Ramp Protocol Research Articles

Does the acute hemodynamic response to a maximum running exercise depend on the aerobic training status of the subjects?

BackgroundHigh-intensity training has become increasingly popular in recent years but the exact effects of high intensity running on the hemodynamic system are not entirely understood and it is unknown whether the aerobic training status of the subjects might influence these hemodynamic reactions. Therefore, the study aims to evaluate whether the acute reactions of peripheral and central blood pressure (BP) and arterial stiffness (AS) to a maximal running exercise depend the training status of the subjects. Methods41 healthy subjects were recruited. Of these were 21 aerobically trained (AE; 11 men) and 20 untrained (UN; 10 men). Aortic pulse wave velocity (PWV), peripheral and central BP was measured at rest and immediately after a maximal treadmill exercise using a ramp protocol including spirometric measurements. ResultsResting hemodynamic values were not different between the groups. Systolic central and peripheral BP, and PWV increased in both groups in response to the running exercise. Δ of all measured parameters showed no difference between the groups. ConclusionsThe acute increases of AS and BP to a maximal running regimen seem to be independent of the subjects’ training status and might therefore be an eligible training mode to maintain overall and vascular health.

Self-Selected Training Load and RPE During Resistance and Aerobic Training Among Recreational Exercisers.

This study compared training load and ratings of perceived exertion (RPE) during resistance training (RT) and aerobic training (AT) sessions at self-selected intensity. Participants were 54 recreationally trained subjects assigned to either RT or AT groups. During RT, participants performed three sets of 10 repetitions of each exercise at a self-selected intensity (load). After RT completion, participants performed one repetition maximum (1RM) and 10RM tests. During AT, participants performed a treadmill exercise at a self-selected intensity and duration (velocity and time). After AT completion, participants performed a treadmill maximal exercise test using a ramp protocol. During RT, subjects chose an intensity (43.6%-60.2% 1RM) below typical training recommendations, and RPE increased in successive exercise sets. During AT, participants chose an intensity (83.9% Heart Ratepeak) in line with typical training recommendations, and RPE increased from the first to second quartile of the session (from a mean of 3.9, standard deviation [ SD] = 1.7 to a mean of 5.4, SD = 1.7; p < .05) and remained stable thereafter. These recreationally trained participants self-selected lower RT intensities than are typically recommended for strength and hypertrophy increases (>67% 1RM) and AT intensities in line with typically recommended intensity (64%-95% HRmax) for cardiovascular fitness increases. Thus, for recreational trained individuals to perform RT at recommended intensities, specific instruction will be required.

Cerebral Microvascular Reactivity and Neurocognition in Childhood Cancer Survivors

PURPOSE: To determine the differences in cerebral microvascular reactivity (CVR) and neurocognition between childhood cancer survivors (CCS) and matched controls (CON). METHODS: Seven cancer survivors and seven matched [age, sex, and body mass index (BMI)]; healthy cancer-free controls were enrolled in the study. Each participant completed neurocognitive testing (i.e., IQ screening, memory, attention/executive, and fine motor) and a self-report survey of executive/self-regulation skills. A computer-controlled gas-blending device was used to evaluate baseline and manipulate end-tidal carbon dioxide (PetCO2). To alter brain blood flow, a PetCO2 gas challenge consisting of two square wave increases of 10 mmHg above baseline PetCO2 and a ramp protocol that decreased PetCO2 to 32 mmHg and then increased linearly to 50 mmHg over 7 mins was utilized. PetO2 was maintained at 100 mmHg. Each participant underwent brain imaging using a 3T MRI for structural and functional (BOLD) imaging. CVR (%BOLD signal change/mmHg CO2) was computed by using the robust linear least squares fit to the correlation between the two time courses. RESULTS: By design, CCS and CON were similar in age (27.1±1.1 vs. 26.0±0.8 y) and BMI (25.2±1.2 vs. 25.2±0.7 kg/m2) (all p>0.05). Baseline Pet CO2 (37.0±1.1 vs. 38.0±0.9 mmHg, p=0.34) was not significantly different between the two groups. Whole brain gray matter CVR was also not significantly different in CCS vs. CON groups for the full sequence (0.36±0.01 vs. 0.35±0.02 %BOLD/mmHg), squares waves only (0.37±0.02 vs. 0.36±0.02 %BOLD/mmHg) and ramp only (0.35±0.01 vs. 0.34±0.01 %BOLD/mmHg) (all p>0.05). The CVR variability (dCVR) was increased and model fit (R2) was significantly decreased in CCS compared with CON (p=0.004 and p=0.01, respectively) in the full sequence, but not in the square or ramp waveforms independently. No significant between-group differences were observed in neurocognitive testing. CONCLUSIONS: The data from this study suggest that childhood cancer survivors may have long-term treatment effects on microcirculation of the brain that affect CVR stability. Although this decline in brain microcirculation did not result in neurocognitive deficits, the long-term consequences of this decline in brain microvascular function have yet to be determined.

