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SAFETY CONSIDERATIONS WITH BLOOD FLOW RESTRICTED RESISTANCE TRAINING

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Blood flow restricted resistance (BFRR) training with pneumatic tourniquet has been suggested as an alternative for conventional weight training due to the proven benefits for muscle strength and hypertrophy using relatively low resistance, hence reducing the mechanical stress across a joint. As such, it has become an important part of rehabilitation programs used in either injured or operated athletes. Despite a general consensus on effectiveness of BFRR training for muscle conditioning, there are several uncertainties regarding the interplay of various extrinsic and intrinsic factors on its safety and efficiency, which have been reviewed from a clinical perspective. Among extrinsic factors tourniquet cuff pressure, size and shape have been identified as key for safety and efficiency. Among intrinsic factors, limb anthropometrics, patient history and presence of cardiac, vascular, metabolic or peripheral neurologic conditions have been recognized as most important. Though there are a few potential safety concerns connected to BFRR training, the following have been identified as the most probable and health-hazardous: (a) mechanical injury to the skin, muscle, and peripheral nerves, (b) venous thrombosis due to vascular damage and disturbed hemodynamics and (c) augmented arterial blood pressure responses due to combined high body exertion and increased peripheral vascular resistance. Based on reviewed literature and authors’ personal experience with use of BFRR training in injured athletes, guidelines have been given for its safe application. Also, a comprehensive risk assessment tool for screening of subjects prior to their inclusion in a BFRR training program has been introduced.
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
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SAFETY CONSIDERATIONS WITH BLOOD FLOW
RESTRICTED RESISTANCE TRAINING
Alan KACIN1, Benjamin ROSENBLATT2, Tina GRAPAR ŽARGI1, Anita BISWAS2
1 University of Ljubljana, Faculty of Health Sciences, Department of Physiotherapy Ljubljana,
Slovenia
2 English Institute of Sport, Bisham Abbey National Sports Centre, Marlow, SL7 1RR, United
Kingdom
Corresponding author:
Alan KACIN, RPT, PhD
University of Ljubljana, Faculty of Health Sciences, Department of Physiotherapy
Zdravstvena pot 5, 1000 Ljubljana, Slovenia
Phone: +386 1 300 11 43
Skype: alankacin
E-mail: alan.kacin@zf.uni-lj.si
ABSTRACT
Blood ow restricted resistance (BFRR) training with pneumatic tourniquet has
been suggested as an alternative for conventional weight training due to the proven
benets for muscle strength and hypertrophy using relatively low resistance, hence re-
ducing the mechanical stress across a joint. As such, it has become an important part of
rehabilitation programs used in either injured or operated athletes. Despite a general
consensus on effectiveness of BFRR training for muscle conditioning, there are several
uncertainties regarding the interplay of various extrinsic and intrinsic factors on its
safety and efciency, which are being reviewed from a clinical perspective. Among
extrinsic factors tourniquet cuff pressure, size and shape have been identied as key
for safety and efciency. Among intrinsic factors, limb anthropometrics, patient history
and presence of cardiac, vascular, metabolic or peripheral neurologic conditions have
been recognized as most important. Though there are a few potential safety concerns
connected to BFRR training, the following have been identied as the most proba-
ble and health-hazardous: (a) mechanical injury to the skin, muscle, and peripheral
nerves, (b) venous thrombosis due to vascular damage and disturbed hemodynamics
and (c) augmented arterial blood pressure responses due to combined high body exer-
tion and increased peripheral vascular resistance. Based on reviewed literature and
authors’ personal experience with the use of BFRR training in injured athletes, some
guidelines for its safe application are outlined. Also, a comprehensive risk assessment
review article UDC: 615.825:796.071.2
received: 2015-08-19
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
tool for screening of subjects prior to their inclusion in a BFRR training program is
being introduced.
Keywords: blood ow restricted exercise, health risk assessment, tourniquet cuff
efciency, rehabilitation of athletes.
VARNA UPORABA VADBE Z ZMANJŠANIM
PRETOKOM KRVI
IZVLEČEK
Vadba proti majhnem uporu s sočasno zmanjšanim pretokom krvi v aktivnih mišicah
(ishemična vadba) dokazano spodbuja hipertrojo in izboljša mišično jakost primerlji-
vo s standardno vadbo proti velikem uporu, vendar ob znatno manjši mehanski obreme-
nitvi sklepa. Zato se ishemično vadbo pospešeno vključuje v zioterapevtske programe,
zlasti pri športnikih s poškodbami ali operativnimi posegi na sklepih spodnjih ali zgor-
njih udov. Kljub splošnem strinjanju glede pozitivnih učinkov na mišično zmogljivost
ostaja vrsta nejasnosti glede medsebojnega učinkovanja vrste intrinzičnih in ekstrinzič-
nih dejavnikov, ki se pojavijo med ishemično vadbo in zelo verjetno vplivajo na njeno
učinkovitost in varnost. Regulacija in velikost manšetnega tlaka ter oblika in velikost
manšete so bili prepoznani kot ključni ekstrinzični dejavniki varnosti in učinkovitosti.
Med intrinzičnimi dejavniki pa so bili v tem pogledu kot najbolj pomembni prepozna-
ni sledeči: antropometrija uda in prisotnost preteklih ali sedanjih srčnih, žilnih, pre-
snovnih ali perifernih živčnih okvar pacienta. Izmed vrste potencialnih zdravstvenih
problemov, povezanih z ishemično vadbo, so najbolj verjetni in zdravje ogrožajoči (a)
mehanske poškodbe kože, mišic in perifernih živcev, (b) globoka venska tromboza za-
radi poškodb ožilja in spremenjene hemodinamike in (c) povečan odziv arterijskega
krvnega tlaka zaradi povečanega občutka napora in upora perifernega ožilja zaradi
nameščene manšete. Na podlagi objavljenih podatkov v literaturi in osebnih izkušenj
avtorjev članka z uporabo ishemične vabe pri športnikih so podana priporočila za nje-
no varno uporabo. V članku je predstavljen tudi enostaven in razumljiv pripomoček
za presojanje dejavnikov zdravstvenega tveganja posameznika pred vključitvijo v pro-
gram ishemične vadbe.
Ključne besede: vadba z oviranim pretokom krvi, ocena dejavnikov tveganja, učin-
kovitost manšetnega sistema, zioterapija in rehabilitacija športnikov
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INTRODUCTION
Blood ow restricted resistance (BFRR) training, its most featured version also
known as kaatsu training, has long been suggested as an alternative for conventional
weight training due to the proven benets for muscle strength and hypertrophy using
relatively low resistance, hence reducing the mechanical stress across a joint. It has
been used in the elderly to maintain muscle mass (Fry et al., 2010) and in athletes
to improve performance (Takarada et al., 2002; Cook, Murphy & Labarbera, 2013)
or to accelerate post-surgical rehabilitation (Ohta et al., 2003). Increases in muscle
hypertrophy following low load BFRR training are well documented and are one of
the primary reasons behind utilizing this form of exercise (Wernbom, Augustsson &
Raastad, 2008). Interestingly, despite lower mechanical stress to the tissues, favourable
adaptations in bone turnover have also been demonstrated with BFRR training (Kara-
bulut et al., 2011).
However, the positive adaptation of muscle to BFRR training seems to extend bey-
ond mimicking hypertrophic effects of high-resistance training. Namely, improvements
in vascular function (Patterson & Ferguson, 2010; Hunt, Walton & Ferguson, 2012;
Hunt, Galea, Tufft, Bunce & Ferguson, 2013; Evans, Vance & Brown 2010), enhanced
oxygen delivery and muscle endurance (Takarada, Sato & Ishii, 2002; Kacin & Strazar,
2011) as well as cardiorespiratory endurance (Abe et al., 2010; Park et al., 2010) have
been also reported with BFRR training. A recent case study even reports of an increa-
sed rate of healing in patient with osteochondral fracture (Loenneke, Young, Wilson &
Andersen, 2013b).
An increasing number of published research supports the efcacy of the technique,
whereas its safety has not been extensively studied. Similar to the use of surgical tour-
niquets on limbs of resting patients (Fitzgibbons, DiGiovanni, Hares & Akelman, 2012;
Estebe, Davies & Richebe, 2011) the major concerns are due to (a) a mechanical injury
to the skin, muscle, and peripheral nerves and (b) venous thrombosis due to vascular
damage and disturbed hemodynamics, but also (c) augmented arterial blood pressure
(ABP) responses due to combined high body exertion and increased peripheral vascu-
lar resistance induced by the tourniquet. In addition, ischemic-reperfusion injury with
local or systemic effect may also play a role. The only epidemiological study available
has shown a surprisingly low occurrence of any adverse effects of BFRR training other
than skin bruising, in various populations in Japan (Nakajima et al., 2006). General and
specic health concerns with BFRR training in healthy people have been reviewed in
depth by Manini and Clark (2009), Loenneke, Wilson, Wilson, Pujol & Bemben (2011)
and Pope, Willardson & Schoenfeld (2013). The present review thus addresses safety
and efciency of BFRR training from clinical perspective, in regard to a complex in-
terplay of various extrinsic (tourniquet system and exercise) and intrinsic (anthropo-
metrics, medical history and life style) factors. Based on reviewed evidence and our
clinical experience with BFRR training in injured and operated athletes we set about
developing a risk assessment tool. The tool will allow physiotherapists and non-medi-
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cal staff such as strength and conditioning coaches, to manage the risk to the athletes
whilst allowing them to benet from an effective technique.
