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Low intensity blood flow restriction training: A meta-analysis

Authors:
  • Applied Science and Performance Institute
  • CyMO Research Institute, Spain

Abstract and Figures

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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ORIGINAL ARTICLE
Low intensity blood flow restriction training: a meta-analysis
Jeremy P. Loenneke Jacob M. Wilson
Pedro J. Marı
´nMichael C. Zourdos
Michael G. Bemben
Received: 23 July 2011 / Accepted: 3 September 2011
ÓSpringer-Verlag 2011
Abstract 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 pop-
ulations 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 resul-
ted 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.
Keywords KAATSU Hypertrophy Strength
Vascular occlusion training
Introduction
The American College of Sports Medicine (ACSM) rec-
ommends lifting a weight of at least 70% 1RM to achieve
muscular hypertrophy as it is believed that anything below
this intensity rarely produces substantial muscle growth
(ACSM 2009). However, numerous studies using low
intensity exercise combined with blood flow restriction
(LI-BFR) have shown muscle hypertrophy to occur with a
training intensity as low as 20% 1RM (Abe et al. 2005b,c;
Madarame et al. 2008; Yasuda et al. 2010). In further
support of LI-BFR, a recent review looking at potential
safety issues of this type of training concluded that it
offered no greater risk than traditional exercise (Loenneke
et al. 2011). LI-BFR has been combined with several dif-
ferent types of exercise (e.g. knee extension, knee flexion,
leg press, cycling, walking, elbow flexion, bench press) and
most have observed significant increases in muscle
hypertrophy (Abe et al. 2006,2010a,b; Madarame et al.
Communicated by Susan A. Ward.
J. P. Loenneke (&)M. G. Bemben
Department of Health and Exercise Science,
The University of Oklahoma, 1401 Asp Avenue,
Room 104, Norman, OK 73019-0615, USA
e-mail: jploenneke@ou.edu
J. M. Wilson
Department of Exercise Science and Sport Studies,
University of Tampa, Tampa, FL, USA
P. J. Marı
´n
Department of Health Sciences, European University Miguel
de Cervantes, Valladolid, Spain
M. C. Zourdos
Department of Nutrition, Food and Exercise Sciences,
The Florida State University, Tallahassee, FL, USA
123
Eur J Appl Physiol
DOI 10.1007/s00421-011-2167-x
2008; Takarada et al. 2000; Yasuda et al. 2010), strength
(Abe et al. 2006,2010a,b; Madarame et al. 2008; Takarada
et al. 2000; Yasuda et al. 2010), and endurance (Kacin and
Strazar 2011). Interestingly, although increases in skeletal
muscle hypertrophy and strength do not typically occur
from an ‘‘Aerobic’’ mode of exercise, increased size and
strength have been observed from both slow walk training
(Abe et al. 2006) and cycling combined with LI-BFR (Abe
et al. 2010a). Previous literature has discussed the benefits
and mechanisms of blood flow restricted training in depth
[for reviews please see (Loenneke and Pujol 2009;
Loenneke et al. 2010; Manini and Clark 2009; Wernbom
et al. 2008; Loenneke and Pujol 2011)].
Published studies hypothesize 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. Proposed mechanisms include increased fiber
type recruitment, metabolic accumulation, stimulation of
muscle protein synthesis, and cell swelling, although it is
likely that many of the aforementioned mechanims work
together.
Throughout the LI-BFR literature there exist many
significant differences in study design, specifically with
respect to different training variables (e.g. mode of exer-
cise, days per week, duration, rest intervals, exercise
intensity, exercise volume). Little work has been com-
pleted to identify which variables are the most important to
consider when designing an optimal LI-BFR training pro-
gram. A robust and quantitative approach to the problem
can be provided in the form of a meta-analysis of the data.
The primary objective of this investigation was to quanti-
tatively identify which training variables result in the
greatest strength and muscle hypertrophy outcomes when
combining low intensity exercise with blood flow
restriction.
Methods
Literature search
Searches were performed for published studies with a
number of 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, to be con-
sidered for our analysis, subject populations had to have
similar baseline characteristics (e.g. both untrained and
trained) so that valid outcome measures could be made.
Finally, the outcome measures had to include at least one
measure of muscle hypertrophy as this is currently sug-
gested to be a primary mechanism responsible for all
outcome measures of functionality (Loenneke et al. 2010).
Studies reporting muscle hypertrophy as a percentage
increase were excluded due to the inability to calculate an
effect size. All studies included in the analysis utilized
MRI except for two which reported changes in hypertrophy
via ultrasound. In addition, due to the paucity of data on LI-
BFR of the upper body, only studies investigating the lower
body were included. Electronic databases searched inclu-
ded Science Citation Index, National Library of Medicine,
Sport Discus, Google Scholar, and MEDLINE were sear-
ched in February 2011 back to the earliest available time
that met the specifications of this meta-analysis when Abe
et al. (2005c) published a foundational study on blood flow
restriction training.
Exclusion of studies with irrelevant content and doublets
was carried out in three steps. First, the titles of the articles
were read, followed by reading of the abstracts, and finally
the entire article was read. The reference lists of relevant
articles were, in turn, scanned for additional articles
(published or unpublished) that met the inclusion criteria.
Conference abstracts and proceedings were excluded.
Relevant studies were selected and searched for data nec-
essary to compute effect size and descriptive information
regarding the training protocol. Table 1is composed of all
studies meeting our meta-analysis requirements and
Table 2lists the studies excluded from analysis.
Coding of studies
Each study was read and coded by the primary investigator
for descriptive information including gender and training
experience. For both endurance and resistance training, we
coded for frequency, mean training intensity, volume
(duration of endurance and sets of strength training), and
type of training split utilized. For training, frequency was
coded by the number of days per week that participants
trained their lower bodies. Pressure of the cuff was coded
through a range dependent upon the initial and final pres-
sure of each study. Volume for resistance and endurance
training, respectively, was coded as number of repetitions
performed, and average duration of the endurance training
session. Because the range of repetitions was not large
enough to compare within modes we compared total vol-
ume of work between all modalities. Training status was
defined as untrained, recreationally active, trained, and
athlete. Participants must have been performing a struc-
tured resistance-training program for at least 1 year prior to
the study’s onset in order to be considered as trained. In
order to be considered for the athlete category, participants
must have been competitive athletes at the collegiate or
professional level. As described previously by Rhea et al.
(2003) all studies included in the analysis were coded twice
by the primary investigator to minimize coder drift.
