Body position and cuff size influence lower limb arterial occlusion pressure and its predictors: implications for standardizing the pressure applied in training with blood flow restriction.

Background: Arterial occlusion pressure (AOP) is a relevant measurement for individualized prescription of exercise with blood flow restriction (BFRE). Therefore, it is important to consider factors that may influence this measure. Purpose: This study aimed to compare lower limb AOP (LL-AOP) measured with 11 cm (medium) and 18 cm (large) cuffs, in different body positions, and explore the predictors for each of the LL-AOP measurements performed. This information may be useful for future studies that seek to develop approaches to improve the standardization of pressure adopted in BFRE, including proposals for equations to estimate LL-AOP. Methods: This is a cross-sectional study. Fifty-one healthy volunteers (males, n = 25, females, n = 26; Age: 18-40 years old) underwent measurement of thigh circumference (TC), brachial blood pressure, followed by assessments of LL-AOP with medium and large cuffs in positions supine, sitting and standing positions. Results: The large cuff required less external pressure (mmHg) to elicit arterial occlusion in all three-body positions when compared to the medium cuff (p < 0.001). The LL-AOP was significantly lower in the supine position, regardless of the cuff used (p < 0.001). Systolic blood pressure was the main predictor of LL-AOP in the large cuff, while TC was the main predictor of LL-AOP with the medium cuff. Body position influenced strength of the LL-AOP predictors. Conclusion: Our results indicate that LL-AOP and its predictors are substantially influenced by body position and cuff width. Therefore, these variables should be considered when standardizing the pressure prescribed in BFRE.

Effect of High-Intensity Interval Exercise versus Continuous Low-Intensity Aerobic Exercise with Blood Flow Restriction on Psychophysiological Responses: A Randomized Crossover Study.

This study compared the effect of continuous low-intensity aerobic exercise with blood flow restriction (LI-AE-BFR) versus high-intensity interval exercise (HIIE), matching total external mechanical work between conditions, on perceptual (exertion, pain, affective and pleasure) and physiological responses (heart rate [HR], blood lactate [BL] and muscle fatigue). Ten healthy untrained men (25.6 ± 3.78 years old; 75.02 ± 12.02 kg; 172.2 ± 6.76 cm; 24.95 ± 3.16 kg/m²) completed three visits to the laboratory. In visit 1, anthropometry, blood pressure and peak running velocity on the treadmill were measured. In visits 2 and 3, participants were randomly assigned to HIIE or LI-AE-BFR, both in treadmill. HIIE consisted of 10 one-minute stimuli at 80% of peak running velocity interspersed with one-minute of passive recovery. LI-AE-BFR consisted of 20-minutes of continuous walking at 40% of peak running velocity with bilateral cuffs inflated to 50% of arterial occlusion pressure. BL and maximum isometric voluntary contraction (MIVC - fatigue measure) were measured pre- and immediately post-exercise. HR, rating of perceived exertion (RPE), and rating of perceived pain (RPP) were recorded after each stimulus in HIIE and every two minutes in LI-AE-BFR. Affective response to the session, pleasure, and future intention to exercise (FIE) were assessed 10 minutes after the intervention ended. Increases in BL concentrations were greater in HIIE (p = 0.028; r = 0.51). No effects time or condition were reported for MIVC. HR was higher in HIIE at all analyzed time points (p < 0.001; d = 3.1 to 5.2). RPE did not differ between conditions (p > 0.05), while average session RPP was higher in LI-AE-BFR (p = 0.036; r = 0.46). Affective positive response (p = 0.019; d = 0.9) and FIE (p = 0.013; d = 0.97) were significantly higher in HIIE. Therefore, HIIE elicited higher physiological stress, positive affective response, and intention to engage in future exercise bouts compared to LI-AE-BFR.

Acute Responses in Blood Flow Restriction Low-intensity Aerobic Training: A Meta-analysis.

