Delayed Onset Muscle Soreness and Perceived Exertion After Blood Flow Restriction Exercise

Effects of a Perioperative Blood Flow Restriction Therapy Program on Early Quadriceps Strength and Patient-Reported Outcomes After Anterior Cruciate Ligament Reconstruction

Background

Quadriceps muscle atrophy remains a limiting factor in returning to activity after anterior cruciate ligament reconstruction (ACLR). Blood flow restriction (BFR) therapy may accelerate quadriceps strengthening in the perioperative period.

Purpose

To evaluate postoperative isometric quadriceps strength in patients who underwent ACLR with a perioperative BFR program.

Study Design

Randomized controlled trial; Level of evidence, 1.

Methods

Patients indicated for ACLR were randomized into 2 groups, BFR and control, at their initial clinic visit. All patients underwent 2 weeks of prehabilitation preoperatively, with the BFR group performing exercises with a pneumatic cuff set to 80% limb occlusion pressure placed over the proximal thigh. All patients also underwent a standardized postoperative 12-week physical therapy protocol, with the BFR group using pneumatic cuffs during exercise. Quadriceps strength was measured as peak and mean torque during seated leg extension and presented as quadriceps index (percentage vs healthy limb). Patient-reported outcomes (PROs), knee range of motion, and quadriceps circumference were also gathered at 6 weeks, 3 months, and 6 months postoperatively, and adverse effects were recorded.

Results

Included were 46 patients, 22 in the BFR group (mean age, 25.4 ± 10.6 years) and 24 in the control group (mean age, 27.5 ± 12.0 years). At 6 weeks postoperatively, the BFR group demonstrated significantly greater strength compared with the controls (quadriceps index: 57% ± 24% vs 40% ± 18%; P = .029), and the BFR group had significantly better Patient-Reported Outcomes Measurement Information System-Physical Function (42.69 ± 5.64 vs 39.20 ± 5.51; P = .001) and International Knee Documentation Committee (58.22 ± 7.64 vs 47.05 ± 13.50; P = .011) scores. At 6 weeks postoperatively, controls demonstrated a significant drop in the peak torque generation of the operative versus nonoperative leg. There were no significant differences in strength or PROs at 3 or 6 months postoperatively. Three patients elected to drop out of the BFR group secondary to cuff intolerance during exercise; otherwise, no other severe adverse events were reported.

Conclusion

Integrating BFR into perioperative physical therapy protocols led to improved strength and increased PROs at 6 weeks after ACLR. No differences in strength or PROs were found at 3 and 6 months between the 2 groups.

Registration

NCT04374968 (ClinicalTrials.gov identifier).

Low-Level Laser Therapy Facilitates Postcontraction Recovery with Ischemic Preconditioning

PURPOSE

Despite early development of muscle fatigue, ischemic preconditioning is gaining popularity for strength training combined with low-load resistance exercise. This study investigated the effect of low-level laser (LLL) on postcontraction recovery with ischemic preconditioning.

METHODS

Forty healthy adults (22.9 ± 3.5 yr) were allocated into sham (11 men, 9 women) and LLL (11 men, 9 women) groups. With ischemic preconditioning, they were trained with three bouts of intermittent wrist extension of 40% maximal voluntary contraction (MVC). During the recovery period, the LLL group received LLL (wavelength of 808 nm, 60 J) on the working muscle, whereas the sham group received no sham therapy. MVC, force fluctuations, and discharge variables of motor units (MU) for a trapezoidal contraction were compared between groups at baseline (T0), postcontraction (T1), and after-recovery (T2).

RESULTS

At T2, the LLL group exhibited a higher normalized MVC (T2/T0; 86.22% ± 12.59%) than that of the sham group (71.70% ± 13.56%; P = 0.001). The LLL group had smaller normalized force fluctuations (LLL, 94.76% ± 21.95%; sham, 121.37% ± 29.02%; P = 0.002) with greater normalized electromyography amplitude (LLL, 94.33% ± 14.69%; sham, 73.57% ± 14.94%; P < 0.001) during trapezoidal contraction. In the LLL group, the smaller force fluctuations were associated with lower coefficients of variation of interspike intervals of MUs (LLL, 0.202 ± 0.053; sham, 0.208 ± 0.048; P = 0.004) with higher recruitment thresholds (LLL, 11.61 ± 12.68 %MVC; sham, 10.27 ± 12.73 %MVC; P = 0.003).