METHODS
Methods of literature review and clinical commentary were combined when prepa-
ring this manuscript. The search of scientic literature published in English language
was performed until March 2015 in various electronic databases (PubMed, WoS, ME-
DLINE, PEDro and ScienceDirect) by the following key words and phrases: blood ow
restricted exercise, ischemic training, reperfusion injury, safety and efciency of pneu-
matic tourniquets and health risk assessment for vascular occlusion. Initial search gave
1582 results which were rened by use of various key word combinations and addition
of new phrases most frequently associated with the topics of interest (rhabdomyolysis,
reperfusion injury, contour and cylindrical cuffs, nerve injury etc.). The second selec-
tion produced 133 publications, which were further reduced to 83 entries, based on
abstract content match with the topics, type of publication, research type and design,
sample size and full text availability. Case studies or reports and book chapters were
included only for the topics not studied by RCTs or other controlled cohort studies.
PROPOSED MECHANISMS OF MUSCLE ADAPTATION
TO BFRR TRAINING
How the positive training adaptations reviewed and discussed above are elicited
by muscle blood ow occlusion during exercise remains debatable. The proposed me-
chanisms were reviewed on several occasions, most recently and in-depth by Pope et
al. (2013) and Heitkamp (Heitkamp, 2015), who listed all hypothetical physiological
triggers identied so far: (a) hypoxia-induced additional or preferential recruitment of
fast-twitch muscle bers, (b) greater duration of metabolic acidosis via the trapping
and accumulation of intramuscular protons (H+ ions) and stimulation of metaborecep-
tors, possibly eliciting an exaggerated acute systemic hormonal response, (c) external
pressure-induced differences in contractile mechanics and sarcolemmal deformation,
resulting in enhanced growth factor expression and intracellular signalling, (d) me-
tabolic adaptations to the fast glycolytic system that stem from compromised oxygen
delivery, (e) production of reactive oxygen species (ROS) that promotes tissue growth,
(f) gradient-induced reactive hyperemia after removal of the external pressure, which
induces intracellular swelling and stretches cytoskeletal structures that may promote
tissue growth, and (g) activation of myogenic stem cells with subsequent myonuclear
fusion with mature muscle bers. Given that detailed review of all these mechanisms is
not the primary aim of the present review, only mechanisms most closely related to the
safety of tourniquet application will be discussed in the following.
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When performing BFRR exercise with a pneumatic tourniquet system, a tourniquet
cuff is applied to the proximal part of the upper or lower limb and inated to the set
pressure. With gradual mechanical compression of all soft tissues under the cuff, a
reduction in vascular diameter is achieved, resulting in occluded venous and reduced
or completely occluded arterial blood ow to the muscles at and distal to the cuff.
During muscle contraction, an increase in intra-muscular pressure is generated under
the pressurized cuff, further disturbing muscle blood ow. In case of isometric muscle
contraction, the contraction-induced muscular pressure is basically constant, whereas
during concentric/eccentric contractions it changes in a cyclical manner. If a rigid cuff
with no regulation of pressure is used, effective tourniquet pressure during contracti-
ons is ~50 % higher than the set value, with ~65−75 % variation between concentric
and eccentric phase of contraction (Figure 1). Depending on the cumulative degree of
blood ow reduction and exercise intensity, variable levels of muscle edema, ischemia
and hypoxia develop in the muscle during the exercise. Following deation of the tour-
niquet, reperfusion of the limb takes place.
Figure 1: Cyclic changes in rigid contour tourniquet cuff (13 cm wide) pressure during
ten concentric / eccentric knee-extension contractions performed at 20 % 1RM by a
representative subject. Set pressures were (A) 100 mmHg and (B) 150 mmHg, with no
pressure regulation provided during exercise (author’s unpublished data).
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There is a lack of a most optimal degree of venous and arterial blood ow reduc-
tion for muscle conditioning is. Although sound experimental evidence is still scarce,
it can be assumed that two distinct changes in muscle hemodynamics are achieved
during the dynamic leg exercise, by inducing either predominant venous-lymphatic oc-
clusion (tourniquet pressure of ~60 mmHg) or intermittent complete arterial occlusion
(≥150 mmHg). In the case of predominantly venous occlusion (VO), blood inow to
the muscle is not compromised, resulting in progressive rise in venous pressure (Iida
et al., 2007). Given that capillary pressure is four times more sensitive to increased ve-
nous pressure, the result is augmented capillary ltration. Fluid shift from vasculature
to extracellular compartments, combined with completely blocked lymphatic outow,
results in soft-tissue edema and increased interstitial uid pressure (Levick & Michel,
2010). Consequently, some of the uid is forced across the sarcolemma into the intra-
cellular compartment, along with non-selective transport of various smaller molecules.
Due to progressive congestion of blood in the muscle during the exercise, substantial
metabolite accumulation and tissue hypoxia are eventually developed. In contrast, the
resistance on both sides of the capillaries is equally reduced during complete arterial
occlusion (AO) hence no detectable muscle swelling occurs during dynamic exercise.
It does however substantially increase hypoxia and metabolic stress in the muscle and
hence post-ischemic hyperemia. As shown by near-infrared spectroscopy, a substantial
hypoxia of vastus lateralis muscle is induced after only a few initial contractions with
intermittent complete AO (tourniquet pressure ≥230 mmHg, width 13 cm) (Kacin &
Strazar, 2011). Upon the release of tourniquet, augmented reperfusion (active hyper-
emia) is driven by accumulated metabolites in the muscle cells which increases pres-
sure gradient across sarcolemma and further cell swelling. It is speculated that cell
swelling per se induces muscle protein synthesis (Loenneke, Fahs, Rossow, Abe &
Bemben, 2012a) as it is the case with other type of cells (Lang et al., 2000). Further-
more, signs of muscle damage and prolonged (up to 48 hrs.) sarcolemmal permeability
were demonstrated after only one bout of BFRR exercise (Wernbom, Paulsen, Nilsen,
Hisdal & Raastad, 2012), which suggests a thin line between hypertrophic stimulus and
potential muscle injury. A reduced muscle compliance to palpation can be noted after
BFRR exercise, and subjects describe muscle as “hard” or “pumped up” for a short
period after BFRR (authors’ unpublished observations). It was also demonstrated that
transient increase in sarcolemma permeability and cell swelling is an important trigger
of hypertrophy and augmented satellite cell activation (Nielsen et al., 2012). Also, mus-
cle hypertrophy and strength gains are shown to have a good correlation (r=0.60-0.88)
with metabolic stress (Takada et al., 2012; Sugaya, Yasuda, Suga, Okita & Abe, 2011).
Importantly, metabolic perturbation induced by disrupted hemodynamics increases
the magnitude of muscle activation, presumably of fast-twitch bers, during low load
BFRR training compared to free blood ow training of same intensity (Yasuda et al.,
2009; Yasuda et al., 2014; Yasuda, Loenneke, Ogasawara & Abe, 2013). This is seen as
one of the key acute adaptations which lead to strength gains following low load BFRR
training (Takarada et al., 2000).
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However, based on our clinical observations with preoperative conditioning of 23
athletes scheduled for ACL reconstruction, the same degree of blood ow restriction
does not have the same effect on muscle activation and performance of power or endu-
rance trained individuals of different build, even when tourniquet pressure is corrected
for resting arterial pressures and leg circumference by Graham’s formula (Graham,
Breault, McEwen & McGraw, 1993). The number of repetitions performed was up to
40 % higher in endurance compared to power athletes (authors’ unpublished observa-
tions). This may be due to different proportions of type I and type II muscle bers and,
hence, different effect of blood deprival on muscle fatigability. A similar observation
was recently reported by Downs et al. (2014), who noted a ~10-15% lower rate of fa-
tigue, calculated from the decrease in number of repetitions, for ankle plantar exors
compared to knee extensors at the same vascular occlusion, which was attributed to
profoundly different muscle composition between muscle groups (Gregory, Vanden-
borne & Dudley, 2001). To provide sufcient training stimulus of BFRR exercise re-
gardless of training status and muscle composition, our patients / athletes perform each
exercise set to volitional failure. This, however, substantially increases the whole body
exertion and cardiac load, thus patients with a history of cardiorespiratory disease must
be excluded. Optimization of exercise parameters for BFRR training in different patient
populations needs to be systematically addressed in further investigations.
POTENTIAL SAFETY AND EFFICIENCY ISSUES WITH BFRR TRAINING
Long-lasting (>30 min) AO induced by pneumatic tourniquets is routinely used dur-
ing limb surgery in order to prevent bleeding. Tourniquet pressure above 170 mm Hg
for upper and 270 mm Hg for lower limbs is usually used, which in combination with
prolonged constant compression poses a threat of mechanical and, upon the release of
tourniquet, ischemia-reperfusion injury of the vascular, neural, metabolic and musculo-
skeletal systems (Fitzgibbons et al., 2012). Ischemia is the reduction of blood supply to
a tissue which results in a lack of oxygen and substrates for cellular metabolism (Ames
& Nesbett, 1983). A prolonged complete ischemia and a rapid reperfusion of tissues
upon the release of blood ow are the causes of reperfusion injury (Estebe, Davies &
Richebe, 2011; Wakai et al., 2001; Hughes, Hendricks, Edwards & Middleton, 2010;
Hughes et al., 2007). It is well known that irreversible skeletal muscle damage occurs
after three hours of ischemia in normothermic conditions (Blaisdell, 2002; Pedowitz et
al., 1991) but adverse cellular events begin much earlier. Research shows that reperfu-
sion injury causes cell apoptosis, presumably by negative inuences on microcircula-
tion, subsequent local inammatory response and production of reactive oxygen spe-
cies (Blaisdell, 2002; Carden & Granger, 2000). In contrast, short episodes of ischemia
− reperfusion are speculated to be the trigger for cellular adaptation to BFRR training
(Wernbom et al., 2008; Manini & Clark, 2009) and were demonstrated to have both
a cardio-protective (Zhu et al., 2013) and a muscle performance enhancing effect (de
Groot, Thijssen, Sanchez, Ellenkamp & Hopman, 2010). However, an optimal protocol
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
for effective and safe BFRR training remains elusive. Strength gains and hypertrophy
comparable to standard high load strength training were reported with various combi-
nations of exercise and tourniquet parameters (see (Wernbom et al., 2008; Loenneke,
Wilson, Marin, Zourdos & Bemben 2012c) for review). In addition, enhanced muscle
endurance capacity and hemodynamics were demonstrated with a combination of ei-
ther extremely low load (40 − 50 RM) exercise and high tourniquet pressures (150
230 mmHg, width 13-15 cm) with reperfusion between four sets for lower limbs (Kacin
& Strazar, 2011; Evans et al., 2010) or low to medium load (25 % and 50 % 1RM) ex-
ercise with low pressure (110 mmHg) without reperfusion between three sets for lower
and upper limbs (Patterson & Ferguson, 2010; Hunt et al., 2012; Hunt et al., 2013).