The purpose was to determine the effect low-intensity training with blood flow restriction (LI-BFR) versus high-intensity aerobic training (HIT) on acute physiological and perceptual responses. The Cumulative Index to Nursing and Allied Health Literature, National Library of Medicine, Scopus, SPORTDiscus and Web of Science databases and the reference list of eligible studies were consulted to identify randomized experimental studies, published until July 4, 2022, that analyzed physiological or perceptual responses between LI-BFR versus HIT in healthy young individuals. Mean difference (MD) and standardized mean difference (SMD) were used as effect estimates and random effects models were applied in all analyses. Twelve studies were included in this review. During exercise sessions, HIT promoted higher values of heart rate (MD=28.9 bpm; p<0.00001; I 2 =79%), oxygen consumption (SMD=4.01; p<0.00001; I 2 =83%), ventilation (MD=48.03 l/min; p=0.0001; I 2 =97%), effort (SMD=1.54; p=0.003; I 2 =90%) and blood lactate (MD=3.85 mmol/L; p=0.002; I 2 =97%). Perception of pain/discomfort was lower in HIT (SMD=-1.71; p=0.04; I 2 =77.5%). In conclusion, LI-BFR promotes less pronounced physiological responses than HIT but with greater perception of pain.

Beneath the cuff: Often overlooked and under-reported blood flow restriction device features and their potential impact on practice-A review of the current state of the research.

Training with blood flow restriction (BFR) has been shown to be a useful technique to improve muscle hypertrophy, muscle strength and a host of other physiological benefits in both healthy and clinical populations using low intensities [20%-30% 1-repetition maximum (1RM) or <50% maximum oxygen uptake (VO2max)]. However, as BFR training is gaining popularity in both practice and research, there is a lack of awareness for potentially important design characteristics and features associated with BFR cuff application that may impact the acute and longitudinal responses to training as well as the safety profile of BFR exercise. While cuff width and cuff material have been somewhat addressed in the literature, other cuff design and features have received less attention. This manuscript highlights additional cuff design and features and hypothesizes on their potential to impact the response and safety profile of BFR. Features including the presence of autoregulation during exercise, the type of bladder system used, the shape of the cuff, the set pressure versus the interface pressure, and the bladder length will be addressed as these variables have the potential to alter the responses to BFR training. As more devices enter the marketplace for consumer purchase, investigations specifically looking at their impact is warranted. We propose numerous avenues for future research to help shape the practice of BFR that may ultimately enhance efficacy and safety using a variety of BFR technologies.

Cardiovascular and Perceptual Responses to Resistance Training with Practical Blood Flow Restriction Induced by a Non-Elastic Band vs. Pneumatic Cuff: A Crossover Randomized Study.

Our purpose in this study was to analyze perceptual and cardiovascular responses in low-load resistance training (RT) sessions associated with a fixed non-elastic band compressed to the proximal region of the arms (p-BFR) versus a pneumatic cuff inflated to a pressure of 150 mmHg (t-BFR). Participants (16 healthy trained men) were randomly assigned to two conditions of low-load RT (20% one repetition maximum [1RM]) with BFR (p-BFR or t-BFR). In both conditions, the participants performed five exercises (4 sets/30-15-15-15) for the upper-limbs, but in one of the conditions, the exercises were performed with a p-BFR induced by a non-elastic band, while in the other, the exercises were performed with a t-BFR using a device with similar width. The devices used to generate the BFR had similar widths (5 cm). Brachial blood pressure (bBP) and heart rate (HR) were measured before, after each exercise and after the experimental session (5-, 10-, 15-, and 20 min post-session). Rating of perceived exertion (RPE) and rating of pain perception (RPP) were reported after each exercise and 15 minutes post-session. HR increased during the training session in both conditions, with no differences between p-BFR and t-BFR. Neither intervention increased diastolic BP (DBP) during training, but there was a significant post-session reduction in DBP in the p-BFR, with no differences observed between conditions. There were no significant differences in RPE and RPP in the two training conditions, with both conditions associated with higher RPE and RPP at the end versus beginning of the experimental session. We conclude that when BFR device width and material are similar, low-load training with t-BFR and p-BFR promotes similar acute perceptual and cardiovascular responses in healthy trained men.

Relative age effects on speed trials in Brazilian athletics.