CONCLUSIONS

LLL expedites postcontraction recovery with ischemic preconditioning, manifesting as superior force generation capacity and force precision control for activation of MU with a higher recruitment threshold and lower discharge variability.

Transcranial Direct Current Stimulation Combined With or Without Caffeine: Effects on Training Volume and Pain Perception

Purpose: This study aimed to investigate the acute effects of tDCS combined with caffeine intake on training volume and pain perception in the bench press in resistance-trained males. The correlation between training volume and pain perception was also assessed in all interventions. Methods: Sixteen healthy males (age = 25.2 ± 4.7 years, body mass = 82.8 ± 9.1 kg, and height = 178.3 ± 5.7 cm), advanced in RT, were randomized and counterbalanced for the following experimental conditions: Sham tDCS with placebo intake (Sham+Pla), Sham tDCS with caffeine intake (Sham+Caff), anodal tDCS with placebo intake (a-tDCS+Pla), and anodal tDCS with caffeine intake (a-tDCS+Caff). The caffeine or placebo ingestion (both with 5 mg.kg^-1) occurred 40 minutes before the tDCS sessions. The tDCS was applied over the left DLPFC for 20 minutes, with a 2 mA current intensity. After the tDCS sessions, participants performed the bench press with an 80% of 1RM load, where training volume and pain perception were measured. Results: Training volume was higher in the 1^st and 2^nd sets in both a-tDCS+Caff and Sham+Caff conditions, compared to the Sham+Pla condition (P < .05). Both a-tDCS+Caff and a-tDCS+Pla showed an increased pain perception during the third set compared to the first set. Also, no correlation was found between the number of repetitions and pain perception in any condition (P > .05). Conclusion: This research revealed that caffeine intake alone could be used as an ergogenic aid during resistance training programs in resistance-trained males.

Investigating the autoregulation of applied blood flow restriction training pressures in healthy, physically active adults: an intervention study evaluating acute training responses and safety

OBJECTIVE

To examine the effects of autoregulated (AUTO) and non-autoregulated (NAUTO) blood flow restriction (BFR) application on adverse effects, performance, cardiovascular and perceptual responses during resistance exercise.

METHODS

Fifty-six healthy participants underwent AUTO and NAUTO BFR resistance exercise in a randomised crossover design using a training session with fixed amount of repetitions and a training session until volitional failure. Cardiovascular parameters, rate of perceived effort (RPE), rate of perceived discomfort (RPD) and number of repetitions were investigated after training, while the presence of delayed onset muscle soreness (DOMS) was verified 24 hours post-session. Adverse events during or following training were also monitored.

RESULTS

AUTO outperformed NAUTO in the failure protocol (p<0.001), while AUTO scored significantly lower for DOMS 24 hours after exercise (p<0.001). Perceptions of effort and discomfort were significantly higher in NAUTO compared with AUTO in both fixed (RPE: p=0.014, RPD: p<0.001) and failure protocol (RPE: p=0.028, RPD: p<0.001). Sixteen adverse events (7.14%) were recorded, with a sevenfold incidence in the fixed protocol for NAUTO compared with AUTO (NAUTO: n=7 vs AUTO: n=1) and five (NAUTO) vs three (AUTO) adverse events in the failure protocol. No significant differences in cardiovascular parameters were found comparing both pressure applications.

CONCLUSION

Autoregulation appears to enhance safety and performance in both fixed and failure BFR-training protocols. AUTO BFR training did not seem to affect cardiovascular stress differently, but was associated with lower DOMS, perceived effort and discomfort compared with NAUTO.

TRIAL REGISTRATION NUMBER

NCT04996680.

