Supine Bicycle Research Articles

Cerebral blood velocity during concurrent supine cycling, lower body negative pressure, and head-up tilt challenges: implications for concussion rehabilitation

Introduction. The effect of concurrent head-up tilt and lower body negative pressure (LBNP) have been examined on middle cerebral artery velocity (MCAv) at rest; however, it is unknown the superimposed effect these factors have on blunting the elevation in cerebral blood velocity associated with moderate-intensity exercise. Methods. 23 healthy adults (11 females / 12 males, 20–33 years) completed three visits. The first consisted of a maximal ramp supine cycling test to identify the wattage associated with individualized maximal MCAv. Subsequent visits included randomized no LBNP (control) or LBNP at −40 Torr (experimental) with successively increasing head-up tilt stages of 0, 15, 30, and 45 degrees during the pre-described individualized wattage. Transcranial Doppler ultrasound was utilized to quantify MCAv. Two-factorial repeated measures analysis of variance with effect sizes were used to determine differences between days and tilt stages. Results. Between-day baseline values for MCAv, heart rate, and blood pressure displayed low variability with <5% variation. With no LBNP, MCAv was above baseline on average for all participants; however, 15 degrees and 30 degrees tilt with concurrent −40 Torr LBNP was sufficient to return MCAv to 100% of baseline values in females and males, respectively. Body-weight did not impact the association between tilt and pressure (R 2 range: 0.01–0.12). Conclusion. Combined LBNP and tilt were sufficient to reduce the increase in MCAv associated with moderate-intensity exercise. This exercise modality shows utility to enable individuals with a concussion to obtain the positive physiological adaptions associated with exercise while minimizing symptom exacerbation due to the notion of the Monro-Kellie doctrine.

The Effect of Supine Cycling and Progressive Lower Body Negative Pressure on Cerebral Blood Velocity Responses.

Moderate-intensity aerobic exercise increases cerebral blood velocity (CBv) primarily due to hyperpnea-induced vasodilation; however, the integrative control of cerebral blood flow (CBF) allows other factors to contribute to vasodilation. Lower body negative pressure (LBNP) can reduce CBv, the exact LBNP-intensity required to blunt the aforementioned exercise-induced CBv response is unknown. This could hold utility for concussion recovery, allowing individuals to exercise at higher-intensities without symptom exacerbation. Thirty-two healthy adults (age: 20-33 years; 19 females) completed a stepwise maximal-exercise test to determine each participant's wattage associated with their exercise-induced maximal CBv increase. During the second visit, participants completed moderate-intensity exercise at their determined threshold, while progressive LBNP was applied at 0, -20, -40, -60, -70, -80, and ~88 Torr. Bilateral middle cerebral artery blood velocities (MCAv), mean arterial pressure (MAP), heart rate, respiratory rate, and end-tidal carbon dioxide levels were measured continuously. Two-way analysis of variance with effect sizes compared between sexes and stages. Compared to resting-supine baseline, averaged MCAv was elevated during 0 and -20 Torr LBNP (q-value>7.73; p<0.001); no differences were noted between baseline and -40 to -70 Torr (q-value<|4.24|; p>0.262). Differences were present between females and males for absolute MCAv measures (q-value>11.2; p<0.001), but not when normalized to baseline (q-value<0.03; p>0.951). Supine cycling-elicited increases in MCAv were blunted during the application of LBNP ranging from -40 to -70 Torr. The blunted CBv response demonstrates the potential benefit of allowing individuals to aerobically train (moderate-intensity supine cycling with LBNP) without exacerbating symptoms during concussion recovery.