BACKGROUND: Relative age effect (RAE) is a concept related to the possible advantage that older athletes would have over younger ones within the same category. Although many studies have approached this subject in individual sports, there are few clippings by events within the sport. More detailed analyses are necessary for a better understanding of how RAE behaves in sports, especially in athletics, the subject of this study. The objective of this study was to analyze the RAE on speed in track and field events as a whole, separating the flat races from the hurdles races. METHODS: The Brazilian Ranking of Brazilian Athletics Confederation was used for data analysis, and the sample was composed of the 50 best-placed marks in the ranking of speed events in athletics in the categories Under(U)-16 and U-18 (female and male). Statistical analysis was calculated by chi-square, and the effect size was checked by Cramer's V. Likelihood-ratio test (L-Ratio) assessed the probability of the RAE occurring in the total sample and by age groups. RESULTS: In the total sample the results pointed to the emergence of RAE in males in both categories (U-16: p < 0.001; V: 0.13; L-Ratio: 3.64, U-18: p < 0.001; V: 0.13; L-Ratio: 3.80), whereas in females no such effect was found in any category (U-16: p = 0.6; V: 0.09; L-Ratio: 0.09, U-18: p = 0.6; V: 0.07; L-Ratio: 0.12). When the results were separated by type of event, there was only a RAE in the shallow event in the U-18 female category (p = 0.3; V: 0.11; L-Ratio: 8.72). CONCLUSION: The results allow us to conclude that there is a RAE in the speed trials of Brazilian athletics in the U16 and U18 categories for men, while this effect appears only in the shallow trials of the U18 category for women, indicating that the RAE has incidence when there is more participation and competition in the sport.

Acute Effect of Resistance Training With Blood Flow Restriction on Perceptual Responses: A Systematic Review and Meta-Analysis.

CONTEXT: Several studies have compared perceptual responses between resistance exercise with blood flow restriction and traditional resistance exercise (non-BFR). However, the results were contradictory. OBJECTIVES: To analyze the effect of RE+BFR versus non-BFR resistance exercise [low-load resistance exercise (LL-RE) or high-load resistance exercise (HL-RE)] on perceptual responses. DATA SOURCES: CINAHL, Cochrane Library, PubMed®, Scopus, SPORTDiscus, and Web of Science were searched through August 28, 2021, and again on August 25, 2022. STUDY SELECTION: Studies comparing the effect of RE+BFR versus non-BFR resistance exercise on rate of perceived exertion (RPE) and muscle pain/discomfort were considered. Meta-analyses were conducted using the random effects model. STUDY DESIGN: Systematic review and meta-analysis. LEVEL OF EVIDENCE: Level 2. DATA EXTRACTION: All data were reviewed and extracted independently by 2 reviewers. Disagreements were resolved by a third reviewer. RESULTS: Thirty studies were included in this review. In a fixed repetition scheme, the RPE [standardized mean difference (SMD) = 1.04; P < 0.01] and discomfort (SMD = 1.10; P < 0.01) were higher in RE+BFR than in non-BFR LL-RE, but similar in sets to voluntary failure. There were no significant differences in RPE in the comparisons between RE+BFR and non-BFR HL-RE; after sensitivity analyses, it was found that the RPE was higher in non-BFR HL-RE in a fixed repetition scheme. In sets to voluntary failure, discomfort was higher in RE+BFR versus non-BFR HL-RE (SMD = 0.95; P < 0. 01); however, in a fixed scheme, the results were similar. CONCLUSION: In sets to voluntary failure, RPE is similar between RE+BFR and non-BFR exercise. In fixed repetition schemes, RE+BFR seems to promote higher RPE than non-BFR LL-RE and less than HL-RE. In sets to failure, discomfort appears to be similar between LL-RE with and without BFR; however, RE+BFR appears to promote greater discomfort than HL-RE. In fixed repetition schemes, the discomfort appears to be no different between RE+BFR and HL-RE, but is lower in non-BFR LL-RE.

Physiological adaptations and myocellular stress in short-term, high-frequency blood flow restriction training: A scoping review.