Hemodynamic and Metabolic Responses to Self-Paced and Ramp Graded Exercise Protocols

PURPOSE: Compare metabolic and hemodynamic responses between self-paced (SP) and ramp (RAMP) graded exercise testing (GXT) protocols. Given that SP is controlled for time while RAMP is not, similarities in physiological responses between protocols may support SP as a viable testing option from a time-management standpoint. METHODS: Sixteen recreationally trained men (23.7±3.0 yrs) completed two separate treadmill GXT protocols. SP consisted of five 2-min stages (10 min total) of increasing speed clamped by the Borg RPE6-20 scale. RAMP increased speed by 0.16 km/hr every 15 s until volitional exhaustion. All testing was performed at 3% incline. Oxygen consumption (VO ) was measured via indirect calorimetry; hemodynamic function was measured via thoracic impedance, and blood lactate (BLa-) was measured via portable lactate analyzer. Differences between SP and RAMP protocols were analyzed as group means by using paired samples t-tests (R Core Team (2017)). RESULTS: Maximal values for SP and RAMP were similar (p > 0.05) for VO (47.1±3.4 vs. 47.4±3.4 mL•kg-1•min-1), heart rate (198±5 vs. 200±6 beats•min-1), ventilation (158.8±20.7 vs. 159.3±19.0 L•min-1), cardiac output (26.9±5.5 vs. 27.9±4.2 L•min-1), stroke volume (145.9±29.2 vs. 149.8±25.3 mL•beat-1), arteriovenous oxygen difference (18.5±3.1 vs. 19.7±3.1 mL•dL-1), and peak BLa- (11.7±2.3 vs. 11.5±2.4 mM•L-1), respectively. CONCLUSIONS: SP elicits similar maximal metabolic and hemodynamic responses in comparison to RAMP for our sample. These results support SP as a feasible GXT protocol. Electing to utilize SP may benefit clinicians and researchers from a time-management perspective.

Reproducibility of a Ramping Protocol to Measure Cerebral Vascular Reactivity Using Functional Magnetic Resonance Imaging

Reproducibility of a Ramping Protocol to Measure Cerebral Vascular Reactivity Using Functional Magnetic Resonance Imaging

Accuracy Of The Polar M430 To Predict VO2 Using Optical Technology

There are a number of fitness watches currently on the market that can predict VO2max based upon resting heart (HR) values. Traditionally these watches have measured HR using a wireless chest transmitter but the Polar M430 uses optical technology which is built into the watch to measure HR. There is evidence that suggests this optical technology will accurately measure resting HR but there is limited information that suggests this new technology will accurately estimate VO2max PURPOSE: The purpose of this study was to compare predicted VO2max values obtained from the Polar M430 watch (M) and actual VO2max values (A) obtained from indirect calorimetry. METHODS: Seven females (age = 24.0 ± 4.5 y, BMI = 26.3 ± 5.9 kg/m2) and fourteen males (age = 24.9 ± 4.5 y, BMI = 28.1 ± 5.2 kg/m2) reported to the lab, provided their informed consent, and then were instructed to lie in a supine position to rest for 10 minutes. During this time, their information (age, height, weight, gender, self-reported training hours) was entered into the watch. Following the rest, the M430 was then fitted to the participant according to the manufacturer instructions and the resting fitness test was started in order to obtain (Pmax). A treadmill ramp protocol using indirect calorimetry was used to obtain Amax. RESULTS: There were no significant differences between Mmax and Amax (48.2±13.5 and 45.3±9.4 ml/kg/min, respectively). In males, there were no significant differences between Mmax and Amax (52.5±13.6 and 50.4±5.8 ml/kg/min, respectively). In females, there were no significant differences between Mmax and Amax (41.8±10.4 and 38.1±10.5 ml/kg/min, respectively). CONCLUSIONS: This evidence suggests that the optical technology used in the M430 provides an estimate of VO2max based upon resting HR that is comparable to a VO2max obtained via indirect calorimetry. The ability to accurately estimate VO2max under resting conditions removes many of the barriers that are associated with a true VO2max test. Removing barriers of a true VO2max test will allow individuals to quantify and make their training more efficient.

