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Chronic effect of strength training with blood flow restriction on muscular strength among women with osteoporosis

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Chronic Effect of Strength Training with Blood Flow Restriction on Muscular Strength among Women with Osteoporosis. JEPonline 2015;18(4):33-41. The aim of this study was to analyze the chronic effect of strength training (ST) combined with blood flow restriction (BFR) on maximal dynamic strength (MDS) in osteoporotic women. Fifteen elderly women with osteoporosis, aged 62.2 ± 4.53 yrs, took part in the study. They were proportionally randomized into three groups: (a) low-intensity strength training with BFR (LI+BFR); (b) high intensity exercise (HI); and (c) control (CON). Experimental groups performed knee extensions for 12 wks, 2 times·wk-1. The CON subjects maintained their normal daily activities. They did not perform any type of exercise during the study period. The one-repetition maximum (1-RM) test was performed to assess MDS pre-test and at 6th-and 12th-wks. Outcomes showed significant increases in the MDS when the pre-test and the 12th-wk values were compared for the HI and LI+BFR groups (P<0.001; P=0.004), respectively. The ES of LI+BFR was also effective in improving MDS levels. Therefore, this method of intervention might be an effective alternative for special groups, particularly osteoporotic women.
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JEPonline
Chronic Effect of Strength Training with Blood Flow
Restriction on Muscular Strength among Women with
Osteoporosis
lio Silva1, Gabriel Rodrigues Neto1, Eduardo Freitas1, Elísio Neto1,
Gilmário Batista1, Mônica Torres2, Maria do Socorro Sousa1
1Physical Education Graduate Program, Federal University of Paraíba
(UFPB), Paraíba, PB, Brazil, 2State University of Rio de Janeiro
(UERJ), Rio de Janeiro, RJ, Brazil
ABSTRACT
Silva J, Neto GR, Freitas E, Pereira Neto E, Batista G, Torres M,
Sousa MS. Chronic Effect of Strength Training with Blood Flow
Restriction on Muscular Strength among Women with Osteoporosis.
JEPonline 2015;18(4):33-41. The aim of this study was to analyze the
chronic effect of strength training (ST) combined with blood flow
restriction (BFR) on maximal dynamic strength (MDS) in osteoporotic
women. Fifteen elderly women with osteoporosis, aged 62.2 ± 4.53
yrs, took part in the study. They were proportionally randomized into
three groups: (a) low-intensity strength training with BFR (LI+BFR); (b)
high intensity exercise (HI); and (c) control (CON). Experimental
groups performed knee extensions for 12 wks, 2 times·wk-1. The CON
subjects maintained their normal daily activities. They did not perform
any type of exercise during the study period. The one-repetition
maximum (1-RM) test was performed to assess MDS pre-test and at
6th- and 12th-wks. Outcomes showed significant increases in the
MDS when the pre-test and the 12th-wk values were compared for the
HI and LI+BFR groups (P<0.001; P=0.004), respectively. The ES of
LI+BFR was also effective in improving MDS levels. Therefore, this
method of intervention might be an effective alternative for special
groups, particularly osteoporotic women.
