubin and albumin. The effects of LTPA on C-reactive protein and albumin were more significant in participants with chronic diseases including diabetes, hypertension, and cancer. In conclusion, this study demonstrates the dose- and intensity-response effects of LTPA on inflammation and oxidative stress and provides exercise prescription recommendations for older adults.

The Evolution of Blood Flow Restricted Exercise

The use of blood flow restricted (BFR) exercise has become an accepted alternative approach to improve skeletal muscle mass and function and improve cardiovascular function in individuals that are not able to or do not wish to use traditional exercise protocols that rely on heavy loads and high training volumes. BFR exercise involves the reduction of blood flow to working skeletal muscle by applying a flexible cuff to the most proximal portions of a person’s arms or legs that results in decreased arterial flow to the exercising muscle and occluded venous return back to the central circulation. Safety concerns, especially related to the cardiovascular system, have not been consistently reported with a few exceptions; however, most researchers agree that BFR exercise can be a relatively safe technique for most people that are free from serious cardiovascular disease, as well as those with coronary artery disease, and also for people suffering from chronic conditions, such as multiple sclerosis, Parkinson’s, and osteoarthritis. Potential mechanisms to explain the benefits of BFR exercise are still mostly speculative and may require more invasive studies or the use of animal models to fully explore mechanisms of adaptation. The setting of absolute resistive pressures has evolved, from being based on an individual’s systolic blood pressure to a relative measure that is based on various percentages of the pressures needed to totally occlude blood flow in the exercising limb. However, since several other issues remain unresolved, such as the actual external loads used in combination with BFR, the type of cuff used to induce the blood flow restriction, and whether the restriction is continuous or intermittent, this paper will attempt to address these additional concerns.

Comparison of skeletal muscle ultrastructural changes between normal and blood flow-restricted resistance exercise: A case report

NEW FINDINGS

What is the main observation in this case? The main observation of this case report is that blood flow-restricted exercise can cause myofibrils to have an aberrant wave-like appearance that is accompanied by irregular pockets of sarcoplasm in the intermyofibrillar space, while traditional forms of damage to the Z-discs and contractile elements are not as apparent. What insights does it reveal? Our findings indicate that blood flow restriction-mediated fluid pooling might cause alterations in skeletal muscle ultrastructure after exercise that might be directly related to myofibre swelling.

ABSTRACT

The acute effects of blood flow-restricted (BFR) exercise training on skeletal muscle ultrastructure are poorly understood owing to inconsistent findings and the use of largely imprecise systemic markers for indications of muscle damage. The purpose of this study was to compare myofibrillar ultrastructure before and 30 min after normal and BFR resistance exercise using transmission electron microscopy in a single individual to evaluate the feasibility of this more nuanced approach. One apparently healthy male with 13 years of resistance exercise completed six sets of both BFR [30% of one-repetition maximum (1-RM)] and normal non-occluded (70% of 1-RM) unilateral angled leg press on the contralateral leg, as a control, after assessment of 1-RM 72 h before. Vastus lateralis muscle biopsies were collected before and 30 min after each exercise session. The lengths and widths of 250 sarcomeres and the sarcoplasmic area were assessed via 20 individual transmission electron photomicrographs. Analysis revealed that BFR training (1.769 ± 0.12 μm) increased sarcomere length when compared with normal exercise (1.64 ± 0.17 μm; P < 0.001), without differences in sarcomere width between conditions (BFR, 0.90 ± 0.26 μm; normal, 0.93 ± 0.27 μm; P = 0.172). Furthermore, there were no significant interaction (P = 0.168) or condition effects between BFR (25.98 ± 4.17%) and normal (27.3 ± 6.49%) resistance exercise for sarcoplasmic area (P = 0.229). Exercise also increased sarcoplasmic area within the myofibril (pre-exercise, 24.42 ± 5.13%; postexercise, 28.95 ± 5.92%) for both conditions (P = 0.001). This case study demonstrates a unique BFR training-induced alteration in myofibril ultrastructure that appeared wave like and was accompanied by intracellular abnormalities that appeared to be fluid pockets of sarcoplasm disrupting the surrounding myofibrils.

The Systemic Effects of Blood Flow Restriction Training: A Systematic Review

BACKGROUND

Blood flow restriction (BFR) training has been reported to have significant benefits on local skeletal muscle including increasing local muscle mass, strength, and endurance while exercising with lower resistance. As a result, patients unable to perform traditional resistance training may benefit from this technique. However, it is unclear what effects BFR may have on other body systems, such as the cardiovascular and pulmonary systems. It is important to explore the systemic effects of BFR training to ensure it is safe for use in physical therapy.

PURPOSE

The purpose of this study was to systematically review the systemic effects of blood flow restriction training when combined with exercise intervention.

STUDY DESIGN

Systematic review.

METHODS

Three literature searches were performed: June 2019, September 2019, and January 2020; using MedLine, ScienceDirect, PubMed, Cochrane Reviews and CINAHL Complete. Inclusion criteria included: at least one outcome measure addressing a cardiovascular, endocrinological, systemic or proximal musculoskeletal, or psychosocial outcome, use of clinically available blood flow restriction equipment, use of either resistance or aerobic training in combination with BFR, and use of quantitative measures. Exclusion criteria for articles included only measuring local or distal musculoskeletal changes due to BFR training, examining only passive BFR or ischemic preconditioning, articles not originating from a scholarly peer-reviewed journal, CEBM level of evidence less than two, or PEDro score less than four. Articles included in this review were analyzed with the CEBM levels of evidence hierarchy and PEDro scale.