Eur J Appl Physiol
123
Calculation and analysis of effect size
Pre- and post-effect sizes (ES) were calculated with the
following formula: [(Posttest mean -pretest mean)/pre-
test standard deviation]. ES were then adjusted for sample
size bias (Rhea 2004; Rhea et al. 2003). This adjustment
consists of applying a correction factor to adjust for a
positive bias in smaller sample sizes. Descriptive statistics
were calculated and univariate analysis of variance by
groups was used to identify differences between training
status, gender, and age with level of significance set at
P\0.05. When a significant Fvalue was achieved, pair-
wise comparisons were performed using a Bonferroni post-
hoc procedure. All calculations were made with SPSS
statistical software package v.19.0 (SPSS Inc., Chicago,
IL). The scale proposed by Rhea (2004) and Rhea et al.
(2003) was used for interpretation of effect size magnitude.
Coder drift was assessed by coding and then recoding all
studies meeting our inclusion criteria. Per case agreement
was determined by dividing the variables coded the same
by the total number of variables (Rhea 2004; Rhea et al.
2003). The mean agreement for this analysis was 0.98.
Results
Overall ES and moderating variables are presented in
Tables 3and 4. The 48 ES for muscle strength (28 ES for
LI-BFR training and 20 ES for low intensity training) and
60 ES for muscle hypertrophy (31 ES for LI-BFR training
and 29 ES for low intensity training) were obtained from a
total of 11 primary studies which met our criteria
(Table 1).
Muscular strength
The mean overall ES for muscle strength for LI-BFR
training was 0.58 [95% CI: 0.40, 0.76], and 0.00 [95% CI:
-0.18, 0.17] for low intensity training (Table 1). Signifi-
cant differences were found between blood flow restriction
training and low intensity training (P\0.05).
Moderating variables for LI-BFR training
Untrained groups gained more muscle strength than
recreationally active groups, 1.38 [95% CI: 1.01, 1.76;
n=6] versus 0.37 [95% CI: 0.17, 0.57; n=21]
(P\0.05), respectively (Table 3). Significant differences
were found between 2–3 days per week and 4–5 day per
week, 1.25 [95% CI: 0.84, 1.67; n=5] versus 0.53 [95%
CI: 0.21, 0.86; n=10], respectively (P\0.05), as well as
between 4–5 days per week and 6–7 days per week, 0.53
[95% CI: 0.21, 0.86; n=10] versus 0.29 [95% CI: 0.00,
Table 1 Studies included in the analysis
Citation Age
(years)
Gender Training
status
Exercise mode Exercise
intensity
Frequency of
training
Length of
training
Protocol Measure of
hypertrophy
Abe et al.(2005c)\25 M Rec. active Squat and knee flexion 20% 1RM 129week 2 weeks 3 sets of 15 repetitions; 30 sec rest MRI
Abe et al.(2005b)\25 M Athlete Squat and knee flexion 20% 1RM 149week 8 days 3 sets of 15 repetitions; 30 sec rest Ultrasound
Abe et al.(2006)\25 M Rec. active Treadmill walking 50 M/Min 129week 3 weeks 52-min walking bouts; 1 min rest MRI
Abe et al.(2009)\25 M Rec. active Treadmill walking 50 M/Min 69week 3 weeks 52-min walking bouts; 60 sec rest MRI
Abe et al.(2010b)[50 M/F Rec. active Treadmill walking 67 M/Min 59week 6 weeks 20 minutes walking Ultrasound
Abe et al.(2010a)\25 M Rec. active Cycling 40% VO
2max
39week 8 weeks 15 minutes cycling MRI
Beekley et al.(2005)\25 M Rec. Active Treadmill walking 50 M/Min 129week 3 weeks 52-min walking bouts; 60 sec rest MRI
Fujita et al.(2008)\25 M Rec. Active Knee extension 20% 1RM 129week 6 days 30-15-15-15 repetitions; 30 sec rest MRI
Kacin and Strazar (2011)\25 M Rec. Active Unilateral knee extension 15% MVC 49week 4 weeks 4 sets to volitional fatigue MRI
Madarame et al.(2008)\25 M Untrained Knee extension and knee flexion 30% 1RM 29week 10 weeks 30,15,15 repetitions; 30 sec rest MRI
Ozaki et al.(2011)[50 M/F Untrained Treadmill walking 45% HRR 49week 10 weeks 20 minutes walking MRI
Eur J Appl Physiol
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Table 2 Studies excluded from the analysis
Citation Age
(years)
Gender Training
status
Exercise mode Length Of
training
Reason for exclusion
Abe et al.(2005a) 47 M Rec. active Knee extension 7 days Case study
Clark et al. (2010)\25 M/F Untrained Knee extension 4 weeks Hypertrophy not measured
Cook et al. (2010) 18–50 M/F Not reported Knee extension 4 weeks Training status not reported/atrophy model
Evans et al. (2010)\25 M Rec. Active Heel raises 4 weeks Hypertrophy not measured
Gualano et al. (2010) 65 M N/A Leg press, knee extension, squat 12 weeks Myopathy case study
Ishii et al. (2005) 25–50 F Untrained Knee up, bent-knee push up, leg
raise, knee flexion, squat, lunge
8 weeks Simultaneous upper and lower body blood flow restriction
Karabulut et al. (2010)[50 M Untrained Leg press, knee extension 6 weeks Hypertrophy not measured
Karabulut et al. (2011)[50 M Untrained Leg press, knee extension 6 weeks Hypertrophy not measured
Kim et al. (2009)\25 M Untrained Leg press, knee extension, knee flexion 3 weeks Hypertrophy measured by DXA
Ohta et al. (2003) 18–52 M/F Rec. active Rehabilitation exercises 16 weeks Rehabilitation from surgery
Park et al. (2010)\25 M Athlete Treadmill walking 2 weeks Hypertrophy not measured
Patterson and Ferguson (2010)\25 F Rec. active Unilateral plantar flexion 4 weeks Hypertrophy not measured
Sakuraba and Ishikawa (2009)\25 M Athlete Isokinetic knee flexion/knee extension 4 weeks Hypertrophy not measured in control group
Sata (2005)\25 M Rec. Active Hip abduction, hip adduction, calf
raise, squat, crunch, etc.
