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We tested the hypothesis that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Fourteen patients with treated hypertension (age 69 ± 11 years, 136 ± 12/80 ± 11 mmHg; mean ± SD) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2 µg kg-1 min-1) to inhibit the peripheral chemoreflex, at baseline, during isocapnic hypoxic rebreathing and during rhythmic handgrip exercise (3 min, 50% maximum voluntary contraction). At baseline, dopamine did not change mean blood pressure (95 ± 10 vs. 98 ± 10 mmHg, P = 0.155) but increased brachial artery blood flow (59 ± 20 vs. 48 ± 16 ml min-1, P = 0.030) and vascular conductance (0.565 ± 0.246 vs. 0.483 ± 0.160 ml min-1 mmHg-1; P = 0.039). Dopamine attenuated the increase in mean blood pressure (∆3 ± 4 vs. ∆8 ± 6 mmHg, P = 0.007) to isocapnic hypoxic rebreathing and reduced peripheral chemoreflex sensitivity by 28 ± 37% (P = 0.044). Rhythmic handgrip exercise induced increases in brachial artery blood flow and vascular conductance (both P < 0.05 vs. rest after 45 s) that were greater with dopamine than saline (e.g. Δ76 ± 54 vs. Δ60 ± 43 ml min-1 and Δ0.730 ± 0.440 vs. Δ0.570 ± 0.424 ml min-1 mmHg-1, respectively, at 60 s; main effect of condition both P < 0.0001). Our results indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow and vascular conductance increases to exercise in treated human hypertension. KEY POINTS: It was hypothesised that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Treated patients with hypertension (n = 14) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2 µg kg-1 min-1) to inhibit the peripheral chemoreflex. Low-dose dopamine reduced resting ventilation and peripheral chemoreflex sensitivity, and while mean blood pressure was unchanged, brachial artery blood flow and vascular conductance were increased. Low-dose dopamine augmented the brachial artery blood flow and vascular conductance responses to rhythmic handgrip. These findings indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow, and vascular conductance increases to exercise in treated human hypertension.

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The purpose of this study was to examine the test-retest reliability of strength-endurance protocols using isometric mid-thigh pull (IMTP). Twenty-eight participants (23.2 ± 4.9 years) completed two protocols across four testing sessions. Protocol one consisted of 10 maximal IMTP tests lasting 5 seconds each with 10 seconds rest between. Protocol two consisted of a prolonged 60 second maximal IMTP. Data from protocol 1 was analysed in two ways; (a) use of the highest peak value from the first three IMTP efforts, and the lowest peak value from the final three IMTP efforts, and (b) use of the mean peak force from the first three IMTP efforts and mean peak force from the final three IMTP efforts. Data from protocol two used the highest and lowest peak values in the first- and final-15 seconds. Analyses revealed excellent reliability for peak force across all four testing sessions (ICC = 0.94), as well as good test-retest reliability for strength-endurance for protocol 1 (a; ICC = 0.81, b; ICC = 0.79). Test-retest reliability for protocol 2 was poor (ICC = 0.305). Bland-Altman bias values were smaller for protocol 1(a = -8.8 Nm, b = 21.7 Nm) compared to protocol 2 = (119.3 Nm). Our data suggest that 10 maximal IMTP tests performed as described herein is a reliable method for exercise professionals to assess both peak force and strength-endurance in a single, time-efficient protocol.

