Blood Flow Restricted Exercise and Reduced Oxygen Tension Decrease Mitochondrial ROS Emission in Human Muscle

Differences in muscle strength adaptations between high-load (HL) and low-load blood flow restricted (BFR) resistance training protocols may be due to the type of strength test performed (e.g isotonic, isokinetic and isometric). PURPOSE: To assess differences in isotonic, isometric and isokinetic strength adaptations in older adults following HL and BFR resistance training. METHODS: Thirty-six males and females (mean: 75.6+7.6 years, 1.67+.09 m, 74.3+13.2 kg) classified as being at risk of mobility limitations were randomly assigned to HL (70% 1-RM) or low-load BFR (30% 1-RM coupled with a vascular restriction) exercise for the knee extensors twice per week for 6 weeks. A control group performed light upper body resistance and flexibility training. Knee extension 10-RM to predict 1-RM strength, isometric maximum voluntary contraction (MVC) and isokinetic strength at 60[BULLET OPERATOR]s-1, 180[BULLET OPERATOR]s-1, and 300[BULLET OPERATOR]s-1were measured before and after 6-weeks of training. RESULTS: HL and BFR training increased predicted 1-RM strength 34% (P<.001) and 24% (P<.001) respectively, from baseline to 6-weeks of training. HL training produced a 16% increase in MVC (P=.002) while BFR training did not change (P=.91). No interventions, included the control, resulted in changes in isokinetic strength at the various speeds (P>.20). CONCLUSION: Strength improvements from HL resistance training carried over to other strength tests. This favorable adaptation did not occur following BFR exercise which may limit the effectiveness of this training program. Isotonic training does not carry over to isokinetic strength adaptations and therefore may be a drawback when implementing resistance training programs for older adults. Supported by NIH grant 1R15 A6040700-01A1.

Life‐history theory suggests that tradeoffs can occur between self‐maintance and an animal's capacity to allocate resources to reproduction. This effect is thought to be exacerbated when a female is faced with an immune challenge during a reproductive event. Ultimately, such tradeoffs are thought to curtail lifespan, but the bioenergetic underpinnings of this effect are not well understood. We determined the extent of any effects in mitochondrial function and oxidative damage in female mice when exposed to an immune challenge (keyhole limpet haemocyanin) during reproduction. Female ICR mice were paired with a male until just before giving birth and randomly assigned to one of three groups. Female mice in the control group (LC) were injected with saline 2 days after parturition, and then sacrificed 1 week after weaning. In the lactating immune challenge group (LI), females were treated similarly except they were injected with KLH. Finally, in the pregnant‐lactating immune challenge group (PLI), females were treated the same as LI group, except the male was left in the box with the female until 3 days post‐partum, so the female became pregnant again while lactating. The second litter was born within 3 days of weaning, immediately removed, and females were sacrificed 1 week later. Mitochondrial function and reactive oxygen species (ROS) emission were determined in the liver and hindlimb skeletal muscle. Antioxidant protein levels and oxidative damage markers were also analyzed in these tissues. A one‐way ANOVA was performed on all measures, with a Tukey's post hoc test to determine group differences. No significant differences were observed in liver or hindlimb skeletal muscle mitochondrial coupling as measured by the respiratory control ratio (RCR) for both complex I and complex II (p&gt;0.05). Isolated mitochondrial ROS emission in the hindlimb skeletal muscle was significantly lower in LI compared to LC (p=0.041), but no differences were observed in the liver. Additionally, skeletal muscle PGC1‐α was significantly reduced in LI mice compared to LC (p=0.01). In skeletal muscle the antioxidant GPX was significantly increased in the PLI animals compared to LI animals (p=0.022). Lastly, liver SOD1 was significantly higher in LC compared to PLI (p=0.039). The opposite response was observed in HSP70, in which PLI had significantly increased expression compared to LC (p=0.018). In conclusion, females that experienced an immune challenge during reproduction did not appear to experience a decline in mitochondrial respiratory performance but a drop in PGC1‐a in skeletal muscle that could contribute to a reduction in future performance associated with a reduction in mitochondrial density.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Anoxia-reoxygenation modulates cadmium-induced liver mitochondrial reactive oxygen species emission during oxidation of glycerol 3-phosphate