6 weeks Patella tendinitis case study
Shinohara et al. (1998)\25 M Untrained Isometric contractions 4 weeks Hypertrophy not measured
Sumide et al. (2009)\25 M Untrained Straight leg raise, hip joint abduction, hip joint
adduction
8 weeks Hypertrophy not measured in control group
Takarada et al. (2002)[50 F Untrained Knee extension 8 weeks Hypertrophy Reported As % Change
Takarada et al. (2004)\25 M Athlete Knee extension 8 weeks Hypertrophy reported as % change
Yasuda et al. (2005) 20–47 M Not reported Squat and knee flexion 2 weeks Training status not reported
Eur J Appl Physiol
123
0.58; n=12] (P\0.05), respectively (Table 3). Signifi-
cant differences were found between B4 and 10 weeks of
duration, 0.27 [95% CI: 0.03, 0.52; n=13] versus 1.38
[95% CI: 1.02, 1.75; n=6] (P\0.05), respectively
(Table 3). The isotonic exercise mode improved more
muscle strength than walking exercise mode, 1.08 [95%
CI: 0.69, 1.46; n=8] versus 0.42 [95% CI: 0.16, 0.67;
n=18) (P\0.05), respectively (Table 3). Significant
differences were found between exercise intensity 15–30%
MVC/1RM and 50–60 m/min, 1.08 [95% CI: 0.69, 1.46;
Table 3 Effect size for muscle strength
Overall LI-BFR Low intensity
Mean (95% CI)
0.58* (0.40, 0.76)
N=28 PMean (95% CI)
-0.00 (-0.18, 0.17)
N=20 P
Moderators
Gender
Male 0.58 (0.29, 0.97) 19 [0.05 0.08 (-0.03, 0.20) 11 \0.05
Female I.D. I.D.
Both 0.58 (0.16, 1.01) 9 -0.20 (-0.37, -0.02) 9
Training status
Untrained 1.38 (1.01, 1.76) 6 \0.05 0.32 (0.13, 0.51) 6 \0.05
Recreationally active 0.37 (0.17, 0.57) 21 -0.10 (-0.20, -0.00) 21
Athletes I.D. I.D.
Days per week
2-3 1.25 (0.84, 1.67) 6 \0.05 0.27 (0.07, 0.47) 6 \0.05
4-5 0.53 (0.21, 0.86) 10 -0.17 (-0.32, -0.14) 10
6-7 0.29 (-0.00, 0.58) 12 -0.00 (-0.15, 0.13) 12
Week of duration
B4 0.27 (0.03, 0.52) 13 \0.05 0.00 (-0.03, 0.04) 19 [0.05
5–8 0.49 (0.20, 0.79) 9 -0.05 (-0.11, 0.15) 7
9–10 1.38 (1.02, 1.75) 6 I.D.
Exercise mode
Isotonic 1.08 (0.69, 1.46) 8 \0.05 0.28 (0.11, 0.44) 8 \0.05
Walking 0.42 (0.16, 0.67) 18 -0.12 (-0.23, -0.02) 18
Cycling I.D. 0.28 (0.11, 0.44)
Exercise intensity
15–30% MVC/1RM 1.08 (0.69, 1.46) 8 \0.05 0.28 (0.12, 0.44) 8* \0.05
50–60 (m/min) 0.25 (-0.10, 0.61) 9 -0.05 (-0.20, 0.09) 9
40–45% HRR/VO
2max
0.50 (0.17, 0.83) 11 -0.17 (-0.30, -0.03) 11*
Repetitions
60–70 1.37 (0.98, 1.76) 6 \0.05 0.32 (0.13, 0.51) 6 \0.05
Failure I.D. I.D.
14–20 (min) 0.39 (0.17, 0.60) 20 -0.11 (-0.22, -0.01) 20
Rest period (s)
0 0.50 (0.19, 0.80) 11 \0.05 -0.17 (-0.30, -0.03) 11 \0.05
30 1.22 (0.83, 1.60) 7 0.30 (0.13, 0.47) 7
60 0.25 (-0.08, 0.58) 9 -0.05 (-0.20, 0.09) 9
120 I.D. I.D.
Cuff pressure (mmHg)
140–220 0.50 (0.12, 0.88) 11 [0.05
160–240 0.67 (0.35, 0.99) 16
230 I.D.
Overall ES and moderating variables for muscular strength. I.D. insufficient data (\5 ESs)
* Significant difference from low intensity training (P\0.05)
Eur J Appl Physiol
123
n=8] versus 0.42 [95% CI: -0.10, 0.61; n=9]
(P\0.05), respectively (Table 3). The total volume of
work done in a workout, of about 60–70 repetitions
improved more muscle strength than 14–20 min of
walking, 1.37 [95% CI: 0.98, 1.76; n=6] versus 0.39
[95% CI: 0.17, 0.60; n=20) (P\0.05), respectively
(Table 3). Significant differences were found between 0 s
rest periods and 30 s rest periods, 0.50 [95% CI: 0.19, 0.80;
Table 4 Effect size for muscle hypertrophy
Overall LI-BFR Low Intensity
Mean (95% CI)
0.39* (0.35, 0.43)
N=31 PMean (95% CI)
-0.01 (-0.05, 0.03)
N=29 P
Moderators
Gender
Male 0.42 (0.37, 0.47) 25 \0.05 0.00 (-0.02, 0.03) 25
Female I.D. I.D.
Both 0.26 (0.16, 0.37) 6 I.D.
Days per week
2–3 0.48 (0.38, 0.58) 6 \0.05 -0.00 (-0.07, 0.06) 6 [0.05
4–5 0.27 (0.18, 0.37) 7 I.D.
6–7 0.41 (0.35, 0.47) 18 -0.00 (-0.04, 0.04) 18
Week of duration
B4 0.41 (0.34, 0.47) 19 [0.05 0.00 (-0.03, 0.04) 19 [0.05
5–8 0.39 (0.29, 0.49) 9 -0.05 (-0.11, 0.01) 7
9–10 I.D. I.D.
Exercise mode
Isotonic 1.08 (0.69, 1.46) 8 \0.05 0.02 (-0.02, 0.06) 13 [0.05
Walking 0.42 (0.16, 0.67) 18 -0.05 (-0.10, -0.05) 12
Cycling I.D. I.D.
Exercise intensity
15–30% MVC/1RM 1.08 (0.69, 1.46) 8 \0.05 0.02 (-0.02, 0.069 13 [0.05
50–60 (m/min) 0.25 (-0.10, 0.61) 9 -0.02 (-0.08, 0.03) 8
40–45% HRR/VO
2max
0.50 (0.17, 0.83) 11 -0.05 (-0.11, 0.00) 8
Lower strength assessment
Isokinetic I.D. [0.05 I.D. [0.05
Isotonic 0.33 (0.26, 0.41) 7 -0.03 (-0,10, 0.03) 7
Isometric 0.37 (0.30, 0.44) 7 0.00 (-0.06, 0.07) 7
Repetitions
60–70 I.D. \0.05 I.D. [0.05
Failure I.D. I.D.
