Continuous Blood Flow Restriction Research Articles

Effect of continuous and intermittent blood flow restriction deep-squat training on thigh muscle activation and fatigue levels in male handball players

We aimed to investigate acute changes before and after low-intensity continuous and intermittent blood flow restriction (BFR) deep-squat training on thigh muscle activation characteristics and fatigue level under suitable individual arterial occlusion pressure (AOP). Twelve elite male handball players were recruited. Continuous (Program 1) and intermittent (Program 2) BFR deep-squat training was performed with 30% one-repetition maximum load. Program 1 did not include decompression during the intervals, while Program 2 contained decompression during each interval. Electromyography (EMG) was performed before and after two BFR training programs in each period. EMG signals of the quadriceps femoris, posterior femoral muscles, and gluteus maximus, including the root mean square (RMS) and normalized RMS and median frequency (MF) values of each muscle group under maximum voluntary contraction (MVC), before and after training were calculated. The RMS value under MVC (RMSMVC) of the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), and gluteus maximus (GM) decreased after continuous and intermittent BFR training programs, and those of the biceps femoris (BF) and semitendinosus (SEM) increased; The RMS standard values of the VL, BF, and SEM were significantly increased after continuous and intermittent BFR training (P < 0.05), The RMS value of GM significantly decreased after cuff inflating (P < 0.05). The MF values of RF, VM, VL, and GM decreased significantly after continuous BFR training (P < 0.05). Continuous BFR deep-squat training applied at 50% AOP was more effective than the intermittent BFR training program. Continuous application of BFR induces greater levels of acute fatigue than intermittent BFR that may translate into greater muscular training adaptations over time.

Acute effect of different blood flow restriction protocols on muscle damage

The aim of this study is to examine the acute effect of different blood flow restriction (BFR) protocols on muscle damage. Thirty (age 19.77±1.30 years) healthy young men were included in the study. Participants were randomly divided into three groups: Experiment 1 (continuous BFR+ barbell squat, n=10), Experiment 2 (intermittent BFR + barbell squat, n=10), and Control (only barbell squats without BFR, n=10). In 80% of their 1RMs, they performed barbell squat exercises for a total of six sets, with two repetitions in each set and a 3-minute rest interval between sets. For markers of muscle damage creatine kinase (CK), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alanine transaminase (ALT), blood was drawn from the individuals twice before and immediately after the exercise. Analysis of variance in repeated measures (Repeated Measures ANOVA) test was used to analyze the data. In statistical analysis, the level of significance was accepted as p

Muscle Fatigue Is Attenuated When Applying Intermittent Compared With Continuous Blood Flow Restriction During Endurance Cycling.

The aim of this study was to identify a blood-flow-restriction (BFR) endurance exercise protocol that maximizes metabolic strain and minimizes muscle fatigue. Twelve healthy participants accomplished 5 different interval cycling endurance exercises (2-min work, 1-min rest) in a randomized order: (1)control, low intensity with unrestricted blood flow (CON30); (2)low intensity with intermittent BFR (i-BFR30, ∼150mm Hg); (3)low intensity with continuous BFR (c-BFR, ∼100mm Hg); (4)unloaded cycling with i-BFR0 (∼150 mm Hg); and (5)high intensity (HI) with unrestricted blood flow. Force production, creatine kinase activity, antioxidant markers, blood pH, and potassium (K+) were measured in a range of 5 minutes before and after each cycling exercise protocol. HI showed the highest reduction (Δ = -0.26 [0.05], d = 5.6) on blood pH. Delta pH for c-BRF30 (Δ = -0.02 [0.03], d = 0.8) and ΔpH for i-BRF30 (Δ = -0.04 [0.03], d = 1.6) were different from each other, and both were higher compared with CON30 (Δ = 0.03 [0.03]). There was significant before-to-after force loss following HI (Δ = 55 [40]N·m-1, d = 1.5) and c-BFR30 (Δ = 27 [21]N·m-1, d = 0.7) protocols only, which were accompanied by significant increases in K+ (HI: Δ = 0.94 [0.65]mmol·L-1, d = 1.8; c-BFR30: Δ = 0.72 [0.85]mmol·L-1, d = 1.2). Moreover, all BFR conditions elicited slight increases in plasma creatine kinase, but not for HI and CON30. Glutathione changes from before to after were significant for all BFR conditions and HI, but not for CON30. The attenuation in fatigue-induced reductions in maximal force suggests that i-BFR exercise could be preferable to c-BFR in improving exercise capacity, with considerably less biologic stress elicited from HI exercises.

