INFLUENCE OF BLOOD FLOW RESTRICTION DURING LOW-INTENSITY RESISTANCE EXERCISE ON THE POSTEXERCISE HYPOTENSIVE RESPONSE ALEX S. MAIOR,1,2 ROBERTO SIMA˜O,2 MICHAEL S.R. MARTINS,1 BELMIRO F. JEFFREY M. WILLARDSON3
DE
SALLES,2
AND
1
University Augusto Motta (UNISUAM), Master Program in Rehabilitation Sciences, Rio de Janeiro, Brazil; 2Federal University of Rio de Janeiro, Physical Education Post-Graduation Program, Rio de Janeiro, Brazil; and 3Department of Kinesiology and Sports Studies, Eastern Illinois University, Charleston, Illinois ABSTRACT
Maior, AS, Sima˜o, R, Martins, MSR, Salles, BFd, and Willardson, JM. Influence of blood flow restriction during low-intensity resistance exercise on the postexercise hypotensive response. J Strength Cond Res 29(10): 2894–2899, 2015—Low-intensity resistance exercise (RE) combined with blood flow restriction (BFR) has been shown to promote similar increases in strength and hypertrophy as traditional high-intensity RE without BFR. However, the effect of BFR on the acute postexercise hypotensive response has received limited examination. Therefore, the purpose of this study was to compare high-intensity exercise (HIE) vs. low-intensity RE with BFR on the postexercise hypotensive response in normotensive young subjects. Fifteen men (age: 23.4 6 3.4 years) performed the following 2 experimental protocols in randomized order: (a) 3 sets of biceps curls (BCs) at 80% of 1 repetition maximum (RM) and 120-second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60-second rest between sets. Analysis of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was conducted for 60 minutes after both protocols. The values for SBP, DBP, and mean blood pressure (MBP) at baseline and postexercise were not significantly different between the HIE vs. the BFR protocol. However, within the BFR protocol, significant decreases (p # 0.05) in SBP occurred at 30 minutes (125.86 6 9.33 mm Hg) and 40 minutes (125.53 6 10.19 mm Hg) after exercise when compared with baseline (132.86 6 9.12 mm Hg) and significant decreases in DBP and MBP occurred at 20 minutes, 30 minutes, and 40 minutes after exercise vs. baseline (p # 0.05). Therefore, we conclude that exercises engaging a relatively small amount of muscle mass, such as the BC (or other similar single joint
Address correspondence to Alex S. Maior, [email protected]. 29(10)/2894–2899 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association
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exercises), might be performed at a lower intensity with BFR to promote a postexercise hypotensive response.
KEY WORDS hypotension, Kaatsu training, vascular occlusion, blood pressure
INTRODUCTION
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ardiovascular disease is associated with primary risk factors that can be controlled, treated, or modified, such as high blood pressure (BP). Physical inactivity is also known as a primary risk factor for cardiovascular disease, and people who are less active and less fit have a 30–50% greater risk for having high BP (19). However, meta-analytical data suggest that resistance exercise (RE) can decrease mean resting BP by as much as 3–4 mm Hg (3). Consequently, RE is prescribed for the control of resting BP in hypertensive and normotensive individuals (2,4,11,13). Resistance exercise involves multiple variables that can be arranged to specifically meet training goals and individual needs, such as exercise order, rest interval between sets, exercise mode, training frequency, movement velocity, training volume, repetitions per set, number of sets, type of muscle action, and the load intensity (4). Therefore, knowledge of cardiovascular responses during and after RE may facilitate better control of hemodynamic parameters and greater effectiveness of certain RE regimens. The magnitude and direction of BP and heart rate (HR) responses during RE are directly related to exertion level, number of repetitions and sets, rest interval between sets, and motor unit recruitment (4,10). Traditional dynamic RE protocols stimulate increases in HR and stroke volume. Concomitantly, greater venous return to heart is facilitated by greater breathing frequency, pumping action of skeletal muscles, and venoconstriction. Conversely, low-intensity RE (20–50% of 1 repetition maximum [1RM]) with the addition of blood flow restriction (BFR) promotes an increase in HR to maintain cardiac output, because of the decrease in stroke volume, which results from restricted blood flow, and consequently, reduces venous blood return (23). Thus, performing RE with
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Journal of Strength and Conditioning Research the addition of BFR stimulates compensatory adaptations to facilitate greater venous return, such as significant increases in vascular endothelial growth factor (VEGF) (23). A recent study (12) showed a significant decrease in carotid arterial compliance that was associated with elevations in systolic blood pressure (SBP) during exercise sessions that consisted of a high-intensity exercise (HIE) (75% of a 1RM) load vs. a low-intensity load with BFR (30% of a 1RM) over 6 weeks. Conversely, another study demonstrated that a postexercise hypotensive response did not occur after a low-intensity RE session with BFR (20% of 1RM), whereas the opposite was found for an HIE session (70% of 1RM) (18). Few studies have evaluated the association between the postexercise hypotensive response and low-intensity RE combined with BFR. Low-intensity RE with BFR might promote greater shear stress against blood vessel walls on restoration of blood flow that occurs with release of occlusive pressure, which may stimulate greater nitric oxide production to promote vasodilation, and a hypotensive response postexercise (6). The RE load intensity can affect the duration but not the magnitude of the postexercise hypotensive response (3,4,8). The magnitude of the postexercise hypotensive response may, to some extent, depend on an individual’s health status. The identification of specific BP responses that might be associated with manipulation of training variables is important to ensure the optimal, and appropriate, prescription of RE for individuals concerned with BP control, such as those with chronic hypertension. Thus, bearing in mind the importance of examining the postexercise hypotensive response to promote greater efficacy and safety during low-intensity RE with BFR, the purpose of this study was to compare an HIE session vs. low-intensity RE with BFR on the postexercise hypotensive response in normotensive young subjects.
