A method to standardize the blood flow restriction pressure by an elastic cuff

Acute Effects of a Practical Blood Flow Restriction Device During Swimming Exercise

Purpose: The present study aimed to analyze: 1) the reliability of the tissue saturation index (TSI) and ratings of perceived discomfort (RPD) responses wearing a neoprene practical cuff (PrC), comparing with the responses from traditional (TrC) pneumatic cuffs (study I); 2) the effects of PrC on metabolic (blood lactate concentration, BLC), perceptual (rate of perceived effort, RPE) and kinematic responses at sub-maximal swimming velocities (study II). Methods: Study I; 1) PrC test-retest at rest and during swimming ergometer exercise; 2) BFR at rest with TrC inflated to different percentages of the minimum arterial occlusion pressure (MAOP; 60, 80, 100, 120 and 140%). Test-retest reliability of TSI and RPD was assessed by the intraclass correlation coefficient (ICC) and comparisons among conditions were analyzed by one-way repeated-measures ANOVA. Study II; 1) 50, 200 and 400 m swimming performances; 2) sub-maximal incremental swimming protocol with and without PrC. Two-way repeated measures ANOVA was used to compare all variables during sub-maximal velocities. Results: TSI (ICC = 0.81; 95%CI 0.62-0.91) and RPD (ICC = 0.97; 95%CI 0.94-0.99) were reliable under restricted exercise using PrC. TSI during restricted exercise was lower (p <.001) compared to unrestricted exercise (6.8 ± 6.1% vs. 21.6 ± 8.2% of physiological normalization). PrC showed higher BLC only at or above 91% of critical velocity (p < .03), while stroke rate and RPE were higher (p < .005), and stroke length was lower (p < .03) during all swimming velocities. Conclusion: This easy-to-handle and affordable practical BFR device increased physiological stress at sub-maximal efforts which could be an additional training tool for swimmers.

Low-load Resistance Exercise with Perceptually Primed Practical Blood Flow Restriction Induces Similar Motor Performance Fatigue, Physiological Changes, and Perceptual Responses Compared to Traditional Blood Flow Restriction in Males and Females

In the recent past, practical blood flow restriction (pBFR) using non-pneumatic, usually elastic cuffs has been established as a cost-effective alternative to traditional blood flow restriction (BFR) using pneumatic cuffs, especially for training in large groups. This study investigated whether low-load resistance exercise with perceptually primed pBFR using an elastic knee wrap is suitable to induce similar motor performance fatigue as well as physiological and perceptual responses compared to traditional BFR using a pneumatic nylon cuff in males and females. In a randomized, counterbalanced cross-over study, 30 healthy subjects performed 4 sets (30-15-15-15 repetitions) of unilateral knee extensions at 20% of their one-repetition-maximum. In the pBFR condition, each individual was perceptually primed to a BFR pressure corresponding to 60% of their arterial occlusion pressure. Before and after exercise, maximal voluntary torque, maximal muscle activity, and cuff pressure-induced discomfort were assessed. Moreover, physiological (i.e., muscle activity, muscle oxygenation) and perceptual responses (i.e., effort and exercise-induced leg muscle pain) were recorded during exercise. Moderate correlations with no differences between pBFR and BFR were found regarding the decline in maximal voluntary torque and maximal muscle activity. Furthermore, no to very strong correlations between conditions, with no differences, were observed for muscle activity, muscle oxygenation, and perceptual responses during exercise sets. However, cuff pressure-induced discomfort was lower in the pBFR compared to the BFR condition. These results indicate that low-load resistance exercise combined with perceptually primed pBFR is a convenient and less discomfort inducing alternative to traditional BFR. This is especially relevant for BFR training with people who have a low cuff-induced discomfort tolerance.