Acute Effects of Different Blood Flow Restriction Protocols on Bar Velocity During the Squat Exercise.

The main goal of the present study was to evaluate the effects of different blood flow restriction (BFR) protocols (continuous and intermittent) on peak bar velocity (PV) and mean bar velocity (MV) during the squat exercise at progressive loads, from 40 to 90% 1RM. Eleven healthy men (age = 23.4 ± 3.1 years; body mass = 88.5 ± 12.1 kg; squat 1RM = 183.2 ± 30.7 kg; resistance training experience, 5.7 ± 3.6 years) performed experimental sessions once a week for 3 weeks in random and counterbalanced order: without BFR (NO-BFR), with intermittent BFR (I-BFR), and with continuous BFR (C-BFR). During the experimental session, the participants performed six sets of the barbell squat exercise with loads from 40 to 90% 1RM. In each set, they performed two repetitions. During the C-BFR session, the cuffs were maintained throughout the training session. During the I-BFR, the cuffs were used only during the exercise and released for each rest interval. The BFR pressure was set to ∼80% arterial occlusion pressure (AOP). Analyses of variance showed a statistically significant interaction for MV (p < 0.02; η2 = 0.18). However, the post hoc analysis did not show significant differences between particular conditions for particular loads. There was no significant condition × load interaction for PV (p = 0.16; η2 = 0.13). Furthermore, there were no main effects for conditions in MV (p = 0.38; η2 = 0.09) as well as in PV (p = 0.94; η2 = 0.01). The results indicate that the different BFR protocols used during lower body resistance exercises did not reduce peak bar velocity and mean bar velocity during the squat exercise performed with various loads.

Similar Morphological and Functional Training Adaptations Occur Between Continuous and Intermittent Blood Flow Restriction.

Davids, CJ, Raastad, T, James, L, Gajanand, T, Smith, E, Connick, M, McGorm, H, Keating, S, Coombes, JS, Peake, JM, and Roberts, LA. Similar morphological and functional training adaptations occur between continuous and intermittent blood flow restriction. J Strength Cond Res 35(7): 1784-1793, 2021-The aim of the study was to compare skeletal muscle morphological and functional outcomes after low-load resistance training using 2 differing blood flow restriction (BFR) protocols. Recreationally active men and women (n = 42 [f = 21], 24.4 ± 4.4 years) completed 21 sessions over 7 weeks of load-matched and volume-matched low-load resistance training (30% 1 repetition maximum [1RM]) with either (a) no BFR (CON), (b) continuous BFR (BFR-C, 60% arterial occlusion pressure [AOP]), or (c) intermittent BFR (BFR-I, 60% AOP). Muscle mass was assessed using peripheral quantitative computed tomography before and after training. Muscular strength, endurance, and power were determined before and after training by assessing isokinetic dynamometry, 1RM, and jump performance. Ratings of pain and effort were taken in the first and final training session. An alpha level of p < 0.05 was used to determine significance. There were no between-group differences for any of the morphological or functional variables. The muscle cross sectional area (CSA) increased pre-post training (p = 0.009; CON: 1.6%, BFR-C: 1.1%, BFR-I: 2.2%). Maximal isometric strength increased pre-post training (p < 0.001; CON: 9.6%, BFR-C: 14.3%, BFR-I: 19.3%). Total work performed during an isokinetic endurance task increased pre-post training (p < 0.001, CON: 3.6%, BFR-C: 9.6%, BFR-I: 11.3%). Perceptions of pain (p = 0.026) and effort (p = 0.033) during exercise were higher with BFR-C; however, these reduced with training (p = 0.005-0.034). Overall, these data suggest that when 30% 1RM loads are used with a frequency of 3 times per week, the addition of BFR does not confer superior morphological or functional adaptations in recreationally active individuals. Furthermore, the additional metabolic stress that is proposed to occur with a continuous BFR protocol does not seem to translate into proportionally greater training adaptations. The current findings promote the use of both intermittent BFR and low-load resistance training without BFR as suitable alternative training methods to continuous BFR. These approaches may be practically applicable for those less tolerable to pain and discomfort associated with ischemia during exercise.