METHODS Experimental Approach to the Problem
To compare an HIE protocol vs. a low-intensity RE protocol with BFR on the postexercise hypotensive response, subjects performed 2 RE sessions. After measurement of a 1RM load for the standing free-weight biceps curl (BC) in test and retest sessions, subjects performed 2 RE sessions in random order, which included the following: (a) 3 sets of BCs at 80% of 1RM and 120second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60-second rest between sets. Blood pressure was measured before and at 10minute intervals for 60 minutes after each RE session. Subjects
Fifteen healthy men (age: 23.4 6 3.4 years, body mass: 78.6 6 6.3 kg, height: 177.2 6 7.1 cm, BMI: 25 6 2.4 kg$m22) with at least 1 year of recreational RE experience were asked to participate in this study. All subjects were over 18 years old and completed the Physical Activity Readiness Questionnaire and signed an informed consent according to the Declaration of
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Helsinki. The experimental procedures were approved by the Ethics Committee of the Institution and were performed in accordance with the international ethical standards. The following additional exclusion criteria were adopted: (a) use of drugs that could affect cardiorespiratory responses, (b) bone-, joint-, or muscle-diagnosed problems that could limit the execution of BC, (c) systemic hypertension ($140/90 mm Hg or use of antihypertensive medication), (d) metabolic disease, (e) use of exogenous anabolic-androgenic steroids, drugs, or medication with potential effects on physical performance. Anthropometric and Hemodynamic Measurements
Volunteers attended the laboratory a total of 4 times with 48 hours between visits. During the first visit, anthropometric and hemodynamic data were collected, as well as a 1RM assessment for the standing free-weight BC. During the second visit, the 1RM assessment was repeated, and the RE sessions were performed during the third and fourth visits with or without BFR. All testing was performed between 1:00 PM and 3:00 PM. Subjects received a light lunch 2 hours before each laboratory visit. Coffee, tea, alcohol, and tobacco intake were prohibited for 48 hours, and subjects avoided formal and strenuous exercise for 48 hours before each visit. Body mass was measured to the nearest 0.1 kg using a calibrated physician’s beam scale (model 31; Filizola, Sa˜o Paulo, Brazil), with the men dressed in shorts. Height was determined without shoes to the nearest 0.1 cm using a stadiometer scale (model 31; Filizola) after a voluntary deep inspiration. Body fat percentage (%) was estimated using the 7-site skinfold method according to the guidelines of the American College of Sports Medicine (1). The mid upper arm muscle circumference was estimated by circumference of the bone and muscle portions of the upper arm. The triceps skinfold was measured to represent the thickness of the subcutaneous fat that surrounds the muscle. The following formula was used to estimate the muscle-bone cross-sectional area (1):
TSF Muscle-bone CSA ¼ ΜC2 p3 : 10 Before commencement of each RE session, subjects rested quietly in a supine position for 10 minutes before measurement of resting BP. After each RE session, BP was measured immediately postexercise and in 10-minute intervals for 60 minutes, resulting in a total of 7 readings after each RE session. Before and after each session, subjects were fitted with ambulatory BP monitoring equipment (PM50 Monitor; Contec Medical, Beijing, China), and this equipment was used for all preand postexercise BP measurements. The ambulatory BP equipment was autocalibrated before each use to ensure accuracy. Spurious readings, because of factors such as movement artifact, were automatically edited by the software. During BP pre- and postexercise monitoring, subjects remained in a supine position in a temperature-controlled quiet room (228 C). VOLUME 29 | NUMBER 10 | OCTOBER 2015 |
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Hypotensive and Blood Flow Restriction range of motion for the exercise (BC) had to be completed. The BC range of motion for a successful repetition was defined as follows: elbows beginning in full extension followed by full flexion, whereas maintaining perfect postural alignment with no torso sway. The 1RM test has been described previously and for reliability, the following strategies were adopted (10): (a) standardized instructions about the testing procedures were given to subjects before test; (b) subjects received standardized instructions concerning exercise technique; (c) verbal encouragement was provided during tests; and (d) the mass of all weights and bars was determined using a precision scale. Strength Training Sessions and Blood Flow Restriction
A standing free-weight BC with a straight bar was selected for use in this study because of its common use in RE programs and because it has been used in previous studies examining BFR (14,24). The 1RM tests were performed after the anthropometric measurements on the first day. After 48 hours, the 1RM test was repeated to determine test-retest reliability. The heaviest load achieved on either test day was considered the 1RM. The 1RM loads were determined in fewer than 5 attempts with a rest interval of 5 minutes between attempts (10). No pause was allowed between the concentric and eccentric phases of a repetition or between repetitions. For a repetition to be successful, a complete
The subjects performed a bilateral BC exercise with a straight bar in a standing position. The 2 strength training sessions were performed on nonconsecutive days and in random order, which included the following: (a) 3 sets of BCs at 80% of 1RM and 120-second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60second rest between sets. In BFR protocol, the proximal portion of both arms was compressed by a specially designed elastic belt (width 140 mm, length 200 mm). The belt contained a small pneumatic bag along its inner surface. To partially occlude muscle blood flow, the cuff was inflated to a pressure of 20 mm Hg below the acute SBP determined after 15 minutes of semirecumbent resting (14). The mean restrictive pressure throughout the period of training was 109.4 6 7.33 mm Hg. The BFR was maintained throughout the session of exercise, which lasted 251.1 6 22.3 seconds for the BFR protocol and 232.7 6 22.2 seconds for the HIE protocol. The partial occlusion of muscle blood flow was restored immediately after the RE session. The BFR protocol resulted in a total
Figure 2. Diastolic blood pressure (DBP) at rest, immediately postexercise, and at 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10– 60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
Figure 3. Mean blood pressure (MBP) at rest, immediately postexercise, and during 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10–60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
Figure 1. Mean systolic blood pressure (SBP) at rest, immediately postexercise, and at 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10–60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
One Repetition Maximum Test
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TABLE 1. Comparison of blood pressure (BP) effect size (ES) statistics traditional HIE protocol vs. BFR protocol.* 10 min Systolic blood pressure BFR HIE Diastolic blood pressure BFR HIE Mean blood pressure BFR HIE
20 min
30 min
40 min
50 min
60 min
20.063 Trivial 0.122 Trivial
0.374 Small 0.281 Trivial
0.741 Small 0.219 Trivial
0.777 Small 0.447 Small
0.593 Small 0.518 Small
0.699 Small 0.421 Small
0.485 Small 0.052 Trivial
0.832 Moderate 0.112 Trivial
0.725 Small 0.238 Trivial
0.684 Small 0.231 Trivial
0.577 Small 0.099 Trivial
0.291 Trivial 20.265 Trivial
0.025 Trivial 0.13 Trivial
0.573 Small 0.244 Trivial
0.727 Small 0.317 Trivial
0.706 Small 0.569 Small
0.507 Small 0.358 Small
0.363 Small 20.04 Trivial
*BFR = blood flow restriction protocol; HIE = high-intensity resistance exercise protocol.