Hyperglycemia‐Induced Alteration of Brain Microvascular Endothelial Intracellular Ca Response to Ischemic Factors: Role of TRPV4 Channels

Cerebral edema is exacerbated in hyperglycemic ischemic stroke through poorly understood mechanisms. We showed previously that hypoxia and other factors present during the early hours of ischemic stroke stimulate blood‐brain barrier (BBB) Na‐K‐Cl cotransport (NKCC1) and Na/H exchange (NHE1) activities, leading to increased secretion of Na, Cl and water from blood into brain across a still intact BBB and consequent edema formation. More recently we found that BBB endothelial cells exposed to high glucose (6 hr to 7 d) exhibit increased abundance of NKCC and NHE and greater stimulation of the transporter activities by ischemic factors compared to cells maintained in normoglycemic conditions. Further, we found that the more robust edema formation observed in hyperglycemic rats is significantly attenuated by bumetanide and HOE‐642, inhibitors of NKCC1 and NHE1 activities. The present study was conducted to investigate signaling events underlying these effects of hyperglycemia on BBB Na transporters and ischemia‐induced cerebral edema with the overall goal of identifying additional therapeutic targets for diabetic ischemic stroke. Compelling evidence suggests that intracellular Ca (Cai) signaling mechanisms are likely to be involved. Exposure to high glucose is known to alter Cai dynamics in several cell types, including non‐brain endothelial cells. In addition, stimulation of NKCC and/or NHE activity by increases in Cai has been demonstrated in a variety of cell types. In recent studies we found that exposing BBB endothelial cells to high glucose for 48 hours resulted in elevated resting levels of Cai and significantly increased the abundance of the Transient Receptor Potential V4 (TRPV4) channel. The present study was conducted to further evaluate the effects of hyperglycemia on BBB endothelial cell Cai and to investigate whether TRPV4 plays a role in hyperglycemia‐induced alteration of Cai dynamics in the cells. Bovine cerebral microvascular endothelial cells (CMEC) were exposed for 24 hr to hyperglycemic (HG, 30mM glucose), normoglycemic (NG, 5mM glucose) or osmotic control media (5mM glucose + 12.5 mM NaCl) then loaded with 5μM Cal‐520‐AM and imaged after exposure (1 hr) to normoxia or hypoxia (7% O2). Calcium levels were normalized to maximal non‐saturated calcium signal following the addition of 8μM ionomycin. We found that HG CMEC exhibited a 4‐fold increase in [Cai] when exposed to hypoxia compared to a 2‐fold in NG CMEC. This effect was abolished in the presence Ca‐free media or the TRPV4 inhibitor HC067047 (1μM). Western blot evaluation of CMEC lysates following exposure to HG media (6 to 48 hr) revealed significant increases in TRPV4 abundance after 24 and 48 hr but no effect of osmotic control medium (NG media with added 12.5 mM NaCl). Using conventional perforated patch‐clamp methods and a 1‐second voltage ramp (−100 mV to +100 mV) protocol, we also found that the TRPV4 agonist GSK1016790A activated an outwardly rectifying current in the cells that was blocked by the antagonist (HC067047; 1μM), indicating the presence of TRPV4 activity in the cells. Our findings indicate that hyperglycemia exposures cause more robust hypoxia‐induced increases in BBB endothelial cell [Cai] in a TRPV4‐dependent manner.Support or Funding InformationSupported by NINDS and the American Heart AssociationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Association between exercise intensity and renal blood flow evaluated using ultrasound echo.

