Keywords
blood flow restriction - occlusion training - upper extremity - blood flow restriction training
Schlüsselwörter
Training zur Einschränkung des Blutflusses - Einschränkung des Blutflusses - Okklusionstraining - obere Extremität
Introduction
In recent years, blood flow restriction training (BFRT) has gained popularity among
scientific research. BFRT is the partial restriction of arterial flow by applying
pneumatic cuffs to the proximal portion of the extremity and complete restriction of
venous outflow [1]
[2]. According to the original perspective,
exercise training with a load exceeding 70% of 1RM (repetition-maximum) can induce
muscle hypertrophy [3]. Previous studies
have demonstrated significant gains in muscle strength and hypertrophy even with
resistance training at 30% of 1RM when combined with blood flow restriction (BFR)
[4]
[5]. An advantage of BFR is its ability to yield gains comparable to or
greater than using a load of 80% of 1RM when only 30% of 1RM load is employed [6]. The use of lower loads reduces stress on
the joints and preserves structure. It is a method that can be preferred in
individuals experiencing difficulty in performing high-load training due to
musculoskeletal disorders [7].
It has been demonstrated that the hypertrophic response is similar to that attained
with high-load resistance exercise [8].
Furthermore, BFRT has been proven to be a reliable and effective technique for
increasing muscle mass and strength. Various systematic reviews have indicated that
BFR can be used for the rehabilitation of individuals in pathological conditions
[9]
[10]. While studies have predominantly focused on the use of BFR in lower
extremity training [8], the effectiveness
of its application in upper extremity exercises remains unknown. For all these
reasons, the purpose of this review is to analyze how BFRT can be most effectively
utilized to enhance upper extremity muscle strength.
Methods
The protocol for this systematic review, is registered in PROSPERO which is an
international database of prospective registered systematic reviews (Registration
Number: CRD42022328559). This systematic review was developed by using PRISMA
(Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines
[11].
PubMed, Web of Science, MEDLINE, Scopus, and Cochrane Library databases were searched
from January 2000 to May 2022. Only articles published in English were considered
for evaluation. The keywords used in the research are ‘Blood flow restriction,’
‘blood flow restriction training,’ ‘blood flow restriction therapy,’ ‘occlusion
training,’ and ‘KAATSU training.’ The search steps for the databases are explained
in the flowchart. Articles that were not randomized studies or could not be accessed
in full text (despite attempts to contact the authors via email) were excluded.
Additionally, articles with a PEDro score of 4 or below were not included. Inclusion
criteria comprised a clinical population with either healthy individuals or those
with musculoskeletal pathology of the upper extremity, participants aged 18 years or
older, a study design with a randomized controlled trial, the application of BFR to
the arm, and a study assessing upper extremity muscle strength before and after
intervention. Evaluated outcomes include isokinetic and/or isometric force data for
upper extremity muscle strength. Data search, collection, and analysis of the
studies were independently conducted by two reviewers (EA and EAY). Discrepancies
were discussed with a third reviewer (ARO). Reviewers initially read titles and
abstracts of the studies without knowledge of each other's assessments based on
eligibility criteria. Full texts of the selected studies were accessed and
thoroughly analyzed. To evaluate the methodological quality of the studies, The
Physiotherapy Evidence Database scale (PEDro scale) was used [12], which includes of 11 items, with the
first question not contributing to the total score, resulting in a maximum score of
10 points [13]
[14]. All selected articles were reviewed by
two reviewers (EA and EAY), and any disagreements were resolved by consulting a
third reviewer (ARO).
Results
Twenty-four randomized controlled studies which are suitable for qualitative results
were shown in the flowchart ([Fig. 1]).
Twenty-four studies were included in the quantitative synthesis and 19 studies were
excluded as their PEDro scores were below 5. The PEDro scores of the included
studies ranged from 5 to 8 (out of a maximum of 10), with an average score of 6.4
([Table 1]). The characteristics of
the studies are presented in [Table 2].
The studies include 219 participants. One of the studies focused on patients with
hand osteoarthritis [15], while four
studies were conducted on healthy participants [16]
[17]
[18]
[19]. Hand grip strength was evaluated in two studies, one using the Jamar
hydraulic dynamometer [16] and the other
using a digital dynamometer [15]. Shoulder
muscle strength was evaluated in three studies: one utilized isokinetic testing and
a dynamometer for shoulder internal and external rotators [17], second one using manual muscle testing
for the supraspinatus and external rotators [18], and the third using a hand-held dynamometer for shoulder abductors,
internal and external rotators [19].
Fig. 1 Preferred Reporting Items for Systematic Reviews and
Meta-Analyses (PRISMA) flowchart diagram of the search process.