Blood flow restriction pressure for narrow cuffs (5 cm) cannot be estimated with precision

Blood flow restriction pressures are set relative to the lowest pressure needed to occlude blood flow with that specific cuff. Due to pressure limitations of some devices, it is often not possible to occlude blood flow in all subjects and apply a known relative pressure in the lower body with a 5 cm wide cuff.Objective. To use a device capable of generating high pressures (up to 907 mmHg) to create and validate an estimation equation for the 5 cm cuff in the lower body using a 12 cm cuff.Approach. 170 participants had their arterial occlusion pressure (AOP) with a 5 cm and 12 cm cuff and their thigh circumference measured in their right leg. The sample was randomly allocated to a prediction group (66%) and validation group (33%). Thigh circumference and 12 cm AOP were used as predictors. A Bland-Altman plot was constructed to assess agreement between measured and predicted values.Main results. The mean difference (95% confidence interval) between the observed (336.8 mmHg) and the predicted (343.9 mmHg) 5 cm AOP was 7.1 (-11.9, 26.1) mmHg. The 95% limits of agreement were -133.6 to 147.8 mmHg. There was a negative relationship between the difference and the average of predicted and measured 5 cm AOP (B= -0.317,p= 0.000043).Significance. Although this was the first study to quantify AOP over 600 mmHg with a 5 cm cuff, our equation is not valid across all levels of pressure. If possible, larger cuff widths should be employed in the lower body.

Influence of cuff stiffness on hemodynamics and perceived cuff pressure in the upper extremities in males and females: implications for practical blood flow restriction training

BACKGROUND

Practical blood flow restriction (pBFR) during exercise is a cost-saving alternative to traditional blood flow restriction using pneumatic cuffs, particularly when exercising in a group setting. Depending on the pBFR technique, several factors (e.g., cuff width, limb circumference) have already been shown to be of importance when applying the pBFR pressure. Given that elastic cuffs are often used for pBFR, the cuff stiffness might be an additional influencing factor. Therefore, the present study compared the acute effects of three elastic cuffs with identical width but different stiffness (high stiffness (HS), medium stiffness (MS), and low stiffness (LS)) on hemodynamic measures and perceived cuff pressure at rest.

METHODS

In a randomized, counter-balanced cross-over study, 36 young and normotensive participants completed three experimental trials. After a 10-min rest period in supine position, the cuff was loosely and proximally applied to the right upper arm. Following baseline data recording, the cuff was successively tightened in 10%-increments with respect to the limb circumference (%overlap) until arterial blood flow was occluded. At baseline and during each %overlap, systolic peak blood flow velocity of the brachial artery, rating of perceived cuff pressure, as well as muscle oxygen saturation and total hemoglobin concentration of the biceps brachii muscle were recorded.

RESULTS

The %overlap required to occlude arterial blood flow was different between the three cuffs (HS: 30.9 ± 3.8%, MS: 43.9 ± 6.1%, LS: 54.5 ± 8.3%). Furthermore, at 30% overlap, systolic peak blood flow velocity was lower when applying the HS (9.0 ± 10.9 cm∙s- 1) compared to MS (48.9 ± 21.9 cm∙s- 1) and LS cuff (62.9 ± 19.1 cm∙s- 1). Rating of perceived cuff pressure at 30% overlap was higher when using the HS (6.5 ± 1.5 arbitrary unit (a.u.)) compared to MS (5.1 ± 1.4 a.u.) and LS cuff (4.9 ± 1.5 a.u.) with no difference between the MS and LS cuff. However, muscle oxygen saturation and total hemoglobin concentration were not different between the three cuffs.

CONCLUSIONS

The present study revealed that the cuff stiffness influenced blood flow velocity and arterial occlusion pressure. Therefore, cuff stiffness seems an important factor for the application of pBFR.

Practical Blood Flow Restriction Training: New Methodological Directions for Practice and Research

Most studies with blood flow restriction (BFR) training have been conducted using devices capable of regulating the restriction pressure, such as pneumatic cuffs. However, this may not be a viable option for the general population who exercise in gyms, squares and sports centers. Thinking about this logic, practical blood flow restriction (pBFR) training was created in 2009, suggesting the use of elastic knee wraps as an alternative to the traditional BFR, as it is low cost, affordable and practical. However, unlike traditional BFR training which seems to present a consensus regarding the prescription of BFR pressure based on arterial occlusion pressure (AOP), studies on pBFR training have used different techniques to apply the pressure/tension exerted by the elastic wrap. Therefore, this Current Opinion article aims to critically and chronologically examine the techniques used to prescribe the pressure exerted by the elastic wrap during pBFR training. In summary, several techniques were found to apply the elastic wrap during pBFR training, using the following as criteria: application by a single researcher; stretching of the elastic (absolute and relative overlap of the elastic); the perceived tightness scale; and relative overlap of the elastic based on the circumference of the limbs. Several studies have shown that limb circumference seems to be the greatest predictor of AOP. Therefore, we reinforce that applying the pressure exerted by the elastic for pBFR training based on the circumference of the limbs is an excellent, valid and safe technique.