Keywords: Strength Training, Osteoporosis, Women, Kaatsu
Journal of Exercise Physiology
online
August 2015
Volume 18 Number 4
Editor-in-Chief
Tommy Boone, PhD, MBA
Review Board
Todd Astorino, PhD
Julien Baker, PhD
Steve Brock, PhD
Lance Dalleck, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
Alexander Hutchison, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
YitAun Lim, PhD
Lonnie Lowery, PhD
Derek Marks, PhD
CristineMermier, PhD
Robert Robergs, PhD
Chantal Vella, PhD
Dale Wagner, PhD
Frank Wyatt, PhD
Ben Zhou, PhD
Official Research Journal
of the American Society of
Exercise Physiologists
ISSN 1097-9751
Official Research Journal of
the American Society of
Exercise Physiologists
ISSN 1097-9751
34
INTRODUCTION
In Brazil, it is estimated that ~10 million people suffer from osteoporosis (9). According to the World
Health Organization (22), this disease is the second-largest health care problem in the world followed
by cardiovascular disorders. Osteoporosis is a metabolic bone disorder characterized by decreased
bone mineral density (BMD) with deterioration of the bone microarchitecture. The disorder occurs
most frequently after menopause (20). Combined with the decrease in muscle mass, BMD decreases
the capacity to produce strength that leads to increased skeletal fragility and fractures due to falls
(13). On the other hand, strength training (ST) is an excellent treatment to increase the size and
strength of the muscles to help maintain and/or increase BMD in people with osteoporosis (2). As a
result, there is anticipated reduction in the risk of falls along with an increase in functional capacity
(8).
Thus, high-intensity ST improves the performance of daily activities among older adults and people
with osteoporosis (21,28,26). The physiological mechanisms associated with high-intensity ST (≥
70% of one-repetition maximum, 1-RM) and improvements in BMD are attributed to the stress
imposed on the joints, the muscles, and the skeletal structures in which the muscles originate and
insert (6). Yet, several studies show that low-intensity ST (20 to 50% of 1-RM) combined with blood
flow restriction (BFR) produces similar strength and muscle mass gains without causing great stress
to the joints resulting from high-intensity ST (1,11,16). This means the combination of ST with BFR
may be a better alternative, especially at the beginning of the training sessions to increase muscle
strength and muscle mass in older adults.
The low-intensity ST with BFR method is carried out with the use of an inflatable cuff to restrict blood
flow to and from the muscles. The BFR results in significant intramuscular changes and neural activity
(25,27) that is associated with a rapid recruitment of type II motor units (18). These are also changes
observed in high-intensity ST that are important for developing strength, increasing muscle mass, and
improving functional capacity.
While the benefits of performing ST with BFR among older adults without osteoporosis are already
documented [e.g., increased muscle strength (10,30), improved bone markers (4,11,17), and
improved hormonal response (7,23)], the purpose of this study was to analyze the chronic effect of
strength training (ST) combined with BFR on maximal dynamic strength (MDS) in osteoporotic
women.
METHODS
Subjects
Fifteen osteoporotic women agreed to participate as subjects in this study. They were proportionally
randomized into three groups: (a) low-intensity ST group with blood flow restriction (LI+BFR); (b)
high-intensity ST group (HI); and (c) control group (CON), which was not exposed to exercise (refer to
Table 1 for subject characteristics). The sample size was calculated using G*Power 3.1® software
(Ausseldorf, Bundesland, Germany). Based on a post-hoc analysis, an alpha level of P≤0.05, a
correlation coefficient of 0.5, and an effect size of 0.80 were used for n = 15 subjects. We found that
the sample size was sufficient to provide 80.9% statistical power. To calculate the sample size, the
procedures suggested by Beck were adopted (3).
35
Table 1. Sample Characteristics.
Variables
Control
(n=5)
HI
(n=5)
LI+BFR
(n=5)
Age (yrs)
62.20 ± 4.08
62.60 ± 4.33
Height (cm)
152.96 ± 6.59
151.78 ± 5.99
Body Mass (kg)
58.52 ± 12
63.98 ± 11.91
Note: Values are expressed as the means ± standard deviations; HI = high-intensity group; LI+BFR = low-
intensity group combined with blood flow restriction.
Women with the following characteristics were included in the study: (a) chronological age greater
than 50 yrs; (b) six months without performing lower-limb strengthening activities; and (c) previous
diagnosis of osteoporosis with a T-score lower than -2.5 SD. After the study’s possible risks and
benefits were explained, the subjects signed an informed consent form prepared in accordance with
the Declaration of Helsinki. The study was approved by the Human Research Ethics Committee
under protocol no. 100/13.