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Type 2 diabetes (T2D) is often accompanied by hypertension, exaggerated blood pressure (BP) responses to sympatho-excitatory stressors, and raised cardiovascular disease risk. Appropriate respiratory-sympathetic coupling and sympathetic transduction to BP are important for short- and longer-term BP control. We tested the hypotheses that respiratory modulation of muscle sympathetic nerve activity (MSNA) and its transduction to BP would be impaired in T2D and associated with higher BP and respiratory-coupled BP variability. Resting MSNA, respiration and beat-to-beat BP were recorded in 20 T2D (49.1 ± 7.4 years; mean ± SD) and 13 healthy control (46.3 ± 9.4 years) participants. MSNA and the transduction of sympathetic bursts (signal-averaging) to mean arterial pressure (MAP) were compared at low and high lung volume phases. The peak MAP response following a sympathetic burst was lower during the high lung volume than low lung volume phase in controls (P = 0.005), whereas it was unchanged with phase in T2D participants (P = 0.522). Respiratory modulation of MSNA was impaired in T2D participants, who had an attenuated reduction in burst incidence from low to the high lung volume phase, versus controls (27.8 ± 38.4% vs. 49.4 ± 24.6%, respectively; P = 0.043). The T2D participants were grouped into unimpaired respiratory modulators (burst incidence modulation median or above) or impaired respiratory modulators (below median). Impaired modulators had higher systolic BP (133 ± 14 vs. 121 ± 11 mmHg, P = 0.046), greater Traube-Hering wave amplitudes (6.3 ± 2.4 vs. 4.6 ± 1.1 mmHg; P = 0.028) and higher BP variability (MAP average real variability, 2.0 ± 0.7 vs. 1.4 ± 0.3, P = 0.033). Respiratory modulation of MSNA and sympathetic transduction to BP are altered in T2D patients and may contribute to their increased hypertension and cardiovascular risk. KEY POINTS: Respiratory-sympathetic coupling and sympathetic transduction to blood pressure (BP) contribute to short- and longer-term BP control. Our understanding of these processes in health and type 2 diabetes (T2D), a condition with high prevalence of hypertension and cardiovascular risk, is incomplete. We found that respiration and sympathetic transduction to BP are coupled in healthy individuals. The mean arterial pressure response to a sympathetic burst was reduced during the high lung volume compared to the low lung volume phase. This coupling was absent in T2D. Respiratory modulation of muscle sympathetic nerve activity (MSNA) is impaired in T2D, with a blunted reduction of MSNA observed during the high lung volume phase. T2D patients with impaired respiratory MSNA modulation had augmented systolic BP, respiratory-related BP excursions (Traube-Hering waves) and BP variability. Abnormal respiratory modulation of MSNA and sympathetic transduction to BP in T2D may contribute to altered blood pressure control and cardiovascular risk in this population.

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Atrial fibrillation (AF) and hypertension (HTN) are both associated with impaired cerebrovascular carbon dioxide reactivity (CVRCO2), an indicator of cerebral vasodilatory reserve. We hypothesised that CVRCO2 would be lower in patients with both AF and HTN (AF + HTN) compared to normotensive AF patients, due to an additive effect of AF and HTN on CVRCO2. Forty AF (68 ± 9 years) and fifty-seven AF + HTN (68 ± 8 years) patients underwent transcranial Doppler ultrasound measurement of middle cerebral artery blood velocity (MCA Vm) during stepped increases and decreases in end-tidal carbon dioxide (PETCO2). A cerebrovascular conductance index (CVCi) was calculated as the ratio of MCA Vm and mean arterial pressure (MAP). CVRCO2 was determined from the linear slope for MCA Vm and MCA CVCi vs PETCO2. Baseline MAP was higher in AF + HTN than AF (107 ± 9 vs. 98 ± 9 mmHg, respectively; p < 0.001), while MCA Vm was not different (AF + HTN:49.6 [44.1-69.0]; AF:51.7 [45.2-63.3] cm.s-1; p = 0.075), and CVCi was lower in AF + HTN (0.46 [0.42-0.57] vs. 0.54 [0.44-0.63] cm.s-1.mmHg-1; p < 0.001). MCA Vm CVRCO2 was not different (AF + HTN: 1.70 [1.47-2.19]; AF 1.74 [1.54-2.52] cm/s/mmHg-2; p = 0.221), while CVCi CVRCO2 was 13% lower in AF + HTN (0.013 ± 0.004 vs 0.015 ± 0.005 cm.s-1.mmHg-1; p = 0.047). Our results demonstrate blunted cerebral vasodilatory reserve (determined as MCA CVCi CVRCO2) in AF + HTN compared to AF alone. This may implicate HTN as a driver of further cerebrovascular dysfunction in AF that may be important for the development of AF-related cerebrovascular events and downstream cognitive decline. We demonstrated reduced cerebrovascular CO2 responsiveness in atrial fibrillation with hypertension (AF+HTN) vs. atrial fibrillation (AF). Furthermore, AF per se (as opposed to normal sinus rhythm) predicts reduced cerebrovascular CO2 responsiveness. Our findings suggest additional cerebrovascular dysfunction in AF+HTN vs. AF.

