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Potential safety issues with blood flow restriction training

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The focal point of previous literature was establishing the efficacy of blood flow restriction training with respect to muscular strength, muscular hypertrophy, and muscular endurance. After mounting evidence supporting the efficacy of low-intensity blood flow restriction training, research has shifted to the overall safety of this training modality. The aim of this review was to summarize the research on the overall safety of blood flow restriction training, focusing on the cardiovascular system (central and peripheral), muscle damage, oxidative stress, and nerve conduction velocity responses compared with those observed with regular exercise. Although still sparse, the blood flow restriction training research thus far is promising with respect to safety outcomes. Individuals respond similarly to blood flow restriction training and to regular exercise; however, longer term studies are required to better understand the chronic effects of low-intensity blood flow restriction training and possible safety issues.
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Potential safety issues with blood flow restriction training
J. P. Loenneke
, J. M. Wilson
, G. J. Wilson
, T. J. Pujol
, M. G. Bemben
Department of Health and Exercise Science, The University of Oklahoma, Norman, Oklahoma, USA,
Department of Exercise
Science and Sport Studies, University of Tampa, Tampa, Florida, USA,
Department of Nutritional Sciences, University of Illinois,
Champaign-Urbana, Illinois, USA,
Department of Health, Human Performance, and Recreation, Southeast Missouri State
University, Cape Girardeau, Missouri, USA
Corresponding author: Jeremy Paul Loenneke, 1401 Asp Avenue, Room 104, Norman, Oklahoma 73019-0615, USA. Tel: 11
405 325-5211, Fax: 11 405 325-0594, E-mail:
Accepted for publication 13 December 2010
The focal point of previous literature was establishing the
efficacy of blood flow restriction training with respect to
muscular strength, muscular hypertrophy, and muscular
endurance. After mounting evidence supporting the efficacy
of low-intensity blood flow restriction training, research has
shifted to the overall safety of this training modality. The
aim of this review was to summarize the research on the
overall safety of blood flow restriction training, focusing on
the cardiovascular system (central and peripheral), muscle
damage, oxidative stress, and nerve conduction velocity
responses compared with those observed with regular ex-
ercise. Although still sparse, the blood flow restriction
training research thus far is promising with respect to safety
outcomes. Individuals respond similarly to blood flow re-
striction training and to regular exercise; however, longer
term studies are required to better understand the chronic
effects of low-intensity blood flow restriction training and
possible safety issues.
The American College of Sports Medicine (ACSM)
recommends weight training at 70% or greater of
one’s one repetition maximum (1RM) in order to
achieve muscular hypertrophy under normal condi-
tions. Exercise intensities below 70% 1RM rarely
produce substantial muscle hypertrophy or strength
gains (ACSM, 2009). However, many individuals
such as the elderly and rehabilitating athletes are
unable to withstand the high mechanical stresses
placed upon the joints during heavy resistance train-
ing; therefore, professionals have sought lower
intensity training alternatives.
One such alternative is training with low intensities
in combination with blood flow restriction, also
known as KAATSU training. Blood flow restriction
training, as the name implies, involves decreasing
blood flow to a muscle by application of a wrapping
device, such as a blood pressure cuff or specially
designed restrictive straps. Evidence indicates that
this style of training can provide a unique, beneficial
mode of exercise, even in clinical settings, because it
produces positive training adaptations equivalent to
the physical activity of daily life (10–30% of maximal
work capacity) (Abe et al., 2006). Muscle hypertro-
phy has recently been shown to occur even during
exercise with intensities as low as 20% 1RM
with moderate vascular restriction ( 100 mmHg)
(Yasuda et al., 2005), which could be quite beneficial
to athletes (Takarada et al., 2000a) and patients in
post-operation rehabilitation, particularly those with
ACL injuries (Takarada et al., 2000b; Ohta et al.,
2003), the elderly (Fry et al., 2010; Karabulut et al.,
2010), and even astronauts (Iida et al., 2007; Loen-
neke & Pujol, 2010). Published studies hypothe-
size that blood flow restriction training induces
skeletal muscle hypertrophy through a variety of
mechanisms (for a review, please see (Loenneke
et al., 2010); however, a definitive mechanism has
yet to be elucidated.
The focal point of previous literature was estab-
lishing the efficacy of blood flow restriction training
with respect to muscular strength, muscular hyper-
trophy, and muscular endurance (for reviews, please
see (Wernbom et al., 2008; Loenneke & Pujol, 2009,
2010; Manini & Clark, 2009; Loenneke et al., 2010).
After demonstrating the efficacy of blood flow
restriction training, the literature now has shifted
more toward the overall safety issues of training with
moderately restricted blood flow (Clark et al., 2010;
Madarame et al., 2010; Renzi et al., 2010). Therefore,
the purpose of this manuscript is to provide an
updated review on several measures of safety with
respect to blood flow restriction training, and
compare those responses to regular exercise.
Scand J Med Sci Sports 2011 &2011 John Wiley & Sons A/S
doi: 10.1111/j.1600-0838.2010.01290.x
Peripheral blood flow changes
Because blood flow dynamics are manipulated with
blood flow restriction training, there are obvious
potential safety concerns for practitioners with
respect to blood flow changes post-exercise (PO
The congestion and distension of veins that can
occur from the pooling of blood with blood flow
restriction could potentially result in valve damage
within the veins. The cardiovascular responses to
regular exercise are partially dependent upon the
type of muscle contraction, with differing intensities
and types of contraction (isometric, dynamic, ec-
centric, etc.) producing different patterns of blood
flow. Alomari and Welsch (2007) reported increased
peak PO
with dynamic handgrip exercise; how-
ever, others have reported decreased PO
isometric contractions (McGowan et al., 2006,
Studies investigating PO
following blood flow
restriction exercise are sparse. Renzi et al. (2010)
reported decreased flow-mediated vasodilation fol-
lowing 14 min of blood flow restriction walking. In
contrast to this acute study, Patterson and Ferguson
(2010) reported that chronic (4 weeks) plantar flexion
exercise with blood flow restriction resulted in an
enhanced PO
compared with resistance exercise
alone, suggesting that the blood flow with restrictive
exercise is acutely impaired post-exercise but en-
hanced over repeated bouts of exercise.