BACKGROUND: High frequency (1-2 times per day) low-intensity blood flow restriction (BFR) training has been recommended as a prescription approach for short durations of time to maximize relevant physiological adaptations. However, some studies demonstrate negative physiological changes after short periods of high-frequency BFR training, including prolonged strength decline and muscle fiber atrophy. OBJECTIVES: To provide a comprehensive overview of short-term, high-frequency blood flow restriction training, including main adaptations, myocellular stress, limitations in the literature, and future perspectives. METHODS: A systematic search of electronic databases (Scopus, PubMed®, and Web of Science) was performed from the earliest record to April 23, 2022. Two independent reviewers selected experimental studies that analyzed physical training protocols (aerobic or resistance) of high weekly frequency (>4 days/week) and short durations (≤3 weeks). RESULTS: In total, 22 studies were included in this review. The samples were composed exclusively of young predominantly male individuals. Muscle strength and hypertrophy were the main outcomes analyzed in the studies. In general, studies have demonstrated increases in strength and muscle size after short term (1-3 weeks), high-frequency low-intensity BFR training, non-failure, but not after control conditions (non-BFR; equalized training volume). Under failure conditions, some studies have demonstrated strength decline and muscle fiber atrophy after BFR conditions, accompanying increases in muscle damage markers. Significant limitations exist in the current HF-BFR literature due to large heterogeneities in methodologies. CONCLUSION: The synthesis presented indicates that short-term, high-frequency BFR training programs can generate significant neuromuscular adaptations. However, in resistance training to failure, strength declines and muscle fiber atrophy were reported. Currently, there are no studies analyzing low-frequency vs. high-frequency in short-term BFR training. Comparisons between resistance exercises of similar intensities (e.g., combined effort) are lacking, limiting conclusions on whether the effect is a product of proximity to failure or a specific effect of BFR.

Effects of high-intensity interval training in combination with detraining on mental health in women with polycystic ovary syndrome: A randomized controlled trial.

This study aimed to investigate the effects of high-intensity interval training (HIIT) and detraining on the quality of life and mental health of 23 women with polycystic ovary syndrome (PCOS). Participants were randomly assigned to the HIIT group (n = 12) [26.0 ± 3.92] and the control group (n = 11) [26.6 ± 4.68]. HIIT sessions comprised 40-60 min, 3 days a week for 12 weeks, followed by detraining for 30 days. We assessed the quality of life using the Short Form Health Survey (SF-36) and mental health by the Depression, Anxiety, and Stress Scale (DASS-21), and we compared group changes on these variables at three time points: 1) at baseline, 2) after 12 weeks of HIIT (or no training), and 3) after 30 days of detraining (or no training). The participants were classified as overweight and had a high percentage of body fat (41.5%) and irregular menstrual cycles (amenorrhea) (66.7%). Throughout training, participants in the HIIT group reported improvements in domains of the quality of life: functional capacity (M = 80.4 ± 3.4 vs. M = 87.0 ± 3.1), physical role functioning (M = 72.5 ± 9.4 vs. M = 81.8 ± 9.7), and general health perception (M = 48.6 ± 4.6 vs. M = 69.0 ± 5.8). Regarding anxiety symptoms (M = 6.4 ± 1.6 vs. M = 3.7 ± 0.7) and depression symptoms (M = 6.7 ± 1.6 vs. M = 3.8 ± 0.9), those reduced significantly after HIIT. After a 30-day detraining period, there was an increase in the significant change in the quality of life; however, domains of mental health showed instability. In summary, the HIIT program promoted improvements in the quality of life and mental health in women with PCOS. The 30 days of detraining changed the benefits in the quality of life and stability in the changes in mental health domains.

Impact of social isolation on the level of physical activity in young Brazilian athletes caused by COVID-19.

