The purpose of this work was to determine endothelial, microvascular, skeletal muscle oxidative capacity (SMOC) and cardiorespiratory responses to an acute bout of continuous single leg cycling (SLC) and double leg cycling (DLC). Ten recreationally active men and women volunteered to participate in this investigation and reported to the laboratory on four separate occasions. Visits 1 and 2 consisted of a DLC and SLC V ̇ O 2 peak ${\dot V_{{{\mathrm{O}}_2}{\mathrm{peak}}}}$ test, while visits 3 and 4 were the experimental visits. Participants performed 30 min of continuous DLC and SLC at 60% of their DLC V ̇ O 2 peak ${\dot V_{{{\mathrm{O}}_2}{\mathrm{peak}}}}$ . Before, 1 and 2 h post-exercise, measures of vascular (i.e., flow mediated dilation (FMD), reactive hyperaemia, microvascular responsiveness) and SMOC were performed. SLC resulted in significantly greater limb specific power (83 ± 23 vs. 51 ± 12 W; P < 0.001) and carbohydrate oxidation (151 ± 40 vs. 126 ± 30 kcal; P = 0.017) compared to DLC. There was a significant reduction in % FMD following SLC (baseline: 9.4 ± 3.2%; 1 h: 6.9 ± 3.4%; P = 0.009), while there was no change following DLC. Both SLC and DLC resulted in a significant increase in SMOC (P < 0.001) and a significant decrease in microvascular responsiveness (P < 0.001). In conclusion, the reduction in FMD following SLC, likely brought on by greater peripheral and oxidative stress, which are key stimuli for long-term positive adaptations, may be more beneficial at improving peripheral adaptations compared to DLC. This may be particularly advantageous for those with exercise intolerance, as SLC leads to greater peripheral stress for a similar central stress.

Single leg emphasis cycling (SLEC) has the potential to be beneficial in the rehabilitation setting; however, the metabolic responses to it are unknown. Thus, the current investigation sought to evaluate the metabolic and blood flow responses of SLEC compared to traditional double leg cycling (DLC) and single leg cycling (SLC). This was a within-participant randomized controlled trial where 12 recreationally active participants completed three different cycling modalities (DLC, SLC and SLEC) at 20%, 35% and 50% of power associated with DLC V ̇ O 2 peak ${{\dot{V}}_{{{{\mathrm{O}}}_2}{\mathrm{peak}}}}$ (Pα). Gas exchange ( V ̇ O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_2}}}$ and V ̇ C O 2 ${{\dot{V}}_{{\mathrm{C}}{{{\mathrm{O}}}_2}}}$ ) was monitored continuously during exercise and rating of perceived exertion (RPE) for the active leg and whole body (WB) was recorded in the last minute of each stage, and blood flow was recorded in the femoral artery immediately following each stage using Doppler ultrasound. Despite similar V ̇ O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_2}}}$ across the three conditions, carbohydrate oxidation was greater during SLEC compared to DLC at 20%, 35% and 50% (P ≤ 0.047) but, lower than SLC at 35% and 50% Pα (P ≤ 0.011). Similarly, blood flow was greater during SLEC compared to DLC at 20%, 35% and 50% (P ≤ 0.010), but lower than SLC at 35% and 50% Pα (P ≤ 0.008). There were no differences in WB or leg RPE between SLEC and DLC across all intensities. The current investigation suggests that SLEC could be an alternative and applicable cycling modality for individuals to increase local metabolic stress for similar levels of exertion and whole-body metabolic demand.