RESULTS

Thirty-five articles were included in the review. PEDro scores ranged between 4 and 8, and had CEBM levels of evidence of 1 and 2. Common systems studied included cardiovascular, musculoskeletal, endocrine, and psychosocial. This review found positive or neutral effects of blood flow restriction training on cardiovascular, endocrinological, musculoskeletal, and psychosocial outcomes.

CONCLUSIONS

Although BFR prescription parameters and exercise interventions varied, the majority of included articles reported BFR training to produce favorable or non-detrimental effects to the cardiovascular, endocrine, and musculoskeletal systems. This review also found mixed effects on psychosocial outcomes when using BFR. Additionally, this review found no detrimental outcomes directly attributed to blood flow restriction training on the test subjects or outcomes tested. Thus, BFR training may be an effective intervention for patient populations that are unable to perform traditional exercise training with positive effects other than traditional distal muscle hypertrophy and strength and without significant drawbacks to the individual.

LEVEL OF EVIDENCE

1b.

Effect of resistance training with blood flow restriction on muscle damage markers in adults: A systematic review

Background

The purpose of this review was to systematically analyze the evidence regarding the occurrence of muscle damage (changes in muscle damage markers) after resistance training with blood flow restriction sessions.

Materials and methods

This systematic review was conducted in accordance with the PRISMA recommendations. Two researchers independently and blindly searched the following electronic databases: PubMed, Scopus, Web of Science, CINAHL, LILACS and SPORTdicus. Randomized and non-randomized clinical trials which analyzed the effect of resistance training with blood flow restriction on muscle damage markers in humans were included. The risk of bias assessment was performed by two blinded and independent researchers using the RoB2 tool.

Results

A total of 21 studies involving 352 healthy participants (men, n = 301; women, n = 51) were eligible for this review. The samples in 66.6% of the studies (n = 14) were composed of untrained individuals. All included studies analyzed muscle damage using indirect markers. Most studies had more than one muscle damage marker and Delayed Onset Muscle Soreness was the measure most frequently used. The results for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions were contrasting, and the use of a pre-defined repetition scheme versus muscle failure seems to be the determining point for this divergence, mainly in untrained individuals.

Conclusions

In summary, the use of sets until failure is seen to be determinant for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions, especially in individuals not used to resistance exercise.

Trial registration

Register number: PROSPERO number: CRD42020177119.

Physical activity, dietary protein and insulin-like growth factor 1: Cross-sectional analysis utilising UK Biobank

BACKGROUND

Insulin-like growth factor-I (IGF-1) is an anabolic hormone that stimulates cell growth and division. The effects of IGF-1 may be beneficial (muscle growth/repair) or detrimental (increased risk of several types of cancer and mortality) for health. Dietary protein and physical activity are thought to be factors that modulate IGF-1.

OBJECTIVE

This study analysed the relationships dietary protein vs IGF-1 and physical activity vs IGF-1 independently with a large sample size, and determined if/how physical activity affected the association between dietary protein and IGF-1 in healthy adults.

METHODS

Regression models were used to assess the association between dietary protein and/or physical activity on serum IGF-1 in a cross-sectional sample of 60,677 healthy adults that were enrolled in the UK Biobank project.

RESULTS

Dietary protein was positively associated with IGF-1 (0.030 nmol/L;95%CI 0.027-0.033;p < 0.001). Individuals undertaking 10-50 excess MET h/week of physical activity had 0.129 nmol/L greater IGF-1 than participants completing less than 10 excess MET h/week (95%CI 0.028-0.230). The "high" category of physical activity (>50 excess MET h/week) was not correlated with IGF-1 (-0.055 nmol/L;95%CI -0.185-0.076). When dietary protein and physical activity were included in the same model, physical activity did not change the relationship between dietary protein and IGF-1, nor visa-versa.

CONCLUSIONS

The positive association between dietary protein and IGF-1 was not influenced by physical activity. The former association was stronger than the latter. Thus, when seeking to adjust IGF-1 for possible health concerns, regulating dietary protein may be more pertinent than physical activity as a primary intervention.

Local and Systemic Effects of Blood Flow Restriction Therapy in an Animal Model

BACKGROUND

Blood flow restriction therapy (BFRT) has been increasingly applied to improve athletic performance and injury recovery. Validation of BFRT has lagged behind commercialization, and currently the mechanism by which this therapy acts is unknown. BFRT is one type of ischemic therapy, which involves exercising with blood flow restriction. Repetitive restriction of muscle blood flow (RRMBF) is another ischemic therapy type, which does not include exercise.

HYPOTHESIS/PURPOSE

The purpose was to develop a rat model of ischemic therapy, characterize changes to muscle contractility, and evaluate local and systemic biochemical and histologic responses of 2 ischemic therapy types. We hypothesized that ischemic therapy would improve muscle mass and strength as compared with the control group.

STUDY DESIGN

Controlled laboratory study.

