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Reported Side-effects and Safety Considerations for the
Use of Blood Flow Restriction During Exercise
in Practice and Research
Christopher R. Brandner, PhD,* Anthony K. May, Bsc,†Matthew J. Clarkson, MSc,†
and Stuart A. Warmington, PhD†
Summary: Blood flow restriction (BFR) exercise is seen as a potential
alternative to traditional training methods, and evidence suggests this is
being used with both healthy and clinical populations worldwide.
Although the efficacy of the technique regarding muscular adaptations
is well known, the safety of its use has been questioned. The purpose of
this review was: (i) provide an overview of the known reported side-
effects while using BFR exercise; (ii) highlight risks associated with the
cardiovascular system, and; (iii) suggest recommendations to minimize
risk of complications in both healthy and clinical populations. Overall,
reported side-effects include perceptual type responses (ie, fainting,
numbness, pain, and discomfort), delayed onset muscle soreness, and
muscle damage. There may be heightened risk to the cardiovascular
system, in particular increased blood pressure responses, thrombolytic
events, and damage to the vasculature. However, while these may be of
some concern there is no evidence to suggest that BFR exercise elevates
the risk of complications any more than traditional exercise modes.
Several modifiable extrinsic factors for risk minimization include
selecting the appropriate BFR pressure and cuff width, as well as
completion of a preexercise safety standard questionnaire to determine
any contraindications to BFR or indeed the prescribed exercise. On the
basis of the available evidence, we are confident that the side-effects of
using BFR are minimal, and further minimized by the use of an
appropriate method of application in the hands of a trained practitioner.
Key Words: KAATSU—safety—side-effects—vascular occlusion—
exercise.
(Tech Orthop 2018;33: 114–121)
Exercise training with blood flow restriction (BFR) is a
technique whereby limb blood flow is reduced via external
compression that is typically applied with a pneumatic cuff or
tourniquet. More specifically, it is expected that BFR results in
a partial restriction to arterial in-flow while occluding venous
outflow. BFR is most commonly applied during resistance
exercise,1and is seen as a potential alternative to traditional
heavy-load resistance exercise (HLRE) [ ≥70% 1 repetition
maximum (1RM)] due to the light-loads prescribed (20% to
40% 1RM) that reduce the mechanical stress on the
musculoskeletal system, while providing gains in muscle
strength and mass that are greater than non-BFR equivalent
intensity exercise, and on occasion have been reported to be
similar to HLRE.2–4
The use of BFR in both healthy and clinical populations
has seen a rise in popularity over the past 2 decades, with many
of the original studies focusing on the efficacy of the use of
BFR with respect to muscle adaptations and performance. More
recently though, several papers have questioned the practicality
and safety of BFR in some human populations.5–13 However, it
would be expected that many of the purported risks and/or side-
effects may be avoided with well-controlled use of suitable
equipment to induce BFR, and when in the hands of trained
practitioners with knowledge of the technique.
To quantify the risk of BFR exercise for a specific pop-
ulation, it is important to compare the responses, side-effects,
and any adverse complications with that of traditional resistance
exercise with heavy-loads or light-loads, as well as high-
intensity and low-intensity aerobic exercise as these are the
current standards to improve muscle strength, mass, and
endurance. As an example, some populations are contra-
indicated to HLRE due to the risks associated with more
extreme elevations in blood pressure (BP), and thus the added
risk of a cardiovascular event.14 Others may be contraindicated
due to the mechanical strain placed on the musculoskeletal
system while lifting heavy-loads, such as low physical func-
tioning populations. Therefore, BFR exercise may be pre-
scribed as an alternative exercise method for populations con-
traindicated to traditional modes, provided that BFR confers
some benefit to the risk of elevated BP or provides benefit due
to the use of light-loads.
Therefore, the purpose of this review is to provide an
overview of the current literature associated with reported side-
effects while using BFR. In addition, to discuss factors that may
be considered important when examining the risks and con-
traindications of BFR. Lastly, we suggest several modifiable
factors for risk minimization when using BFR in populations
that are often contraindicated or those that may be at greater risk
of adverse events during traditional modes of exercise.