The exact mechanism for the increase in PO
chronic blood flow restriction exercise remains un-
known. Patterson and Ferguson (2010) postulated
that perhaps an increased venous compliance from
the pooling of blood associated with blood flow
restriction training could explain the increase in
(Convertino et al., 1988). Other potential ex-
planations include the restriction of oxygen and/or
accumulation of metabolites, specifically vasoactive
metabolites (e.g. adenosine) (Loenneke et al., 2010).
The accumulation of metabolites and the decreased
availability of oxygen results in the recruitment of
fast twitch (FT) fibers at lower than expected exercise
intensities (Loenneke et al., 2010). FT fibers have
demonstrated preferential capillarization compared
with slow twitch fibers in certain situations (Adair et
al., 1990). Local metabolic changes may also play an
important signaling role for vascular endothelial
growth factor (VEGF) upregulation (Roca et al.,
1998), possibly initiated through the VEGF/NO
cascade (Milkiewicz et al., 2005), because at least
one study reported VEGF increased in response to
resistance training with blood flow restriction (Ta-
kano et al., 2005). Additionally, capillary shear stress
facilitates angiogenesis, thus reperfusion of blood
flow post-exercise might also contribute to the en-
hancement of blood flow following blood flow re-
striction exercise (Suzuki et al., 2000; Hudlicka &
Brown, 2009). Further support comes from Evans et
al. (2010) who recently reported that 4 weeks of
blood flow restriction exercise (plantar flexion) en-
hanced microvascular filtration, an index of capillar-
ity, supporting the hypothesis that an increase in
capillarization can occur.
Like PO
, research is equivocal regarding the
changes in peripheral pulse wave velocity (PWV)
from regular exercise. PWV is an indirect measure
of peripheral arterial stiffness, determined by mea-
suring waveforms from the common femoral and
posterior tibial artery of the ankle (Clark et al.,
2010). PWV increases as arterial stiffness increases.
Collier et al. (2008) found that 4 weeks of resis-
tance training (65% 1RM) increased peripheral
PWV; however, several studies have shown no
deliterious effect of resistance training on arterial
stiffness (PWV) (Cortez-Cooper et al., 2005; Casey
et al., 2007; Yoshizawa et al., 2009). The Collier et
al. (2008) study investigated pre- and stage 1
hypertensive patients, which might explain the
disparity in findings (elevated sympathetic out-
flow). Clark et al. (2010) found no changes in
PWV following 4 weeks of bilateral knee extensor
training with either low-intensity blood flow re-
striction training (30% 1RM) or high-intensity
exercise (80% 1RM).
Other indices of peripheral resistance, total per-
ipheral resistance (TPR) and ankle brachial index
(ABI), have also been investigated with blood flow
restriction training. Takano et al. (2005) found peak
TPR to be similar between blood flow restricition
exercise and a work matched control group; how-
ever, more recently, Renzi et al. (2010) found TPR to
be significantly higher (BFR 512% vs
CON 540%) during walking with blood flow
restriction. These different intensities might be attri-
butable to the different exercise modes or the overall
volume of exercise. ABI appears to remain un-
changed following both acute (Renzi et al., 2010)
and chronic blood flow restriction exercise (Clark
et al., 2010).
In summation, the peripheral blood flow response
to blood flow restriction training appears to respond
in a similar fashion as regular exercise, and future
research efforts might be better served to focus on the
time course of the PO
impairment observed with
acute blood flow restriction exercise. In addition,
chronic blood flow restriction training studies should
be designed to measure both the chronic effects of
training, as well as the acute responses observed on
the last training day of a program, and the exercise
should include more than one muscle group being
trained in a session in order to better reflect a real-
world setting.
Loenneke et al.
Central responses of the cardiovascular system
In general, dynamic exercise results in a simultaneous
decrease in peripheral resistance with a concomitant
increase in heart rate and stroke volume (Mayo &
Kravitz, 1999). These responses result in only slight
increases in mean arterial pressure (MAP). During
high-intensity double leg resistance training, based on
ACSM guidelines (70–100% 1RM), there is complete
occlusion of the skeletal muscle vasculature from
mechanical compression and increases in intrathoracic
pressure. Extensive research from MacDougall’s lab
using a high-intensity (80–100% 1RM) double leg
press model demonstrated peak systolic and diastolic
pressures as high as 480/350mmHg and a doubling of
MAP (114–212 mmHg) (MacDougall et al., 1985,
1992; Haslam et al., 1988; Lentini et al., 1993).
Additionally, heart rates reached values of 170 beats
per minute or higher. End-diastolic and end-systolic
volumes declined by 30% and 50%, respectively, with
a concomitant 17–35 mL decline in stroke volume. In
comparison with low-intensity non-occlusion exercise
(20% 1RM), low-intensity blood flow restriction
training (20% 1RM) with the lower body (bilateral
leg extensions) has been found to result in slightly
greater values for heart rate (109 vs 96 bpm), and
systolic (182 vs 155 mmHg), diastolic (105 vs
99 mmHg), and mean arterial blood pressures (127
vs 113 mmHg) (Takano et al., 2005); however, these
values are all well below changes that occur during
high-intensity resistance training. While end-diastolic
and end-systolic volumes have yet to be measured
with blood flow restriction training, slight declines in
stroke volume (12%), but not cardiac output, have
been observed with blood flow restriction training
(Takano et al., 2005). Because these central cardio-
vascular responses are generally lower than traditional
resistance training, they suggest that low-intensity
blood flow restriction training is a safe alternative.