of 47.1 6 9.5 repetitions and the HIE protocol in a total of 21.8 6 5.9 repetitions. During each RE session, subjects were verbally encouraged to perform all sets to concentric failure, using the consistent definition of a complete range of motion used for the 1RM test. No attempt was made to control repetition velocity. During all RE sessions, subjects were asked not to perform a Valsalva maneuver. All of the exercise sessions were preceded by a 10-minute warm-up on an upper body ergometer (Technogym, Italy) with an intensity of 20 W. Statistical Analyses
All data are presented as mean 6 SD. The statistical analysis was initially performed using the Shapiro-Wilk normality test and the homoscedasticity test (Bartlett criterion). To test the reproducibility of the 1RM load between the test and retest, we used the intraclass correlation coefficient (ICC). To compare potential differences in postexercise SBP, diastolic blood pressure (DBP), and mean blood pressure (MBP) in the BFR and HIE protocols, a repeatedmeasures 2-way analysis of variance (ANOVA) with Bonferroni post hoc tests was used. Comparisons withingroups for BP were performed with a 1-way repeatedmeasures ANOVA followed by Tukeys post hoc tests. The level of significance was set at p # 0.05 for all statistical comparisons. Additionally, to determine the magnitude of the findings, effect size (ES; the difference between pretest and posttest scores divided by the pretest SD) statistics were calculated for the SBP and DBP responses for each RE session, and the scale proposed by Rhea (17) was used to determine the magnitude of the ES. All statistical analyses were performed using GraphPad Prism 5.0 (GraphPad Software Inc., San Diego, CA, USA).
RESULTS The ICC for the BC was 0.92 (p , 0.001), Figures 1–3 summarize the acute hemodynamic responses for each protocol (BFR vs. HIE). The SBP values were not significantly different between protocols at baseline and postexercise at each time point (Figure 1). However, within the BFR protocol, a significant decrease in SBP was observed at the 30 and 40-minute postexercise time points compared with baseline (p # 0.05). The DBP and MBP were not significantly different between protocols (Figures 2 and 3). However, within the BFR protocol, significant decreases in DBP and MBP occurred at the 20, 30, and 40 minutes after exercise time points vs. baseline (p # 0.05). Table 1 shows the SBP, DBP, and MBP ES statistics after each RE protocol. The ES statistics for both RE protocols (BFR vs. HIE) presented trivial to small values, with the exception of a moderate ES for DBP at 20 minutes after the BFR protocol. Additionally, the ES statistics were generally greater for the BFR protocol at each time point postexercise.
DISCUSSION The aim of this study was to compare postexercise hypotensive responses after an HIE session vs. a low-intensity BFR session. The key finding was that there were no significant differences between protocols in the SBP, DBP, and MBP responses postexercise at any time point. However, within the BFR protocol, significant decreases in SBP occurred at 30and 40-minute postexercise, and significant decreases in MBP and DBP occurred at 20-, 30-, and 40-minute postexercise. These results may suggest that the duration of the VOLUME 29 | NUMBER 10 | OCTOBER 2015 |
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Hypotensive and Blood Flow Restriction hypotensive response might not only be dependent on differences in the rest interval between sets (i.e., 60 seconds in the BFR vs. 120 seconds in the HIE) or load intensity (40% in the BFR vs. 80% in the HIE) but rather on the ischemic effects induced during the BFR protocol. During both RE protocols (BFR vs. HIE), significant increases were observed in SBP, DBP, and MBP. The amount of muscle mass recruited during exercise is positively related to the increase in BP because of compression of vascular beds during concentric actions that occludes the circulation and consequently raises vascular resistance (5,9). Additionally, the application of external compression as in the BFR protocol reduced venous return with concomitant stimulation of group III (mechanosensitive) and group IV (metabosensitive) muscle afferents, promoting a reflexive increase in HR and arterial BP to maintain cardiac output (15,20). However, surprisingly, a recent study showed that carotid arterial compliance decreased with an HIE protocol vs. a BFR protocol, and this was correlated with SBP elevations during the HIE session (12). Several studies have observed a hypotensive response after HIE sessions (2,4,21). This response might occur because of a stress-mediated increase in nitric oxide synthase—an enzyme responsible for the conversion of L-arginine into nitric oxide— a small electrically neutral molecule that promotes vasodilation and reductions in peripheral vascular resistance (6,7,13). Additionally, the release of local substances such as potassium, prostaglandins, and adenosine might promote peripheral vasodilatation and a hypotensive response after traditional HIE sessions (8,16,25,26). Regarding RE intensity, Rezk et al. (16) concluded that sessions using either a low intensity (40% 1RM) or high intensity (80% 1RM), resulted in reduced SBP postexercise, attributed to decreased cardiac output that was not completely compensated by increased systemic peripheral vascular resistance. In this study, we observed small postexercise reductions in SBP for both the BFR (40% 1RM) and HIE (80% 1RM) protocols, respectively. However, in terms of ES, it was observed that the BFR protocol generally elicited a greater hypotensive response in SBP, DBP, and MBP. Conversely, Rossow et al. (18) compared the hypotensive effect (at 30- and 60-minute postexercise) of RE for the lower limbs under 3 conditions: HIE session (70% 1RM, 3 sets of 10 repetitions, 1-minute rest between sets) without BFR; lowintensity (20% of 1RM, 4 sets, 30 repetitions in the first set, 15 repetitions in 2, 3, and 4 sets, 30-second rest between sets) without BFR; and a low-intensity session with BFR (200 mm Hg; 5-cm wide cuff). The authors found that only the HIE protocol promoted significant hypotensive responses after 60 minutes. They speculated that the BFR protocol did not result in a hypotensive response because the load intensity may have been insufficient (20% of 1RM) and suggested that the accumulation of metabolites occurs only at intensities above 30% of 1RM (22). Thus, the accumulation of metabolites based on RE load intensity (with the concomitant decrease in pH) may