Variations in Muscle Activity and Exerted Torque During Temporary Blood Flow Restriction in Healthy Individuals.

Recent studies suggest that transitory blood flow restriction (BFR) may improve the outcomes of training from anatomical (hypertrophy) and neural control perspectives. Whilst the chronic consequences of BFR on local metabolism and tissue adaptation have been extensively investigated, its acute effects on motor control are not yet fully understood. In this study, we compared the neuromechanical effects of continuous BFR against non-restricted circulation (atmospheric pressure—AP), during isometric elbow flexions. BFR was achieved applying external pressure either between systolic and diastolic (lower pressure—LP) or 1.3 times the systolic pressure (higher pressure—HP). Three levels of torque (15, 30, and 50% of the maximal voluntary contraction—MVC) were combined with the three levels of pressure for a total of 9 (randomized) test cases. Each condition was repeated 3 times. The protocol was administered to 12 healthy young adults. Neuromechanical measurements (torque and high-density electromyography—HDEMG) and reported discomfort were used to investigate the response of the central nervous system to BFR. The investigated variables were: root mean square (RMS), and area under the curve in the frequency domain—for the torque, and average RMS, median frequency and average muscle fibres conduction velocity—for the EMG. The discomfort caused by BFR was exacerbated by the level of torque and accumulated over time. The torque RMS value did not change across conditions and repetitions. Its spectral content, however, revealed a decrease in power at the tremor band (alpha-band, 5–15 Hz) which was enhanced by the level of pressure and the repetition number. The EMG amplitude showed no differences whilst the median frequency and the conduction velocity decreased over time and across trials, but only for the highest levels of torque and pressure. Taken together, our results show strong yet transitory effects of BFR that are compatible with a motor neuron pool inhibition caused by increased activity of type III and IV afferences, and a decreased activity of spindle afferents. We speculate that a compensation of the central drive may be necessary to maintain the mechanical output unchanged, despite disturbances in the afferent volley to the motor neuron pool.

EFFECT OF EXERCISE WITH CONTINUOUS AND INTERMITTENT BLOOD FLOW RESTRICTION ON HEMODYNAMICS

ABSTRACT Introduction: Strength training with blood flow restriction (BFR) involves the use of low loads (20-30% of 1RM) with restriction of blood flow to promote gains in physical fitness. The restriction can be applied continuously or intermittently; however, it is unclear how it affects the hemodynamics of hypertensive women. Objective: To analyze the acute effect of resistance exercise (RE) on the upper and lower limbs with continuous and intermittent blood flow restriction (BFR) on the hemodynamic variables of women with hypertension. Methods: Thirteen women with controlled hypertension (40 to 65 years) underwent eight experimental protocols, with a randomized, counter balanced, crossover design; four exercise sessions for the right upper limb (elbow flexion) and four for the right lower limb (knee extension). The systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate (HR) were measured before, during, immediately after and 15, 30, 45 and 60 minutes after the exercises. Results: There were no significant interactions between the protocols vs. segments vs. time, protocols vs. segments, protocols vs. time, segments vs. time, protocol, segment and time, on the variables SAP, DAP, and HR during and after the RE (p&gt;0.05). Although all these protocols had significantly elevated SAP, DAP and HR, the values remained within the normal range. The protocols of this study did not cause hypotensive effect. Conclusion: Low-load RE combined with continuous and intermittent BFR, on the upper and lower limbs, appears to promote similar variations in the hemodynamic variables of women with hypertension. Level of evidence II; Randomized clinical trial.