REPORTED SIDE-EFFECTS WHILE PERFORMING
BFR EXERCISE
There have been reports of side-effects as a result of
performing BFR exercise. Even the original creator of the BFR
technique (referred to as Kaatsu in Japan), acknowledged that
he found it difficult to apply the appropriate pressure for him-
self and to other individuals during early experimentations, to a
point where his skin would turn pale and he was later diagnosed
with pulmonary embolism, although there is no evidence to
suggest that this was caused by BFR.15
From the *Sports Science Department, Aspire Academy for Sports
Excellence, Doha, Qatar; and †Institute for Physical Activity and Nutrition
(IPAN), School of Exercise and Nutrition Sciences, Deakin University,
Geelong, Australia.
The authors declare that they have nothing to disclose.
For reprint requests, or additional information and guidance on
the techniques described in the article, please contact Christopher R.
Brandner, PhD, at chris.brandner@aspire.qa or by mail at Sports
Science Department, Aspire Academy for Sports Excellence, P.O. Box
22287, Doha, Qatar. You may inquire whether the author(s) will agree
to phone conferences and/or visits regarding these techniques.
Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
SYMPOSIUM
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As the technique was popularized in Japan, the largest
epidemiological study of BFR usage demonstrated particularly
low incidences of any adverse events for BFR exercise.5The
most common reported side-effect was subcutaneous hemor-
rhage (13%) followed by numbness (1.3%), and with occa-
sional reports of cerebral anemia, feeling cold, venous throm-
bus, pain, itch, and others. However, while some of these may
be considered more serious adverse outcomes, there is no
indication of any underlying medical conditions for those in the
survey who suffered adverse events, and given the occurrence
of these adverse outcomes was lower than the natural incidence
across the broader population, it is difficult to conclude that
these outcomes were a direct result of the BFR. However, it is
known that at the time of the survey, in Japanese centers BFR
was applied with relatively thin cuffs (∼3 cm) and high pres-
sures in excess of 160 to 200 mm Hg. As such, it is feasible that
this implementation of BFR may have been more likely to
produce adverse side-effects that are now rarely reported. A
more recent global survey of practitioners and researchers that
implement BFR in a wide variety of populations showed similar
reported incidence of subcutaneous hemorrhage/bruising (13%)
while numbness was more prevalent (19%). Again, there was
little evidence to directly align these outcomes with BFR, and
even less alignment with the method of BFR application (eg,
BFR pressure and cuff width). We are confident that the side-
effects of using BFR are minimal, and further minimized by
appropriate methods of application in the hands of a trained
practitioner.
Perceptual Type Responses
Fainting/Dizziness
One of the highest reported side-effects in a recent survey
of practitioners using the BFR technique was numbness and
fainting/dizziness, with almost 20% of respondents declaring
that they had observed this in their facility.1However, these
were only reported in <1% of cases by Nakajima and col-
leagues, and it is likely these reported incidences inflate the true
representation of these side-effects given there are no data on
the number of users/participants of BFR within each facility,
and does not account for overlap between practitioners in the
survey that encountered the same event. In any case, it is likely
these participants experienced postexercise hypotension, or
even a vaso-vagal response associated with the application of
BFR and so is expected to be a somewhat random incidence
rather than being clearly definable, identifiable, and predictable
in particular participants.
Numbness
The first randomized control trial to comment on a sen-
sation of numbness in the quadriceps muscle during BFR
exercise used high pressures (230 mm Hg) combined with wide
cuffs (13 cm).16 These are important factors to consider, given
that the BFR pressure, duration of inflation, and cuff width are
all modifiable prescription variables that may reduce the risk of
these adverse responses. It is worth noting that numbness with
BFR likely occurs either due to pressure applied to peripheral
nerves, or more likely the development of ischemia in response
to the restriction to flow.17 In 1 study, sensory motor nerve
conduction was not altered following 4 weeks of lower body
resistance exercise with BFR,18 which is not surprising given
that BFR is typically only held for relatively short durations of
5 to 20 minutes. Even with experiments in which complete
occlusion is induced for upwards of 30 minutes, these do not
result in any long-term adverse effects or maladaptations and
these side-effects are rapidly reversed following the removal of
the BFR.17 In addition, being transient events without long-
term concerns, we do not expect these to be prohibitive for the
prescription of BFR when using an appropriate method and in
the hands of a trained practitioner.