METHODS

Four groups of 10 Sprague-Dawley rats were established: control, stimulation, RRMBF, and BFRT. One hindlimb of each subject underwent 8 treatment sessions over 4 weeks. To simulate exercise, the stimulation group underwent peroneal nerve stimulation for 2 minutes. The RRMBF group used a pneumatic cuff inflated to 100 mm Hg with a 48-minute protocol. The BFRT group involved 100-mm Hg pneumatic cuff inflation and peroneal nerve stimulation for a 5-minute protocol. Four methods of evaluation were performed: in vivo contractility testing, histology, immunohistochemistry, and ELISA. Analysis of variance with post hoc Tukey test and linear mixed effects modeling were used to compare the treatment groups.

RESULTS

There was no difference in muscle mass among groups (P = .40) or between hindlimbs (P = .73). In vivo contractility testing showed no difference in maximum contractile force among groups (P = .64) or between hindlimbs (P = .30). On histology, myocyte cross-sectional area was not different among groups (P = .55) or between hindlimbs (P = .44). Pax7 immunohistochemistry demonstrated no difference in muscle satellite cell density among groups (P = .06) or between hindlimbs (P = .046). ELISA demonstrated the RRMBF group as eliciting elevated GH levels as compared with the other groups (P < .001).

CONCLUSION

Ischemic therapy did not induce gains in muscle mass, contractility strength, fiber cross-sectional area, or satellite cell density locally or systemically in this model, although the RRMBF group did have elevated GH levels on ELISA.

CLINICAL RELEVANCE

This animal model does not support ischemic therapy as a method to improve muscle mass, function, or satellite cell density.

Ischemic Therapy in Musculoskeletal Medicine

BACKGROUND

The competitive environment of athletics has promoted the exploration of any technology application that may offer an edge with performance and recovery from injury. Ischemic therapy is one such technology that has rapidly been incorporated into training rooms and physical therapy clinics worldwide. This therapy modality is reported to increase an athlete's ability to improve muscle mass, strength, and endurance.

PURPOSE

To provide the sports medicine physician with an understanding of the current state of ischemic therapy technology, including treatment specifications, known physiological effects, hypothesized mechanisms, biochemical effects, athletic applications, medical applications, animal models, and future research recommendations.

STUDY DESIGN

Literature review.

METHODS

A computer-based search of the PubMed database was used to perform a comprehensive literature review on musculoskeletal ischemic therapy.

RESULTS

The current research on ischemic therapy is largely composed of case series with varying equipment, methods, and therapy specifications. The publication of case series has value in identifying this technology for future research, but the results of these studies should not be justification for application to athletes without validation of safety and effectiveness.

CONCLUSION

To date, ischemic therapy remains unvalidated, and the mechanism by which it improves muscle performance is not clear.

Does Blood Flow Restriction Therapy in Patients Older Than Age 50 Result in Muscle Hypertrophy, Increased Strength, or Greater Physical Function? A Systematic Review

BACKGROUND

Blood flow restriction (BFR) is a process of using inflatable cuffs to create vascular occlusion within a limb during exercise. The technique can stimulate muscle hypertrophy and improve physical function; however, most of these studies have enrolled healthy, young men with a focus on athletic performance. Furthermore, much of the information on BFR comes from studies with small samples sizes, limited follow-up time, and varied research designs resulting in greater design, selection, and sampling bias. Despite these limitations, BFR's popularity is increasing as a clinical rehabilitation tool for aging patients. It is important for practitioners to have a clear understanding of the reported effects of BFR specifically in older adults while simultaneously critically evaluating the available literature before deciding to employ the technique.

QUESTIONS/PURPOSES

(1) Does BFR induce skeletal muscle hypertrophy in adults older than 50 years of age? (2) Does BFR improve muscle strength and/or physical function in adults older than 50 years?

METHODS

Using PubMed, Google Scholar, Web of Science, and Science Direct, we conducted a systematic review of articles using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to assess the reported effects of BFR on skeletal muscle in older adults. Included articles enrolled participants 50 years of age or older and used BFR in conjunction with exercise to study the effects of BFR on musculoskeletal outcomes and functionality. The following search terms were used: "blood flow restriction" OR "KAATSU" OR "ischemic training" AND "clinical" AND "elderly." After duplicates were removed, 1574 articles were reviewed for eligibility, and 30 articles were retained with interventions duration ranging from cross-sectional to 16 weeks. Sample sizes ranged from 6 to 56 participants, and exercise tasks included passive mobilization or electrical stimulation; walking; resistance training using machines, free weights, body weight, or elastic bands; and water-based activities. Furthermore, healthy participants and those with cardiovascular disease, osteoarthritis, osteoporosis, sporadic inclusion body myositis, spinal cord injuries, and current coma patients were studied. Lastly, retained articles were assigned a risk of bias score using aspects of the Risk of Bias in Nonrandomized Studies of Interventions and the Cochrane Collaboration's tool for assessing the risk of bias in randomized trials.

RESULTS

BFR, in combination with a variety of exercises, was found to result in muscle hypertrophy as measured by muscle cross-sectional area, thickness, volume, mass, or circumference. Effect sizes for BFR's ability to induce muscle hypertrophy were calculated for 16 of the 30 papers and averaged 0.75. BFR was also shown to improve muscle strength and functional performance. Effect sizes were calculated for 21 of the 30 papers averaging 1.15.

