Levels Of Blood Flow Restriction Research Articles

Neuromuscular Responses and Perceptions of Health Status and Pain-Related Constructs in End-Stage Knee Osteoarthritis During Resistance Training With Blood Flow Restriction.

Ogrezeanu, DC, López-Bueno, L, Sanchís-Sánchez, E, Carrasco, JJ, Cuenca-Martínez, F, Suso-Martí, L, López-Bueno, R, Cruz-Montecinos, C, Martinez-Valdes, E, Casaña, J, and Calatayud, J. Neuromuscular responses and perceptions of health status and pain-related constructs in end-stage knee osteoarthritis during resistance training with blood flow restriction. J Strength Cond Res 38(4): 762-772, 2024-We aimed to evaluate the neuromuscular responses and their relationship with health status, kinesiophobia, pain catastrophizing, and chronic pain self-efficacy in patients with end-stage knee osteoarthritis during acute resistance training with different levels of blood flow restriction (BFR). Seventeen patients with end-stage knee osteoarthritis participated in 3 experimental sessions separated by 3 days, performing 4 sets of knee extensions with low load and 3 levels of concurrent BFR performed in a random order: control (no BFR), BFR at 40% arterial occlusion pressure (AOP), and BFR at 80% AOP. Normalized root-mean-square (nRMS), nRMS spatial distribution (centroid displacement, modified entropy, and coefficient of variation), and normalized median frequency (nFmed) were calculated from the vastus medialis (VM) and lateralis (VL) using high-density surface electromyography. Subjects were asked to report adverse effects after the sessions. In the VM, nRMS was higher with 80% AOP than with 40% AOP ( p = 0.008) and control ( p < 0.001), whereas there were no differences between conditions in the VL. Normalized root-mean-square also showed an association with pain catastrophizing, chronic pain self-efficacy, and health status (VM: -0.50, 0.49, -0.42; VL: -0.39, 0.27, -0.33). Spatial distribution varied between conditions but mostly in the VL. Overall, nFmed did not vary, with only a slight increase in the VL with 40% AOP, between set 3 and 4. BFR during knee extensions at 80% AOP increases VM activity and VL amplitude distribution more than 40% AOP and control. Importantly, muscle activity increases are modulated by pain catastrophizing, chronic pain self-efficacy, and health status in these patients, and kinesiophobia seems to especially modulate entropy.

Exercise-induced hypoalgesia with end-stage knee osteoarthritis during different blood flow restriction levels: sham-controlled crossover study.

blood flow restriction (BFR) training could be a valuable treatment to induce exercise-induced hypoalgesia (EIH) in patients with end-stage knee osteoarthritis. However, the use of BFR in these patients is poorly explored and there is no evidence about the training dosage needed. To evaluate the effect of resistance training protocols with different occlusion levels of blood flow restriction (BFR) on EIH in patients with end-stage knee osteoarthritis. Crossover study. University physical exercise laboratory. 26 adults with end-stage knee osteoarthritis. Patients performed 4 sets (30, 15, 15 and 15 repetitions) separated by 1-minute rests of three protocols/sessions of low-load (30% 1RM) seated knee extensions with elastic bands and BFR: placebo (sham BFR), BFR at 40% arterial occlusion pressure (AOP) and BFR at 80% AOP. Pressure Pain Thresholds (PPT) and Visual Analog Scale (VAS) collected before, immediate post session and post 10 minutes. No differences in EIH between the different levels of BFR were found. However, 80% AOP protocol worsened VAS scores immediately (Mean difference, MD (95%CI): -21.190 (-33.897 to -8.484)) while improving PPT immediately (MD (95%CI); affected limb: -.629 (-1.080 to -.177); contralateral: -.590 (-.986 to -.195)) and at 10 min (MD (95%CI); affected limb: -.633 (-1.153 to -.113); contralateral: -.676 (-1.136 to -.216); and forearm: -.467 (-.881 to -.053)) post-exercise compared to baseline. There is no EIH difference after using different occlusion levels. EIH is modulated by pain-related psychological constructs and self-perceived health status.