Acute Effects of Ischemic Intra-Conditioning on 30 m Sprint Performance

The present study aimed to evaluate the effects of ischemic intra-conditioning applied during rest intervals on 30 m sprint performance. Thirty-four trained male (n = 12) and female (n = 22) track and field and rugby athletes volunteered to participate in the study (age = 19.6 ± 4 years; training experience = 5.3 ± 1.9 years). In a randomized and counterbalanced order, participants performed six sets of 30 m sprints under three different testing conditions: without ischemic intra-conditioning, and with ischemic intra-conditioning at 60% or 80% arterial occlusion pressure applied bilaterally before the first trial of the sprint and during the rest periods between all sprint trials. During experimental sessions, subjects perform 6 × 30 m sprints with a 7 min rest interval between attempts. The cuffs were applied following a 1 min rest period and lasted for 5 min before being released at the 6th minute to allow for reperfusion (1 min + 5 min ischemic intra-conditioning + 1 min reperfusion). The two-way repeated measures ANOVA did not show statistically significant condition × set interaction for time of the sprint (p = 0.06; η² = 0.05). There was also no main effect of ischemic intra-conditioning for any condition (p = 0.190; η² = 0.05). This study indicates that ischemic intra-conditioning did not enhance the performance of 30 m sprints performed by athletes. However, ischemic intra-conditioning did not decrease performance either.

Effects of short-term repeated sprint training in hypoxia or with blood flow restriction on response to exercise

This study compared the effects of a brief repeated sprint training (RST) intervention performed with bilateral blood flow restriction (BFR) conditions in normoxia or conducted at high levels of hypoxia on response to exercise. Thirty-nine endurance-trained athletes completed six repeated sprints cycling sessions spread over 2 weeks consisting of four sets of five sprints (10-s maximal sprints with 20-s active recovery). Athletes were assigned to one of the four groups and subjected to a bilateral partial blood flow restriction (45% of arterial occlusion pressure) of the lower limbs during exercise (BFRG), during the recovery (BFRrG), exercised in a hypoxic room simulating hypoxia at FiO2 ≈ 13% (HG) or were not subjected to additional stress (CG). Peak aerobic power during an incremental test, exercise duration, maximal accumulated oxygen deficit and accumulated oxygen uptake (VO2) during a supramaximal constant-intensity test were improved thanks to RST (p < 0.05). No significant differences were observed between the groups (p > 0.05). No further effect was found on other variables including time-trial performance and parameters of the force-velocity relationship (p > 0.05). Thus, peak aerobic power, exercise duration, maximal accumulated oxygen deficit, and VO2 were improved during a supramaximal constant-intensity exercise after six RST sessions. However, combined hypoxic stress or partial BFR did not further increase peak aerobic power.

Effect of Blood Flow Restriction Technique on Delayed Onset Muscle Soreness: A Systematic Review

Background and Objectives: The effect of the blood flow restriction technique (BFR) on delayed onset muscular soreness (DOMS) symptoms remains unclear. Since there is no consensus in the literature, the aim of the present study is to systematically identify and appraise the available evidence on the effects of the BFR technique on DOMS, in healthy subjects. Materials and Methods: Computerized literature search in the databases Pubmed, Google Scholar, EBSCO, Cochrane and PEDro to identify randomized controlled trials that assessed the effects of blood flow restriction on delayed onset muscular soreness symptoms. Results: Eight trials met the eligibility criteria and were included in this review, presenting the results of 118 participants, with a mean methodological rating of 6/10 on the PEDro scale. Conclusions: So far, there is not enough evidence to confirm or refute the influence of BFR on DOMS, and more studies with a good methodological basis are needed, in larger samples, to establish protocols and parameters of exercise and intervention. Data analysis suggests a tendency toward the proinflammatory effect of BFR during high restrictive pressures combined with eccentric exercises, while postconditioning BFR seems to have a protective effect on DOMS. Prospero ID record: 345457, title registration: “Effect of Blood Flow Restriction Technique on the Prevention of Delayed Onset Muscle Soreness: A Systematic Review”.

Greater Neuromuscular Fatigue Following Low Load Blood Flow Restriction than Non Blood Flow Restriction Resistance Exercise Among Recreationally Active Men

PURPOSE

The purpose of this study was to examine the acute effects of low-load blood flow restriction (LLBFR) and low-load non-BFR (LL) on neuromuscular function following a bout of standardized, fatiguing leg extension muscle actions.

METHODS

Fourteen men (mean age ± SD = 23±4 yrs) volunteered to participate in this investigation and randomly performed LLBFR and LL on separate days. Resistance exercise consisted of 75 isotonic, unilateral leg extension muscle actions performed at 30% of one-repetition maximum. Prior to (pretest) and after (posttest) performing each bout of exercise, strength and neural assessments were determined.