Instruments
Determination of BFR
The BFR procedure was performed by vascular Doppler (MedPej® DV-2001, Ribeirão Preto, State of
São Paulo - SP, Brazil), in which the transducer was placed on the posterior tibial artery. A blood
pressure cuff (18 cm in width and 80 cm in length) was secured to the thigh (inguinal fold) and inflated
to the point that the auscultatory pulse of the tibial artery was interrupted (15). The tourniquet
pressure used during the training protocol was set as 80% of the pressure required for complete BFR
in the resting state (15). The cuff was deflated between the series. The mean pressure used
throughout the exercise protocol was 104.20 ± 7.88 mm Hg.
Maximum Strength Measure (1-RM)
The MDS (1-RM) was determined following the recommendations of the American Society of
Exercise Physiologists (5) and was performed using a leg extension machine (Body Fitness, Brazil)
unilaterally (right lower limb). The sample subjects were instructed not to perform physical activities or
strenuous efforts for at least 24 hrs prior to the tests. To warm up, a series of 5 to 10 repetitions of
knee extensions were performed on the same machine on which the test was performed, with a load
of 40% of the perceived 1-RM. After 1-min of rest, the subjects performed a second series of 3 to 5
repetitions with 60 to 80% of the perceived 1-RM load. Subsequently, the subjects tried to perform a
maximum repetition. The load was measured regardless of the goal being achieved or not. The
subjects had at most five attempts with 5-min intervals between them to allow for measurement of the
1-RM. In case the 1-RM could not be measured in these five attempts, this process was repeated
after 72 hrs. No pause was allowed between the concentric and the eccentric phase of a repetition or
between repetitions. The maximum strength was evaluated pre-test and at the 6th-wk and the 12th-
wk.
36
Procedures
ST Program
The ST program lasted 12 wks. It was designed with two weekly sessions separated by a 48-hr
interval (totaling 24 sessions). The exercise used was unilateral knee extension (right leg). The
experimental groups performed a 3-min warm-up on a stationary bicycle. The HI group performed the
exercise with four series until concentric failure with a load corresponding to 80% of 1-RM and a 2-
min rest interval between series (mean of 8.0 ± 2.01 repetitions per series; Figure 1A). The LI+BFR
group performed four series, until concentric failure, with a load corresponding to 30% of 1-RM, a 30-
sec rest interval between series (mean of 7.0 ± 3.38 repetitions per series), and the BFR using an
inflatable cuff (Figure 1B). The CON subjects maintained their normal daily activities without a
commitment to any type of physical exercise or strenuous activity involving the lower limbs throughout
the study’s intervention period and until the post-test was performed.
Statistical Analyses
The descriptive results are expressed as the means ± standard deviations. The effect size was used
to determine the magnitude of changes between the assessed time-points (24), and the percentage
variation (Δ%) was used to express possible differences in muscle strength between the first and the
third evaluations (post-test). Analysis of variance of repeated measures [3 x 3; protocols (BRF vs. HI
vs. CON) x time (pre-test vs. 6th-wk vs. 12th-wk)] followed by the Bonferroni’s post hoc test were
used to evaluate the effects of exercise for all dependent variables. The significance level adopted
was P≤0.05. No assumption of the use of the parametric statistics was violated. All analyses were
37
performed in the statistical software Statistical Package for the Social Sciences (SPSS) version 20.0
(SPSS Inc., Chicago, IL, USA).
RESULTS
In the intergroup comparison of the MDS, significant differences were observed at the 6th-wk when
evaluating LI+BFR vs.CON groups (P=0.004) and at the 12th-wk when evaluating LI+BFR vs. CON
and HI vs. CON groups (P=0.004 and P=0.017, respectively) (Table 2). In the intragroup analysis,
the HI group exhibited a significant difference when comparing pre- vs. 6th-wk, pre- vs. 12th-wk and
6th-wk vs. 12th-wk (P<0.001, ES = 1.44, ∆%= 18.35; P<0.001, ES= 2.77, ∆% = 34.5; P=0.002, ES =
1.39, ∆%= 13.65, respectively). For the LI+BFR group, there was a significant difference when
comparing pre- vs. 6th-wk and pre- vs. 12th-wk (P=0.006, ES = 5.71, ∆%= 0.30; P=0.004, ES = 0.63,
∆%= 10.59). The CON group did not exhibit significant differences between the three assessed time-
points (P>0.05).