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potentiate the actions of vasodilator substances (e.g., potassium, prostaglandins, adenosine, and nitric oxide), producing increases in arteriole diameter and decreases in BP (7,8,26). Another key finding of our study was that the BFR protocol promoted a long-lasting hypotensive DBP response. Rossow et al. (18) found no significant hypotensive responses in DBP after their BFR protocol, which may have been because of inadequate sample size. Regardless, in this study, SBP, DBP, and MBP were transiently reduced after the BFR protocol. Our findings provide important information on hemodynamic responses, because they suggest beneficial effects in all BP parameters by using BFR in conjunction with RE. Lowintensity RE combined with BFR promotes increased VEGF, stimulating angiogenesis, which may become a good option for treating people affected by vascular diseases (23). The measurement of BP using the oscillometric method may have been a possible limitation of this study, but care was taken to calculate the appropriate sample size and food recall 24 hours before the collections were performed to increase the internal validity of the research. Additionally, other limiting factors that might be considered in future studies include levels of endothelium-dependent vasodilator agents, local metabolites, autonomic sympathetic activity, and cardiac output, which would provide further insight into the mechanisms behind the observed responses. In conclusion, both HIE protocol and low-intensity RE with BFR can be used to promote a postexercise hypotensive effect. The BFR protocol promoted a greater ES at most time points in SBP, DBP, and MBP. Therefore, it can be suggested that either RE approach tested can be used safely and effectively in normotensive subjects.
PRACTICAL APPLICATIONS This study indicates that low-intensity RE with BFR is an effective method to promote a significant hypotensive response. These results might also be prescribed for the treatment and prevention of hypertension. However, future experiments are required to analyze the safety and efficiency of this technique in hypertensive subjects. Additionally, the effect of the manipulation of different RE variables (load intensity, sets, repetition range, rest interval between sets) still has to be further investigated.
ACKNOWLEDGMENTS Dr. Alex Souto Maior and Dr. Roberto Sima˜o are supported by FAPERJ.
REFERENCES 1. ACSM. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. Baltimore, MD: Williams & Wilkins, 2014. 2. Bentes, CM, Costa, PB, Rodrigues Neto, G, Costa e Silva, GV, De Salles, BF, Miranda, HL, and Novaes, JS. Hypotensive effects and performance responses between different resistance training intensities and exercise orders in apparently health women. Clin Physiol Funct Imaging 34, 2014. Apr 1. doi: 10.1111/cpf.12144.
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Journal of Strength and Conditioning Research 3. Cornelissen, VA and Fagard, RH. Effect of resistance training on resting blood pressure: A meta-analysis of randomized controlled trials. J Hypertens 23: 251–259, 2005. 4. De Salles, BF, Maior, AS, Polito, M, Novaes, J, Alexander, J, Rhea, M, and Sima˜o, R. Influence of rest interval lengths on hypotensive response after strength training sessions performed by older men. J Strength Cond Res 24: 3049–3054, 2010. 5. Kacin, A and Strazar, K. Frequent low-load ischemic resistance exercise to failure enhances muscle oxygen delivery and endurance capacity. Scand J Med Sci Sports 2: 231–241, 2011. 6. Kawada, S and Ishii, N. Skeletal muscle hypertrophy after chronic restriction of venous blood flow in rats. Med Sci Sports Exerc 37: 1144–1150, 2005. 7. Lizardo, JH, Silveira, EA, Vassallo, DV, and Oliveira, EM. Post-resistance exercise hypotension in spontaneously hypertensive rats is mediated by nitric oxide. Clin Exp Pharmacol Physiol 35: 782–787, 2008. 8. MacDonald, JR. Potential causes, mechanisms, and implications of post-exercise hypotension. J Hum Hypertens 16: 225–236, 2002. 9. MacDougall, JD, Tuxen, D, Sale, DG, Moroz, JR, and Sutton, JR. Arterial blood pressure response to heavy resistance exercise. J Appl Physiol (1985) 58: 785–790, 1985. 10. Maior, AS, Paixa˜o, RC, Ribeiro, IC, Freitas, DGS, Mota, GR, and Marocolo, M. Acute responses of rate pressure product in sets of resistance exercise. Medicina Sportiva 18: 36–41, 2014. 11. Nascimento, C, Tibana, RA, Benik, FM, Fontana, KE, Ribeiro Neto, F, Santana, FS, Santos-Neto, L, Silva, RA, Silva, AO, Farias, DL, Balsamo, S, and Prestes, J. Sustained effect of resistance training on blood pressure and hand grip strength following a detraining period in elderly hypertensive women: A pilot study. Clin Interv Aging 9: 219–225, 2014. 12. Ozaki, H, Yasuda, T, Ogasawara, R, Sakamaki-Sunaga, M, Naito, H, and Abe, T. Effects of high-intensity and blood flow-restricted low-intensity resistance training on carotid arterial compliance: Role of blood pressure during training sessions. Eur J Appl Physiol 113: 167–174, 2013. 13. Queiroz, AC, Rezk, CC, Teixeira, L, Tinucci, T, Mion, D, and Forjaz, CL. Gender influence on post-resistance exercise hypotension and hemodynamics. Int J Sports Med 34: 939–944, 2013.