Association between fractional flow reserve and CMR-derived exercise capacity

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NMRC Open-Fund Young Individual Research Grant, Singapore. NMRC Open-Fund Individual Research Grant, Singapore. Background In-scanner exercise stress cardiac magnetic resonance (ExCMR) imaging using supine cycling ergometer offers assessment of perfusion defects, inducible regional wall motion abnormalities, viability and exercise capacity in a single examination (EMPIRE Trial). Aim We aim to investigate the role of CMR-derived exercise capacity to assess the physiological stenosis severity, measured by invasive fractional flow reserve (FFR). Methods 107 patients (60±8 years, 80 males) with suspected coronary artery disease (CAD) underwent ExCMR (Siemens 1.5T) and invasive coronary angiogram with FFR measurement (PressureWireTMX Guidewire – Abbott Laboratories) followed previously published trial protocol [1]. Exercise capacity was derived as age- and sex-specific percentile of peak cardiac index, according to the reference range previously established [2]. Results Exercise capacity remains the only predictor of FFR values (beta 0.005, P&amp;lt;0.001) with backward multivariate regression of clinical variables (age, sex, BMI, presence of hyperlipidema, blood pressure, presence of diabetes mellitus) and quantitative CMR parameters (LV mass, extracellular volume, LV stroke volume at rest and exercise capacity). Patients with haemodynamically significant CAD (FFR&amp;lt;0.8) had significantly lower exercise capacity (median 14 [IQR 4–20] vs 5 [IQR 1–10] age- and sex-specific percentile of peak cardiac index, P&amp;lt;0.001) Conclusion In addition to perfusion defects, regional wall motion abnormalities and viability assessment to detect coronary artery disease, exercise capacity predicts the physiological stenosis severity.

Larger splenic emptying correlate with slower EPOC kinetics in healthy men and women during supine cycling.

The present study investigated whether larger splenic emptying augments faster excess post-exercise O2 consumption (EPOC) following aerobic exercise cessation. Fifteen healthy participants (age 24 ± 4, 47% women) completed 3 laboratory visits at least 48-h apart. After obtaining medical clearance and familiarizing themselves with the test, they performed a ramp-incremental test in the supine position until task failure. At their final visit, they completed three step-transition tests from 20 W to a moderate-intensity power output (PO), equivalent to [Formula: see text]O2 at 90% gas exchange threshold, where data on metabolic, cardiovascular, and splenic responses were recorded simultaneously. After step-transition test cessation, EPOCfast was recorded, and the first 10min of the recovery period was used for further analysis. Blood samples were collected before and immediately after the end of exercise. In response to moderate-intensity supine cycling ([Formula: see text]O2 = ~ 2.1 L·min-1), a decrease in spleen volume of ~ 35% (p = 0.001) was observed, resulting in a transient increase in red cell count of ~ 3-4% (p = 0.001) in mixed venous blood. In parallel, mean blood pressure, heart rate, and stroke volume increased by 30-100%, respectively. During recovery, mean τ[Formula: see text]O2 was 45 ± 18s, the amplitude was 2.4 ± 0.5 L·min-1, and EPOCfast was 1.69 L·O2. Significant correlations were observed between the percent change in spleen volume and (i) EPOCfast (r = - 0.657, p = 0.008) and (ii) τ[Formula: see text]O2 (r = - 0.619, p = 0.008), but not between the change in spleen volume and (iii) [Formula: see text]O2 peak (r = 0.435, p = 0.105). Apparently, during supine cycling, individuals with larger spleen emptying tend to have slower [Formula: see text] O2 recovery kinetics and a greater EPOCfast.

Haemodynamic and metabolic adaptations in coronary microvascular disease

ObjectiveWe aimed to evaluate the microcirculatory resistance (MR) and myocardial metabolic adaptations at rest and in response to increased cardiac workload in patients with suspected coronary microvascular dysfunction (CMD).MethodsPatients with...

Early aortic valve replacement improves exercise capacity in truly asymptomatic patients with severe aortic stenosis

Abstract Background Exercise capacity is a strong predictor of morbidity and mortality overall. In severe aortic stenosis (AS) ustained pressure overload during watchful waiting is associated with LV structural and functional deterioration and impaired clinical outcome both pre- and post aortic valve replacement (AVR). The effect of early surgical aortic valve replacement (SAVR) in asymptomatic patients with severe AS and normal left ventricular function on exercise capacity in unknown. Aim We investigated whether the early surgical AVR in truly asymptomatic patients with severe aortic stenosis and normal LVEF improves the exercise capacity. Methods This is a sub-analysis or the AVATAR trial (NCT02436655), which is international prospective randomized controlled trial that evaluated the safety and efficacy of early SAVR in the treatment of asymptomatic patients with severe AS, according to common criteria (valve area ≤1 cm2 with aortic jet velocity &amp;gt;4 m/s or a mean transaortic gradient ≥40 mm Hg), and with normal left ventricular function. Patients underwent cardiopulmonary exercise testing (supine bicycle, ramp protocol, 15 W/min) at the baseline and 12 months following the randomization. Patients who had positive exercise testing at baseline visit were excluded. We compared the value of workload (in WATs), VO2 max, VO2 AT, VE/VCO2 and PETCO2 slope at the inclusion and at 12 months. Results Total of 157 patients (mean age, 67 years; 57% men) were randomly allocated to early surgery (n=78) or conservative treatment (n=79). Mean LVEF and Vmax in early surgery and conservative treatment group were 70% and 4.5m/s and 69% and 4.5m/s, respectively. After 12 months in patients with conservative treatment there was a slight decrease in the values of workload, VO2 max, VO2 AT, VE/VCO2 and PETCO2 slope, but without statistical significance. However operated patients showed a significant increase in workload (115.4±38.4 watts at 12 months vs 104.8±42.2 at inclusion, p=0.038) and VO2 max (19.7±6.8 at 12 months vs 16.2±5.4 at the inclusion, p=0.048), while there was slight increase in the values of VO2 AT, VEVCO2 and PETCO2 but without statistical significance. Conclusion Early SAVR improve the functional capacity in asymptomatic patients with severe aortic stenosis and normal left ventricular ejection fraction Funding Acknowledgement Type of funding sources: None.

