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The use of a single resistance exercise with or without blood flow restriction in the treatment of pain in knee osteoarthritis: a randomized clinical trial

ABSTRACT

BACKGROUND AND OBJECTIVES:

Physical exercise is an efficient non-pharmacological strategy for the treatment of knee osteoarthritis (KOA). Blood flow restriction (BFR) is a technique known to enhance strength and hypertrophy gains when combined with low-intensity resistance exercise. This study aimed to analyze the effects of 12 weeks of low-intensity resistance training with and without blood flow restriction (BFR) on pain control and strength improvement in patients with KOA.

METHODS:

Two intervention groups performed low-intensity resistance exercise (knee joint extension on the leg extension chair at 30% of one repetition maximum) with (LI+BFR, n=13) or without blood flow restriction (LI, n=13), twice a week for 12 weeks. Preand post-test of one repetition maximum, functional strength (Chair-test), peak torque for unilateral knee extension exercise and pain (Visual Analogue Scale) were evaluated.

RESULTS:

No statistically significant differences were observed between treatments in pain reduction (p>0.05). Both interventions increased muscle strength and functional strength after 12 weeks of intervention (p<0.05). The peak torque for knee joint extension increased only in the LI+BFR group (p<0.05). Has no difference in reducing pain in patients with KOA among the groups (p< 0.05), both in the LI+BFR and the LI group.

CONCLUSION:

The results of the present study showed that BFR associated with low-intensity resistance exercise does not produce additional effects in terms of pain reduction and strength gain in patients with knee osteoarthritis, when compared to resistance exercise alone.

Keywords
Chronic pain; Exercise therapy; Muscle strength; Pain Management

RESUMO

JUSTIFICATIVA E OBJETIVOS:

O exercício físico é uma estratégia não farmacológica eficiente para o tratamento da osteoartrite de joelho (OAJ). A restrição do fluxo sanguíneo (RFS) é uma técnica conhecida por potencializar o ganho de força e hipertrofia quando combinada com exercícios de resistência de baixa intensidade. Este estudo teve como objetivo analisar os efeitos de 12 semanas de treinamento de resistência de baixa intensidade com e sem restrição de fluxo sanguíneo (RFS) no controle da dor e melhora da força em pacientes com OAJ.

MÉTODOS:

Dois grupos de intervenção realizaram exercício resistido de baixa intensidade (extensão da articulação do joelho na cadeira extensora a 30% de uma repetição máxima) com (ER+RFS, n=13) ou sem restrição do fluxo sanguíneo (ER, n=13), duas vezes por semana durante 12 semanas. Foram avaliados pré e pós-teste de uma repetição máxima, força funcional (Chair-test), pico de torque para exercício de extensão de joelho unilateral e dor (Escala Analógica Visual).

RESULTADOS:

Não foram observadas diferenças estatisticamente significativas entre os tratamentos na redução da dor (p>0,05). Ambas as intervenções aumentaram a força muscular e a força funcional após 12 semanas de intervenção (p<0,05). O pico de torque para extensão da articulação do joelho aumentou apenas no grupo ER+RFS (p<0,05). A dor crônica relacionada à OAJ não apresentou diferença estatisticamente significativa na redução da dor (p> 0,05) em resposta a ambas as intervenções.

CONCLUSÃO:

Os resultados do presente estudo evidenciaram que a RFS associada ao exercício de resistência de baixa intensidade não prouduz efeitos adicinais na redução da dor e no ganho de força em pacientes com osteoartrite de joelho, quando comparada apenas ao exercício de resistência.

Descritores
Dor crônica; Força muscular; Manejo da dor; Terapia por exercício

HIGHLIGHTS

  • There is no difference in pain improvement whether the exercise is performed with or without blood flow restriction.

  • A single exercise can be used as an option to the early phases of rehabilitation.

  • Low-intensity resistance exercise with or without blood flow restriction, can be applied as an alternative in cases of knee osteoarthritis.

HIGHLIGHTS

  • There is no difference in pain improvement whether the exercise is performed with or without blood flow restriction.

  • A single exercise can be used as an option to the early phases of rehabilitation.

  • Low-intensity resistance exercise with or without blood flow restriction, can be applied as an alternative in cases of knee osteoarthritis.

INTRODUCTION

Osteoarthritis (OA) is a painful condition that affects the joints, leading to an inflammatory condition that, over time, results in joint stiffness, compromising the performance of activities of daily living or sports because of the painful condition in 80% of patients11 Incze MA. I have arthritis of the knees: what should i do? JAMA Intern Med. 2019;179(5):736.. In about 25% of cases, these limitations are associated with worsening quality of life, especially in relation to pain and the psychological dimension22 Fransen M, McConnell S, Harmer AR, Van der Esch M, Simic M, Bennell KL. Exercise for osteoarthritis of the knee: a Cochrane systematic review. Br J Sports Med. 2015;49(24):1554-7..