Acute effects of static balance exercise combined with different levels of blood flow restriction on motor performance fatigue as well as physiological and perceptual responses in young healthy males and females

PurposeThis study investigated the acute effects of a static balance exercise combined with different blood flow restriction (BFR) pressures on motor performance fatigue development and recovery as well as physiological and perceptual responses during exercise in males and females.MethodsTwenty-four recreational active males (n = 13) and females (n = 11) performed static balance exercise on a BOSU ball (3 sets of 60 s with 30 s rest in-between) on three separate (> 3 days) laboratory visits with three different BFR pressures (80% arterial occlusion pressure [AOP], 40%AOP, 30 mmHg [SHAM]) in random order. During exercise, activity of various leg muscles, vastus lateralis muscle oxygenation, and ratings of effort and pain perception were recorded. Maximal squat jump height was measured before, immediately after, 1, 2, 4, and 8 min after exercise to quantify motor performance fatigue development and recovery.ResultsQuadriceps muscle activity as well as ratings of effort and pain were highest, while muscle oxygenation was lowest in the 80%AOP compared to the 40%AOP and SHAM condition, with no differences in postural sway between conditions. Squat jump height declined after exercise with the highest reduction in the 80%AOP (− 16.4 ± 5.2%) followed by the 40%AOP (− 9.1 ± 3.2%), and SHAM condition (− 5.4 ± 3.3%). Motor performance fatigue was not different after 1 min and 2 min of recovery in 40% AOP and 80% AOP compared to SHAM, respectively.ConclusionStatic balance exercise combined with a high BFR pressure induced the largest changes in physiological and perceptual responses, without affecting balance performance. Although motor performance fatigue was increased by BFR, it may not lead to long-term impairments in maximal performance.

Effect of quadriceps training at different levels of blood flow restriction on quadriceps strength and thickness in the mid-term postoperative period after anterior cruciate ligament reconstruction: a randomized controlled external pilot study

BackgroundMore than 2 million anterior cruciate ligament (ACL) injuries occur worldwide each year. Most surgeons suggest that athletes and active persons with significant knee functional demands, including cutting motions, require and should be offered ligament reconstruction surgery. Despite concentrated rehabilitation efforts, deficits in quadriceps size and strength can persist for years after surgery. Blood flow restriction (BFR) training can help overcome disuse muscular atrophy in the mid-term postoperative period after anterior cruciate ligament reconstruction (ACLR) surgery. The purpose of this study was to evaluate the effects of quadriceps training with different levels of blood flow restriction on quadriceps strength and thickness of participants after ACLR.MethodsIn this study, 30 post-ACL reconstruction participants were randomly divided into three groups (control, 40% Arterial Occlusion Pressure [AOP] and 80% AOP groups). All patients were subjected to different levels of BFR, combined with conventional quadriceps rehabilitation, for 8 weeks. Assessments included scaled maximal isokinetic knee extension strength at 60°/s and 180°/s, the sum of the thickness of the affected femoris rectus and vastus intermedius, Y-balance test performance, and International Knee Documentation Committee questionnaire responses before and after the intervention.ResultsIn total, 23 participants completed the entire study. The 80% AOP compression group showed an increase in quadriceps femoris muscle strength and muscle thickness (p < 0.01). As compared with the control group, outcome indicators in the 40% AOP and 80% AOP group were improved (p < 0.05). After 8 weeks of experimental BFR intervention, the results were better for the 80% AOP compression group than for the 40% AOP compression group in quadriceps peak torque to body weight at 60°/s and 180°/s angular velocity, as well as the sum of the thickness of the rectus femoris and vastus intermedius.ConclusionThe combination of BFR and low-intensity quadriceps femoris training can effectively improve the muscle strength and thickness of knee extensors in participants with ACLR and help reduce the difference between the healthy and surgical sides of the knee joint while improving knee-joint function. Choosing quadriceps training with 80% AOP compression intensity could provide the most benefits. Meanwhile, BFR can accelerate the rehabilitation process of patients and allow early entry into the next rehabilitation cycle.RegistrationTrial registration Chinese Clinical Trial Registry, registration number ChiCTR2100050011, date of registration: 15/08/2021.

Acute effects of different external compression with blood flow restriction on force-velocity profile during squat and bench press exercises

The aim was to compare the acute effects of bench press (BP) and squat (SQ) exercises with blood flow restriction (BFR) (40%, 60%, 80% and 100% of the complete arterial occlusion pressure (AOP)) and without BFR (CON) on the mean propulsive (VelMED) and maximum (VelMAX) bar velocity. Fourteen healthy, physically active males (age, 23.6 ± 4.1 years; height, 1.85 ± 0.11 m; body weight 85.4 ± 4.1 kg) took part in the study. There was one set for each testing condition (CON, 40%, 60%, 80% and 100%) with 6 repetitions for BP and 6 repetitions for SQ, at 60% of 1RM, and 3 minutes of recovery between sets. The results showed statistically significant differences of the sets with 80% BFR vs. CON (mean difference [MD] = 0.035 m · s-1, p < 0.05, ES = 0.52 [1.02-0.03]) and 100% BFR sets vs. CON (MD = 0.074, p < 0.001, ES = 1.08 [1.79-0.38]) for BP. In the SQ exercise, statistically significant differences were found between 100% BFR vs. CON (DM = 0.031 m · s-1, p < 0.05), vs. 100% BFR 40% (MD = 0.04 m · s-1, p < 0.05). Trend analysis showed a statistically significant linear trend (F[1,9] = 34.9, p < 0.001, F[1,13] = 27.32, p < 0.001) for the VelMED in relation to the different levels of BFR. In conclusion, our results showed that BFR levels above ˜80% AOP (BP) and ˜100% AOP (SQ) produce a VelMED improvement at 60% 1RM.