Skeletal Muscle Deoxygenation Amplitude, Rather Than Splenic Emptying Contributes to Higher V̇O2max. During Supine Cycling in Healthy Active Men

The aim of the present study was to investigate whether greater splenic emptying or higher skeletal muscle deoxygenation amplitude (determined by near‐infrared spectroscopy, NIRS) contributes to higher V̇O2 max. during supine cycling. We hypothesized that the reduction in splenic volume, and subsequent manipulations of O2 delivery by blood ejected from the spleen, would not contribute to higher V̇O2max. during supine cycling, because this transient increase in circulating red blood cells (RBC’s) would be insufficient to increase the O2 storage capacity in the blood. Rather, O2 uptake during supine cycling in healthy subjects is expected to be limited, at least in part, by skeletal muscle bioenergetics. Here, fourteen healthy young individuals completed all study procedures. On three separate days they underwent a medical examination, supine V̇O2 max. test, and three step‐transitions from 20 W to a moderate‐intensity power output equivalent to V̇O2 uptake at 90% gas exchange threshold. During these step‐transitions, pulmonary V̇O2, NIRS of the vastus lateralis (VL), and cardiovascular responses (via Finapres) were measured continuously. In parallel, minute‐by‐minute ultrasound measurements of the spleen were performed. Blood samples were taken before and immediately after the step‐transition cycling. Mean V̇O2 max. was 46.5±6.5 mL·kg·min‐1. In response to supine step‐transition cycling, spleen volume was significantly reduced (by ~38%, p=.001). Both hematocrit and hemoglobin concentration increased by ~4%, after exercise cessation. There was no correlation between: i)spleen volume at rest, ii) changes in spleen volume (%), iii) hematocrit at rest and V̇O2 max. However, a linear, near‐significant correlation was observed between VL deoxygenation amplitude and V̇O2 max. Apparently, individuals with a higher V̇O2 max. are capable of greater O2 extraction from the superficial knee extensors, whereas in parallel, greater splenic emptying does not correlate with higher V̇O2 max, regardless of the subsequent release of erythrocytes. Therefore, it is reasonable to suggest that maximal O2 utilization during supine cycling in healthy young men is limited, in part, by skeletal muscle bioenergetics.ReferencesHolmström, PK, Karlsson Ö, Lindblom H, McGawley K, &amp; Schagatay, EK. (2021). Enhanced splenic volume and contraction in elite endurance athletes. J Appl Physiol, 131(2), 474‐486, DOI: 10.1152/japplphysiol.01066.2020;Zubac, D, Obad, A, Bosnjak, A, Zec, M, Ivancev, V, Valic, Z. (2021). Spleen emptying does not correlate with faster oxygen kinetics during a step‐transition supine cycling. Appl Physiol Nutr Metab. Accepted for publication in Jun 24. doi: 10.1139/apnm‐2021‐0294.2021.

Determination of exercise intensity domains during upright versus supine cycling: a methodological study.