The major risk factors are advanced age, previous knee injury, obesity, female gender, family history of the disease, and occupational demand. In the United States, more than 22.7 million people have symptoms of OA, with concomitant impairment in the level of physical activity practice33 Mandl LA. Osteoarthritis year in review 2018: clinical. Osteoarthritis Cartilage. 2019;27(3):359-64.. In Brazil, according to Brazilian Society of Rheumatology (Sociedade Brasileira de Reumatologia)44 Brazilian Society of Rheumatology. Osteoartrite (Artrose). 2011; Available at: https://www.reumatologia.org.br/doencas/principais-doencas/osteoartrite-artrose/ Acessed sep-tember 9, 2021.
https://www.reumatologia.org.br/doencas/...
, OA is the most common rheumatologic disease, especially knee osteoarthritis (KOA).

Pain is a condition that compromises the practice of physical activities in patients with OA, enhancing the reduction of muscle strength. This condition, in a cyclical way, potentiates the loss of strength and pain55 Jorge RT, Souza MC, Jones A, Lombardi Júniore I, Jennings F, Natour J. Progressive resistance training in chronic musculoskeletal disorders. Braz J Reumatol. 2009;49(6):726-34.. In KOA, non-drug treatment includes weight loss and low-impact exercises such as cycling, rowing, swimming, walking, strength training, and Tai-Chi-Chuan, which have positive effects in reducing pain and improving functionality11 Incze MA. I have arthritis of the knees: what should i do? JAMA Intern Med. 2019;179(5):736.. Moderate to high intensity resistance training is among the main interventions indicated to improve conditions that may be associated with chronic pain in patients with KOA, such as muscle weakness66 Takagi S, Omori G, Koga H, Endo K, Koga Y, Nawata A, Endo N. Quadriceps muscle weakness is related to increased risk of radiographic knee OA but not its progression in both women and men: the Matsudai Knee Osteoarthritis Survey. Knee Surg Sports Traumatol Ar-throsc. 2018;26(9):2607-14.. A study77 Harper SA, Roberts LM, Layne AS, Jaeger BC, Gardner AK, Sibille KT, Wu SS, Vincent KR, Fillingim RB, Manini TM, Buford TW. Blood-flow restriction resistance exercise for older adults with knee osteoarthritis: a pilot randomized clinical trial. J Clin Med. 2019;8(2):265. provided evidence that strengthening the knee extensor muscles plays an important role, both in the prevention and in the treatment of KOA.

Interventions based on resistance exercises focused on increasing muscle strength are associated with important improvements in quality of life, especially in more vulnerable population groups, such as the elderly and patients with chronic pain88 Fusco O, Ferrini A, Santoro M, Lo Monaco MR, Gambassi G, Cesari M. Physical function and perceived quality of life in older persons. Aging Clin Exp Res. 2012;24(1):68-73.,99 Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP; American College of Sports Medicine. American College of Sports Medicine posi-tion stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc. 2011;43(7):1334-59.. Considering that high-intensity resistance exercise is more effective for reduction of pain and improvement of strength and functionality in patients with KOA and that this type of exercise (high-intensity) is not always well tolerated, lower-intensity exercise alternatives should be explored with a view to greater adherence to intervention protocols1010 Pitsillides A, Stasinopoulos D, Mamais I. Blood flow restriction training in patients with knee osteoarthritis: systematic review of randomized controlled trials. J Bodyw Mov Ther. 2021;27:477-86.. Therefore, blood flow restriction (BFR) techniques associated with low-intensity exercise have potential as a non-pharmacological intervention in the treatment of pain in patients with KOA1010 Pitsillides A, Stasinopoulos D, Mamais I. Blood flow restriction training in patients with knee osteoarthritis: systematic review of randomized controlled trials. J Bodyw Mov Ther. 2021;27:477-86..

In addition, interest in the technique of blood flow restriction associated with low-intensity exercise is growing, due to its effects on the musculature are comparable to high-intensity exercise and the potential to generate less pain and discomfort during exercise in patients with KOA1010 Pitsillides A, Stasinopoulos D, Mamais I. Blood flow restriction training in patients with knee osteoarthritis: systematic review of randomized controlled trials. J Bodyw Mov Ther. 2021;27:477-86.,1111 Ferraz RB, Gualano B, Rodrigues R, Kurimori CO, Fuller R, Lima FR, DE Sá-Pinto AL, Ros-chel H. Benefits of resistance training with blood flow restriction in knee osteoarthritis. Med Sci Sports Exerc. 2018;50(5):897-905.. Therefore, the present study aimed to analyze the effects of low-intensity resistance training with and without blood flow restriction for pain management and improvement of strength and functional capacity in patients with KOA.