Ratings of Perceived Exertion, Pain, and Discomfort
Most often BFR presents greater ratings of perceived
exertion (RPE), pain, and discomfort despite the use of light-
load resistance exercise (20% to 40% 1RM).19–21 As such, one
might suggest that BFR remains unsuitable for populations with
low conditioning, poor motivation, and reduced adherence to
exercise programs. However, for these population, most forms
of exercise at least present with greater RPE. Therefore, if
undertaking structured exercise, BFR should form part of the
available repertoire. Indeed we have shown in older adults that
RPE was great in the initial stages of a BFR walking training
program, but this subsided over the first few sessions to be
equivalent to that for non-BFR walking training.22
Importantly, some studies have shown that perceived
exertion and pain are lower with BFR exercise in comparison
with HLRE.23,24 However, this seems to be a contentious area
within the BFR literature with some opposing reports that are
likely due to different exercise protocols and BFR method-
ologies used between studies.19,21,25 Nevertheless, with these
perceptual responses subsiding after a few exercise sessions
with BFR,20,26 there appears an adaptive effect on these per-
ceptual responses that facilitates greater tolerance to BFR
exercise once participants gain some familiarity with the
experience.
Delayed Onset Muscle Soreness
Delayed onset muscle soreness (DOMS) seems to be
commonly reported following BFR exercise, and can persist for
24,27 48,28 and even 72 hours postexercise24 depending on the
exercise protocol and BFR methodology being used. BFR
exercise has been shown to result in greater DOMS in com-
parison with exercise with the same loads without BFR,24,27
whereas only 1 study has compared this response to HLRE and
found the DOMS response to be greater with BFR.24
It is imperative to note that an episode of DOMS is rela-
tively normal following unaccustomed exercise bouts, or due to
higher than expected increases in exercise intensity (ie, external
load) or volume (ie, total exercise volume).29 So while the
DOMS response peaks between 24 and 72 hours postexercise,
this is a transient response to the exercise stimulus and not to
BFR per se, before muscle soreness levels return to resting
levels.
Markers of Muscle Damage
Given that DOMS is often associated with several markers
of exercise-induced muscle damage, several different measures
for muscle damage have been examined following BFR exer-
cise. These are often measured as a time course response
postexercise in comparison with resting measurements. Overall,
the affiliated markers of muscle damage appear only slightly
increased and/or rapidly return to resting levels. For example,
maximal voluntary contractile force is reduced immediately
postexercise30 and at 24 hours postexercise,27,31 whereas
changes in muscle swelling, circumference, and range of
motion all return to baseline levels within 24 hours of exercise
completion.28 Furthermore, although blood markers of muscle
damage have not been extensively examined, creatine kinase,
myoglobin, and interleukin-6 are not elevated following BFR
exercise in both young and older healthy adults.32–34 Given that
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these observed markers are relatively low, it would appear that
the BFR exercise confers no more risk for muscle damage (and
perhaps even less so) than traditional training methods.
Of note, 1 paper observed reduced quadriceps muscle
cross-sectional area at the site of muscle origin following BFR
training.16 However, this was likely due to the application of
wide cuffs in combination with suprasystolic restriction pres-
sures (230 mm Hg) resulting in high compression and shear
stress to the tissue under the cuff. There have also been case
study reports of BFR-inducing rhabdomyolysis,35,36 which is a
condition in which damaged skeletal muscle breaks down
rapidly and myoglobin is released into the circulation. The
patient in the first reported case study presented to hospital with
elevated creatine kinase levels following just a single bout of
BFR knee extension exercise. However, this patient was dis-
charged from hospital after 3 days, and 18 days after the inci-
dent continued BFR exercise without further (reported) inci-
dent. The patient in the more recent case study36 was a 30-year-
old overweight man (body mass index, 28.1 kg/m
2
) diagnosed
with rhabdomyolysis within 24 hours following a single BFR
exercise session. This was the first training session after a
period of inactivity. Physical inactivity, and the early intro-
duction of squats to a training program, which he performed
with a BFR (pressure and load not listed), are both considered
risk factors for rhabdomyolysis.37 In addition, before any
diagnosis of rhabdomyolysis, a high fever and pharyngeal pain
(diagnosed as tonsillitis) were reported after the session and
resulted in a local clinic prescribing a number of medications,
which may have further promoted the later onset/diagnosis and
treatment of rhabdomyolysis.38 Therefore, this case of rhab-
domyolysis seems to be more a result of a combination of
factors, and probably not a result of the BFR. The large epi-
demiological study conducted by Nakajima and colleagues
reported only 1 of 12,642 persons diagnosed with rhabdo-
myolysis following BFR exercise. More recently, of 115
practitioners surveyed in a questionnaire using BFR with their
clients/patients, 3% reported an incident of rhabdomyolysis
while using BFR.1However, 1 potential limitation of these
studies is that it is not clear how rhabdomyolysis was deter-
mined, while a large range of populations with possible con-
traindications to exercise/BFR were captured, making it diffi-
cult to relate the adverse effects to BFR when so few
occurrences have been noted. Overall, muscle damage seems to
be a minor risk following BFR exercise.