Blood Flow Restriction Prevents The Drop In Blood Pressure Upon Head-up Tilt

Many astronauts develop orthostatic intolerance following spaceflight and this change may be more prevalent in females. Although the blood pressure response to standing should normalize in the weeks following their return to Earth, there may be emergencies where an immediate short-term solution is necessary. PURPOSE: To examine the effects of different levels of blood flow restriction on blood pressure and heart rate when a person is transitioned from supine to an upright position and determine whether this change differs based on sex. METHODS: 45 men and 44 women partook in this four-visit study. The first visit included the determination of the applied pressure for the different conditions, and familiarization with the tilt table protocol. Visits 2-4 were the experimental visits completed in a randomized order on the tilt table: 1) Sham, 2) Moderate, or 3) High pressure. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and 8 more times separated by 45 seconds. RESULTS: Data are presented as mean (SD) and as a change from the baseline measurement. Changes in systolic blood pressure were pressure dependent (High > Moderate > Sham). Notably, the application of blood flow restriction was able to prevent the drop in systolic blood pressure when moving from a supine to the head-up tilt position [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4), and Moderate vs Sham: 2.4 (8.4) mmHg]. Diastolic blood pressure increased following head-up tilt and changes were greatest with the High pressure with no differences between Moderate and Sham [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3), and Moderate vs Sham: 0.6 (5.1) mmHg]. Heart rate increased following head-up tilt and the change was initially greatest in the Sham condition [High vs Sham: -3.5 (9.1) mmHg, High vs Moderate: 0.5 (9.1), and Moderate vs Sham: -3.6 (9.3) mmHg]. However, heart rate changed the most in the High pressure condition by the end of the head-up tilt period. CONCLUSIONS: The application of blood flow restriction prevented the initial drop in blood pressure when transitioning from the supine to the upright position. This could be useful when astronauts need to exit the spacecraft quickly upon landing, where a failure to maintain blood pressure could be fatal.

The Influence on Post-Activation Potentiation Exerted by Different Degrees of Blood Flow Restriction and Multi-Levels of Activation Intensity.

(1) Background: To explore the influence on post-activation potentiation (PAP) when combining different degrees of blood flow restriction (BFR) with multi-levels of resistance training intensity of activation. (2) Purpose: To provide competitive athletes with a more efficient and feasible warm-up program. (3) Study Design: The same batch of subjects performed the vertical jump test of the warm-up procedure under different conditions, one traditional and six BFR procedures. (4) Methods: Participants performed seven counter movement jump (CMJ) tests in random order, including 90% one repetition maximum (1RM) without BFR (CON), and three levels of BFR (30%, 50%, 70%) combined with (30% and 50% 1RM) (BFR-30-30, BFR-30-50, BFR-50-30, BFR-50-50, BFR-70-30 and BFR-70-50). Jump height (H), mean power output (P), peak vertical ground reaction force (vGRF), and the mean rate of force development (RFD) were recorded and measured. (5) Results: Significantly increasing results were observed in: jump height: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4, 8 min), BFR-50-30 (8 min), BFR-50-50 (4, 8 min), BFR-70-30 (8 min), (p < 0.05); and power output: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4 min), BFR-50-30 (8 min), BFR-50-50 (4, 8 min) (p < 0.05); vGRF: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4, 8 min), BFR-50-30 (4 min), BFR-50-50 (4, 8 min) (p < 0.05); RFD: CON (8 min), BFR-30-30 (0, 4 min), BFR-30-50 (4 min), BFR-50-30 (4 min), BFR-50-50 (4 min) (p < 0.05). (5) Conclusions: low to moderate degrees of BFR procedures produced a similar PAP to traditional activation. Additionally, BFR-30-30, BFR-30-50, and BFR-50-50 were longer at PAP duration in comparison with CON.

Blood flow restriction maintains blood pressure upon head-up tilt.