It should be noted that although Takano et al.
(2005) observed central cardiovascular values lower
than traditional resistance training studies, different
exercises were used. Central cardiovascular responses
to double leg press with blood flow restriction have
yet to be investigated. In addition, although tradi-
tional resistance training results in acute spikes in
blood pressure, research has observed a beneficial
post-exercise hypotensive response (MacDonald et
al., 1999; Fisher, 2001; Simao et al., 2005; de Salles et
al., 2010), even observed at intensities as low as 50%
1RM (Fisher, 2001). Furthermore, evidence exists to
indicate that chronic traditional resistance training
might also lower resting blood pressure (Cornelissen
& Fagard, 2005). Future blood flow restriction
research should investigate the post-exercise blood
pressure response into recovery as well as the effect of
chronic training on resting blood pressure.
Blood coagulation
Hemostasis is maintained through a balance between
coagulation and fibrinolytic activity and exercise has
been shown to affect activation of both processes
(Nakajima et al., 2007). Regular exercise preferen-
tially activates fibrinolysis, while strenuous exercise
may increase activity of the coagulation system,
resulting in venous thrombosis. Research demon-
strates that complete vascular occlusion can cause
the formation of a thrombus and can induce a
microvascular occlusion even after reperfusion.
This post-reperfusion occlusion can result in both
muscle damage and cell necrosis (Harman, 1948;
Strock & Majno, 1969). Furthermore, the literature
has suggested that metabolic and/or adrenergic fac-
tors may play some role in exercise-induced throm-
bin production. To illustrate, Herren et al. (1992)
reported a positive correlation between post-exercise
blood lactate and thrombin–antithrombin III com-
plex (TAT) concentrations and Wallen et al. (1999)
found that an adrenaline infusion, as well as fati-
guing exercise, also increased plasma TAT.
Nakajima et al. (2006) first investigated the ques-
tion of thrombosis in a survey of Asian facilities
implementing blood flow restriction training. Only
0.06% out of 300 000 training sessions resulted in an
incidence of venous thrombosis, which is lower rate
than that reported for the general Asian population
(0.2–0.26%) (Klatsky et al., 2000). Nakajima
confirmed their survey findings with a study measur-
ing various blood markers such as D-dimer and
fibrin degradation product (FDP), markers of intra-
vascular clot formation, which were not increased
following low-intensity blood flow restriction exer-
cise (30% 1RM). Prothrombin time (PT) and throm-
bin time, markers of coagulation activity, were also
unaffected with low-intensity blood flow restriction
exercise. However, blood flow restriction training did
result in increased tissue plasminogen activity (tPA),
a fibrinolytic protein that catalyzes the conversion of
plasminogen to plasmin, without affecting plasmino-
gen activator of inhibitor-1, the principle inhibitor of
tPA (Nakajima et al., 2007).
Clark et al. (2010) further investigated the coagu-
lation effects of blood flow restriction exercise and
found that neither PT nor D-dimer increased acutely
or chronically following 4 weeks of low-intensity
blood flow restriction training (30% 1RM) in 20–30
year olds. Fry et al. (2010) also found that D-dimer
was unaffected in elderly subjects (70 years of age)
performing an acute blood flow restriction exercise
bout (20% 1RM). However, one study (Zaar et al.,
2009) found that plasma TAT, a marker of thrombin
generation, increased after a 10 min bout of lower
body negative pressure at 30 mmHg, despite plasma
D-dimer not increasing (Zaar et al., 2009). To
Safety of blood flow-restricted exercise
address this concern, Madarame et al. (2010) inves-
tigated all previous blood markers of the coagulation
system as well as TAT, and reported that neither
markers of intravascular clot formation (D-dimer,
FDP) nor TAT were increased with low-intensity
blood flow restriction exercise (30% 1RM).
In summation, coagulation activity does not ap-
pear to increase following low-intensity blood flow
restriction exercise. In contrast, fibrinolytic potential
(tPA) appears to be enhanced with blood flow
restriction exercise as it is with traditional resistance
training. Protocols that have investigated coagula-
tion activity have implemented cuff sizes ranging
from 50 to 60 mm, restriction pressures of 150–
200 mmHg and exercise intensities ranging from
20% to 30% 1RM for up to four sets of lower
body exercise ( 10–15 min total time under restric-
tion) (Nakajima et al., 2007; Clark et al., 2010; Fry
et al., 2010; Madarame et al., 2010). Thus, these
findings are specific to studies using similar protocols
and are not necessarily applicable to all blood flow
restriction training models. Interestingly, vascular
compressions alone have long been associated with
an increase in fibrinolytic activity without elevation
of the coagulation cascade (Holemans, 1963; Robert-
son et al., 1972; Shaper et al., 1975; Stegnar &
Pentek, 1993). Thus, it is currently unknown if the
fibrinolytic response is from the exercise bout, the
moderate restriction stimulus, or the combination of
both. Future research should examine what effects
longer duration low-intensity blood flow restriction
exercise might have on the coagulation system.
Oxidative stress
Oxidative stress is a biological phenomenon marked
by an imbalance between reactive free radicals and
antioxidant defenses (Halliwell & Gutteridge, 1999).
The term oxidative stress indicates a combination of
increased free radical production and/or exhaustion
of antioxidant defenses (local water-soluble than fat-
soluble antioxidants). Severe acute or prolonged
chronic oxidative stress can lead to oxidatively mod-
ified lipids, proteins, and DNA (Hudson et al., 2008).