BackgroundThere is a growing interest among the research community and clinical practitioners to investigate cardiopulmonary exercise test (CPET) procedures and protocols utilized in supine cycling.Materials and MethodsThe current study investigated the effects of posture on indicators of exercise intensity including gas exchange threshold (GET), respiratory compensation point (RCP), and the rate of peak oxygen uptake (V̇O2 peak), as well as the role of V̇O2 mean response time (MRT) in determining exercise intensity domains in nineteen healthy men (age: 22 ± 3 years). Two moderate-intensity step-transitions from 20 to 100 Watt (W) were completed, followed by a maximal CPET. After completing the ramp test, participants performed a constant-load at 90% of their attained peak power output (PPO).ResultsNo differences were observed in the V̇O2 MRT between the two positions, although the phase II-time constant (τV̇O2p) was 7 s slower in supine position compared to upright (p = 0.001). The rate of O2 uptake in the supine position at GET and RCP were lower compared to the upright position (208 ± 200 mL·min−1 (p = 0.007) and 265 ± 235 mL·min−1 (p = 0.012) respectively). Besides, V̇O2 peak was significantly decreased (by 6%, p = 0.002) during supine position. These findings were confirmed by the wide limits of agreement between the measures of V̇O2 in different postures (V̇O2 peak: −341 to 859; constant-load test: −528 to 783; GET: −375 to 789; RCP: −520 to 1021 all in mL·min−1).ConclusionSince an accurate identification of an appropriate power output (PO) from a single-visit CPET remains a matter of debate, especially for supine cycling, we propose that moderate-intensity step-transitions preceding a ramp CPET could be a viable addition to ensure appropriate exercise-intensity domain determination, in particular upon GET-based prescription.

Improving physical function of patients following intensive care unit admission (EMPRESS): protocol of a randomised controlled feasibility trial

IntroductionPhysical rehabilitation delivered early following admission to the intensive care unit (ICU) has the potential to improve short-term and long-term outcomes. The use of supine cycling together with other rehabilitation...

Early Hemodynamic Changes following Surgical Ablation of the Right Greater Splanchnic Nerve for the Treatment of Heart Failure with Preserved Ejection Fraction.

Background: Permanent ablation of the right greater splanchnic nerve (GSN) has previously been demonstrated to improve quality of life and functional outcomes, as well as reduce abnormally high intracardiac filling pressures, in patients with heart failure with preserved ejection fraction (HFpEF) at 1, 3 and 12 months following the procedure. We hypothesize that hemodynamic changes that ensue from surgical right GSN ablation would be apparent as early as 24 h after the medical intervention. Methods and Results: This is a prespecified analysis of a single-arm, two-center, open-label study evaluating the effects of right GSN ablation via thoracoscopic surgery in HFpEF patients with pulmonary capillary wedge pressure (PCWP) ≥15 mmHg at rest or ≥25 mmHg with supine cycle ergometry. A total of seven patients (median age 67 years, 29% female) underwent GSN removal followed by invasive right heart catheterization within 24 h. GSN ablation resulted in a significant reduction in PCWP 24 h after the procedure compared to baseline for both 20 W exercise (baseline (28.0 ± 4.3 mmHg) to 24 h (19.6 ± 6.9 mmHg); p = 0.0124) and peak exercise (baseline (25.6 ± 2.4 mmHg) to 24 h (17.4 ± 5.9 mmHg); p = 0.0025). There were no significant changes in resting or leg-up hemodynamics. Conclusions: Permanent right GSN ablation leads to a reduction in intracardiac filling pressures during exercise, apparent as early as 24 h following the procedure.

High prevalence of occult left ventricular diastolic dysfunction detected by exercise stress test in systemic sclerosis

Despite the poor prognosis of systemic sclerosis (SSc) due to the co-occurrence of left ventricular diastolic dysfunction (LVDD), presence of occult LVDD has not been sufficiently investigated. This retrospective study aimed to reveal the prevalence and determinants of occult LVDD in patients with SSc by exercise stress test. Forty-five SSc patients (age, 63 ± 13 years; men/women, 6/39) with normal pulmonary artery pressure and pulmonary artery wedge pressure (PAWP) at rest underwent a symptom-limited exercise test with right heart catheterization using a supine cycle ergometer; haemodynamic parameters at rest, leg raise and during exercise were evaluated. Occult LVDD defined PAWP ≥ 25 mmHg during exercise was seen in 13 patients (29%). Higher PAWP, lower pulmonary vascular resistance and diastolic pulmonary pressure gradient, larger left atrium at rest, and higher PAWP during leg raise (15 ± 4 vs 10 ± 4 mmHg in non-LVDD group, p < 0.001) were observed in the occult LVDD group. The area under the ROC curve for PAWP after leg raise was largest at 0.83 (95% CI: 0.70–0.95, p = 0.001). About one-third (29%) of SSc patients with normal haemodynamics at rest showed occult LVDD. A higher PAWP after leg raise could be useful for detecting occult LVDD.