High-intensity exercise reduces renal blood flow (RBF) and may transiently exacerbate renal dysfunction. RBF has previously been measured invasively by administration of an indicator material; however, non-invasive measurement is now possible with technological innovations. This study examined variations in RBF at different exercise intensities using ultrasound echo. Eight healthy men with normal renal function (eGFRcys 114 ± 19mL/min/1.73m2) participated in this study. Using a bicycle ergometer, participants underwent an incremental exercise test using a ramp protocol (20W/min) until exhaustion in Study 1 and the lactate acid breaking point (LaBP) was calculated. Participants underwent a multi-stage test at exercise intensities of 60, 80, 100, 120, and 140% LaBP in Study 2. RBF was measured by ultrasound echo at rest and 5min after exercise in Study 1 and at rest and immediately after each exercise in Study 2. To determine the mechanisms behind RBF decline, a catheter was placed into the antecubital vein to study vasoconstriction dynamics. RBF after maximum exercise decreased by 51% in Study 1. In Study 2, RBF showed no significant decrease until 80% LaBP, and showed a significant decrease (31%) at 100% LaBP compared with at rest (p < 0.01). The sympathetic nervous system may be involved in this reduction in RBF. RBF showed no significant decrease until 80% LaBP, and decreased with an increase in blood lactate. Reduction in RBF with exercise above the intensity at LaBP was due to decreased cross-sectional area rather than time-averaged flow velocity.

Optimizing a Treadmill Ramp Protocol to Evaluate Aerobic Capacity of Hemiparetic Poststroke Patients.

Bernardes, WL, Montenegro, RA, Monteiro, WD, de Almeida Freire, R, Massaferri, R, and Farinatti, P. Optimizing a treadmill ramp protocol to evaluate aerobic capacity of hemiparetic poststroke patients. J Strength Cond Res 32(3): 876-884, 2018-A correct assessment of cardiopulmonary capacity is important for aerobic training within motor rehabilitation of poststroke hemiparetic patients (PSHPs). However, specific cardiopulmonary exercise testing (CPET) for these patients are scarce. We proposed adaptations in a protocol originally developed for PSHPs by Ovando et al. (CPET1). We hypothesized that our adapted protocol (CPET2) would improve the original test, by preventing early fatigue and increasing patients' peak performance. Eleven PSHPs (52 ± 14 years, 10 men) performed both protocols. CPET2 integrated changes in final speed (100-120% vs. 140% maximal speed in 10-m walking test), treadmill inclination (final inclination of 5 vs. 10%), and estimated test duration (10 vs. 8 minutes) to smooth the rate of workload increment of CPET1. Peak oxygen uptake (V[Combining Dot Above]O2peak) (20.3 ± 6.1 vs. 18.6 ± 5.0 ml·kg·min; p = 0.04), V[Combining Dot Above]O2 at gas exchange transition (V[Combining Dot Above]O2-GET) (11.5 ± 2.9 vs. 9.8 ± 2.0 ml·kg·min; p = 0.04), and time to exhaustion (10 ± 3 vs. 6 ± 2 minutes; p < 0.001) were higher in CPET2 than in CPET1. Slopes and intercepts of regressions describing relationships between V[Combining Dot Above]O2 vs. workload, heart rate vs. workload, and V[Combining Dot Above]O2 vs. heart rate were similar between CPETs. However, standard errors of estimates obtained for regressions between heart rate vs. workload (3.0 ± 1.3 vs. 3.8 ± 1.0 b·min; p = 0.004) and V[Combining Dot Above]O2 vs. heart rate (6.0 ± 2.1 vs. 4.8 ± 2.4 ml·kg·min; p = 0.05) were lower in CPET2 than in CPET1. In conclusion, the present adaptations in Ovando's CPET protocol increased exercise tolerance of PSHPs, eliciting higher V[Combining Dot Above]O2peak and V[Combining Dot Above]O2-GET, preventing earlier fatigue, and providing better physiological relationships along submaximal workloads.

Quenches across the self-organization transition in multimode cavities

A cold dilute atomic gas in an optical resonator can be radiatively cooled by coherent scattering processes when the driving laser frequency is tuned close to but below the cavity resonance. When the atoms are sufficiently illuminated, their steady state undergoes a phase transition from a homogeneous distribution to a spatially organized Bragg grating. We characterize the dynamics of this self-ordering process in the semi-classical regime when distinct cavity modes with commensurate wavelengths are quasi-resonantly driven by laser fields via scattering by the atoms. The lasers are simultaneously applied and uniformly illuminate the atoms; their frequencies are chosen so that the atoms are cooled by the radiative processes, and their intensities are either suddenly switched or slowly ramped across the self-ordering transition. Numerical simulations for different ramp protocols predict that the system will exhibit long-lived metastable states, whose occurrence strongly depends on the initial temperature, ramp speed, and the number of atoms.