CONCLUSIONS

Available evidence suggests BFR may demonstrate utility in aiding rehabilitation efforts in adults older than 50 years of age, especially for inducing muscle hypertrophy, combating muscle atrophy, increasing muscle strength, and improving muscle function. However, most studies in this systematic review were at moderate or high risk of bias; that being so, the findings in this systematic review should be confirmed, ideally using greater sample sizes, randomization of participants, and extended follow-up durations.

LEVEL OF EVIDENCE

Level II, systematic review.

Blood flow restriction impairs the inflammatory adaptations of strength training in overweight men: a clinical randomized trial

The aim of this study was to evaluate the impact of high-intensity strength training (ST) or low-intensity strength training with blood flow restriction (ST-BFR) on monocyte subsets, the expression of C-C chemokine receptor 5 (CCR5), and CD16 on monocytes, and tumor necrosis factor alpha (TNF-α) production of overweight men. Thirty overweight men were randomly assigned to conventional ST or ST-BFR. Both groups performed exercises of knee extension and biceps curl with equal volume (3 sessions/week) over 8 weeks, and the peripheral frequency of monocytes (CD14+CD16-, classical monocytes; CD14+CD16+, intermediate monocytes; CD14-CD16+, nonclassical monocytes), the mean fluorescence intensity (MFI) of CCR5 and CD16 on CD14+ monocytes; and the production of TNF-α by lipopolysaccharide (LPS)-stimulated cells were quantified. Eight weeks of ST increased the frequency of CD14+CD16- monocytes (p = 0.04) and reduced the percentage of CD14-CD16+ (p = 0.02) and the production of TNF-α by LPS-stimulated cells (p = 0.03). The MFI of CD16 on CD14+ monocytes decreased after the ST intervention (p = 0.02). No difference in monocyte subsets, CCR5 or CD16 expression, and TNF-α production were identified after ST-BFR intervention (p > 0.05). The adoption of ST promotes anti-inflammatory effects on monocyte subsets of overweight men, but this effect was lost when BFR was adopted. Novelty High-intensity strength training reduces the production of TNF-α and the peripheral frequency of CD16+ monocytes in overweight men. Blood flow restriction method blunts the strength training adaptations on monocyte subsets and pro-inflammatory TNF-α production in overweight men.

Immune System Modulation in Response to Strength Training With Blood Flow Restriction

Souza, TSP, Pfeiffer, PAS, Pereira, JN, Pereira Neto, EA, Dutra, TS, Mendonça, MGL, and Cirilo-Sousa, MS. Immune system modulation in response to strength training with blood flow restriction. J Strength Cond Res XX(X): 000-000, 2019-This study aimed to compare the strength training with blood flow restriction (ST-BFR) to the multiple-set training at different intensities (30% of 1RM and 75% of 1RM) as for their effect on immunoinflammatory responses (total leukocytes, segmented neutrophils, lymphocytes, monocytes, and lymphocyte subpopulations). It is a randomized experimental study with a repeated measures design with inter and intragroup effects of a strength training session. Eighteen physically active adults aged 20-31 years (26.17 ± 3.7 years), apparently healthy, performed a strength training session with 2 exercises. Six milliliters of blood were collected before the training, immediately after the training, and at 30 minutes and 24 hours after the session to carry out the analyses. The results showed that the strength training could promote modulation (time effect) in the leukocyte count (F = 25.86, p < 0.01, η = 0.74), regardless of the method used. Neutrophils (F = 22.71, p < 0.01, η = 0.60), specifically the TCD4+ lymphocytes (F = 6.33, p < 0.05, η = 0, 3), were the main factors responsible for this variation. Despite the similarity, there were differences between the methods in the modulations of total leukocytes (F = 4.16, p < 0.05, η = 0.36) and neutrophils (F = 4.80, p < 0.05, η = 0.39). In conclusion, compared to the multiple-set training, ST-BFR produces immunoinflammatory responses similar to the low-intensity training and different from the high-intensity training. However, the demargination process of some cells was different depending on the method and intensity used. Nevertheless, these variations are compatible with an appropriate recovery process, because the amplitude and length of the modulation curves of leukocytes, and lymphocyte subpopulations were not compatible with immunosuppression.

The Effects of Restriction Pressures on the Acute Responses to Blood Flow Restriction Exercise

Purpose

No current guidelines or recommendations exist informing the selection of restriction pressure during blood flow restriction exercise (BFRE). Moreover, the effects of specific relative restriction pressures on the acute muscle, metabolic and cardiopulmonary responses to BFRE are unclear. The purpose of this study was to characterize these acute responses at different levels of restriction pressure.

Methods

Participants (n = 10) completed rhythmic isometric knee extension exercise across five experimental trials in a balanced randomized order. Three were BFRE trials {B-40 [restriction pressure set to 40% LOP (total limb occlusion pressure)]; B-60 (60% LOP); and B-80 (80% LOP)} with a workload equivalent to 20% maximal voluntary force (MVC), one was non-BFRE at 20% MVC (LL) and one was non-BFRE at 80% MVC (HL). Measurements recorded were torque, muscle activity via electromyography (EMG), tissue oxygenation via near infrared spectroscopy, whole body oxygen consumption, blood lactate and heart rate.