Table 2. Comparative Analysis of Maximum Dynamic Strength (1-RM) between the Study
Groups.
RM
Control
HI
LI+BFR
Pre-
27.98 ± 3.74
27.78 ± 3.45
35.85 ± 6.72
6th- WK
27.94 ± 3.76
32.88 ± 3.21*
37.90 ± 5.71*
12th-WK
27.83 ± 3.58
37.37 ± 4.58*
40.10 ± 7.39*
Note: *Significant differences between pre- and 6th-wk, pre- and 12th-wk and 6th-wk and 12th-wk (P<0.05); HI
= high-intensity group; LI+BFR = low-intensity group combined with blood flow restriction.
DISCUSSION
This study analyzed the chronic effect of ST combined with BFR on the MDS of women with
osteoporosis. The data from this study show significant increases in MDS in the two assessment
time-points after the intervention program started in both experimental groups, but with no significant
differences between them. These results corroborate those obtained by Mosti et al. (19), who
observed increased maximum strength levels after a high-intensity intervention period (85 to 90% of
1-RM) over 12 wks. The same authors also observed improved BMD levels. In the study by Mosti et
al. (19), the exercises were performed 3 times·wk-1, while in the present study, the exercises were
performed 2 times·wk-1 without BFR. In the present study, considering that significant increases in
MDS were observed with and without BFR, we can infer that performing the exercises 2 times·wk-1
with and without BFR seems to be sufficient to observe increased MDS in the analyzed periods and
in the studied population. Thus, ST with BFR may be an alternative for improving MDS levels
provided that a high volume of exercise is performed (greater than or equal to 2 times·wk-1).
The effects of exercise with BFR for increasing muscle strength (11,29) are well known. This
improvement is justified by increased muscle hypertrophy and neuromuscular adaptations (29).
Several studies have also observed increased muscle strength when using ST with BFR in older
adults (10,12,30). However, to the best of our knowledge, the present study is the first to study the
effects of ST with BFR in a population of subjects with osteoporosis.
38
Based on studies by Karabulut et al. (10) and Yasuda et al. (30), it seems that performing ST with
BFR promotes increased muscle strength in older adults whether or not they have osteoporosis.
When analyzing the studies by Karabulut et al. (10) and Yasuda et al. (30) and comparing them to the
present study, one observes that even when exercises are performed unilaterally, strength gains may
be similar to those obtained when exercises are performed bilaterally (i.e., ST with BFR can be
performed both unilaterally and bilaterally to increase the strength of older adults). Thus, we
speculate that there was an increase in muscle strength levels for the LI with BFR and HI groups and
that a consequent increase in MDS would occur. This result would be a counterpoint for the assertion
that high-intensity and high-impact ST would be the only effective way of increasing levels of strength,
hypertrophy, and gain in the formation or maintenance of bone mass (21,26,28).
Several studies have observed positive effects of ST with BFR on bone markers (4,11,17). Although
ST with BFR has shown positive effects for bone metabolism, and its contribution for the recovery of
bone trauma has been reported (17), it is not yet clear how this training affects bone metabolism. In a
study conducted with a population of elderly men (11) that used the knee extension exercise with
BFR, positive responses were observed in osteoblast activity and muscle strength. Similarly, Kim et
al. (14) reported positive increases in both bone turnover markers and muscle cross-sectional area in
older adults who trained with and without BFR. However, subjects who performed high-intensity
training exhibited the greatest gains and showed improved bone turnover, based on higher responses
of the bone anabolic marker for that type of exercise. Similarly, Bemben et al. (4) observed that, after
a session of ST with BFR, the analyses of bone markers of absorption and reabsorption indicated an
increase in osteoblast activity and a decrease in osteoclast activity. Thus, ST with BFR seems to be
effective for developing bone tissue because it indicates a positive response in bone rehabilitation
(14). Based on the above and on the articles mentioned previously, it seems that similarly to high-
intensity ST, ST with BFR can improve bone markers.
