Blood flow restriction augments the cross-education effect of isometric handgrip training.

INTRODUCTION: The application of blood flow restriction (BFR) to low-intensity exercise may be able to increase strength not only in the trained limb but also in the homologous untrained limb. Whether this effect is repeatable and how that change compares to that observed with higher intensity exercise is unknown. PURPOSE: Examine whether low-intensity training with BFR enhances the cross-education of strength compared to exercise without BFR and maximal efforts. METHODS: A total of 179 participants completed the 6-week study, with 135 individuals performing isometric handgrip training over 18 sessions. Participants were randomly assigned to one of four groups: 1) low-intensity (4 × 2 min of 30% MVC; LI, n = 47), 2) low-intensity with blood flow restriction (LI + 50% arterial occlusion pressure; LI-BFR, n = 41), 3) maximal effort (4 × 5 s of 100% MVC; MAX, n = 47), and 4) non-exercise control (CON, n = 44). RESULTS: LI-BFR was the only group that observed a cross-education in strength (CON: 0.64 SD 2.9 kg, LI: 0.95 SD 3.6 kg, BFR-LI: 2.7 SD 3.3 kg, MAX: 0.80 SD 3.1 kg). In the trained hand, MAX observed the greatest change in strength (4.8 SD 3.3 kg) followed by LI-BFR (2.8 SD 4.0 kg). LI was not different from CON. Muscle thickness did not change in the untrained arm, but ulna muscle thickness was increased within the trained arm of the LI-BFR group (0.06 SD 0.11 cm). CONCLUSION: Incorporating BFR into low-intensity isometric training led to a cross-education effect on strength that was greater than all other groups (including high-intensity training).

The effects of branched-chain amino acids on muscle protein synthesis, muscle protein breakdown and associated molecular signalling responses in humans: an update.

Branched-chain amino acids (BCAA: leucine, isoleucine and valine) are three of the nine indispensable amino acids, and are frequently consumed as a dietary supplement by athletes and recreationally active individuals alike. The popularity of BCAA supplements is largely predicated on the notion that they can stimulate rates of muscle protein synthesis (MPS) and suppress rates of muscle protein breakdown (MPB), the combination of which promotes a net anabolic response in skeletal muscle. To date, several studies have shown that BCAA (particularly leucine) increase the phosphorylation status of key proteins within the mechanistic target of rapamycin (mTOR) signalling pathway involved in the regulation of translation initiation in human muscle. Early research in humans demonstrated that BCAA provision reduced indices of whole-body protein breakdown and MPB; however, there was no stimulatory effect of BCAA on MPS. In contrast, recent work has demonstrated that BCAA intake can stimulate postprandial MPS rates at rest and can further increase MPS rates during recovery after a bout of resistance exercise. The purpose of this evidence-based narrative review is to critically appraise the available research pertaining to studies examining the effects of BCAA on MPS, MPB and associated molecular signalling responses in humans. Overall, BCAA can activate molecular pathways that regulate translation initiation, reduce indices of whole-body and MPB, and transiently stimulate MPS rates. However, the stimulatory effect of BCAA on MPS rates is less than the response observed following ingestion of a complete protein source providing the full complement of indispensable amino acids.

Unilateral high-load resistance training influences strength changes in the contralateral arm undergoing low-load training.

OBJECTIVES: Within-subject training models have become common within the exercise literature. However, it is currently unknown if training one arm with a high load would impact muscle size and strength of the opposing arm training with a low load. DESIGN: Parallel group. METHODS: 116 participants were randomized to one of three groups that completed 6-weeks (18 sessions) of elbow flexion exercise. Group 1 trained their dominant arm only, beginning with a one-repetition maximum test (≤5 attempts), followed by four sets of exercise using a weight equivalent to 8-12 repetition maximum. Group 2 completed the same training as Group 1 in their dominant arm, while the non-dominant arm completed four sets of low-load exercise (30-40 repetition maximum). Group 3 trained their non-dominant arm only, performing the same low-load exercise as Group 2. Participants were compared for changes in muscle thickness and elbow flexion one-repetition maximum. RESULTS: The greatest changes in non-dominant strength were present in Groups 1 (Δ 1.5 kg; untrained arm) and 2 (Δ1.1 kg; low-load arm with high load on opposite arm), compared to Group 3 (Δ 0.3 kg; low-load only). Only the arms being directly trained observed changes in muscle thickness (≈Δ 0.25 cm depending on site). CONCLUSIONS: Within-subject training models are potentially problematic when investigating changes in strength (though not muscle growth). This is based on the finding that the untrained limb of Group 1 saw similar changes in strength as the non-dominant limb of Group 2 which were both greater than the low-load training limb of Group 3.