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16. Rezk, CC, Marrache, RCB, Tinucci, T, Mion, D Jr, and Forjaz, CLM. Post-resistance exercise hypotension, hemodynamics, and heart rate variability: Influence of exercise intensity. Eur J Appl Physiol 98: 105–112, 2006. 17. Rhea, MR. Determining the magnitude of treatment effects in strength training research through the use of the effect size. J Strength Cond Res 18: 918–920, 2004. 18. Rossow, LM, Fahs, CA, Sherk, VD, Seo, DI, Bemben, DA, and Bemben, MG. The effect of acute blood-flow-restricted resistance exercise on postexercise blood pressure. Clin Physiol Funct Imaging 31: 429–434, 2011. 19. Sabzmakan, L, Morowatisharifabad, MA, Mohammadi, E, Mazloomy-Mahmoodabad, SS, Rabiei, K, Naseri, MH, Shakibazadeh, E, and Mirzaei, M. Behavioral determinants of cardiovascular diseases risk factors: A qualitative directed content analysis. ARYA Atheroscler 10: 71–81, 2014. 20. Sakamaki, M, Fujita, S, and Sato, Y. Blood pressure response to slow walking combined with KAATSU in the elderly. Int J Kaatsu Training Res 4: 17–20, 2008. 21. Sima˜o, R, Fleck, SJ, Polito, M, Monteiro, W, and Farinatti, P. Effects of resistance training intensity, volume, and session format on the postexercise hypotensive response. J Strength Cond Res 19: 853–858, 2005. 22. Suga, T, Okita, K, Morita, N, Yokota, T, Hirabayashi, K, Horiuchi, M, Takada, S, Omokawa, M, Kinugawa, S, and Tsutsui, H. Dose effect on intramuscular metabolic stress during low-intensity resistance exercise with blood flow restriction. J Appl Physiol (1985) 108: 1563–1567, 2010. 23. Takano, H, Morita, T, Iida, H, Asada, K, Kato, M, Uno, K, Hirose, K, Matsumoto, A, Takenaka, K, Hirata, Y, Eto, F, Nagai, R, Sato, Y, and Nakaajima, T. Hemodynamic and hormonal responses to a shortterm low-intensity resistance exercise with the reduction of muscle blood flow. Eur J Appl Physiol 95: 65–73, 2005. 24. Takarada, Y, Sato, Y, and Ishii, N. Effects of resistance exercise combined with vascular occlusion on muscle function in athletes. Eur J Appl Physiol 86: 308–314, 2002.
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25. Whelton, PK, Appel, LJ, Sacco, RL, Anderson, CA, Antman, EM, Campbell, N, Dunbar, SB, Frohlich, ED, Hall, JE, Jessup, M, Labarthe, DR, MacGregor, GA, Sacks, FM, Stamler, J, Vafiadis, DK, and Van Horn, LV. Sodium, blood pressure, and cardiovascular disease: Further evidence supporting the american heart association sodium reduction recommendations. Circulation 126: 2880–2889, 2012.
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SALLES,2
AND
1
University Augusto Motta (UNISUAM), Master Program in Rehabilitation Sciences, Rio de Janeiro, Brazil; 2Federal University of Rio de Janeiro, Physical Education Post-Graduation Program, Rio de Janeiro, Brazil; and 3Department of Kinesiology and Sports Studies, Eastern Illinois University, Charleston, Illinois ABSTRACT
Maior, AS, Sima˜o, R, Martins, MSR, Salles, BFd, and Willardson, JM. Influence of blood flow restriction during low-intensity resistance exercise on the postexercise hypotensive response. J Strength Cond Res 29(10): 2894–2899, 2015—Low-intensity resistance exercise (RE) combined with blood flow restriction (BFR) has been shown to promote similar increases in strength and hypertrophy as traditional high-intensity RE without BFR. However, the effect of BFR on the acute postexercise hypotensive response has received limited examination. Therefore, the purpose of this study was to compare high-intensity exercise (HIE) vs. low-intensity RE with BFR on the postexercise hypotensive response in normotensive young subjects. Fifteen men (age: 23.4 6 3.4 years) performed the following 2 experimental protocols in randomized order: (a) 3 sets of biceps curls (BCs) at 80% of 1 repetition maximum (RM) and 120-second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60-second rest between sets. Analysis of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was conducted for 60 minutes after both protocols. The values for SBP, DBP, and mean blood pressure (MBP) at baseline and postexercise were not significantly different between the HIE vs. the BFR protocol. However, within the BFR protocol, significant decreases (p # 0.05) in SBP occurred at 30 minutes (125.86 6 9.33 mm Hg) and 40 minutes (125.53 6 10.19 mm Hg) after exercise when compared with baseline (132.86 6 9.12 mm Hg) and significant decreases in DBP and MBP occurred at 20 minutes, 30 minutes, and 40 minutes after exercise vs. baseline (p # 0.05). Therefore, we conclude that exercises engaging a relatively small amount of muscle mass, such as the BC (or other similar single joint
Address correspondence to Alex S. Maior, [email protected]. 29(10)/2894–2899 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association
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exercises), might be performed at a lower intensity with BFR to promote a postexercise hypotensive response.