Morphologic adaptation occurred at all levels of the vascular tree with enhanced peak
reactive hyperemia and transient improvement in artery function preceding changes in
artery structural capacity (Hunt et al., 2013). Although tourniquet pressure is usually
regarded as a key extrinsic factor of blood ow reduction, other extrinsic and intrinsic
confounding factors like 1) tourniquet width and shape (Moore, Garn & Hargens,
1987; Crenshaw, Hargens, Gershuni & Rydevik, 1988; Pedowitz et al., 1993), 2) limb
circumference (Graham et al., 1993; Tuncali et al., 2006) and 3) individual’s arterial
blood pressures (ABP) (Newman & Muirhead, 1986; Graham et al., 1993) substantially
affect the nal degree of occlusion.
Inuence of Tourniquet Cuff Design and Pressure
Various combinations of tourniquet pressure (range 50 − 230 mmHg) and cuff width
(range 3.3 − 20.5 cm) were used in BFRR exercise studies. Although tourniquet pres-
sures and exposure times used are lower compared to the ones in surgery, the stretching
and shear forces in the tissue are most likely to be much higher due to muscle contrac-
tions under pressurized tourniquet cuff. As shown in Figure 1, the cuff pressure during
concentric phase of contraction peaks ≥ 50 % above the value set on the resting muscle
prior to the exercise, which reects a very high increase in intramuscular forces at the
site of cuff compression. Tourniquet system that provides a fast responsive and accu-
rate cuff pressure regulation during muscle contractions is thus essential for a safe and
efcient application of BFRR exercise.
In a resting limb, the same reduction of blood ow can be achieved using a wider
tourniquet cuff at much lower pressures (Moore et al., 1987; Crenshaw et al., 1988;
Pedowitz et al., 1993). Likewise, contoured (cone) cuffs induce arterial occlusion at
lower pressures than straight (cylindrical) ones (Younger, McEwen & Inkpen, 2004;
Pedowitz et al., 1993). Given that the shape and width of the cuff inuence pressure
distribution and sheer forces in the underlying muscle tissue (Pedowitz et al., 1991), us-
ing the lowest pressures possible to achieve the desired training effect should minimize
the risk of soft tissue damage. Cuff width, shape and pressure also have an important
inuence on pain provocation and, hence, patient comfort during the application. When
compared at the same ination pressure (SBP×1.3≈160 mm Hg), wide rigid cuffs (13.5
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Alan KACIN, Benjamin ROSENBLATT, Tina GRAPAR ŽARGI, Anita BISWAS: SAFETY CONSIDERATIONS WITH BLOOD ..., 326
cm) provoke somewhat higher pain levels (~2 points on Borg’s CR-10) and perception
of effort (~1.5 point on 6 − 20 Borg’s scale) during lower limb exercise than narrow
belt-like elastic cuffs (5 cm) (Rossow et al., 2012). Given that at the same pressure a
wider cuff induces more blood-ow restriction, such comparisons may be deceptive.
As demonstrated already by Estebe, Le Naoures, Chemaly and Ecoffey (2000) on
resting upper limbs, wider cuffs (14 cm) indeed provoke more pain than narrow cuffs
(7 cm) when compared at same absolute pressure (~260 mm Hg), but less pain when
compared at individual occlusion pressure. The latter was on average 55 mmHg lower
with wider cuffs (202 mmHg for narrow and 147 mmHg for wide cuffs) (Estebe et al.,
2000), suggesting that wider cuffs might in fact provoke less discomfort and pain for
the same occlusion stimulus also during the exercise. Given that different pressures and
conditions (exercise vs. rest) were scrutinized in these studies, more research is needed
in this regard.
In many published BFRR exercise studies, there is a lack of detailed technical char-
acteristics of the tourniquets and pressure systems used. The degree of blood ow re-
duction is, thus, difcult to estimate, but according to signicant differences in various
confounding factors listed above, vast variations between and within studies are likely.
Meta-analysis of well-designed and controlled BFRR studies (Loenneke et al., 2012c)
revealed a difculty in estimating the actual impact of various tourniquet pressures on
gains in muscle mass and strength, which is not surprising due to large variations in
tourniquet systems used. There is a clear need for a systematic study of differences in
intramuscular responses induced by various tourniquet systems used for BFRR training.
Impact of Limb Anthropometrics on Pressure Transmission
Transmission of pressure from a tourniquet to the underlying tissues showed to be
exponentially inverse to extremity circumference (Tuncali et al., 2006) and to the ratio
between circumference and tourniquet cuff width (Graham et al., 1993). Similarly, sig-
nicant negative correlations between tissue oxygenation and leg lean body mass, total
lean body mass, and thigh circumference were reported by Karabulut, McCarron, Abe,
Sato & Bemben (2011b). Furthermore, it was established that as much as ~80% of vari-
ability in the occlusion pressures with the use of rigid wide cuffs can be explained by
the ratio of muscle to subcutaneous fat cross-sectional areas and only ~20% by either
systolic (SAP) or diastolic (DAP) blood pressure (Loenneke et al., 2012d), which coun-
ters the previous reports (Newman & Muirhead, 1986; Graham et al., 1993). With an
application of elastic belt-like tourniquet cuffs, the total variance in occlusion pressures
explained by anthropometrics was much smaller, and was even non-signicant for SAP.
Taken together, the transmission of cuff pressure to the center of the limb, where the
majority of large blood vessels is located, seems to be negatively related to the limb
circumference and positively related to the cuff width.
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CONSIDERATIONS FOR CLINICAL SCREENING AND RISK
ASSESSMENT
The use of BFRR training for musculoskeletal rehabilitation is relatively new and
rapidly evolving. To improve our understanding of the risks associated with this form
of training, a thorough screening and regular auditing processes need to be established
by all users of the technique.
We consider that a high quality screening process, including a medical practitioner
is essential to safe guard against potential adverse reactions associated with this form of
exercise. The purpose of a screen is to lter out those patients that may be at increased
risk of injury for medical or other reasons. A further purpose is to identify the factors
which will reduce the risk of injury to potentially overstressed structures reviewed be-
low. Considering the safety aspects of BFRR training using these principles relies on a
comprehensive personal medical, social and family history. Particular attention needs
to be paid to any condition or lifestyle activity that may have impact on any of the
systems outlined below. In the development of a risk assessment tool we addressed the
following principles:
identication of the structures affected by blood ow restriction;
identication of which subjects / patients may be at higher risk from the potenti-
al negative effects of BFRR training and determination of the level of precaution
required;
development of an easy-to-use risk assessment tool;
review of any adverse reactions;
review and update of the risk assessment tools as necessary.
In the process of identifying potential risks, the structures which may be affected by
the application of a tourniquet must be considered. We addressed each of these structu-
res individually when determining which medical conditions may increase the risk of
exposure to BFRR exercise.
Skin and subcutaneous tissues
Pressure necrosis and frictional burns can occur due to inadequate padding, poor
application of the tourniquet, and movement of the fully inated tourniquet over bare
skin. Soft wrinkle-free padding should be used below the cuff (Van der Spuy, 2012) to
avoid these issues. Stretch sleeves made of two-layer elastic material were shown to
provide the most effective protection against skin injury during application of surgical
tourniquets (Olivecrona, Tidermark, Hamberg, Ponzer & Cederfjäll, 2006). Frictional
burns and pinching are more likely to occur during BFRR exercise if no padding is
used.
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Musculoskeletal system
In the musculoskeletal system, consideration must be given to the effect of BFRR
on muscle and joints. Excessive and unaccustomed exercise may result in muscle dam-
age and delayed-onset soreness. Both of these have also been reported after a low load
BFRR training (Umbel et al., 2009), but this may be evidence of the adaptations nec-
essary for a training effect rather than an adverse response. It was shown that exces-
sive pressures combined with a wide tourniquet can provoke paraesthesia in the thighs
during the exercise. In addition, suppressed muscle hypertrophy in vastus intermedius
muscle with signs of atrophy at the site of tourniquet compression were observed after
four weeks of BFRR training (Kacin & Strazar, 2011).
Lack of blood perfusion to a limb and extreme physical exertion are both well-
known causes of rhabdomyolysis. This is a clinical syndrome resulting from skeletal
muscle damage and the release of potentially toxic substances into the circulation (Alli-
son & Bedsole, 2003). It may be caused by trauma or muscle hypoxia and manifests as
muscle pain and weakness. There was also a case report of rhabdomyolysis following
the initial exposure to BFRR training (Iversen & Rostad, 2010). Other potential causes
of rhabdomyolysis, which need to be excluded prior to BFRR training, are outlined in
Table 1.
Consideration must, therefore, be given in the case when other conditions associ-
ated with rhabdomyolysis are present. This includes restricted caloric intake (particu-
larly with low levels of potassium, phosphate and magnesium), a history of severe heat
illness / injury, a recent muscle trauma or a crush injury. Caution must, therefore, be
taken in individuals who lack any previous training history as unaccustomed exercise
can also be associated with an increased risk of rhabdomyolysis.