No differences in splenic emptying during on-transient supine cycling between aerobically trained and untrained participants.

PurposeThe role of splenic emptying in O2 transport during aerobic exercise still remains a matter of debate. Our study compared the differences in spleen volume changes between aerobically trained and untrained individuals during step-transition supine cycling exercise at moderate-intensity. We also examined the relationship between spleen volume changes, erythrocyte release, and O2 uptake parameters.MethodsFourteen healthy men completed all study procedures, including a detailed medical examination, supine maximal O2 uptake ({dot{text{V}}text{O}}_{2} max.) test, and three step-transitions from 20 W to a moderate-intensity power output, equivalent to {dot{text{V}}text{O}}_{2} uptake at 90% gas exchange threshold. During these step-transitions pulmonary {dot{text{V}}text{O}}_{{2{text{p}}}}, near-infrared spectroscopy of the vastus lateralis, and cardiovascular responses were continuously measured. In parallel, minute-by-minute ultrasonic measurements of the spleen were performed. Blood samples were taken before and immediately after step-transition cycling.ResultsOn average, {dot{text{V}}text{O}}_{2} max. was 10 mL kg min−1 (p = 0.001) higher in trained compared to their aerobically untrained peers. In response to supine step-transition cycling, the splenic volume was significantly reduced, and the largest reduction (~ 106 to 115 mL, ~ 38%, p = 0.001) was similar in both aerobically trained and untrained individuals. Erythrocyte concentration and platelet count transiently increased after exercise cessation, with no differences observed between groups. However, the vastus lateralis deoxygenation amplitude was 30% (p = 0.001) greater in trained compared to untrained individuals. No associations existed between: (i) spleen volumes at rest (ii) spleen volume changes (%), (iii) resting hematocrit and oxygen uptake parameters.ConclusionGreater splenic emptying and subsequent erythrocyte release do not lead to a slower tau {dot{text{V}}text{O}}_{{2{text{p}}}}, regardless of individual {dot{text{V}}text{O}}_{2} max. readings.

Supine arm cycling during the post-flap recovery period for persons with spinal cord injuries: The multi-purpose arm cycle ergometer (M-PACE) safety and pilot testing

Objective: To describe how using a supine arm cycle ergometer can safely reduce deconditioning experienced by patients with spinal cord injury or disorder (SCI/D) during their four to six weeks of complete bed rest after surgery to close a stage 4 pressure injury. Design: This pilot project used a newly designed arm cycle ergometer (known as the M-PACE) that extends over the bed, allowing a patient to lie completely supine while exercising. Setting: The M-PACE was designed and built at the Minneapolis Veterans Affairs Health Care System (MVAHCS) and pilot tested at the MVAHCS SCI/D Center. Participants: Patients with SCI/D, recovering from flap surgery and deemed appropriate to use the arm cycle ergometer were enrolled in the pilot study (n = 47). Outcome Measures: A pre–post six-minute arm test (6MAT), a proxy for conditioning, was conducted on a subset (n = 15) of participants before and after the supine cycling exercise training program. Participants’ rating of perceived exertion (RPE) scores were collected at cessation of each 6MAT. Participants gave feedback on their perception of using the M-PACE. Results/Conclusions: The 6MAT RPE was significantly reduced after training with the M-PACE while on bed rest (P = 0.003). Also, significantly more rotations were performed after completing the training program (P = 0.02). Further, study participants who accessed the M-PACE found using it helped offset the tedium of laying supine during flap surgery recovery. The differences in the 6MAT pre- to post measures indicate the M-PACE should be further studied for offsetting the normal deconditioning that occurs with extended bedrest.

Quantification of mitral regurgitation and biventricular assessment is feasible during continuous supine exercise cardiovascular magnetic resonance in primary mitral regurgitation patients