Electrical stimulation (ES) is used in rehabilitation to enhance circulation and muscle activation, but its effects on vascular function and fatigue compared with voluntary (VOL) exercise remain unclear. This study examined acute and short-term neuromuscular and vascular responses to higher-frequency ES and force-matched VOL isometric knee extensions. Eleven healthy adults (5 women; 23 ± 4 years) completed two interventions in a crossover design: 40 isometric ES contractions at a pain-tolerated threshold and 40 force-matched VOL contractions, separated by a 14-day washout. Outcomes included force, heart rate (HR), superficial femoral artery (SFA) blood flow, vascular conductance, oscillatory shear stress (OSS), muscle oxygenation via near-infrared spectroscopy, femoral-popliteal pulse wave velocity (fpPWV), and flow-mediated dilation (FMD), assessed before, during, and up to 48 h post-exercise. Force declined more rapidly during ES, with greater strength loss at 24 and 48 h (p = 0.01) and increased soreness at 1, 24, and 48 h (p ≤ 0.04). HR was higher during ES until approximately contraction 20 (p < 0.05). Net SFA blood flow was consistently greater with ES (p < 0.01), while VOL produced greater retrograde flow (p < 0.01) and OSS (p = 0.02). Total hemoglobin was higher during ES at earlier contractions (p = 0.01). No significant changes were observed in FMD (p ≥ 0.06) or fpPWV (p = 0.59). Higher-frequency ES increases blood flow and reduces OSS compared with force-matched VOL contractions, at the cost of greater fatigue and soreness. These findings suggest ES may offer circulatory benefits relevant to rehabilitation, though optimal parameters are needed to minimize neuromuscular strain.

The upper limits for total energy expenditure (TEE) and water turnover (rH2O) in humans have been reported during several continuous single-day ultraendurance races (running, cycling, and triathlon). Currently, the upper limits for TEE and rH2O during continuous single-day activity in cold weather (<0 °C) remain unknown. The Arrowhead Ultra is one of the coldest ultraendurance races in North America and provides a unique opportunity to answer these questions. Racers select a bicycle, cross-country skis, or foot travel to traverse a 214-km snow-covered trail (altitude range: 345-426 m; 2,030-m elevation gain). Historically, approximately one-half of the racers complete the event. In this case study, we assessed TEE and rH2O from the racer [cyclist: age: 22 yr; height: 1.84 m; body mass: 87.7 kg; and maximal oxygen consumption (V̇o2max): 5.0 LO2·min-1] who won the 2025 Arrowhead Ultra (17.9 h; -13 to -1 °C) using the doubly labeled water method. Total energy and fluid intake were recorded to assess energy and fluid balance. Mean heart rate was 141 beats·min-1 (71% of maximum heart rate). TEE was 63.9 MJ (15,273 kcal; 9.6 times basal metabolic rate) while total energy intake was 33.2 MJ (7,941 kcal). Mean carbohydrate intake was 88 g·h-1. Water turnover was 17.7 L, yielding a rH2O/TEE ratio of 0.28 L·MJ-1 for the race. The cyclist demonstrated high TEE and rH2O that were comparable to values from other ultraendurance athletes competing in a range of temperatures (3-34°C). Notably, rH2O from this cyclist was higher compared to athletes performing other ultratype endeavors in cold weather conditions (-25 to -19 °C). Our observations shed light on energy and fluid demands during continuous single-day activity in the cold and have endurance training and performance implications.NEW & NOTEWORTHY In this short report, we detail new data on the upper limits of human energy expenditure (9.6 times basal metabolic rate) and water turnover (10.5 L·12 h-1) during continuous single-day exercise in the cold. Our results indicated elevated energy use, and impressively, water turnover comparable to exercise in warmer conditions. These findings have implications for training and endurance performance of strenuous exercise in cold weather environments.

We compared predictors of lower-limb arterial occlusion pressure (AOP) across commonly used blood flow restriction (BFR) cuff widths (11, 13, 18 cm) and developed prediction equations to estimate AOP for each cuff. Participants (n = 116) underwent measurements of thigh circumference (TC), systolic (SBP) and diastolic (DBP) blood pressure, and AOP was assessed using Doppler ultrasound in a seated position. Multiple linear regression models with commonality analysis and mixed-effects models were used to identify and compare predictors of AOP between each cuff. LASSO regression with bootstrap resampling was used to develop and internally validate prediction equations. TC, SBP, DBP, age, and sex explained 60%–70% of total variance in AOP, with greater predictive power in narrower cuffs. As cuff width increased, TC uniquely accounted for less (36%, 26%, 11% for 11, 13, 18 cm, respectively) and SBP uniquely accounted for more (2%, 6%, 12% for 11, 13, 18 cm, respectively) variance. A cuff width × TC interaction indicated that limb size had greater influence on AOP with narrower cuffs. In contrast, the relationship between SBP and AOP remained stable across cuff widths. Prediction equations demonstrated good predictability and calibration, with limits of agreement ranging from ±18.4 to ±28.6 mmHg and statistical equivalence between predicted and measured AOP. Internal validation showed minimal overfitting. These findings highlight the importance of accounting for cuff width in BFR pressure prescription, with narrower cuffs requiring consideration primarily of TC, and wider cuffs requiring consideration of both TC and SBP. These cuff-specific equations may offer a practical alternative to direct AOP measurement.