PURPOSE: Blood Flow Restriction (BFR) exercise is an innovative method that can induce strength and increase muscle hypertrophy, even with low-intensity resistance exercise. This study aimed to review the physiological mechanisms, safety, major research trends, and practical applicability of BFR exercises through a literature review.METHODS: This study analyzed articles on BFR exercises published between January 1, 2000, and December 31, 2024, by searching databases such as PubMed, Google Scholar, and Web of Science. Key terms such as “Blood Flow Restriction Training,” “Low-Intensity Resistance Exercise,” “Muscle Hypertrophy,” and “Safety of BFR” were used. Research on the mechanisms, effects, safety, and application of BFR exercises were summarized.RESULTS: Previous studies have shown that BFR exercise increases metabolic stress and mechanical tension, and promotes muscle protein synthesis. Notably, even at 20–50% of the one-repetition maximum, BFR can induce similar effects as high-intensity exercise. Additionally, BFR exercises can be effectively applied in various fields, such as enhancing athletic performance, preventing sarcopenia in older individuals, and improving function in patients with chronic diseases. However, some studies have indicated that BFR exercise may increase blood pressure and the risk of thrombosis, and caution should be exercised when it is applied to individuals with cardiovascular diseases.CONCLUSIONS: The BFR exercise is a promising method for increasing strength and muscle hypertrophy, even at low intensities, and can be widely applied in rehabilitation and sports training. However, to ensure safety, proper pressure settings and adherence to protocols are essential, and special care should be taken when applied to specific populations (e.g., individuals with hypertension or cardiovascular diseases). Future research should focus on the long-term effects of BFR exercises and the development of personalized protocols.

Lipids are main fuels for cellular energy and mitochondria their major oxidation site. Yet unknown is to what extent the fuel role of lipids is influenced by their uncoupling effects, and how this affects mitochondrial energetics, redox balance and the emission of reactive oxygen species (ROS). Employing a combined experimental-computational approach, we comparatively analyze β-oxidation of palmitoyl CoA (PCoA) in isolated heart mitochondria from Sham and streptozotocin (STZ)-induced type 1 diabetic (T1DM) guinea pigs (GPs). Parallel high throughput measurements of the rates of oxygen consumption (VO2) and hydrogen peroxide (H2O2) emission as a function of PCoA concentration, in the presence of L-carnitine and malate, were performed. We found that PCoA concentration < 200 nmol/mg mito protein resulted in low H2O2 emission flux, increasing thereafter in Sham and T1DM GPs under both states 4 and 3 respiration with diabetic mitochondria releasing higher amounts of ROS. Respiratory uncoupling and ROS excess occurred at PCoA > 600 nmol/mg mito prot, in both control and diabetic animals. Also, for the first time, we show that an integrated two compartment mitochondrial model of β-oxidation of long-chain fatty acids and main energy-redox processes is able to simulate the relationship between VO2 and H2O2 emission as a function of lipid concentration. Model and experimental results indicate that PCoA oxidation and its concentration-dependent uncoupling effect, together with a partial lipid-dependent decrease in the rate of superoxide generation, modulate H2O2 emission as a function of VO2. Results indicate that keeping low levels of intracellular lipid is crucial for mitochondria and cells to maintain ROS within physiological levels compatible with signaling and reliable energy supply.