14–20 (min) 0.36 (0.30, 0.42) 18 -0.03 (-0.07, 0.00) 16
45 (rep) 0.51 (0.43, 0.60) 8 0.03 (-0.01, 0.09) 8
Rest period (s)
0 0.37 (0.28, 0.46) 10 [0.05 -0.05 (-0.10, 0.00) 8 [0.05
30 0.44 (0.36, 0.53) 12 0.00 (-0.03, 0.05) 12
60 0.35 (0.25, 0.45) 8 -0.02 (-0.08, 0.03) 8
120 I.D. I.D.
Cuff pressure (mmHg)
140–220 0.37 (0.28, 0.46) 10 [0.05
160–240 0.41 (0.34, 0.44) 20
230 I.D.
Overall ES and moderating variables for muscular hypertrophy. I.D. insufficient data (\5 ESs)
* Significant difference from low intensity training (P\0.05)
Eur J Appl Physiol
123
n=11] versus 1.22 [95% CI: 0.83, 1.60; n=7]
(P\0.05), respectively, as well as between 30 and 60 s
rest periods, 1.22 [95% CI: 0.83, 1.60; n=7] versus 0.25
[95% CI: -0.08, 0.58; n=9] (Table 3). Correlational
analysis identified significant relationships (P\0.01)
between ESfor strength development and weeks of training
duration (r=0.67).
Muscular hypertrophy
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 (Table 4). Sig-
nificant differences were found between occlusion training
and low intensity training (P\0.05).
Moderating variables for LI-BFR training
An analysis of the differences in hypertrophy gains
achieved for blood flow restriction training was performed
in males as compared to combined gender groups to
determine whether gender influenced hypertrophy gains.
The male group gained more hypertrophy than the com-
bined group, 0.42 [95% CI: 0.37, 0.47; n=25] versus 0.26
[95% CI: 0.16, 0.37; n=6] (P\0.05), respectively
(Table 4). Significant differences were found between
2–3 days per week and 4–5 days per week, 0.48 [95% CI:
0.38, 0.58; n=6] versus 0.27 [95% CI: 0.18, 0.37; n=7],
respectively (P\0.05). The isotonic exercise mode
improved more muscle hypertrophy than the walking
exercise mode, 0.44 [95% CI: 0.34, 0.47; n=13] versus
0.31 [95% CI: 0.25, 0.38; n=14) (P\0.05), respectively
(Table 4). Significant differences were found between
exercise intensity 15–30% MVC/1RM and 50–60 m/min
walking speed, 1.08 [95% CI: 0.69, 1.46; n=8] versus
0.25 [95% CI: -0.10, 0.61; n=9]. The total volume of
work done in a workout with 45 repetitions improved more
muscle hypertrophy than 14–20 min of walking, 0.51 [95%
CI: 0.43, 0.60; n=8] versus 0.36 [95% CI: 0.30, 0.42;
n=18] (P\0.05), respectively (Table 4).
No significant relationships were found (P[0.05)
between ES for hypertrophy and weeks of duration.
Discussion
The findings of this meta-analysis confirm previous ACSM
recommendations that regular low intensity resistance
training (not to muscular failure) does not provide an
adequate stimulus to produce substantial increases in
strength or muscle hypertrophy. However, when that same
low intensity exercise is combined with blood flow
restriction, significant increases are found comparable to a
previous meta-analysis using higher intensities (HIT)
(Krieger 2010) with both strength (LI-BFR 0.58 vs. HIT
0.80) and muscle hypertrophy (LI-BFR 0.39 vs. HIT 0.35).
To our knowledge, this is the first meta-analysis completed
on this novel mode of training, which shows the overall
effect from manipulating different variables for training
adaptation.
Subject characteristics
Subjects who were previously untrained have greater
increases in muscular strength than those who were
recreationally active. This may also provide some expla-
nation for the lower effect size observed with strength in
the LI-BFR cohort compared to a previous meta-analysis
on HIT resistance training which was composed almost
exclusively of untrained subjects. No such comparison
could be made for hypertrophy as a result of insufficient
data from available studies. No studies meeting our criteria
have been completed investigating LI-BFR using only
females, thus for this analysis males were compared to a
combined group made up of both males and females (males
vs. males/females). The combined group observed signifi-
cantly less muscle hypertrophy than the male only group,
possibly due to a buffering effect of females. This would be
consistent with previous research demonstrating that
women experience smaller changes in muscle size com-
pared with men (Ivey et al. 2000). A comparison across age
groups could not be made due to insufficient data from the
studies included in this analysis.
Training frequency
The analysis found that strength and muscle hypertrophy
were both significantly greater in the groups performing
exercise 2–3 days per week compared to those exercising
4–5 days per week. It is possible that the gains were
attenuated in the 4–5 day/week group from an overtraining
response, even though the external resistance was low,
however, it is more likely this overtraining response is
more reflective of the frequency of training rather than the
days trained per week, since 4 out of 7 studies in the
4–5 day/week group trained twice per day.
Training duration
This investigation found that although the ES for muscular
hypertrophy remains fairly constant from \4 weeks of
training to 10 or more weeks of training, muscular strength
responds much differently. The ESindicate that muscular
strength does not significantly increase until the 10 week
time point (Fig. 1). This finding is interesting because
traditionally it has been thought that neural adaptations
Eur J Appl Physiol
123
increase strength during the first couple of weeks of exer-
cise and muscle hypertrophy occurs later on in the training
([6 weeks). These data suggest that perhaps the traditional
training adaptation paradigm is reversed with LI-BFR
exercise. This may help to explain the findings of studies
which report that the strength gains from LI-BFR exercise
are a product of muscle hypertrophy and not neural adap-
tation (Fujita et al. 2008; Takarada et al. 2002,2000;
Yasuda et al. 2011). All of those studies with the exception
of one (Takarada et al. 2000) trained \8 weeks. If the
findings from this analysis are accurate and representative,
then it is conceivable that neural adaptations for LI-BFR
exercise do not occur until much later in the training pro-
gram, and studies lasting \10 weeks would be unlikely to
produce relative strength gains (maximal voluntary
strength per unit muscle cross sectional area). In further
support, correlational analyses found a significant rela-
tionship between the ES for strength and weeks of training,
with no significant correlation found for hypertrophy. This
possible reversal in the neural adaptation finding warrants
further investigation before these phenomena can be
definitively acknowledged. It is also possible that this
finding is spurious and exclusive only to the two long-term
(9–10 weeks) studies included in this analysis. While this
finding is far from conclusive; however, Fig. 2graphically
depicts the possible theoretical interaction between
strength, hypertrophy, and neural adaptations during both
traditional resistance training, and LI-BFR exercise.