The personal experience of the authors is of the use of BFRR in the rehabilitation
of musculoskeletal injuries. When determining potential risk factors for the use of this
technique in patients after ACL reconstruction with or without partial menisectomy
(N=32), we were concerned about the potential negative effect on post-surgical patients
with a swollen joint, due to congestion of tissues or swelling that may result from the
external restriction of blood and lymphatic vessels. This may also have impact on those
with an inammatory arthropathy, synovitis, haemarthrosis or septic arthritis. Indeed,
in case of post-surgical synovitis (N=1) or haemarthrosis (N=1) exacerbation of symp-
toms were induced by BFRR (authors’ unpublished observations), hence, alternative
forms of training should be considered.
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
Table 1: Types and causes of rhabdomyolysis. (Allison & Bedsole, 2003)
Type Cause
Trauma or muscle
compression
Crush syndrome
Prolonged immobilization
Non-traumatic
exertional
rhabdomyolysis
Unaccustomed exertion in untrained individuals
Hyperthermia: malignant hyperthermia, neuroleptic malignant syn-
drome
Metabolic myopathies: mitochondrial myopathies, McArdles etc
Non-traumatic and
non-exertional
rhabdomyolysis
Drugs: alcohol, heroin, cocaine, amphetamines, methadone, and D-
-lysergic acid diethylamide (LSD), antipsychotics, statins, selective
serotonin reuptake inhibitors, zidovudine, colchicine, lithium, anti-
histamines, and several others
Toxins: metabolic poisons, such as carbon monoxide, snake venoms,
insect venoms, including wasp and bee stings, mushroom poisoning
Viral infections: acute viral infections (eg inuenza A and B),
coxsackievirus, Epstein-Barr, herpes simplex, parainuenza, adeno-
virus, echovirus, human immunodeciency virus, and cytomegalo-
virus
Bacterial infections: bacterial pyomyositis legionella, tularemia,
streptococcus and salmonella, E. coli, leptospirosis, coxiella burnetii
(Q fever), and staphylococcal infection
Electrolyte disorders: hypokalemia, hypophosphatemia,
diabetic ketoacidosis or nonketotic hyperglycemia, hypophosphate-
mia, hypocalcemia hyponatremia hypernatremia
Inammatory myopathies: inammatory myopathies, dermatomyo-
sitis, polymyositis
Endocrine disorders: diabetes, hyper and hypo-thyroidism
Cardiac function and arterial blood pressure
In healthy population, a substantially higher exercise-induced increase in SAP, DAP
and mean ABP and heart rate (HR) compared to free ow exercise were found after two
or more subsequent sets of BFRR exercise with no reperfusion between the sets (Renzi,
Tanaka & Sugawara 2010; Vieira, Chiappa, Umpierre, Stein & Ribeiro 2013; Takano
et al., 2005). As demonstrated by Renzi et al. (2010), increased HR during blood ow
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Alan KACIN, Benjamin ROSENBLATT, Tina GRAPAR ŽARGI, Anita BISWAS: SAFETY CONSIDERATIONS WITH BLOOD ..., 326
restricted walking exercise (cuff pressure 160 mmHg, width not reported) compensates
for a compromised venous return and, hence, reduced the stroke volume, which results
in a three-fold greater index of myocardial oxygen demand. A report by Vieira et al.
(2013) corroborates the exaggerated heart rate (HR) and ABP responses to single-arm
BFRR exercise (cuff pressure 120 mmHg, width not reported) performed at 30 % 1RM
in both young and older healthy men. Similar ndings were recently reported for uni-
lateral leg BFRR exercise with two different tourniquet cuff pressures (1.3×DAP and
1.3×SAP, width 6 cm), with the exception of an attenuated rather than augmented HR
response (Downs et al., 2014). It appears that BFRR exercise can either increase or
decrease a normal HR response, depending on the interplay between cardio accelera-
tion driven by increased sympathetic drive and reduced stroke volume and cardio de-
celeration driven by increased cardiac afterload and decreased preload. These ndings
show that a lack of reperfusion during the short rest between exercise sets progressively
exacerbates cardiac load and cardiovascular demand. However, if exercise protocols
are not matched for work and intensity, but performed until volitional failure, acute HR
and ABP responses are similar between BFRR and free ow exercise (Loenneke et al.,
2012b; Kacin, Strazar, Palma & Podobnik 2011; Kacin & Strazar, 2011). From clinical
perspective it is important that cardiac and blood pressure responses to low-load BFRR
exercise are still signicantly lower than during the standard high-load resistance ex-
ercise despite a higher perception of exertion (Poton & Doederlein Polito, 2014). The
latter is apparently driven predominantly by peripheral sensations from the occluded
limb. Given that a low load BFRR exercise does not induce post-exercise hypotension
comparable to a free ow high load resistance exercise (Rossow et al., 2011), it appears
that an overall level of exertion determines systemic cardiovascular responses, more
than blood ow restriction per se.
The safety of BFRR exercise in patient populations at increased risks for cardio-
vascular events has not been systematically studied so far. A recent pilot study of nine
patients with stabile ischemic cardiac disease (Madarame, Kurano, Fukumura, Fukuda
& Nakajima, 2013) also revealed an augmented exercise-induced increase in heart rate
and plasma noradrenaline concentration during the BFRR exercise, although the sub-
jects performed a xed number of repetitions per set rather than exercising to volitional
failure. Despite an increased body exertion, no warning signs of any cardiovascular
events were observed in these patients (Madarame et al., 2013). Thus, subjects with a
history of or an increased risk of cardiovascular disease should be thoroughly screened
prior to their inclusion to BFRR training program and closely monitored for excessive
HR and ABP responses during the exercise. Exercise is advised not to be performed to
volitional failure and should also allow longer and more frequent reperfusion during
multiple sets. In our experience, six sets of BFRR with 45 − 60s reperfusion between
two consecutive sets is better tolerated by ACL decient (N=32) patients or those with
knee osteoarthritis (N=12), than three or four sets without reperfusion. It can be assu-
med that such BFRR exercise protocol is also more appropriate for people with modera-
te risk for cardiovascular events. An alternating exercise for agonistic and antagonistic
muscles can further reduce the stress, but most likely reduces the BFRR exercise effect.
16
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
Little is known about the long-term effects of BFRR training on cardiovascular
regulation. A study of Kacin and Strazar (2011) revealed a small, but signicant in-
crease in pre-exercise resting diastolic arterial pressure after a 4-week BFRR training
program, which may indicate chronically elevated levels of stress hormones due to
repetitive high body exertion in healthy individuals. This observation warrants a further
investigation both in healthy individuals and cardiac patients.
Vascular considerations
Overall, there is evidence that there are vascular benets to the use of blood ow
restriction (Patterson & Ferguson, 2010; Hunt et al., 2012; Hunt et al., 2013), however,
blood ow through vessels is affected by a number of factors including the vessel diam-
eter and blood turgidity. Any condition that interferes with a ‘normal’ blood ow may
contribute to and compound these compressive effects by impacting on the turgidity of
the blood. It stands to reason that any condition affecting blood ow through the limb
to be trained and the wider cardiovascular system may show impact on the risk to the
patient. Nakajima estimated the risk of venous thrombus to be 0.055 % in their epide-
miological study in Japan (Nakajima et al., 2006), nonetheless it is very low, it is a real
risk. Consideration must therefore be given to a personal or family history of conditions
affecting blood ow through local vessels or the wider cardiovascular system. These
are outlined in Table 2.
Table 2: Medical and social factors which may affect limb muscle blood ow.
Lifestyle
Travel
Periods of immobilization
Medication
Smoking
Personal Medical
History
Clotting disorders
Connective tissue disorders
Thrombosis (deep vein, pulmonary embolus, stroke)
Traumatic injury to blood vessels or nerves, compartment syndrome,
fractures or surgery
Non traumatic injury etc. diabetes/ hypertension/ peripheral vascular
disease
Liver/ renal disease
Pregnancy
Family History
Clotting disorders
Connective tissue disorders
Sickle cell anemia
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Alan KACIN, Benjamin ROSENBLATT, Tina GRAPAR ŽARGI, Anita BISWAS: SAFETY CONSIDERATIONS WITH BLOOD ..., 326
Despite the potential risk, there is a growing body of evidence that BFRR exercise
does not increase risk of venous thrombosis, at least in healthy individuals. A single
bout of blood ow restriction exercise show to augment brinolytic potential (Clark et
al., 2011) without affecting coagulation (Clark et al., 2011; Madarame et al., 2010; Fry
et al., 2010) and inammatory responses (Clark et al., 2011). The question whether this
holds true also for patients with increased risk for cardiovascular events has not been
systematically studied yet. A recent pilot study of Madarame et al. (2013) showed that
hemostatic and inammatory responses are not signicantly increased by a single bout
(4 sets without reperfusion) of BFRR exercise performed at 20 % 1RM (5 cm wide
elastic cuff with pressure 200 mmHg) in patients with stabile ischemic heart disease.
However, these results should not be directly extrapolated to other patient populations
and the interpretation must be taken with caution; the number of subjects was rather
small and the degree of blood ow restriction must have been different between subject
at a given tourniquet pressure.
Neural Considerations
Disruptions in peripheral nerve function may be due to both compression and local
asphyxiation (Ochoa, Fowler & Gilliatt, 1972). Under lower levels of compression,
disruptions are usually due to local ischemia (Brown & Brenner, 1944) unless the dura-
tion of compression is prolonged, in which case disruption is due to the pressure ef-
fects alone. In experiments looking into the effects of tourniquet pressure on the tissues
beneath it, higher pressures have been shown to cause localized conduction block as a
result of mechanical deformation nerve bers (Ochoa, Fowler & Gilliatt, 1972), with
large nerve bers being affected more than those that are smaller (Bolton & McFarlane,
1978; Larsen & Hommelgaard, 1987). Lundborg, Gelberman, Minteer-Convery, Lee &
Hargens (1982) reported hand numbness resulting from tourniquet compression of arm
likely due to nerve ischemia and conduction block, with similar numbness reported also
in the thigh during the BFRR exercise by Kacin and Strazar (2011). Such acute nerve
compression, however, does not usually have a long-term negative effect on nerve con-
duction velocities, at least in healthy adults (Clark et al., 2011).