A comparison of variability between absolute and relative blood flow restriction pressures

Recommendations are that blood flow restriction (BFR) be applied relative to arterial occlusion pressure (AOP) to provide a similar stimulus.

PURPOSE

Compare variability of the change in blood flow, shear rate, and discomfort between recommended relative pressures and an absolute pressure.

METHODS

During one visit, brachial arterial blood flow was measured in 91 participants using pulse-wave Doppler ultrasonography. After 5-min seated rest, AOP was measured. Following another 5-min rest, blood flow and discomfort were assessed twice before cuff inflation as controls (C1 and C2), then again with a cuff inflated to each BFR pressure (all measures separated by 1-min). Change scores from C1 to all subsequent measures were calculated (i.e., C2-C1; 40%AOP-C1; 80%AOP-C1; 100mmHg-C1). Variability of the changes were compared via pairwise modified Pitman-Morgan tests (α=.008).

RESULTS

Variance (95%CI) of the change for blood flow (mL/min), shear rate (1/sec), and discomfort (AU) had similar trends. C2-C1 differed from all conditions (all p<.001), 40%AOP-C1 differed from 80%AOP-C1 and 100mmHg-C1 (all p<.001), which did not differ (both p≥.117). Blood flow: C2-C1=469.79 (357.90, 644.07), 40%AOP-C1=1263.18 (962.34, 1731.80), 80%AOP-C1=1752.90 (1335.42, 2403.18), 100mmHg-C1=1603.18 (1221.36, 2197.92); Shear rate: C2-C1=6248.24 (4760.10, 8566.15), 40%AOP-C1=14625.30 (11142.06, 20050.95), 80%AOP-C1=22064.02 (16809.13, 30249.27), 100mmHg-C1=20778.76 (15829.98, 28487.21); Discomfort: C2-C1=0.07 (0.05, 0.08), 40%AOP-C1=2.03 (1.55, 2.78), 80%AOP-C1=4.26 (3.25, 5.84), 100mmHg-C1=4.50 (3.43, 6.17).

CONCLUSION

Contrary to previous suggestions, applying relative pressures does not necessarily guarantee a similar stimulus. It seems that higher pressures produce more variable changes even if the external pressure applied is made relative to each individual. This article is protected by copyright. All rights reserved.

Perceived Barriers to Blood Flow Restriction Training

Blood flow restriction (BFR) training is increasing in popularity in the fitness and rehabilitation settings due to its role in optimizing muscle mass and strength as well as cardiovascular capacity, function, and a host of other benefits. However, despite the interest in this area of research, there are likely some perceived barriers that practitioners must overcome to effectively implement this modality into practice. These barriers include determining BFR training pressures, access to appropriate BFR training technologies for relevant demographics based on the current evidence, a comprehensive and systematic approach to medical screening for safe practice and strategies to mitigate excessive perceptual demands of BFR training to foster long-term compliance. This manuscript attempts to discuss each of these barriers and provides evidence-based strategies and direction to guide clinical practice and future research.

Conditioning participants to a relative pressure: implications for practical blood flow restriction

OBJECTIVE

To develop a valid method of applying blood flow restriction when the pressure cannot be known. This method involves conditioning the individual to what the goal pressure should be, such that the participant is able to recognize the sensation associated with that specific pressure.

APPROACH

Participants were conditioned to 40% of their arterial occlusion pressure (AOP) by oscillating between pressures that were too high (60%) and pressures that were too low (20%). Incorrect pressures were used to highlight pressure sensations surrounding the correct pressure that participants would be asked to later identify. Participants made attempts to estimate pressures at 5 min and 24 h following the conditioning stimulus.

MAIN RESULTS

A total of 40 participants completed this study. Estimated pressures at 5 min post conditioning were similar to the target pressure (-2 (-7, 3) mmHg; probability of H0: 0.675). However, pressures at 24 h post conditioning were underestimated as compared to the target pressure (-7 (-13, -2) mmHg). Additionally, pressures at 24 h appeared to be less than that at 5 min (-4.7 (-8.6, 0.9) mmHg; probability of H1: 0.84). The average absolute error was 11.2 mmHg (7.4% AOP) for 5 min and 14.0 mmHg (9.2% AOP) at 24 h.