BACKGROUND: Social detachment to prevent the spread of the COVID-19 pandemics in the year 2020 can significantly contribute to the physical inactivity of citizens worldwide. The study aimed to analyze the level of physical activity by identifying the training methods used during the social isolation resulting from the COVID-19 pandemic. METHODS: Sixty-eight Brazilian athletes (both sexes, 14.7±1.68 years) answered and adapted the International Physical Activity Questionnaire (I-PAQ) through an online platform. Participants were asked to report their level of physical activity before and during the period of social distance. RESULTS: According to our results, 67.7% of the interviewed athletes said they were able to adapt their sports training to the isolation environment under the guidance of a distance physical education professional. Only 4.38% of the sample was not training under such supervision and, therefore, inactive. Among the activities performed in the isolation environment, calisthenics was the primary practice (effect size: ƒ2=0.50, P<0.0001) and the sport practiced at home was the secondary practice (effect size: ƒ2=0.27, P=0.004). During the pandemic, the training hours of athletes reduced significantly from ~3h to ~1h per day (effect size: 1.74, P<0.0001), as well as the perceived intensity decreased from "high" to "moderate" (effect size: 1.38, P<0.0001). The weekly training frequency decreased from ~6 to 7 days to ~3 to 5 days (effect size: 0.40, P=0.03). CONCLUSIONS: Despite the social distance and the reduced pace of training, the young Brazilian athletes analyzed managed to remain physically active during the COVID-19 pandemic.

Myoelectric Activity and Fatigue in Low-Load Resistance Exercise With Different Pressure of Blood Flow Restriction: A Systematic Review and Meta-Analysis.

Background: Low-load resistance exercise (LL-RE) with blood flow restriction (BFR) promotes increased metabolic response and fatigue, as well as more pronounced myoelectric activity than traditional LL-RE. Some studies have shown that the relative pressure applied during exercise may have an effect on these variables, but existing evidence is contradictory. Purpose: The aim of this study was to systematically review and pool the available evidence on the differences in neuromuscular and metabolic responses at LL-RE with different pressure of BFR. Methods: The systematic review and meta-analysis was reported according to PRISMA items. Searches were performed in the following databases: CINAHL, PubMed, Scopus, SPORTDiscus and Web of Science, until June 15, 2021. Randomized or non-randomized experimental studies that analyzed LL-RE, associated with at least two relative BFR pressures [arterial occlusion pressure (AOP)%], on myoelectric activity, fatigue, or metabolic responses were included. Random-effects meta-analyses were performed for MVC torque (fatigue measure) and myoelectric activity. The quality of evidence was assessed using the PEDro scale. Results: Ten studies were included, all of moderate to high methodological quality. For MVC torque, there were no differences in the comparisons between exercise with 40-50% vs. 80-90% AOP. When analyzing the meta-analysis data, the results indicated differences in comparisons in exercise with 15-20% 1 repetition maximum (1RM), with higher restriction pressure evoking greater MVC torque decline (4 interventions, 73 participants; MD = -5.05 Nm [95%CI = -8.09; -2.01], p = 0.001, I 2 = 0%). For myoelectric activity, meta-analyses indicated a difference between exercise with 40% vs. 60% AOP (3 interventions, 38 participants; SMD = 0.47 [95%CI = 0.02; 0.93], p = 0.04, I2 = 0%), with higher pressure of restriction causing greater myoelectric activity. This result was not identified in the comparisons between 40% vs. 80% AOP. In analysis of studies that adopted pre-defined repetition schemes, differences were found (4 interventions, 52 participants; SMD = 0.58 [95%CI = 0.11; 1.05], p = 0.02, I 2 = 27%). Conclusion: The BFR pressure applied during the LL-RE may affect the magnitude of muscle fatigue and excitability when loads between 15 and 20% of 1RM and predefined repetition protocols (not failure) are prescribed, respectively. Systematic Review Registration: [http://www.crd.york.ac.uk/prospero], identifier [CRD42021229345].

Performance Prediction Equation for 2000 m Youth Indoor Rowing Using a 100 m Maximal Test.