Acute Effects of Continuous and Intermittent Blood Flow Restriction on Movement Velocity During Bench Press Exercise Against Different Loads.

This study evaluated the effects of continuous and intermittent blood flow restriction (BFR) with 70% of full arterial occlusion pressure on bar velocity during the bench press exercise against a wide range of resistive loads. Eleven strength-trained males (age: 23.5 ± 1.4 years; resistance training experience: 2.8 ± 0.8 years, maximal bench press strength – 1RM = 101.8 ± 13.9 kg; body mass = 79.8 ± 10.4 kg), performed three different testing protocols in random and counterbalanced order: without BFR (NO-BFR); intermittent BFR (I-BFR) and continuous BFR (C-BFR). During each experimental session, subjects performed eight sets of two repetitions each, with increasing loads from 20 to 90% 1RM (10% steps), and 3 min rest between each set. In the C-BFR condition occlusion was kept throughout the trial, while in the I-BFR, occlusion was released during each 3 min rest interval. Peak bar velocity (PV) during the bench press exercise was higher by 12–17% in both I-BFR and C-BFR compared with NO-BFR only at the loads of 20, 30, 40, and 50% 1RM (p < 0.001), while performance at higher loads remained unchanged. Mean bar velocity (MV) was unaffected by occlusion (p = 0.342). These results indicate that BFR during bench press exercise increases PV and this may be used as an enhanced stimulus during explosive resistance training. At higher workloads, bench press performance was not negatively affected by BFR, indicating that the benefits of exercise under occlusion can be obtained while explosive performance is not impaired.

Central And Systemic Haematological Responses Are Similar Between Continuous And Intermittent Blood Flow Restricted Resistance Exercise

Resistance training (RT) with blood flow restriction (BFR) induces similar adaptations to traditional RT but uses markedly lower training loads. However, information about the acute exercise pressor, hemodynamic, and local metabolic cost of this training approach is sparse. These data are needed to understand the acute safety implications of this training approach and help identify an optimal BFR protocol. PURPOSE: To compare the acute central and systemic cardiovascular, and local metabolic responses to resistance exercise performed with continuous (BFR-C) and intermittent (BFR-I) BFR. METHODS: 12 resistance-trained males (mean ± SD) aged 22.3 ± 3.2yrs, 1.82 ± 0.06m, and 84.1 ± 9.0kg performed 4 separate acute resistance training sessions in a random order, each separated by 7 days. Training sessions involved four sets of squat-based RT at 30% of individuals’ 1 repetition maximum with 1) no BFR (CON), 2) BFR-C, 3) BFR-I, and 4) traditional high load training at 70% of 1 repetition maximum with no BFR (HL). Systemic blood pressure and derivatives of cardiac output, central aortic blood pressure pulse wave characteristics, and local blood volume and metabolism were assessed periodically during, and after each training session. Data were assessed by two-way ANOVA with Bonferroni-corrected post-hoc comparisons. RESULTS: All sessions similarly increase average metabolic demand, seen by a decreased tissue saturation index (-15%, 95% CI 13.3 to 17.4, p<0.0001) with no difference between conditions (p>0.05). Whilst changes in haemoglobin-derived Vastus Lateralis blood volumes were similar between conditions, they were higher with BFR-C than CON (6.97 μmol/L, 95% CI 0.2 to 13.6, p=0.04) and HL (7.9 μmol/L, 95% CI 1.2 to 14.8, p=0.01). Training equally increased mean systemic mean arterial pressure (MAP) (+70.5 to 76.6 mmHg, p<0.001) and cardiac output (+0.74 to 0.96 L, p<0.001) above baseline, with no difference between conditions. Training also equally increased mean aortic MAP (+14.8 to 24.2 mmHg, p<0.001) above baseline across conditions. CONCLUSIONS: BFR-C and BFR-I cause similar exercise pressor responses comparable with both traditional resistance training, and training without BFR. Adding BFR to resistance training didn’t exacerbate the magnitude or duration of the associated cardiovascular stress.