RESULTS

There was no pretest to posttest differences between LLBFR and LL for maximal voluntary isometric contraction (MVIC) torque or V-wave/M-wave responses (muscle compound action potentials assessed during a superimposed MVIC muscle action) which exhibited decreases (collapsed across condition) of 41.2% and 26.2%, respectively. There were pretest to posttest decreases in peak twitch torque (36.0%) and sEMG (29.5%) for LLBFR but not LL, and larger decreases in voluntary activation for LLBFR (11.3%) than LL (4.5%).

CONCLUSIONS

These findings suggested that LLBFR elicited greater fatigue-induced decreases in several indices of neuromuscular function relative to LL. Despite this, both LLBFR and LL resulted in similar decrements in performance as assessed by maximal strength.

Is There a Minimum Effective Dose for Vascular Occlusion During Blood Flow Restriction Training?

Background

Blood flow restriction (BFR) training at lower exercise intensities has a range of applications, allowing subjects to achieve strength and hypertrophy gains matching those training at high intensity. However, there is no clear consensus on the percentage of limb occlusion pressure [%LOP, expressed as a % of the pressure required to occlude systolic blood pressure (SBP)] and percentage of one repetition max weight (%1RM) required to achieve these results. This review aims to explore what the optimal and minimal combination of LOP and 1RM is for significant results using BFR.

Method

A literature search using PubMed, Scopus, Wiley Online, Springer Link, and relevant citations from review papers was performed, and articles assessed for suitability. Original studies using BFR with a resistance training exercise intervention, who chose a set %LOP and %1RM and compared to a non-BFR control were included in this review.

Result

Twenty-one studies met the inclusion criteria. %LOP ranged from 40 to 150%. %1RM used ranged from 15 to 80%. Training at 1RM ≤20%, or ≥ 80% did not produce significant strength results compared to controls. Applying %LOP of ≤50% and ≥ 80% did not produce significant strength improvement compared to controls. This may be due to a mechanism mediated by lactate accumulation, which is facilitated by increased training volume and a moderate exercise intensity.

Conclusion

Training at a minimum of 30 %1RM with BFR is required for strength gains matching non-BFR high intensity training. Moderate intensity training (40-60%1RM) with BFR may produce results exceeding non-BFR high intensity however the literature is sparse. A %LOP of 50-80% is optimal for BFR training.

Efficacy and Safety of Blood Flow Restriction Training in Patients With Knee Osteoarthritis: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the efficacy and safety of blood flow restriction training (BFRT) in the treatment of patients with knee osteoarthritis (OA).

METHOD

Seven electronic databases were searched to identify trials comparing BFRT and conventional resistance training in a population with knee OA. Studies were selected according to the inclusion and exclusion criteria. Standardized mean differences (SMDs) or risk ratios (RRs) with 95% confidence intervals (95% CIs) were calculated to compare outcome measures of the groups. The methodologic quality of selected studies and the quality of evidence were evaluated for included studies.

RESULTS

A total of 5 studies were included in this meta-analysis, with very low to moderate risk of bias. The pooled results showed no significant difference between BFRT and conventional resistance training for knee OA, including pain (SMD -0.04 [95% CI -0.31, 0.24], P = 0.79), physical function performance (SMD 0.12 [95% CI -0.55, 0.78], P = 0.73), self-reported function (SMD 0.14 [95% CI -0.24, 0.52], P = 0.48), and adverse events (RR 0.45 [95% CI 0.20, 1.01], P = 0.05). In subgroup analysis, BFRT had a lower incidence of adverse events when compared with high-load resistance training (HLRT).

CONCLUSION

Data from pooled studies showed that BFRT may not have greater efficacy for treating patients with knee OA, and it is less likely to have a higher risk of adverse events. However, limited evidence supports the idea that BFRT is likely safer than HLRT. More evidence with high quality is needed in further research on efficacy and safety.

Hypoalgesic effects of a blood flow restriction technique at moderate intensity with or without motor imagery: a single-blind randomized controlled trial

PURPOSE

The main objective was to assess the hypoalgesic effect of adding blood flow restriction (BFR) training with or without motor imagery (MI) to moderate-intensity exercise. The secondary objective was to analyse the correlations of the pain pressure thresholds (PPTs) regarding perceived pain intensity, perceived fatigue, and cuff pressure discomfort.