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BACKGROUND: Exertional dyspnoea, a cardinal symptom in interstitial lung disease (ILD), can be objectively measured during a 6-min walk test (6MWT) using the Borg Dyspnoea Score (BDS). However, the clinical utility of this measurement is unclear. The purpose of this systematic review was to determine the association between 6MWT BDS and prognosis (mortality and lung transplantation), other 6MWT variables and measures of pulmonary function. METHODS: MEDLINE, EMBASE, Cochrane and SCOPUS databases were used to identify studies reporting an association between post-6MWT BDS and the relevant outcomes in adults with ILD. Language was limited to English. Study quality was assessed using the Quality in Prognosis Study risk of bias tool. A narrative synthesis for each outcome was performed. RESULTS: Ten full-text studies (n = 518) were included. Four studies had high overall risk of bias. Two studies (n = 127) reported prognosis and both found that higher 6MWT BDS was associated with increased all-cause mortality. However, the certainty of evidence was very low due to study design and likely publication bias. Higher post-6MWT BDS may be associated with shorter, or no effect on 6MWD; and lower pulmonary function. There was insufficient evidence that BDS correlated with 6MWT oxygen saturation. CONCLUSIONS: Post-6MWT BDS has a potential role as a predictor of all-cause mortality in ILD, 6MWD and lower pulmonary function. Larger studies designed to confirm these relationships and assess the independent association between the 6MWT BDS and clinical outcomes are required.

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INTRODUCTION: Atrial fibrillation (AF) is associated with endothelial damage/dysfunction. Herein, we tested the hypothesis that brachial artery flow-mediated dilation (FMD) is superior in AF patients taking apixaban compared to warfarin. METHODS: AF patients on apixaban (n = 46; 67 [7] years; mean [standard deviation]; 15 women) and warfarin (n = 27; 73 [9] years (p < 0.01); 11 women) were recruited. Duplex Doppler ultrasound imaging was undertaken during baseline (2 min), cuff inflation (5 min), and following cuff deflation (3 min). FMD was defined as peak increase in brachial artery diameter following cuff deflation and analysed as percentage change in diameter, as a ratio of FMD, shear rate area under the curve (SRAUC; FMD-to-SRAUC), and using SRAUC as a covariate (FMDSR). RESULTS: Baseline artery diameter (4.96 [1.14] vs. 4.89 [0.88] mm), peak diameter (5.12 [1.17] vs. 5.14 [0.93] mm), and FMDSR (3.89 [3.62] vs. 4.80 [3.60] %) were not different between warfarin and apixaban (p > 0.05; analysis of covariance with age, CHA2DS2-VASc, years since AF diagnosis, number of diabetics, alcohol drinkers, and units of alcohol consumed per week as covariates). Stepwise multiple regression identified independent association of fibrillation, hypertension, and increased age with FMD. CONCLUSION: AF patients on warfarin and apixaban exhibit similar endothelium-dependent vasodilation. Increased blood pressure negatively impacts vasodilator capacity in AF patients.