INTRODUCTION:While both voluntary (VOL) and electrically stimulated (ES) contractions increase blood flow, ES induces greater oxidative stress, raising the risk of exercise induced muscle damage (EIMD), which can impair vascular function, and oxygen utilization. PURPOSE:We examined how ES and force-matched VOL contractions impact microvascular function and muscle oxidative capacity. METHOD:Utilizing a cross-over design, 16 healthy adults performed 40 isometric knee extensions (KE) via ES and VOL contractions. The following variables were assessed at baseline, 1 h, 24 h, and 48 h postexercise: knee extensor strength and soreness, microvascular function (hyperemic response to single passive leg movement (sPLM), and skeletal muscle oxidative capacity (SMOC) of the vastus lateralis. RESULT:Maximal voluntary contraction (MVC) was lower following ES than VOL at 24 h (324.7 ± 125.8 vs. 366.8 ± 125.6 N, p = 0.01) and 48 h (308.5 ± 124.7 vs. 379.0 ± 129.0 N, p = 0.001). Soreness (p ≤ 0.02) and muscle swelling (p ≤ 0.02) were greater after ES. Vascular function, quantified as the AUC for total hyperemic response following sPLM and measured by Doppler/ultrasound, was reduced following ES at 1 h (p = 0.01) and 24 h (p = 0.002). SMOC was more impaired after ES than VOL (p ≤ 0.03). There was a 31% decrease in oxygen recovery rate 1-h post-ES, with an additional 10% decline at 24-h and 48-h (p ≤ 0.03) compared to VOL. CONCLUSION:ES seemed to elicit EIMD, resulting in reduced MVC, impaired recovery, while affecting microvascular function and oxidative capacity.

IntroductionExercise with blood flow restriction (BFR) has gained popularity for use with a wide range of healthy and clinical populations. However, several factors including medical screening, selection of equipment, and determination of cuff pressure still pose barriers for implementation. Accordingly, this study aimed to develop and test a web-based application to guide practitioners in using BFR safely and effectively.MethodsFirst, we developed an application to assist with medical screening, selection of appropriate equipment, and determination of cuff pressures. Subsequently, we conducted preliminary usability testing of the application using a mixed methods approach. Licensed physical therapists (n = 5) with no prior experience with BFR used the application to implement BFR exercise in hypothetical patient scenarios. Afterward, perceived usability was assessed using the System Usability Scale (SUS) and semi-structured interviews analyzed through thematic analysis.ResultsAll task scenarios were successfully completed in an average time of 2.3 ± 1.2 min. A total of 11 errors occurred, including minor navigation issues (4), data input problems (2), and difficulty interpreting recommendations (5). The composite SUS score was 94 ± 5, ranking highly compared to industry standards. Interviews revealed that the application was efficient, boosted confidence in using BFR, and increased the perceived likelihood of incorporating BFR into clinical practice.DiscussionThese findings suggest that the web-based application has potential to serve as a valuable tool for overcoming barriers to BFR use, enhancing accessibility, and improving the safety and effectiveness of BFR implementation in clinical settings.

