Minutes Of Stage Research Articles

REDUCED AEROBIC FITNESS IS ASSOCIATED WITH IMPAIRED CEREBROVASCULAR FUNCTION IN INDIVIDUALS WITH ATRIAL FIBRILLATION

INTRODUCTION & AIMS Lower aerobic fitness (V̇O2peak) is associated with higher risk of cerebrovascular disease. However, the relationship between V̇O2peak and cerebrovascular function and cerebral blood velocity at rest and during exercise has not been investigated in adults with atrial fibrillation (AF). We aimed to compare resting and exercise cerebral blood velocity responses and cerebrovascular function in individuals with AF to healthy controls. METHODS Eight inactive adults either with AF or healthy age-matched controls (AF: n=4, 64±6 years, 50% female; control: n=4, 66±4 years, 75% female) completed a maximal graded exercise test to measure V̇O2peak. Transcranial Doppler was used to measure bilateral middle cerebral artery velocity (MCAv). Vascular function was assessed by measuring MCAv increases and time to peak following a 30s hypercapnia stimulus (9% CO2, 21% O2, and balanced nitrogen), and MCAv during aerobic exercise (3-minute stages at 40%, 60% and 80% V̇O2peak). Blood pressure, heart rate and end-tidal gases were collected alongside MCAv. RESULTS Compared to controls, individuals with AF (both P<0.01) had higher BMI (AF: 31.8±2.0 kg/m2; control: 27.3±0.6 kg/m2), lower V̇O2peak (AF: 19.9±2.5 mL/kg/min; control: 33.7±5.8 mL/kg/min), and similar blood pressure. Resting right and left MCAv was higher in the AF group (R: 66.6±34.0 cm/s; L: 44.2±10.1 cm/s) compared to the control (R: 36.1±6.7 cm/s; L: 34.9±8.7 cm/s); this was not significant (P=0.121 and 0.258). Right MCAv was higher than left MCAv in individuals with AF but this was not significant (P=0.247). Hypercapnia and exercise induced MCAv and time to peak were similar between groups (P>0.05). CONCLUSION Lower V̇O2peak may be associated with increased resting MCAv in individuals with AF. Furthermore, there may be regional disparities in MCAv in individuals with AF. Future studies with larger sample sizes investigating potential mechanisms and volumetric cerebrovascular changes (e.g., vessel diameter, arterial stiffness) in AF are warranted.

L-Citrulline Supplementation Improves Leg Endothelial Function and Blood Flow Responses to Plantarflexion Exercise in Hypertensive Postmenopausal Women

Menopause and hypertension are associated with macro- and microvascular endothelial dysfunction at rest. Arginine deficiency and low nitric oxide (NO) synthesis may contribute to reduced muscle blood flow (BF) and oxygen delivery to exercising muscles. Improving BF to calf muscles may enhance physical activity. L-Citrulline supplementation (CIT) has improved resting macrovascular endothelial function via increased arginine availability for NO synthesis. Thus, the purpose of this study was to examine the effects of CIT on resting microvascular endothelial function and BF responses to plantarflexion exercise (PFE) in hypertensive postmenopausal women. We hypothesized that CIT would improve microvascular function and BF responses to PFE compared to placebo (PL). Twenty-one hypertensive postmenopausal women were randomized to 4 weeks of CIT (10g/day, n=10) or PL ( n=11). Superficial femoral macro- (flow-mediated dilation; FMD) and microvascular function (5s average peak blood velocity and flow during reperfusion) were assessed by ultrasound at 0 and 4 weeks. Femoral artery BF and vascular conductance (VC) were measured via ultrasound at rest and during 3-minute stages of rhythmic PFE at 5%, 15%, and 30% of 1-repetition maximum (1RM) at 0 and 4 weeks. BF and VC responses to PFE were analyzed as the change from rest to the last minute of each stage. There were no differences between groups in FMD, 5s peak velocity and flow during reperfusion, and vascular responses to PFE at 0 weeks. CIT significantly increased FMD (CIT:Δ1.28 ± 0.42 vs PL:Δ0.01 ± 0.40%, p = 0.04) and 5s peak velocity (CIT:Δ17.44 ± 4.21 vs PL:Δ0.09 ± 4.01 cm/s, p = 0.01) and flow (CIT:Δ220 ± 54 vs PL:Δ35 ± 51 mL/min, p = 0.02) during reperfusion compared to PL. CIT had no effect on BF and VC responses to 5% PFE ( p > 0.05). CIT significantly augmented BF responses to 15% PFE (CIT:Δ82 ± 16 vs PL:Δ22 ± 15 mL/min, p < 0.01) and 30% PFE (CIT:Δ156 ± 33 vs PL:Δ38 ± 32 mL/min, p < 0.01) and VC responses to 15% PFE (CIT:Δ0.80 ± 0.16 vs PL:Δ0.11 ± 0.15 mL*100mmHg/min, p < 0.01) and 30% PFE (CIT:Δ1.49 ± 0.29 vs PL:Δ0.24 ± 0.27 mL*100mmHg/min, p < 0.01) compared to PL. Improvements in FMD were not correlated with BF or VC responses to PFE ( p > 0.05). Improvements in 5s peak velocity were positively correlated with BF responses to 15% PFE ( r = 0.498, p = 0.02) and 30% PFE ( r = 0.532, p = 0.01), and with VC responses to 15% PFE ( r = 0.542, p = 0.01) and 30% PFE ( r = 0.633, p < 0.01). Similarly, augmented 5s flow was positively correlated with BF ( r = 0.461, p = 0.04) and VC ( r = 0.558, p = 0.01) responses to 30% PFE. These findings indicate that CIT improved superficial femoral artery macro- and microvascular endothelial function at rest. However, only improvements in microvascular endothelial function influenced vascular function during leg exercise in hypertensive postmenopausal women. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Brachial artery flow-mediated dilation during incremental handgrip exercise is not impacted by sex or female sex hormones