METHODS

A sample of 42 asymptomatic participants were randomly assigned to 3 groups: control group (CG), BFR group, and BFR with MI group. All participants performed a squat exercise at an intensity of 60% of 1RM. For the BFR groups, blood occlusion occurred at 80% of maximal arterial occlusive pressure. Local, bilateral, and distal PPT were assessed pre-intervention, post-intervention and 48 h post-intervention. The perceived fatigue was assessed post-intervention, and pain intensity was assessed only 48 h post-intervention.

RESULTS

There were intragroup differences in the CG and BFR + MI group in the local PPT between the pre-intervention and post-intervention measurements (p = 0.039, d= -0.32 and p = 0.009, d= -0.46, respectively) and only in the CG in the bilateral PPT (p = 0.002, d= -0.41). The CG and BFR group showed significant differences at 48 h post-intervention, with a decrease in local PPT (p = 0.009, d = 0.51 and p = 0.049, d = 0.43, respectively) and bilateral PPT (p = 0.004, d = 0.53 and p = 0.021, d = 0.46, respectively). There was a negative moderate correlation between local PPT at the post-intervention time and perceived discomfort of the occlusion device only in the BFR group (r=-0.54, p = 0.045).

CONCLUSION

Moderate-intensity resistance training with high occlusion did not generate hypoalgesia but did appear to generate a hyperalgesic response within 48 h after the intervention.

Acute cellular and molecular responses and chronic adaptations to low-load blood flow restriction and high-load resistance exercise in trained individuals

Blood flow restriction (BFR) with low-load resistance exercise (RE) is often used as a surrogate to traditional high-load RE to stimulate muscular adaptations, such as hypertrophy and strength. However, it is not clear whether such adaptations are achieved through similar cellular and molecular processes. We compared changes in muscle function, morphology and signaling pathways between these differing training protocols. Twenty-one males and females (mean ± SD: 24.3 ± 3.1 years) experienced with resistance training (4.9 ± 2.6 years) performed nine weeks of resistance training (three times per week) with either high-loads (75-80% 1RM; HL-RT), or low-loads with BFR (30-40% 1RM; LL-BFR). Before and after the training intervention, resting muscle biopsies were collected, and quadricep cross-sectional area (CSA), muscular strength and power were measured. Approximately 5 days following the intervention, the same individuals performed an additional 'acute' exercise session under the same conditions, and serial muscle biopsies were collected to assess hypertrophic- and ribosomal-based signaling stimuli. Quadricep CSA increased with both LL-BFR (7.4±4.3%) and HL-RT (4.6±2.9%), with no significant differences between training groups (p=0.37). Muscular strength also increased in both training groups, but with superior gains in squat 1RM occurring with HL-RT (p<0.01). Acute phosphorylation of several key proteins involved in hypertrophy signaling pathways, and expression of ribosomal RNA transcription factors occurred to a similar degree with LL-BFR and HL-RT (all p>0.05 for between-group comparisons). Together, these findings validate low-load resistance training with continuous BFR as an effective alternative to traditional high-load resistance training for increasing muscle hypertrophy in trained individuals.

Tolerance to Intermittent vs. Continuous Blood Flow Restriction Training: A meta-Analysis

The proven beneficial effects of low-load blood flow restriction training on strength gain has led to further exploration into its application during rehabilitation, where the traditional use of heavy loads may not be feasible. With current evidence showing that low-load blood flow restriction training may be less well tolerated than heavy-load resistance training, this review was conducted to decipher whether intermittently deflating the pressure cuff during rest intervals of a training session improves tolerance to exercise, without compromising strength. Four databases were searched for randomized controlled trials that compared the effect of intermittent versus continuous blood flow restriction training on outcomes of exercise tolerance or strength in adults. Nine studies were identified, with six included in the meta-analysis. No significant difference in rate of perceived exertion was found (SMD-0.06, 95% CI-0.41 to 0.29, p=0.73, I ²=80%). Subgroup analysis excluding studies that introduced bias showed a shift towards favoring the use of intermittent blood flow restriction training (SMD-0.42, 95% CI-0.87 to 0.03, p=0.07, I ²=0%). There was no significant difference in strength gain. Intermittent cuff deflations during training intervals does not improve tolerance to exercise during blood flow restriction training.