https://youtu.be/Jm8BVwM0X54 INTRODUCTION The purpose of this study was to evaluate the effects of high-intensity interval training (HIIT) at normobaric hypoxia (NH) on measures of hemodynamics. METHODS Ten active adults aged 23±1 years volunteered to complete a HIIT intervention at a randomized condition (sea level (SL); low NH (900m); moderate NH (2500m), high NH (4300m)) separated by 72 hours. After acclimating to the condition for 45 minutes (Rest), participants completed a HIIT intervention consisting of six bouts of high-intensity cycling separated by three minutes and 30 seconds of active recovery (AR). Hemodynamic variables included systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), and rate pressure product (RPP). They were assessed at Rest, during the final AR (AR6), and five minutes following the final bout of exercise (Post). A two-way repeated analysis of variance (ANOVA) was used to analyze the effects of condition (SL, 900m, 2500m, 4300m) across the repeated factor of time (Rest, AR6, Post) in response to HIIT. RESULTS There was a significant (p≤0.05) main effect of time for HR, SBP, DBP, MAP, PP, and RPP. At all conditions, HR (SL: Rest: 62±9bpm; AR6: 156±21bpm; Post: 104±15bpm; 900m: Rest: 61±10bpm; AR6: 161±10bpm; Post: 109±19bpm; 2500m: Rest: 64±11bpm; AR6: 167±14bpm; Post: 104±14bpm; 4300m: Rest: 67±14bpm; AR6: 171±11bpm; Post: 111±19bpm) increased following Rest, and AR6 was greater than Post. Additionally, at all conditions, SBP (SL: Rest: 116±7mmHg; AR6: 154±16mmHg; Post: 134±13mmHg; 900m: Rest: 119±8mmHg; AR6: 152±10mmHg; Post: 133±13mmHg; 2500m: Rest: 120±10mmHg; AR6: 153±12mmHg; Post: 136±14mmHg; 4300m: Rest: 116±10mmHg; 4300m AR6: 149±15mmHg; Post: 136±14mmHg) increased following Rest. More so, MAP at Rest was lower than AR6 and Post at SL (Rest: 66±5mmHg; AR6: 69±7mmHg; Post: 60±2mmHg) and 900m (Rest: 68±5mmHg; AR6: 70±8mmHg; Post: 68±7mmHg). At AR6, MAP was higher than Post at 900m. Similarly, PP (SL: Rest: 50±7mmHg; AR6: 85±15mmHg; Post: 64±15mmHg; 900m: Rest: 51±7mmHg; AR6: 82±10mmHg; Post: 63±11mmHg; 2500m: Rest: 48±6mmHg; AR6: 85±14mmHg; Post: 66±10mmHg; 4300m: Rest: 44±6mmHg; AR6: 77±14mmHg; Post: 63±11mmHg) was augmented following Rest at all conditions, and AR6 was higher than Post at SL, at 900m. Finally, RPP (SL: Rest: 71±13mmHg; AR6: 216±42mmHg; Post: 139±21mmHg; 900m: Rest: 73±15mmHg; AR6: 204±34mmHg; Post: 145±28mmHg; 2500m: Rest: 78±17mmHg; AR6: 202±30mmHg; Post: 141±22mmHg; 4300m: Rest: 79±21mmHg; AR6: 208±30mmHg; Post: 152±31mmHg) increased following Rest, and Post was lower than AR6, at all conditions. No other significant main effects, conditions, or interactions were observed. CONCLUSIONS While both NH and HIIT increase measures of hemodynamics, combining HIIT and NH does not further augment such variables. Thus, engaging in HIIT at NH does not increase cardiovascular stress or the risk of experiencing a cardiovascular event compared to HIIT at SL.

PurposeElectrical stimulation-induced muscle contractions in individuals with paralyzed muscles are often associated with early-onset fatigue. We examined whether electrical stimulation of the quadriceps muscle results in vasoconstriction and a reduction in blood flow, which may contribute to this early-onset fatigue.MethodsSeventeen young individuals completed 40 electrical stimulation isometric contractions (stimulation frequency of 75 Hz, pulse duration of 400 mu s, on-off ratio 6.0-20 secs) and force matched voluntary isometric contractions. Isometric force, heart rate, blood pressure, superficial femoral diameter, and blood velocity were measured at baseline and during exercise (contractions 1, 5, 10, 15, 20, 25, 30, 35, and 40). Net, antegrade, and retrograde blood flow, and conductance were quantified. Two-way, within-subjects analyses of variance were used to evaluate diameter, blood flow, and conductance.ResultsDiameter was not different between electrical stimulation and voluntary (P = 0.57). Net blood flow increased during both conditions with the greatest blood flow occurring during electrical stimulation compared to voluntary (P <= 0.01). Electrical stimulation showed a greater increase antegrade and reduced retrograde flow compared to voluntary. After the twentieth contraction, electrical stimulation also elicited greater conductance than voluntary (P <= 0.049).ConclusionsThe use of neuromuscular electrical stimulation to elicit muscle contractions does not result in vasoconstriction or a reduced hyperemic response compared to volitional contractions.