Maximum Skin Wettedness after Aerobic Training with and without Heat Acclimation.

To quantify how maximum skin wettedness (ωmax); that is, the determinant of the boundary between compensable and uncompensable heat stress, is altered by aerobic training in previously unfit individuals and further augmented by heat acclimation. Eight untrained individuals completed an 8-wk aerobic training program immediately followed by 8 d of hot/humid (38°C, 65%RH) heat acclimation. Participants completed a humidity ramp protocol pretraining (PRE-TRN), posttraining (POST-TRN), and after heat acclimation (POST-HA), involving treadmill marching at a heat production of 450 W for 105 min in 37.5°C, 2.0 kPa (35%RH). After attaining a steady-state esophageal temperature (Tes), humidity increased 0.04 kPa·min. An upward inflection in Tes indicated the upper limit of physiological compensability (Pcrit), which was then used to quantify ωmax. Local sweat rate, activated sweat gland density, and sweat gland output on the back and arm were simultaneously measured throughout. Peak aerobic capacity increased POST-TRN by approximately 14% (PRE-TRN: 45.8 ± 11.8 mL·kg·min; POST-TRN: 52.0 ± 11.1 mL·kg·min, P < 0.001). ωmax values became progressively greater from PRE-TRN (0.72 ± 0.06) to POST-TRN (0.84 ± 0.08; P = 0.02), to POST-HA (0.95 ± 0.05; P = 0.03). These shifts in ωmax were facilitated by a progressively greater local sweat rate and activated sweat gland density from PRE-TRN (0.84 ± 0.21 mg·cm·min; 67 ± 20 glands per square centimeter) to POST-TRN (0.96 ± 0.21 mg·cm·min, P = 0.03; 86 ± 27 glands per square centimeter; P = 0.009), to POST-HA (1.15 ± 0.21 mg·cm·min; P < 0.001; 98 ± 35 glands per square centimeter; P < 0.001). No differences in sweat gland output were observed. A greater ωmax occurred after 8 wk of aerobic training, but ωmax was further augmented with heat acclimation, indicating only a partially increased heat loss capacity with training. These ωmax values may assist future predictions of heat stress risk in untrained/trained unacclimated individuals and trained heat-acclimated individuals.

Ramp and periodic dynamics across non-Ising critical points

We study ramp and periodic dynamics of ultracold bosons in an one-dimensional (1D) optical lattice which supports quantum critical points separating a uniform and a ${Z}_{3}$ or ${Z}_{4}$ symmetry broken density-wave ground state. Our protocol involves both linear and periodic drives which takes the system from the uniform state to the quantum critical point (for linear drive protocol) or to the ordered state and back (for periodic drive protocols) via controlled variation of a parameter of the system Hamiltonian. We provide exact numerical computation, for finite-size boson chains with $L\ensuremath{\le}24$ using exact diagonalization (ED), of the excitation density $D$, the wave function overlap $F$, and the excess energy $Q$ at the end of the drive protocol. For the linear ramp protocol, we identify the range of ramp speeds for which $D$ and $Q$ show Kibble-Zurek scaling. We find, based on numerical analysis with $L\ensuremath{\le}24$, that such scaling is consistent with that expected from critical exponents of the $q$-state Potts universality class with $q=3,4$. For the periodic protocol, we show that the model displays near-perfect dynamical freezing at specific frequencies; at these frequencies $D,Q\ensuremath{\rightarrow}0$ and $|F|\ensuremath{\rightarrow}1$. We provide a semi-analytic explanation of such freezing behavior and relate this phenomenon to a many-body version of Stuckelberg interference. We suggest experiments which can test our theory.

New Reference Values for Cardiopulmonary Exercise Testing in Children.