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Background: Surgery is a stressful exercise, and the experience of occupational stress may have impacts on surgical performance, and surgeon well-being. Music is played in operating theatres (OTs) throughout the world, and while it may improve surgical performance, and reduce clinician stress within the OT, concerns exist over its distracting and noise-creating properties. Methods: In this prospective observational study, between May to August 2022, Vascular, General and Paediatric surgeons and registrars in Australia and Aotearoa New Zealand (AoNZ) responded to a survey investigating the way they use music, and their perceptions and attitudes towards its effect on the OT environment. Binomial logistic regression and Chi squared tests of association were performed, accepting p < 0.05 as significant. Results: In this cohort of 120 surgeons, 45 % were vascular specialists, 30 % were female and 59 % were consultant surgeons. The most commonly preferred music genres were easy listening and pop. Over 75 % of surgeons enjoyed having music in their OTs with the majority reporting it improved their temperament, how mentally fatiguing a procedure felt and how anxious or stressed they felt. Vascular surgeons were more likely to believe music had a positive influence on communication than their general and paediatric surgery colleagues (p < 0.01). Registrars had significantly higher odds of believing music had a positive effect on their temperament, and how stressed and anxious they felt when operating, when compared to consultants (p < 0.05). Conclusions: This study provides a window into the surgeons' use of and attitudes towards intra-operative background music and its effect on stress and cognitive load in Australia and AoNZ. While overall, music is viewed positively by this cohort, there was some difference seen across specialties and level of experience. Further subjective and objective data in this field may provide useful information to guide hospital policy and inform pathways for clinician wellbeing.

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Background: Based on emerging evidence that brief periods of cessation from resistance training (RT) may re-sensitize muscle to anabolic stimuli, we aimed to investigate the effects of a 1-week deload interval at the midpoint of a 9-week RT program on muscular adaptations in resistance-trained individuals. Methods: Thirty-nine young men (n = 29) and women (n = 10) were randomly assigned to 1 of 2 experimental, parallel groups: An experimental group that abstained from RT for 1 week at the midpoint of a 9-week, high-volume RT program (DELOAD) or a traditional training group that performed the same RT program continuously over the study period (TRAD). The lower body routines were directly supervised by the research staff while upper body training was carried out in an unsupervised fashion. Muscle growth outcomes included assessments of muscle thickness along proximal, mid and distal regions of the middle and lateral quadriceps femoris as well as the mid-region of the triceps surae. Adaptions in lower body isometric and dynamic strength, local muscular endurance of the quadriceps, and lower body muscle power were also assessed. Results: Results indicated no appreciable differences in increases of lower body muscle size, local endurance, and power between groups. Alternatively, TRAD showed greater improvements in both isometric and dynamic lower body strength compared to DELOAD. Additionally, TRAD showed some slight psychological benefits as assessed by the readiness to train questionnaire over DELOAD. Conclusion: In conclusion, our findings suggest that a 1-week deload period at the midpoint of a 9-week RT program appears to negatively influence measures of lower body muscle strength but has no effect on lower body hypertrophy, power or local muscular endurance.

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OBJECTIVE: The experience of stress is common among surgeons while working in the operating theatre (OT). Understanding and finding ways to mitigate this stress is important for optimizing surgical quality and maintaining clinician wellbeing. In this pilot study, we tested the feasibility and reported the outcomes of measuring the effect of background music on intra-operative surgeon stress in the clinical environment. METHODS: The effect of Music on the Operating Surgeon: A pilot Randomized crossover Trial (the MOSART study) was conducted over a 9-month period in a single-centre. Vascular and general surgeons acting as primary operators (POs) performing elective, general anaesthetic operations were included. The intervention was surgeon-selected music, and the control was the absence of music. Outcome measures were feasibility (recruitment rate, practicability, and completeness of data), heart rate variability (HRV) indices, the Six-Item State-Trait Anxiety Inventory (STAI-6), and the Surgical Task-load Index (SURG-TLX). RESULTS: Five POs performed 74 eligible randomized cases. The protocol was well tolerated, and no cases were abandoned. Data was incomplete in 8% of cases. The overall mean (SD) operative SURG-TLX score was 48 (±22). Mean HR increased and RMSSD decreased significantly from baseline, suggesting reduced parasympathetic activity while operating. The presence of intra-operative music was not found to affect the psychological or physiological outcomes. CONCLUSIONS: A music interventional study of this nature is feasible in the operating theatre environment, though no difference was found between in the music and non-music conditions. Follow-up research in a simulated environment with intensive physiological monitoring could be considered.