Orthostatic intolerance occurs in some astronauts following space flight. Although orthostatic blood pressure responses should normalize in the weeks following the return to Earth, there may be situations where an immediate short-term solution is necessary (e.g., emergency evacuation). The purpose of this study was to examine different levels of blood flow restriction on changes in blood pressure and heart rate when transitioning from supine to a head-up tilt and determine whether this change differs based on sex. Eighty-nine participants (45 men, 44 women) completed the three visits with different pressures (Sham, Moderate, and High) in a randomized order. Cuffs were placed on the most proximal area of the thighs. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and eight more times separated by 45 seconds. Data are presented as mean (SD). The change in systolic (High > Moderate > Sham) [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4) mmHg, and Moderate vs Sham: 2.4 (8.4) mmHg] and diastolic pressure (High > Moderate = Sham) [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3) mmHg] differed across applied pressures. The change in heart rate was initially greatest in the sham-pressure but increased the greatest in the high-pressure condition by the end of the head-up tilt period. Additionally, there was no influence of sex. Blood flow restriction applied in this study increased blood pressure in a pressure-dependent manner upon head-up tilt.

Blood flow restriction with different load levels in patients with knee osteoarthritis: protocol of a randomized controlled trial

BackgroundThe effectiveness of blood flow restriction training (BFR) in elderly with knee osteoarthritis (OA) is comparable to performing high-intensity protocols (70 to 80% of 1 RM [repetition maximum]) that are known to be effective for improving the muscle strength of knee extensors, with the advantage of generating less particular rating of perceived exertion and pain immediately after training. However, despite being a promising alternative, little is known about the best way to apply the BFR, such as level of pressure and combination or not with other therapeutic modalities. The purpose of this study is to evaluate whether different levels of blood flow restriction with low load (BFR + LL) and no load (BFR + rest) are non-inferior to high-intensity resistance exercise (HIRE+BFRplacebo) for pain reduction in patients with knee OA.Methods/designThis clinical trial is a non-inferiority, five-arm, randomized, active-controlled, single trial which will be carried out in 165 patients of both sexes with knee OA, aged 50 years and older. Participants will be randomly allocated into 5 exercise groups (40% of BFR + LL; 80% of BFR + LL; 40% of BFR + rest; 80% BFR + rest, and HIRE+BFR placebo). A mixed linear model will be used to examine the effect of group-by-time interaction on pain intensity on the WOMAC subscale (primary outcome) and on disease severity, physical functional data, balance data, quality of life, global perceived effect scale, and muscle strength (secondary outcomes). Participants will be analyzed for intention-to-treat, and the statistical assessor blinded to the groups. The collection of outcomes 72 h after completion of the 16 weeks of interventions will be the primary measurement point. Follow-up secondary timepoints will be collected at 20, 28, 40, 52, and 64 weeks after the end of interventions, except for pain during the training, which will be measured immediately at the end of each session. Only the comparison of the primary outcome between the HIRE group with each BFR group will be analyzed in the non-inferiority framework, the other comparisons between the BFR groups for the primary outcome, and all secondary outcomes will be interpreted in the superiority framework.DiscussionThe results of this clinical trial can point out more clearly to ways to optimize the BFR training with the minimum of pain immediately after training, which will allow the offer of an effective and more adherent strengthening training to patients with knee OA.Trial registrationRegistro Brasileiro de Ensaios Clínicos, RBR-93rx9q. Registered on 23 July 2020. Version 1.0.

Effects of Blood Flow Restriction on O2 Muscle Extraction and O2 Pulmonary Uptake Kinetics During Heavy Exercise.

This study aimed to determine the effects of three levels of blood flow restriction (BFR) on and O2 extraction kinetics during heavy cycling exercise transitions. Twelve healthy trained males completed two bouts of 10 min heavy intensity exercise without BFR (CON), with 40% or 50% BFR (BFR40 and BFR50, respectively). and tissue saturation index (TSI) were continuously measured and modelled using multiexponential functions. The time constant of the primary phase was significantly slowed in BFR40 (26.4 ± 2.0s; p < 0.001) and BFR50 (27.1 ± 2.1s; p = 0.001) compared to CON (19.0 ± 1.1s). The amplitude of the slow component was significantly increased (p < 0.001) with BFR in a pressure-dependent manner 3.6 ± 0.7, 6.7 ± 0.9 and 9.7 ± 1.0 ml·min−1·kg−1 for CON, BFR40, and BFR50, respectively. While no acceleration of the primary component of the TSI kinetics was observed, there was an increase (p < 0.001) of the phase 3 amplitude with BFR (CON −0.8 ± 0.3% VS BFR40 −2.9 ± 0.9%, CON VS BFR50 −2.8 ± 0.8%). It may be speculated that BFR applied during cycling exercise in the heavy intensity domain shifted the working muscles to an O2 dependent situation. The acceleration of the extraction kinetics could have reached a plateau, hence not permitting compensation for the slowdown of the blood flow kinetics, and slowing kinetics.