The hypothesis of this study was that blood flow restriction associated with low-intensity exercise (knee extension on the extension chair) would be more effective than low-intensity exercise alone in reducing pain intensity, increasing muscle strength, and functional strength in patients with KOA.

METHODS

The present study was characterized as a randomized clinical trial, followed the protocol registered at ensaiosclinicos.gov.br and was reported according to Consolidated Standards of Reporting Trails (CONSORT)1212 Schulz KF, Altman DG, Moher D, CONSORT Group. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMC Med. 2010;8:18. https://doi.org/10.1186/1741-7015-8-18.
https://doi.org/10.1186/1741-7015-8-18...
.

Study design

As shown in figure 1, 35 subjects with a clinical diagnosis of KOA of both genres, aged 45 to 70 years were recruited. Twenty-six men (n=10) and women (n=16) met the eligibility criteria, underwent the pretest, and were randomly assigned to two experimental groups: low-intensity resistance exercise with blood flow restriction (LI+BFR: n=13), and low-intensity resistance exercise without blood flow restriction (LI: n=13). All subjects, regardless of the protocol, performed two sessions per week for 12 weeks and were reassessed (post-test).

Figure 1
Study design.

Participants

The sample of the present study consisted of 26 participants distributed in the two intervention groups. To calculate the sample size, an online calculator was used (http://hedwig.mgh.harvard.edu/sample_size/). The sample size was estimated considering a statistical power of 0.85; significance level of 0.05 (two-tailed), mean standard deviation of the main outcome variable (pain) of two units1313 Aguiar GC, Do Nascimento MR, De Miranda AS, Rocha NP, Teixeira AL, Scalzo PL. Effects of an exercise therapy protocol on inflammatory markers, perception of pain, and physical per-formance in individuals with knee osteoarthritis. Rheumatol Int. 2015;35(3):525-31. and a minimum detectable difference between the treatment of 2.5 units. Considering a sample loss of 10%, the sample in the present study consisted of 26 participants (LI+BFR = 13 and LI = 13).

Eligibility

This study included men and women aged between 45 and 70 years, with a diagnosis of KOA (assessed by a specialized physician), with no clinical restrictions for performing exercises, recruited in a Basic Health Unit (Unidade Básica de Saúde - UBS). For the classification of osteoarthritis, the criteria established by the American College of Rheumatology1414 Hochberg MC, Altman RD, April KT, Benkhalti M, Guyatt G, McGowan J, Towheed T, Welch V, Wells G, Tugwell P. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care Res (Hoboken). 2012;64(4):465-74. were used. Patients who underwent a recent surgical procedure (last three months), which compromised their participation in the study, with a diagnosis of vascular problems, and those who had functional limitations to perform the exercise proposed in the intervention protocols were excluded from the sample.

Randomization

The entire randomization process was designed and carried out by an administrative technician who was not part of the research team. Participants were randomly assigned to one of two intervention groups, with opaque sealed envelopes containing the description of the interventions inside.

Interventions

Low-intensity resistance exercise with blood flow restriction (LI+BFR)

The protocol consisted of performing two weekly sessions of bilateral knee joint extension exercise on the extension chair (TRG Fitness™, Blumenau-SC, Brazil), for 12 weeks. In the first two sessions, one set of 15 repetitions was performed, followed by two sets of 15 repetitions in the two subsequent sessions and three sets of 15 repetitions until the end of the 12 weeks of intervention. All participants performed the number of sets and repetitions prescribed in the intervention protocols. The progression of the number of sets and repetitions was chosen based on clinical practice to minimize pain during the physical exercise adaptation phase and improve adherence to the intervention protocol. The load used was equivalent to 30% of a maximum repetition (1-RM), assessed in the pretest and at the beginning of the 3rd, 5th, 8th, and 10th weeks of intervention.

The exercise execution speed was three seconds for each repetition (1.5 seconds for the concentric phase and 1.5 seconds for the eccentric phase) monitored by a digital metronome (Sanny Personal Counter™, São Bernardo do Campo-SP, Brazil) and the recovery interval between sets in all phases of the intervention protocol was one minute. To restrict blood flow, pneumatic tourniquets 7.5 x 90 cm (Clinic Leg WCS, Tecnologia/Cardiomed™, Curitiba-PR, Brazil) were attached to the proximal portion of both thighs at a height equivalent to the gluteal line. The pressure used in the tourniquets corresponded to 70% of the posterior tibial artery occlusion pressure measured by Portable Vascular Doppler (MEDPEJ™ DV-2001, Ribeirão Preto-SP, Brazil) with the subject in the standing position. The Visual Analog Scale (VAS) was used for pain monitoring, before, during, and immediately after each training session.