Fig. 1 The effect sizes (ES) for
muscle strength and
hypertrophy with low intensity
blood flow restriction (LI-BFR)
as it relates to duration of
training
Fig. 2 Graphical
representation of the theoretical
interaction between strength,
hypertrophy, and neural
adaptations during both
traditional resistance training
(T-RT), and low intensity blood
flow restricted exercise (LI-
BFR) is shown. During T-RT
strength increases at first
primarily by changes in
muscular hypertrophy followed
latter by neural adaptations. For
LI-BFR the opposite pattern
may occur (adapted from Sale
1988)
Eur J Appl Physiol
123
Training modality and intensity/volume
The results indicate that isotonic exercise improved mus-
cular strength and hypertrophy to a greater degree than
walking. This difference is likely related to the amount of
work completed by the muscle as well as the accumulation
of metabolites. With resistance training, specific muscles
are easily isolated and the metabolic accumulation is much
larger than that observed with walking, which further
highlights the importance of metabolic accumulation for
ideal outcomes in strength and hypertrophy. An additional
mechanism responsible for adaptations caused by LI-BFR
may be acute cell swelling as this has been shown to
stimulate an anabolic response in hepatocytes (Haussinger
1996). Regardless of the mechanism, significant differ-
ences exist between isotonic resistance training and walk-
ing with LI-BFR. Therefore, individuals capable of
performing low intensity resistance training with blood
flow restriction will see larger increases in strength and
muscle hypertrophy compared to those walking with blood
flow restriction. Subsequent alterations in muscular
strength and muscle hypertrophy outcomes were also sig-
nificantly dependent upon exercise intensity. To illustrate,
resistance training with 15–30% MVC/1RM produced
greater strength and size gains compared to walking at
50–60 m/min. However, these results are likely to be an
artifact of the exercise modality, which the aforementioned
analysis demonstrated can impact the overall effect. Sim-
ilar results are present in relation to volume of exercise and
rest interval. For example, greater gains in strength and size
were found; however, the only two comparisons were made
between repetitions completed and minutes walked. In
addition, this analysis found that 30 s of rest between sets
produced much greater strength gains than 60 s; however,
every study using 60 s rest was a walking study. Thus, we
suggest that future investigators specifically analyze the
question of volume within a given exercise modality.
Cuff pressures
Throughout the literature, numerous cuff pressures are
used. Often, training studies begin at an overall low pres-
sure and progress to high pressures throughout the training
programs. For this analysis, two of our groups have over-
lap, but differed at where the initial training pressures
began (140 vs. 160 mmHg) and where the final training
pressures ended (160–240 mmHg). This overlap may have
led to the non-significant finding, however it may also
indicate that the absolute pressure needed for muscular
adaptation is much less than commonly thought, especially
when using a wider cuff to induce blood flow restriction
(Crenshaw et al. 1988). In support of this, evidence sug-
gests that higher restrictive cuff pressures (200 mmHg) are
no more effective at increasing intramuscular metabolites
than moderate pressures (*150 mmHg or 130% systolic
BP) when using a wide (18.5 cm) cuff (Suga et al. 2010).
The impact of cuff width was not able to be made from the
current analysis, since most studies in this meta-analysis
used a narrow cuff (5 cm), therefore the overall impact of
cuff width on training adaptation remains unknown. Cur-
rent research on acute LI-BFR exercise (Wernbom et al.
2008) and the data from this analysis do not suggest that
higher pressures would be more effective than lower
pressures for inducing training adaptations. However, no
study to date has examined the impact of progressively
increasing or maintaining restrictive cuff pressure during
LI-BFR training so it is not clear if progressive increases in
restrictive cuff pressure are necessary to produce muscular
strength or hypertrophy.
Limitations for endurance-based outcomes
The primary focus of our meta-analysis was the effects of
blood flow restriction training on hypertrophy and strength
training. However, it should be emphasized that our results
do not necessarily apply to other outcomes such as
endurance performance. For example, we found that
greater training frequencies may not be ideal for hyper-
trophy and strength gains; however, they may be beneficial
for endurance outcomes. This was illustrated by Kacin and
Strazar (2011) who found that high frequency (49week)
LI-BFR resulted in small gains in hypertrophy, and no
significant increases in strength. However, they found that
the blood flow restricted group increased endurance per-
formance by 63% as compared to 36% in the control
condition. Moreover, while our results strongly indicate
that a resistance exercise mode is ideal for strength and
hypertrophy, a number of researchers have demonstrated
that cycling under ischemic conditions may be a highly
effective mode for increasing muscular endurance (Kaijser
et al. 1990; Nygren et al. 2000; Sundberg et al. 1993). For
the reason that endurance adaptations are an important, yet
understudied, component of LI-BFR exercise training we
suggest future research attempt to disseminate exactly what
the ideal prescription is for those particular outcomes.
Conclusions
This meta-analysis provides insight into the overall impact
of different training variables on muscular strength and
hypertrophy to LI-BFR training. Although only 11 studies
met the inclusion criteria for this meta-analysis, general
recommendations can be made from the results and pat-
terns observed from this study. This analysis provides
evidence and recommendations for future studies to use in
Eur J Appl Physiol
123
order to maximize the muscular strength and hypertrophy
response to this novel mode of training. It appears that
blood flow restriction combined with low intensity
resistance exercise produces a much greater response
than blood flow restricted walking. Furthermore, LI-BFR
training 2–3 days per week appears to maximize the
training adaptation and there is some evidence that the
neural adaptation to LI-BFR training does not occur at
the beginning of a training program as it does with
traditional resistance training. It appears that initial
increases in strength may be due solely to muscle
hypertrophy, while the neural impact on strength gains
may occur much later with LI-BFR training. Although
this finding may be true with LI-BFR training, longer-
term studies are needed before a definitive conclusion
can be made.
Conflict of interest The authors report no conflict of interest.
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... Therefore, different groups of individuals and a wide array of BFR protocols have been examined [30][31][32][33]. However, most of these studies have enrolled healthy participants with a focus on physical performance outcomes and body composition change [23,34,35] or physiological responses [24,36,37]. On the other hand, only a few studies have focused on assessing the adverse effects of long-term BFR training [33,[38][39][40]. ...
... The physiological mechanisms underlying muscle adaptation from BFR are widely studied, and it seems that increased fast-twitch fiber recruitment [53][54][55], decreased myostatin expression [56], satellite cell proliferation [57], and acute muscle cell swelling may contribute to the anabolic response of BFR during low-load resistance training [22]. Recent literature has shown that low-load BFR resistance training outperforms bodyweight or low-load training without BFR [34]. Moreover, it may even produce effects similar to moderate-heavy resistance training, including increases in muscle strength and muscle mass [34], cardiovascular capacity [58], and performance in specific tasks [59]. ...
... Recent literature has shown that low-load BFR resistance training outperforms bodyweight or low-load training without BFR [34]. Moreover, it may even produce effects similar to moderate-heavy resistance training, including increases in muscle strength and muscle mass [34], cardiovascular capacity [58], and performance in specific tasks [59]. Therefore, if BFR resistance training would be deemed a safe alternative to high-intensity strength training for glaucoma patients and those at risk for glaucoma, it could mitigate the potential side effects of high-intensity resistance training while still reaping its benefits. ...