Improved interference control after exercise with blood flow restriction and cooling is associated with but not mediated by increased lactate.

BACKGROUND: To evaluate the effects of recumbent sprint interval exercise with and without blood flow restriction and body cooling on interference control and whether the changes in interference control can be explained by the changes in blood lactate. METHODS: 85 participants (22 SD 3 years old) completed 1 familiarization visit and then 5 experimental visits in a randomized order: exercise only (Ex), exercise with blood flow restriction (ExB), exercise with cooling (ExC), and exercise with blood flow restriction and cooling (ExBC), and non-exercise control (Con). Measurements of blood lactate and the Stroop Color Word Test were performed before and after exercise. Each bout began with a 15-minute low-moderate intensity warm-up, followed by five 20-second "all out" sprints separated by 40 s of active recovery. Bayes Factors (BF10) quantified evidence for or against the null hypothesis. Within-subject mediation analysis quantified the indirect effect of changes in blood lactate (mediator) on the change in interference control (each exercise condition vs. Con). RESULTS: Bayesian pairwise comparisons found that only ExC [σ: -0.37 (-0.59, -0.15)] and ExBC [σ: -0.3 (-0.53, -0.09)] produced changes in incongruent reaction time different from that of Con. There was also evidence that all exercise conditions increased blood lactate (BF10 = 8.65e+29 - 1.9e+32) and improved congruent reaction time (BF10 = 4.01 - 15.371) compared to that of Con. There was no evidence to show that changes in lactate mediated the change in incongruent reaction time. CONCLUSIONS: Both exercise with body cooling and when body cooling was combined with blood flow restriction presented favorable changes in incongruent reaction time (a marker of interference control), which might not be explained by the changes in systemic blood lactate concentration.

Evaluation of sex-based differences in resistance exercise training-induced changes in muscle mass, strength, and physical performance in healthy older (≥60 y) adults: A systematic review and meta-analysis.

The objective of this systematic review and meta-analysis was to determine if there are sex-based differences in adaptations to resistance exercise training in healthy older adults. Following the screening process, data from 36 studies comparing older males and females (602 males; 703 females; ≥60 years of age) for changes in skeletal muscle size, muscle strength, and/or physical performance following the same resistance exercise training intervention were extracted. Mean study quality was 16/29 (modified Downs and Black checklist), considered moderate quality. Changes in absolute upper-body (Effect Size [ES] = 0.81 [95% CI 0.54, 1.09], P < 0.001), and lower-body (ES = 0.40 [95% CI 0.24, 0.56], P < 0.001) strength were greater in older males than females. Alternatively, changes in relative upper-body (ES = -0.46 [95% CI -0.77, -0.14], P < 0.01), and lower-body (ES = -0.24 [95% CI -0.42, -0.06], P < 0.01) strength were greater in older females than males. Changes in absolute, but not relative, whole-body fat-free mass (ES = 0.18 [95% CI 0.04, 0.33], P < 0.05) were greater in older males than females. There were no sex-based differences for absolute or relative changes in limb muscle size, muscle fiber size, or physical performance.

Effect of Increased Pressure Pain Threshold on Resistance Exercise Performance With Blood Flow Restriction.