Acute effects of physical exercise with different levels of blood flow restriction on vascular reactivity and biomarkers of muscle hypertrophy, endothelial function and oxidative stress in young and elderly subjects – A randomized controlled protocol

BackgroundGains in muscle mass and strength have been documented in exercise training with blood flow restriction (BFR). However, the impact of retrograde blood flow during BFR training on vascular health remains unclear. The present study designed a protocol to evaluate the acute effects of exercise performed with different levels of BFR on vascular reactivity and biomarkers of endothelial function, oxidative stress, and muscle hypertrophy in young and older individuals. Methods and study designSixty-eight physically inactive eutrophic men [34 young (18–25-yrs old) and 34 elderly (≥65-yrs old)] will be included in the study. Subjects will undergo three experimental protocols: a) control (ExCON) – handgrip exercise with intensity of 30% of the maximum voluntary contraction (MVC); b) blood flow restriction (ExBFR) – handgrip exercise with a resistance of 30% of the MVC with low level of BFR [80% of arterial occlusion pressure at rest (rAOP)]; and c) arterial occlusion pressure (ExAOP) – handgrip exercise with a resistance of 30% of the MVC with high level of BFR (120% of rAOP). Primary outcomes will be: a) vascular reactivity assessed by venous occlusion plethysmography; b) endothelial function (nitric oxide and apoptotic endothelial micro particles; c) oxidative stress (thiobarbituric acid reactive substances). Growth hormone and lactate concentration will be measured as secondary outcomes reflecting the hypertrophic drive and metabolic stress, respectively. DiscussionThe findings of the present study may help to elucidate the age-related impacts of BFR training on the vascular health.

Cardiac autonomic response to aerobic exercise with different levels of blood flow restriction in pre-hypertensive men

Cardiovascular safety of aerobic exercise with blood flow restriction (BFR) has been little studied in clinical populations. This study investigated the effects of different levels of BFR on cardiac autonomic response during and after walking tasks in pre-hypertensive men. Twelve pre-hypertensive men performed three randomly assigned experimental sessions: (1) 20 min of walking at 40% of peak running velocity (Vpeak) without BFR (CON); (2) 20 min of walking at 40% of Vpeak with BFR sets at 40% of the maximum cuff pressure that fully interrupted blood flow (BFR40); and (3) 20 min of walking at 40% of Vpeak with BFR sets at 80% of the maximum cuff pressure that fully interrupted blood flow (BFR80). The HR and HRV measurements were taken at rest, during exercise, and during the recovery period after constant load sessions. Heart rate was higher throughout the BFR80 session when compared to the CON condition (p 0.05). Restricting blood flow imposes additional cardiovascular stress during and after exercise in pre-hypertensive men, with apparently greater stress as the level of BFR increases.

Acute physiological and perceptual responses to moderate intensity cycling with different levels of blood flow restriction.

The aim of this study was to compare: i) the physiological and perceptual responses of low-load exercise [(moderate intensity exercise (MI)] with different levels of blood flow restriction (BFR), and ii) MI with BFR on the bike with high intensity (HI) exercise without BFR. The protocol involved large muscle mass exercise at different levels of BFR, and this differentiates our study from others. Twenty-one moderately trained males (age: 24.6 ± 2.4 years; VO2peak: 47.2 ± 7.0 ml.kg-1.min-1, mean ± sd) performed one maximal graded exercise test and seven 5-min constant-load cycling bouts. Six bouts were at MI [40% peak power (Ppeak), 60%VO2peak], one without BFR and five with different levels of BFR (40%, 50%, 60%, 70%, 80% of estimated arterial occlusion pressure). The HI bout (70%Ppeak, 90%VO2peak) was without BFR. Oxygen uptake (VO2), heart rate (HR), blood lactate (BLa), rate of perceived exertion (RPE), and tissue oxygen saturation (TSI) were recorded. Regardless of pressure, HR, BLa and RPE during MI-BFR were higher compared to MI (p < 0.05, ES: moderate to very large), and TSI reduction was greater in MI-BFR than MI (p < 0.05, ES: moderate to large). The responses of VO2, HR, BLa, RPE and TSI induced by the different levels of BFR in MI-BFR were similar. Regardless of pressure, the responses of VO2, HR, BLa and RPE induced by MI-BFR were lower than HI (p < 0.05), except for TSI. TSI change was similar between MI-BFR and HI. It appears that BFR equal to 40% of arterial occlusion pressure is sufficient to reduce TSI when exercising with a large muscle mass.