KEY WORDS hypotension, Kaatsu training, vascular occlusion, blood pressure
INTRODUCTION
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ardiovascular disease is associated with primary risk factors that can be controlled, treated, or modified, such as high blood pressure (BP). Physical inactivity is also known as a primary risk factor for cardiovascular disease, and people who are less active and less fit have a 30–50% greater risk for having high BP (19). However, meta-analytical data suggest that resistance exercise (RE) can decrease mean resting BP by as much as 3–4 mm Hg (3). Consequently, RE is prescribed for the control of resting BP in hypertensive and normotensive individuals (2,4,11,13). Resistance exercise involves multiple variables that can be arranged to specifically meet training goals and individual needs, such as exercise order, rest interval between sets, exercise mode, training frequency, movement velocity, training volume, repetitions per set, number of sets, type of muscle action, and the load intensity (4). Therefore, knowledge of cardiovascular responses during and after RE may facilitate better control of hemodynamic parameters and greater effectiveness of certain RE regimens. The magnitude and direction of BP and heart rate (HR) responses during RE are directly related to exertion level, number of repetitions and sets, rest interval between sets, and motor unit recruitment (4,10). Traditional dynamic RE protocols stimulate increases in HR and stroke volume. Concomitantly, greater venous return to heart is facilitated by greater breathing frequency, pumping action of skeletal muscles, and venoconstriction. Conversely, low-intensity RE (20–50% of 1 repetition maximum [1RM]) with the addition of blood flow restriction (BFR) promotes an increase in HR to maintain cardiac output, because of the decrease in stroke volume, which results from restricted blood flow, and consequently, reduces venous blood return (23). Thus, performing RE with
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Journal of Strength and Conditioning Research the addition of BFR stimulates compensatory adaptations to facilitate greater venous return, such as significant increases in vascular endothelial growth factor (VEGF) (23). A recent study (12) showed a significant decrease in carotid arterial compliance that was associated with elevations in systolic blood pressure (SBP) during exercise sessions that consisted of a high-intensity exercise (HIE) (75% of a 1RM) load vs. a low-intensity load with BFR (30% of a 1RM) over 6 weeks. Conversely, another study demonstrated that a postexercise hypotensive response did not occur after a low-intensity RE session with BFR (20% of 1RM), whereas the opposite was found for an HIE session (70% of 1RM) (18). Few studies have evaluated the association between the postexercise hypotensive response and low-intensity RE combined with BFR. Low-intensity RE with BFR might promote greater shear stress against blood vessel walls on restoration of blood flow that occurs with release of occlusive pressure, which may stimulate greater nitric oxide production to promote vasodilation, and a hypotensive response postexercise (6). The RE load intensity can affect the duration but not the magnitude of the postexercise hypotensive response (3,4,8). The magnitude of the postexercise hypotensive response may, to some extent, depend on an individual’s health status. The identification of specific BP responses that might be associated with manipulation of training variables is important to ensure the optimal, and appropriate, prescription of RE for individuals concerned with BP control, such as those with chronic hypertension. Thus, bearing in mind the importance of examining the postexercise hypotensive response to promote greater efficacy and safety during low-intensity RE with BFR, the purpose of this study was to compare an HIE session vs. low-intensity RE with BFR on the postexercise hypotensive response in normotensive young subjects.
METHODS Experimental Approach to the Problem
To compare an HIE protocol vs. a low-intensity RE protocol with BFR on the postexercise hypotensive response, subjects performed 2 RE sessions. After measurement of a 1RM load for the standing free-weight biceps curl (BC) in test and retest sessions, subjects performed 2 RE sessions in random order, which included the following: (a) 3 sets of BCs at 80% of 1RM and 120second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60-second rest between sets. Blood pressure was measured before and at 10minute intervals for 60 minutes after each RE session. Subjects
Fifteen healthy men (age: 23.4 6 3.4 years, body mass: 78.6 6 6.3 kg, height: 177.2 6 7.1 cm, BMI: 25 6 2.4 kg$m22) with at least 1 year of recreational RE experience were asked to participate in this study. All subjects were over 18 years old and completed the Physical Activity Readiness Questionnaire and signed an informed consent according to the Declaration of
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Helsinki. The experimental procedures were approved by the Ethics Committee of the Institution and were performed in accordance with the international ethical standards. The following additional exclusion criteria were adopted: (a) use of drugs that could affect cardiorespiratory responses, (b) bone-, joint-, or muscle-diagnosed problems that could limit the execution of BC, (c) systemic hypertension ($140/90 mm Hg or use of antihypertensive medication), (d) metabolic disease, (e) use of exogenous anabolic-androgenic steroids, drugs, or medication with potential effects on physical performance. Anthropometric and Hemodynamic Measurements
Volunteers attended the laboratory a total of 4 times with 48 hours between visits. During the first visit, anthropometric and hemodynamic data were collected, as well as a 1RM assessment for the standing free-weight BC. During the second visit, the 1RM assessment was repeated, and the RE sessions were performed during the third and fourth visits with or without BFR. All testing was performed between 1:00 PM and 3:00 PM. Subjects received a light lunch 2 hours before each laboratory visit. Coffee, tea, alcohol, and tobacco intake were prohibited for 48 hours, and subjects avoided formal and strenuous exercise for 48 hours before each visit. Body mass was measured to the nearest 0.1 kg using a calibrated physician’s beam scale (model 31; Filizola, Sa˜o Paulo, Brazil), with the men dressed in shorts. Height was determined without shoes to the nearest 0.1 cm using a stadiometer scale (model 31; Filizola) after a voluntary deep inspiration. Body fat percentage (%) was estimated using the 7-site skinfold method according to the guidelines of the American College of Sports Medicine (1). The mid upper arm muscle circumference was estimated by circumference of the bone and muscle portions of the upper arm. The triceps skinfold was measured to represent the thickness of the subcutaneous fat that surrounds the muscle. The following formula was used to estimate the muscle-bone cross-sectional area (1):