Thus, based on the abovementioned findings and the data from the present study, ST performed in
combination with BFR is effective for increasing MDS in the elderly population with osteoporosis.
Because improvements in bone markers were observed in other studies with the use of BFR, it is
reasonable to expect that this method will be an alternative intervention in this population. However,
further studies are needed to assess the efficacy of using ST with BFR in the BMD of elderly
populations with osteoporosis. Therefore, we recommend that high- and low-intensity training with
BFR be used to prevent and control osteoporosis.
CONCLUSIONS
Low-intensity ST combined with BFR seems to be effective for increasing MDS in elderly women with
osteoporosis. Thus, this method seems to be an effective alternative for special population groups,
especially in women with osteoporosis.
Address for correspondence: Neto GR, MD, Department of Physical Education - Associate
Graduate Program in Physical Education UPE / UFPB, Federal University of Paraíba, University City,
Research Center for Human Movement Sciences, Kinanthropometry Laboratory, Room 06 and 08.
Castelo Branco. João Pessoa 58051-900, Brazil. / Phone: 55 083 9612-2726 E-mail:
gabrielrodrigues_1988@hotmail.com
39
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... In general, the groups that performed LI-RT in BFR conditions showed significant improvements in different strength measurements compared with LI-RT in non-BFR conditions (see Table 1). Among the sixteen studies, thirteen performed resistance training [7,15,18,22,30,37,40,[50][51][52][53][54][55] and three aerobic training [1,26,27] with BFR ( Fig. 1). ...
... Light-intensity resistance training in non-BFR conditions did not show significant increases in strength measurements. However, similar improvements in strength between LI-RT in BFR condition and HI-RT non-BFR groups were also reported [40,50,51]. Related to the aerobic training programs with BFR, some studies [1,26,27] reported increases in the knee extension isometric strength ranging from 5.9 to 11.8%, the knee extension isokinetic strength (N/m) ranging from 7 to 8.7%, as well as in the knee flexion isokinetic strength (N/m) ranging from 16 to 22% [1,26,27]. ...
... Importantly, similar improvements in resistance training with BFR compared to the traditional HI-RT non-BFR groups have also been reported [40,50,51]. In the study of Silva et al. [40], conducted on women with osteoporosis, the HI-RT non-BFR group showed higher improvements in 1RM leg extension compared to the LI-RT group with BFR (HI-RT non-BFR group: mean increase post-intervention 9.59 kg; and LI-RT with BFR group: mean increase postintervention 4.25 kg). ...
Article
Full-text available
Background Low-intensity resistance training (LI-RT) combined with blood flow restriction (BFR) is an alternative to traditional moderate–high-intensity resistance training to increase strength and muscle mass. However, the evidence about the efficacy of this novel training method to increase strength and muscle mass in healthy and older adults with pathologies is limited. Furthermore, the possible risk and adverse effects with BFR training methodology in older adults should be considered. Objectives (1) To summarize the current evidence on training with BFR strategies in older adults aiming to improve strength and to increase muscle mass; and (2) to provide recommendations for resistance and aerobic training with BFR in older adults based on the studies reviewed. Methods Studies that investigated the chronic responses to resistance training or aerobic training with BFR related to strength and muscle mass changes in older adults were identified. Two independent researchers conducted the search in PubMed, Web of Science, and Google Scholar databases from their inception up to November 1, 2018. Results Seventeen out of 35 studies, which performed resistance or aerobic training with BFR in older adults focused on strength and muscle mass outcomes, were included in this review. Studies performing resistance and aerobic training with BFR found better improvements in strength and higher increase in muscle mass compared to non-BFR groups that performed the same training protocol. High-intensity resistance training (HI-RT) without BFR provided greater improvements in strength and a similar increase in muscle mass compared to light-intensity resistance training (LI-RT) with BFR. Conclusions Current evidence suggests that LI-RT and/or aerobic training with BFR improves strength and increases muscle mass in older people. Light-intensity training without BFR would normally not obtain such benefits. Therefore, LI-RT and aerobic training with BFR is an alternative to traditional methods to improve strength and by way of an increase in muscle mass, which are important in the elderly who have progressive muscle atrophy and are at higher risk of falls.