Other Reported Side-Effects
There have been few other side-effects described in the
current literature, but case studies have reported acute loss of
vision,39 and a series of complications including brain hemor-
rhage, petechial hemorrhage, and venous injury.40 Although
future studies are encouraged to report any side-effects that may
occur during BFR exercise, it is somewhat difficult to elucidate
if the complication was caused solely by BFR, the exercise
stimulus, or via any underlying complicating physiology/path-
ology. Furthermore, the potential risk of using BFR either with
or without exercise, and frequency of side-effects, should not be
any higher than what is typically seen following traditional
resistance or aerobic exercise.
POTENTIAL RISKS WHEN USING BFR DURING
EXERCISE
Before prescription of any traditional mode of exercise,
consideration is needed with regard to the potential risks of
adverse events. This is typically undertaken through standard
screening procedures to evaluate certain risks. Factors such as
age, training history/habits, evidence of chronic disease (dia-
betes, hypertension, obesity, etc.), genetic/family medical his-
tory, current/prior musculoskeletal injury, etc., all play a role.
However, often the focus is largely on BP and the associated
complications that may arise as a result, and which vary
between populations. These factors inform the practitioner of
the risk of prescription of HLRE as well as intense aerobic
exercise, yet despite BFR exercise prescribing the use of light-
loads, similar considerations must be given these common
contraindicators that confer added risk of adverse events to
undertaking any exercise type. Therefore, in the sections below,
we describe and discuss some of the potential contraindicators
to BFR exercise to characterize their significance in the context
of HLRE, given HLRE is considered the most likely exercise
type to confer a significant risk of an adverse event. In addition,
we review some other areas of focus that have previously been
raised as a concern when considering prescription of BFR
exercise.
Hemodynamics
For resistance exercise, the BP response increases in line
with the resistance load, volume, and mass of skeletal muscle
recruited for the action. Although this is normal for any exer-
cise, BP may be exacerbated during HLRE with maximal val-
ues for mean arterial pressure being reported upwards of
250 mm Hg.41 As such, BFR with light-loads is seen as a
potential alternative.
A large body of the current literature has focused on the
acute hemodynamic responses to BFR, both with and without
exercise, and a systematic review of these responses was pub-
lished recently.42 It seems that when matched for the same
external load (% 1RM) and total exercise volume (sets×repe-
titions), BFR resistance exercise typically elicits slightly higher
acute increases in heart rate (HR), BPs, and cardiac output, with
reductions in stroke volume, in comparison with non-BFR
exercise.23,43–47 However, when exercise is performed until
muscle failure, these acute hemodynamic responses are similar
between light-load BFR and non-BFR exercise.16,48 The mode
of exercise is also important to note, with BFR walking pro-
ducing comparably lower elevations in BPs, HR, and cardiac
output in comparison with BFR resistance exercise in both
healthy young and older populations.23,43
Comparisons with heavy-load exercise are less frequent
but in the context of risk assessment, probably the most
important. Nevertheless, the hemodynamic responses with BFR
exercise are generally shown to be similar,23,44 and in some
cases lower than for HLRE.47,48 For example, evidence from
our laboratory with both young and older healthy populations
has shown that HR, BP, and cardiac output responses are
similar to HLRE when utilizing high-pressure BFR exercise
(∼150 mm Hg), yet more similar to light-load resistance exer-
cise when the BFR pressure is reduced (∼90 mm Hg).44 Myo-
cardial workload (measured as the product of HR and BP) is
also lower with BFR exercise in comparison with HLRE49 or at
least not any greater than traditional HLRE.44,47 This is espe-
cially important to consider, given that increased muscle
strength and mass may be derived though BFR exercise in
conjunction with a reduction in exercising hemodynamic stress,
and so may alleviate some of the risk associated with HLRE for
populations that may be contraindicated.