Low-intensity endurance training with blood flow restriction (BFR) elicits greater improvements in maximal oxygen consumption (V̇o2max) compared with volume-matched training. However, determinants of V̇o2max, such as oxygen-carrying capacity and mitochondrial content, do not exhibit proportional improvement. Despite the hemodynamic alterations during BFR exercise that could stimulate remodeling, cardiac adaptations remain unexplored. We assessed cardiac function in athletes (11 M/5 F) at rest, during semirecumbent cycling with BFR, and at a matched work and heart rate (HR) using echocardiography. In an exploratory analysis, a subset of athletes (5 M/2 F) then completed 6 wk of low-intensity BFR walking three times per week, and echocardiograms were repeated. Compared with rest and unoccluded exercise, BFR increased arterial elastance (rest: 1.07 ± 0.32 mmHg/mL, BFR: 1.32 ± 0.33 mmHg/mL, work-match: 0.93 ± 0.25 mmHg/mL, HR-match: 0.97 ± 0.25 mmHg/mL; all P < 0.01) and altered left ventricular (LV) filling, with a greater proportion of filling achieved through atrial contraction (rest: 45 ± 8%, BFR: 56 ± 8%, work-match: 49 ± 6%, HR-match: 46 ± 7%; all P < 0.05) to maintain end-diastolic volume (rest: 163 ± 40 mL, BFR: 163 ± 40 mL vs. work-match: 167 ± 37 mL, HR-match: 168 ± 38 mL; P = 0.5). Concurrently, stroke volume was reduced (rest: 99 ± 26 mL, BFR: 95 ± 23 mL, work-match: 109 ± 27 mL, HR-match: 110 ± 25 mL; P < 0.05), and HR was elevated (rest: 54 ± 10 beats/min, BFR and HR-match: 87 ± 13 beats/min vs. work-match: 74 ± 11 beats/min; P < 0.01) to maintain cardiac output (rest: 5.1 ± 1.2 L/min, BFR: 7.5 ± 1.0 L/min, work-match: 8.0 ± 1.2 L/min, HR-match: 9.1 ± 1.7 L/min; P < 0.0001). BFR training did not affect LV mass index (Pre: 121 ± 18 g/m2, Post: 123 ± 11 g/m2; P = 0.5), nor LV function at rest or during unoccluded exercise. However, posttraining, stroke volume during BFR exercise was increased (Pre: 101 ± 25 mL, Post: 113 ± 23 mL; P = 0.03), suggesting adaptation of the cardiac response to this specific stress. This highlights how the heart supports oxygen delivery during BFR exercise and provides insight into how cardiac adaptations may contribute to BFR training-associated improvements in V̇o2max.NEW & NOTEWORTHY Blood-flow restriction exercise uniquely challenges the heart through an increase in afterload, which necessitates altered diastolic filling patterns and increased heart rate to compensate for reduced stroke volume. Repeated exposure to low-intensity endurance-type blood-flow restriction exercise through training improves the hearts' ability to support stroke volume, specifically when performing blood-flow restriction exercise, but not low-intensity free-flow exercise.

Eserhaut, DA, DeLeo, JM, and Fry, AC. Blood flow restricted resistance exercise in well-trained men: Salivary biomarker responses and oxygen saturation kinetics. J Strength Cond Res 38(12): e716-e726, 2024-Resistance exercise with continuous lower-limb blood flow restriction (BFR) may provide supplementary benefit to highly resistance-trained men. Thus, the purpose of this study was to compare cardiovascular and salivary biomarker responses, along with skeletal muscle oxygen saturation (SmO2) during passive lower-limb BFR (pBFR), BFR resistance exercise performed to task failure (BFR+RE), and volume-matched resistance exercise (RE). A within-subjects, repeated measures design was used. Nineteen men (x̄±SD: relative squat 1RM: 1.9 ± 0.3 kg·bw-1) reported for 3 visits. First, body composition, blood pressure, back squat, and leg extension 1 repetition maximums (1RM) were assessed. Resting systolic blood pressure and proximal thigh circumferences were used to estimate arterial occlusion pressures (eAOP). Visit 1 involved pBFR, where BFR cuffs were inflated to 80% eAOP around the proximal thighs for 10 minutes while subjects were seated in a leg extension machine. Then, 24-120 hours later, 4 sets of bilateral seated leg extensions at 30% 1RM were performed to momentary task failure with 1-minute rest at the same 80% eAOP. After 72-120 hours rest, subjects matched the repetition performances from BFR+RE at 30% 1RM for the RE condition. BFR+RE elicited greater (p ≤ 0.05) heart rates, systolic, and diastolic blood pressures relative to pBFR and RE. Significantly elevated (p ≤ 0.05) blood lactate, salivary cortisol concentrations, and α-amylase activity occurred following BFR+RE relative to pBFR and RE. BFR+RE also induced blunted (p < 0.001) SmO2 interset resaturation rates compared with RE. In trained men, continuous BFR+RE seems to significantly alter acute physiological responses to a greater degree than either pBFR alone or volume-matched RE.

This systematic review investigated protocols used in Blood Flow Restriction (BFR) exercise training and evaluated the intensity of exercise and length of training for the development of muscle hypertrophy and strength. Twelve studies were included according to criteria. The Random-effects Model was used to teste the intensity of exercise and length of training in quadriceps femoral. In general, the BFR group was associated with an increase in Muscle Cross-sectional Area (CSA) of 3.84%; however, it was not associated with an increase in quadriceps strength compared with the control group. When the analyses were made considering the intensity of the exercise and length of training, the results showed that BFR exercise ≤ 30% of One Repetition Maximal (1RM) and the length of training ≤ 2 weeks were associated with an increase in quadriceps CSA and strength compared with the control group. The analyses provide subsidies that BFR training until 30% 1RM and a length of training until 2 weeks are the most effective to develop muscle hypertrophy and strength in lower limbs than exercise more than 30%1RM and more than 4 weeks of length training.