ABSTRACT: Kataoka, R, Song, JS, Bell, ZW, Wong, V, Spitz, RW, Yamada, Y, and Loenneke, JP. Effect of increased pressure pain threshold on resistance exercise performance with blood flow restriction. J Strength Cond Res 37(6): 1204-1210, 2023-This study aimed to examine whether increasing pressure pain threshold (PPT) through isometric handgrip exercise (HG) affects the number of repetitions completed and discomfort with knee extension exercise (KE) with blood flow restriction (BFR), and examine whether performing additional exercise leads to a further increase in PPT. Forty-one participants completed 2 trials: rest followed by low-load KE with BFR at 80% of resting arterial occlusion pressure (Rest + KE BFR) and low-intensity (30% of maximal strength) HG exercise followed by KE with BFR (HG + KE BFR). Pressure pain threshold was measured before and after exercise at the forearm and tibialis anterior. Results are presented as median difference (95% credible interval). Pressure pain threshold increased at the forearm (Bayes factor [BF 10 ]: 5.2 × 10 7 ) and tibialis anterior (BF 10 : 1.5 × 10 6 ) after HG exercise. However, this did not lead to greater repetitions being completed with BFR exercise (0.2 [-0.1, 0.6] repetitions, BF 10 : 0.07). Pressure pain threshold after BFR exercise was not augmented over that observed with HG exercise (0.02 [-0.15, 0.2] kg·cm -2 , BF 10 : 0.175) at the forearm. More data are needed in the lower body to determine which model best fits the data (BF 10 : 0.84). Discomfort with BFR exercise was not different between conditions (1.0 [-2.3, 4.4] arbitrary units, BF 10 : 0.10). The pain-reducing effect of prior exercise did not change the repetitions completed with BFR exercise, suggesting that the change in PPT may not have been great enough to alter performance. Performing additional exercise did not elicit further increases in PPT nor was perceived discomfort to BFR exercise altered by changes in PPT.

Does muscle growth mediate changes in a nonspecific strength task?

The purpose of this study was to determine if muscle growth mediates increases in a strength task which was not directly trained. One hundred fifty-one participants were randomized into control, one-repetition maximum training (1RM-TRAIN), or traditional training (TRAD-TRAIN). Training groups performed isotonic elbow flexion 3x/week for 6 weeks. Anterior muscle thickness at 50%, 60% and 70% upper arm length, and maximal isokinetic torque at 60°/sec were assessed pre- and post-training. Change-score mediation models (adjusted for sex, pre-muscle thickness, and pre-strength) were constructed for each muscle thickness site. The effects of each training group were evaluated relative to the control. Data is presented as coefficient (95% CI). There were no significant relative direct effects on nonspecific strength for either training group outside of the 60% model (1.7 [0.13, 3.27] Nm). The relative effect of 1RM-TRAIN on muscle thickness was greater in 60% (0.09 [0.01, 0.17] cm) and 70% (0.09 [0.00, 0.17] cm) models; while TRAD-TRAIN was greater in all three: (50% = 0.24 [0.15, 0.32]; 60% = 0.24 [0.16, 0.33]; 70% = 0.22 [0.14, 0.31] cm). The effect of muscle thickness on nonspecific strength was only significant for the 60% (-3.06 [-5.7, -0.35] Nm) model. The relative indirect effect on nonspecific strength was not significant for the 1RM-TRAIN or TRAD-TRAIN. Similar to previous findings on specific strength, we did not find evidence for a mediating effect of muscle growth on training induced increases in nonspecific strength. The importance of muscle growth for changes in nonspecifically trained strength may need to be reconsidered.

Sex segregation in strength sports: Do equal-sized muscles express the same levels of strength between sexes?

OBJECTIVES: Concerns have been raised against the current two-sex binary category in sports competitions. The thesis states that if males and females were separated based on muscle size, it would negate the strength advantage between the sexes. We tested the possible sex differences in various strength outcomes when pair-matched for muscle thickness. METHODS: A total of 16 different data sets (n = 963) were assessed to pair-match females with males who had a muscle thickness value within 2%. We further compared the competition performances of the smallest male weight class within the International Powerlifting Federation (IPF) to different weight classes in females. RESULTS: Overall, 76%-88% of the strength assessments were greater in males than females with pair-matched muscle thickness, regardless of contraction types (i.e., isotonic, isometric, isokinetic). Additionally, males in the lightest weight division in the IPF largely outperformed females in heavier weight divisions. CONCLUSIONS: Our results would suggest that segregation based on muscle mass or surrogates of muscle mass (e.g., lean body mass) might not be an appropriate classification to create fair competition within strength sports. This is not to refute the concept of the desegregation of the two-sex binary category but to present data that raises important concerns about the potential sex-based differences in strength performance.

Quantifying the Generality of Strength Adaptation: A Meta-Analysis.