Vasculature
There is growing interest in the effect of BFR exercise on
vascular function.48,50–57 In particular with respect to muscular
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endurance, with current evidence suggesting that BFR exercise
promotes postexercise blood flow, oxygen delivery, and capil-
larization (angiogenesis), resulting in an overall improvement in
microvascular function.53,58 The main stimuli for inducing
skeletal muscle angiogenesis include intramuscular hypoxia,
changes in vascular wall tension/shear stress, and mechanical
overload produced during muscle contraction. The result is an
increase in expression of several angiogenic factors. However,
despite the low mechanical tension associated with BFR exer-
cise in comparison with HLRE, results from a study by Larkin
et al59 showed that BFR exercise also increases the expression
of several angiogenic factors, including vascular endothelial
growth factor, hypoxia-inducible factor-1 α, and neuronal-nitric
oxide synthase. Importantly, these responses were shown to
be elevated immediately postexercise and up to 24 hours post-
exercise, which is similar to observations seen following HLRE60
and early BFR research.61 However, BFR exercise training
[4 weeks of knee extension; with BFR (30% 1RM) or without
(80% 1RM)] has not demonstrated any effect on measures of
pulse wave velocity in healthy young adults,18 andsothisneeds
further investigation.
This potential effect of BFR on vascular function may
prove particularly beneficial in populations that are more
susceptible to endothelial dysfunction as a result of progressive
atherosclerosis across the lifespan (eg, older adults). However,
this raises some degree of caution given that BFR is more likely
to produce turbulent arterial flow that can lead to vascular
damage, thus placing populations like older adults at greater
risk of a vascular event during BFR.9,62 Although, recent evi-
dence has demonstrated a positive effect on vascular endothelial
function and peripheral blood circulation in healthy older adults
without any reported contraindications.57 Again, there is little
evidence to support BFR being any more deleterious in pop-
ulations susceptible to vascular injury, but provides an element
of concern and certainly an area for future research.9,62
Thrombolytic Events
Given the nature of the application of BFR, there may be a
concern associated with obstruction of blood flow producing
conditions that may promote coagulation at sites of vascular
damage and atherosclerosis. Fortunately, as mentioned above,
there have yet to be any reports of deleterious effects of BFR on
the vasculature within well-designed research studies. The
epidemiological questionnaire conducted by Nakajima et al5
reported thrombolytic complications at 0.055% (7 cases) in
their large study sample, whereas only 0.8% of practitioners
reported thrombolytic events with their clients in a more recent
questionnaire, although the health and age of these participants
was not able to be determined.
One way to measure the effect of BFR exercise on
thrombolytic events is by examining the acute and training-
related changes in blood markers for coagulation (eg, fibrinogen
and D-dimer). Nakajima et al63 were the first to show that BFR
resistance exercise did not alter prothrombin time or markers of
coagulation, whereas Madarame et al64 also showed that blood
markers of thrombus formation and thrombin production are
not elevated following a single bout of 4 sets of leg press with
BFR. Similar results were found in a follow-up study by the
same authors in patients with stable ischemic heart disease
who were not currently treated with anticoagulant drugs.65
Although these studies examined the effects of BFR following
a single training session, Clark et al18 did not observe any acute
changes in fibrinolytic or coagulation markers following an
initial exercise session with either BFR or heavy-loads, or
following the final training session after 4 weeks of training in
healthy young adults. This seems to be similar in healthy older
adults (60 y and above), with 12 weeks of BFR resistance
exercise of both the lower-body66 and upper-body67 showing
no deleterious changes in coagulation factors such as fibrinogen
degradation product or D-Dimer.