SIGNIFICANCE

Although pressure estimations were underestimated at 24 h post conditioning, the majority of estimated pressures were between the upper and lower pressures used for the conditioning stimulus. Future research is needed to clarify and potentially refine what appears to be a promising method of estimation.

Does Acute Blood Flow Restriction with Pneumatic and Non-Pneumatic Non-Elastic Cuffs Promote Similar Responses in Blood Lactate, Growth Hormone, and Peptide Hormone?

Blood flow restriction (BFR) can be used during resistance training (RT) through pressure application with pneumatic (pressurized) cuffs (PC) or non-pneumatic (practical) cuffs (NPC). However, PC are expensive and difficult to use in the gym environment compared to NPC. The main aim was to compare, correlate, and verify the hormonal and metabolic responses between PC and NPC during a low-load BFR during RT of the upper-body. The secondary aim was to compare blood lactate (BLa) concentration between pre- and post-exercise (2-min into recovery), as well as growth hormone (GH) and insulin-like growth factor 1 (IGF-1) concentration before, 10-min, and 15-min post exercise. Sixteen trained men randomly and alternately completed two experimental RT protocols of the upper-body : A) RT with BFR at 20% 1RM using PC (RT-BFR-PC) and (B) RT with BFR at 20% 1RM using NPC (RT-BFR-NPC) in the bench press, wide-grip lat pulldown, shoulder press, triceps pushdown, and biceps curl exercises. There was no significant difference in BLa 2-min post exercise (p=0.524), GH 10-min (p=0.843) and 15-min post exercise (p=0.672), and IGF-1 10-min (p=0.298) and 15-min post exercise (p=0.201) between RT-BFR-PC and RT-BFR-NPC. In addition, there was a moderate correlation, satisfactory ICCs, and agreement between both protocols in metabolic and hormonal responses. The experimental sessions promoted significant increases in GH and BLa, but not in IGF-1 (p<0.05). The absence of a significant difference between RT-BFR-PC and RT-BFR-NPC in metabolic and hormonal responses highlight the applicability of NPC as a low-cost and easy-to-use tool for BFR upper-body RT.

Perioperative Blood Flow Restriction Rehabilitation in Patients Undergoing ACL Reconstruction: A Systematic Review

Background:

Low-load blood flow restriction (BFR) training has attracted attention as a potentially effective method of perioperative clinical rehabilitation for patients undergoing orthopaedic procedures.

Purpose:

To (1) compare the effectiveness of low-load BFR training in conjunction with a standard rehabilitation protocol, pre- and postoperatively, and non-BFR interventions in patients undergoing anterior cruciate ligament reconstruction (ACLR) and (2) evaluate protocols for implementing BFR perioperatively for patients undergoing ACLR.

Study Design:

Systematic review; Level of evidence, 2.

Methods:

A systematic review of the 3 medical literature databases was conducted to identify all level 1 and 2 clinical trials published since 1990 on BFR in patients undergoing ACLR. Patient demographics from included studies were pooled. Outcome data were documented, including muscle strength and size, and perceived pain and exertion. A descriptive analysis of outcomes from BFR and non-BFR interventions was performed.

Results:

A total of 6 studies (154 patients; 66.2% male; mean ± SD age, 24.2 ± 3.68 years) were included. Of these, 2 studies examined low-load BFR as a preoperative intervention, 1 of which observed a significant increase in muscle isometric endurance (P = .014), surface electromyography of the vastus medialis (P < .001), and muscle blood flow to the vastus lateralis at final follow-up (P < .001) as compared with patients undergoing sham BFR. Four studies investigated low-load BFR as a postoperative intervention, and they observed significant benefits in muscle hypertrophy, as measured by cross-sectional area; strength, as measured by extensor torque; and subjective outcomes, as measured by subjective knee pain during session, over traditional low-load resistance training (all P < .05). BFR occlusion periods ranged from 3 to 5 minutes, with rest periods ranging from 45 seconds to 3 minutes.

Conclusion:

This systematic review found evidence on the topic of BFR rehabilitation after ACLR to be sparse and heterogeneous likely because of the relatively recent onset of its popularity. While a few authors have demonstrated the potential strength and hypertrophy benefits of perioperative BFR, future investigations with standardized outcomes, long-term follow-up, and more robust sample sizes are required to draw more definitive conclusions.