BACKGROUND: Isotonic exercise is the most common mode of strength training. Isotonic strength is often measured in the movement that was exercised, but isometric and isokinetic movements are also commonly used to quantify changes in muscular strength. Previous research suggests that increasing strength in one movement may not lead to an increase in strength in a different movement. Quantifying the increase in strength in a movement not trained may be important for understanding strength training adaptations and making recommendations for resistance exercise and rehabilitation programs. OBJECTIVE: To quantify changes in non-specific strength relative to a control. DESIGN: A systematic review and random effects meta-analysis was conducted investigating the effects of isotonic strength training on isotonic and isokinetic/isometric strength. SEARCH AND INCLUSION: This systematic review was conducted in Google scholar, PubMed, Academic Search Premier, and MENDELEY. To be included in this review paper the article needed to meet the following criteria: (1) report sufficient data for our variables of interest (i.e., changes in isotonic strength and changes in isokinetic or isometric strength); (2) include a time-matched non-exercise control; (3) be written in English; (4) include healthy human participants over the age of 18 years; (5) the participants had to train and test isotonically; (6) the participants had to be tested isokinetically or isometrically on a device different from that they trained on; (7) the non-specific strength task had to test a muscle involved in the training (i.e., could not have trained chest press and test handgrip strength); and (8) the control group and the experimental group had to perform the same number of strength tests. RESULTS: We completed two separate searches. In the original search a total of 880 papers were screened and nine papers met the inclusion criteria. In the secondary search a total of 2594 papers were screened and three additional papers were added (total of 12 studies). The overall effect of resistance training on changes in strength within a movement that was not directly trained was 0.8 (Cohen's d) with a standard error of 0.286. This overall effect was significant (t = 2.821, p = 0.01) and the 95% confidence interval (CI) is 0.22-1.4. The overall effect of resistance training on strength changes within a movement that was directly trained was 1.84 (Cohen's d) with a standard error of 0.296. This overall effect was significant (t = 6.221, p < 0.001) and the 95% CI is 1.23-2.4. CONCLUSION: The results of our meta-analysis suggest that strength increases in both the specific and non-specific strength tests. However, the smaller effect size associated with non-specific strength suggests that it will be difficult for a single study to meaningfully investigate the transfer of strength training adaptions.

The Hypoalgesic Effect of Low-Load Exercise to Failure Is Not Augmented by Blood Flow Restriction.

Purpose: To 1) examine whether blood flow restriction would provide an additional exercise-induced hypoalgesic response at an upper and lower limb when it is incorporated with low-load resistance exercise until failure, and 2) examine if increases in blood pressure and discomfort, with blood flow restricted exercise, would mediate the exercise-induced hypoalgesia over exercise without blood flow restriction. Methods: Forty healthy young participants completed two trials: four sets of unilateral knee extension exercise to failure at 30% of one-repetition maximum, with and without blood flow restriction. Pressure pain thresholds were assessed before (twice) and 5-min post exercise at an upper and lower limb. Blood pressure and discomfort ratings were recorded to examine mediating effects on exercise-induced hypoalgesia with blood flow restricted exercise. Results: Pressure pain threshold increased following both exercise conditions compared to a control, without any differences between exercise conditions at the upper (exercise conditions vs. control: ~0.37 kg/cm2) and lower (exercise conditions vs. control: ~0.60 kg/cm2) limb. The total number of repetitions was lower for exercise with blood flow restriction compared to exercise alone [median difference (95% credible interval) of -27.0 (-29.8, -24.4) repetitions]. There were no mediating effects of changes in blood pressure, nor changes in discomfort, for the changes in pressure pain threshold at either the upper or lower limb. Conclusion: The addition of blood flow restriction to low-load exercise induces a similar hypoalgesic response to that of non-blood flow restricted exercise, with a fewer number of repetitions.

Can Individuals Be Taught to Sense the Degree of Vascular Occlusion? A Comparison of Methods and Implications for Practical Blood Flow Restriction.