Sex differences exist in reactive hyperemia flow-mediated dilation (RH-FMD), with males demonstrating larger RH-FMD responses than naturally menstruating females and females using oral contraception (OC). This difference is thought to be partly attributed to sex hormones. Among females, some studies demonstrate lower RH-FMD in females using OC relative to naturally menstruating females. To date, non-invasive assessments of endothelial function in males, naturally cycling females and females using OC have only been completed using RH-FMD. Notably, due to differences in the shear stimulus during sustained shear-induced FMD (SS-FMD) versus the transient pattern observed with RH-FMD, SS-FMD may provide distinct insight into endothelial dysfunction undetected with RH-FMD. Therefore, we hypothesized that the SS-FMD responses to incremental handgrip (IHG) exercise would be greatest in males, and that females using OC would have the smallest increase in SS-FMD compared to males and naturally menstruating females. The IHG protocol consisted of 3-minute stages of rhythmic handgrip exercise at 15, 30, and 45% of an individual’s maximal voluntary contraction (MVC) force, with no rest period between MVC transitions. Brachial artery diameter and blood velocity were measured simultaneously via duplex Doppler ultrasound in 10 males (26±4 [mean±SD] years), 11 naturally menstruating females (25±4 years), and 9 females using OC (27±5 years) during IHG. Females were tested in the mid-luteal (ML) and active (high hormone) OC phases. SS-FMD and shear rate were analyzed using linear mixed model analyses. MVC was greater in males relative to both groups of females (males: 40±6, ML: 28±8, OC: 26±6 kg; One-way ANOVA: post-hocs P≤0.001). Brachial artery shear rate was not different between males, ML females or females using OC throughout exercise (group-by-stage interaction: P=0.975). Consequently, the brachial artery dilated by 1.3±1.5, 0.1±2.1, and 1.2±3.6 % at 15% MVC, 4.0±3.1, 2.7±3.3, and 4.1±4.8 % at 30% MVC, and 9.1±4.9, 7.3±5.4, and 7.6±5.9 % at 45% MVC, in males, ML females, and females using OC, respectively (all P>0.05). Furthermore, the slopes of the relationship between the change in brachial artery diameter and shear rate was similar between the three groups (Males: 0.0004±0.0002, ML: 0.0003±0.0002, OC: 0.0003±0.0002 Δmm/Δ1·s -1 ; One-way ANOVA: P=0.564). Taken together, these data indicate that endothelial function in response to sustained elevations in shear stress are not impacted by biological sex or OC use. Supported by the Natural Sciences and Engineering Research Council of Canada, and IEEM indirect funds. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pedaling cadence does not affect aerobic performance during an incremental maximal test among male and female adult cyclists