... Low-load (LL) resistance training (RT; i.e., 20-30% of one repetition maximum [1RM]) combined with blood flow restriction (BFR) emerged in the 1960s but gained greater notoriety in the 2000s 1 as an alternative method for individuals who cannot perform high-intensity exercises (i.e., ≥ 65% of 1RM). In this context, this training method has been shown to effectively increase muscle strength [2][3][4][5] , muscular hypertrophy 2,5 , localized muscular endurance 4,6,7 , isometric force 8 , and functional capacity 9 . Furthermore, it has been shown to be safe in relation to hemodynamics 10-14 . ...
... The muscle activity of the pectoralis and back was not verified because the heart beat might have interfered with the electromyographic signal. The BFR pressure used was verified for the dorsal decubitus, but the positions of the four exercises were performed in different positions; however, these procedures are commonly performed in the literature [2][3][4]6,8,11,12 . ...
Article
Full-text available
Resistance training (RT) with blood flow restriction (BFR) has been used to increase muscle strength and hypertrophy, however, the best strategy to perform BFR (continuous or intermittent) has not yet been established. The aim of this study was to analyze the chronic effect of RT with continuous or intermittent blood flow restriction (CBFR or IBFR) on muscle activation. A total of 24 men with RT experience were randomly divided into three experimental groups: low-load exercises at 20% of one repetition maximum (1RM) combined with CBFR (LL + CBFR), low-load exercises at 20% of 1RM combined with IBFR (LL + IBFR), or low-load exercises at 20% of 1RM without BFR (LL). Twelve RT sessions were performed for 6 weeks, twice a week. A comparative analysis of the activation of the biceps and triceps brachial muscles after the bench press, triceps pulley, and biceps pulley exercises did not reveal group × evaluations × sets, group × evaluations, group × sets, or evaluations × sets interactions with regard to group, evaluation, or sets (p > 0.05). However, the evaluations showed a significant increase in the LI+IBFR group after the 1st, 2nd, and 4th sets (p < 0.05) only with regard to biceps muscle activation. It was concluded that the muscle activations of the biceps and triceps are similar with regard to the bench press, triceps pulley, and biceps pulley exercises when CBFR is compared with IBFR; however, IBFR improved the muscle activation of the biceps brachial only with regard to the front pull down exercise.
... In fact, BFR-RE incorporates exercise loads corresponding to 20 to 30% of an individual's one-repetition maximum (1-RM), rather than loads exceeding 70% of a person's 1-RM [8,9]. In this regard, BFR-RE is an appealing exercise modality for improving or maintaining muscle parameters when HL-RE is contraindicated, such as when working with clinical populations [10][11][12]. ...