It is well known that peripheral nerve function (both sensory and motor) in diabetics
is reduced early in the disease and that this is also likely to be due to ischemia (Greger-
sen, Servo, Borsting & Theil, 1978) although the deterioration in nerve function can
be reduced by maintaining good control of blood sugars. Therefore, the relative risk of
nerve injury in diabetics using BFRR may be considered to be higher than in the gen-
eral population. In assessing risk, it also stands to reason that any history of previous
disruption to the peripheral nervous system particularly if due to compression, places a
patient at a higher risk of re-injury during BFRR training. Caution is particularly advi-
sed in paralympic athletes with a spinal cord injury, direct peripheral nerve injury (such
as post-traumatic joint dislocation) or a complex regional pain syndrome.
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
Metabolic and systemic conditions
There is good evidence that BFRR training is benecial in diabetics (Satoh, 2011).
However, besides the potential risk of adverse neural effects described above, there is a
well-documented increased risk of peripheral vascular disease with disordered regula-
tion of cutaneous blood ow and increased susceptibility to leg ulcers and limb loss
in this population (Sima, Thomas, Ishii & Vinik, 1997). There is an argument that any
method that restricts blood ow may compound these issues. In athletes with diabetes,
there is a likelihood of fewer other confounding risk factors than in non-athletic dia-
betic patients. We would, nevertheless, consider that, before using this form of training
in a diabetic athlete, a medical assessment of the overall risk versus benet for the
individual should be undertaken. In addition, based on the extensive Kaatsu work in
Japan (Nakajima et al., 2006) the risks of adverse effects are not as high as may be rst
considered, so this valuable method of training should not be automatically excluded.
In other diabetic populations the risk may be higher and each person should be assessed
individually as to their suitability.
Paralympic athletes may include those with Duchene muscular dystrophy. This is
a condition in which the protein, dystrophin, is absent and causes an increase in sarco-
lemma damage in response to the exercise (Markert, Ambrosio, Call & Grange, 2011).
Loenneke et al. (2013a) suggested that BFRR may be a good way to improve symptoms
in this group of patients for whom exercise may improve their condition, but may also
be associated with muscle damage, as discussed above. In considering the use of BFRR
training in paralympic athletes and other people with this condition, sound medical
reasoning was used in the authors’ clinical practice whilst acknowledging the absence
of strong medical evidence as to its risks or benets.
Other less common conditions for consideration and rarely seen in our popula-
tion, include genetic muscle diseases comprising familial paroxysmal rhabdomyolysis,
McArdles, myopathies, and severe hypothyroidism. The only published evidence on
these conditions is a case study in Inclusion Body Myositis in which a patient gained
improvements in strength and motor function after BFRR training with no adverse ef-
fects on his disease (Gualano et al., 2010). Certain medication such as statins and some
medications for Parkinson’s disease are also associated with this, which also increases
the risk of adverse effects (Table 1).
DEVELOPING A RISK ASSESSMENT TOOL
Considering the safety aspects of BFRR training using these principles relies on
a comprehensive personal, medical, social and family history. Particular attention
needs to be paid to any condition or lifestyle activity that may impact on any of the
systems outlined above. In recognition of this the following screening tool was de-
veloped (Figure 2).
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Alan KACIN, Benjamin ROSENBLATT, Tina GRAPAR ŽARGI, Anita BISWAS: SAFETY CONSIDERATIONS WITH BLOOD ..., 326
Figure 2: Clinical screening tool for risk assessment of subjects prior to their inclusion
in blood ow restricted resistance training program.
MAGNITU-
DE OF RISK MEDICAL HISTORY OR LIFESTYLE FACTOR PATIENT
RESPONSE DECISION
ABSOLUTE
Do you have a family history of clotting disorders
(e.g. SLE (lupus), haemophilia, high platelets)?
YES STOP
NO CONTINUE
Do you have level 1 hypertension (SAP ≥ 140
mmHg)?
YES STOP
NO CONTINUE
Do you have a past history of DVT or pulmona-
ry embolus?
YES STOP
NO CONTINUE
Have you suffered from a haemorrhagic or
thrombotic stroke?
YES STOP
NO CONTINUE
RELATIVE
Do you have a family history of clotting disorders
(e.g. SLE (lupus), haemophilia, high platelets)?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you smoke? YES SEEK MEDICAL ADVICE
NO CONTINUE
Are you on any medication including the contra-
ceptive pill?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have a history of injury to your arteries
or veins?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have a history to any of your nerves
(including back or neck injury)?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have diabetes? YES SEEK MEDICAL ADVICE
NO CONTINUE
Does one of your parents or siblings have dia-
betes?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have hypertension (SAP 120-140
mmHg)?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have metal work in situ? YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have any undiagnosed groin/calf pain? YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have/have you suffered from compart-
ment syndrome?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Have you had surgery in past 4 weeks? YES SEEK MEDICAL ADVICE
NO CONTINUE
Have you had a journey lasting more than 4
hours or a ight in the last 7 days?
YES SEEK MEDICAL ADVICE
NO CONTINUE
Do you have any other medical conditions inclu-
ding a history of synovitis?
YES SEEK MEDICAL ADVICE
NO CONTINUE
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ANNALES KINESIOLOGIAE • 6 • 2015 • 1
If it is considered that an athlete may benet from BFRR training, they ought to
be subjected to a series of questions to determine whether their medical history or
lifestyle may increase the risk of illness or injury when using BFRR training. The
purpose of the questions is to assess whether the athlete is at higher than normal risk
of adverse reactions or injury whilst using this form of training. The risk factors were
separated into ‘absolute’ and ‘relative’, where the following absolute risk factors were
recognized:
history or presence of clothing disorders (including SLE, hemophilia and high
plateles count);
history or presence of deep vein thrombosis (DVT) or pulmonary embolism;
history of thrombotic or haemorrhagic stroke;
presence of level 1 hypertension or higher.
If patients / athletes show an absolute risk factor then they are automatically
excluded from BFRR training. If they do not, then they are able to continue with the
assessment tool. If they showany relative risk factor, a referral is made to a medical
practitioner prior to progression with BFRR training. The tool was designed so it
can be used at the point of contact by a non-medical practitioner, but with a clear
understanding that the nal decision about the suitability of an athlete for BFRR is
ultimately a medical one.
The following precaution measures in different patient populations are suggested:
1. Where there may be an increased risk of thrombotic events screening should be
considered and at the very least, close monitoring is advised and a low threshold
maintained for using a different form of resistance training.
2. Subjects with a history or increased risk of cardiovascular disease should be
thoroughly screened prior to their inclusion to BFRR training program and clo-
sely monitored for excessive HR and ABP responses during the exercise. The
exercise not performed to volitional failure with longer and more frequent reper-
fusions allowed during multiple sets is also advised.
3. Those who may be at a higher risk of nerve injury such as diabetics should
be fully examined for evidence of current compromise and monitored for any
changes in sensation, or development of paraesthesia in the exercising limb.
In these subjects, monitoring blood glucose levels should be considered and in
those with poorly controlled diabetes, other forms of training may be advisable.
4. In all subjects, but particularly where factors that may contribute to the deve-
lopment of rhabdomyolysis exist, monitoring for excessive muscle pain and we-
akness, changes in urine color and systemic symptoms of malaise are essential
during BFRR training. Where there is a high level of suspicion, appropriate
medical advice should be sought early and training should be ceased.
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Alan KACIN, Benjamin ROSENBLATT, Tina GRAPAR ŽARGI, Anita BISWAS: SAFETY CONSIDERATIONS WITH BLOOD ..., 326
CONCLUSIONS
Tourniquet design and pressure and whether a patient / athlete is at a high risk of
adverse reactions are the two key considerations which can be managed to increase the
safety and efciency of BFRR training. A pneumatic tourniquet is very easy to use, but
is a rather crude method of blood ow restriction, hence, a safe and efcient applica-
tion can be provided only by well-controlled tourniquet pressure on tissues. The degree
of blood ow reduction and tissue compression induced by pneumatic cuffs during
dynamic exercise most likely varies greatly between subjects in published studies, thus,
precise parameters for a safe and efcient application cannot be established from avai-
lable data. Tourniquet pressure during BFRR training should be set individually, where
at least subject’s limb circumference and composition (skinfold), arterial blood pres-
sures and cuff design (width and shape) are to be taken into the account. We consider
that a high quality screening process including a medical practitioner is the best way to
safeguard against adverse reactions associated with this form of exercise. To improve
our understanding of the risks associated with BFRR training, a thorough and regular
auditing process needs to be established.
Conicts of interest
Authors declare no conict of interest or nancial benet connected with this
manuscript.
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... For all populations, correct application and safety in training are important (Sato, 2005;Loenneke et al., 2011;Hughes et al., 2017;Patterson et al., 2019). Regardless, for those wanting to implement a screening tool, Kacin et al. (2015) created a screening questionnaire and Rolnick et al. (2021) proposed a funnel approach which can aid health professionals in determining if the treatment is appropriate. ...
... Specific to those who have diabetes, Kacin et al. (2015) indicated the potential risk of neurological injury caused by ischemia and nerve compression particularly among those with reduced peripheral nerve function. Few studies have explored the effects of administering BFR/KAATSU training on those with osteoporosis. ...