An acute exercise bout under normal conditions is
typically associated with a transient increase in
oxidative stress, with the response being proportional
to exercise intensity. The literature demonstrates that
high-intensity exercise ( 70% 1RM) involving a
large muscle mass consistently elicits a measurable
increase in blood oxidative stress markers (Lee et al.,
2002; Bloomer et al., 2005, 2006, 2007; Hudson et al.,
2008), but the responses to lower intensity resistance
exercise (o60% 1RM) have been mixed (McBride
et al., 1998; McAnulty et al., 2005). Not only is the
oxidative stress response affected by exercise intensity,
it has also been shown to increase with ischemic
reperfusion (IR) models (Tsutsumi et al., 2007). IR
in muscle results in an increased vascular permeability,
attributed to an increase of xanthine oxidase activity
during the hypoxic condition resulting in elevated
reactive oxygen species (ROS) (Korthuis et al., 1985).
Although IR models increase ROS levels, this has
not been observed with exercise in combination with
moderate vascular restriction. Takarada et al.
(2000a) provided the first study looking at oxidative
stress following low-intensity (20% 1RM) knee ex-
tensor exercise with moderate blood flow restriction
(214 mmHg). Using thiobarbituric acid reactive
substances (TBARS) as the measure, Takarada et al.
(2000a) found no increases in TBARS with either
low-intensity exercise or low-intensity exercise with
blood flow restriction (20% 1RM). One limitation of
this study was the measurement of TBARS, which is
a non-specific and insensitive measure of lipid per-
oxidation. To address this, Goldfarb et al. (2008)
followed up with a study measuring protein carbo-
nyls and blood glutathione status, both of which are
sensitive indicators of oxidative stress. They found
that neither was increased with low-intensity blood
flow restriction exercise (30% 1RM); however, eleva-
tions were seen with the moderate resistance exercise
(70% 1RM) and during blood flow restriction
without exercise.
Goldfarb et al. (2008) cited two possible explana-
tions for why oxidative stress remained unchanged
with respect to blood flow restriction and exercise.
The first possibility is that the muscle contractions
during the partial occlusion were able to overcome
the resistance to venous outflow and thus helped
remove the oxidative stress markers from the circula-
tion. The second possibility is that the pressures
during the contractions were sufficient to enhance
blood flow during the muscle contractions, which
enabled adequate blood flow delivery to overcome
the partial vascular restriction.
Other explanations could be that the partial occlu-
sion with exercise causes oxidative stress markers to
peak much later than the 15 min post-exercise time
point measured in the Goldfarb study (Goldfarb et
al., 2008). The protein carbonyl levels, while not
statistically significant, did increase from post-exer-
cise to 15 min post-exercise. Previous investigations
have found that protein carbonyls do not always
peak immediately following exercise, but instead
continued to increase for over an hour post-exercise
(Bloomer et al., 2005). One other possibility may be a
protective effect from heat shock proteins (HSP) as
they are known inhibitors of oxidative stress (Polla
et al., 1996) and researchers using a rat model have
shown that vascular blood flow restriction increases
HSPs (Kawada & Ishii, 2005). This HSP response
has been investigated only once with respect to blood
Loenneke et al.
flow restriction exercise in humans, and that study
found no increase in HSPs (Fry et al., 2010); how-
ever, this study involved an elderly population in
which the HSP response is known to be blunted
(Hamada et al., 2005; Vasilaki et al., 2006).
In summation, oxidative stress has not been shown
to increase in response to low-intensity blood flow
restriction training ( 30% 1RM). Despite this,
research on this topic is sparse, and much more
research is warranted before a definitive opinion
can be made on the effects of low-intensity blood
flow restriction training on damage from oxidative
stress. Research should focus on measuring blood
markers of oxidative stress out to at least 24 h post-
exercise and ideally up to 48 h. HSPs, known inhibi-
tors of free radicals, should also be measured in
younger populations to see what role, if any, they
play in the antioxidant defense system.
Muscle damage
Muscle damage occurs during and after unaccus-
tomed exercise, particularly if the exercise involves a
large amount of eccentric contractions (Wilson et al.,
2009). It is currently thought that the initial muscle
damage is proportional to the relative load and thus
mechanical perturbations in skeletal muscle, while
the inflammatory response that occurs later may
explain additional damage following exercise (Clark-
son & Hubal, 2002). Because of the inherent errors in
assessing whole muscle damage from small biopsy
samples, as well as the invasive nature of these
techniques, investigators have sought more indirect
indices. According to Warren et al. (1999), the three
most frequently utilized measures include subjec-
tively estimated soreness from a pain rating scale,
strength decrements, and changes in blood protein
levels (e.g. creatine kinase and lactate dehydrogen-
ase) (Warren et al., 1999). Our data and others have
found that muscle soreness peaks at approximately
24–72 h following exercise (White et al., 2008; Wilson
et al., 2009). In general, isokinetic knee extensions
result in approximately a marking of 4–5 on a scale
of 10 with soreness, while maximal eccentric contrac-
tions result in scores as high as 7–8 (Clarkson &
Hubal, 2002). However, low-intensity blood flow
restriction knee extensor exercise (35% MVC) only
resulted in peak soreness scores of 2.8 at 24 h, with no
increases in perceived soreness at any other time
points (Umbel et al., 2009). In two independent
studies, we reported increases in creatine kinase
from 140 U/L at rest to values as high as 1100 U/L
following leg extension exercise (White et al., 2008;
Wilson et al., 2009); however, others have found
post-exercise values 45000 U/L using primarily
eccentric downhill exercise (Clarkson & Hubal,
2002). In contrast, low-intensity blood flow restric-
tion training has not been shown to result in changes
in either creatine kinase or myoglobin content fol-
lowing acute bouts of resistance exercise at 20%
1RM (Takarada et al., 2000a) or walk training at
50 m/min (Abe et al., 2006). While more extensive
research needs to be conducted, to this point it
appears that low-intensity blood flow restriction
training causes only minimal muscle damage.