Acute Physiological Responses to Resistance Exercise With Continuous Versus Intermittent Blood Flow Restriction: A Randomized Controlled Trial.

The primary goal of this investigation was to examine the physiological responses of blood flow restriction (BFR) resistance exercise (RE) performed with continuous or intermittent BFR and to compare these results to those from conventional high- and low-load RE without BFR. Fourteen men randomly completed the following experimental trials: (1) low-load RE with continuous BFR (cBFR), (2) low-load RE with intermittent BFR (iBFR), (3) low-load RE without BFR (LI), and (4) conventional high-load RE without BFR (HI). For the cBFR, iBFR, and LI exercise trials, participants performed four sets of 30–15–15–15 repetitions of the bilateral leg press (LP) and knee extension (KE) exercises, at an intensity of 20% of their one-repetition maximum (1-RM), at a 1.5-s contraction speed, and with a 1-min rest period between sets. The only difference between the cBFR and iBFR protocols was that the pressure of the cuffs was released during the rest intervals between sets for the iBFR trial. For the HI trial, participants completed four sets of 10 repetitions of the same exercises, at 70% of 1-RM, with a 1-min rest period between sets, and at the same contraction speed. Muscle activity was assessed during each set using superficial electromyography, as well as changes in blood lactate concentration [La–] from baseline at 5 min post exercise and in muscle swelling and plasma volume (%ΔPV) at 5 and 15 min post exercise. There were no significant differences in muscle activity (p < 0.05) across the cBFR, iBFR, and LI protocols at any time point, whereas they were all significantly lower than HI. There were also no significant (p < 0.05) differences across the three low-load RE conditions for [La–],%ΔPV, or muscle swelling. HI elicited significantly (p < 0.05) greater responses than cBFR, iBFR, and LI for all the physiological markers measured. In conclusion, RE combined with cBFR or iBFR induce the same acute physiological responses. However, the largest physiological responses are observed with HI, probably because of the significantly greater exercise volumes. Therefore, releasing the pressure of the restrictive cuffs during the rest periods between sets will not hinder the acute physiological responses from BFR RE.

Perceptual responses to continuous versus intermittent blood flow restriction exercise: A randomized controlled trial

We investigated the perceptual responses to resistance exercise (RE) with continuous and intermittent blood flow restriction (BFR). Fourteen males randomly completed the following exercise conditions: low-load RE with continuous BFR (cBFR), low-load RE with intermittent BFR (iBFR), low-load RE without BFR (LI), and traditional high-load RE (HI). Participants completed 4 sets of 30-15-15-15 repetitions of bilateral leg press and knee extension exercises during the low-load conditions, at 20% of one-repetition maximum (1-RM), a 1.5‑sec metronome-controlled pace, with a 1-min rest interval between sets; HI consisted of 4 sets of 10 repetitions of the same exercises, at 70% 1-RM, with the same pace and rest interval. Ratings of perceived exertion (RPE) and discomfort were assessed using psychometric scales before exercise and after each set. RPE displayed no significant differences (p > 0.05) between the BFR conditions for either exercise. Additionally, both BFR conditions elicited significantly (p < 0.05) greater RPE than LI and significantly (p <0.05) lower RPE than HI during both exercises. Rating of discomfort displayed no significant differences between BFR conditions during the first two sets of leg press; however, cBFR evoked greater discomfort compared to iBFR during the last two sets. There were no significant (p > 0.05) differences observed between conditions during the knee extension exercise. Rating of discomfort was similar between the BFR and HI conditions and each were significantly greater than LI during both exercises. Therefore, cBFR and iBFR seem to produce similar perceptual responses, which are greater than LI and lower than HI, but similar in regards to discomfort.