... Nascimento et al. (2019) proposed an alternative exercise regime for resistance training using 50% of the 1 RM. In addition, Kacin et al. (2015) developed a screening tool and Rolnick et al. (2021) a funnel which may help in determining whether to administer BFR/KAATSU training. Finally, Patterson et al. (2018) suggested the use of clinical prediction rules to assess for additional risk particularly for venous thromboembolism. ...
Article
Full-text available
Purpose: The purpose of the study was to explore how individuals in the United States of America applied BFR/KAATSU devices and administered BFR/KAATSU training. In addition, the study sought to examine safety topics related to BFR/KAATSU training. Methods: The study was completed using survey research. Subjects were recruited through Facebook, email, and word of mouth. The survey was developed, piloted, and finally deployed March 22, 2021-April 21, 2021. Results: In total, 148 consented to the research; 108 completed the survey, and of those 108, 70 indicated current use with BFR/KAATSU equipment. Professions represented included athletic training, personal training, physical therapy, and strength and conditioning. Among those currently using BFR/KAATSU training (n = 70), the following results were found. The most common devices used were inflatable devices (n = 43, 61.4%). Education completed prior to device administration was formal (n = 39, 55.7%) and/or self-directed (n = 37, 52.9%). Barriers were faced by 29 (41.4%) when trying to enact training. Techniques and parameters varied during application. Screening processes were used (n = 50, 71.4%) prior to training. The devices were used to determine restrictive pressure (n = 31, 44.3%), and a supine position was used most when determining initial restrictive pressure (n = 33, 47.1%). For subsequent restrictive pressure measurements, respondents repeated the same method used initially (n = 38, 54.3%). Workload was often defined as the length of time under tension/load (n = 22, 31.4%) and exercise was directly supervised (n = 52, 74.3%). Adverse effects included bruising, lightheadedness, and cramping (n = 15, 21.4%). The devices have also been applied on those with pathology (n = 16, 22.9%). Conclusion: Those using blood flow restriction/KAATSU devices came from several professions and used an assortment of devices for BFR/KAATSU training. Individuals applied devices using a variety of parameters on populations for which efficacy has and has not been well defined.
... The available research coupled with the rapid expansion of BFR in clinical practice informs the overall safety of this intervention (3,55,57,58), and thus developing a strategy for determining when to use or not use BFR is critical. Practitioners may understand the benefits of BFR training but given there have been reported safety concerns (53,59), it's imperative they are able to quickly reason through those that are unique to BFR, as well as have a strategy for arriving at a sound clinical decision when presented with less common medical histories. ...
... While scoring systems and algorithms may be helpful in ensuring that one has been thorough in a decision-making process, one barrier these possess in determining appropriateness is they may unwarrantedly increase perceived intervention risk in a medically complex population (53,59). Clinical decision-making can be aided by pre-screening questions or questionnaires incorporated into new client/patient initial evaluation documentation, while other decisions hinge upon the subjective interview and physical examination. ...
... Performing a thorough subjective examination and medical history that includes, but is not limited to, any history of cardiovascular disease, clots, clotting disorders, or rhabdomyolysis is pertinent and may substantially shape the clinical decision-making process. Kacin et al. (59) has previously developed a screening tool and others have written somewhat extensively regarding the safety of the intervention and developed risks and contraindication lists (3,53). However, there has been no attempt to provide a thorough clinical reasoning procedure, and no tool has been validated to aid the practitioner's decision to use or not use BFR. ...
Article
Full-text available
Blood flow restriction (BFR) training is increasing in popularity in the fitness and rehabilitation settings due to its role in optimizing muscle mass and strength as well as cardiovascular capacity, function, and a host of other benefits. However, despite the interest in this area of research, there are likely some perceived barriers that practitioners must overcome to effectively implement this modality into practice. These barriers include determining appropriate BFR training pressures, access to appropriate BFR training technologies for relevant demographics based on the current evidence, a comprehensive and systematic approach to medical screening for safe practice and strategies to mitigate excessive perceptual demands of BFR training to foster long-term compliance. This manuscript attempts to discuss each of these barriers and provides evidence-based strategies and direction to guide clinical practice and future research.
... However, some possible contraindications of pBFR training should be taken into consideration, such as venous thromboembolism, peripheral vascular disease, unstable hypertension and pregnancy [51]. In this sense, the scoring system proposed by Nakajima et al. [51] or the clinical screening tool proposed by Kacin et al. [52] assist in tracking risk factors; thus, both tools can be used to assess whether the individual has any contraindication to perform pBFR training. In addition, it is recommended to check the ankle brachial index (0.90 ≤ ABI ≤ 1.40) as it is a predictor of cardiovascular disease, and most studies with pBFR do not perform this measurement. ...
Article
Full-text available
Most studies with blood flow restriction (BFR) training have been conducted using devices capable of regulating the restriction pressure, such as pneumatic cuffs. However, this may not be a viable option for the general population who exercise in gyms, squares and sports centers. Thinking about this logic, practical blood flow restriction (pBFR) training was created in 2009, suggesting the use of elastic knee wraps as an alternative to the traditional BFR, as it is low cost, affordable and practical. However, unlike traditional BFR training which seems to present a consensus regarding the prescription of BFR pressure based on arterial occlusion pressure (AOP), studies on pBFR training have used different techniques to apply the pressure/tension exerted by the elastic wrap. Therefore, this Current Opinion article aims to critically and chronologically examine the techniques used to prescribe the pressure exerted by the elastic wrap during pBFR training. In summary, several techniques were found to apply the elastic wrap during pBFR training, using the following as criteria: application by a single researcher; stretching of the elastic (absolute and relative overlap of the elastic); the perceived tightness scale; and relative overlap of the elastic based on the circumference of the limbs. Several studies have shown that limb circumference seems to be the greatest predictor of AOP. Therefore, we reinforce that applying the pressure exerted by the elastic for pBFR training based on the circumference of the limbs is an excellent, valid and safe technique.
... Consequently, the application of BFR-walking may represent a feasible and effective training modality for individuals with knee OA. Previous investigations have reported BFR exercise as safe when correctly and cautiously implemented (18,(25)(26)(27)(28)(29). However, only a single case study has investigated functional performance following BFR-walking in an individual with knee OA (30). ...
Article
Full-text available
Objective: To investigate if blood flow restricted walking exercise is feasible in patients suffering from knee osteoarthritis, and secondly to examine changes in functional performance and self-reported function. Design: Feasibility study. Patients and methods: Fourteen elderly individuals diagnosed with knee osteoarthritis participated in 8-10 weeks of outdoor walking (4 km/h, 20 minutes/session, 4 times/week) with partial blood flow restriction applied to the affected leg. Adherence, drop-outs and adverse events were registered. Timed-Up&Go, 30-s sit-to-stand performance, 40-m fast-paced walk speed, stair-climbing and Knee Osteoarthritis Outcome Score were assessed pre- and post-training. Results: Nine participants completed the intervention, while five participants withdrew of which four experienced cuff discomfort or exacerbated knee pain. Baseline BMI (p=0.05) and knee pain (p=0.06) were higher while gait performance (p=0.04) was reduced in non-completing participants. Considering completed case data, training-adherence rate was 93%, while mean knee pain in the affected leg was 0.7 on a numerical rating scale from 0-10. Functional performance improved, while self-reported function remained unchanged. Conclusion: Blood flow restricted walking exercise appeared feasible in patients with knee osteoarthritis although possibly affected by participants' baseline characteristics. Participants who completed the intervention protocol demonstrated improvements in functional performance, without any changes in self-reported function.
... Previous work has discussed the safety aspects of BfRT in detail (Loenneke et al, 2011c) and work published after the generation of this project's health screening questionnaire has created a risk assessment tool (Kacin et al, 2015). However, neither has collated and expressed the incidence of contraindications across the literature to interested readers. ...
... Moreover, the cuff pressure is of particular importance, as it is intended to induce the above mentioned mechanisms that, in turn, promote the desired physiological adaptations without potential harmful consequences (e.g., adverse cardiovascular events) (65,113). However, the supposed optimal cuff pressure is influenced by various moderator variables (113), e.g., (a) cuff width (41,81), (b) cuff material (18), (c) cuff shape (43,121), (d) individual's blood pressure (17,41,58) (e) individual limb characteristics (e.g., circumferences), (12,58), (f) body position (36,98), (g) position of the cuff tube (100), and (h) initial restriction pressure (45,46,114). Therefore, it is recommended to set the cuff pressure relative to these moderator variables (16,77,89). ...
Article
Bielitzki, R, Behrendt, T, Behrens, M, and Schega, L. Current techniques used for practical blood flow restriction training: a systematic review. J Strength Cond Res XX(X): 000-000, 2021-The purpose of this article was to systematically review the available scientific evidence on current methods used for practical blood flow restriction (pBFR) training together with application characteristics as well as advantages and disadvantages of each technique. A literature search was conducted in different databases (PubMed, Web of Science, Scopus, and Cochrane Library) for the period from January 2000 to December 2020. Inclusion criteria for this review were (a) original research involving humans, (b) the use of elastic wraps or nonpneumatic cuffs, and (c) articles written in English. Of 26 studies included and reviewed, 15 were conducted using an acute intervention (11 in the lower body and 4 in the upper body), and 11 were performed with a chronic intervention (8 in the lower body, 1 in the upper body, and 2 in both the upper and the lower body). Three pBFR techniques could be identified: (a) based on the perceptual response (perceived pressure technique), (b) based on the overlap of the cuff (absolute and relative overlap technique), and (c) based on the cuffs' maximal tensile strength (maximal cuff elasticity technique). In conclusion, the perceived pressure technique is simple, valid for the first application, and can be used independently of the cuffs' material properties, but is less reliable within a person over time. The absolute and relative overlap technique as well as the maximal cuff elasticity technique might be applied more reliably due to markings, but require a cuff with constant material properties over time.