Table 1 PEDro score for included studies.
|
Q-1
|
Q-2
|
Q-3
|
Q-4
|
Q-5
|
Q-6
|
Q-7
|
Q-8
|
Q-9
|
Q-10
|
Q-11
|
Score
|
|
Florianovicz et al., 2019
|
(+)
|
(+)
|
(+)
|
(+)
|
(–)
|
(–)
|
(–)
|
(+)
|
(+)
|
(+)
|
(+)
|
7
|
|
Bowman et al., 2020
|
(+)
|
(+)
|
(+)
|
(+)
|
(–)
|
(–)
|
(+)
|
(+)
|
(–)
|
(+)
|
(+)
|
7
|
|
Brumitt et al., 2020
|
(+)
|
(+)
|
(–)
|
(–)
|
(–)
|
(–)
|
(+)
|
(+)
|
(–)
|
(+)
|
(+)
|
5
|
|
Magni et al., 2021
|
(+)
|
(+)
|
(+)
|
(+)
|
(–)
|
(–)
|
(+)
|
(+)
|
(+)
|
(+)
|
(+)
|
8
|
|
Lambert et al.,2021
|
(+)
|
(+)
|
(–)
|
(–)
|
(–)
|
(–)
|
(+)
|
(+)
|
(–)
|
(+)
|
(+)
|
5
|
Q: Question; (+): Yes; (–): No
Table 2 Characteristics of included studies.
|
Studies
|
Population Characteristics
|
Strength Measurement (method/muscle)
|
Exercise
|
Protocol
|
Duration/Frequency
|
Exercise Load
|
Conclusion
|
|
Florianovicz et al.
PEDro score: 7
|
-
Healthy women
-
n=58
-
EG-1: (n=15), 22± (1.19) years
-
EG-2: (n=15), 21±(1.24) years
-
EG-3: (n=14), 21±(2.2) years
-
CG: (n=14), 21±(2.1) years
|
-
Jamar dynamometer/ Handgrip strength
-
MM-50 load cell/ wrist extensor muscle
-
EMG (radial carpal extensor muscle)
|
Wrist extensor muscle strengthening
|
10 set x6
|
8 intervention 2 days/wk
|
BFR 1 RM %40
|
Significant increase in wrist extensor strength in the BFR group
compared to the control group (p=0.004)
|
|
Bowman et al.
PEDro score: 7
|
-
Healthy subjects
-
n=24
-
EG: (n=14), 26.2±3.4 years
-
CG: (n=10), no difference in age
|
|
-
Shoulder external rotation – internal rotation
-
Biceps curl -Triceps extension
-
prone horizontal shoulder abduction
|
BFR 1-RM %30
|
6 wk 2 days/wk
|
BFR pressure %60
|
Proximal and distal muscle strength and hypertrophy increased
more in BFR group than in control group
|
|
BFR: 30–15– 15–15
|
|
Brumit et al.
PEDro score: 5
|
-
Healthy subjects
-
n=46
-
25.0±2.2 years
|
Manuel muscle test/ Supraspinatus and Shoulder external
rotators
|
|
-
BFR+ exercise:1RM %30
-
Only exercise: :1RM %30
-
BFR pressure %50
|
8 wk 2 days/wk
|
BFR: 30–15– 15–15
|
No difference in strength in supraspinatus and external rotator
muscles between the groups
|
|
Magni et al.
PEDro score: 8
|
-
Hand osteoarthritis
-
n=59
-
EG-1: (n=19), 67.9(8.6) years
-
EG-2: (n=20), 72.7(9) years
-
CG: (n=20), 75.6(12) years
|
Digital Dynamometer/ Handgrip strength
|
Grip, pinch, and thumb extension and abduction strengthening
exercises.
|
-
BFR+advice 1-RM %30-40
-
HIT+advice
|
6 wk 3 days/wk
|
BFR: 30–15– 15–15
|
No improvement in grip strength and function
|
|
1-RM %60-70
|
HIT: 4X10
|
|
Just Advice (control)
|
|
Lambert et al.
PEDro score: 5
|
-
Healthy adults
-
n=32
-
EG: (n=16), 27.6±4.3 years
-
CG (n=16), 25.8±4.1 years
|
Hand-held dynamometer /shoulder abduction, external and internal
rotation
|
Cable ER at 0◦ cable IR at 0◦ dumbbell scaption, and side-lying
dumbbell ER at 0◦
|
|
8wk 2 days/wk
|
resistance was increased by 1 lb (~0.45 kg) for individual
exercises
|
Greater increases in arm lean mass and isometric IR strength in
BFR group
|
|
BFR: blood flow restriction; CG: control group; EG: experimental
group; ER: external rotation, HIT: high intensity training; IR:
internal rotation; RM: repetition maximum.
|
Discussion
The limited published results indicate that BFRT may be an effective and safe method
for increasing upper extremity strength in healthy individuals. No complications
related to BFRT have been demonstrated in the existing studies. Five randomized
controlled studies were included in the systematic review. The aim of the current
systematic review is to evaluate the effects of BFRT on muscle strength in the upper
extremities. Comparing results is challenging due to the lack of standardized
exercise protocols with variations in exercise duration, frequency, and intensity
across studies. We maintain the viewpoint that standardization of cuff pressure and
parameters related to the exercise used in protocols for upper extremity BFRT is
necessary. In the examined five studies, BFR was successful in improving muscle
strength without causing pain, and this strength was equivalent to high-intensity
resistance training. Our review demonstrated that BFRT led to a strength increase in
upper extremities similar to the control group but did not show a significant
difference between groups.