Low-intensity resistance exercise (LI)

The same strength exercise was used as indicated in the low intensity protocol, but without the use of pneumatic tourniquets.

Outcome measures

Primary outcome

The evaluation of maximum dynamic of muscle strength in knee extension exercise (TRG Fitness™, Blumenau, Santa Catarina, Brazil) followed the recommendations of the American Society of Exercise Physiologists.1414 Hochberg MC, Altman RD, April KT, Benkhalti M, Guyatt G, McGowan J, Towheed T, Welch V, Wells G, Tugwell P. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care Res (Hoboken). 2012;64(4):465-74. The exercise consisted of the full extension of the knee joint (180º), starting from the initial position (90º), and returning to the initial position. To assess pain intensity, the VAS, as proposed by a study1515 Martinez JE, Grassi DC, Marques LG. Analysis of the applicability of different pain question-naires in three hospital settings: outpatient clinic, ward and emergency unit. Rev Bras Reuma-tol. 2011;51(4):299-308., was used in preand post-test and immediately after each training session. The instrument consisted of a scale with a score ranging from zero (no pain) to 10 (worst pain possible).

Secondary outcomes

The evaluation of the mean peak torque for unilateral knee joint extension1616 Martins W, Oliveira R, Silva M, et al. Assessment of knee extension strength in older adults: re-liability of an isokinetic testing protocol. Rev Bras Ativ Física Saúde. 2015;20(4):435-435.,1717 Siqueira CM, Pelegrini FRMM, Fontana MF, Greve JMD. Isokinetic dynamometry of knee flexors and extensors: comparative study among non-athletes, jumper athletes and runner athle-tes. Rev Hosp Clin Fac Med São Paulo. 2002;57(1):19-24. was performed using an isokinetic dynamometer (Biodex System 4 Pro™, Biodex Medical Systems INC., Shirley, NY, USA). The quadriceps strength of both legs was evaluated, although for the present study only the peak torque of the limb with OA was considered. Briefly, one minute after the end of the warm-up (cycle ergometer for five minutes), the participants performed six maximum concentric extensions on each limb at a speed of 60º/s. Peak torque is defined as the highest output force exerted at any time during a repetition. To assess the functional strength of the lower limbs, the chair test was used, which consists of getting up from a chair without an armrest, performing a full extension of the knee and hip joints, maintaining the torso upright and returning to the starting position as often as possible within 30 seconds1818 Rikli RE, Jones C J. Senior fitness test manual. Champaign, IL: Human kinetics Publishers; 2013..

Data collection and blinding

All participants selected for the study attended the physical therapy clinic one week before the start of data collection, to familiarize themselves with the data collection procedures that were used in the preand post-test. In the following week, on previously established days and times, each subject attended the clinic to assess anthropometric parameters (body mass and height) and assess functional strength and maximum dynamic strength. The isokinetic evaluation was performed as previously scheduled at the physiotherapy clinic. In the week following the pretest, 12 weeks of intervention were started, followed by post-test evaluations.

The intervention protocols were performed at different times, so that subjects from different groups did not use the intervention site at the same time. To minimize the risk of bias, additional measures were taken. All data collection procedures were performed by professionals who were blinded to the treatments.

Ethical procedures

All procedures, objectives, risks, and benefits of the study were explained to the volunteers, who signed the Free and Informed Consent Term (FICT), consenting to their participation in the research. This study was approved by the Ethics Committee for Research Involving Human Beings (Comitê de Ética em Pesquisa Envolvendo Seres Humanos - Protocol 3.061.166) and registered in the Brazilian Registry of Clinical Trials (Registro Brasileiro de Ensaios Clínicos - ReBEC).

Statistical analysis

Shapiro-wilk, Levene, and Mauchly tests were used to analyze the distribution and data characteristics (normality, homoscedasticity, and sphericity, respectively). Logarithmic adjustments and Greenhouse-Geisser correction were made when the distribution did not meet the normality assumptions of the data distribution. A two-way analysis of variance (ANOVA 2x2) was used for comparisons between time (preand post-intervention) and between groups (LI+BFR and LI) and for the evaluation of the “time x group” interaction, followed by Bonferroni multiple comparison test. For all analyzes, the Statistical Package for Social Sciences (SPSS™) version 24.0 was used, and the significance level adopted for all analyzes was 5%.