BACKGROUND: The exhaustive series of tests undergone by young athletes of Olympic rowing prior to important competitions imply loads of physical stress that can ultimately impact on mood and motivation, with negative consequences for their training and performance. Thus, it is necessary to develop a tool that uses only the performance of short distances but is highly predictive, offering a time expectancy with high reliability. Such a test must use variables that are easy to collect with high practical applicability in the daily routine of coaches. OBJECTIVE: The objective of the present study was to develop a mathematical model capable of predicting 2000 m rowing performance from a maximum effort 100 m indoor rowing ergometer (IRE) test in young rowers. METHODS: The sample consisted of 12 male rowing athletes in the junior category (15.9 ± 1.0 years). A 100 m time trial was performed on the IRE, followed by a 2000 m time trial 24-h later. RESULTS: The 2000 m mathematical model to predict performance in minutes based on the maximum 100 m test demonstrated a high correlation (r = 0.734; p = 0.006), strong reliability index (ICC: 0.978; IC95%: [0.960; 0.980]; p = 0.001) and was within usable agreement limits (Bland -Altman Agreement: -0.60 to 0.60; 95% CI [-0.65; 0.67]). CONCLUSION: The mathematical model developed to predict 2000 m performance is effective and has a statistically significant reliability index while being easy to implement with low cost.

Effect of resistance training with blood flow restriction on muscle damage markers in adults: A systematic review.

BACKGROUND: The purpose of this review was to systematically analyze the evidence regarding the occurrence of muscle damage (changes in muscle damage markers) after resistance training with blood flow restriction sessions. MATERIALS AND METHODS: This systematic review was conducted in accordance with the PRISMA recommendations. Two researchers independently and blindly searched the following electronic databases: PubMed, Scopus, Web of Science, CINAHL, LILACS and SPORTdicus. Randomized and non-randomized clinical trials which analyzed the effect of resistance training with blood flow restriction on muscle damage markers in humans were included. The risk of bias assessment was performed by two blinded and independent researchers using the RoB2 tool. RESULTS: A total of 21 studies involving 352 healthy participants (men, n = 301; women, n = 51) were eligible for this review. The samples in 66.6% of the studies (n = 14) were composed of untrained individuals. All included studies analyzed muscle damage using indirect markers. Most studies had more than one muscle damage marker and Delayed Onset Muscle Soreness was the measure most frequently used. The results for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions were contrasting, and the use of a pre-defined repetition scheme versus muscle failure seems to be the determining point for this divergence, mainly in untrained individuals. CONCLUSIONS: In summary, the use of sets until failure is seen to be determinant for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions, especially in individuals not used to resistance exercise. TRIAL REGISTRATION: Register number: PROSPERO number: CRD42020177119.

Application and side effects of blood flow restriction technique: A cross-sectional questionnaire survey of professionals.

ABSTRACT: The physiological benefits of applying blood flow restriction (BFR) in isolation or in the presence of physical exercise have been widely documented in the scientific literature. Most investigations carried out under controlled laboratory conditions have found the technique to be safe. However, few studies have analyzed the use of the technique in clinical settings.To analyze how the BFR technique has been applied by professionals working in the clinical area and the prevalence of side effects (SEs) resulting from the use of this technique.This is a cross-sectional study. A total of 136 Brazilian professionals who perform some function related to physical rehabilitation, sports science, or physical conditioning participated in this study. Participants answered a self-administered online questionnaire consisting of 21 questions related to the professional profile and methodological aspects and SEs of the BFR technique.Professionals reported applying the BFR technique on individuals from different age groups from youth (≤18 years; 3.5%) to older adults (60-80 years; 30.7%), but mainly on people within the age group of 20 to 29 years (74.6%). A total of 99.1% of the professionals coupled the BFR technique with resistance exercise. Their main goals were muscle hypertrophy and physical rehabilitation. The majority (60.9%) of interviewees reported using BFR in durations of less than 5 minutes and the pressure used was mainly determined through the values of brachial blood pressure and arterial occlusion. Moreover, 92% of professionals declared observing at least 1 SE resulting from the BFR technique. Most professionals observed tingling (71.2%) and delayed onset of muscle soreness (55.8%). Rhabdomyolysis, fainting, and subcutaneous hemorrhaging were reported less frequently (1.9%, 3.8%, and 4.8%, respectively).Our findings indicate that the prescription of blood flow restriction technique results in minimal serious side effects when it is done in a proper clinical environment and follows the proposed recommendations found in relevant scientific literature.