In contrast to the negatively associated effects of BFR
exercise on thrombus formation, it would appear that resistance
exercise without BFR68 as well as BFR without exercise69 have
been shown to stimulate the fibrinolytic system. Importantly as
well, the combination of BFR and light-load resistance exercise
helps to promote a fibrinolytic state,63,64 which inhibits
thrombus formation. Therefore, while most of the afore-
mentioned studies were conducted in healthy populations, it
would appear that BFR exercise does not activate the coagu-
lation system.
MINIMIZING RISK FACTORS WHEN
PRESCRIBING BFR
There are several intrinsic and extrinsic factors that should
be considered before conducting BFR exercise. Intrinsic factors
can include an individuals’medical history, and are considered
contraindications to BFR exercise (Table 1). These are some-
what less modifiable than extrinsic factors. Other intrinsic
factors that are not contraindicators but should be considered
before prescription of BFR exercise can include age, lifestyle
TABLE 1. Possible Contraindications to Use of BFR
Cardiovascular disease
Coronary heart disease
Unstable hypertension
Peripheral vascular disease
Venous thromboembolism
Hypercoagulable states (blood clotting disorders)
Cardiopulmonary conditions
Atherosclerotic vessels causing poor blood circulation
Silent myocardial ischemia
Left ventricular dysfunction
Hemophilia
Vascular endothelial dysfunction
Varicose veins
Induration/Marfan syndrome
Musculoskeletal injury
Recent muscle trauma or crush injuries
Postsurgical excess swelling
Open fractures
Open soft tissue injuries
Skin graft
Lifestyle
Age
Smoking
Body mass (eg, obesity)
Pregnancy
Uncontrolled diabetes mellitus
Dyslipidemia
Dehydration
Family medical history
Clotting disorders
Sickle cell anemia
Atrial fibrillation or heart failure
Cancer
Medications
Those known to increase blood clotting risk
On the basis of authors review of the literature and in consultation
with medical professionals.
BFR indicates blood flow restriction.
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factors, blood vessel size, limb size, muscle and adipose tissue
thickness, and current strength capacity.15 As such, the mod-
ification of extrinsic factors such as the final BFR pressure,
duration of applied pressure, and the width of the cuffs or
tourniquets is required to prescribe BFR exercise in an effective
and safe manner.
Considerations on Patient Selection and Possible
Contraindications
The majority of data available on healthy young pop-
ulations suggests that BFR is a safe alternative to traditional
modes of exercise; however, possible contraindications to the
use of BFR are listed in Table 1. Over the past decade there has
been an increase in adoption of BFR exercise in clinical pop-
ulations such as older adults at risk of sarcopenia,67,70 pregnant
women,71 following musculoskeletal injury,72 patients with
metabolic syndrome,73 hypertension,74–76 cardiovascular
disease,65,77 as well as obese clients.78 Importantly, no adverse
risk responses have been reported in published randomized
control trials in these clinical populations, and while there have
been some reported side-effects to BFR, it remains difficult to
suggest whether BFR should be avoided in any special
populations.
All populations should be assessed for possible risks and
contraindications before performing BFR in research and
practice. Therefore, thorough clinical judgement is required by
the practitioner to determine if the individual is an appropriate
candidate to perform BFR. For all research studies involving
BFR (either with or without exercise), approval from the
Institutional Research Review Board and signed informed
consent from the study participants should be obtained.
Although it may not be necessary for the lead investigator of a
BFR research study to be a licensed physician, it would be
expected that this person should be an expert in BFR with
knowledge about principles, physiology, prescription, and
potential side-effects or adverse reactions to the technique. In
addition, it should be essential that before any use of BFR in
research or the field that a standard prequestionnaire screen
should be completed by all BFR candidates. An easy to use risk
assessment tool was recently published.10
Providing that screening is administered, and the
researcher/practitioner has knowledge of BFR and its applica-
tion, there is potential for the use of BFR with broader clinical
populations, provided the researcher/practitioner is well-versed
in exercise responses in those populations or protocols are
devised with a collaborator that is. For example, while uncon-
trolled hypertension may prohibit BFR use in the same way it
prohibits HLRE, those medicated for hypertension may still be
eligible for BFR exercise given that BP and BP responses may
still fall within “normal”ranges seen during and following
exercise.79 Diabetes is often strongly associated with hyper-
tension, and additionally requires strict monitoring of blood
glucose.80 However, both factors are easily measured and
controlled by medication, meaning BFR exercise may not be
contraindicated provided BP and blood glucose are monitored.