The effect sizes were calculated for the outcome variables as suggested by an author1919 Cohen J. Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Taylor and Francis; 2013. Available at: https://www.perlego.com/book/1616435/statistical-power-analysis-for-the-behavioral-sciences-pdf.
https://www.perlego.com/book/1616435/sta...
. Effect sizes were classified as very small (< 0.19), small (0.20 to 0.49), medium (0.50 to 0.79), large (0.80 to 1.19), very large (1.20 - 1.99), and huge (> 2.0)2020 Sawilowsky SS. New effect size rules of thumb. J Mod Appl Stat Methods. 2009;8(2):26. The calculation of confidence intervals for effect sizes was performed as proposed by a study2121 Berben L, Sereika SM, Engberg S. Effect size estimation: methods and examples. Int J Nurs Stud. 2012;49(8):1039-47..

RESULTS

Figure 1 shows the flow diagram of the study. Of 35 individuals invited to participate in the study, seven did not meet inclusion criteria and two had another reason for exclusion. Of the 26 remaining individuals, 26 were randomized to the exercise program with and without blood flow restriction groups. The final analysis included all randomized individuals (13 in the low-intensity resistance exercise with blood flow restriction LI+BFR and 13 low-intensity resistance exercise LI).

Table 1 presents the sociodemographic and clinical characteristics of the participants (pre-test).

Table 1
Characterization of study participants.

The analysis of data related to the effects of interventions on chronic pain is presented in table 2. There were no statistically significant differences (p>0.05) between treatments in pain reduction. In both protocols, the effect size was evaluated as large (LI+BFR: ES = -2.44; LI: ES = -2.04). The analysis of pain data showed that both protocols (LI+BFR and LI) significantly reduced pain from pre to post-test (p<0.05).

Table 2
Effects of low-intensity resistance exercise with blood flow restriction (LI+BFR) and low-intensity resistance exercise (LI) on pain in patients with knee osteoarthritis.

Data relating to strength for 1-RM, functional strength (chair-test) and peak torque are shown in Figure 2. No statistically significant difference (p>0.05) between treatments was found for the variables strength for 1-RM and functional strength. Both the strength for 1-RM and the functional strength increased significantly (p < 0.05) from preto post-test in both intervention protocols (LI+BFR and LI). Peak torque, expressed as a function of body mass, showed a significant increase from preto post-test only in the LI+BFR group (p < 0.05). No statistically significant differences between groups (p ≥ 0.05) were found, both preand post-test for the variables, strength for 1-RM, functional strength, and peak torque (Figure 2).

Figure 2
Effects of 12 weeks of strength exercise (knee joint extension on extensor chair) on maximal dynamic strength (1-RM) and functional strength (chair-test) in patients with knee osteoarthritis (KOA)

Effect sizes related to interventions (Figure 2) were evaluated as large and very large for functional strength (LI+BFR: ES = 1.10; LI: ES = 1.57, respectively), large for strength for 1-RM (LI+BFR: ES = 1.00, LI: ES = 1.12), and small for the peak torque (LI+BFR: ES = 0.33, LI: ES = 0.24). It should be noted that the magnitude of effect of the interventions was quite similar between treatments for the variable’s strength for 1-RM, functional strength (chair-test) and peak torque.

DISCUSSION

The main finding of this study was the fact that blood flow restriction added to resistance exercise does not produce additional effects on strength gain and pain reduction in patients with KOA. The magnitudes of the effects of the analyzed outcomes were similar between interventions. Although no differences were demonstrated between the interventions in the analyzed outcomes, both analyzed protocols increased muscle strength for 1-RM, functional strength and reduced pain in patients with KOA.

In KOA, muscle strength is usually reduced and accompanied by pain. For this reason, the American College of Rheumatology recommends muscle strengthening as the first therapeutic strategy for the treatment of this condition1414 Hochberg MC, Altman RD, April KT, Benkhalti M, Guyatt G, McGowan J, Towheed T, Welch V, Wells G, Tugwell P. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care Res (Hoboken). 2012;64(4):465-74.. The strengthening of the femoral quadriceps is commonly indicated in the treatment of KOA, considering that this condition has a static and dynamic chondroprotective effect on the knee joint.

In the present study, both interventions were effective to improve strength and reduce pain in patients with KOA. Low-intensity exercise may have been a factor that contributed to the high adherence of participants, with a consequent improvement in the evaluated outcomes2222 Loenneke J, Fahs CA, Rossow LM, Abe T, Bemben MG. The anabolic benefits of venous blood flow restriction training may be induced by muscle cell swelling. Med Hypotheses. 2012;78(1):151-4.. Another aspect that can be considered to explain the results of this study was suggested by a study2323 Messier SP, Mihalko SL, Beavers DP. Effect of high-intensity strength training on knee pain and knee joint compressive forces among adults with knee osteoarthritis: the start randomized clinical trial. JAMA. 2021;325(7):646-57., who reported that the effects of interventions for KOA may be mainly related to the placebo effect, natural history of the disease, and the long duration of intervention that may increase the placebo response to subjective findings such as pain.