Article
The purpose of the current investigation was to compare the acute perceptual responses during low-load resistance exercise (RE) with clinical blood flow restriction (cBFR-RE) and practical blood flow restriction (pBFR-RE), and during conventional low- (LL-RE) and high-load resistance exercise (HL-RE), to determine if these responses differed between young males and females. Twenty-nine participants (14 males: 23.6±2.7years, 25.3±3.1kg/m² and 15 females: 20.3±1.6years, 23.4±1.9kg/m²) completed the following exercise conditions in a randomized design: 1) cBFR-RE, 2) pBFR-RE, 3) HL-RE, and 4) LL-RE. Low-load conditions consisted of 30-15-15-15 repetitions of two-leg press (LP) and knee extension (KE) exercises with 30% one-repetition maximum (1-RM), and HL-RE consisted of 3 sets of 10 repetitions at 80% 1-RM, all with 60s rest intervals. Ratings of perceived exertion (RPE) and discomfort were assessed before exercise and immediately following each set. RPE was significantly higher in HL-RE compared to all low-load conditions for both exercises after each set (all p<0.05). cBFR-RE resulted in significantly greater RPE than pBFR-RE and LL-RE for both exercises for sets 1-4 for LP and sets 2-3 for KE (all p<0.05). Levels of discomfort were similar between cBFR-RE and HL-RE, which tended to be significantly higher than pBFR-RE and LL-RE (p<0.05). Men reported significantly greater RPE than women following sets 2-4 during KE with cBFR-RE and sets 2 and 3 during KE for HL-RE (all p<0.05). Males also reported significantly greater discomfort than women following sets 2-4 for KE LL-RE (p<0.05). Altogether, these data suggest that pBFR-RE may provide a more favorable BFR condition based on perceptual responses and that perceptual responses may differ between sexes across varying resistance exercise conditions.
... Low-intensity resistance exercise (RE; 20% and 30% one-repetition maximum; 1RM) in combination with blood flow restriction (BFR) has been used to increase strength (Laurentino et al., 2012; Silva et al., 2015; Vechin et al., 2015), hypertrophy (Laurentino et al., 2012; Vechin et al., 2015), functional capacity (Araujo et al., 2015), and local muscle endurance (Gil et al., 2015; Kacin & Strazar, 2011 ), and it has been found safe with respect to hemodynamics (Arau´joArau´jo et al., 2014; Fahs et al., 2011; Neto et al., 2015; Takano et al., 2005; Vieira, Chiappa, Umpierre, Stein, & Ribeiro, 2013). This training method may be used on different special populations because it reduces impact on the joints (Loenneke, Wilson, Marı´nMarı´n, Zourdos, & Bemben, 2012; Scott, Loenneke, Slattery, & Dascombe, 2015 ) and enables gains in muscle strength and hypertrophy similar to those resulting from high-intensity (HI) training (Laurentino et al., 2012; Takarada, Takazawa, et al., 2000). ...
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The present study aimed to analyse the effects of six weeks of strength training (ST), with and without blood flow restriction (BFR), on torque, muscle activation, and local muscular endurance (LME) of the knee extensors. Thirty-seven healthy young individuals were divided into four groups: high intensity (HI), low intensity with BFR (LI+BFR), high intensity and low intensity + BFR (COMB), and low intensity (LI). Torque, muscle activation and LME were evaluated before the test and at the 2nd, 4th and 6th weeks after exercise. All groups had increased torque, muscle activation and LME (p<0.05) after the intervention, but the effect size and magnitude were greater in the HI, LI+BFR and COMB groups. In conclusion, the groups with BFR (LI+BFR and COMB) produced magnitudes of muscle activation, torque and LME similar to those of the HI group.
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ABSTRACT: The present study aimed to analyse the effects of six weeks of strength training (ST), with and without blood flow restriction (BFR), on torque, muscle activation, and local muscular endurance (LME) of the knee extensors. Thirty-seven healthy young individuals were divided into four groups: high intensity (HI), low intensity with BFR (LI+BFR), high intensity and low intensity + BFR (COMB), and low intensity (LI). Torque, muscle activation and LME were evaluated before the test and at the 2nd, 4th and 6th weeks after exercise. All groups had increased torque, muscle activation and LME (p<0.05) after the intervention, but the effect size and magnitude were greater in the HI, LI+BFR and COMB groups. In conclusion, the groups with BFR (LI+BFR and COMB) produced magnitudes of muscle activation, torque and LME similar to those of the HI group.