Effects of strength training with continuous or intermittent blood flow restriction on the hypertrophy, muscular strength and endurance of men

The aim of the present study was to compare the effects of strength training (ST) with continuous or intermittent blood flow restriction (BFR) on the muscle hypertrophy (MH), dynamic muscle strength (DMS), isometric muscle strength (IMS) and localized muscular endurance (LME) of healthy men. Twenty-five men with experience in ST were randomly divided into 3 experimental groups: a) 4 low-load exercises at 20% of the one-repetition maximum (1RM) combined with continuous BFR (LL+CBFR), b) 4 low-load exercises at 20% of 1RM combined with intermittent BFR (LL+IBFR); and c) 4 low-load exercises at 20% of 1RM without BFR (LL). Twelve sessions of ST were performed (twice a week for 6 weeks). There were no differences between groups for all variables (p > 0.05). However, there were significant differences in time for the LME in the triceps pulley only in the LL+CBFR group (p < 0.001) and in the biceps pulley in the groups LL+CBFR, LL+IBFR and LL (p < 0.001, p = 0.002, p = 0.032), respectively, with large magnitudes only for the two forms of the BFR. It can be concluded that continuous or intermittent BFR seems to be a good alternative for the increase of the LME of the upper limbs in single-joint exercises.

Resistance training with interval blood flow restriction effectively enhances intramuscular metabolic stress with less ischemic duration and discomfort.

Increases in muscle size and strength similar to those obtained with high resistance load can be achieved by combining lower loads with continuous blood flow restriction (BFR). However, high ratings for distress have been reported for continuous BFR. Therefore, we investigated the efficacy (metabolic stress) of BFR applied only during intervals in resistance exercise. Seven healthy men performed three 1-min sets of plantar flexion (30 reps/min) with 1-min rest intervals under 4 conditions: low-load resistance exercise (L, 20% 1-repetition maximum (1RM)) without BFR (L-noBFR), L with BFR during exercise sets (L-exBFR), L with BFR during rest intervals (L-intBFR), and L with continuous BFR during both exercise and rest intervals (L-conBFR). Based on the results of the first experiment, we performed additional protocols using a moderate load (M, 40% 1RM) with intermittent (exercise or rest intervals) BFR (M-exBFR and M-intBFR). Intramuscular metabolic stress, defined as decreases in phosphocreatine and intramuscular pH, was evaluated by 31P magnetic resonance spectroscopy. Rated perceived exertion (RPE) was also assessed. At the end of exercise, total decreases in phosphocreatine and intramuscular pH were similar among L-noBFR, L-intBFR, and L-exBFR and significantly less than those in L-conBFR (p < 0.05). In contrast, changes in these variables in M-intBFR but not in M-exBFR were similar to those in L-conBFR. Nevertheless, RPE was lower in M-intBFR than in both M-exBFR and L-conBFR (p < 0.05). The effect of intermittent BFR during exercise might be insufficient to induce metabolic stress when using a low load. However, effective metabolic stress for muscle adaptation could be obtained by moderate-load resistance exercise with BFR during intervals with less ischemic duration and discomfort.

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.

Does a resistance exercise session with continuous or intermittent blood flow restriction promote muscle damage and increase oxidative stress?