The purpose of the study was to evaluate the effect of pedaling at the energetically optimal cadence (EOC) on aerobic capacity and cycling efficiency in experienced male and female adult cyclists. Twenty-four experienced cyclists underwent a progressive, maximal metabolic exercise test on a cycling ergometer pedaling at their freely chosen cadence (FCC). EOC was determined by maintaining an output of 65% of peak power during seven consecutive 3-minute stages of cadences between 50 rpm to 110 rpm in 10 rpm increments in a randomized order. Cyclists were then randomized to either an FCC or EOC group and performed a second maximal exercise test. Oxygen consumption (VO2max), time to exhaustion (Tmax), ventilatory threshold (VO2VT) and time to ventilatory threshold (TVT) were compared between the FCC and EOC groups. Submaximal average oxygen consumption was significantly higher during FCC (85±11 rpm) than EOC (60±8 rpm; 38.2±6.64 ml/kg/min v. 35±7.7 ml/kg/min, p<0.001). There were no significant interactions between group and order of maximal exercise tests with respect to VO2max (b=1.59, p=0.38), Tmax (b=0.31, p=0.55), VO2VT (b=0.05, p=0.98) or TVT (b=0.18, p=0.82). FCC was significantly lower among female cyclists compared to male cyclists. We conclude that cycling at EOC at submaximal workloads demands less oxygen consumption than FCC, but does not significantly improve VO2max, and that there may be sex-specific differences with regards to FCC among experienced adult cyclists.

0190 Association of Sleep Spindle Activity with Cognition in Youth from the General Population

Abstract Introduction Sleep spindle activity has been increasingly studied as an underlying mechanism of cognition. In youth, it appears the relationship between spindle activity and cognition depends upon the spindle metric and cognitive domain examined. Prior research has been conducted primarily in highly selective experimental studies of typically developing youth. We aimed to clarify the relationship between spindle activity and lower and higher order cognitive functions in children and adolescents from the general population. Methods We studied 639 children aged 5-12y (median 9y) and 418 adolescents aged 12-23y (median 16y) from a population-based cohort. All subjects underwent a 9-hour, in-lab polysomnography. We calculated sleep spindle density (SSD), the total number of spindles per minute of stage 2 of non-rapid eye movement sleep, and peak spindle frequency (PSF) in the 10-16 Hz range at central, frontal and fronto-occipital derivations. Wechsler intelligence testing assessed verbal and non-verbal intelligence quotients (IQ), processing speed (coding) and working memory (digit span backward [DSB]). Multivariable-adjusted linear regression models with age, sex, race/ethnicity, body mass index, apnea/hypopnea index, and insomnia symptoms as covariates examined the association between SSD and PSF with cognitive outcomes. Results At ages 5-12, central SSD was positively associated with verbal IQ (p=0.04), non-verbal IQ (p=0.03), coding (p=0.01) and DSB (p<0.01); additionally, frontal SSD was positively associated with coding and DSB (both p<0.01) and fronto-occipital SSD with DSB (p<0.01). Also, central (p<0.01) and frontal (p=0.01) PSF was positively associated with DSB. At ages 12-23, fronto-occipital SSD was positively associated with non-verbal IQ (p=0.02), while no other statistically significant associations were observed for SSD or PSF with cognitive outcomes (all p≥0.08). Conclusion Spindle density is a strong correlate of general ability (both verbal and non-verbal IQ) in childhood, and it remains for non-verbal IQ in adolescence. Both increased spindle density and peak frequency are associated with better working memory in childhood, yet not in adolescence. These developmental differences may be due to cortical (e.g., synaptic pruning) and thalamocortical (e.g., increased myelination) maturational changes occurring during adolescence. Support (If Any) National Institutes of Health (R01MH118308, UL1TR000127)

The Self-Paced Submaximal Run Test: Associations With the Graded Exercise Test and Reliability.