Nerve conduction velocity
Nakajima et al. (2006) found from their survey of 105
facilities that used blood flow restriction as a training
technique that numbness was sometimes reported in
response to a blood flow restrictive exercise bout.
Although only 1.6% out of 30 000 sessions reported
the transient side effect, it raised an important safety
question, with respect to the numbness and possible
nerve conduction blockage which is often seen fol-
lowing surgery (Lundborg, 1988) or when external
compressions are applied to a limb causing both
ischemia and a slowing of nerve conduction velocity
(NCV) (Denny-Brown & Brenner, 1944; Pedowitz
et al., 1991; Mittal et al., 2008).
Clark et al. (2010) investigated the overall integrity
of sensory motor nerve conduction by estimating
NCV from the latency responses in H-reflex record-
ings. NCV was unchanged after 4 weeks of low-
intensity blood flow restriction training (30% 1RM).
This was an expected outcome because the overall
length of the restrictive exercise bout only lasted
approximately 10–15 min. Surgery, which requires
much longer durations of occlusion, is associated
with a transient slowing in NCV, which is rapidly
reversed and rarely results in permanent nerve
damage (Lundborg, 1988).
In summation, low-intensity blood flow restriction
training (30% 1RM) does not seem to have a chronic
negative effect on NCV in healthy human subjects.
Future research should investigate the NCV effects of
an acute blood flow restriction training bout to see if
any short-term impairment occurs, and if so, the time
course of that impairment. In addition, focus should
be placed on long-term studies greater than 4 weeks,
to determine what effect longer term training has on
H-reflex amplitudes during blood flow restriction
exercise because increases have been noted following
chronic resistance training (Aagaard et al., 2002;
Lagerquist et al., 2006; Holtermann et al., 2007).
Pressure recommendations for future research
Following a careful review of the literature, numer-
ous pressures have been used for restricting blood
flow. These restrictive pressures generally range from
Safety of blood flow-restricted exercise
approximately 1.3 times greater than systolic blood
pressure ( 160 mmHg) to upwards of 200 mmHg.
In most published reports, the width of the belt used
to restrict blood flow is often times ignored. How-
ever, the width of the restrictive device is of impor-
tance because wider cuffs transmit pressure
differently than narrow cuffs (Crenshaw et al.,
1988), thus applying 200 mmHg across 50 mm with
a KAATSU Master cuff which will likely produce a
different stimulus than 200 mmHg applied over
135 mm with a different cuff. Crenshaw et al. (1988)
demonstrated that wider cuffs restrict blood flow at a
lower overall pressure than a narrow belt. Addition-
ally, Shaw and Murray (1982) observed that limb
circumference is also a determining factor in the level
of blood flow restriction from a given pressure,
especially with a narrow cuff. They demonstrated
using an 80 mm wide cuff, a consistent decrease in the
mean maximal tissue-fluid pressure as the circumfer-
ence of the limb increased. However, although a
wider cuff may produce a greater level of restriction
with lower pressures, Mittal et al. (2008) has shown
that a wider cuff also produces a greater reduction in
NCV when compared with a narrow cuff (140 vs
70 mm).
In summary, perhaps the pressures used to restrict
blood flow should to some degree be determined by
the width of the cuffs and limb circumference, and
not necessarily by pressures previously used in the
literature. Investigators should also consider the
possible NCV impairments that may occur from
using a wider cuff (Mittal et al., 2008).
This review focused on what is currently known
about the safety of blood flow restriction training
and how this compares to exercise under normal
blood flow conditions (Fig. 1). The research, while
positive, is limited and more research should be
completed to better determine under what conditions
this type of training can be safely used. In addition,
the width of the belt and limb circumference should
be accounted for when applying the restrictive sti-
mulus to each subject. In conclusion, the current
research on blood flow restriction training with
respect to safety outcomes confirms earlier reports
that blood flow restriction exercise, when used in a
controlled environment by trained and experienced
personnel, provides a safe training alternative for
most individuals regardless of age and training
Key words: KAATSU, cardiovascular, muscle
damage, hypertrophy.
Fig. 1. Summary of the potential safety issues with blood flow restriction (BFR) compared with high-intensity resistance
training (HIT-RT). Responses for each were as follows: ", increases; #, decreases; $, no change.
Loenneke et al.
This review was not supported by funding from an outside
source. The only affiliation that one of the co-authors, M. G.
Bemben, has with Sato Sports Plaza is that he is the current
Chair for the Kaatsu Training Interest Group within the
American College of Sports Medicine.
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Safety of blood flow-restricted exercise
... Thus, the determination of the cuff's applied pressure to the limb during exercise likely becomes a key element for the correct, safe, and effective use of this technique, particularly in clinical populations. 1,15 Nevertheless, although BFRT has been shown to be a safe type of training, 1,4,16,17 risk may be heightened if complete occlusion is reached through inappropriately applied pressures. 15 Recently, recommendations were given suggesting that clinical application of BFRT pressures be administered with a percentage of limb occlusion pressure (LOP). 1 LOP is the minimum pressure required to stop arterial blood flow into the limb distal to the cuff at a specific time, with a specific tourniquet, applied to a specific patient, in a specific location. ...
... There are studies that have applied methodological procedures of occlusion based on 1/3 of the diastolic blood pressure 55 or based on resting brachial systolic blood pressure (rbSBP) that usually apply about 130% of the rbSBP (rbSBP 1.3 ). 25,38,52,[55][56][57][58][59] However, findings by Loenneke et al 16 suggest that wider cuffs (eg, greater than a normal blood pressure cuff) inflated at rbSBP 1.3 would exceed the necessary pressure for complete arterial restriction. Even so there is debate whether rbSBP should even be considered a viable approach to personalizing pressures since studies report a moderate, if not absent, relationship between rbSBP and limb BFR. ...