Results

For the LL and B-40 trials, most measures remained constant. However, for the B-60 and B-80 trials, significant fatigue was demonstrated by a reduction in MVC torque across the trial (p < 0.05). Blood lactate increased from baseline in HL, B-60, and B-80 (p < 0.05). Submaximal EMG was greater in B-60 and B-80 than LL, but lower compared with HL (p < 0.05). Tissue oxygenation decreased in HL, B-40, B-60, and B-80 (p < 0.05), which was lower in the B-80 trial compared to all other trials (p < 0.01). Whole body oxygen consumption was not different between the BFRE trials (p > 0.05).

Conclusion

We demonstrate graded/progressive acute responses with increasing applied pressure during BFRE, from which we speculate that an effective minimum “threshold” around 60% LOP may be necessary for BFRE to be effective with training. While these data provide some insight on the possible mechanisms by which BFRE develops skeletal muscle size and strength when undertaken chronically across a training program, the outcomes of chronic training programs using different levels of applied restriction pressures remain to be tested. Overall, the present study recommends 60–80% LOP as a suitable “minimum” BFRE pressure.

Blood Flow Restriction Resistance Exercise Improves Muscle Strength and Hemodynamics, but Not Vascular Function in Coronary Artery Disease Patients: A Pilot Randomized Controlled Trial

Resistance training may be associated with unfavorable cardiovascular responses (such as hemodynamic alterations, anginal symptoms or ventricular arrhythmias). In healthy adults, blood flow-restricted (BFR) resistance training improves muscle strength and hypertrophy improvements at lower loads with minimal systemic cardiovascular adverse responses. The aim of this study was to assess the safety and efficacy of BFR resistance training in patients with coronary artery disease (CAD) compared to usual care. Patients with stable CAD were randomized to either 8 weeks of supervised biweekly BFR resistance training (30-40% 1RM unilateral knee extension) or usual exercise routine. At baseline and after 8 weeks, patients underwent 1-RM knee extension tests, ultrasonographic appraisal of vastus lateralis (VL) muscle diameter and of systemic (brachial artery) flow-mediated dilation, and determination of markers of inflammation (CD40 ligand and tumor necrosis factor alfa), and fasting glucose and insulin levels for homeostatic model assessment (HOMA). A total of 24 patients [12 per group, mean age 60 ± 2 years, 6 (25%) women] were included. No training-related adverse events were recorded. At baseline groups significantly differ in age (mean difference: 8.7 years, p < 0.001), systolic blood pressure (mean difference: 12.17 mmHg, p = 0.024) and in metabolic control [insulin (p = 0.014) and HOMA IR (p = 0.014)]. BFR-resistance training significantly increased muscle strength (1-RM, +8.96 kg, p < 0.001), and decreased systolic blood pressure (-6.77 mmHg; p = 0.030), whereas VL diameter (+0.09 cm, p = 0.096), brachial artery flow-mediated vasodilation (+1.55%; p = 0.079) and insulin sensitivity (HOMA IR change of 1.15, p = 0.079) did not improve significantly. Blood flow restricted resistance training is safe and associated with significant improvements in muscle strength, and may be therefore provided as an additional exercise option to aerobic exercise to improve skeletal muscle functioning in patients with CAD. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03087292.

Blood Flow Restriction During Futsal Training Increases Muscle Activation and Strength

The aim of this study was to investigate the effect of leg blood flow restriction (BFR) applied during a 3-a-side futsal game on strength-related parameters. Twelve male futsal players were randomly assigned into two groups (n = 6 for each group) during 10 training sessions either with or without leg BFR. Prior to and post-training sessions, participants completed a series of tests to assess anabolic hormones and leg strength. Pneumatic cuffs were initially inflated to 110% of leg systolic blood pressure and further increased by 10% after every two completed sessions. In comparison with baseline, the resting post-training levels of myostatin (p = 0.002) and IGF-1/MSTN ratio (p = 0.006) in the BFR group changed, whereas no change in the acute level of IGF-1 and myostatin after exercise was observed. Peak torque of knee extension and flexion increased in both groups (p < 0.05). A trend of increased neural activation of all heads of the quadriceps was observed in both groups, however, it was statistically significant only for rectus femoris in BFR (p = 0.02). These findings indicated that the addition of BFR to normal futsal training might induce greater neuromuscular benefits by increasing muscle activation and augmenting the hormonal response.

Microvascularization is not a limiting factor for exercise in adults with cerebral palsy

Muscle contractures are a common complication in patients with central nervous system (CNS) lesions which limit range of movement and cause joint deformities. Furthermore, it has previously been shown that muscles with contractures have a reduced number of capillaries, indicating decreased tissue vascularization. The aim of the present study was to investigate the microvascular volume (MV) at rest and after acute exercise in the muscle tissue of individuals with cerebral palsy (CP) and healthy control individuals. Contrast-enhanced ultrasound (CEUS) was used before and after 30 min of walking or running on a treadmill in 10 healthy control participants and 10 individuals with CP to detect MV of their skeletal muscle tissue. A significant increase in the MV was observed after exercise both in the adult CP group (21–53 yr) and in the control group (21–52 yr) (1.8 ± 0.8 ΔdB to 3.1 ± 0.9 ΔdB or 42.9% and 1.5 ± 0.6 ΔdB to 2.5 ± 0.9 ΔdB or 39.0%, respectively). Furthermore, a difference in the resting MV was observed between the most severe cases of CP [gross motor function classification scale (GMFCS) 3 and 4] (2.3 ± 0.5 ΔdB) and the less severe cases (GMFCS 1 and 2) (1.5 ± 0.2 ΔdB). When the CP group was walking (3.4 km/h), the lactate levels, Borg score, and heart rate matched the level of controls when they were running (9.8 km/h). In conclusion, individuals with CP become exhausted at much lower exercise intensities than healthy individuals. This is not explained by impaired microvascularization, since the MV of the individuals with CP respond normally to increased O2 demand during acute exercise.