To some extent, data from the present study on the potential effects of low-intensity physical exercise, with or without blood flow restriction, on pain reduction may be associated with increased strength and muscle hypertrophy, as proposed by a study2424 Lorenz DS, Bailey L, Wilk KE, Mangine RE, Head P, Grindstaff TL, Morrison S. Blood flow restriction training. J Athl Train. 2021;56(9):937-44., who also observed that ischemic conditions potentiate the signaling network that increases the gene expression of substances involved in the preservation of the nervous system and neuronal apoptosis in patients with orthopedic injuries.

Although a study2424 Lorenz DS, Bailey L, Wilk KE, Mangine RE, Head P, Grindstaff TL, Morrison S. Blood flow restriction training. J Athl Train. 2021;56(9):937-44. have shown that exercise with blood flow restriction potentiates gains in strength and muscle mass, the same study2424 Lorenz DS, Bailey L, Wilk KE, Mangine RE, Head P, Grindstaff TL, Morrison S. Blood flow restriction training. J Athl Train. 2021;56(9):937-44. strongly advocate the inclusion of BFR to gain strength and muscle mass in the early stages of rehabilitation, when high-intensity exercises would not be tolerated by patients, and another study55 Jorge RT, Souza MC, Jones A, Lombardi Júniore I, Jennings F, Natour J. Progressive resistance training in chronic musculoskeletal disorders. Braz J Reumatol. 2009;49(6):726-34. demonstrated that high-intensity exercises do not reduce more knee pain and knee joint compression forces than low-intensity exercises, in the present study, BFR was not efficient to promote additional increases in dynamic strength or functional strength, which is why pain improvement was similar between the experimental protocols used.

Other studies on KOA patients have also shown that exercise with BFR was effective in promoting strength gain and pain improvement77 Harper SA, Roberts LM, Layne AS, Jaeger BC, Gardner AK, Sibille KT, Wu SS, Vincent KR, Fillingim RB, Manini TM, Buford TW. Blood-flow restriction resistance exercise for older adults with knee osteoarthritis: a pilot randomized clinical trial. J Clin Med. 2019;8(2):265.,88 Fusco O, Ferrini A, Santoro M, Lo Monaco MR, Gambassi G, Cesari M. Physical function and perceived quality of life in older persons. Aging Clin Exp Res. 2012;24(1):68-73.,1111 Ferraz RB, Gualano B, Rodrigues R, Kurimori CO, Fuller R, Lima FR, DE Sá-Pinto AL, Ros-chel H. Benefits of resistance training with blood flow restriction in knee osteoarthritis. Med Sci Sports Exerc. 2018;50(5):897-905.,1414 Hochberg MC, Altman RD, April KT, Benkhalti M, Guyatt G, McGowan J, Towheed T, Welch V, Wells G, Tugwell P. American College of Rheumatology 2012 recommendations for the use of nonpharmacologic and pharmacologic therapies in osteoarthritis of the hand, hip, and knee. Arthritis Care Res (Hoboken). 2012;64(4):465-74.. However, in these studies, the authors used different protocols such as isometric contraction of the abdomen, hip abduction, sensorimotor training, and knee extension in the extension chair associated with leg press exercise. None of the protocols studied in the literature showed similar characteristics to the present study. A study1111 Ferraz RB, Gualano B, Rodrigues R, Kurimori CO, Fuller R, Lima FR, DE Sá-Pinto AL, Ros-chel H. Benefits of resistance training with blood flow restriction in knee osteoarthritis. Med Sci Sports Exerc. 2018;50(5):897-905., was the closest methodologically closer to the present study, however, the protocol used in that study included two exercises (bilateral leg press and knee extension exercise) and was performed in a hospital environment.

Unlike the study1111 Ferraz RB, Gualano B, Rodrigues R, Kurimori CO, Fuller R, Lima FR, DE Sá-Pinto AL, Ros-chel H. Benefits of resistance training with blood flow restriction in knee osteoarthritis. Med Sci Sports Exerc. 2018;50(5):897-905.,2626 Bryk FF, Dos Reis AC, Fingerhut D. Exercises with partial vascular occlusion in patients with knee osteoarthritis: a randomized clinical trial. Knee Surg Sports Traumatol Arthrosc. 2016;24(5):1580-6. who did not find increases in muscle strength associated with low intensity exercise despite performing a protocol with two exercises over 12 weeks, the present study demonstrated that only one knee extension exercise was sufficient to increase muscle strength in response to the same training period. Although the results of this present study are encouraging, they need to be interpreted with carefully. More important than the increase in muscle mass for the patient with KOA is the increase in strength, especially in the initial phase of the intervention, and different muscle components of sarcopenia and therapeutic interventions to increase muscle strength have important impacts on reducing pain and improving performance in activities of daily living, with consequent improvement in quality of life2727 Trombetti A, Reid KF, Hars M, Herrmann FR, Pasha E, Phillips EM, Fielding RA. Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int. 2016;27(2):463-71..