ABSTRACT: Bell, ZW, Spitz, RW, Wong, V, Yamada, Y, Song, JS, Abe, T, and Loenneke, JP. Can individuals be taught to sense the degree of vascular occlusion? A comparison of methods and implications for practical blood flow restriction. J Strength Cond Res 36(12): 3359-3365, 2022-The study objective was to determine whether subjects could be conditioned to a relative blood flow restriction pressure in the lower body and compare 2 separate conditioning methods (unconstrained vs. constrained). Thirty-five subjects completed 4 visits, involving measurements for arterial occlusion and pressure estimations at 5 minutes and 24 hours after conditioning. The constrained method involved applying 40% of measured arterial occlusion 11 times, along with 10% above and below this pressure. The unconstrained method was time-matched, involving a series of inflations to 40% arterial occlusion for 12 seconds and then deflated for 22 seconds. Data are presented as mean differences (95% credible interval) unless otherwise noted. The absolute error between conditioning methods was found to be similar at 5 minutes (-1.1 [-5.9, 3.7] mm Hg) and 24 hours (-2.4 [-7, 2.2] mm Hg) after conditioning. The constant error differed between methods at 5 minutes [-8.2 (-14.4, -1.9) mm Hg] but was similar at 24 hours (-2.5 [-8.5, 3.6] mm Hg; H0: 0.680; H1: 0.068; and H2: 0.252) after conditioning. The bias and 95% limits of agreement for the unconstrained method were -3.9 (-33.8, 25.9) mm Hg at 5 minutes and -2.9 (-32, 26.1) mm Hg at 24 hours. The agreement for the constrained method was 4.2 (-28, 36.5) mm Hg at 5 minutes and -0.54 (-37.3, 36.2) mm Hg at 24 hours. Conditioning methods produced similar levels of absolute error, indicating that either method may offer a viable means of pressure application. Most estimates were between 20 and 60% of arterial occlusion pressure. Additional conditioning sessions may be needed to narrow this range at the individual level.

Training-induced hypoalgesia and its potential underlying mechanisms.

It is well-established that a single bout of exercise can reduce pain sensitivity (i.e., exercise-induced hypoalgesia) in healthy individuals. However, exercise-induced hypoalgesia is often impaired in individuals with chronic pain. This might suggest that repeated bouts of exercise (i.e., exercise training) are needed in order to induce a reduction in pain sensitivity (i.e., training-induced hypoalgesia) among individuals with chronic pain, given that a single bout of exercise seems to be insufficient to alter pain. However, the effect of repeated bouts of exercise on pain sensitivity and its underlying mechanisms remain poorly understood. Therefore, the purpose of this review was to provide an overview of the existing literature on training-induced hypoalgesia, as well as discuss potential mechanisms of training-induced hypoalgesia and offer considerations for future research. Existing literature suggests that training interventions may induce hypoalgesic adaptations potentially driven by central nervous system and immune system factors. However, the limited number of randomized controlled trials available, along with the lack of understanding of underlying mechanisms, provides a rationale for future research.

Blood flow restriction maintains blood pressure upon head-up tilt.

BACKGROUND: Orthostatic intolerance occurs in some astronauts following space flight. Although orthostatic blood pressure responses should normalize in the weeks following the return to Earth, there may be situations where an immediate short-term solution is necessary (e.g., emergency evacuation). PURPOSE: The purpose of this study was to examine different levels of blood flow restriction on changes in blood pressure and heart rate when transitioning from supine to a head-up tilt and determine whether this change differs based on sex. METHODS: Eighty-nine participants (45 men, 44 women) completed the three visits with different pressures (Sham, Moderate, and High) in a randomized order. Cuffs were placed on the most proximal area of the thighs. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and eight more times separated by 45 seconds. RESULTS: Data are presented as mean (SD). The change in systolic (High > Moderate > Sham) [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4) mmHg, and Moderate vs Sham: 2.4 (8.4) mmHg] and diastolic pressure (High > Moderate = Sham) [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3) mmHg] differed across applied pressures. The change in heart rate was initially greatest in the sham-pressure but increased the greatest in the high-pressure condition by the end of the head-up tilt period. Additionally, there was no influence of sex. CONCLUSION: Blood flow restriction applied in this study increased blood pressure in a pressure-dependent manner upon head-up tilt.

Muscle thickness assessment of the forearm via ultrasonography: is experience level important?