The effects of blood flow restriction resistance training on indices of delayed onset muscle soreness and peak power

BACKGROUND: Low-load resistance training with blood flow restriction (LL + BFR) attenuated delayed onset muscle soreness (DOMS) under some conditions. OBJECTIVE: The purpose of this study examined the effects of reciprocal concentric-only elbow flexion-extension muscle actions at 30% of peak torque on indices of DOMS. METHODS: Thirty untrained women (mean ± SD; 22 ± 2.4 years) were randomly assigned to 6 training days of LL + BFR (n= 10), low-load non-BFR (LL) (n= 10), or control (n= 10). Participants completed 4 sets (1 × 30, 3 × 15) of submaximal (30% of peak torque), unilateral, isokinetic (120∘s-1) muscle actions. Indices of DOMS including peak power, resting elbow joint angle (ROM), perceived muscle soreness (VAS), and pain pressure threshold (PPT) were assessed. RESULTS: There were no changes in peak power, ROM, or VAS. There was a significant interaction for PPT. Follow-up analyses indicated PPT increased for the LL + BFR condition (Day 5 > Day 2), but did not decrease below baseline. The results of the present study indicated LL + BFR and LL did not induce DOMS for the elbow extensors in previously untrained women. CONCLUSION: These findings suggested LL + BFR and LL concentric-only resistance training could be an effective training modality to elicit muscular adaptation without inducing DOMS.

Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7

BACKGROUD

Blood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training.

METHODS

A total of 7 healthy young men performed squats, and between sets BFR was carried out on one leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mmHg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training.

RESULTS

Doppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. microRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-β serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg.

CONCLUSION

BFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

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.

Impact of Three Consecutive Days of Endurance Training Under Hypoxia on Muscle Damage and Inflammatory Responses

Purpose: The purpose of this study was to determine the effect of 3 consecutive days of endurance training under hypoxia on muscle damage, inflammation, and performance responses.

Methods: Nine active healthy males completed two trials in different periods, consisting of either 3 consecutive days of endurance training under hypoxia [fraction of inspired oxygen (Fio₂): 14.5%, HYP] or normoxia (Fio₂: 20.9%, NOR). They performed daily 90-min sessions of endurance training consisting of high-intensity endurance interval pedaling [10 × 4-min pedaling at 80% of maximal oxygen uptake (V˙o2max) with 2 min of active rest at 30% of V˙o2max] followed by 30-min continuous pedaling at 60% of V˙o2max during 3 consecutive days (days 1–3). Venous blood sample, muscular performance of lower limb, and score of subjective feelings were determined every morning (days 1–4) to evaluate muscle damage and inflammation. On day 4, subjects performed an incremental exercise test (IET) to evaluate the performance response.

Results: Pedaling workload during daily endurance training was significantly lower in the HYP trial (interval exercise: 166 ± 4 W) than in the NOR trial (194 ± 8 W; P < 0.0001). Serum creatine kinase (CK) and high-sensitivity C-reactive protein (hsCRP) concentrations did not significantly change during days 1–4 in either trial. Maximal voluntary contraction (MVC) of knee extension (P < 0.0001) and drop jump (DJ) index (P = 0.004) were significantly decreased with training in both trials, with no significant difference between trials. The muscle soreness and fatigue scores significantly increased in both trials (P < 0.0001). However, the HYP trial showed a significantly lower score of fatigue on day 4 compared with the NOR trial (P = 0.004). Maximal aerobic power output during IET on day 4 did not significantly differ between trials.

Conclusion: Three consecutive days of endurance training under hypoxia induced comparable levels of muscle damage, inflammation, and performance responses compared with the same training under normoxia.

IN-SEASON REHABILITATION PROGRAM USING BLOOD FLOW RESTRICTION THERAPY FOR TWO DECATHLETES WITH PATELLAR TENDINOPATHY: A CASE REPORT

Background and Purpose

Patellar tendinopathy is an overuse injury experienced primarily by athletes; especially athletes who participate in sports that involve frequent jumping. Therapeutic exercise is the primary conservative treatment for patients with this condition. However, some patients with patellar tendinopathy may be unable to tolerate the loading that occurs during exercise. The use of blood flow restriction (BFR) therapy for patients with patellar tendinopathy may allow the athlete to exercise with a lower load while still experiencing the physiological benefits associated with training at a higher intensity. The purpose of this case report was to detail the outcomes from a rehabilitation program utilizing BFR for two collegiate decathletes with patellar tendinopathy.