Pain associated with physical dysfunction is one of the main factors that compromise the daily activities of people with KOA77 Harper SA, Roberts LM, Layne AS, Jaeger BC, Gardner AK, Sibille KT, Wu SS, Vincent KR, Fillingim RB, Manini TM, Buford TW. Blood-flow restriction resistance exercise for older adults with knee osteoarthritis: a pilot randomized clinical trial. J Clin Med. 2019;8(2):265.,2727 Trombetti A, Reid KF, Hars M, Herrmann FR, Pasha E, Phillips EM, Fielding RA. Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int. 2016;27(2):463-71.

28 Lixandrao ME, Ugrinowitsch C, Berton R. Magnitude of muscle strength and mass adaptations between high-load resistance training versus low-load resistance training associated with blood-flow restriction: a systematic review and meta-analysis. Sports Med. 2018;48(2):361-78.

29 Hughes L, Patterson SD. The effect of blood flow restriction exercise on exercise-induced hypo-algesia and endogenous opioid and endocannabinoid mechanisms of pain modulation. J App Physiol. 2020;128(4):914-24.
-3030 Creamer P, Lethbridge-Cejku M, Hochberg MC. Factors associated with functional impair-ment in symptomatic knee osteoarthritis. Rheumatology. 2000;39(5):490-6.. A systematic review with meta-analysis3131 Rocha TC, Ramos PDS, Dias AG, Martins EA. The effects of physical exercise on pain mana-gement in patients with knee osteoarthritis: a systematic review with metanalysis. Rev Bras Or-top. 2020;55(5):509-17., showed that quadriceps strengthening improves pain in patients with KOA, although there is no consensus on the most appropriate protocol to be used, especially in relation to exercise dosages3030 Creamer P, Lethbridge-Cejku M, Hochberg MC. Factors associated with functional impair-ment in symptomatic knee osteoarthritis. Rheumatology. 2000;39(5):490-6.,3131 Rocha TC, Ramos PDS, Dias AG, Martins EA. The effects of physical exercise on pain mana-gement in patients with knee osteoarthritis: a systematic review with metanalysis. Rev Bras Or-top. 2020;55(5):509-17.. The results of the present study point to the importance of muscle strengthening, especially of the quadriceps, in the treatment of pain in patients with KOA. Despite being a study with limitations, the results of this study represent a positive perspective for future analyzes on this protocol for subjects with knee osteoarthritis.

In this research, the gain in strength, regardless of the intervention, occurred concomitantly with the improvement in muscle function and with the reduction in pain. Thus, this research hypothesized that these associated factors may also result in an increase in self-confidence to perform activities of daily living (not assessed), alleviating fear and the expectation of pain2727 Trombetti A, Reid KF, Hars M, Herrmann FR, Pasha E, Phillips EM, Fielding RA. Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int. 2016;27(2):463-71.,3232 Dor A, Kalichman L. A myofascial component of pain in knee osteoarthritis. J Bodyw Mov Ther. 2017;21(3):642-7.,3333 Bushnell MC, Čeko M, Low LA. Cognitive and emotional control of pain and its disruption in chronic pain. Nat Rev Neurosci. 2013;14(7):502-11.. It should be noted that the main advantage attributed at the blood flow restriction (BFR) is to be an effective clinical intervention used to increase strength in healthy individuals. However, its effects on pain and function in individuals with knee pain are unknown3434 Cuyul-Vásquez I, Leiva-Sepúlveda A, Catalán-Medalla O, Araya-Quintanilla F, Gutiérrez-Espinoza H. The addition of blood flow restriction to resistance exercise in individuals with knee pain: a systematic review and meta-analysis. Braz J Phys Ther. 2020;24(6):465-78.. In this study, blood flow restriction did not produce additional effects regarding the parameters used when compared to exercise without blood flow restriction. The findings of this study showed that in the initial phase of an intervention (first 12 weeks), a single low-intensity resistance exercise twice a week is sufficient to significantly reduce pain in a patient with KOA and that blood flow restriction it was not a condition that potentiated this effect.