NEW & NOTEWORTHY Cerebral palsy (CP) patients were less physically active compared with typically developed individuals. This may affect the microvascularization. We observed that the CP group became exhausted at much lower exercise intensities compared with healthy individuals. However, impaired microvascularization was not the reason for the decreased physical activity as the CP group responded normally to increased O2 demand during acute exercise. These results indicate that walking may be recommended as an intervention to train and maintain skeletal muscle tissue in individuals with CP.

Effect of resistance training on inflammatory markers of older adults: A meta-analysis

INTRODUCTION

Low-grade inflammation is associated with several deleterious health outcomes and may aggravate sarcopenia and dynapenia during aging. A strategy to alleviate these conditions is resistance training (RT). Thus, the aim was to critically examine the effects of regular RT on inflammatory markers of older adults from previous studies.

METHODS

The search was conducted on MEDLINE, July 2017. Only randomized controlled trials (RCTs) testing RT effects on C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) and/or interleukin-6 (IL-6) of adults over 50 years-of-age were selected by two independent reviewers.

RESULTS

The main meta-analyses showed RT reduced CRP in older adults (standard mean difference [SMD] = -0.61, 95%CI = -0.83; -0.31, p < 0.001), tended to reduce IL-6 (SMD = -0.19, 95%CI = -0.42; 0.02, p = 0.07) and did not change TNF-α. Further exploratory sub-group analyses showed a potential association of muscle mass for both CRP and TNF-α changes. Reductions in CRP and TNF-α only occurred in RCTs performing a higher number of exercises (>8), higher weekly frequency (3 times/week) and longer durations than 12 weeks.

CONCLUSIONS

Anti-inflammatory effects of RT were significant only for CRP with a tendency for a decrease in IL-6 as well. The exploratory analyses suggested the reduction in inflammatory markers could be dependent on increases in muscle mass and higher volume of RT protocols. These potential mediators of RT anti-inflammatory effects should be addressed in future meta-analyses to clarify the effects of RT on inflammatory markers of older adults with very specific conditions and larger numbers of studies.

Delayed Onset Muscle Soreness and Perceived Exertion After Blood Flow Restriction Exercise

Brandner, CR, and Warmington, SA. Delayed onset muscle soreness and perceived exertion after blood flow restriction exercise. J Strength Cond Res 31(11): 3101-3108, 2017-The purpose of this study was to determine the perceptual responses to resistance exercise with heavy loads (80% 1 repetition maximum [1RM]), light loads (20% 1RM), or light loads in combination with blood flow restriction (BFR). Despite the use of light loads, it has been suggested that the adoption of BFR resistance exercise may be limited because of increases in delayed onset muscle soreness (DOMS) and perceived exertion. Seventeen healthy untrained males participated in this balanced, randomized cross-over study. After 4 sets of elbow-flexion exercise, participants reported ratings of perceived exertion (RPE), with DOMS also recorded for 7 days after each trial. Delayed onset muscle soreness was significantly greater for low-pressure continuous BFR (until 48 hours postexercise) and high-pressure intermittent BFR (until 72 hours postexercise) than for traditional heavy-load resistance exercise and light-load resistance exercise. In addition, RPE was higher for heavy-load resistance exercise and high-pressure intermittent BFR than for low-pressure continuous BFR, with all trials greater than light-load resistance exercise. For practitioners working with untrained participants, this study provides evidence to suggest that to minimize the perception of effort and postexercise muscle soreness associated with BFR resistance exercise, continuous low-pressure application may be more preferential than intermittent high-pressure application. Importantly, these perceptual responses are relatively short-lived (∼2 days) and have previously been shown to subside after a few exercise sessions. Combined with smaller initial training volumes (set × repetitions), this may limit RPE and DOMS to strengthen uptake and adherence and assist in program progression for muscle hypertrophy and gains in strength.

Tribulus terrestris extracts alleviate muscle damage and promote anaerobic performance of trained male boxers and its mechanisms: Roles of androgen, IGF-1, and IGF binding protein-3

PURPOSE

To investigate the effects of Tribulus terrestris (TT) extracts on muscle mass, muscle damage, and anaerobic performances of trained male boxers and its mechanisms: roles of plasma androgen, insulin growth factor 1 (IGF-1), and IGF-1 binding protein-3 (IGFBP-3).

METHODS

Fifteen male boxers were divided into exercise group (E, n = 7) and exercise plus TT group (E + TT, n = 8). The 2 groups both undertook 3-week high-intensity and 3-week high-volume trainings separated by a 4-week rest. TT extracts (1250 mg/day) were orally administered by boxers in E + TT group. TT extract compositions were detected by UHPLC-Q-TOF/MS. Before and at the end of the 2 trainings, muscle mass, anaerobic performance, and blood indicators were explored.