Objectives:Blood Flow Restriction (BFR) training provides partial occlusion at the proximal upper and lower extremities and has been shown to improve muscular strength and hypertrophy following an injury or surgery. By eliciting hypoxic intramuscular conditions, we can stimulate adaptive processes in skeletal muscle in a similar manner to high intensity resistance training but at substantially lower and safer exercise workloads (20-30%1RM). While much of the literature has focused on tissues distal to the site of occlusion, recent findings (Lambert et al 2021, Bowman et al 2020) have observed proximal benefits (increased muscle mass, work capacity, and performance) to upper extremity BFR in the shoulder region during rotator cuff training in both general population adults and pitching athletes. These findings were partially attributed to increased muscle activation (via electromyography, EMG) observed while extremities were under occlusion. However, only one standardized occlusion pressure (50%LOP) was utilized during these investigations as typical in current literature. The purpose of the present study was to compare muscle activation (EMG amplitude, EMGa) of the shoulder region during BFR training at variable occlusion pressures in order to optimize application and muscle-specific targeting of BFR for rehabilitation and preventative shoulder training.Methods:Institutional review board approval was first obtained. Fifteen healthy subjects (7 males and 8 females; age 29.4 ± 4.26 y.o.) from a sports medicine physical therapy clinic were recruited and consented to participate in this study. Individuals were excluded if they had any pre-existing shoulder pathology in the dominant limb, active participation in a structured upper body weight regimen, or any history of vascular compromise that may render use of BFR inappropriate. Each participant underwent 4 different experimental sessions, which included performing 3 common exercises for the shoulder to failure on the dominant limb; dumbbell scaption, cable external rotation (ER) @ 0°, and cable internal rotation (IR) @ 0°. Exercises were completed with BFR using an automated tourniquet system (Delfi Medical Innovations®) at a different pre-assigned occlusion pressure (0, 25, 50, 75% LOP) each session. Load was determined using 20% of a one-repetition maximum (1RM) for each exercise utilizing a maximal voluntary isometric contraction (MVIC) test. EMGa data utilizing surface electrodes (Delsys, Natick, MA, US) were recorded from target shoulder muscles proximal to the occlusive cuff during testing - anterior deltoid, middle deltoid, posterior deltoid, infraspinatus, teres minor, and upper trapezius muscles. Repetitions to failure (RTF) and assessments of discomfort (VAS, 0-10) with each exercise at the various occlusive pressures were also collected for analysis. Raw EMGa measures were averaged across the first 30 contractions for IR and scaption as well as the first 20 contractions for ER following normalization to 5 calibration contractions at 0% LOP. A mixed model ANOVA repeated on occlusion pressure was performed followed by a Bonferroni post hoc test for pairwise comparisons. Type I error set at ∝=0.05.Results:EMG findings are presented in Figure 1 demonstrating a significant effect of occlusion level on shoulder muscle activation for all exercises (p<0.05). Of note, continued significant increases in EMGa were not observed above 50%LOP with the exception of the teres minor during IR (Figure 1A) or the posterior deltoid during scaption (Figure 1C). As shown in Figure 2, significant decreases in repetitions to failure relative to 0%LOP were observed at 75%LOP for all exercises as well as at 50%LOP for scaption (p<0.05). Also shown in Table 1, a linear increase in discomfort was observed for all exercises with increasing LOP (p<0.01).Conclusions:There appears to be several distinct differences in muscle activation about the shoulder complex based on the exercise as well as occlusive pressure; including a common trend of heightened EMG activity being concurrent with an increase in LOP. These findings may indicate that added occlusion leads to greater muscle utilization, enhancing exercise selection and prescription dependent on the targeted muscle group. However, based on these data, there may be an element of diminishing returns past 50% LOP for the exercises and musculature studied, ultimately limiting efficacy past this occlusion stimulus when considering discomfort or total achievable exercise volume. While limited to the population study, these findings paired with those found in general and athletic populations may be used to establish BFR guidelines which may be suitable for shoulder rehabilitation or injury prevention.