Abstract Funding Acknowledgements Type of funding sources: None. Background Biventricular volume and great vessel flow assessment during continuous supine free-breathing exercise cardiovascular magnetic resonance (Ex-CMR) is feasible in healthy volunteers using Compressed SENSEx3 (CS3) sequences1. Exercise transthoracic echocardiography (TTE) provides prognostic information in primary mitral regurgitation (MR). Resting CMR offers reference standard biventricular assessment and MR quantification with superior reproducibility to TTE. Ex-CMR assessment of biventricular volumes and quantitated MR may offer additional prognostic information. Purpose Determine the feasibility of biventricular assessment and MR quantification in primary MR patients during continuous supine Ex-CMR using the recently validated protocol1. Methods 10 asymptomatic patients with at least moderate primary MR on TTE (8 male, median age 62, 55-67years interquartile range) underwent continuous in-scanner (1.5T Philips Ingenia) supine cycle ergometer (Lode BV) Ex-CMR. Target heart rates (THR) were individually prescribed using heart rate reserve (HRR) and age predicted maximal heart rate model. Participants exercised for 2-minutes at no resistance, then an increase of 25-Watts every 2-minutes until THR achieved at low (30-39% HRR), then moderate (40-59% HRR) stages. CMR imaging: free-breathing CS3 respiratory navigated short axis cine imaging and free-breathing CS3 aortic phase-contrast magnetic-resonance at rest, low and moderate exercise stages. MR was quantified indirectly from left ventricular (LV) and aortic stroke volumes. Intra/inter-observer reproducibility was assessed by coefficient of variance (CV). Results All patients completed the Ex-CMR protocol without complication. During exercise, no statistically significant changes occurred in LV volumes, global left ventricular ejection fraction (LVEF), right ventricular end-diastolic or systolic volumes (Table 1). From rest to low and moderate exercise: right ventricular ejection fraction increased (55 ± 5.4% to 60 ± 6.0% and 63 ± 6.6% respectively, p = 0.001) and MR fraction decreased (40 ± 14% to 36 ± 11% and 30 ± 15% respectively, p = 0.006) allowing effective forward LVEF (aortic stroke volume/ left ventricular end-diastolic volume) to increase (38 ± 9.3% to 43 ± 9.3% and 46 ± 11% respectively, p = 0.004). Intra-observer reproducibility (Table 2) was excellent (CV &amp;lt;10%), except right ventricular stroke volumes (RVSV) during low, MR volumes and fraction during moderate and right ventricular end-systolic volumes (RVESV) during both exercise stages, which were good (CV10-20%). Inter-observer reproducibility (Table 2) was excellent (CV &amp;lt; 10%), except RVESV and MR volumes at all stages, LV end-systolic volumes during low and MR fraction during moderate exercise, which were good (CV 10-20%). Conclusion Biventricular assessment and MR quantification during continuous supine Ex-CMR is feasible in asymptomatic primary MR patients, further research assessing the techniques prognostic ability is now warranted.

Spleen emptying does not correlate with faster oxygen kinetics during a step-transition supine cycling.

This manuscript quantified spleen volume changes and examined the relationship between those changes and oxygen uptake kinetics during supine cycling. Ten volunteers (age= 22± 3), completed 3 step transitions from 20W to their power output at 90% gas exchange threshold. Ultrasonic measurements of the spleen were performed each minute. The largest spleen volume reduction was 105mL (p= 0.001). No associations existed between i) spleen volumes at rest; and ii) spleen volume changes (%) and tau pulmonary oxygen uptake (τV̇O2p). Larger resting spleen volume and greater emptying do not correlate with a faster τV̇O2p. Novelty: Greater splenic contractions do not augment τV̇O2p, irrespective of spleen emptying and subsequent erythrocyte release.

The ramp and all-out exercise test to determine critical power: validity and robustness to manipulations in body position

PurposeThe purpose of the present study was to determine whether a contiguous ramp and all-out exercise test could accurately determine critical power (CP) in a single laboratory visit during both upright and supine cycle exercise.MethodsHealthy males completed maximal ramp-incremental exercise on a cycle ergometer in the upright (n = 15) and supine positions (n = 8), with task failure immediately followed by a 3-min all-out phase for determination of end-test power (EP). On separate days, participants undertook four constant-power tests in either the upright or supine positions with the limit of tolerance ranging from ~ 2 to 15 min for determination of CP.ResultsDuring upright exercise, EP was highly correlated with (R2 = 0.93, P < 0.001) and not different from CP (CP = 221 ± 40 W vs. EP = 226 ± 46 W, P = 0.085, 95% limits of agreement − 30, 19 W). During supine exercise, EP was also highly correlated with (R2 = 0.94, P < 0.001) and not different from CP (CP = 140 ± 42 W vs. EP = 136 ± 40 W, P = 0.293, 95% limits of agreement − 16, 24 W).ConclusionThe present data suggest that EP derived from a contiguous ramp all-out exercise test is not different from the gold-standard method of CP determination during both upright and supine cycle exercise when assessed at the group level. However, the wide limits of agreement observed within the present study suggest that EP and CP should not be used interchangeably.