It is suggested that experience is needed in order to capture valid estimates of muscle size with ultrasound. However, it is unknown whether there is a large degree of skill needed to analyze the images once they are captured.Objective.To determine if less experienced raters could accurately analyze ultrasound images of the forearm by comparing their estimates with those of a very experienced ultrasonographer (criterion).Approach.50 muscle thickness images were captured by one experienced ultrasonographer (also Rater 1). Those images were saved and were then measured by four raters with different levels of experience. The rater who captured the images was very experienced (criterion), the second rater was also experienced and provided 5 minutes of instruction for Rater 3 (minimal experience) and Rater 4 (no experience). Test-retest reliability was also determined for Rater 3 and 4.Main Results.The average muscle thickness value for the criterion was 3.73 cm. The constant error for Rater 2, 3, and 4 was -0.003 (0.02) cm (p= 0.362), -0.07 (0.04) cm (p< 0.001), and 0.02 (0.09) cm (p= 0.132), respectively. The SD for Rater 4 was greater, resulting in wider limits of agreement compared to Rater 2 and 3. Absolute error was 0.01 cm for Rater 2, whilst it was 0.07 cm and 0.03 cm for the two inexperienced raters (Rater 3 and 4). The error for Rater 3 was systematic and post-hoc assessment found that this rater was using a different border than the other three raters (but consistent across time). For the test-retest reliability, the minimal difference for Rater 3 was 0.08 cm (relative minimal difference of 2%) and 0.17 cm (relative minimal difference of 4%) for Rater 4.Significance.Less experienced raters were able to accurately and reliably analyze already captured muscle thickness images of the forearm with low absolute errors.

The impact of isometric handgrip exercise and training on health-related factors: A review.

Isometric handgrip exercise has been suggested to promote some health-related factors (e.g., lowering blood pressure). However, there is a need to evaluate whether this type of exercise can be included as an option to elicit these health-related outcomes. The purpose of the article was to systematically review the acute and chronic effects of isometric handgrip exercise on resting blood pressure, pain sensation, cognitive function and blood lipids and lipoproteins. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 89 studies met our inclusion criteria. Most randomized controlled trials (17/26) reported reductions in resting blood pressure (mostly systolic blood pressure) following isometric handgrip training. There were inconsistent results in isometric handgrip exercise-induced hypotension (i.e., acute response). There was convincing evidence observed in randomized controlled trials (4/6) for isometric handgrip exercise-induced hypoalgesia. Some randomized controlled trials (2/2) supported an improvement in memory performance, but not interference control (0/2), after a session of isometric handgrip exercise. None of the included studies found any effects of isometric handgrip training on blood lipids and lipoproteins. Isometric handgrip exercise appears to be an effective method to improve certain health-related factors. The acute reductions in pain and blood pressure may share a similar central mechanism. However, training-induced reductions in resting blood pressure may be driven by changes in the periphery. Additional work is needed to better understand if (and to what extent) isometric handgrip exercise (or training) influences cognitive function and blood lipids and lipoproteins.

Comparisons of calorie restriction and structured exercise on reductions in visceral and abdominal subcutaneous adipose tissue: a systematic review.

Exercise and low-calorie diets are common approaches taken to produce an energy deficit for weight loss in obesity. Changes in visceral and abdominal subcutaneous fat associated with weight loss are important questions but have not yet been concluded. We investigated the relationship between changes in visceral (VAT) and subcutaneous adipose tissue (SAT) areas obtained by abdominal imaging with the change in total body fat. The relevant databases were searched through January 2021 according to the PRISMA guidelines. Sixty-five studies were included. We found that the change in total body fat was associated with changes in both VAT and abdominal SAT areas, but the relationship between total body fat and the abdominal SAT area appeared stronger. Baseline values of VAT and abdominal SAT area were similar in the three treatment groups (calorie restriction, calorie restriction plus exercise, and exercise alone). The reduction in abdominal SAT area for a loss of 1 kg of total body fat was about 10 cm2, which was similar among all the treatments. The change in VAT area (-26.3 cm2) was a similar level as the change in abdominal SAT area (-31.5 cm2) in the exercise, whereas in the calorie restriction with and without exercise, the change in VAT area (-33.6 and -51.6 cm2, respectively) was approximately half of the reduction of SAT area (-65.1 and -87.2 cm2, respectively). Absolute changes in VAT and abdominal SAT areas might differ between interventions for the exercise and calorie restriction with and without exercise.

The Effect of Blood Flow Restriction Therapy on Recovery After Experimentally Induced Muscle Weakness and Pain.