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INTRODUCTION: Several retrospective studies of strength sport athletes have reported strength adaptations over months to years; however, such adaptations are not linear. METHODS: We explored changes in strength over time in a large, retrospective sample of powerlifting (PL) athletes. Specifically, we examined the rate and magnitude of strength adaptation based on age category and weight class for PL competition total, and the squat, bench press, and deadlift, respectively. Mixed effects growth modelling was performed for each operationalised performance outcome (squat, bench press, deadlift, and total) as the dependent variables, with outcomes presented on both the raw, untransformed time scale and on the common logarithmic scale. Additionally, the fitted values were rescaled as a percentage. RESULTS: Collectively, the greatest strength gains were in the earliest phase of PL participation (~ 7.5-12.5% increase in the first year, and up to an ~ 20% increase after 10 years). Females tended to display faster progression, possibly because of lower baseline strength. Additionally, female Masters 3 and 4 athletes (> 59 years) still displayed ~ 2.5-5.0% strength improvement, but a slight strength loss was observed in Masters 4 (> 69 years) males (~ 0.35%/year). CONCLUSION: Although directly applicable to PL, these findings provide population-level support for the role of consistent and continued strength training to improve strength across the age span and, importantly, to mitigate, or at least largely attenuate age-related declines in strength compared to established general population norms. This information should be used to encourage participation in strength sports, resistance training more generally, and to support future public health messaging.

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Meta-analysis has become commonplace within sport and exercise science for synthesising and summarising empirical studies. However, most research in the field focuses upon mean effects, particularly the effects of interventions to improve outcomes such as fitness or performance. It is thought that individual responses to interventions vary considerably. Hence, interest has increased in exploring precision or personalised exercise approaches. Not only is the mean often affected by interventions, but variation may also be impacted. Exploration of variation in studies such as randomised controlled trials (RCTs) can yield insight into interindividual heterogeneity in response to interventions and help determine generalisability of effects. Yet, larger samples sizes than those used for typical mean effects are required when probing variation. Thus, in a field with small samples such as sport and exercise science, exploration of variation through a meta-analytic framework is appealing. Despite the value of embracing and exploring variation alongside mean effects in sport and exercise science, it is rarely applied to research synthesis through meta-analysis. We introduce and evaluate different effect size calculations along with models for meta-analysis of variation using relatable examples from resistance training RCTs.

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This study compared the effects of supervised versus unsupervised resistance training (RT) on measures of muscle strength and hypertrophy in resistance-trained individuals. Thirty-six young men and women were randomly assigned to one of two experimental, parallel groups to complete an 8-week RT programme: One group received direct supervision for their RT sessions (SUP); the other group performed the same RT programme in an unsupervised manner (UNSUP). Programme variables were kept constant between groups. We obtained pre- and post-study assessments of body composition via multi-frequency bioelectrical impedance analysis (MF-BIA), muscle thickness of the upper and lower limbs via ultrasound, 1 repetition maximum (RM) in the back squat and bench press, isometric knee extension strength, and countermovement jump (CMJ) height. Results showed the SUP group generally achieved larger increases in muscle thickness for the triceps brachii, all sites of the rectus femoris, and the proximal region of the vastus lateralis. MF-BIA indicated increases in lean mass favoured SUP. Squat 1RM was greater for SUP; bench press 1RM and isometric knee extension were similar between conditions. CMJ increases modestly favoured UNSUP. In conclusion, our findings suggest that supervised RT promotes greater muscular adaptations and enhances exercise adherence in young, resistance-trained individuals.