To assess the reliability and construct validity of a self-paced, submaximal run test (SRTRPE) for monitoring aerobic fitness. The SRTRPE monitors running velocity (v), heart rate (HRex), and blood lactate concentration (B[La]), during three 3-minute stages prescribed by ratings of perceived exertion (RPEs) of 10, 13, and 17. Forty (14 female) trained endurance runners completed a treadmill graded exercise test for the determination of maximal oxygen consumption (VO2max), v at VO2max (vVO2max), and v at 2mmol·L-1 (vLT1) and 4mmol·L-1 (vLT2) B[La]. Within 7 days, participants completed the SRTRPE. Convergent validity between the SRTRPE and graded exercise test parameters was assessed through linear regression. Eleven participants completed a further 2 trials of the SRTRPE within a 72-hour period to quantify test-retest reliability. There were large correlations between v at all stages of the SRTRPE and VO2max (r range = .57-.63), vVO2max (.50-.66), and vLT2 (.51-.62), with vRPE 17 displaying the strongest associations (r > .60). Intraclass correlation coefficients (ICC3,1) were moderate to high for parameters v (range = .76-.84), HRex (.72-.92), and %HRmax (.64-.89) at all stages of the SRTRPE. The corresponding coefficients of variation were 2.5% to 5.6%. All parameters monitored at intensity RPE 17 displayed the greatest reliability. The SRTRPE was shown to be a valid and reliable test for monitoring parameters associated with aerobic fitness, displaying the potential of this submaximal, time-efficient test to monitor responses to endurance training.

Facemasks during aerobic exercise: Implications for cardiac rehabilitation programs during the Covid-19 pandemic

Introduction and objectivesDuring the COVID-19 pandemic, among the safety measures adopted, use of facemasks during exercise training sessions in cardiac rehabilitation programs raised concerns regarding possible detrimental effects on exercise capacity. Our study examined the cardiorespiratory impact of wearing two types of the most common facemasks during treadmill aerobic training. MethodsTwelve healthy health professionals completed three trials of a symptom-limited Bruce treadmill protocol: Without a mask, with a surgical mask and with a respirator. Perceived exertion and dyspnea were evaluated with the Borg Scale of Perceived Exertion and the Borg Dyspnea Scale, respectively. Blood pressure, heart rate and arterial oxygen saturation (SpO2) were measured at each 3-minute stage. ResultsUsing a surgical mask or a respirator resulted in a shorter duration of exercise testing. At peak capacity, using a respirator resulted in higher levels of dyspnea and perceived exertion compared to not wearing a facemask. A significant drop in SpO2 was present at the end of exercise testing only when using a respirator. There were no differences in either chronotropic or blood pressure responses between testing conditions. ConclusionsProfessionals involved in cardiac rehabilitation should be aware of the cardiorespiratory impact of facemasks. Future studies should assess whether exposure to these conditions may impact on the overall results of contemporary cardiac rehabilitation programs.

Pharmacological and simulated exercise cardiac stress tests produce different ischemic signatures in high-resolution experimental mapping studies

ObjectiveTest the hypothesis that exercise and pharmacological cardiac stressors create different electrical ischemic signatures. IntroductionCurrent clinical stress tests for detecting ischemia lack sensitivity and specificity. One unexplored source of the poor detection is whether pharmacological stimulation and regulated exercise produce identical cardiac stress. MethodsWe used a porcine model of acute myocardial ischemia in which animals were instrumented with transmural plunge-needle electrodes, an epicardial sock array, and torso arrays to simultaneously measure cardiac electrical signals within the heart wall, the epicardial surface, and the torso surface, respectively. Ischemic stress via simulated exercise and pharmacological stimulation were created with rapid electrical pacing and dobutamine infusion, respectively, and mimicked clinical stress tests of five 3-minute stages. Perfusion to the myocardium was regulated by a hydraulic occluder around the left anterior descending coronary artery. Ischemia was measured as deflections to the ST-segment on ECGs and electrograms. ResultsAcross eight experiments with 30 (14 simulated exercise and 16 dobutamine) ischemic interventions, the spatial correlations between exercise and pharmacological stress diverged at stage three or four during interventions (p<0.05). We found more detectable ST-segment changes on the epicardial surface during simulated exercise than with dobutamine (p<0.05). The intramyocardial ischemia formed during simulated exercise had larger ST40 potential gradient magnitudes (p<0.05). ConclusionWe found significant differences on the epicardium between cardiac stress types using our experimental model, which became more pronounced at the end stages of each test. A possible mechanism for these differences was the larger ST40 potential gradient magnitudes within the myocardium during exercise. The presence of microvascular dysfunction during exercise and its absence during dobutamine stress may explain these differences.

Development and Validation of a Functional Capacity Test for Collegiate Dancers.