Cardiopulmonary exercise testing is an essential tool to assess cardiorespiratory fitness (CRF) in children. There is a paucity of adequate pediatric reference values that are independent of body size and pubertal stage. The purpose of this study is to provide Z score equations for several maximal and submaximal CRF parameters derived from a prospectively recruited sample of healthy children. In this cross-sectional multicenter study, we prospectively recruited 228 healthy children 12 to 17 yr old in local schools. We performed a symptom-limited cardiopulmonary exercise testing progressive ramp protocol on an electronically braked cycle ergometer. Eighteen CRF parameters were analyzed. We tested several regression models to obtain prediction curves that minimized residual association with age, body size, and pubertal stage. Both the predicted mean and the predicted SD were modeled to account for heteroscedasticity. We identified nonlinear association of CRF parameters with body size and significant heteroscedasticity. To normalize CRF parameters, the use of a single body size variable was not sufficient. We therefore used multivariable models with various combination of height, corrected body mass, and age. Final prediction models yielded adjusted CRF parameters that were independent of age, sex, body mass, height, body mass index, and Tanner stages. We present Z score equations for several CRF parameters derived from a healthy pediatric population. These reference values provide updated predicted means and range of normality that are independent of sex and body size. Further testing is needed to assess if these reference values increase sensitivity and specificity to identify abnormal cardiorespiratory response in children with chronic diseases.

Extracorporeal Shockwave Lithotripsy Could Lead to a Prolonged Increase in the Renal Fibrotic Process of Up to 2 Years.

This prospective study aimed to evaluate the effect of ramping and pause protocols on renal fibrosis, blood pressure control, and renal function in patients receiving extracorporeal shockwave lithotripsy (SWL). This study prospectively recruited 320 patients with solitary radiopaque renal stones <15 mm in size. Patients were randomized to receive one of four shockwave protocols: (1) standard protocol (no ramping or pause); (2) ramping protocol alone; (3) ramping and pause protocols; or (4) pause protocol alone. Spot urine samples were collected before and for 2 years after treatment to monitor the levels of the renal fibrosis marker procollagen III aminoterminal propeptide (PIIINP) by blinded research staffs. Blood pressure and serum creatinine levels were also monitored during follow-up. The four groups had comparable baseline data and treatment parameters. Significant increases (p < 0.05) in the urinary PIIINP levels from 6 weeks until 18 months after SWL were observed among all patients and in individual groups. PIIINP levels peaked at 1 year after SWL and gradually decreased to the baseline at 2 years. At the 2-year follow-up point, the overall serum creatinine levels remained significantly elevated (76.21-80.01 μmol/L, p < 0.001). Twenty (9.95%) patients developed new-onset hypertension and another 43 (36.4%) experienced worsening blood pressure control. However, no differences were observed among the four treatment groups. SWL led to significant increases in renal fibrosis marker levels for up to 18 months after treatment. However, no differences in changes in renal fibrosis marker and serum creatinine levels and worsening of blood pressure control were observed with respect to the use of either ramping or pause treatment protocols.

Pulsatile Hemodynamics Are Associated With Exercise Capacity in Patients With Exertional Dyspnea and Preserved Left Ventricular Ejection Fraction.

Pulsatile hemodynamics are associated with left ventricular filling pressures and diastolic dysfunction. We investigated their relationship with maximum workload and peak oxygen uptake (peak VO2) in patients with exertional dyspnea and preserved left ventricular ejection fraction (LVEF). Radial waveforms from tonometry were processed with a transfer function, pulse wave analysis and wave separation analysis, yielding central aortic pressures and measures of forward (amplitude of forward wave-Pf) and reflected waves (augmentation index-AIx, augmentation pressure-AP, amplitude of backward wave-Pb) and their ratio (reflection magnitude). Aortic pulse wave velocity (aoPWV) was estimated with a validated formula from single-point waveforms. Ergospirometry for assessment of exercise capacity was performed on a bicycle ergometer, using a ramp protocol. Sixty-six patients were included (43 females; mean age 66 years; 83% hypertensives; mean body mass index 28.3 kg/m2). Mean peak VO2 was 17.0 ml/min/kg, mean achieved maximum workload 104.5 watts (80.9% of a reference population). Maximum workload and peak VO2 showed significant inverse relationships with AIx, AP, Pb, and aoPWV (r = -0.26 to -0.57). In multiple adjusted regression models, brachial and aortic pulse pressure, AP, Pf, Pb, and aoPWV were significant independent predictors of maximum workload, whereas AP, AIx75, Pf, Pb, and aoPWV were independently related to peak VO2. Pulsatile hemodynamics are independently associated with objective measures of exercise capacity in patients with normal LVEF.