... According to Loenneke et al, 16 our results show that when using the value of rbSBP 1.3 the cuff pressure applied reaches the LOP (100% and 113%, depending on the body area). Thus, futures studies could investigate the possibility of using the rbSBP 1.3 to indirectly estimate the LOP when Doppler ultrasound is not available, as the values seem to be very close in our study. ...
Context: Resistance training with blood flow restriction (BFR) has increased in clinical rehabilitation due to the substantial benefits observed in augmenting muscle mass and strength using low loads. However, there is a great variability of training pressures for clinical populations as well as methods to estimate it. The aim of this study was to estimate the percentage of maximal BFR that could result by applying different methodologies based on arbitrary or individual occlusion levels using a cuff width between 9 and 13 cm. Design: A secondary analysis was performed on the combined databases of 2 previous larger studies using BFR training. Methods: To estimate these percentages, the occlusion values needed to reach complete BFR (100% limb occlusion pressure [LOP]) were estimated by Doppler ultrasound. Seventy-five participants (age 24.32 [4.86] y; weight: 78.51 [14.74] kg; height: 1.77 [0.09] m) were enrolled in the laboratory study for measuring LOP in the thigh, arm, or calf. Results: When arbitrary values of restriction are applied, a supra-occlusive LOP between 120% and 190% LOP may result. Furthermore, the application of 130% resting brachial systolic blood pressure creates a similar occlusive stimulus as 100% LOP. Conclusions: Methods using 100 mm Hg and the resting brachial systolic blood pressure could represent the safest application prescriptions as they resulted in applied pressures between 60% and 80% LOP. One hundred thirty percent of the resting brachial systolic blood pressure could be used to indirectly estimate 100% LOP at cuff widths between 9 and 13 cm. Finally, methodologies that use standard values of 200 and, 300 mm Hg far exceed LOP and may carry additional risk during BFR exercise.
... The current literature lacks studies on joint proprioception during BFR training, even though it is essential to consider the safety issues of using BFR. So far, it has been assumed that the risks of performing BFR training are comparable to those of traditional training and include, for example, blood clotting and muscle damage [4,24]. Regarding proprioception, in the literature, we can find one study conducted by Yamada et al. on the effect of low-intensity aerobic exercise-more precisely, walking with a BFR applicated using an elastic band-on knee proprioception [12]. ...
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The number of blood flow restriction (BFR) training practitioners is rapidly increasing, so understanding the safety issues associated with limb occlusion is strongly needed. The present study determined the effect of BFR by an inflatable cuff worn around the arm on the wrist joint position sense (JPS) in healthy recreational athletes. In the prospective randomized, double-blind placebo control study, sixty healthy right-handed recreational athletes aged x = 22.93 ± 1.26 years were assigned to groups of equal size and gender rates: BFR, placebo, and control. The active wrist JPS was assessed in two separate sessions using an isokinetic dynamometer. The first assessment was performed with no cuffs. In the second session, a cuff with a standardized pressure was worn on the examined limb in the BFR group. In the placebo group, the cuff was uninflated. A between-session comparison in each group of collected angular errors expressed in degrees was carried out. The angular error in the BFR group was larger during the second measurement than the first one (p = 0.011-0.336). On the contrary, in the placebo (p = 0.241-0.948) and control (p = 0.093-0.904) groups, the error value in the second session was comparable or smaller. It was determined that BFR by an inflatable cuff around the arm impairs the wrist position sense. Hence, BFR training should be performed with caution.
... The single event of persistent paraesthesia post-exercise lasted for 25 minutes only and did not reoccur but could be explained by narrower cuff widths leading J o u r n a l P r e -p r o o f to greater discomfort in some users (Estebe et al., 2000). Nerve conduction velocity has previously been reported to be unaffected by four weeks of low intensity resistance exercise combined with BFR-training (Loenneke et al., 2011). Bruising was reported as a side effect by 13% of BFR practitioners in a recent worldwide survey (Patterson & Brandner, 2018). ...
Full-text available
Objectives Explore the feasibility of lower-limb garment-integrated BFR-training. Design Observational study. Setting Human performance laboratory. Participants Healthy males with no experience of BFR-training. Main outcome measures Feasibility was determined by a priori thresholds for recruitment, adherence, and data collection. Safety was determined by measuring BFR torniquet pressure and the incidence of side effects. Efficacy was determined by measuring body anthropometry and knee isokinetic dynamometry. Feasibility and safety outcomes were reported descriptively or as a proportion with 95% confidence intervals (95% CI), with mean change, 95% CIs, and effect sizes for efficacy outcomes. Results Twelve participants (mean age 24.8 years [6.5]) were successfully recruited; 11 completed the study. 134/136 sessions were completed (adherence = 98.5%) and 100% of data were collected. There was one event of excessive pain during exercise (0.7%, 95% CI 0.0%, 4.0%), two events of excessive pain post-exercise (1.5%, 95% CI 0.4%, 5.5%), and one event of persistent paraesthesia post-exercise (0.7%, 95% CI 0.0%, 4.0%). Mean maximal BFR torniquet pressure was <200 mmHg. We observed an increase in knee extension peak torque (mean change 12.4 Nm), but no notable changes in body anthropometry. Conclusions Lower-limb garment-integrated BFR-training is feasible, has no signal of important harm, and could be used independently.