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Despite the many health benefits of resistance training, it has been suggested that high-intensity resistance exercise is associated with acute increases in intraocular pressure which is a significant risk factor for the development of glaucomatous optic nerve damage. Therefore, resistance training using a variety of forms (e.g., resistance bands, free weights, weight machines, and bodyweight) may be harmful to patients with or at risk of glaucoma. An appropriate solution for such people may involve the combination of resistance training and blood flow restriction (BFR). During the last decade, the BFR (a.k.a. occlusion or KAATSU training) method has drawn great interest among health and sports professionals because of the possibility for individuals to improve various areas of fitness and performance at lower exercise intensities. In comparison to studies evaluating the efficiency of BFR in terms of physical performance and body composition changes, there is still a paucity of empirical studies concerning safety, especially regarding ocular health. Although the use of BFR during resistance training seems feasible for glaucoma patients or those at risk of glaucoma, some issues must be investigated and resolved. Therefore, this review provides an overview of the available scientific data describing the influence of resistance training combined with BFR on ocular physiology and points to further directions of research.
... This is especially true considering low-load BFR exercise has been shown to produce superior hypertrophy when compared with work-matched low-load exercise alone and similar hypertrophy to high-load training. 28,35 The accelerated fatigue experienced in the working muscle during low-load BFR exercise is thought to enhance the perceptual experiences of the exerciser due to a proximity to failure from the restricted blood flow attenuating oxygen delivery compared with free-flow exercise. 56,57 Therefore, low-load exercise with BFR may be expected to increase the RPE response compared with low-load exercise. ...
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Context Several studies have compared perceptual responses between resistance exercise with blood flow restriction and traditional resistance exercise (non-BFR). However, the results were contradictory. Objectives To analyze the effect of RE+BFR versus non-BFR resistance exercise [low-load resistance exercise (LL-RE) or high-load resistance exercise (HL-RE)] on perceptual responses. Data Sources CINAHL, Cochrane Library, PubMed ® , Scopus, SPORTDiscus, and Web of Science were searched through August 28, 2021, and again on August 25, 2022. Study Selection Studies comparing the effect of RE+BFR versus non-BFR resistance exercise on rate of perceived exertion (RPE) and muscle pain/discomfort were considered. Meta-analyses were conducted using the random effects model. Study Design Systematic review and meta-analysis. Level of Evidence Level 2. Data Extraction All data were reviewed and extracted independently by 2 reviewers. Disagreements were resolved by a third reviewer. Results Thirty studies were included in this review. In a fixed repetition scheme, the RPE [standardized mean difference (SMD) = 1.04; P < 0.01] and discomfort (SMD = 1.10; P < 0.01) were higher in RE+BFR than in non-BFR LL-RE, but similar in sets to voluntary failure. There were no significant differences in RPE in the comparisons between RE+BFR and non-BFR HL-RE; after sensitivity analyses, it was found that the RPE was higher in non-BFR HL-RE in a fixed repetition scheme. In sets to voluntary failure, discomfort was higher in RE+BFR versus non-BFR HL-RE (SMD = 0.95; P < 0. 01); however, in a fixed scheme, the results were similar. Conclusion In sets to voluntary failure, RPE is similar between RE+BFR and non-BFR exercise. In fixed repetition schemes, RE+BFR seems to promote higher RPE than non-BFR LL-RE and less than HL-RE. In sets to failure, discomfort appears to be similar between LL-RE with and without BFR; however, RE+BFR appears to promote greater discomfort than HL-RE. In fixed repetition schemes, the discomfort appears to be no different between RE+BFR and HL-RE, but is lower in non-BFR LL-RE.
... BFR-LLST (20-40% of 1-Repetition Maximum (RM)) requires much less external loading than traditional strength training (70-80% of 1RM). BFR-LLST produces positive training adaptations, such as muscle hypertrophy and increased strength in the lower extremity in healthy subjects, and patients with knee pathology [27,47,73,79]. The underlying mechanisms are not fully understood, but may stem from a complex interplay of reduction in oxygen delivery to the muscle (hypoxia), accumulation of metabolites, muscle fiber recruitment and proliferation of myogenic stem cells [56,63,69]. ...
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Purpose Blood flow restriction – low load strength training (BFR-LLST) is theoretically superior to traditional heavy strength training when rehabilitating patients who cannot heavily load tissues following surgery. The main purpose of this study was to examine the feasibility of BFR-LLST added to usual care exercise early after cartilage or meniscus repair in the knee joint. Methods We included 42 patients with cartilage ( n = 21) or meniscus repair ( n = 21) of the knee joint. They attended 9 weeks of BFR-LLST added to a usual care exercise program at an outpatient rehabilitation center. Outcome measures were assessed at different time points from four (baseline) to 26 weeks postoperatively and included adherence, harms, knee joint and thigh pain, perceived exertion, thigh circumference (muscle size proxy), isometric knee-extension strength, self-reported disability and quality of life. Results On average, patients with cartilage or meniscus repair completed > 84% of the total BFR-LLST supervised sessions. Thirty-eight patients reported 146 adverse events of which none were considered serious. No decrease in thigh circumference or exacerbation of knee joint or quadriceps muscle pain of the operated leg was found in either group during the intervention period. Conclusions BFR-LLST added to usual care exercise initiated early after cartilage or meniscus repair seems feasible and may prevent disuse thigh muscle atrophy during a period of weight bearing restrictions. Harms were reported, but no serious adverse events were found. Our findings are promising but need replication using a RCT-design. Trial registration NCT03371901 , preprint (open access): https://www.medrxiv.org/content/10.1101/2022.03.31.22272398v1
... However, there could be some individuals who are unwilling or incapable of exercising at a high-intensity and/or for a prolonged duration (e.g., elderly population, patients undergoing rehabilitation). For these individuals, the addition of blood flow restriction may offer an alternative method of exercise by inducing a similar hypoalgesic response to exercise with higher loads (Loenneke et al., 2012). ...
Article
Purpose: To 1) examine whether blood flow restriction would provide an additional exercise-induced hypoalgesic response at an upper and lower limb when it is incorporated with low-load resistance exercise until failure, and 2) examine if increases in blood pressure and discomfort, with blood flow restricted exercise, would mediate the exercise-induced hypoalgesia over exercise without blood flow restriction. Methods: Forty healthy young participants completed two trials: four sets of unilateral knee extension exercise to failure at 30% of one-repetition maximum, with and without blood flow restriction. Pressure pain thresholds were assessed before (twice) and 5-min post exercise at an upper and lower limb. Blood pressure and discomfort ratings were recorded to examine mediating effects on exercise-induced hypoalgesia with blood flow restricted exercise. Results: Pressure pain threshold increased following both exercise conditions compared to a control, without any differences between exercise conditions at the upper (exercise conditions vs. control: ~0.37 kg/cm²) and lower (exercise conditions vs. control: ~0.60 kg/cm²) limb. The total number of repetitions was lower for exercise with blood flow restriction compared to exercise alone [median difference (95% credible interval) of −27.0 (−29.8, −24.4) repetitions]. There were no mediating effects of changes in blood pressure, nor changes in discomfort, for the changes in pressure pain threshold at either the upper or lower limb. Conclusion: The addition of blood flow restriction to low-load exercise induces a similar hypoalgesic response to that of non-blood flow restricted exercise, with a fewer number of repetitions.