Power Output and Efficiency During Supine, Recumbent, and Upright Cycle Ergometry.

Recumbent and supine cycling are common exercise modes in rehabilitation and clinical settings but the influence of postures on work efficiency is unclear. Therefore, the aim of this study was to compare metabolic and ventilatory efficiency during upright, recumbent, and supine postures. Potential differences should be assessed for suitable diagnostics and for prescriptions of training that probably is performed in alternative postures. Eighteen healthy subjects (age: 47.2 ± 18.4 years; 10 female, 8 male) participated in the study and each completed three incremental cycle ergometer tests until exhaustion in upright, recumbent (40°), and supine positions. Gas exchange, heart rate (HR), and lactate concentrations were analyzed and efficiency was calculated subsequently. Testing sessions were performed in random order within a 2-week period. Upright cycling resulted in significantly higher peak values [power output, oxygen uptake (Vo2), HR] as well as performance at lactate and ventilatory thresholds in comparison to recumbent or supine positions. Vco2/Vo2 slope and ventilatory efficiency (VE/Vco2 slope) were not affected by posture. Aerobic work efficiency (Vo2/P slope) and gross efficiency (GE) differed significantly between postures. Hereby, GE was lowest in supine cycling, particularly obvious in a mainly aerobic condition at 70 Watt [Median 11.6 (IQR 10.9–13.3) vs. recumbent: 15.9 (IQR 15.6–18.3) and upright: 17.4 (IQR 15.1–18.3)]. Peak power as well as GE and work efficiency values are influenced by cycling position, reinforcing the importance of adjusting test results for training prescriptions. Surprisingly, ventilatory efficiency was not affected in this study and therefore does not seem to falsify test results for pulmonary diagnostics.

Spleen Contraction During Step‐Transition Supine Cycling Exercise: Preliminary findings

The current literature suggests that the spleen plays a significant role during physiological stress like exercise or apnea, primarily due to its capacity to contract and release additional red blood cells (RBC) into the systemic circulation. Besides the RBC release, human spleen emptying is also associated with circulating platelets release. However, data on the circulating platelets release following acute exercise have not yet been examined thoroughly. This is especially important since the spleen platelet volume is ~20% larger compared to the volume of circulating platelets, and some authors suggest that increased spleen platelet concentration is associated with the greater risk of a cardiovascular or cerebrovascular event during exercise. The present study aims to explore the magnitude of spleen contraction during on-transient supine cycling exercise in healthy humans. We hypothesized that the spleen is capable of rapid contractions during on-transient cycling, thereby releasing an additional amount of both RBC and platelets into the systemic circulation. Such an increase in RBC count in particular may facilitate O2 transport, and result in faster oxygen kinetics during on transient supine cycling. Healthy, active volunteers (age= 22±3, V̇O2 max.= 48±5 mL·kg·min-1), completed three laboratory visits, including a detailed medical examination, resting ultrasound imaging of the spleen, V̇O2 max. test until voluntary exhaustion, and a supine step-transition test from 20 W to a moderate-intensity cycling power output (PO), corresponding to V̇O2 at 90% gas exchange threshold (GET). During the step-transitions breath-by-breath pulmonary oxygen uptake (V̇O2p), near-infrared spectroscopy derived muscle oxygenation, and beat-by-beat cardiovascular response (via Finapres) were continuously monitored. In parallel, minute by minute ultrasonic measurements of the spleen function were performed in successive, 3 sec. time frames. Blood samples were drawn from the antecubital vein before and immediately after the acute exercise intervention.Currently, six participants completed all study procedures. Compared to baseline readings, the largest spleen volume reduction (~40%) was observed during the 6th minute of cycling at 90% GET. Spleen volume recovered to baseline values after 20 minutes. Immediately after exercise cessation the mean RBC and platelet count increased significantly by 3.2% and 6.5%, respectively. In parallel, the V̇O2p was 46±10 sec, while the mean V̇O2 uptake was ~2.5 L·min-1. Secondary to these findings, transient rises in mean arterial pressure (MAP) and heart rate (HR), were observed during the step-transition exercise, with MAP and HR reaching the highest value of 110±4 mmHg and 149±2 bmp, respectively. In conclusion, these preliminary findings indicate that splenic contraction evoked by a series of on-transient cycling bouts at 90% GET results in a rapid increase in RBC and platelet count into the systemic circulation of healthy active individuals.