... The exercise of blood flow restriction with low loads (20 to 40% 1RM) may be a safe tool 6 and effective to improve morphology and strength response in human muscle tissue 7 . This restriction generates a local tissue hypoxemia that accelerates glycogen expenditure, making the medium acidic, activating the hypothalamus and increasing GH production, the growth hormone. ...
Full-text available
This is a cross-sectional, comparative, and randomized study aimed to evaluate the effects of the partial vascular occlusion technique (Kaatsu Training) associated with low load exercises in the muscle strengthening of quadriceps in women with patellofemoral pain. We evaluated 18 women with patellofemoral pain, aged from 18 to 35 years, allocated into two groups. The experimental group performed the strengthening with blood flow reduction with the aid of a sphygmomanometer, associated with low load (≅20% RM). Whereas the control group performed exercises with the same load, but without blood flow reduction. The treatment was performed three times a week for six weeks, totaling 18 sessions. We used the numerical pain rating scale (NPRS) and the anterior knee pain scale (AKPS) questionnaire for evaluation; we evaluated the muscle strength of knee extensors by the digital dynamometer. The results showed that the partial vascular occlusion technique significantly improved the values of quadriceps strength gain in the right, 6.22kg (p=0.03) and left limb, 6.98kg (p=0.04), in women with patellofemoral pain. Therefore, training with partial vascular occlusion can be useful for strengthening of the knee extensor musculature in women with patellofemoral pain who, because of the pain, have low tolerance to high load exercises for muscle strengthening. An effective, safe and cost-effective technique, which does not require an investment in a leg extension machine, since, with a cuff, low load exercises can offer significant results. Keywords: Knee; Pain; Physical Endurance; Rehabilitation
... Detailed discussions of these aspects have been published in several review studies and are beyond the scope of the current study. 14,[25][26][27] However, considering the fact the present study proposes a home-based BFR protocol, some safety aspects will now be presented. The effect of BFR on the central cardiovascular response depends on the level of BFR and mode of application (i.e., continuous vs. intermittent). ...
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ntroduction: Physical inactivity is a major unintended consequence of the social distancing imposed by the Covid-19 pandemic. Increased physical inactivity and sedentary behaviors have profound physiological impacts on muscular health,leading to muscle and strength losses that are associated with lowerperformance and higher mortality rates. In the so-called “new normal”, exercise routines must find alternative ways to replace high-intensity resistance exercises,since resources are limited in home environments. Blood flow restriction (BFR) is a low-intensity training method involving compressive pressure of the vasculature by use of a tourniquet cuff in the proximal portion of the upper and lower limbs. BFR has been demonstrated to be a safe and efficient training modality to promote muscle and strength gains in different groups, including those under musculoskeletal rehabilitation, young and older adults, and athletes. Objective: This review aims to show that BFR training is an effective intervention for counteracting losses of muscle mass and function caused by Covid-19. Methods: A review of the scientific literature was conducted on electronic databases, such as PubMed, Scielo and Web of Science, covering the period 2000–2020. Results: We advocate the use of BFR training as an urgent counteracting intervention to prevent muscle and strength losses during social distancing and propose a progressive home-based protocol based on wide array of literature. Conclusion: This evidence can help practitioners, personal trainers, physical therapists, and physician assistants to implement an alternative exercise routine that may prevent the deleterious physiological effects of physical inactivity on muscle function during intermittent social distancing.
The aim of the study was to systematically review the effect of resistance training with blood flow restriction on muscle strength and functional capacity of clinical populations. This research used SCOPUS, WEB OF SCIENCE and MEDLINE/PubMed databases from the first records until November 2021 and in English. The terms (“blood flow restriction” or “vascular occlusion” or “kaatsu training” and “low intensity”) and (“strength training” or “resistance training” or “strength”) and (“clinical populations” or “elderly” or “old” or “hypertension” or “diabetes” or “myositis” or “obesity” and “chronic diseases”) and (“functional capacity” or “functionality” or “muscle function”) were used. Clinical trials (randomised and non-randomised) were included when compared to high-intensity resistance training, low-intensity resistance training, low-intensity resistance training with blood flow restriction and a control group without physical exercise. The quality of the evidence was assessed using the Testex scale. During the research, 122 articles were pre-selected and analysed, and at the end of the selection, nine articles met all the inclusion criteria and established specifications. We conclude that resistance training associated with blood flow restriction has been an effective and tolerable alternative in improving muscle strength and functional capacity and, therefore, a potential tool for the clinical population.
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A consensus on the acute cardiovascular responses to low intensity (LI) resistance exercise (RE) combined with blood flow restriction (BFR) has not yet been reached. This study was designed to compare acute cardiovascular responses to a single bout of LIRE, high intensity (HI) RE, and LIRE with BFR in physically active young males. Participants completed 3 RE sessions in random order, where each session consists of 4 sets of unilateral dumbbell bicep curls. Cardiovascular hemodynamics were measured at baseline and right after each set of RE. Aortic augmentation index (AIx) was significantly higher after set 2,3,4 of RE in LI + BFR session compared to LI session (P < 0.05). Brachial systolic blood pressure (SBP), heart rate (HR), brachial rate pressure product (RPP), and central RPP responses did not differ between LI and LI + BFR sessions (P > 0.05). HI session had a higher central SBP, brachial RPP, central RPP, and aortic AIx compared to LI session after each set of RE (P < 0.05), but not brachial SBP (P > 0.05). Taken together, this study showed that LIRE combined with BFR acutely augmented aortic stiffness, as also observed in HI session, but myocardial oxygen consumption was only higher in HI session when compared to LI session. Thus, although BFR did not exaggerate cardiovascular responses nor cause extra myocardial oxygen consumption, it should be prescribed with caution when control of acute aortic stiffening is necessary during RE.