The purpose of this study was to design and validate a peak functional capacity test that is physiologically comprehensive and appropriate in movement for dancers with broad dance backgrounds. The Seifert Assessment of Functional Capacity for Dancers (SAFD) employs commonly utilized dance movements in progressively intense 3-minute stages, continued until volitional exhaustion. A convenience sample of 13 female collegiate dancers completed a familiariza- tion trial of the SAFD, an SAFD trial, a peak treadmill test, and a second SAFD trial. Time to exhaustion, peak oxygen consumption (VO₂ peak), respiratory exchange ratio (RER), heart rate (HR), blood lactate (BLa), and rate of perceived exertion (RPE) were measured with each trial. Intraclass correlation coefficients (ICCs) were used to assess test-retest reliability, while concurrent validity was analyzed using Pearson product-moment correlations (PPMCs). Strong ICCs were found between the SAFD trials for time to exhaustion, VO₂ peak, HR, and RPE, providing evidence of test-retest reliability of the SAFD. Significant positive relationships were found between time to exhaustion, VO₂ peak, HR, BLa, and RPE for the SAFD and the treadmill test, providing evidence of concurrent validity of the SAFD. The data reported in the study provide initial evidence of reliability and validity for the SAFD.

Characterization of Aerosol Generation During Various Intensities of Exercise

BackgroundCharacterization of aerosol generation during exercise can inform the development of safety recommendations in the face of COVID-19.Research QuestionDoes exercise at various intensities produce aerosols in significant quantities?Study Design and MethodsIn this experimental study, subjects were eight healthy volunteers (six men, two women) who were 20 to 63 years old. The 20-minute test protocol of 5 minutes rest, four 3-minute stages of exercise at 25%, 50%, 75%, and 100% of age-predicted heart rate reserve, and 3 minutes active recovery was performed in a clean, controlled environment. Aerosols were measured by four particle counters that were place to surround the subject.ResultsAge averaged 41 ± 14 years. Peak heart rate was 173 ± 17 beat/min (97% predicted); peak maximal oxygen uptake was 33.9 ± 7.5 mL/kg/min; and peak respiratory exchange ratio was 1.22 ± 0.10. Maximal ventilation averaged 120 ± 23 L/min, while cumulative ventilation reached 990 ± 192 L. Concentrations increased exponentially from start to 20 minutes (geometric mean ± geometric SD particles/liter): Fluke >0.3 μm = 66 ± 1.8 → 1605 ± 3.8; 0.3-1.0 μm = 35 ± 2.2 → 1095 ± 4.6; Fluke 1.0-5.0 μm = 21 ± 2.0 → 358 ± 2.3; P-Trak anterior = 637 ± 2.3 → 5148 ± 3.0; P-Trak side = 708 ± 2.7 → 6844 ± 2.7; P-Track back = 519 ± 3.1 → 5853 ± 2.8. All increases were significant at a probability value of <.05. Exercise at or above 50% of predicted heart rate reserve showed statistically significant increases in aerosol concentration.InterpretationOur data suggest exercise testing is an aerosol-generating procedure and, by extension, other activities that involve exercise intensities at or above 50% of predicted heart rate reserve. Results can guide recommendations for safety of exercise testing and other indoor exercise activities.

Comparison of maximal lactate steady state with anaerobic threshold determined by various methods based on graded exercise test with 3-minute stages in elite cyclists