ABSTRACT: Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res 36(4): 1147-1152, 2022-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

Blood Flow Restricted Exercise and Discomfort: A Review.

ABSTRACT: Spitz, RW, Wong, V, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. Blood flow restricted exercise and discomfort: A review. J Strength Cond Res 36(3): 871-879, 2022-Blood flow restriction exercise involves using a pneumatic cuff or elastic band to restrict arterial inflow into the muscle and block venous return out of the muscle during the exercise bout. The resultant ischemia in conjunction with low-load exercise has shown to be beneficial with increasing muscle size and strength. However, a limitation of using blood flow restriction (BFR) is the accompanying discomfort associated with this type of exercise. Factors that may influence discomfort are applied pressure, width of the cuff, cuff material, sex, and training to failure. The goal of this review was to evaluate the existing literature and elucidate how these factors can be manipulated to reduce discomfort during exercise as well as provide possible directions for future research. Thirty-eight different studies were located investigating BFR and discomfort. It was found that BFR training causes more discomfort than exercise without BFR. However, chronic use of BFR may increase tolerability, but discomfort may still be elevated over traditional non-blood flow restricted exercise. Discomfort can be attenuated by the application of lower applied pressures and stopping short of task failure. Finally, in the upper body, wider cuffs seem to increase ratings of discomfort compared with more narrow cuffs. In conclusion, applying the proper-sized cuff and making the applied pressure relative to both the individual and the cuff applied may attenuate discomfort. Reducing discomfort during exercise may help increase adherence to exercise and rehabilitation programs.

Blood flow restriction training on resting blood pressure and heart rate: a meta-analysis of the available literature.

The purpose of this meta-analysis was to examine the effects of blood flow restriction training on resting blood pressure and heart rate. A meta-analysis was completed in May 2020 including all previously published papers on blood flow restriction and was analyzed using a random effects model. To be included, studies needed to implement a blood flow restriction protocol compared to the same exercise protocol without restriction. A total of four studies met the inclusion criteria for quantitative analysis including four effect sizes for resting systolic blood pressure, four effect sizes for resting diastolic blood pressure, and three effect sizes for resting heart rate. There was evidence of a difference [mean difference (95 CI)] in resting systolic blood pressure between training with and without blood flow restriction [4.2 (0.3, 8.0) mmHg, p = 0.031]. No significant differences were observed when comparing resting diastolic blood pressure [1.2 (-1, 3.5) mmHg p = 0.274] and resting heart rate [-0.2 (-4.7, 4.1) bpm, p = 0.902] between chronic exercise with and without blood flow restriction. These results indicate that training with blood flow restriction may elicit an increase in resting systolic blood pressure. However, lack of data addressing this topic makes any conclusion speculative. Based on the results of the present study along with the overall lack of long-term data, it is suggested that future research on this topic is warranted. Recommendations include making changes in resting blood pressure a primary outcome and increasing the sample size of the interventions.

Hypoalgesia following isometric handgrip exercise with and without blood flow restriction is not mediated by discomfort nor changes in systolic blood pressure.

The purpose was to examine the effect of isometric handgrip exercise with and without blood flow restriction on exercise-induced hypoalgesia at a local and non-local site, and its underlying mechanisms. Sixty participants (21 males & 39 females, 18-35 years old) completed 3 trials: four sets of 2-minute isometric handgrip exercise at 30% of maximum handgrip strength; isometric handgrip exercise with blood flow restriction at 50% of arterial occlusion pressure; and a non-exercise time-matched control. Pain thresholds increased similarly in both exercise conditions at a local (exercise conditions: ~0.45 kg/cm2, control: ~-0.04 kg/cm2) and non-local site (exercise conditions: ~0.37 kg/cm2, control: ~-0.16 kg/cm2). Blood flow restriction induced greater feelings of discomfort compared to exercise alone [median difference (95% credible interval) of 4.5 (0.5, 8.6) arbitrary units]. Blood pressure increased immediately after exercise (systolic: 10.3 mmHg, diastolic: 7.7 mmHg) and decreased in recovery. There was no within participant correlation between changes in discomfort and pressure pain threshold. A bout of isometric handgrip exercise with or without blood flow restriction can provide exercise-induced hypoalgesia at a local and non-local site. However, discomfort and changes in systolic blood pressure do not explain this response.