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Aim: The aim of the current study was to investigate the effect of resistance training with blood flow restriction and creatine consumption on the serum levels of myostatin and growth hormone in male bodybuilders. Methods: 36 male bodybuilders with an average age of 22.63 years were divided into three equal groups of 12 people, which included the resistance training group with blood flow restriction and creatine supplementation, the resistance training group with blood flow restriction and placebo, and the creatine consumption group. The exercise program was performed for 8 weeks and 3 sessions of 80 minutes each week, in a stationary and circular manner. The training intensity was 30-40% of a maximum repetition in each training session. Creatine supplement was also taken for eight weeks, every five days and daily in the amount of 20 grams. Growth hormone, muscle strength and volume were evaluated before and after training. Results: The results showed that the serum concentration of growth hormone, muscle strength and volume increased significantly after eight weeks of blood flow restriction training and creatine consumption (P=0.003). while the serum concentration of myostatin had a significant decrease (P=0.002). Conclusion: It seems that low-intensity training under conditions of blood flow restriction and creatine consumption can lead to increase of strength and muscle hypertrophy, and in addition, increase the serum concentration of growth hormone and decrease myostatin. Therefore, it is recommended that athletes use the same protocol in their training to improve strength and increase muscle hypertrophy.
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This is a cross-sectional, comparative, and randomized study aimed to evaluate the effects of the partial vascular occlusion technique (Kaatsu Training) associated with low load exercises in the muscle strengthening of quadriceps in women with patellofemoral pain. We evaluated 18 women with patellofemoral pain, aged from 18 to 35 years, allocated into two groups. The experimental group performed the strengthening with blood flow reduction with the aid of a sphygmomanometer, associated with low load (≅20% RM). Whereas the control group performed exercises with the same load, but without blood flow reduction. The treatment was performed three times a week for six weeks, totaling 18 sessions. We used the numerical pain rating scale (NPRS) and the anterior knee pain scale (AKPS) questionnaire for evaluation; we evaluated the muscle strength of knee extensors by the digital dynamometer. The results showed that the partial vascular occlusion technique significantly improved the values of quadriceps strength gain in the right, 6.22kg (p=0.03) and left limb, 6.98kg (p=0.04), in women with patellofemoral pain. Therefore, training with partial vascular occlusion can be useful for strengthening of the knee extensor musculature in women with patellofemoral pain who, because of the pain, have low tolerance to high load exercises for muscle strengthening. An effective, safe and cost-effective technique, which does not require an investment in a leg extension machine, since, with a cuff, low load exercises can offer significant results. Keywords: Knee; Pain; Physical Endurance; Rehabilitation
Background: Blood flow restriction (BFR) has become a key rehabilitative tool for human orthopaedic conditions. With modernised technology and evolution of clinical application, patient-specific delivery of occlusion percentages is now considered the standard of care in human patients due to improved therapeutic outcomes and minimised safety risks. Safety validation and limb occlusion pressure (LOP) data for horses, however, are lacking. Objective: (1) To determine if BFR exposure resulted in forelimb biomechanical gait dysfunction as safety validation and (2) to investigate inter-horse and inter-limb LOP differences. Study design: Controlled in vivo experiment. Methods: Daily unilateral forelimb BFR was performed in four horses over 56 days. Clinical examinations and objective gait analyses were performed on Days 0, 28 and 56. Daily LOP values were determined by Doppler evaluation to deliver 80% vascular occlusion at a walk. A linear mixed model evaluated for differences in lameness, kinetic and kinematic gait parameters. Results: There were no significant differences in forelimb lameness (range of Grades 0-2 across all forelimbs), kinematic or kinetic gait parameters over time or between BFR-exposed and control (contralateral) limbs (p > 0.05). Clinically apparent complications related to BFR such as thrombosis or dermatitis were not appreciated. Significant differences in mean LOP values between various horses (p < 0.001) and measured left (204.48 mmHg) and right (173.78 mmHg) forelimbs (p < 0.001) were observed. Mean LOP and standard deviation across all readings was 189.1 ± 22.2 mmHg. Main limitations: Optimal BFR occlusion percentages and protocols with documented clinical efficacy are unknown. Small study population. Conclusions: Exposure to BFR did not result in forelimb biomechanical dysfunction in four horses. Applied pressures of 75-151 mmHg would likely simulate a range of 50%-80% vascular occlusion in horses, but inherent physiological variation between horses and forelimbs warrants incorporation of individual pressures.
1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?
KAATSU training is a novel training, which is performed under conditions of restricted blood flow. It can induce a variety of beneficial effects such as increased muscle strength, and it has been adopted by a number of facilities in recent times. The purpose of the present study is to know the present state of KAATSU training in Japan and examine the incidence of adverse events in the field. The data were obtained from KAATSU leaders or instructors in a total of 105 out of 195 facilities where KAATSU training has been adopted. Based on survey results, 12,642 persons have received KAATSU training (male 45.4%, female 54.6%). KAATSU training has been applied to all generations of people including the young ( 80 years old). The most popular purpose of KAATSU training is to strengthen muscle in athletes and to promote the health of subjects, including the elderly. It has been also applied to various kinds of physical conditions, cerebrovascular diseases, orthopedic diseases, obesity, cardiac diseases, neuromuscular diseases, diabetes, hypertension and respiratory diseases. In KAATSU training, various types of exercise modalities (physical exercise, walking, cycling, and weight training) are used. Most facilities have used 5-30 min KAATSU training each time, and performed it 1-3 times a week. Approximately 80% of the facilities are satisfied with the results of KAATSU training with only small numbers of complications reported. The incidence of side effects was as follows; venous thrombus (0.055%), pulmonary embolism (0.008%) and rhabdomyolysis (0.008%). These results indicate that the KAATSU training is a safe and promising method for training athletes and healthy persons, and can also be applied to persons with various physical conditions.
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training