Improvements in peak torque in isokinetic knee extension exercise (LI+BFR) were consistent with other studies in which strength gain was similar between low-intensity exercise protocols with BFR1111 Ferraz RB, Gualano B, Rodrigues R, Kurimori CO, Fuller R, Lima FR, DE Sá-Pinto AL, Ros-chel H. Benefits of resistance training with blood flow restriction in knee osteoarthritis. Med Sci Sports Exerc. 2018;50(5):897-905.,2626 Bryk FF, Dos Reis AC, Fingerhut D. Exercises with partial vascular occlusion in patients with knee osteoarthritis: a randomized clinical trial. Knee Surg Sports Traumatol Arthrosc. 2016;24(5):1580-6.,3434 Cuyul-Vásquez I, Leiva-Sepúlveda A, Catalán-Medalla O, Araya-Quintanilla F, Gutiérrez-Espinoza H. The addition of blood flow restriction to resistance exercise in individuals with knee pain: a systematic review and meta-analysis. Braz J Phys Ther. 2020;24(6):465-78.,3535 Behringer M, Heinke L, Leyendecker J, Mester J. Effects of blood flow restriction during mo-derate-intensity eccentric knee extensions. J Physiol Sci. 2018;68(5):589-99., reinforcing the hypothesis that pain improvement can be attributed to strength gain. The data from this study corroborate the findings by a research77 Harper SA, Roberts LM, Layne AS, Jaeger BC, Gardner AK, Sibille KT, Wu SS, Vincent KR, Fillingim RB, Manini TM, Buford TW. Blood-flow restriction resistance exercise for older adults with knee osteoarthritis: a pilot randomized clinical trial. J Clin Med. 2019;8(2):265., which also showed improvements in peak torque from preto post-test for the LI+BFR group. It should also be noted that increases in functional strength are associated with the improved performance of activities of daily living, and this factor can be contributed indirectly to reducing pain in knee OA2727 Trombetti A, Reid KF, Hars M, Herrmann FR, Pasha E, Phillips EM, Fielding RA. Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int. 2016;27(2):463-71.. Regarding the frequency of sessions3636 Shiromaru FF, De Salles Painelli V, Silva-Batista C. Differential muscle hypertrophy and edema responses between high-load and low-load exercise with blood flow restriction. Scand J Med Sci Sports. 2019;29(11):1713-26., was demonstrated that a high frequency of low-intensity training associated with BFR over a period of three weeks can produce significant increases in the cross-sectional area of all quadriceps muscles without edema-induced muscle swelling. A study suggested that low intensity, short duration, and high-frequency BFR may be a better training approach than high intensity to achieve hypertrophy without noticeable influence of muscle edema3636 Shiromaru FF, De Salles Painelli V, Silva-Batista C. Differential muscle hypertrophy and edema responses between high-load and low-load exercise with blood flow restriction. Scand J Med Sci Sports. 2019;29(11):1713-26.. This hypothesis corroborates the findings of the present study, which in the short term, reported significant improvement in pain only with low-intensity exercise, regardless of blood flow restriction.

One limitation of the present study was the low sample size. A second limitation was the absence of a high-intensity resistance exercise and a control exercise group as well as missing to include an evaluation of biomarkers that allow identification of the mechanisms involved in response to BFR exercise. However, to date, few studies have demonstrated new alternatives for KOA patients77 Harper SA, Roberts LM, Layne AS, Jaeger BC, Gardner AK, Sibille KT, Wu SS, Vincent KR, Fillingim RB, Manini TM, Buford TW. Blood-flow restriction resistance exercise for older adults with knee osteoarthritis: a pilot randomized clinical trial. J Clin Med. 2019;8(2):265.,2424 Lorenz DS, Bailey L, Wilk KE, Mangine RE, Head P, Grindstaff TL, Morrison S. Blood flow restriction training. J Athl Train. 2021;56(9):937-44.,2727 Trombetti A, Reid KF, Hars M, Herrmann FR, Pasha E, Phillips EM, Fielding RA. Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int. 2016;27(2):463-71.. In this sense, the protocols analyzed in this study are a possible effective alternative to increase maximum dynamic strength, functional strength, and reduce pain, especially because they use a single exercise, easy to apply and perform, which facilitates treatment adherence. Clearly, further studies are needed to examine whether the present results are representative of the general population with KOA.

CONCLUSION

The results of this study showed that blood flow restriction associated with low-intensity resistance exercise does not produce additional effects on muscle strength gain and pain reduction in patients with knee osteoarthritis, compared to strength exercise alone. In this sense, the hypothesis of the study was rejected.

  • Sponsoring sources: this study was financed in part by the Coordination for the Improvement of Higher Education Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil - CAPES) - Finance Code 001.

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Publication Dates

  • Publication in this collection
    16 June 2023
  • Date of issue
    Jan-Mar 2023

History

  • Received
    25 Jan 2023
  • Accepted
    27 Mar 2023
Sociedade Brasileira para o Estudo da Dor Av. Conselheiro Rodrigues Alves, 937 Cj2 - Vila Mariana, CEP: 04014-012, São Paulo, SP - Brasil, Telefones: , (55) 11 5904-2881/3959 - São Paulo - SP - Brazil
E-mail: dor@dor.org.br