Different Levels Of Blood Flow Restriction Research Articles

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.

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.

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.

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

Acute effects of exercise under different levels of blood-flow restriction on muscle activation and fatigue.

There is some evidence that muscular activation during exercise is enhanced by higher levels of blood flow restriction (BFR). However, the impact of different relative levels of BFR on the acute neuromuscular response to resistance exercise is not yet fully understood. We examined the acute effects of low-intensity knee extensions [20% of 1-repetition maximum (1RM)] with BFR on muscle activation, neuromuscular fatigue and torque in the rectus femoris (RF) and vastus medialis (VM) muscles. Fourteen men (24.8±5.4 years) exercised at 20% 1RM combined with 40, 60 and 80% BFR. Restrictive pressures were calculated based on direct blood-flow measurements taken at rest on each participant. Torque was determined during pre- and post-exercise maximal voluntary contractions. Surface electromyographic activity [root mean square (RMS)] was obtained during dynamic and sustained isometric contractions before and after exercise. The median frequency (MF) of the electromyographic power spectrum was computed for isometric contractions. Torque only decreased in the 80% BFR condition (-5.2%; p<0.01). Except for the VM in the 40% BFR, MF decreased in both muscles post-exercise in all conditions (p<0.01). MF decrements were of greater magnitude post-exercise at higher levels of BFR. RMS increased within all sets in both muscles (p<0.01) and attained higher values in the 80% BFR condition; except for set 1 in the RF muscle (p<0.01). Muscular activation, as well as neuromuscular fatigue, varies as a function of relative BFR intensity. Therefore, the individual determination of vascular restriction levels is crucial before engaging in BFR exercise.