Acute Physiological Responses To Low-intensity Exercise With Different Levels Of Blood Flow Restriction

PURPOSE: External pressure is a key factor in blood flow restriction (BFR) training. Previous studies have used a limited range of occlusion pressures to compare the acute physiological and perceptual responses during leg exercise. The aim of this study was twofold: i) to compare the physiological and perceptual responses of low-intensity exercise (LI) with different levels of BFR, and ii) to compare LI with BFR on the bike with high-intensity (HI) exercise without BFR. METHODS: Twenty-one healthy, moderately-trained male (age: 24.6±2.4 yrs; VO2peak: 47.2±7.0 ml/kg/min, mean±sd) volunteered to perform one maximal graded exercise test on the bike and seven 5-min constant intensity exercise bouts on separate days and in a counterbalanced order. Six bouts were at 40% peak power (Ppeak; LI); one without BFR and five with different levels of BFR (40%, 50%, 60%, 70%, 80% of arterial occlusion pressure, LI-BFR40/50/60/70/80). Finally, they performed one HI bout (70% Ppeak) without BFR. Oxygen uptake (VO2), heart rate (HR), blood lactate (BLa), rating of perceived exertion (RPE), and tissue oxygen saturation (TSI) with near-infrared spectroscopy were recorded. RESULTS: Regardless of pressure, HR, BLa and RPE during LI-BFR were higher compared to LI (p<0.05), and TSI reduction was greater in LI-BFR (LI-BFR40/50/60/70/80: -10.6±3.1%, -10.2±4.0%, -10.1±5.1%, -10.0±4.2%, -11.3±4.9%, respectively) than LI (-6.0±4.2%, p<0.05).The responses of VO2, HR, BLa, RPE and TSI induced by the different levels of BFR applied in LI-BFR were similar. Regardless of pressure, the responses of VO2, HR, BLa and RPE induced by LI-BFR was lower than HI (p<0.05), except for TSI. TSI change was similar between LI-BFR40/50/60/70/80 and HI (LI-BFR40/50/60/70/80 range: -10.0±4.2% to -11.3±4.9%, HI: -11.5±4.5%). CONCLUSION: It appears that BFR equal to 40% of arterial occlusion pressure is sufficient to reduce TSI. This BFR level seems to stress the physiological mechanisms adequately and there is no need for higher external pressure application. This level of BFR can also produce local hypoxia similar to that during HI. Therefore, low-intensity exercise with BFR could be an alternative exercise mode for individuals who are unable to perform high-intensity exercise.

Effects Of Exercise Under Different Levels Of Blood-flow Restriction On Autonomic Modulation And Muscular Fatigue

PURPOSE: To assess the acute cardiac autonomic and peripheral muscular responses to eccentric exercise combined with different levels of blood flow restriction (BFR) in young women. METHODS: Twenty-five women (21.22±0.61 year) performed 4 sets of leg extension (30 + 15 + 15 + 15 repetitions) at 20 % one repetition maximum, with four different BFR conditions (0, 40, 60, and 80 %). Restrictive pressures were calculated based on blood-flow measurements taken at rest on each subject. Heart rate variability (HRV) and muscle fatigue were recorded at rest and during 24 hour of recovery by calculating time (RMSSD) and frequency domain (LF nu, HF nu, LF/HF) indices and analyzing muscle displacement (Dm) and contraction velocity (Vc) values, respectively. RESULTS: All parameters in CON (0%BFR) did not significant change (P>0.05). In BFR40, there was a slight reduction in RMSSD (18.51%) and HF nu (12.19%) compared to CON (P<0.05). In BFR60, RMSSD and HF nu decreased 27.91% and 13.98% while LF nu increased 13.77% compared to CON (P<0.05), and LF/HF recovered within 30min post exercise (P>0.05). In BFR80, LF nu increased 16.43% while RMSSD, HF nu, Dm and Vc dramatically declined 39.92%, 15.41%, 37.34% and 48.85% respectively when compared to CON (P<0.01), so it took longer time to restore LF/HF balance (within 24 hours). Correlation analysis showed that RMSSD was positively correlated with Dm (r = 0.65) and Vc (r = 0.62), respectively (P<0.05). while LF nu was negatively correlated with Dm (r =﹣0.57)and Vc (r =﹣0.59) (P<0.05). CONCLUSION: On the basis of low load resistance exercise, 40% BFR can withdraw vagal regulation, but sympathetic activity and sympathetic/ parasympathetic balance can be enhanced when the restriction increased to 60%BFR. Peripheral muscular fatigue can just be obviously evoked in 80% BFR, and this fatigue is highly related to cardiac autonomic modulation. Therefore, we do not recommend 80% BFR for women with cardiovascular risk.