Cardiorespiratory Optimal Point in Professional Soccer Players: A Novel Submaximal Variable During Exercise

Abstract Background: Maximal oxygen consumption (VO2max) and ventilatory threshold (VT) obtained during a cardiopulmonary exercise test (CPX) are used in the evaluation of athletes. However, the identification of these variables may sometimes be unreliable, which limits their use. In contrast, the cardiorespiratory optimal point (COP) is a submaximal variable derived from CPX with objective measurement and prognostic significance. However, its behavior in athletes is unknown. Objective: To describe the behavior of COP in professional soccer players and its association with VO2max and VT. Methods: VO2max, VT and COP were obtained retrospectively from 198 soccer players undergoing maximal treadmill CPX using ramp protocol. COP was defined as the lowest value of the ventilation/oxygen consumption ratio in a given minute of the CPX. The soccer players were stratified according to their field position: goalkeeper, center-defender, left/right-back, midfielder and forwarder. Continuous variables were compared using unpaired Student t test or ANOVA, or Mann-Whitney test or Kruskal-Wallis test depending on their distribution, and categorical variables were compared using chi-square test. Pearson correlation was used to test the association between COP and other ventilatory variables. A level of 5% was used for statistical significance. Results: COP (mean ± SD) was 18.2 ± 2.1 and was achieved at a speed 4.3 ± 1.4 km.h-1 lower than that achieved at the VT. While VO2max (62.1 ± 6.2 mL.kg-1.min-1) tended to be lower in goalkeepers (p < 0.05), the COP did not vary according to field position (p = 0.41). No significant association was observed between COP and VO2max (r = 0.032, p = 0.65) or between COP and VT (r = -0.003, p = 0.96). Conclusion: COP can be easily determined during submaximal exercise performed with incremental speed in soccer players and does not vary according to the athlete’s field position. The absence of association with VO2max and VT indicates that COP provides distinct and complementary information to these variables. Future studies are needed to determine the practical implications of COP in assessing athletes. (Int J Cardiovasc Sci. 2018; [online].ahead print, PP.0-0)

The accuracy of two equations for predicting maximal oxygen uptake on individualized ramp protocol

PurposeValid protocols use nomograms based on standardized stages to calculate maximal oxygen uptake (VO&lt;sub&gt;2&lt;/sub&gt;max). Although the maximal ramp exercise protocol offers advantages over traditional protocols, it is not known if the non-standardized stages approach affects the accuracy to estimate VO&lt;sub&gt;2&lt;/sub&gt;max. The study aims to examine the accuracy of 2 equations for predicting VO&lt;sub&gt;2&lt;/sub&gt;max in a maximal ramp exercise test.MethodsOverall, 11 men (age: 26 ± 5 years, height: 178 ± 7 cm, weight: 77.6 ± 9.9 kg) underwent 3 sessions of a maximal ramp test on a motorized treadmill; the speed increments were equal but with 0, 3, and 6% grades. Expired gases were analysed with a portable metabolic system. The VO&lt;sub&gt;2&lt;/sub&gt;max measured was set as the highest mean value observed from 7 consecutive breaths and it was predicted from 2 equations: American College Sports Medicine (ACSM) and Myers.ResultsVO&lt;sub&gt;2&lt;/sub&gt;max predicted by ACSM equation (54.3 ± 6.7 mL • kg&lt;sup&gt;–1&lt;/sup&gt; • min&lt;sup&gt;–1&lt;/sup&gt;) was approximately 10 ± 10% higher and by Myers equation (30.6 ± 6.1 mL • kg&lt;sup&gt;–1&lt;/sup&gt; • min&lt;sup&gt;–1&lt;/sup&gt;) approximately 38 ± 11% lower than directly measured (49.6 ± 6.7 mL • kg&lt;sup&gt;–1&lt;/sup&gt; • min&lt;sup&gt;–1&lt;/sup&gt;, &lt;i&gt;p&lt;/i&gt; &lt; 0.05). Bland-Altman graphs indicate low and no agreement for ACSM and Myers equations, respectively. The calculated standard error of the estimates was 6.5 mL • kg&lt;sup&gt;–1&lt;/sup&gt; • min&lt;sup&gt;–1&lt;/sup&gt; for ACSM equation and 19.9 mL • kg&lt;sup&gt;–1&lt;/sup&gt; • min&lt;sup&gt;–1&lt;/sup&gt; for Myers equation.ConclusionsThe ACSM and Myers equations significantly over- and under-predict the VO&lt;sub&gt;2&lt;/sub&gt;max of young adults, respectively. Although the former overestimated VO&lt;sub&gt;2&lt;/sub&gt;max, we recommend its use with caution.