The purpose of this study was to characterise how blood flow restriction (BFR) exercise is utilised by practitioners in high-performance sports settings. Participants (n = 154) engaged with the questionnaire, of which 123 provided data about their use of BFR with athletes in high-performance sports settings. The main findings indicated that BFR was primarily used for injury rehabilitation (81.3% of practitioners) or supplementary to traditional strength and conditioning programs for muscle hypertrophy (80.4%), limiting loss of muscle mass (71.9%), or muscle strengthening (51.6%). Participants used BFR with both team and individual sports, but with only a small subset of the athletes they worked with (65% of practitioners used BFR with less than 25% of their athletes). Cuff pressures were prescribed using both measured individualised occlusion pressures (56.1%) and arbitrary set pressures (52.8%). Despite practitioners’ awareness of contraindications and the need for screening, formal screening tools were underutilised (55.7% of practitioners did not use a screening tool for clearance to use BFR). Ultimately, BFR exercise was largely prescribed in line with established guidelines, although the application of individualised cuff pressures and health screening processes may require further attention from practitioners in high-performance sports.

Overall, there is a great need within sports medicine to ensure that athletes can return from injury in an efficient, yet thorough manner. It is crucial to not avoid necessary difficulties in this process but also to ensure time-efficient rehabilitation. One of the more promising techniques to achieve timely recovery is blood flow restriction (BFR) training. BFR training is a growing and novel development that could be a vital tool to lighten the burden of recovery from injury in athletes. BFR utilizes a pneumatic tourniquet to limit blood flow in specific areas of the body. The use of BFR has been shown to potentially enhance the analgesic effects of exercise-induced hypoalgesia (EIH). By limiting pain, athletes will be less burdened by mobility and loading exercises required for them to effectively return to play. In a field where time away from sports can have massive implications, the need for tools to assist in the acceleration of the rehabilitation process is vital. Much of the work that has already been done in the field has been able to exploit the benefits of EIHand further enhance the body's capabilities through BFR. Studies have compared EIH at low- and high-intensity settings utilizing BFR with both resistance and aerobic exercise. The results of these studies show comparable beta-endorphin levels with high-intensity exercise without BFR and low-intensity exercise with BFR. Low-intensity training with BFR had greater local pain relief, perhaps indicating the promising effects of BFR in enhancing EIH. By reviewing the current literature on this topic, we hope that further progress can be made to better understand the mechanism behind BFR and its ability to enhance EIH. Currently, local metabolites are a major focus for the potential mechanism behind these effects. Mas-related G-protein-coupled receptors (Mrgprs) contribute to local pain pathways via mast cell degranulation. Similarly, chemokine receptor 2/chemokine ligand 2 (CCR2/CCL2) triggers mast cell degranulation and inflammation-induced pain. Finally, pain-reducing effects have been linked to anti-inflammatory IL-10 signaling and anaerobic metabolites via transient receptor potential vanilloid 1 (TRPV1). Through a better understanding of these metabolites and their mechanisms, it is possible to further exploit the use of BFR to not only serve athletes recovering from injury but also apply this information to better serve all patients.

Background: Osteoarthritis (OA) is the third leading cause of disability worldwide, significantly impacting pain, physical function, and quality of life (QoL). Among its types, knee osteoarthritis (KOA) is the most prevalent, affecting over 80% of individuals with OA. Effective conservative management is crucial for mitigating its physical and social burden. Exercise therapy, including strength training, has been widely utilized; however, the comparative efficacy of blood flow restriction training (BFRT) and traditional strength training remains underexplored. Objective: This study aimed to compare the impact of BFRT and traditional strength training on pain and QoL in patients with KOA. Methods: This randomized controlled trial was conducted between March 2024 and August 2024, enrolling 38 patients with KOA using a purposive sampling technique. Participants aged 40–70 years with clinically and radiologically confirmed KOA experiencing moderate-to-severe symptoms were included. Patients with contraindications to BFRT, such as vascular disorders or recent surgeries, were excluded. The interventions included BFRT with low-load resistance and traditional high-load strength training. Pain and QoL were assessed using the Visual Analogue Scale (VAS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS), respectively. Ethical considerations were followed throughout the study, and SPSS version 24 was used for statistical analysis. Results: Baseline VAS scores were 7.4 ± 1.1 for the BFRT group and 7.3 ± 1.2 for the traditional group (p = 0.87). Post-intervention, VAS improved significantly in both groups, with BFRT showing a greater reduction (3.2 ± 1.0) compared to the traditional group (4.5 ± 1.1, p = 0.01). KOOS scores improved from 48.6 ± 6.9 to 72.3 ± 7.5 in the BFRT group and from 47.9 ± 7.2 to 64.7 ± 8.1 in the traditional group (p = 0.03). Both groups demonstrated significant improvements, with BFRT showing superior results. Conclusion: Both BFRT and traditional strength training significantly improved pain and QoL in KOA patients, with BFRT yielding more pronounced benefits. BFRT offers a promising low-load alternative for managing pain and enhancing QoL in individuals with KOA.