... These include intrinsic and extrinsic factors, which are summarized elsewhere, to develop an applicable screening tool. 44,94,95 Furthermore, (2) hemodynamic and physiological responses (eg, blood pressure, heart rate), blood markers of muscle damage (eg, serum creatine kinase), and pain sensations related to the injured/operated tissue (eg, visual analogue scale) should be monitored during exercise and throughout the whole rehabilitation process. 56 As mentioned above, (3) the correct application of BFR training is of particular importance to create a safe stimulus. ...
Article
The main goal of musculoskeletal rehabilitation is to achieve the pre-injury and/or pre-surgical physical function level with a low risk of re-injury. Blood flow restriction (BFR) training is a promising alternative to conventional therapy approaches during musculoskeletal rehabilitation because various studies support its beneficial effects on muscle mass, strength, aerobic capacity, and pain perception. In this perspective article, we used an evidence-based progressive model of a rehabilitative program that integrated BFR in four rehabilitation phases: (1) passive BFR, (2) BFR combined with aerobic training, (3) BFR combined with low-load resistance training, and (4) BFR combined with low-load resistance training and traditional high-load resistance training. Considering the current research, we suppose that a BFR-assisted rehabilitation has the potential to shorten the time course of therapy to reach the stage where the patient is able to tolerate resistance training with high loads. The information and arguments presented are intended to stimulate future research, which compares the time to achieve rehabilitative milestones and their physiological bases in each stage of the musculoskeletal rehabilitation process. This requires the quantification of BFR training-induced adaptations (eg, muscle mass, strength, capillary-to-muscle-area ratio, hypoalgesia, molecular changes) and the associated changes in performance with a high measurement frequency (≤1 wk) to test our hypothesis. This information will help to quantify the time saved by BFR-assisted musculoskeletal rehabilitation. This is of particular importance for patients, because the potentially accelerated recovery of physical functioning would allow to return to their work and/or social life earlier. Furthermore, other stakeholders in the healthcare system (eg, physicians, nurses, physiotherapists, insurance companies) might benefit from that with regard to work and financial burden.
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Objective: To summarize the existing evidence on the acute response of low-load (LL) resistance exercise (RE) with blood flow restriction (BFR) on hemodynamic parameters. Data sources: MEDLINE (via PubMed), EMBASE (via Scopus), SPORTDiscus, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Web of Science, and MedRxiv databases were searched from inception to February 2022. Review methods: Cross-over trials investigating the acute effect of LLRE+BFR vs. passive (no exercise) and active control methods (LLRE or HLRE) on heart rate (HR), systolic (SBP), diastolic (DBP), and mean (MBP) blood pressure responses. Results: The quality of the studies was assessed using the PEDro scale, risk of bias using the RoB 2.0 tool for cross-over trials, and certainty of the evidence using the GRADE method. A total of 15 randomized cross-over studies with 466 participants were eligible for analyses. Our data showed that LLRE+BFR increases all hemodynamic parameters compared to passive control, but not compared to conventional resistance exercise. Subgroup analysis did not demonstrate any differences between LLRE+BFR and low- (LL) or high-load (HL) resistance exercise protocols. Studies including younger volunteers presented higher chronotropic responses (HR) than those with older volunteers. Conclusions: Despite causing notable hemodynamic responses compared to no exercise, the short-term low-load resistance exercise with BFR modulates all hemodynamic parameters HR, SBP, DBP, and MBP, similarly to a conventional resistance exercise protocol, whether at low or high-intensity. The chronotropic response is slightly higher in younger healthy individuals despite the similarity regarding pressure parameters. This article is protected by copyright. All rights reserved.
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Blood flow restriction training (BFRT) is a modality with growing interest in the last decade and has been recognized as a critical tool in rehabilitation medicine, athletic and clinical populations. Besides its potential for positive benefits, BFRT has the capability to induce adverse responses. BFRT may evoke increased blood pressure, abnormal cardiovascular responses and impact vascular health. Furthermore, some important concerns with the use of BFRT exists for individuals with established cardiovascular disease (e.g., hypertension, diabetes mellitus, and chronic kidney disease patients). In addition, considering the potential risks of thrombosis promoted by BFRT in medically compromised populations, BFRT use warrants caution for patients that already display impaired blood coagulability, loss of antithrombotic mechanisms in the vessel wall, and stasis caused by immobility (e.g., COVID-19 patients, diabetes mellitus, hypertension, chronic kidney disease, cardiovascular disease, orthopedic post-surgery, anabolic steroid and ergogenic substance users, rheumatoid arthritis, and pregnant/postpartum women). To avoid untoward outcomes and ensure that BFRT is properly used, efficacy endpoints such as a questionnaire for risk stratification involving a review of the patient’s medical history, signs, and symptoms indicative of underlying pathology is strongly advised. Here we present a model for BFRT pre-participation screening to theoretically reduce risk by excluding people with comorbidities or medically complex histories that could unnecessarily heighten intra- and/or post-exercise occurrence of adverse events. We propose this risk stratification tool as a framework to allow clinicians to use their knowledge, skills and expertise to assess and manage any risks related to the delivery of an appropriate BFRT exercise program. The questionnaires for risk stratification are adapted to guide clinicians for the referral, assessment, and suggestion of other modalities/approaches if/when necessary. Finally, the risk stratification might serve as a guideline for clinical protocols and future randomized controlled trial studies.
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The purpose of this study was to investigate the effects of tissue flossing applied to the ankle joint or to the calf muscles, on ankle joint flexibility, plantarflexor strength and soleus H reflex. Eleven young (16.6 ± 1.2 years) martial arts fighters were exposed to three different intervention protocols in distinct sessions. The interventions consisted of wrapping the ankle (ANKLE) or calf (CALF) with an elastic band for 3 sets of 2 min (2 min rest) to create vascular occlusion. A third intervention without wrapping the elastic band served as a control condition (CON). Active range of motion for ankle (AROM), plantarflexor maximum voluntary contraction (MVC), and soleus H reflex were assessed before (PRE), after (POST), and 10 min after (POST10) the intervention. The H reflex, level of pain (NRS) and wrapping pressure were also assessed during the intervention. Both CALF and ANKLE protocols induced a significant drop in H reflex during the intervention. However, the CALF protocol resulted in a significantly larger H reflex reduction during and after the flossing intervention (medium to large effect size). H reflexes returned to baseline levels 10 min after the intervention in all conditions. AROM and MVC were unaffected by any intervention. The results of this study suggest that tissue flossing can decrease the muscle soleus H reflex particularly when elastic band is wrapped around the calf muscles. However, the observed changes at the spinal level did not translate into higher ankle joint flexibility or plantarflexor strength.
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Concurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported. We examined the effects of low-intensity cycle exercise training with and without blood flow restriction (BFR) on muscle size and maximum oxygen uptake (VO2max). A group of 19 young men (mean age ± SD: 23.0 ± 1.7 years) were allocated randomly into either a BFR-training group (n=9, BFR-training) or a non-BFR control training group (n=10, CON-training), both of which trained 3 days/wk for 8 wk. Training intensity and duration were 40% of VO2max and 15 min for the BFR-training group and 40% of VO2max and 45 min for the CON-training group. MRI-measured thigh and quadriceps muscle cross-sectional area and muscle volume increased by 3.4-5.1% (P < 0.01) and isometric knee extension strength tended to increase by 7.7% (p < 0.10) in the BFR-training group. There was no change in muscle size (~0.6%) and strength (~1.4%) in the CON-training group. Significant improvements in VO2max (6.4%) and exercise time until exhaustion (15.4%) were observed in the BFR-training group (p < 0.05) but not in the CON-training group (-0.1 and 3. 9%, respectively). The results suggest that low-intensity, short-duration cycling exercise combined with BFR improves both muscle hypertrophy and aerobic capacity concurrently in young men. Key pointsConcurrent improvements in aerobic capacity and muscle hypertrophy in response to a single mode of training have not been reported.In the present study, low-intensity (40% of VO2max) cycle training with BFR can elicit concurrent improvement in muscle hypertrophy and aerobic capacity.
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The most common form of muscular dystrophy is Duchenne muscular dystrophy (DMD), which is an X-linked disorder affecting 1 in 3500 newborn males across the world. DMD is caused by the lack of dystrophin which is a protein that provides stability to the sarcolemma and is likely involved in the transmission of force between the extracellular matrix and the intracellcular contractile apparatus (Lovering and Brooks, 2013). Due to the absence of this protein, the sarcolemma is easily damaged in response to muscle contraction (Markert et al., 2012). Although there is no cure for DMD, exercise has been proposed as a possible treatment; however, the risk of muscle damage is a large concern for this population (Markert et al., 2012). Therefore, traditional strength training which includes high load eccentric contractions may need to be avoided in patients with DMD due to the susceptibility of muscle damage with lengthening contractions. In addition, although submaximal exercise may exert some benefits for this population, the low load exercise is unlikely to be an optimal stimulus for maintaining or increasing muscle function. Interestingly, there are numerous studies (>40) in healthy subjects which suggest that submaximal exercise in combination with blood flow restriction (BFR) can elicit muscle adaptations similar to that observed with higher load resistance training (Loenneke et al., 2012c) without increasing indices of muscle damage (Loenneke et al., 2011). Briefly, BFR is a stimulus commonly applied with specialized pressure cuffs placed at the top of a limb which are inflated to a set pressure throughout exercise. The pressure applied should be high enough to occlude venous return from the muscle but low enough to maintain arterial inflow into the muscle. Available evidence indicates that the pressure applied should be based on the size of the limb (i.e., bigger the limb higher the pressure) (Loenneke et al., 2012b). The proposed mechanisms (Loenneke et al., 2012a) behind the effects of low load exercise in combination with BFR on skeletal muscle include acute muscle cell swelling, increased fiber type recruitment from metabolic accumulation, decreased myostatin (48 h after last training session), decreased atrogenes (8 h post exercise), and the proliferation of satellite cells (8 days into training intervention, 3 and 10 days after cessation of training) (Nielsen et al., 2012). A recent review discussed 5 mechanisms of DMD pathology which may improve or worsen as a result of exercise training which included: (1) mechanical weakening of the sarcolemma; (2) inappropriate calcium influx; (3) aberrant cell signaling (angiogenesis); (4) increased oxidative stress; and (5) recurrent muscle ischemia (Markert et al., 2012). The purpose of this manuscript is to discuss each one of these mechanisms as it relates to what is known about low load resistance exercise in combination with BFR.