Assessing the Use of Wrist-Worn Devices in Patients With Heart Failure: Feasibility Study.

BackgroundExercise capacity and raised heart rate (HR) are important prognostic markers in patients with heart failure (HF). There has been significant interest in wrist-worn devices that track activity and HR.ObjectiveWe aimed to assess the feasibility and accuracy of HR and activity tracking of the Fitbit and Apple Watch.MethodsWe conducted a two-phase study assessing the accuracy of HR by Apple Watch and Fitbit in healthy participants. In Phase 1, 10 healthy individuals wore a Fitbit, an Apple Watch, and a GE SEER Light 5-electrode Holter monitor while exercising on a cycle ergometer with a 10-watt step ramp protocol from 0-100 watts. In Phase 2, 10 patients with HF and New York Heart Association (NYHA) Class II-III symptoms wore wrist devices for 14 days to capture overall step count/exercise levels.ResultsRecorded HR by both wrist-worn devices had the best agreement with Holter readings at a workload of 60-100 watts when the rate of change of HR is less dynamic. Fitbit recorded a mean 8866 steps/day for NYHA II patients versus 4845 steps/day for NYHA III patients (P=.04). In contrast, Apple Watch recorded a mean 7027 steps/day for NYHA II patients and 4187 steps/day for NYHA III patients (P=.08).ConclusionsBoth wrist-based devices are best suited for static HR rate measurements. In an outpatient setting, these devices may be adequate for average HR in patients with HF. When assessing exercise capacity, the Fitbit better differentiated patients with NYHA II versus NYHA III by the total number of steps recorded. This exploratory study indicates that these wrist-worn devices show promise in prognostication of HF in the continuous monitoring of outpatients.

Mycophenolate mofetil prevents the delayed T cell response after pilocarpine-induced status epilepticus in mice.

Growing clinical and laboratory evidence corroborates a role for the immune system in the pathophysiology of epilepsy. In order to delineate the immune response following pilocarpine-induced status epilepticus (SE) in the mouse, we monitored the kinetics of leukocyte presence in the hippocampus over the period of four weeks. SE was induced following a ramping protocol of pilocarpine injection into 4–5 weeks old C57BL/6 mice. Brains were removed at days 1–4, 14 or 28 after SE, and the hippocampi were analyzed via flow cytometry, via quantitative reverse transcriptase PCR (qRT-PCR) and via immunohistochemistry. Epileptogenesis was confirmed by Timm staining of mossy fiber sprouting in the inner molecular layer of the dentate gyrus. The flow cytometry data revealed a biphasic immune response following pilocarpine-induced SE with a transient increase in activated CD11b+ and F4/80+ macrophages within the first four days replaced by an increase in CD3+ T-lymphocytes around day 28. This delayed T cell response was confirmed via qRT-PCR and via immunohistochemistry. In addition, qRT-PCR data could show that the delayed T cell response was associated with an increased CD8/CD4 ratio indicating a cytotoxic T cell response after SE. Intriguingly, early intervention with mycophenolate mofetil administration on days 0–3 after SE prevented this delayed T cell response. These results show an orchestrated immunological sequela and provide evidence that the delayed T cell response is sensitive to early immunomodulatory intervention.

Controlling the Floquet state population and observing micromotion in a periodically driven two-body quantum system

Near-resonant periodic driving of quantum systems promises the implementation of a large variety of novel effective Hamiltonians. The challenge of Floquet engineering lies in the preparation and measurement of the desired quantum state. We address these aspects in a model system consisting of interacting fermions in a periodically driven array of double wells created by an optical lattice. The singlet and triplet fractions and the double occupancy of the Floquet states are measured, and their behavior as a function of the interaction strength is analyzed in the high- and low-frequency regimes. We demonstrate full control of the Floquet state population and find suitable ramping protocols and time-scales which adiabatically connect the initial ground state to different targeted Floquet states. The micromotion which exactly describes the time evolution of the system within one driving cycle is observed. Additionally, we provide an analytic description of the model and compare it to numerical simulations.