... Muscular and systemic adaptations can be achieved through numerous resistance training methodologies by manipulating the different resistance training variables (i.e., type of exercise and materials used, frequency, intensity, volume) (Garber et al., 2011). In this regard, the combination of blood flow restriction (BFR) with resistance training is a relatively new methodology that induces similar or even greater muscle adaptations than exercising with the same or greater loads without BFR (D. Kim et al., 2017;Loenneke et al., 2014Loenneke et al., , 2012Pope et al., 2013;. BFR consists of the application of a blood pressure cuff that restricts blood flow to the main muscles involved in the exercise Patterson et al., 2019;. ...
Article
Objective: To determine the effect of blood flow restriction (BFR) applied to the legs at different pressures (40% and 60%) on intraocular pressure (IOP) during the execution of ten repetitions maximum (10RM) in the half-squat exercise. Methods: Quasi-experimental, prospective study with 17 healthy physically active subjects (9 males and 8 females; 24.1 ± 4.2 years). Two sessions were conducted. The 10RM load was determined in the first session. The second session consisted of 10RM under three BFR conditions (no-BFR, 40%-BFR, and 60%-BFR) that were applied in random order. IOP was measured before each condition, immediately after each repetition, and after 1 minute of passive recovery. A two-way repeated-measures ANOVA (restriction type [no-BFR, 40%-BFR, and 60%-BFR] x measurement point [basal, repetitions 1–10, and recovery]) was applied on the IOP measurements. Results: A significant main effect of the BFR condition (p = .022, ƞp² = 0.21) was observed due to the significantly higher mean IOP values for the 60%-BFR (19.0 ± 0.7 mmHg) compared to the no-BFR (18.0 ± 0.8 mmHg; p = .048, dunb = 1.30). Non-significant differences with a large effect size were reached between 60%-BFR and 40%-BFR (18.1 ± 0.8 mmHg; p = .081, dunb = 1.16) and between no-BFR and 40%-BFR (p = .686, dunb = 0.18). IOP increased approximately 3–4 mmHg from baseline to the last repetition. Conclusions: Low-pressure BFR (40%-BFR) in combination with moderate-load (10RM load) resistance exercise could be an effective and safe strength training strategy while avoiding IOP peaks associated with heavy-load resistance exercises. These findings incorporate novel insights into the most effective exercise strategies in individuals who need to maintain stable IOP levels (e.g., glaucoma patients).
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: Blood flow restriction therapy (BFRT) involves the application of a pneumatic tourniquet cuff to the proximal portion of the arm or leg. This restricts arterial blood flow while occluding venous return, which creates a hypoxic environment that induces many physiologic adaptations. ➢: BFRT is especially useful in postoperative rehabilitation because it produces muscular hypertrophy and strength gains without the need for heavy-load exercises that are contraindicated after surgery. ➢: Low-load resistance training with BFRT may be preferable to low-load or high-load training alone because it leads to comparable increases in strength and hypertrophy, without inducing muscular edema or increasing pain.
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The purpose of this study was to investigate once-daily walk training with restricted leg blood flow (KAATSU) on thigh muscle size and strength. Twelve young men performed walk training: KAATSU-walk training (n=6) and control (no KAATSU-walk; n=6). Training was conducted once daily, 6 days per week, for 3 weeks. Treadmill walking (50 m/min) was performed for 5 sets of 2-min bouts interspersed with 1-min rest periods. The KAATSU-walk group wore pressure cuff belts (5 cm wide) on both legs during training, with incremental increases in external compression starting at 160 mmHg and ending at 230 mmHg. Thigh muscle volume and isometric and 1-repetition maximal (1-RM) strength were measured before and after training. In the KAATSU-walk group, quadriceps and hamstrings muscle volume increased 1.7 and 2.4% (both P<0.05), respectively, following training. One-RM leg press and leg curl increased 7.3 and 8.6% (both P<0.05), respectively, following KAATSU-walk training. Also, isometric knee extension strength (4.4%; P<0.01), but not knee flexion strength (1.7%), increased following KAATSU-walk training. There were no changes in muscle volume or strength in the control-walk group. These results confirm previous work showing that the combination of slow walk training and leg muscle blood flow restriction induces muscle hypertrophy and strength gains. However, the magnitude of change in muscle mass and strength following once-daily KAATSU-walk training was approximately one-half that reported for twice-daily KAATSU-walk training over a 3-week period. These results in combination with previous observations lead to the conclusion that the impact of KAATSU-walk training on muscle size and strength is related to an ability to accomplish a high number of training bouts within a compressed training duration. Second, frequency-dependent muscle enlargement appears to be associated with KAATSU-walk training.
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The purpose of this study was to investigate the effects of short-term KAATSU-resistance training on skeletal muscle size and sprint/jump performance in college athletes. Fifteen male track and field college athletes were randomly divided into two groups: KAATSU (resistive exercise combined with blood flow restriction, n=9) and control (n=6) groups. The KAATSU group trained twice daily with squat and leg curl exercises (20% of 1-RM, 3 sets of 15 repetitions) for 8 consecutive days while both KAATSU and control groups participated in the regular sprint/jump training sessions. Maximal strength, muscle-bone CSA, mid-thigh muscle thickness (MTH), and sprint/jump performance were measured before and after the 8 days of training. The muscle-bone CSA increased 4.5% (p 0.05) in the control group. Quadriceps and hamstrings MTH increased (p 0.05) in the control group. Overall 30-m dash times improved (p 0.05) for either the KAATSU or control groups. These data indicated that eight days of KAATSU-training improved sprint but not jump performance in collegiate male track and field athletes.