TSF Muscle-bone CSA ¼ ΜC2 p3 : 10 Before commencement of each RE session, subjects rested quietly in a supine position for 10 minutes before measurement of resting BP. After each RE session, BP was measured immediately postexercise and in 10-minute intervals for 60 minutes, resulting in a total of 7 readings after each RE session. Before and after each session, subjects were fitted with ambulatory BP monitoring equipment (PM50 Monitor; Contec Medical, Beijing, China), and this equipment was used for all preand postexercise BP measurements. The ambulatory BP equipment was autocalibrated before each use to ensure accuracy. Spurious readings, because of factors such as movement artifact, were automatically edited by the software. During BP pre- and postexercise monitoring, subjects remained in a supine position in a temperature-controlled quiet room (228 C). VOLUME 29 | NUMBER 10 | OCTOBER 2015 |
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Hypotensive and Blood Flow Restriction range of motion for the exercise (BC) had to be completed. The BC range of motion for a successful repetition was defined as follows: elbows beginning in full extension followed by full flexion, whereas maintaining perfect postural alignment with no torso sway. The 1RM test has been described previously and for reliability, the following strategies were adopted (10): (a) standardized instructions about the testing procedures were given to subjects before test; (b) subjects received standardized instructions concerning exercise technique; (c) verbal encouragement was provided during tests; and (d) the mass of all weights and bars was determined using a precision scale. Strength Training Sessions and Blood Flow Restriction
A standing free-weight BC with a straight bar was selected for use in this study because of its common use in RE programs and because it has been used in previous studies examining BFR (14,24). The 1RM tests were performed after the anthropometric measurements on the first day. After 48 hours, the 1RM test was repeated to determine test-retest reliability. The heaviest load achieved on either test day was considered the 1RM. The 1RM loads were determined in fewer than 5 attempts with a rest interval of 5 minutes between attempts (10). No pause was allowed between the concentric and eccentric phases of a repetition or between repetitions. For a repetition to be successful, a complete
The subjects performed a bilateral BC exercise with a straight bar in a standing position. The 2 strength training sessions were performed on nonconsecutive days and in random order, which included the following: (a) 3 sets of BCs at 80% of 1RM and 120-second rest between sets (HIE protocol) and (b) 3 sets of BCs at 40% of 1RM with BFR and 60second rest between sets. In BFR protocol, the proximal portion of both arms was compressed by a specially designed elastic belt (width 140 mm, length 200 mm). The belt contained a small pneumatic bag along its inner surface. To partially occlude muscle blood flow, the cuff was inflated to a pressure of 20 mm Hg below the acute SBP determined after 15 minutes of semirecumbent resting (14). The mean restrictive pressure throughout the period of training was 109.4 6 7.33 mm Hg. The BFR was maintained throughout the session of exercise, which lasted 251.1 6 22.3 seconds for the BFR protocol and 232.7 6 22.2 seconds for the HIE protocol. The partial occlusion of muscle blood flow was restored immediately after the RE session. The BFR protocol resulted in a total
Figure 2. Diastolic blood pressure (DBP) at rest, immediately postexercise, and at 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10– 60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
Figure 3. Mean blood pressure (MBP) at rest, immediately postexercise, and during 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10–60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
Figure 1. Mean systolic blood pressure (SBP) at rest, immediately postexercise, and at 10-minute intervals for 60 minutes after resistance exercise (RE) for the BFR protocol vs. the HIE protocol. Data are presented as mean 6 SD. #p # 0.05 = significantly greater than postexercise measurements (10–60 minutes); §p # 0.05 = significantly greater than rest; *p # 0.05 = significantly less than rest.
One Repetition Maximum Test
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TABLE 1. Comparison of blood pressure (BP) effect size (ES) statistics traditional HIE protocol vs. BFR protocol.* 10 min Systolic blood pressure BFR HIE Diastolic blood pressure BFR HIE Mean blood pressure BFR HIE
20 min
30 min
40 min
50 min
60 min
20.063 Trivial 0.122 Trivial
0.374 Small 0.281 Trivial
0.741 Small 0.219 Trivial
0.777 Small 0.447 Small
0.593 Small 0.518 Small
0.699 Small 0.421 Small
0.485 Small 0.052 Trivial
0.832 Moderate 0.112 Trivial
0.725 Small 0.238 Trivial
0.684 Small 0.231 Trivial
0.577 Small 0.099 Trivial
0.291 Trivial 20.265 Trivial
0.025 Trivial 0.13 Trivial
0.573 Small 0.244 Trivial
0.727 Small 0.317 Trivial
0.706 Small 0.569 Small
0.507 Small 0.358 Small
0.363 Small 20.04 Trivial
*BFR = blood flow restriction protocol; HIE = high-intensity resistance exercise protocol.
of 47.1 6 9.5 repetitions and the HIE protocol in a total of 21.8 6 5.9 repetitions. During each RE session, subjects were verbally encouraged to perform all sets to concentric failure, using the consistent definition of a complete range of motion used for the 1RM test. No attempt was made to control repetition velocity. During all RE sessions, subjects were asked not to perform a Valsalva maneuver. All of the exercise sessions were preceded by a 10-minute warm-up on an upper body ergometer (Technogym, Italy) with an intensity of 20 W. Statistical Analyses
All data are presented as mean 6 SD. The statistical analysis was initially performed using the Shapiro-Wilk normality test and the homoscedasticity test (Bartlett criterion). To test the reproducibility of the 1RM load between the test and retest, we used the intraclass correlation coefficient (ICC). To compare potential differences in postexercise SBP, diastolic blood pressure (DBP), and mean blood pressure (MBP) in the BFR and HIE protocols, a repeatedmeasures 2-way analysis of variance (ANOVA) with Bonferroni post hoc tests was used. Comparisons withingroups for BP were performed with a 1-way repeatedmeasures ANOVA followed by Tukeys post hoc tests. The level of significance was set at p # 0.05 for all statistical comparisons. Additionally, to determine the magnitude of the findings, effect size (ES; the difference between pretest and posttest scores divided by the pretest SD) statistics were calculated for the SBP and DBP responses for each RE session, and the scale proposed by Rhea (17) was used to determine the magnitude of the ES. All statistical analyses were performed using GraphPad Prism 5.0 (GraphPad Software Inc., San Diego, CA, USA).