Study Design

Case ReportCase Descriptions and Interventions: Two NCAA Division III freshmen collegiate decathletes with a history of left knee pain prior to college and who had been complaining of increasing pain during the initial month of track practices. Findings from the musculoskeletal examinations included left sided lower extremity weakness, pain during functional testing, pain when palpating the left patellar tendon, and VISA-P scores less than 80. Ultrasound imaging at baseline revealed thickened tendons on the left with hypoechoic regions. Both athletes participated in 20 therapy sessions consisting of therapeutic exercises performed with BFR.

Outcomes

Both athletes experienced improvements in pain scores, increases in lower extremity strength, improved functional test performance, higher VISA-P scores, and improvements in tendon size and appearance as measured by diagnostic ultrasound.

Conclusion

Both athletes experienced improvements with the BFR-based therapeutic exercise program and were able to compete throughout the track season. The use of BFR may allow patients who are unable to tolerate exercise due to pain an alternative approach during rehabilitation. Future research should compare therapeutic exercise programs for this condition with and without BFR.

Level of Evidence

Level V.

Perceptual and Neuromuscular Responses Adapt Similarly Between High-Load Resistance Training and Low-Load Resistance Training With Blood Flow Restriction

Teixeira, EL, Painelli, VdS, Schoenfeld, BJ, Silva-Batista, C, Longo, AR, Aihara, AY, Cardoso, FN, Peres, BdA, and Tricoli, V. Perceptual and neuromuscular responses adapt similarly between high-load resistance training and low-load resistance training with blood flow restriction. J Strength Cond Res XX(X): 000-000, 2020-This study compared the effects of 8 weeks of low-load resistance training with blood flow restriction (LL-BFR) and high-load resistance training (HL-RT) on perceptual responses (rating of perceived exertion [RPE] and pain), quadriceps cross-sectional area (QCSA), and muscle strength (1 repetition maximum [RM]). Sixteen physically active men trained twice per week, for 8 weeks. One leg performed LL-BFR (3 sets of 15 repetitions, 20% 1RM), whereas the contralateral leg performed HL-RT (3 sets of 8 repetitions, 70% 1RM). Rating of perceived exertion and pain were evaluated immediately after the first and last training sessions, whereas QCSA and 1RM were assessed at baseline and after training. Rating of perceived exertion was significantly lower (6.8 ± 1.1 vs. 8.1 ± 0.8, p = 0.001) and pain significantly higher (7.1 ± 1.2 vs. 5.8 ± 1.8, p = 0.02) for LL-BFR than that for HL-RT before training. Significant reductions in RPE and pain were shown for both protocols after training (both p < 0.0001), although no between-protocol differences were shown in absolute changes (p = 0.10 and p = 0.48, respectively). Both LL-BFR and HL-RT were similarly effective in increasing QCSA (7.0 ± 3.8% and 6.3 ± 4.1%, respectively; both p < 0.0001) and 1RM (6.9 ± 4.1% and 13.7 ± 5.9%, respectively; both P < 0.0001), although absolute changes for 1RM in HL-RT were greater than LL-BFR (p = 0.001). In conclusion, LL-BFR produces lower RPE values and a higher pain perception than HL-RT. However, consistent application of these approaches result in chronic adaptations so that there are no differences in perceptual responses over the course of time. In addition, muscle strength is optimized with HL-RT despite similar increases in muscle hypertrophy between conditions.

The Safety of Blood Flow Restriction Training as a Therapeutic Intervention for Patients With Musculoskeletal Disorders: A Systematic Review

BACKGROUND

The effectiveness of blood flow restriction training (BFRT) as compared with other forms of training, such as resistance training, has been evaluated in the literature in clinical and nonclinical populations. However, the safety of this intervention has been summarized only in healthy populations and not in clinical populations with musculoskeletal disorders.

PURPOSE

To evaluate the safety and adverse events associated with BFRT in patients with musculoskeletal disorders.

STUDY DESIGN

Systematic review.

METHODS

A literature search was conducted with 3 online databases (MEDLINE, CINAHL, and Embase). Eligibility criteria for selecting studies were as follows: (1) BFRT was used as a clinical intervention, (2) study participants had a disorder of the musculoskeletal system, (3) authors addressed adverse events, (4) studies were published in English, and (5) the intervention was performed with human participants.