ABSTRACTThe aim of this study was to compare the effect of low-load resistance exercise (LLRE) with continuous and intermittent blood flow restriction (BFR) on the creatine kinase (CK), lactate dehydrogenase (LDH), protein carbonyl (PC), thiobarbituric acid-reactive substance (TBARS) and uric acid (UA) levels in military men. The study included 10 recreationally trained men aged 19 ± 0.82 years who underwent the following experimental protocols in random order on separate days (72–96 h): 4 LLRE sessions at a 20% 1RM (one-repetition maximum [1RM]) with continuous BFR (LLRE + CBFR); 4 LLRE sessions at 20% 1RM with intermittent BFR (LLRE + IBFR) and 4 high-intensity resistance exercise (HIRE) sessions at 80% 1RM. The CK and LDH (markers of muscle damage) levels were measured before exercise (BE), 24 h post-exercise and 48 h post-exercise, and the PC, TBARS and UA (markers of oxidative stress) levels were measured BE and immediately after each exercise session. There was a significant increase in CK in the HIRE 24 post-exercise samples compared with the LLRE + CBFR and LLRE + IBFR (P = 0.035, P = 0.036, respectively), as well as between HIRE 48 post-exercise and LLRE + CBFR (P = 0.049). Additionally, there was a significant increase in CK in the LLRE + CBFR samples BE and immediately after each exercise (Δ = 21.9%) and in the HIRE samples BE and immediately after each exercise, BE and 24 post-exercise, and BE and 48 post-exercise (Δ values of 35%, 177.6%, and 177.6%, respectively). However, there were no significant changes in LDH, PC, TBARS, and UA between the protocols (P > 0.05). Therefore, a physical exercise session with continuous or intermittent BFR did not promote muscle damage; moreover, neither protocol seemed to affect the oxidative stress markers.

Acute Effects of Resistance Exercise With Continuous and Intermittent Blood Flow Restriction on Hemodynamic Measurements and Perceived Exertion.

This study compared the acute effects of low-intensity resistance exercise (RE) sessions for the upper limb with continuous and intermittent blood flow restriction (BFR) and high-intensity RE with no BFR on lactate, heart rate, double product (DP; heart rate times systolic blood pressure), and perceived exertion (RPE). Ten recreationally trained men (1-5 years strength training; age mean = 19 ± 0.82 years) performed three experimental protocols in random order: (a) low-intensity RE at 20% one-repetition maximum (1RM) with intermittent BFR (LI + IBFR), (b) low-intensity RE at 20% 1RM with continuous BFR (LI + CBFR), and (c) high-intensity RE at 80% 1RM. The three RE protocols increased lactate and DP at the end of the session ( p < .05) and increased heart rate at the end of each exercise ( p < .05). However, greater local and general RPE was observed in the high-intensity protocol compared with LI + IBFR and LI + CBFR in the lat pull-down, triceps curl, and biceps curl exercises ( p < .05). A greater percentage change in DP and lactate was observed for continuous BFR compared with intermittent BFR; however, RPE was lower for intermittent BFR. In conclusion, intermittent BFR appears to be an excellent option for physical training because it did not differ significantly from continuous BFR in any variable and promoted a lower percentage change in DP and RPE.

Physiological responses to interval endurance exercise at different levels of blood flow restriction.

We aimed to identify a blood flow restriction (BFR) endurance exercise protocol that would both maximize cardiopulmonary and metabolic strain, and minimize the perception of effort. Twelve healthy males (23±2years, 75±7kg) performed five different exercise protocols in randomized order: HI, high-intensity exercise starting at 105% of the incremental peak power (P peak); I-BFR30, intermittent BFR at 30% P peak; C-BFR30, continuous BFR at 30% P peak; CON30, control exercise without BFR at 30% P peak; I-BFR0, intermittent BFR during unloaded exercise. Cardiopulmonary, gastrocnemius oxygenation (StO2), capillary lactate ([La]), and perceived exertion (RPE) were measured. V̇O2, ventilation (V̇ E), heart rate (HR), [La] and RPE were greater in HI than all other protocols. However, muscle StO2 was not different between HI (set1-57.8±5.8; set2-58.1±7.2%) and I-BRF30 (set1-59.4±4.1; set2-60.5±6.6%, p<0.05). While physiologic responses were mostly similar between I-BFR30 and C-BFR30, [La] was greater in I-BFR30 (4.2±1.1 vs. 2.6±1.1mmolL-1, p=0.014) and RPE was less (5.6±2.1 and 7.4±2.6; p=0.014). I-BFR30 showed similar reduced muscle StO2 compared with HI, and increased blood lactate compared to C-BFR30 exercise. Therefore, this study demonstrate that endurance cycling with intermittent BFR promotes muscle deoxygenation and metabolic strain, which may translate into increased endurance training adaptations while minimizing power output and RPE.