Diabetes may still be contraindicated to BFR in the presence of
symptomatic neuropathy or active retinal hemorrhage.80 Thie-
baud et al81 highlighted the potential benefits of BFR exercise
for chronic obstructive pulmonary disorder. Providing consid-
erations to underlying cardiovascular concerns are well man-
aged, and the prescription accounts for impaired respiratory
capacity, BFR may be valuable for chronic obstructive pulmonary
disorder. Pilot data (Stuart A Warmington and Matthew J Clarkson;
Data collected, 2016) from our research group indicates that
BFR applied during cycling exercise is appropriate for patients on
hemodialysis. Neither BP, HR, nor dialysis adequacy were affected
with low-to-moderate intensity BFR cycling compared with
equivalent intensity non-BFR cycling, which is already a recom-
mended prescription for dialysis patients.82 Although these sug-
gestions represent a range of clinical populations that may benefit
from BFR with additional considerations, it is by no means a
comprehensive list, and for most conditions further research is still
required to confirm the suitability of prescribing BFR exercise.
BFR Recommendations for Practitioners and
Research
It seems that the area of main concern regarding the use of
BFR relates to the equipment being used (in particular the width
of the restrictive cuff) and the final BFR pressure used during
exercise and how this may initially be determined. Early
research studies (eg, between 1998 and 2012) often prescribed
arbitrary and excessive BFR pressures. However, this method is
limited in that it does not account for interindividual differences
in limb size (ie, both muscle and adipose tissue content), vas-
cularization, and BP, which may not only decrease the efficacy
of BFR with regard to functional adaptations, but may also be a
safety concern if prescribed exercise pressures are excessive.
The major focus for prescribing a pressure during BFR exercise
should be to find the lowest possible pressure that remains
effective for the individual. Loenneke et al83 first proposed a
standardization method to account for interindividual differ-
ences when using BFR. It was suggested that the pressure that
produces a complete cessation of arterial blood flow, or the
individual arterial occlusion pressure (AOP) be determined
using Doppler Ultrasound at rest, and practitioners are
encouraged to use a set percentage of that measurement for the
BFR pressure.84 Methodology for determining the AOP using
Doppler Ultrasound has been provided previously,85 whereas
other devices utilize in-built technology to similarly determine
the maximal limb occlusion pressure (LOP). Importantly, time
of day also has an effect on the maximal AOP, thus practi-
tioners should endeavor to measurement of AOP immediately
before undertaking BFR exercise, or at least at the same time of
day as previous measurements of AOP.86 Furthermore, given
that pressure transmission from the cuff to the underlying tissue
is dependent on cuff width (discussed below), the cuff width
used to determine AOP must be the same as that used to restrict
blood flow during a BFR exercise bout.
Following on from the determination of AOP, the practi-
tioner must decide what percentage of AOP to prescribe for the
BFR user. The final restriction pressure used has varied widely
(50 to 300 mm Hg) depending on the individual and exercising
limb. However, similar increases in elbow flexion muscle
strength, mass, and endurance have been observed between
BFR pressures equal to 40% AOP (53 ±7 mm Hg) and 90%
AOP (116 ±17 mm Hg), suggesting that lower pressures could
be useful to avoid any deleterious responses to higher
pressures.87 There still is no consensus within the literature as
to the most optimal BFR pressure, and utilization of AOP/LOP
methods for BFR exercise is still low (11.5% of 115 surveyed
practitioners).1In addition, it is unknown whether different
BFR pressures may be required for prescription in different
populations. For example, athletes versus nonathletes, older
adults versus young adults, and a host of other populations. As
such, despite limited information on safe yet effective BFR
pressure prescription, we recommend use of a BFR pressure in
the range of 40% to 80% AOP for both the upper-body and
lower-body, with lower pressures perhaps just as efficacious as
higher pressures while minimizing the risk of contraindications
to BFR during exercise. It may also be prudent to begin training
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programs at lower percentages and progressively increase the
restriction pressure each exercise session while monitoring
physiological and perceptual responses.
