Blood Flow Restriction Resistance Exercise Research Articles

Acute Vascular and Cardiovascular Responses to Blood Flow–Restricted Exercise

Blood flow-restricted resistance exercise improves muscle strength; however, the cardiovascular response is not well understood. This investigation measured local vascular responses, tissue oxygen saturation (StO2), and cardiovascular responses during supine unilateral leg press and heel raise exercise in four conditions: high load with no occlusion cuff, low load with no occlusion cuff, and low load with occlusion cuff pressure set at 1.3 times resting diastolic blood pressure (BFRDBP) or at 1.3 times resting systolic blood pressure (BFRSBP). Subjects (N = 13) (men/women, 5/8, 31.8 ± 12.5 yr, 68.3 ± 12.1 kg, mean ± SD) performed three sets of leg press and heel raise to fatigue with 90-s rest. Artery diameter, velocity time integral, and stroke volume were measured using two-dimensional and Doppler ultrasound at rest and immediately after exercise. HR was monitored using a three-lead ECG. Finger blood pressure was acquired by photoplethysmography. Vastus lateralis StO2 was measured using near-infrared spectroscopy. A repeated-measures ANOVA was used to analyze exercise work and StO2. Multilevel modeling was used to evaluate the effect of exercise condition on vascular and cardiovascular variables. Statistical significance was set a priori at P < 0.05. Artery diameter did not change from baseline during any of the exercise conditions. Blood flow increased after exercise in each condition except BFRSBP. StO2 decreased during exercise and recovered to baseline levels during rest only in low load with no occlusion cuff and high load with no occlusion cuff. HR, stroke volume, and cardiac output (Q˙) responses to exercise were blunted in blood flow-restricted exercise. Blood pressure was elevated during rest intervals in blood flow-restricted exercise. Our results demonstrate that cuff pressure alters the hemodynamic responses to resistance exercise. These findings warrant further evaluations in individuals presenting cardiovascular risk factors.

Acute response and subcellular movement of HSP27, αB-crystallin and HSP70 in human skeletal muscle after blood-flow-restricted low-load resistance exercise.

Heat-shock proteins (HSP) are important chaperones for stressed and damaged proteins. Low-load blood-flow-restricted resistance exercise (BFRE) is generally believed not to induce significant muscle damage, but is hitherto unverified with intracellular markers. Consequently, the aim of this study was to investigate the HSP response after BFRE in human skeletal muscle. Nine healthy volunteers performed five sets to failure of unilateral knee extension at 30% of 1RM with partial blood-flow restriction. The contralateral leg performed the same work with free blood flow. Muscle biopsies were collected before exercise, 1, 24 and 48 h after exercise and analysed for HSP27, αB-crystallin, HSP70, desmin, glycogen content and myosin heavy chain by immunohistochemistry, ELISA and western blotting. One hour after exercise, HSP27 and αB-crystallin levels were reduced in the cytosolic and increased in the cytoskeletal fraction in the BFRE leg. HSP70 showed a delayed response and was increased over 48 h in the BFRE leg. Immunohistochemical analyses showed higher staining intensity of HSP70 in type 1 fibres in the BFRE leg at 24 and 48 h post-exercise. PAS staining showed decreased glycogen levels after BFRE, and interestingly, glycogen was still depleted 48 h after exercise in the same fibres displaying high HSP70 staining (type 1 fibres). Translocation of HSP27 and αB-crystallin from cytosol to cytoskeletal structures indicates that cytoskeletal proteins are stressed during BFRE. However, overt signs of myofibrillar disruptions were not observed. Interestingly, the stress response was more pronounced in type 1 than in type 2 fibres and coincided with low glycogen levels.

Hyperactivation of skeletal muscle stem cells with blood flow restricted resistance exercise: Implications for muscle hypertrophy in sports and the clinical setting

Hyperactivation of skeletal muscle stem cells with blood flow restricted resistance exercise: Implications for muscle hypertrophy in sports and the clinical setting

Perceptual effects and efficacy of intermittent or continuous blood flow restriction resistance training