Separate and combined effects of local and systemic hypoxia in resistance exercise.

This study quantified performance, physiological, and perceptual responses during resistance exercise to task failure with blood flow restriction (BFR), in systemic hypoxia, and with these stimuli combined. Fourteen young men were tested for 1-repetition maximum (1RM) in the barbell biceps curl and lying triceps extension exercises. On separate visits, subjects performed exercise trials (4 sets to failure at 70% 1RM with 90s between sets) in six separate randomized conditions, i.e., in normoxia or hypoxia (fraction of inspired oxygen = 20.9% and 12.9%, respectively) combined with three different levels of BFR (0%, 45%, or 60% of resting arterial occlusion pressure). Muscle activation and oxygenation were monitored via surface electromyography and near-infrared spectroscopy, respectively. Arterial oxygen saturation, heart rate, and perceptual responses were assessed following each set. Compared to set 1, the number of repetitions before failure decreased in sets 2, 3, and 4 for both exercises (all P < 0.001), independently of the condition (P > 0.065). Arterial oxygen saturation was lower with systemic hypoxia (P < 0.001), but not BFR, while heart rate did not differ between conditions (P > 0.341). Muscle oxygenation and activation during exercise trials remained unaffected by the different conditions (all P ≥ 0.206). A significant main effect of time, but not condition, was observed for overall perceived discomfort, difficulty breathing, and limb discomfort (all P < 0.001). Local and systemic hypoxic stimuli, or a combination of both, did not modify the fatigue-induced change in performance, trends of muscle activation or oxygenation, nor exercise-related sensations during a multi-set resistance exercise to task failure.

The acute effects of lower limb blood flow restriction on physiology and performance of competitive cyclists

Background: Training in conjunction with limb Blood flow restriction (BFR) is an increasingly popular method of producing increased physiological stress without the strain of high exercise loads. However little is known about the physiological responses to BFR with trained cyclists or how best to prescribe appropriate BFR training intensities. Purpose: In this study, we investigate the acute responses to different levels of BFR with trained cyclists to enable identification of specific training intensity criteria. Methods: Nine trained male cyclist (age 39.2 ± 8.1 years, height 179.1 ± 6.7 cm, weight 75.4 ± 6.7 kg, Max VO 2 4.4 ± 0.5 L.min -1 ) completed a series of tests under conditions of no BFR (N-BFR; 0mmHg), moderate BFR (M-BFR; ~40mmHg) or high BFR (H-BFR; ~80mmHg). During BFR trials restriction was applied to the proximal thighs using 11cm wide pneumatic cuffs. Testing consisted of an incremental maximal cycle test and a self-paced 3-km time-trial. Measurement of Oxygen uptake (VO 2 ), Muscle Oxygen saturation (MO 2 ) blood lactate concentration (Bla) and perceived exertion (RPE) were taken during the incremental test along with performance data from the time trial.  Physiological responses from the three trials were examined across a range of comparable power outputs and at pre-determined blood lactate concentrations of 2 and 4 Mmol. Results: At comparable power outputs, heart rate and RPE was significantly higher (p>0.05) in the H-BFR condition compared to all other conditions. However, there were no significant differences between conditions in VO 2 and MO 2 at equivalent powers. Compared to the N-BFR condition power output was lower by ~9% and ~21 % in the M-BFR and H-BFR condition respectively (fig 1) for fixed blood lactate concentration of 2 and 4mMol. Discussion: Using moderate and high levels of BFR during cycling exercise leads to substantial reductions (left shift) in power output at fixed blood lactate values. The reduced power was associated with increases in heart rate and RPE, at equivalent power outputs. However, measures of O 2 and MO 2 were not significantly different at comparable exercise intensities between the conditions. Conclusions: the decrease in attainable power output in BFR conditions appears predominately due to an increased reliance on anaerobic metabolism and an elevation in blood lactate concentration. Cardiovascular O2 delivery and extraction does not appear to be significantly affected by BFR. Â

Vascular and oxygenation responses of local ischemia and systemic hypoxia during arm cycling repeated sprints