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Traditional high-intensity resistance training performed 2-3 times per week induces muscle hypertrophy, at least, in 5 weeks (i.e. 10-15 training sessions). To examine the effect of a higher training frequency (12 sessions in 6 days), healthy young men performed low-intensity resistance training with (n=8, LIT-BFR) and without (n=8, LIT-CON) leg blood flow restriction with cuff inflation (BFR) twice per day for 6 days. Training involved 4 sets of knee extension exercise (75 total contractions) at 20% 1-RM. Significant muscle hypertrophy was observed only in the LIT-BFR group as estimated muscle-bone cross-sectional area (CSA) (2.4%), MRI-measured mid-thigh quadriceps muscle CSA (3.5%) and quadriceps muscle volume (3.0%) increased. The resulting hypertrophic potential (% change in muscle size divided by number of training sessions; ∼0.3% per session) is similar to previously reported traditional high-intensity training (0.1 to 0.5% per session). Improved 1-RM knee extension strength (6.7%) following LIT-BFR training was accounted for by increased muscle mass as relative strength (1-RM/CSA) did not change. There was no apparent muscle damage associated with the exercise training as blood levels of creatine kinase, myoglobin, and interleukin-6 remained unchanged throughout the training period in both training groups. A single bout of training exercise with and without BFR produced no signs of blood clotting as plasma thrombin-antithrombin complex, prothrombin fragment 1,2 and D-dimer were unchanged. In conclusion, changes in muscle mass and strength following 6-day (12 sessions) of low-intensity resistance training requires BFR to produce responses comparable to the effect of several weeks of high-intensity resistance training.
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Low-intensity Kaatsu resistance training performed by patients with moderate vascular occlusion is known to cause skeletal muscle hypertrophy over a short term. In our patients who used such training as a part of their rehabilitation, we have seen the same results, as well as a quenching analgesic effect. Herein, we report the effect of Kaatsu resistance training in a patient with patella tendinitis. The patient was a 17-year-old male who played basketball and came to us with intense pain at the lower edge of the patella in the right knee and was confirmed by an MRI image which showed a high intensity signal in the area of the patella tendon. Initially, we gave a dose of antiphlogistic analgetic, a steroid injection, and prescribed hospitalization for 1 month. Kaatsu resistance training was also recommended in an attempt to prevent muscle atrophy. The vascular occlusion point for the Kaatsu training cuff was the proximal end of the right limb, which had an occlusion pressure ranging from 160-180 mmHg. The exercise components that were used in combination with the Kaatsu training program were SLR, hip abduction, hip adduction, calf raise, toe raise, squat, crunch, back extension, and shooting. The exercise protocol was performed at about 30% of 1RM, with 3 sets of 15 repetitions, 5 to 6 times per week, for 3 weeks. T2 weighted MRI images (axial and sagittal) of the right patella tendon prior to beginning Kaatsu training showed high intensity signals, however, after 3 weeks of Kaatsu training, the signal intensity was reduced and the thigh circumference was increased by 7 mm and 2 mm for the right and left sides, respectively. Further, there was no evidence of muscle atrophy. The present patient was then treated with appropriate anti-inflammatory drugs and 1-month of hospitalization. During that time it was possible to completely relieve the inflammation and avoid muscle atrophy with Kaatsu training, and the patient quickly returned to playing basketball. In conclusion, this low-intensity resistance training was able to be performed without applying excessive load, which may have caused further damage, and we intend to use Kaatsu training with future patients to help them return as early as possible to full activities.
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Previous studies have shown that low-intensity resistance training with restricted blood flow, known as KAATSU training, increases muscle strength and size. Its effects on blood vessel function, however, have not been examined. We compared the effects of a short-term KAATSU resistance training protocol and traditional high-intensity resistance training on muscle strength and blood vessel function in young, untrained men. Male volunteers were randomly assigned to a KAATSU resistance training group (KR, n=10), a traditional resistance training group (RT, n=10), or a KAATSU-only group (K, n=10). Both KR and RT groups trained 3 times per week for 3 weeks doing leg press (LP), knee flexion (KF), and knee extension (KE) isotonic resistance exercises. Training sessions consisted of 5-10 min of warm-up, followed by 2 sets of 10 repetitions at 80% of 1 repetition maximum (1-RM) for the RT group, while the KR group performed the resistance exercises with vascular restriction at a load of 20% of 1-RM. The K group had only the vascular restriction treatment for 3 weeks. Muscle strength (1-RM) and arterial compliance (pulse contour analysis) were assessed at baseline and after training. Both the KR and RT groups did not show changes in arterial compliance of the large or small arteries (P>0.05) after training. There were significant time effects (P<0.05 pre- vs. posttraining); however, resistance training generally resulted in greater relative improvements in strength. Arterial compliance of the large and small arteries was not affected by the either the KAATSU or traditional high-intensity resistance training interventions.
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The purpose of this study was to examine the daily skeletal muscle hypertrophic and strength responses to one week of twice daily KAATSU training, and follow indicators of muscle damage and inflammation on a day-to-day basis, for one subject. KAATSU training resulted in a 3.1% increase in muscle-bone CSA after 7 days of training. Both MRI-measured maximum quadriceps muscle cross-sectional area (Q-CSA max) and muscle volume can be seen increasing after the first day of KAATSU training, and continuously increasing for the rest of the training period. Following 7 days KAATSU resistance training, the increases in Q-CSA max and muscle volume were 3.5% and 4.8%, respectively. Relative strength (isometric knee extension strength per unit Q-CSA max) was increased after training (before, 3.60 Nm/cm2; after, 4.09 Nm/cm2). There were very modest increases in CK and myoglobin after a single bout of KAATSU exercise in the first day of the training, but the values were return towards normal at 2 days after the training. IL-6 remained unchanged throughout the training period. In conclusion, our subject gained absolute strength and increased muscle size after only one week of low intensity KAATSU resistance training. Indicators of muscle damage and inflammation were not elevated by this training. KAATSU training appears to be a safe and effective method to rapidly induce skeletal muscle strength and hypertrophy.
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The present study investigated whether circuit training with body weight alone (no external load) can cause muscular hypertrophy when combined with moderate venous occlusion (‘Kaatsu Training’). Healthy women (mean age, 32.7 ± 4.0 yr; n=22) were randomly assigned into the occlusive training group (OCC, n=11) and the normal training group (NOR, n=11). Both groups performed the same circuit-training regimen consisting of six, successive exercises for muscles in the upper and lower limbs and the trunk, at a frequency of 3 sessions/wk. Each session lasted for 5-10 min. In OCC group, proximal ends of the upper and lower limbs of both sides were moderately compressed by means of ‘KAATS Sportswear’, to restrict the venous blood flow during the exercises (preset pressure, 50-80 mmHg and 80-120 mmHg for upper and lower limbs, respectively). Cross-sectional area (CSA) of the thigh muscle was measured with spiral computer tomography. After an 8-wk period of training, the muscle CSA of both right and left limbs showed significant increases by ∼3% (P<0.05) in the OCC group, whereas there was no change for the NOR group. To propose a mechanism for these findings, the acute effects of the same exercise regimen combined with occlusion on plasma concentration of growth hormone (GH) were further investigated with male subjects (n=2). The circuit exercise with occlusion elicited a dramatic increase in plasma GH, whereas that without occlusion did not, although statistical analysis could not be made. The results indicate that circuit training with only body weight can cause hypertrophy in lower-limb muscles when combined with moderate venous occlusion, but the exact mechanism is not yet understood.