RESULTS

Nineteen studies met eligibility criteria, with a pooled sample size of 322. Diagnoses included various knee-related disorders, inclusion body myositis, polymyositis or dermatomyositis, thoracic outlet syndrome, Achilles tendon rupture, and bony fractures. Nine studies reported no adverse events, while 3 reported rare adverse events, including an upper extremity deep vein thrombosis and rhabdomyolysis. Three case studies reported common adverse events, including acute muscle pain and acute muscle fatigue. In the randomized controlled trials, individuals exposed to BFRT were not more likely to have an adverse event than individuals exposed to exercise alone. Of the 19 studies, the adverse events were as follows: overall, 14 of 322; rare overall, 3 of 322; rare BFRT, 3 of 168; rare control, 0 of 154; any adverse BFRT, 10 of 168; any adverse control, 4 of 154. A majority of studies were excluded because they did not address safety.

CONCLUSION

BFRT appears to be a safe strengthening approach for knee-related musculoskeletal disorders, but further research is needed to make definitive conclusions and to evaluate the safety in other musculoskeletal conditions. Improved definitions of adverse events related to BFRT are needed to include clear criteria for differentiating among common, uncommon, and rare adverse events. Finally, further research is needed to effectively screen who might be at risk for rare adverse events.

[Blood flow restriction training for people with cardiovascular disease: An exploratory review]

OBJECTIVE

To analyse the evidence on the effects of blood flow restriction training in people with cardiovascular disease.

MATERIALS AND METHODS

We searched MEDLINE, EMBASE, SPORTDiscus, CINAHL, LILACS, SCOPUS and Wiley databases. Experimental and non-experimental studies investigating the effects of blood flow restriction in participants with cardiovascular disease were included.

RESULTS

Six clinical trials and three non-experimental studies met the inclusion criteria. The experimental studies were conducted in participants with hypertension and ischaemic heart disease. Non-experimental studies described hemodynamic adaptations and potential adverse effects of therapy. The risk of bias of the included clinical trials was moderate to high. Exercise-induced hemodynamic stress increased significantly during training with blood flow restriction compared with traditional training. The small number of available studies have focused mostly on acute effects, but chronic effects are unknown.

CONCLUSION

There is currently no evidence to recommend the use of blood flow restriction in people with cardiovascular disease.

Efficacy of blood flow restriction exercise during dialysis for end stage kidney disease patients: protocol of a randomised controlled trial

BACKGROUND

Exercise during haemodialysis improves strength and physical function. However, both patients and clinicians are time poor, and current exercise recommendations add an excessive time burden making exercise a rare addition to standard care. Hypothetically, blood flow restriction exercise performed during haemodialysis can provide greater value for time spent exercising, reducing this time burden while producing similar or greater outcomes. This study will explore the efficacy of blood flow restriction exercise for enhancing strength and physical function among haemodialysis patients.

METHODS

This is a randomised controlled trial design. A total of 75 participants will be recruited from haemodialysis clinics. Participants will be allocated to a blood flow restriction cycling group, traditional cycling group or usual care control group. Both exercising groups will complete 3 months of cycling exercise, performed intradialytically, three times per week. The blood flow restriction cycling group will complete two 10-min cycling bouts separated by a 20-min rest at a subjective effort of 15 on a 6 to 20 rating scale. This will be done with pressurised cuffs fitted proximally on the active limbs during exercise at 50% of a pre-determined limb occlusion pressure. The traditional cycling group will perform a continuous 20-min bout of exercise at a subjective effort of 12 on the same subjective effort scale. These workloads and volumes are equivalent and allow for comparison of a common blood flow restriction aerobic exercise prescription and a traditional aerobic exercise prescription. The primary outcome measures are lower limb strength, assessed by a three repetition maximum leg extension test, as well as objective measures of physical function: six-minute walk test, 30-s sit to stand, and timed up and go. Secondary outcome measures include thigh muscle cross sectional area, body composition, routine pathology, quality of life, and physical activity engagement.

DISCUSSION

This study will determine the efficacy of blood flow restriction exercise among dialysis patients for improving key physiological outcomes that impact independence and quality of life, with reduced burden on patients. This may have broader implications for other clinical populations with similarly declining muscle health and physical function, and those contraindicated to higher intensities of exercise.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trial Register: ACTRN12616000121460.