Levosimendan Improves Hemodynamics and Exercise Tolerance in PH-HFpEF: Results of the Randomized Placebo-Controlled HELP Trial

ObjectivesThe purpose of this study was to evaluate the effects of intravenous levosimendan on hemodynamics and 6-min walk distance (6MWD) in patients with pulmonary hypertension and heart failure with preserved ejection fraction (PH-HFpEF). BackgroundThere are no proven effective treatments for patients with PH-HFpEF. MethodsPatients with mean pulmonary artery pressure (mPAP) ≥35 mm Hg, pulmonary capillary wedge pressure (PCWP) ≥20 mm Hg, and LVEF ≥40% underwent 6MWD and hemodynamic measurements at rest, during passive leg raise, and supine cycle exercise at baseline and after an open-label 24-h levosimendan infusion (0.1 μg/kg/min). Hemodynamic responders (those with ≥4 mm Hg reduction of exercise-PCWP) were randomized (double blind) to weekly levosimendan infusion (0.075 to 0.1 ug/kg/min for 24 h) or placebo for 5 additional weeks. The primary end point was exercise-PCWP, and key secondary end points included 6MWD and PCWP measured across all exercise stages. ResultsThirty-seven of 44 patients (84%) met responder criteria and were randomized to levosimendan (n = 18) or placebo (n = 19). Participants were 69 ± 9 years of age, 61% female, and with resting mPAP 41.0 ± 9.3 mm Hg and exercise-PCWP 36.8 ± 11.3 mm Hg. Compared with placebo, levosimendan did not significantly reduce the primary end point of exercise-PCWP at 6 weeks (−1.4 mm Hg; 95% confidence interval [CI]: −7.8 to 4.8; p = 0.65). However, levosimendan reduced PCWP measured across all exercise stages (−3.9 ± 2.0 mm Hg; p = 0.047). Levosimendan treatment resulted in a 29.3 m (95% CI: 2.5 to 56.1; p = 0.033) improvement in 6MWD compared with placebo. ConclusionsSix weeks of once-weekly levosimendan infusion did not affect exercise-PCWP but did reduce PCWP incorporating data from rest and exercise, in tandem with increased 6MWD. Further study of levosimendan is warranted as a therapeutic option for PH-HFpEF. (Hemodynamic Evaluation of Levosimendan in Patients With PH-HFpEF [HELP]; NCT03541603)

Multiparametric exercise stress cardiovascular magnetic resonance in the diagnosis of coronary artery disease: the EMPIRE trial

BackgroundStress cardiovascular magnetic resonance (CMR) offers assessment of ventricular function, myocardial perfusion and viability in a single examination to detect coronary artery disease (CAD).We developed an in-scanner exercise stress CMR (ExCMR) protocol using supine cycle ergometer and aimed to examine the diagnostic value of a multiparametric approach in patients with suspected CAD, compared with invasive fractional flow reserve (FFR) as the reference gold standard.MethodsIn this single-centre prospective study, patients who had symptoms of angina and at least one cardiovascular disease risk factor underwent both ExCMR and invasive angiography with FFR. Rest-based left ventricular function (ejection fraction, regional wall motion abnormalities), tissue characteristics and exercise stress-derived (perfusion defects, inducible regional wall motion abnormalities and peak exercise cardiac index percentile-rank) CMR parameters were evaluated in the study.ResultsIn the 60 recruited patients with intermediate CAD risk, 50% had haemodynamically significant CAD based on FFR. Of all the CMR parameters assessed, the late gadolinium enhancement, stress-inducible regional wall motion abnormalities, perfusion defects and peak exercise cardiac index percentile-rank were independently associated with FFR-positive CAD. Indeed, this multiparametric approach offered the highest incremental diagnostic value compared to a clinical risk model (χ2 for the diagnosis of FFR-positive increased from 7.6 to 55.9; P < 0.001) and excellent performance [c-statistic area under the curve 0.97 (95% CI: 0.94–1.00)] in discriminating between FFR-normal and FFR-positive patients.ConclusionThe study demonstrates the clinical potential of using in-scanner multiparametric ExCMR to accurately diagnose CAD.Trial registration: ClinicalTrials.gov, NCT03217227, Registered 11 July 2017–Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03217227?id=NCT03217227&draw=2&rank=1&load=cart