Compared to traditional methods, near-infrared spectroscopy (NIRS) provides a relatively cheap and easy-to-use noninvasive technique to measure skeletal muscle oxygen uptake following exercise. This laboratory not only enables students to learn about the basics of NIRS and muscle energetics but also addresses more complex questions regarding skeletal muscle physiology.

Previous investigators have developed prediction equations to estimate arterial occlusion pressure (AOP) for blood flow restriction (BFR) exercise. Most equations have not been validated and are designed for use with expensive cuff systems. Thus, their implementation is limited for practitioners. To develop and validate an equation to predict AOP in the lower limbs when applying an 18 cm wide thigh sphygmomanometer (SPHYG18cm). Healthy adults (n = 143) underwent measures of thigh circumference (TC), skinfold thickness (ST), and estimated muscle cross-sectional area (CSA) along with brachial and femoral systolic (SBP) and diastolic (DBP) blood pressure. Lower-limb AOP was assessed in a seated position at the posterior tibial artery (Doppler ultrasound) using a SPHYG18cm. Hierarchical linear regression models were used to determine predictors of AOP. The best set of predictors was used to construct a prediction equation to estimate AOP. Performance of the equation was evaluated and internally validated using bootstrap resampling. Models containing measures of either TC or thigh composition (ST and CSA) paired with brachial blood pressures explained the most variability in AOP (54

Exercise with reduced muscle mass facilitates greater muscle-specific adaptations than training with larger muscle mass. The smaller active muscle mass can demand a greater portion of cardiac output which allows muscle(s) to perform greater work and subsequently elicit robust physiological adaptations that improve health and fitness. One reduced active muscle mass exercise that can promote greater positive physiological adaptations is single-leg cycling (SLC). Specifically, SLC confines the cycling exercise to a smaller muscle mass resulting in greater limb specific blood flow (i.e., blood flow is no longer "shared" by both legs) which allows the individual to exercise at a greater limb specific intensity or for a longer duration. Numerous reports describing the use of SLC have established cardiovascular and/or metabolic benefits of this exercise modality for healthy adults, athletes, and individuals living with chronic diseases. SLC has served as a valuable research tool for understanding central and peripheral factors to phenomena such as oxygen uptake and exercise tolerance (i.e., V̇O2peak and V̇O2 slow component). Together, these examples highlight the breadth of applications of SLC to promote, maintain, and study health. Accordingly, the purpose of this review was to describe: 1) acute physiological responses to SLC, 2) long-term adaptations to SLC in populations ranging from endurance athletes to middle aged adults, to individuals living with chronic disease (COPD, heart failure, organ transplant), and 3) various methods utilized to safely perform SLC. A discussion is also included on clinical application and exercise prescription of SLC for the maintenance and/or improvement of health.