Restrictive cuffs can range from 3 to ≥15 cm in width.
However, wider cuffs likely occlude arterial blood flow at lower
overall pressures in comparison with narrow cuffs.88,89 When
using the same percentage of maximal AOP (80%), no differ-
ences in muscle strength or mass were observed following 12
weeks of training with either wide (10 cm) or narrow (5 cm)
cuffs.90 However, when matched for the same relative pressure
(determined as a percentage of systolic BP), wider cuffs have
been shown to induce a greater cardiovascular response in
comparison with narrow cuffs,91 and this may be seen as a
potential concern, particularly for those with underlying car-
diovascular issues. Overall, wide cuffs (8 to 10 cm for upper-
body, 10 to 14 cm for lower-body) should provide a more
effective transmission of pressure through the underlying tissue
and vasculature in comparison with narrow cuffs (5 and 3 cm
for upper-body and lower-body, respectively), and thus lower
relative restriction pressures can be prescribed. It may be more
likely that narrow cuffs and subsequently higher restriction
pressures increase the risk of adverse responses in bruising,
nerve compression, and numbness. Finally, contoured cuffs
induce occlusion at lower pressures than commonly used
straight cuffs.92 As such, this should also be considered when
prescribing BFR pressures.
BFR AND ORTHOPEDIC CONSIDERATIONS
The majority of the BFR-published literature has been
conducted on nonclinical populations. However, clinicians have
begun to apply BFR as part of a rehabilitation program after
injuries and orthopedic surgery.72 A number of published
studies have assessed the effects of BFR after anterior cruciate
ligament reconstruction without adverse events.93,94 Time
frames ranged from days 3 to 14 and weeks 2 to 16 post-
operative. One trial included measurements of joint laxity via
knee ligament arthrometry (KT2000) and found no significant
difference between groups. The potential for thrombus for-
mation has only been assessed in 1 postoperative BFR trial. In
that study, 6 weeks of BFR after knee arthroscopy found no
signs of thrombus formation on Duplex Ultrasound imaging.95
Currently, there are registered orthopedic trials assessing
the effects of BFR after joint arthroplasty, anterior cruciate
ligament surgery, femur fractures, and wrist fractures.96 As
more large robust clinical trials are completed the safety of BFR
and appropriate clinical populations will be better understood.
Orthopedic surgeons have adopted the use of surgical grade
medical tourniquets in the operating room with minimal com-
plications. In the clinical setting, applying BFR following the
same safety principals utilized during surgery may help reduce
potential tourniquet complications.97
CONCLUSIONS
The purpose of this review was to briefly discuss the
reported side-effects of performing BFR either with healthy or
clinical populations, to present some possible contraindications
to BFR exercise, and to provide recommendations to minimize
risk when using BFR in populations that are often contra-
indicated or those that may be at greater risk of adverse events
during traditional modes of exercise.
On the basis of the current literature, it seems that BFR
exercise can be used safely in most populations without sig-
nificant risk of complications, provided that BFR is prescribed by
trained practitioners that have knowledge of appropriate protocols
(ie, restriction pressure application and durations, and their
interaction with different cuff widths), and the possible contra-
indications to the use of occlusive stimuli. It is recommended that
the final restriction pressures used during exercise should be
calculated as a percentage of each individual’s maximal AOP,
with lower pressures (ie, 40% to 80% AOP) perhaps conferring a
reduction in risk, making BFR safer and just as efficacious as
higher pressures for improving musculoskeletal mass and
strength, cardiovascular fitness, and functional abilities. The
current data examining the safety aspect of BFR is in its relative
infancy, although tourniquet safety has long been examined.
Therefore, before performing BFR it is recommended that prac-
titioners use a preexercise safety standard questionnaire that
accounts for listed contraindications to BFR exercise (as well as
traditional exercise modes) to determine any contraindications,
and future studies should report and discuss any side-effects
observed when using BFR exercise to improve our understanding
of any arising issues with respect to safety.
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