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Objective: Ischemia reperfusion injury is partly responsible for the high mortality associated with induced myocardial injury and the reduction in the full benefit of myocardial reperfusion. Remote ischemic preconditioning, perconditioning, and postconditioning have all been shown to be cardioprotective. However, it is still unknown which one is the most beneficial. To examine this issue, we used adult male Wistar rat ischemia reperfusion models to compare the cardioprotective effect of these three approaches applied on double-sided hind limbs. Methods: The rats were randomly distributed to the following five groups: sham, ischemia reperfusion, remote preconditioning, remote perconditioning, and remote post-conditioning. The ischemia/reperfusion model was established by sternotomy followed by a 30-min ligation of the left coronary artery and a subsequent 3-h reperfusion. Remote conditioning was induced with three 5-min ischemia/5-min reperfusion cycles of the double-sided hind limbs using a tourniquet. Results: A lower early reperfusion arrhythmia score (1.50 + 0.97) was found in the rats treated with remote perconditioning compared to those in the ischemia reperfusion group (2.33 + 0.71). Meanwhile, reduced infarct size was also observed (15.27 + 5.19% in remote perconditioning, 14.53 + 3.45% in remote preconditioning, and 19.84+5.85% in remote post-conditioning vs. 34.47 + 7.13% in ischemia reperfusion, p<0.05), as well as higher expression levels of the apoptosis-relevant protein Bcl-2/Bax following global (ischemia/reperfusion) injury in in vivo rat heart models (1.255 + 0.053 in remote perconditioning, 1.463 + 0.290 in remote preconditioning, and 1.461 +0.541 in remote post-conditioning vs. 1.003 + 0.159 in ischemia reperfusion, p<0.05). Conclusion: Three remote conditioning strategies implemented with episodes of double-sided hind limb ischemia/reperfusion have similar therapeutic potential for cardiac ischemia/reperfusion injury, and remote perconditioning has a greater ability to prevent reperfusion arrhythmia.
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Skeletal muscle bulk and strength are becoming important therapeutic targets in medicine. To increase muscle mass, however, intensive, long-term mechanical stress must be applied to the muscles, and such stress is often accompanied by orthopedic and cardiovascular problems. We examined the effects of circulatory occlusion in resistance training combined with a very low-intensity mechanical load on enhancing muscular metabolic stress and thereby increasing muscle bulk. Muscular metabolic stress, as indicated by the increases in inorganic phosphate (P(i)) and a decrease in intramuscular pH, was evaluated by (31)P-magnetic resonance spectroscopy during unilateral plantar-flexion at 20% of the one-repetition maximum (1-RM) with circulatory occlusion for 2 min in 14 healthy, male untrained participants (22 yr) at baseline. Participants performed two sets of the same exercise with a 30-s rest between sets, 2 times/day, 3 days/wk, for 4 wk. The muscle cross-sectional area (MCA) of the plantar-flexors and the 1-RM were measured at baseline and after 2 and 4 wk of training. MCA and 1-RM were significantly increased after 2 and 4 wk (P < 0.05, respectively). The increase in MCA at 2 wk was significantly (P < 0.05) correlated with the changes in P(i) (r = 0.876) and intramuscular pH (r = 0.601). Furthermore, the increases in MCA at 4 wk and 1-RM at 2 wk were also correlated with the metabolic stress. Thus enhanced metabolic stress in exercising muscle is a key mechanism for favorable effects by resistance training. Low-intensity resistance exercise provides successful outcomes when performed with circulatory occlusion, even with a short training period.
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The purpose of this study was to determine the difference in cuff pressure which occludes arterial blood flow for two different types of cuffs which are commonly used in blood flow restriction (BFR) research. Another purpose of the study was to determine what factors (i.e., leg size, blood pressure, and limb composition) should be accounted for when prescribing the restriction cuff pressure for this technique. One hundred and sixteen (53 males, 63 females) subjects visited the laboratory for one session of testing. Mid-thigh muscle (mCSA) and fat (fCSA) cross-sectional area of the right thigh were assessed using peripheral quantitative computed tomography. Following the mid-thigh scan, measurements of leg circumference, ankle brachial index, and brachial blood pressure were obtained. Finally, in a randomized order, arterial occlusion pressure was determined using both narrow and wide restriction cuffs applied to the most proximal portion of each leg. Significant differences were observed between cuff type and arterial occlusion (narrow: 235 (42) mmHg vs. wide: 144 (17) mmHg; p = 0.001, Cohen's D = 2.52). Thigh circumference or mCSA/fCSA with ankle blood pressure, and diastolic blood pressure, explained the most variance in the cuff pressure required to occlude arterial flow. Wide BFR cuffs restrict arterial blood flow at a lower pressure than narrow BFR cuffs, suggesting that future studies account for the width of the cuff used. In addition, we have outlined models which indicate that restrictive cuff pressures should be largely based on thigh circumference and not on pressures previously used in the literature.
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The primary objective of this investigation was to quantitatively identify which training variables result in the greatest strength and hypertrophy outcomes with lower body low intensity training with blood flow restriction (LI-BFR). Searches were performed for published studies with certain criteria. First, the primary focus of the study must have compared the effects of low intensity endurance or resistance training alone to low intensity exercise with some form of blood flow restriction. Second, subject populations had to have similar baseline characteristics so that valid outcome measures could be made. Finally, outcome measures had to include at least one measure of muscle hypertrophy. All studies included in the analysis utilized MRI except for two which reported changes via ultrasound. The mean overall effect size (ES) for muscle strength for LI-BFR was 0.58 [95% CI: 0.40, 0.76], and 0.00 [95% CI: -0.18, 0.17] for low intensity training. The mean overall ES for muscle hypertrophy for LI-BFR training was 0.39 [95% CI: 0.35, 0.43], and -0.01 [95% CI: -0.05, 0.03] for low intensity training. Blood flow restriction resulted in significantly greater gains in strength and hypertrophy when performed with resistance training than with walking. In addition, performing LI-BFR 2-3 days per week resulted in the greatest ES compared to 4-5 days per week. Significant correlations were found between ES for strength development and weeks of duration, but not for muscle hypertrophy. This meta-analysis provides insight into the impact of different variables on muscular strength and hypertrophy to LI-BFR training.
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Muscular blood flow reduction (BFR) during multiple sets of low-intensity exercise training has been shown to elicit muscle hypertrophy and strength gain. Several hypotheses have been proposed to explain the hypertrophic adaptations to low-intensity BFR exercise, which include muscle fatigue with metabolic stress. However, the change in intramuscular inorganic phosphate (Pi, an index of muscle fatigue) during multiple sets of low-intensity exercise with BFR is poorly understood. Eight men performed four sets of unilateral plantar flexion exercise (20% 1-RM) on a (31)P-magnetic resonance spectroscopy. Each subject wore a cuff (5-cm wide) on the most proximal portion of the thigh; the cuff was inflated during the exercise session at three different pressures [0 mmHg as the control ± (CON), 180 mmHg as moderate restriction (BFR-M) and 230 mmHg as high restriction (BFR-H)]. During the first and second exercise sets, the increase in Pi was higher (P<0·05) with BFR-H than with BFR-M and CON. On the other hand, the decrease in Pi was lower with BFR-H than with CON during the second and third rest periods between sets. As a result, the Pi concentration increased progressively (P<0·05) with BFR-H, while the Pi was relatively constant with BFR-M and CON during the exercise session. Our results suggest that intramuscular Pi accumulation during multiple sets of low-intensity exercise can be produced only by a high level of BFR, but not by moderate reduction. The Pi accumulation was associated both with exercise and with the rest period between sets.
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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 5·0 cm wide elastic cuff or a 13·5 cm 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 15 min 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 15 min 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.
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Recent studies have demonstrated that even a low-intensity resistance exercise can effectively induce muscle hypertrophy and strength increase when combined with moderate blood flow restriction (BFR) into the exercising muscle. Although serious side effects of low-intensity resistance exercise with BFR have not been reported, a concern of thrombosis has been suggested, because this type of exercise is performed with restricted venous blood flow and pooling of blood in extremities. Thus, the purpose of this study was to investigate the effects of low-intensity resistance exercise with BFR on coagulation system in healthy subjects. Ten healthy men (25.1 +/- 2.8 year) performed four sets of leg press exercises with and without BFR (150-160 mmHg) at an intensity of 30% of one-repetition maximum (1RM). In each exercise session, one set with 30 repetitions was followed by three sets with 15 repetitions. Blood samples were taken before, and 10 min, 1, 4 and 24 h after the exercise. Prothrombin fragment 1 + 2 (PTF) and thrombin-antithrombin III complex (TAT) were measured as markers of thrombin generation, whereas D-dimer and fibrin degradation product (FDP) were measured as markers of intravascular clot formation. Changes in plasma volume (PV) were calculated from haemoglobin and hematocrit values. PV reduction was significantly greater after the exercise with BFR than without (P<0.05). However, neither markers of thrombin generation nor intravascular clot formation increased after the exercises. These results suggest that low-intensity resistance exercise with BFR does not activate coagulation system in healthy subjects.