Hypotensive effects of resistance exercise with continuous and intermittent blood flow restriction

The aim of this study was to compare the acute effects of low-intensity (LI) resistance exercise (RE) with continuous blood flow restriction (CBFR) and intermittent blood flow restriction (IBFR) on systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP). After a one-repetition maximum test, 10 normotensive recreationally trained men performed three experimental protocols. In the three RE protocols, increases in SBP, DBP, and MAP were observed immediately after exercise, but the effect sizes (ESs) were greater for the LI + CBFR and high-intensity protocols. There were hypotensive effects on SBP, DBP, and MAP in all three protocols; however, the effects on MAP lasted longer for the LI + IBFR and LI + CBFR protocols. These long-lasting hypotensive effects on DBP and MAP occurred in all three protocols. Thus, we conclude that the post exercise hypotensive effects on SBP, DBP, and MAP appear to occur in all three RE protocols, with the effect on SBP being longer in the LI + IBFR and LI + CBFR protocols.

Effects of resistance training with blood flow restriction on haemodynamics: a systematic review.

This study systematically reviewed the available scientific evidence on the changes promoted by low-intensity (LI) resistance training (RT) combined with blood flow restriction (BFR) on blood pressure (BP), heart rate (HR) and rate-pressure product (RPP). Searches were performed in databases (PubMed, Web of Science™ , Scopus and Google Scholar), for the period from January 1990 to May 2015. The study analysis was conducted through a critical review of contents. Of the 1112 articles identified, 1091 were excluded and 21 met the selection criteria, including 16 articles evaluating BP, 19 articles evaluating HR and four articles evaluating RPP. Divergent results were found when comparing the LI protocols with BFR versus LI versus high intensity (HI) on BP, HR and RPP. The evidence shows that the protocols using continuous BFR following a LIRT session apparently raise HR, BP and RPP compared with LI protocols without BFR, although increases significantly in BP seem to exist between the HI protocols when compared to LI protocols. Haemodynamic changes (HR, SBP, DBP, MBP, RPP) promoted by LIRT with BFR do not seem to differ between ages and body segments (upper or lower), although they are apparently affected by the width of the cuff and are higher with continuous BFR. However, these changes are within the normal range, rendering this method safe and feasible for special populations.

Influence of continuous or intermittent blood flow restriction on muscle activation during low-intensity multiple sets of resistance exercise

Low-intensity resistance exercise with blood flow restriction (BFR) has been shown to induce a prominent increase in muscle activation in response to muscle fatigue. However, the magnitude of muscle fatigue between continuous (Con-BFR) and intermittent BFR (Int-BFR, BFR only during exercise) is currently unknown. We examined the effect of Con-BFR or Int-BFR on muscle activation during exercise. Unilateral arm curl exercise (20% of one-repetition maximum, four sets, 30 sec rest period between sets) was performed without (CON) or with Con-BFR or Int-BFR. During BFR conditions, the cuff was inflated to 160 mmHg on the proximal region of testing arm. Surface electromyography (EMG) was recorded from the biceps brachii muscle, and integrated EMG (iEMG) was analyzed. During the exercise, iEMG increased progressively in Con-BFR and Int-BFR and both conditions were greater (p < 0.05) than CON at the 3rd and 4th set. However, there were no differences (p > 0.05) in iEMG between Con-BFR and Int-BFR during exercise (∼2.45 and ∼2.40 times, respectively). Thus, the magnitude of increase in muscle activation may be similar between Con-BFR and Int-BFR when BFR exercise was performed at a high level of cuff pressure intensity.