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Surface EMG (sEMG) has been used to compare loading conditions during exercise. Studies often explore mean/median frequencies. This potentially misses more nuanced electrophysiological differences between exercise tasks. Therefore, wavelet-based analysis was used to evaluate electrophysiological characteristics in the sEMG signal of the quadriceps under both higher- and lower-torque (70 % and 30 % of MVC, respectively) isometric knee extension performed to momentary failure. Ten recreationally active adult males with previous resistance training experience were recruited. Using a within-session, repeated-measures, randomised crossover design, participants performed isometric knee extension whilst sEMG was collected from the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL). Mean signal frequency showed similar characteristics in each condition at momentary failure. However, individual wavelets revealed different frequency component changes between the conditions. All frequency components increased during the low-torque condition. But low-frequency components increased, and high-frequency components decreased, in intensity throughout the high-torque condition. This resulted in convergence of the low-torque and high-torque trial wavelet characteristics towards the end of the low-torque trial. Our results demonstrate a convergence of myoelectric signal properties between low- and high-torque efforts with fatigue via divergent signal adaptations. Further work should disentangle factors influencing frequency characteristics during exercise tasks.

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We tested the hypothesis that ingestion of cocoa flavanols would improve cognition during acute hypoxia equivalent to 5,500 m altitude (partial pressure of end-tidal oxygen = 45 mmHg). Using placebo-controlled double-blind trials, 12 participants ingested 15 mg·kg-1 of cocoa flavanols 90 min before completing cognitive tasks during normoxia and either poikilocapnic or isocapnic hypoxia (partial pressure of end-tidal carbon dioxide uncontrolled or maintained at the baseline value, respectively). Cerebral oxygenation was measured using functional near-infrared spectroscopy. Overall cognition was impaired by poikilocapnic hypoxia (main effect of hypoxia, P = 0.008). Cocoa flavanols improved a measure of overall cognitive performance by 4% compared with placebo (effect of flavanols, P = 0.033) during hypoxia, indicating a change in performance from "low average" to "average." The hypoxia-induced decrease in cerebral oxygenation was two-fold greater with placebo than with cocoa flavanols (effect of flavanols, P = 0.005). Subjective fatigue was increased by 900% with placebo compared with flavanols during poikilocapnic hypoxia (effect of flavanols, P = 0.004). Overall cognition was impaired by isocapnic hypoxia (effect of hypoxia, P = 0.001) but was not improved by cocoa flavanols (mean improvement = 1%; effect of flavanols, P = 0.72). Reaction time was impaired by 8% with flavanols during normoxia and further impaired by 11% during isocapnic hypoxia (effect of flavanols, P = 0.01). Our findings are the first to show that flavanol-mediated improvements in cognition and mood during normoxia persist during severe oxygen deprivation, conferring a neuroprotective effect.NEW & NOTEWORTHY We show for the first time that cocoa flavanols exert a neuroprotective effect during severe hypoxia. Following acute cocoa flavanol ingestion, we observed improvements in cognition, cerebral oxygenation, and subjective fatigue during normoxia and severe poikilocapnic hypoxia. Cocoa flavanols did not improve cognition during severe isocapnic hypoxia, suggesting a possible interaction with carbon dioxide.