Blood flow restriction (BFR) exercise may be an alternative form of resistance training; however, a side of effect of BFR resistance exercise is acute muscle pain. Typically, BFR exercise studies restrict blood flow with a cuff continuously during the exercise bout, including rest periods. However, others have used intermittent BFR where the cuff is inflated only during sets. We performed two studies to compare intermittent and continuous BFR exercise. In study one, eleven subjects randomly proceeded through three treatments of unilateral leg extensions to failure: (i) continuous BFR, (ii) intermittent BFR and (iii) control (exercise without BFR). Pain measurements were taken immediately after each set. In study two, subjects (n = 32) underwent a 5-week resistance training programme after random assignment to one of the three conditions. Lean mass and strength were assessed at baseline and after training. Continuous BFR resulted in significantly greater pain than intermittent BFR or control. Both BFR conditions resulted in significantly fewer repetitions to failure than control. This suggests that an acute bout of intermittent BFR exercise may produce as much muscle fatigue as an acute bout of continuous BFR exercise, but with less pain. With training, maximal knee extension (P = 0·033) and maximum knee flexion (P = 0·007) strength increased among all groups. There were no significant differences between groups in strength or lean mass. These results suggest that short-term low-load resistance training increases muscle strength to a similar extent as low-load resistance training without BFR.

Blood flow-restricted exercise in space

Prolonged exposure to microgravity results in chronic physiological adaptations including skeletal muscle atrophy, cardiovascular deconditioning, and bone demineralization. To attenuate the negative consequences of weightlessness during spaceflight missions, crewmembers perform moderate- to high-load resistance exercise in conjunction with aerobic (cycle and treadmill) exercise. Recent evidence from ground-based studies suggests that low-load blood flow-restricted (BFR) resistance exercise training can increase skeletal muscle size, strength, and endurance when performed in a variety of ambulatory populations. This training methodology couples a remarkably low exercise training load (approximately 20%–50% one repetition maximum (1RM)) with an inflated external cuff (width, ranging between approximately 30–90 mm; pressure, ranging between approximately 100–250 mmHg) that is placed around the exercising limb. BFR aerobic (walking and cycling) exercise training methods have also recently emerged in an attempt to enhance cardiovascular endurance and functional task performance while incorporating minimal exercise intensity. Although both forms of BFR exercise training have direct implications for individuals with sarcopenia and dynapenia, the application of BFR exercise training during exposure to microgravity to prevent deconditioning remains controversial. The aim of this review is to present an overview of BFR exercise training and discuss the potential usefulness of this method as an adjunct exercise countermeasure during prolonged spaceflight. The work will specifically emphasize ambulatory BFR exercise training adaptations, mechanisms, and safety and will provide directions for future research.

Blood flow‐restricted resistance exercise: rapidly affecting the myofibre and the myonuclei

Acute blood flow restriction (BFR) by itself or in combination with low-intensity aerobic and/or low-load resistance exercise has been shown to result in favourable effects on skeletal muscle, namely increases in muscle size and strength (Loenneke et al. 2012). These positive muscular adaptations have been observed across a wide range of populations (e.g. athletes, elderly, diseased). Previous research indicates that BFR resistance exercise stimulates muscle protein synthesis (MPS) (Gundermann et al. 2012); however, little is known about the exact cellular mechanisms behind that response on muscle protein synthesis or muscle hypertrophy. Previous research suggests that the muscle hypertrophic effect may, in part, be related to the concomitant decrease in the mRNA gene expression of E3-ligases such as MURF-1 (8 h post-decrease; Manini et al. 2011) and atrogin (Manini et al. 2011). Furthermore, Laurentino et al. (2012) have observed decreased mRNA gene expression of myostatin, with an increased expression of the follistatin isoforms following low-load resistance exercise with BFR. In a recent issue of The Journal of Physiology, Nielsen et al. (2012) presented research that suggests that the proliferation of myogenic stem cells may be an additional mechanism involved in the muscle hypertrophic response to high-frequency low-load resistance exercise with BFR. Briefly, participants performed four sets of knee extensor exercise to failure at 20% of their concentric one repetition maximum. The researchers found that performing 23 sessions of low-load BFR exercise within 19 days resulted in marked increases in muscular strength and muscle fibre cross-sectional area when measured greater than 3 days post-training. It should be mentioned that there were transient increases in muscle fibre cross-sectional area after 5 days of the intervention in both groups; however, this was thought to be due to exercise-induced cell swelling and not a reflection of true muscle hypertrophy. This is supported by the post-training data which indicated increases in muscle size and strength only in the BFR group, while the work-matched control groups’ fibre cross-sectional area was equivalent to baseline levels. These positive muscular adaptations in the BFR group were accompanied by a substantial upregulation in myogenic stem cells, resulting in nuclear additions to the exercised muscle fibre. The data reported in the Nielsen et al. (2012) investigation provides valuable insight into the acute and chronic effects of high-frequency low-load resistance training with BFR. The increased proliferation of myogenic stem cells with BFR resistance training is significant as it is thought that the myonuclear donation is required in order to have substantial increases in human muscle fibre cross-sectional area. Further support of this notion comes from their data which show positive correlations between the change in myonuclei number per fibre and muscle fibre area as well as between the relative change in myogenic stem cells per fibre and muscle fibre area. The exact reason behind the large increase in myogenic stem cell proliferation is not known, but the authors speculated that the activation and proliferation of myogenic stem cells may be acutely stimulated by BFR-induced stretch-, hypoxia-, and/or contraction-induced nitric oxide secretion. In addition, they noted that it was unlikely that the increased proliferation was due to muscle cell membrane damage because the authors did not find any visible signs of damage to the basal lamina from their laminin stainings. This finding is consistent with previous BFR studies, which indicate minimal to no muscle damage with this type of exercise. It would be interesting if future research could expand on these findings and investigate whether or not there is proliferation of myogenic stem cells and a subsequent myonuclear addition in response to low-intensity aerobic exercise in combination with BFR. This type of study would be useful as low-intensity aerobic exercise with BFR has been observed to elicit significant increases in muscle size and strength (Loenneke et al. 2012). Currently it is unknown if the mechanisms behind that effect are different to that observed with low-load resistance training. Additionally, BFR in the absence of exercise has been shown to attenuate atrophy; however, it is unclear as to the exact mechanism involved with BFR in the absence of muscle contraction. Whether or not there is a relationship between the application of BFR in the absence of muscle contraction and myogenic stem cells is unknown but might be an interesting avenue of research to explore in the future.