RESULTS

Compared with E group, decreases of plasma CK (1591.5 ± 909.6 U/L vs. 2719.9 ± 832.5 U/L) and IGFBP-3 (3075.5 ± 1072.5 ng/mL vs. 3950.8 ± 479.3 ng/mL) as well as increases of mean power (MP, 459.4 ± 122.3 W vs. 434.6 ± 69.5 W) and MP/body weight (MP/BW, 7.5 ± 0.9 W/kg vs. 7.1 ± 1.1 W/kg) were detected in E + TT group after a high-intensity training. For high-volume training, reduction of IGFBP-3 (2946.4 ± 974.1 ng/mL vs. 3632.7 ± 470.1 ng/mL) and increases of MP (508.7 ± 103.2 W vs. 477.8 ± 49.9 W) and MP/BW (8.2 ± 0.3 W/kg vs. 7.5 ± 0.9 W/kg) were detected in E + TT group, compared with E group. Muscle mass, blood levels of testosterone, dihydrotestosterone (DHT), and IGF-1 were not signifiantly changed between the 2 groups.

CONCLUSION

Taking 1250 mg capsules containing TT extracts did not change muscle mass and plasma levels of testosterone, DHT, and IGF-1 but significantly alleviated muscle damage and promoted anaerobic performance of trained male boxers, which may be related to the decrease of plasma IGFBP-3 rather than androgen in plasma.

Blood flow restricted training leads to myocellular macrophage infiltration and upregulation of heat shock proteins, but no apparent muscle damage

KEY POINTS

Muscular contractions performed using a combination of low external loads and partial restriction of limb blood flow appear to induce substantial gains in muscle strength and muscle mass. This exercise regime may initially induce muscular stress and damage; however, the effects of a period of blood flow restricted training on these parameters remain largely unknown. The present study shows that short-term, high-frequency, low-load muscle training performed with partial blood flow restriction does not induce significant muscular damage. However, signs of myocellular stress and inflammation that were observed in the early phase of training and after the training intervention, respectively, may be facilitating the previously reported gains in myogenic satellite cell content and muscle hypertrophy. The present results improve our current knowledge about the physiological effects of low-load muscular contractions performed under blood flow restriction and may provide important information of relevance for future therapeutic treatment of muscular atrophy.

ABSTRACT

Previous studies indicate that low-load muscle contractions performed under local blood flow restriction (BFR) may initially induce muscle damage and stress. However, whether these factors are evoked with longitudinal BFR training remains unexplored at the myocellular level. Two distinct study protocols were conducted, covering 3 weeks (3 wk) or one week (1 wk). Subjects performed BFR exercise (100 mmHg, 20% 1RM) to concentric failure (BFRE) (3 wk/1 wk), while controls performed work-matched (LLE) (3 wk) or high-load (HLE; 70% 1RM) (1 wk) free-flow exercise. Muscle biopsies (3 wk) were obtained at baseline (Pre), 8 days into the intervention (Mid8), and 3 and 10 days after training cessation (Post3, Post10) to examine macrophage (M1/M2) content as well as heat shock protein (HSP27/70) and tenascin-C expression. Blood samples (1 wk) were collected before and after (0.1-24 h) the first and last training session to examine markers of muscle damage (creatine kinase), oxidative stress (total antibody capacity, glutathione) and inflammation (monocyte chemotactic protein-1, interleukin-6, tumour necrosis factor α). M1-macrophage content increased 108-165% with BFRE and LLE at Post3 (P < 0.05), while M2-macrophages increased (163%) with BFRE only (P < 0.01). Membrane and intracellular HSP27 expression increased 60-132% at Mid8 with BFRE (P < 0.05-0.01). No or only minor changes were observed in circulating markers of muscle damage, oxidative stress and inflammation. The amplitude, timing and localization of the above changes indicate that only limited muscle damage was evoked with BFRE. This study is the first to show that a period of high-frequency, low-load BFR training does not appear to induce general myocellular damage. However, signs of tissue inflammation and focal myocellular membrane stress and/or reorganization were observed that may be involved in the adaptation processes evoked by BFR muscle exercise.

Effects of resistance training at different loads on inflammatory markers in young adults

PURPOSE

Suppressing inflammaging at an early stage in life via exercise might prevent chronic diseases later in life. The aim was to investigate the influence of resistance training at different external loads on inflammatory markers in healthy young adults.

METHODS

Serum was collected for basal levels of cytokines (IL-1beta, IL-6, IL-8, sTNFR1, IL-1RA, IL-10 and GM-CSF) before and after 9 weeks exercise from 36 young (22 ± 2 years) healthy subjects who were randomized to three times weekly supervised resistance training at either HI_max (n = 12, 1 × 10-12 repetitions at 80% 1RM), LO (n = 12, 1 × 10-12 repetitions at 40% 1RM), or LO_max (n = 12, 1 × 10-12 repetitions at 40% 1RM preceded by 60 repetitions at 20-25% 1RM) respectively.

RESULTS

Overall, IL-8 increased (p < 0.001) and IL-6 decreased (p = 0.001) after training, but no significant time*group interaction was found (respectively, p = 0.283 and p = 0.058 for IL-8 and IL-6). When analyzed separately, IL-8 increased significantly in HI_max (p = 0.022) and LO_max (p = 0.024); and IL-6 decreased significantly in LO_max (p = 0.009) and LO (p = 0.013). No significant overall time effect was observed for sTNFR1 and IL-1RA; however, in HI_max sTNFR1 (p = 0.031) and IL-1RA (p = 0.014) increased significantly, but remained unchanged in LO_max and LO. IL-1beta, IL-10 and GM-CSF levels remained undetectable in most participants.