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The purpose of this study was to compare the effects of electromagnetic resistance alone, as well as in combination with variable resistance or accentuated eccentric methods, with traditional dynamic constant external resistance exercise on myoelectric activity during elbow flexion. The study employed a within-participant randomized, cross-over design whereby 16 young, resistance-trained male and female volunteers performed elbow flexion exercise under each of the following conditions: using a dumbbell (DB); using a commercial electromagnetic resistance device (ELECTRO); variable resistance (VR) using a setting on the device that attempts to match the level of resistance to the human strength curve, and; eccentric overload (EO) using a setting on the device that increases the load by 50% on the eccentric portion of each repetition. Surface electromyography (sEMG) was obtained for the biceps brachii, brachioradialis and anterior deltoid on each of the conditions. Participants performed the conditions at their predetermined 10 repetition maximum. " The order of performance for the conditions was counterbalanced, with trials separated by a 10-min recovery period. The sEMG was synced to a motion capture system to assess sEMG amplitude at elbow joint angles of 30°, 50°, 70°, 90°, 110°, with amplitude normalized to the maximal activation. The anterior deltoid showed the largest differences in amplitude between conditions, where median estimates indicated greater concentric sEMG amplitude (~ 7-10%) with EO, ELECTRO and VR compared with DB. Concentric biceps brachii sEMG amplitude was similar between conditions. In contrast, results indicated a greater eccentric amplitude with DB compared to ELECTRO and VR, but unlikely to exceed a 5% difference. Data indicated a greater concentric and eccentric brachioradialis sEMG amplitude with DB compared to all other conditions, but differences were unlikely to exceed 5%. The electromagnetic device tended to produce greater amplitudes in the anterior deltoid, while DB tended to produce greater amplitudes in the brachioradialis; amplitude for the biceps brachii was relatively similar between conditions. Overall, any observed differences were relatively modest, equating to magnitudes of ~ 5% and not likely greater than 10%. These differences would seem to be of minimal practical significance.

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In hypertension, the cardiorespiratory responses to peripheral chemoreflex activation (hypoxia) and inactivation (hyperoxia) are reportedly augmented, but the impact on peripheral venous function is unknown. We tested the hypothesis that in hypertensives, both hypoxia and hyperoxia evoke more pronounced changes in lower limb venous capacity and compliance, than in age-matched normotensives. In 10 hypertensive [HTN: 7 women; age: 71.7 ± 3.7 yr, mean blood pressure (BP): 101 ± 10 mmHg, mean ± SD] and 11 normotensive (NT: 6 women; age: 67.7 ± 8.0 yr, mean BP 89 ± 11 mmHg) participants, great saphenous vein cross-sectional area (GSV CSA; Doppler ultrasound) was measured during a standard 60 mmHg thigh cuff inflation-deflation protocol. Separate conditions of room air, hypoxia [fraction of inspired oxygen ([Formula: see text]): 0.10] and hyperoxia ([Formula: see text]: 0.50) were tested. In HTN, GSV CSA was decreased in hypoxia (5.6 ± 3.7 mm2, P = 0.041) compared with room air (7.3 ± 6.9 mm2), whereas no change was observed with hyperoxia (8.0 ± 9.1 mm2, P = 0.988). In NT, no differences in GSV CSA were observed between any condition (P = 0.299). Hypoxia enhanced GSV compliance in HTN (-0.0125 ± 0.0129 vs. -0.0288 ± 0.0090 mm2·100 mm2·mmHg-1, room air vs. hypoxia, respectively; P = 0.004), but it was unchanged in NT (-0.0139 ± 0.0121 vs. -0.0093 ± 0.0066 mm2·100 mm2·mmHg-1, room air vs. hypoxia, respectively; P < 0.541). Venous compliance was unaltered with hyperoxia in both groups (P < 0.05). In summary, compared with NT, hypoxia elicits a decrease in GSV CSA and enhanced GSV compliance in HTN, indicating enhanced venomotor responsiveness to hypoxia.NEW & NOTEWORTHY Hypertension remains a significant global health problem. Although hypertension research and therapies are keenly focused on the heart and arterial circulation, the venous circulation has been neglected comparatively. We determined whether hypoxia, known to cause peripheral chemoreflex activation, evoked more pronounced changes in lower limb venous capacity and compliance in hypertensives (HTN) than in age-matched normotensives (NT). We found that hypoxia reduced venous capacity in the great saphenous vein in HTN and increased its compliance twofold. However, hypoxia did not affect venous function in NT. Our data indicate the venomotor response to hypoxia is enhanced in hypertension, and this may contribute to the hypertensive state.

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