Exercise intensity and muscle hypertrophy in blood flow–restricted limbs and non‐restricted muscles: a brief review

Although evidence for high-intensity resistance training-induced muscle hypertrophy has accumulated over the last several decades, the basic concept of the training can be traced back to ancient Greece: Milo of Croton lifted a bull-calf daily until it was fully grown, which would be known today as progressive overload. Now, in the 21st century, different types of training are being tested and studied, such as low-intensity exercise combined with arterial as well as venous blood flow restriction (BFR) to/from the working muscles. Because BFR training requires the use of a cuff that is placed at the proximal ends of the arms and/or legs, the BFR is only applicable to limb muscles. Consequently, most previous BFR training studies have focused on the physiological adaptations of BFR limb muscles. Muscle adaptations in non-BFR muscles of the hip and trunk are lesser known. Recent studies that have reported both limb and trunk muscle adaptations following BFR exercise training suggest that low-intensity (20-30% of 1RM) resistance training combined with BFR elicits muscle hypertrophy in both BFR limb and non-BFR muscles. However, the combination of leg muscle BFR with walk training elicits muscle hypertrophy only in the BFR leg muscles. In contrast to resistance exercise with BFR, the exercise intensity may be too low during BFR walk training to cause muscle hypertrophy in the non-BFR gluteus maximus and other trunk muscles. Other mechanisms including hypoxia, local and systemic growth factors and muscle cell swelling may also potentially affect the hypertrophic response of non-BFR muscles to BFR resistance exercise.

Cardiovascular and perceptual responses to blood‐flow‐restricted resistance exercise with differing restrictive cuffs

The purpose of this study was to determine (i) the cardiovascular responses to acute blood-flow-restricted (BFR) resistance exercise and (ii) the influence of applied BFR cuff type on the cardiovascular and perceptual responses. In a randomized, crossover design, 27 participants wore either a 5·0cm wide elastic cuff or a 13·5cm wide non-elastic cuff around the thigh while performing four sets of knee extension exercise using 20% of 1-RM. Brachial and central blood pressure (BP) and aortic augmentation index (AIx) were measured before and after the restrictive cuffs were applied and inflated, after the 2nd and 4th set of resistance exercise, and 5 and 15min following the 4th set of exercise. Ratings of perceived exertion and pain were obtained before exercise and after the 2nd and 4th set of exercise. Both brachial and central BPs increased and AIx decreased during BFR exercise but returned to baseline levels within 15min following exercise. The wide cuffs caused a greater elevation in heart rate, brachial and central BPs, perceived effort and pain and a greater decrease in AIx during the BFR exercise. These findings suggest that low-intensity BFR resistance exercise does not appear to acutely negatively affect the vasculature. Also, cuff type will greatly affect cardiovascular and perceptual responses to BFR resistance exercise and thus is an important consideration in study design.