PURPOSE: To compare the recovery rate of mitochondria following electrically stimulated (ES) and voluntary (VOL) skeletal muscle contractions. METHODS: Ten recreationally active men and women (27 ± 3.3 years; 171.7 ± 5.5 cm; 77.2 ± 12.6 kg; 0.93 ± 0.46 cm lower limb adipose tissue thickness) volunteered to participate in this investigation. Participants were seated in a recumbent position with the right knee fully extended and ankle supported at 90o. The foot was attached to a force transducer and a blood pressure cuff was applied above the knee joint. A near-infrared spectroscopy (NIRS) device was placed on the posterior mid-line of the tibia at the largest circumference of the gastrocnemius. ES pads were placed directly superior and inferior to the NIRS device. Participants performed fifteen seconds of ES plantar flexion (2 Hz with 60amps at a pulse duration of 500 μs). Immediately after exercise six repeated arterial occlusions were performed. Each occlusion lasted 5 seconds(s) and was followed by 5 s of recovery. After five minutes of rest the procedure was repeated with VOL contractions with real time feedback so they could match forces produced during ES. Recovery slopes and rate constants were calculated to determine the proficiency of the mitochondria to return the rate of oxygen consumption to baseline. A maximum ischemic calibration and blood volume correction was performed. RESULTS: No significant differences were observed between ES (2.11 ± 1.01) and VOL (1.47 ± 1.22) rate constants. There was a significant interaction (f = 13.85, p < 0.001), main effect of condition (f = 28.72, p < 0.001) and main effect of time (f = 24.11, p < 0.001). Post-hoc testing revealed significant differences in slope recovery between ES and VOL contractions at all time points: Immediately (4.05 ± 2.07 v. 0.83 ± 0.35; p < 0.001), 10s (2.29 ± 1.06 v. 0.58 ± 0.33; p = 0.001), 20s (1.8 ± 0.95 v. 0.53 ± 0.32; p = 0.002), 30s (1.32 ± 0.79 v. 0.40 ± 0.21; p = 0.004), 40s (1.14 ± 0.52 v. 0.45 ± 0.22; p = 0.002) and 50s (1.01 ± 0.30 v. 0.41 ± 0.22; p < 0.001) after cessation of contractions. CONCLUSION: No significant differences were observed in the rate of recovery. However, ES contractions evoked a larger magnitude of recovery due to a greater rate of oxygen consumption.

Accumulating evidence indicates that some COVID-19 survivors display reduced muscle mass, muscle strength, and aerobic capacity, which contribute to impairments in physical function that can persist for months after the acute phase of illness. Accordingly, strategies to restore muscle mass, muscle strength, and aerobic capacity following infection are critical to mitigate the long-term consequences of COVID-19. Blood flow restriction (BFR), which involves the application of mechanical compression to the limbs, presents a promising therapy that could be utilized throughout different phases of COVID-19 illness. Specifically, we hypothesize that: 1) use of passive BFR modalities can mitigate losses of muscle mass and muscle strength that occur during acute infection and 2) exercise with BFR can serve as an effective alternative to high-intensity exercise without BFR for regaining muscle mass, muscle strength, and aerobic capacity during convalescence. The various applications of BFR may also serve as a targeted therapy to address the underlying pathophysiology of COVID-19 and provide benefits to the musculoskeletal system as well as other organ systems affected by the disease. Consequently, we present a theoretical framework with which BFR could be implemented throughout the progression from acute illness to outpatient rehabilitation with the goal of improving short- and long-term outcomes in COVID-19 survivors. We envision that this paper will encourage discussion and consideration among researchers and clinicians of the potential therapeutic benefits of BFR to treat not only COVID-19 but similar pathologies and cases of acute critical illness.

PURPOSE: To examine indirect markers of muscle damage and vessel stiffness following force matched volitional and electrically stimulated (ES) isometric contractions of the knee extensors. METHODS: Thirteen recreationally active men and women (n = 6), (26.2 ± 2.1 yrs; 178.2 ± 6.5 cm; 75.4 ± 8.3 kg) participated in two different isometric knee extension protocols (40 x 6 sec. contractions with 20 sec. recovery). Condition 1 involved the use of electrical stimulation (ES) to generate muscle contractions and condition 2 involved voluntary (VOL) force matched contractions. For the ES condition, stimulating electrodes were placed over the vastus lateralis and rectus femoris muscles (stimulation parameters: 75 Hz, 400 pulse width, and intensity set to the highest tolerable limit). Repeated measures ANOVAs were used to examine condition-and time-based differences in femoral artery pulse wave velocity (PWV), maximal muscle strength (MVC), perceived soreness (VAS), and total muscle size (mCSA) prior to exercise (baseline), and then 1-, 24-, and 48-h after exercise. RESULTS: There were significant condition x time interactions for MVC (p < 0.01), in which MVC was significantly lower after ES compared to VOL (359 ± 35 N vs. 389 ± 34 N; p = 0.04). MVC was lowest at 48H following ES (339 ± 129 N vs. 411 ± 130 N; p < 0.01), with no difference after VOL across time (p > 0.05). There were also significant condition x time interactions for perceived soreness (p < 0.01), where perceived soreness was greater than baseline at all time points (p ≥ 0.01) after ES compared VOL. ES resulted in the largest increase from baseline at 48-h (24.7 ± 16.8 mm). There were significant condition x time interactions for mCSA (p < 0.01), where mCSA was significantly larger after ES as compared to VOL (37.1 ± 9.3 cm2 vs. 36.1 ± 9.1 cm2; p < 0.01), After ES, mCSA increased from baseline to 48H (36.0 ± 9.4 cm2 vs. 38.0 ± 9.6 cm2; p < 0.01). For PWV, there was also a significant main effect of condition (p = 0.04) and time (p < 0.01) but not their interaction (p = 0.09). Across all timepoints PWV was faster after ES compared to VOL (26.8 ± 11.5 cm/s vs. 20.4 ± 6.0 cm/s; p = 0.04). CONCLUSIONS: ES isometric contractions reduced knee extensor strength, increased soreness, induced swelling, and resulted in greater vessel stiffness compared to force matched volitional contractions.