RESULTS The ICC for the BC was 0.92 (p , 0.001), Figures 1–3 summarize the acute hemodynamic responses for each protocol (BFR vs. HIE). The SBP values were not significantly different between protocols at baseline and postexercise at each time point (Figure 1). However, within the BFR protocol, a significant decrease in SBP was observed at the 30 and 40-minute postexercise time points compared with baseline (p # 0.05). The DBP and MBP were not significantly different between protocols (Figures 2 and 3). However, within the BFR protocol, significant decreases in DBP and MBP occurred at the 20, 30, and 40 minutes after exercise time points vs. baseline (p # 0.05). Table 1 shows the SBP, DBP, and MBP ES statistics after each RE protocol. The ES statistics for both RE protocols (BFR vs. HIE) presented trivial to small values, with the exception of a moderate ES for DBP at 20 minutes after the BFR protocol. Additionally, the ES statistics were generally greater for the BFR protocol at each time point postexercise.
DISCUSSION The aim of this study was to compare postexercise hypotensive responses after an HIE session vs. a low-intensity BFR session. The key finding was that there were no significant differences between protocols in the SBP, DBP, and MBP responses postexercise at any time point. However, within the BFR protocol, significant decreases in SBP occurred at 30and 40-minute postexercise, and significant decreases in MBP and DBP occurred at 20-, 30-, and 40-minute postexercise. These results may suggest that the duration of the VOLUME 29 | NUMBER 10 | OCTOBER 2015 |
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Hypotensive and Blood Flow Restriction hypotensive response might not only be dependent on differences in the rest interval between sets (i.e., 60 seconds in the BFR vs. 120 seconds in the HIE) or load intensity (40% in the BFR vs. 80% in the HIE) but rather on the ischemic effects induced during the BFR protocol. During both RE protocols (BFR vs. HIE), significant increases were observed in SBP, DBP, and MBP. The amount of muscle mass recruited during exercise is positively related to the increase in BP because of compression of vascular beds during concentric actions that occludes the circulation and consequently raises vascular resistance (5,9). Additionally, the application of external compression as in the BFR protocol reduced venous return with concomitant stimulation of group III (mechanosensitive) and group IV (metabosensitive) muscle afferents, promoting a reflexive increase in HR and arterial BP to maintain cardiac output (15,20). However, surprisingly, a recent study showed that carotid arterial compliance decreased with an HIE protocol vs. a BFR protocol, and this was correlated with SBP elevations during the HIE session (12). Several studies have observed a hypotensive response after HIE sessions (2,4,21). This response might occur because of a stress-mediated increase in nitric oxide synthase—an enzyme responsible for the conversion of L-arginine into nitric oxide— a small electrically neutral molecule that promotes vasodilation and reductions in peripheral vascular resistance (6,7,13). Additionally, the release of local substances such as potassium, prostaglandins, and adenosine might promote peripheral vasodilatation and a hypotensive response after traditional HIE sessions (8,16,25,26). Regarding RE intensity, Rezk et al. (16) concluded that sessions using either a low intensity (40% 1RM) or high intensity (80% 1RM), resulted in reduced SBP postexercise, attributed to decreased cardiac output that was not completely compensated by increased systemic peripheral vascular resistance. In this study, we observed small postexercise reductions in SBP for both the BFR (40% 1RM) and HIE (80% 1RM) protocols, respectively. However, in terms of ES, it was observed that the BFR protocol generally elicited a greater hypotensive response in SBP, DBP, and MBP. Conversely, Rossow et al. (18) compared the hypotensive effect (at 30- and 60-minute postexercise) of RE for the lower limbs under 3 conditions: HIE session (70% 1RM, 3 sets of 10 repetitions, 1-minute rest between sets) without BFR; lowintensity (20% of 1RM, 4 sets, 30 repetitions in the first set, 15 repetitions in 2, 3, and 4 sets, 30-second rest between sets) without BFR; and a low-intensity session with BFR (200 mm Hg; 5-cm wide cuff). The authors found that only the HIE protocol promoted significant hypotensive responses after 60 minutes. They speculated that the BFR protocol did not result in a hypotensive response because the load intensity may have been insufficient (20% of 1RM) and suggested that the accumulation of metabolites occurs only at intensities above 30% of 1RM (22). Thus, the accumulation of metabolites based on RE load intensity (with the concomitant decrease in pH) may
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potentiate the actions of vasodilator substances (e.g., potassium, prostaglandins, adenosine, and nitric oxide), producing increases in arteriole diameter and decreases in BP (7,8,26). Another key finding of our study was that the BFR protocol promoted a long-lasting hypotensive DBP response. Rossow et al. (18) found no significant hypotensive responses in DBP after their BFR protocol, which may have been because of inadequate sample size. Regardless, in this study, SBP, DBP, and MBP were transiently reduced after the BFR protocol. Our findings provide important information on hemodynamic responses, because they suggest beneficial effects in all BP parameters by using BFR in conjunction with RE. Lowintensity RE combined with BFR promotes increased VEGF, stimulating angiogenesis, which may become a good option for treating people affected by vascular diseases (23). The measurement of BP using the oscillometric method may have been a possible limitation of this study, but care was taken to calculate the appropriate sample size and food recall 24 hours before the collections were performed to increase the internal validity of the research. Additionally, other limiting factors that might be considered in future studies include levels of endothelium-dependent vasodilator agents, local metabolites, autonomic sympathetic activity, and cardiac output, which would provide further insight into the mechanisms behind the observed responses. In conclusion, both HIE protocol and low-intensity RE with BFR can be used to promote a postexercise hypotensive effect. The BFR protocol promoted a greater ES at most time points in SBP, DBP, and MBP. Therefore, it can be suggested that either RE approach tested can be used safely and effectively in normotensive subjects.
PRACTICAL APPLICATIONS This study indicates that low-intensity RE with BFR is an effective method to promote a significant hypotensive response. These results might also be prescribed for the treatment and prevention of hypertension. However, future experiments are required to analyze the safety and efficiency of this technique in hypertensive subjects. Additionally, the effect of the manipulation of different RE variables (load intensity, sets, repetition range, rest interval between sets) still has to be further investigated.
ACKNOWLEDGMENTS Dr. Alex Souto Maior and Dr. Roberto Sima˜o are supported by FAPERJ.
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