Sarcolemmal permeability and muscle damage as hypertrophic stimuli in blood flow restricted resistance exercise (Reply to Loenneke and Abe)

Dear Editor,We welcome the letter by Loenneke and Abe (2011)relating to our recent publication (Wernbom et al. 2011), aswe feel that the topics are of importance and deserve fur-ther discussion.1. Regarding their first point, we were interested instudying the recovery of maximal voluntary contraction(MVC) during maintained partial blood flow restriction(BFR) in order to document the acute effects of our BFRmodel on muscle function during and after exercise, whileblood flow was still restricted. We were also aiming tostudy later recovery, hence our choice of time points.2. Regarding their second point, we acknowledge thatthere were no significant differences in MVC after the BFRwas released. However, there was a trend for MVC of theBFR leg to still be reduced at 72 h post-exercise(p\0.10), the nonsignificance possibly reflecting a type IIerror. Nevertheless, some signs of membrane permeabilitywere present also in the free-flow leg, see below.Concerning signs of damage in the BFR leg, Umbelet al. (2009) demonstrated greater reductions in MVC(-14.1 vs. -1.5%) in the BFR leg than in the free-flowtrained leg at 24 h post-exercise. Interestingly, inspectionof their figures on vastus lateralis cross-sectional area(CSA) reveals a muscle swelling of *5.5% at 24 h post-exercise (vs. *2% in the free-flow leg), and the swelling at24 h was significant when the CSA data for both legs werecombined. The moderate torque decrements, muscleswelling and delayed onset muscle soreness (DOMS) areconsistent with the suggestion of mild muscle damage, asproposed by Umbel et al. (2009). The torque decrements,the signs of increased membrane permeability, the pro-longed increase in resting tension, and DOMS in our study(Wernbom et al. 2011) are also consistent with thisproposal.There are other reports that signs of muscle damage canbe induced by low-to-moderate load resistance exerciseduring ischemic conditions (see point 3), and also a casereport on rhabdomyolysis after BFR-resistance exercise(Iversen and Rostad 2010). These findings suggest that thepotential for muscle damage with strenuous acute BFR-resistance exercise needs to be taken seriously.However, it should also be emphasised that this was thefirst time that our subjects performed strenuous BFR-resistance exercise. It is our experience that the symptomsof muscle damage are much less evident with subsequentbouts, suggesting a protective ‘‘repeated-bout effect’’similar to that for eccentric exercise.3. Concerning Loenneke and Abe’s third point, it shouldbe noted that the exercise was performed without relaxa-tion between repetitions. Signs of ischemia with continuousdynamic knee-extensions have been noted at loads as lowas 10% of MVC (Shoemaker et al. 1994), and isometricknee-extensions at 25–35% of MVC elicited a similar

Methodological considerations for blood flow restricted resistance exercise

Blood flow restricted (BFR) resistance exercise has become a popular area of research. However, studies use a range of blood flow restriction and resistance exercise protocols. Objectives: To provide an overview of the methods used for BFR resistance exercise for individuals interested in utilizing BFR training and for researchers studying the acute and chronic effects of BFR resistance exercise. Design: A systematic review. Method: BFR resistance training studies with muscular strength and hypertrophy as main outcomes were identified. Resistance exercise protocol and blood flow restriction protocol were compared between these studies. Acute BFR resistance exercise studies comparing different BFR protocols were also examined. Results: Continuous, partial arterial blood flow restriction during resistance exercise appears to be tolerable and effective for increasing both limb and trunk muscle strength and hypertrophy. Compared to non-BFR exercise, blood flow restriction produces an additive effect when combined with resistance exercise loads of <50% one-repetition maximum. Optimal BFR resistance training frequency may be higher (2x daily) than high-load resistance exercise. Conclusions: Restrictive cuff size, pressure, and limb circumference affect the degree of blood flow restriction and should be carefully considered when performing or prescribing BFR resistance exercise. The volume and frequency of BFR resistance exercise may depend on the trainee's capabilities and goals.

Blood Flow Restriction: How Does It Work?

Blood Flow Restriction: How Does It Work?

The effect of acute blood-flow-restricted resistance exercise on postexercise blood pressure

Blood-flow-restricted (BFR) exercise is an emerging type of exercise that may be particularly beneficial to elderly or special populations. These populations may also benefit from reductions in blood pressure (BP). The effect of BFR exercise on postexercise BP has not been examined; this should first be examined in a young, healthy population as a preliminary investigation. The main purpose of this study was to determine whether postexercise hypotension (PEH) occurred following low-intensity [20% 1 repetition maximum (1-RM)] BFR resistance exercise. A secondary purpose was to compare this response to both a work-matched low-intensity (20% 1-RM) (LI) and a traditional high-intensity (70% 1-RM) resistance exercise bout (HI). In a randomized cross-over design, ten normotensive, young (18-35 years) men performed one of the three lower-body resistance exercise bouts (HI, LI or low-intensity BFR) during separate visits to the laboratory. Brachial BP, cardiac ultrasound and calf blood flow measurements were taken prior to and 30 and 60 min following exercise. Repeated measures analysis of variance (3 × 3; condition × time) was performed on all variables. A significant interaction (P<0·05) was found for brachial systolic blood pressure which decreased following HI only. Significant interactions (P<0·05) were also seen for heart rate, total peripheral resistance and calf vascular resistance. Postexercise hypotension occurred only following HI. Thus, if one is exercising with the intent of lowering BP, HI resistance exercise may be more useful than low-intensity BFR resistance exercise.