For implementation of exercise with blood flow restriction (BFR), cuff pressures should be based on arterial occlusion pressure (AOP). Limb circumference and blood pressure have been identified as predictors of AOP and used to set appropriate exercising cuff pressures. However, it is unclear whether these predictors are consistent across BFR cuffs of varying width. Our purpose was to compare predictors of lower-body AOP in a variety of commonly utilized cuff widths. We hypothesized that limb circumference would be a stronger predictor when using narrower cuffs while blood pressure would be a stronger predictor when using wider cuffs.Healthy normotensive adults (women=44, men=76; age:23±4yrs; BMI:25±4) underwent measurements of thigh circumference (TC) and systolic (SBP) and diastolic blood pressure (DBP). Lower-body AOP was assessed (via Doppler ultrasound) in the post-tibial artery in a seated position with an 11, 13, and 18cm wide pneumatic cuff. Models of hierarchical linear regression were constructed to predict AOP in each of the cuffs using TC, SBP, and DBP as predictor variables. A linear mixed effects model including AOP as the outcome variable was fit. The model included fixed effects of TC, SBP, DBP, cuff width, TC x cuff width, SBP x cuff width, and DBP x cuff width, and a random intercept for participants.AOP was 188±28, 170±20, and 152±15mmHg, for the 11, 13, and 18cm cuff, respectively. For the 11cm cuff, TC (β = 0.66, part = 3.46), SBP (β = 0.17, part = 0.48), and DBP (β = 0.21, part = 3.46) were significant predictors that explained 74% of AOP variability. For the 13cm cuff, TC (β = 0.56, part = 2.06), SBP (β = 0.25, part = 0.48), and DBP (β = 0.22, part = 0.59) were significant predictors that explained 69% of AOP variability. In the 18cm cuff, TC (β = 0.35, part = 0.10) and SBP (β = 0.48, part = 0.72) were significant predictors that explained 57% of the AOP variability. There were significant main effects of TC, SBP, DBP, and cuff width on AOP, and significant interactions of TC x cuff width and SBP x cuff width (all P<0.05). Results indicated that when using a narrow cuff, AOP was largely based on TC and when using a wider cuff, AOP was based mostly on SBP. Differences are likely due to wider cuffs transmitting pressures more efficiently into underlying soft tissues, thereby reducing the influence of TC on AOP and shifting greater influence towards blood pressure. Our results support and expand on previous work in a small sample (n=12) reporting that AOP depends more on TC as cuff width decreases. Together, these data provide evidence that cuff width should be considered when selecting factors to estimate AOP and establish appropriate pressures during lower-body BFR exercise. This work was supported by the Michigan Tech Health Research Institute This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Lower-body aerobic exercise with blood flow restriction (BFR) offers a unique approach for stimulating improvements in muscular function and aerobic capacity. While there are more than 40 reports documenting acute and chronic responses to lower-body aerobic exercise with BFR, responses to upper-body aerobic exercise with BFR are not clearly established. We evaluated acute physiological and perceptual responses to arm cranking with and without BFR. Participants (N = 10) completed 4 arm cranking (6 × 2 min exercise, 1 min recovery) conditions: low-intensity at 40