ObjectivesThe purpose of this study was to investigate the acute vascular and oxygenation responses to repeated sprint exercise during arm cycling with either blood flow restriction (BFR) or systemic hypoxia alone or in combination. DesignThe study design was a single-blinded repeated-measures assessment of four conditions with two levels of normobaric hypoxia (400 m and 3800 m) and two levels of BFR (0% and 45% of total occlusion). MethodsSixteen active participants (eleven men and five women; mean ± SD; 26.4 ± 4.0 years old; 73.8 ± 9.8 kg; 1.79 ± 0.07 m) completed 5 sessions (1 familiarization, 4 conditions). During each test visit, participants performed a repeated sprint arm cycling test to exhaustion (10 s maximal sprints with 20 s recovery until exhaustion) to measure power output, metabolic equivalents, blood flow, as well as oxygenation (near-infrared spectroscopy) of the biceps brachii muscle tissue. ResultsRepeated sprint performance was decreased with both BFR and systemic hypoxia conditions. Greater changes between minimum-maximum of sprints in total hemoglobin concentration (Δ[tHb]) were demonstrated with BFR (400 m, 45% and 3800 m, 45%) than without (400 m, 0% and 3800 m, 0%) (p < 0.001 for both). Additionally, delta tissue saturation index (ΔTSI) decreased more with both BFR conditions than without (p < 0.001 for both). The absolute maximum TSI was progressively reduced with both BFR and systemic hypoxia (p < 0.001). ConclusionsBy combining high-intensity, repeated sprint exercise with BFR and/or systemic hypoxia, there is a robust stimulus detected by increased changes in blood perfusion placed on specific vascular mechanisms, which were more prominent in BFR conditions.

High-pressure blood flow restriction with very low load resistance training results in peripheral vascular adaptations similar to heavy resistance training

Objective: To investigate vascular adaptations to eight weeks of resistance exercise, with and without different pressures of blood flow restriction (BFR), in the upper and lower body. Approach: Forty individuals (men = 20, women = 20) completed eight weeks of resistance exercise at very low loads (15% of one-repetition maximum (1RM)), with two levels of BFR (40% arterial occlusion pressure (AOP), 80% AOP), without BFR, and 70% of 1RM. Vascular conductance and venous compliance were measured via plethysmography before and following training in the forearms and in the calves. Main results: Values reported as means (95% confidence intervals). Pre to post changes in vascular conductance occurred only in the high-pressure conditions (upper body: +8.29 (3.01–13.57) ml · mmHg−1; lower body: +7.86 (3.37–12.35) ml · mmHg−1) and high-load conditions (upper body: +8.60 (3.45–13.74) ml · mmHg−1); lower body: +7.20 (2.71–11.69) ml · mmHg−1) only. In the upper body, the change was significantly greater in the high-pressure and high-load conditions compared to the change observed in the low-pressure condition (−0.41 (−5.56, 4.73) ml · mmHg−1). These changes were not greater than the change observed in the low-load condition without pressure (+1.81 (−3.47, 7.09) ml · mmHg−1). In the lower body, the change in the high-pressure and high-load conditions were significantly greater than the changes observed with low-load training with (−0.86 (−5.60, 3.87) ml · mmHg−1) and without (−1.22 (−5.71, 3.27) ml · mmHg−1) a low pressure. Venous compliance increased in all groups in the upper body (+0.003 (.000 08, 0.006) ml · 100 ml−1 · mmHg−1) only, with no changes in the lower body. Significance: High-pressure BFR causes adaptations in vascular function following eight weeks of training at mechanical loads not typically associated with such adaptations.

Effects of Different Percentages of Blood Flow Restriction on Energy Expenditure.

The study aimed to analyze the effect of different levels of blood flow restriction (BFR) on energy expenditure (EE) and subjective perceptions of discomfort (SPD) during aerobic exercises. A sample group of 24 young men was required to walk on a treadmill for 14 min at 40% of their maximum speed, with 4 different percentages of BFR (0, 50, 80 and 100%) applied in the lower limbs (LL) once a week with a 7-day interval between the 4 evaluations. EE data were collected during the exercise periods; SPD data were collected after the exercises. There was a significant increase in EE at 50, 80 and 100% BFR compared to the condition without BFR, and between 50 and 100% BFR; however, there were no differences between 50 and 80% and 80 and 100% BFR. Discomfort showed a significant increase according to the increase in BFR. During the walking exercises with BFR, the EE strongly increased until 50% of BFR; after this level the additional increases slowed. It can be concluded that when performing aerobic exercises with BFR, there is no need to use BFR levels above 50% to reach satisfying level of EE with only a moderate level of discomfort to the practitioner. This study was registered in the Brazilian Registry of Clinical Trials (REBEC) under number RBR-3XHSJX.