In systematic reviews conducted on healthy individuals, variations in cuff pressure,
exercise durations, and dosages have been reported. The authors noted that a
standardized cuff pressure is not suitable and emphasized the importance of
personalized cuff pressure, along with the development of a model ensuring uniform
occlusion for all individuals. Upon examining the four studies in our systematic
review, cuff pressure was gradually increased in sessions to the extent tolerated by
the participants. In terms of the BFR protocol, three studies employed the
30-15-15-15 protocol. The protocol involves the first set of 30 repetitions followed
by a 30-second rest, the second set of 15 repetitions followed by a 30-second rest,
the third set of 15 repetitions followed by a 30-second rest, and the fourth set of
15 repetitions.
Numerous studies were included to examine the effects of BFRT on the upper and/or
lower extremities in healthy individuals in the systematic review conducted by Slysz
et al [20]. In their research, which
suggests the effectiveness of combining BFR with dynamic exercise training in
increasing both muscle strength and size, three out of 19 studies that measured
increases in muscle strength when exercise was combined with BFR focused on
restriction applied to the upper extremity. Despite differences in study designs,
these studies reported that low-intensity resistance training with BFR was effective
on muscle strength. The results of the studies in this research indicate that BFRT
could be used when traditional high-load training is inappropriate or inaccessible.
These results also support our findings that progress in upper extremity muscle
strength can be achieved without any reported complications. Our review revealed
that a minimum of 6 weeks is necessary to achieve gains related to strength. Even
though there was no standard BFR protocol, similar BFR protocols were used in the
three analyzed studies and demonstrating a positive impact on muscle strength.
It has been demonstrated that BFRT provides significant benefits in muscle
hypertrophy in both healthy individuals and elite athletes [10]. Determining the appropriate cuff
pressure, training duration, and dosage for upper extremity strengthening muscle
rehabilitation, and establishing whether an equivalent protocol to that used for
healthy individuals is necessary, requires further investigation. The primary
mechanisms responsible for these findings remain uncertain. With decreased blood
flow through BFRT, metabolic stress levels increase, there is an augmentation in
fast-twitch muscle fiber recruitment, cellular swelling is stimulated, systemic
hormones are elevated, and an ischemic/hypoxic environment that enhances the
production of reactive oxygen species is created [21]
[22]. The review of Hughes et
al. includes 20 studies regarding the use of BFR on the upper and/or lower
extremities in musculoskeletal rehabilitation. Four of these studies examine
resistance training combined with BFR applied to the upper extremities. Although
there is no standard protocol, no side effects have been reported [21]. Similarly, in our study, no
complications were reported. These results suggest that BFRexercise training applied
to the upper extremities in healthy individuals may be an alternative method to
high-intensity exercise training.
Individuals with hand osteoarthritis can benefit from strength trainings. In the
studies conducted by Magni and colleagues [15], the feasibility of two types of strength trainings in individuals
with symptomatic hand osteoarthritis was compared. According to the recommendations
of the American College of Sports Medicine, high-intensity exercises are frequently
suggested for hand osteoarthritis [23]. The
study compared high-intensity exercise with BFRexercise according to this
recommendation. The results of the study demonstrated that both strength training
applications were feasible, safe, and acceptable. It was reported that the majority
of participants completed the treatment, and the number of pain feedbacks was low
for both exercise procedures. Additionally, no improvement in function and
perception was observed in the study. The similarity of the training programs
highlights the need for larger randomized controlled trials.
Conclusion
This systematic review included five studies related to BFRT and its effects on upper
extremity muscle strength. While BFRT has become a popular method particularly in
lower extremity muscle strengthening programs in recent years, it has also started
to find its place in upper extremity programs. It is observed that there is a
limited number of studies addressing the BFR to the upper extremities when reviewing
literature on the effectiveness of BFRT on strength. Even though studies have
reported the efficacy of low-intensity resistance training with BFR on muscle
strength, due to the lack of uniform study protocols, there is no sufficient
evidence regarding the most effective BFR protocol for increasing upper extremity
muscle strength. There is also no reported side effect associated with its use in
the upper extremity. However, this review has several limitations. Firstly, the
limited number of participants reached due to the inadequacy of randomized
controlled trials. Secondly, only English articles were included. Thirdly, there
were variations in the characteristics of participants and sample sizes. Authors
planning future studies should aim to address these limitations by increasing sample
sizes, employing appropriate study designs, and providing clear and statistical
analysis results to enhance the quality of the studies.
Notice
This article was changed according to the following Erratum
on April 24th 2024.
Erratum
In the above-mentioned article, the institution affiliation for
Ecenur Atli has been corrected. Correct is that Ecenur Atli belongs
to this affiliation: 1 Graduate Education Institute, Physiotherapy
and Rehabilitation, Biruni University, Istanbul, Turkey.