CONCLUSIONS

Nine weeks of resistance training-irrespective of the external load-have beneficial effects on circulating IL-8 and IL-6. In addition, training at high external load increases the anti-inflammatory cytokines sTNFR1 and IL-1RA. The results of this study show that resistance training has anti-inflammatory effects in healthy young persons and that the response of the different inflammatory mediators depends on the magnitude of the external load.

Efficacy of Blood Flow-Restricted Low-Load Resistance Training For Quadriceps Strengthening in Men at Risk of Symptomatic Knee Osteoarthritis

Background:

Greater quadriceps strength has been associated with lower risk of symptomatic knee osteoarthritis (OA) in older adults. However, factors that confer elevated risk of knee OA (eg, sedentary lifestyle, obesity, and knee injury) also contribute to a reduced tolerance of resistance training programs at ≥60% 1-repetition maximum (1RM). Therefore, the current study assessed whether concurrent application of blood flow restriction (BFR) to low-load resistance training is an efficacious and tolerable means of improving quadriceps strength in men at risk of symptomatic knee OA.

Methods:

Men older than age 45, with a history of knee injury or elevated body mass index (BMI), were randomized to low-load resistance training (30% 1RM) either with or without concurrent BFR. Isotonic double-leg press strength and isokinetic knee extensor strength were assessed before and after 4 weeks of training 3 times/wk. Knee pain (Knee Osteoarthritis Outcome Score) was assessed for tolerance.

Results:

Of the 42 men (mean age 56.1 ± 7.7 years) who were randomized, 41 completed the program. There were no significant intergroup differences in age, BMI, knee pathology, or muscle strength at baseline. Although leg press 1RM improved in both control and BFR groups, there were no significant intergroup differences in primary or secondary measures of muscle strength. The BFR was not associated with worsening of knee pain, but there was a significant improvement in knee pain in the control group.

Conclusions:

In comparison with training without BFR, addition of BFR to 30% 1RM resistance training for 4 weeks did not confer significantly greater increases in leg press or quadriceps strength in older men with risk factors for symptomatic knee OA.

Dose-and gender-specific effects of resistance training on circulating levels of brain derived neurotrophic factor (BDNF) in community-dwelling older adults

BACKGROUND

BDNF is known to induce neuroplasticity and low circulating levels have been related to neuronal loss in older persons. Physical exercise is thought to trigger BDNF-induced neuroplasticity, but conflicting observations have been reported regarding the effects of resistance training on circulating BDNF in the elderly. These conflicting observations might reflect dose-and gender-specific differences.

METHOD

Fifty-six apparently healthy elderly (68 ± 5 years) participants were randomized to 12 weeks of resistance training (3×/week) at either high-resistance (HIGH, 8 Males, 10 Females, 2 × 10-15 repetitions at 80% 1 RM), low-resistance (LOW, 9 Males, 10 Females, 1 × 80-100 repetitions at 20% 1 RM), or mixed low-resistance (LOW+, 9 Males, 10 Females, 1 × 60 repetitions at 20% 1 RM followed by 1 × 10-20 repetitions at 40% 1 RM). Serum was collected for BDNF assay at baseline and after 12 weeks (24 h-48 h after the last training).

RESULTS

12 weeks of LOW+ exercise significantly increased BDNF levels in male (from 34.9 ± 10.7 ng/mL to 42.9 ± 11.9 ng/mL, time × group interaction p=0.013), but not in female participants. No significant change was observed in HIGH or LOW, neither in male nor female subjects.

CONCLUSION

Our results show that only the mixed-low-resistance training program with a very high number of repetitions at a sufficiently high external resistance was able to increase circulating BDNF in older male participants. Training to volitional fatigue might be necessary to obtain optimal results. Additional studies are needed to unravel the underlying mechanisms, as well as to confirm the observed gender difference.

The effects of resistance exercise with and without different degrees of blood-flow restriction on perceptual responses

The aim was to compare exercise with and without different degrees of blood-flow restriction on perceived exertion (RPE) and discomfort. Participants were assigned to Experiment 1, 2, or 3. Each completed protocols differing by pressure, load, and/or volume. RPE and discomfort were taken before and after each set. For pressure and RPE, the 20% one repetition maximum (1RM) blood-flow restriction conditions were affected by increasing the pressure from 40% to 50% blood-flow restriction (~12 vs. ~14). This did not appear to happen within the 30% 1RM blood-flow restriction conditions or the higher pressures in the 20% 1RM conditions. The similar RPE between 20% and 30% 1RM to failure was expected given both were to failure. For discomfort, ratings were primarily affected by load at the lowest pressure. Increasing pressure to 50% blood-flow restriction increased discomfort at 20% 1RM (~2.6 vs. ~4). There was a further increase when increasing to 60% blood-flow restriction (~4 vs. ~4.8). The high-load condition had the lowest discomfort, while ratings were highest with 20% 1RM to failure. In conclusion, exercise with blood-flow restriction does not appear to augment the perceptual response observed with low-load exercise to failure.