Purpose: The relationship between exercise and irisin and sex hormone release is unclear and is of interest to current research. This study aimed to investigate the acute effect of blood flow restricted (BFR) resistance exercise on irisin and sex hormones. Material and Methods: The study included healthy males over 18 years of age. Participants' physical activity levels were determined using International Physical Activity Questionnaire (IPAQ). Participants underwent body composition analysis and isotonic muscle strength measurement and were randomly divided into 3 groups: low-intensity (20% of 1-RM) resistance exercise with BFR, high-intensity (70% of 1-RM) resistance exercise without BFR, and a control group. Blood samples were obtained 15 minutes post-exercise to assess acute irisin, testosterone, and estrogen responses. Results: The study included 17 healthy males. The average age was 26.1±2.9 years, mean physical activity was 1259.2±1003.1 MET/week, and mean 1-RM max (as measured with isotonic muscle strength test) was 41.1±7.5 kg. The descriptive characteristics of the three groups were statistically similar (p&gt;0.05). The acute post-intervention irisin and sex hormone levels were not statistically different between the groups (p&gt;0.05). Conclusion: Acute changes in irisin and sex hormone levels were not statistically different for low-intensity BFR and high-intensity non-BFR exercise.

The current manuscript sets out a series of guidelines for blood flow restriction exercise, focusing on the methodology, application and safety of this mode of training. With the emergence of this technique and the wide variety of applications within the literature, the aim of this review is to set out a current research informed guide to blood flow restriction training to practitioners. This covers the use of blood flow restriction to enhance muscular strength and hypertrophy via training with resistance and aerobic exercise and preventing muscle atrophy using the technique passively. The authorship team for this article was selected from the researchers focused in blood flow restriction training research with expertise in exercise science, strength and conditioning and sports medicine.

Muscle strength gains following blood flow restricted (BFR) resistance training are consistently lower than those observed after HL training and this may be due to differences in neuromuscular activation. Integrating high-velocity muscle contractions and BFR resistance exercise may increase neuromuscular activation. PURPOSE: To compare torque and neuromuscular activation before and after sessions of HL knee extension exercise and high-velocity BFR knee extension exercise in young and older adults. METHODS: Ten young males and females (20.3+1.5 years, 1.73+.06 m, 69.2+10.4 kg) and 10 older males and females (72.6+4.7 years, 1.70+.12 m, 74.3+14.6 kg) performed randomized sessions of HL (80% 1-RM for 3 sets of 10 isotonic knee extension repetitions) and low-load, high-velocity BFR (30% 1-RM coupled with a vascular restriction for one set of 30 knee extension repetitions and 3 sets of 15 repetitions completed as quickly as possible). Knee extension isometric torque was assessed before and after each session of exercise and neuromuscular activation of the vastus lateralis (VL) was quantified with surface electromyography (EMG). RESULTS: The young participants had higher isometric torque than the older participants (213.4+54.8 vs 160.1+56.3 Nm; P=.01). There was an average decrement in torque of 31.4+9.2% among all participants from baseline to post exercise (P<.01). The magnitude of this decrement was similar between conditions (P=.19), age (P=.12), and the interaction of time, condition and age (P=.16). EMG amplitude normalized to pre isometric torque in the first 5 knee extension repetitions of the HL condition averaged 106+57% and 90+33% in the BFR high-velocity condition. In the last 5 repetitions, EMG amplitude averaged 117+56% and 113+46 in the HL and BFR conditions respectively. This was a significant increase in EMG amplitude (P<.01) but there were no interactions or main effects of condition or age (P>.05). CONCLUSION: Combing high-velocity contractions with BFR resistance exercise results in decrements in torque and heightened neuromuscular activation similar to HL exercise in both young and older adults. Future studies should evaluate the training adaptations from high-velocity BFR resistance training. Supported by University of New Hampshire Grimes Family Fund.