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We investigated the acute and chronic effects of low-intensity concentric or eccentric resistance training with blood flow restriction (BFR) on muscle size and strength. Ten young men performed 30% of concentric one repetition maximal dumbbell curl exercise (four sets, total 75 reps) 3 days/week for 6 weeks. One arm was randomly chosen for concentric BFR (CON-BFR) exercise only and the other arm performed eccentric BFR (ECC-BFR) exercise only at the same exercise load. During the exercise session, iEMG for biceps brachii muscles increased progressively during CON-BFR, which was greater (p<0.05) than that of the ECC-BFR. Immediately after the exercise, muscle thickness (MTH) of the elbow flexors acutely increased (p<0.01) with both CON-BFR and ECC-BFR, but was greater with CON-BFR (11.7%) (p<0.01) than ECC-BFR (3.9%) at 10-cm above the elbow joint. Following 6-weeks of training, MRI-measured muscle cross-sectional area (CSA) at 10-cm position and mid-upper arm (12.0% and 10.6%, respectively) as well as muscle volume (12.5%) of the elbow flexors were increased (p<0.01) with CON-BFR. Increases in muscle CSA and volume were lower in ECC-BFR (5.1%, 0.8% and 2.9%, respectively) than in the CON-BFR and only muscle CSA at 10-cm position increased significantly (p<0.05) after the training. Maximal voluntary isometric strength of elbow flexors was increased (p<0.05) in CON-BFR (8.6%), but not in ECC (3.8%). These results suggest that CON-BFR training leads to pronounced acute changes in muscle size, an index of muscle cell swelling, the response to which may be an important factor for promoting muscle hypertrophy with BFR resistance training.
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Beck, TW. The importance of a priori sample size estimation in strength and conditioning research. J Strength Cond Res 27(8): 2323-2337, 2013-The statistical power, or sensitivity of an experiment, is defined as the probability of rejecting a false null hypothesis. Only 3 factors can affect statistical power: (a) the significance level (α), (b) the magnitude or size of the treatment effect (effect size), and (c) the sample size (n). Of these 3 factors, only the sample size can be manipulated by the investigator because the significance level is usually selected before the study, and the effect size is determined by the effectiveness of the treatment. Thus, selection of an appropriate sample size is one of the most important components of research design but is often misunderstood by beginning researchers. The purpose of this tutorial is to describe procedures for estimating sample size for a variety of different experimental designs that are common in strength and conditioning research. Emphasis is placed on selecting an appropriate effect size because this step fully determines sample size when power and the significance level are fixed. There are many different software packages that can be used for sample size estimation. However, I chose to describe the procedures for the G*Power software package (version 3.1.4) because this software is freely downloadable and capable of estimating sample size for many of the different statistical tests used in strength and conditioning research. Furthermore, G*Power provides a number of different auxiliary features that can be useful for researchers when designing studies. It is my hope that the procedures described in this article will be beneficial for researchers in the field of strength and conditioning.
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KAATSU training involves the restriction of blood flow to exercising muscle and is the culmination of nearly 40 years of experimentation with the singular purpose of increasing muscle mass. KAATSU Training consists of performing low-intensity resistance training while a relatively light and flexible cuff is placed on the proximal part of one's lower or upper limbs, which provides appropriate superficial pressure. KAATSU Training should not be confused with training under ischemic conditions which has previously been reported (Sundberg, 1994). KAATSU Training does not induce ischemia within skeletal muscle, but rather promotes a state of blood pooling in the capillaries within the limb musculature. Applied basic and clinical research conducted over the past 10 years has demonstrated that KAATSU Training not only improves muscle mass and strength in healthy volunteers, but also benefits patients with cardiovascular and orthopedic conditions.