Hormone Responses to Acute and Chronic Traditional and Blood Flow Restricted Resistance Exercise in Young Men

Hormone Responses to Acute and Chronic Traditional and Blood Flow Restricted Resistance Exercise in Young Men

Acute and Chronic Effects of Traditional and Blood Flow Restricted Resistance Exercise on Bone Markers

Acute and Chronic Effects of Traditional and Blood Flow Restricted Resistance Exercise on Bone Markers

Muscle Damage and Inflammation Marker Responses to Acute and Chronic Blood Flow Restricted Resistance Exercise

Muscle Damage and Inflammation Marker Responses to Acute and Chronic Blood Flow Restricted Resistance Exercise

The Effect Of Low-intensity Blood-flow Restricted Resistance Exercise On Post-exercise Blood Pressure

The Effect Of Low-intensity Blood-flow Restricted Resistance Exercise On Post-exercise Blood Pressure

Acute Systemic Growth Responses To Low Intensity Blood Flow Restricted Resistance Exercise In Old Men

Acute Systemic Growth Responses To Low Intensity Blood Flow Restricted Resistance Exercise In Old Men

Fibrinogen, D-dimer and tPA Antigen Concentrations Following Acute and Chronic Blood Flow Restricted Resistance Exercise

Fibrinogen, D-dimer and tPA Antigen Concentrations Following Acute and Chronic Blood Flow Restricted Resistance Exercise

Acute Systemic Growth Responses To Low Intensity Blood Flow Restricted Resistance Exercise

Previous research has demonstrated that blood flow restriction during low intensity resistance exercise (BFR-Low) results in a potent muscle growth response in humans. However, it is unclear whether this stimulus is similar to that provoked with free-flow high intensity resistance exercise (FF-HI). PURPOSE: To determine the acute growth hormone (GH) and insulin-like growth factor (IGF-1) responses to BFR-Low and FF-HI in young adults. Additionally, because BFR may induce adverse reactions we evaluated cardiovascular, endothelial inflammation with vascular cell adhesion molecule (VCAM) and blood coagulation (D-dimer) responses. METHODS: Ten healthy subjects aged 20-39 years reported to the laboratory between 7 and 9 AM on two separate occasions in a fasted condition. Knee extension exercise was performed at 20% of maximal strength for the BFR-Low condition in comparison to a FF-HI performed at 80% of maximal strength. Both conditions were performed for 5 sets until task failure. During BFR-Low exercise, a 10 cm wide tourniquet cuff was placed around the upper thigh at 1.5 systolic blood pressure immediately before exercise and remained inflated (∼15 minutes). Blood was sampled every 10 minutes for 150 minutes to assess GH responses and IGF-1 was measured at baseline and 90 minutes post-exercise. RESULTS: Subjects demonstrated a greater mean increase in GH levels with BFR-Low exercise (2.1 ± 2.1 ng/ml) when compared to FF-HI (1.5 ± 2.6 ng/ml), but this difference was not statistically different (p = 0.61). IGF-1 levels demonstrated no change regardless of the exercise condition. Peak heart rate (HR) and systolic blood pressure (BP) showed similar responses to both conditions (HR: BFR-Low: 83.8 ± 12.4; FF-HI: 84.8 ± 6.7 bpm) (SBP: BFR-Low: 148.8 ± -.9 vs. FF-HI: 139.0 ± 15.6 mmHg). Peak diastolic blood pressure was elevated to a greater extent during BFR-Low exercise (BFR-Low: 103 ± 9.7; FF-HI: 92.6 ± 12.4, p=0.05). D-dimer, a degradation product of crosslinked fibrin and VCAM levels showed no change 30 min post exercise for either condition. CONCLUSIONS: Resistance exercise performed at low intensity with BFR has a similar systemic acute growth, blood coagulation and endothelial inflammatory response, but greater cardiovascular demand when compared to resistance exercise performed at a high intensity.

Glycogen depletion pattern in human skeletal muscle fibers after heavy exercise.

Glycogen depletion pattern in human skeletal muscle fibers after heavy exercise.