BackgroundThe maximal lactate steady state (MLSS) is defined as the highest workload that can be maintained for a longer period of time without continued blood lactate (LA) accumulation. MLSS is one of the physiological indicators of aerobic performance. However, determination of MLSS requires the performance of a series of constant-intensity tests during multiple laboratory visits. Therefore, attempts are made to determine MLSS indirectly by means of anaerobic threshold (AT) evaluated during a single graded exercise test (GXT) until volitional exhaustion. The aim of our study was to verify whether AT determined by maximal deviation (Dmax), modified maximal deviation (ModDmax), baseline LA concentration + 1 mmol/l (+ 1 mmol/l), individual anaerobic threshold (IAT), onset of blood lactate accumulation (OBLA4mmol/l) and V-slope methods based on GXT with 3-min stages provide valid estimates of MLSS in elite cyclists.MethodsTwelve elite male cyclists (71.3 ± 3.6 ml/kg/min) completed GXT (the increase by 40 W every 3 min) to establish the AT (by Dmax, ModDmax, + 1 mmol/l, IAT, OBLA4mmol/l and V-slope methods). Next, a series of 30-min constant-load tests to determine MLSS was performed. Agreement between the MLSS and workload (WR) at AT was evaluated using the Bland–Altman method.ResultsThe analysis revealed a very high (rs > 0.90, p < 0.001) correlation between WRMLSS and WRDmax and WRIAT. The other AT methods were highly (rs > 0.70) correlated with MLSS except for OBLA4mmol/l (rs = 0.67). The Bland-Altman analysis revealed the highest agreement with MLSS for the Dmax, IAT and + 1 mmol/l methods. Mean difference between WRMLSS and WRDmax, WRIAT and WR+1mmol/l was 1.7 ± 3.9 W, 4.3 ± 7.9 W and 6.7 ± 17.2 W, respectively. Furthermore, the WRDmax and WRIAT had the lowest limits of agreement with the WRMLSS. The ModDmax and OBLA4mmol/l methods overestimated MLSS by 31.7 ± 18.5 W and 43.3 ± 17.8 W, respectively. The V-slope method underestimated MLSS by 36.2 ± 10.9 W.ConclusionsThe AT determined by Dmax and IAT methods based on the cycling GXT with 3-min stages provides a high agreement with the MLSS in elite cyclists. Despite the high correlation with MLSS and low mean difference, the AT determined by + 1 mmol/l method may highly overestimate or underestimate MLSS in individual subjects. The individual MLSS cannot be properly estimated by V-slope, ModDmax and OBLA4mmol/l methods.

Effects of preferred music on physiological responses, perceived exertion, and anaerobic threshold determination in an incremental running test on both sexes.

This study aimed to investigate and compare the effects of preferred music on anaerobic threshold determination in an incremental running test, as well the physiological responses and perceived exertion at this intensity, in physically active men and women. Additionally, by using area under the curve (AUC) analysis of the parameters of interest during the graded test, we studied the effects of music at two physiological moments—before and after anaerobic threshold intensity (iAT)—in men and women. Twenty (men = 10; women = 10) healthy and active participants completed four visits to the laboratory. The first and second sessions were used for sample characterization. In the third and fourth sessions, participants performed an incremental running test (started at 7 km.h-1 with increments of 1 km.h-1 at each 3-minute stage) under preferred music and non-music conditions. Blood lactate ([Lac]), heart rate (HR), and perceived exertion were measured by two scales (RPEBorg and the estimation of time limit ‒ ETL) during all tests, and the total time of effort (TT) was considered as performance. Individual curves of the “intensity vs blood lactate” analyzed by the bissegmentation method provide the iAT and the AUC of [Lac], HR, RPEBorg, and ETL before and after the iAT attainment were calculated. The iAT for men (non-music: 11.5±0.9km.h-1 vs music: 11.6±1.1km.h-1) and women (non-music: 9.8±0.7km.h-1 vs music: 9.7±0.7km.h-1) was not affected by music, and for both sexes, there was no difference between non-music and music conditions in all variables obtained at iAT. The AUC of all variables were not affected by music before the iAT attainment. However, [Lac], HR, and RPEBorg presented higher values of AUC after iAT for the female group with preferred music. This may be due to the fact that 70% of women have increased TT under music conditions. Overall, preferred music did not affect the iAT determination in an incremental running test. However, some physiological responses and perceived exertion after iAT of female subjects seems to be influenced by preferred music.

0937 The Evaluation of Brain Maturation by REM Sleep Analyses During Puberty Using Fast Fourier Transform

Abstract Introduction Brain maturation has been associated with electroencephalogram (EEG) changes during rapid eye movement (REM) sleep. There is a higher delta power during sleep in the first decade of the human EEG and this fact might be related to puberty period. Most studies assessed EEG during wakefulness and NREM sleep. The aim of this study was to evaluate changes in the REM sleep EEG spectral analysis across puberty. Methods Twenty healthy children were studied. They were divided into two groups: early puberty (n=10, ageranging from 6 to 12) and late puberty (n=10, age= ranging from 13 to 18). Polysomnography was performed in 2 nights, one for adaptation purpose. The Tanner scales were obtained and exclusion criteria were the presence of sleep and daytime complaints at least 14 days before recruitment. Fast Fourier Transform (FFT) was performed in C3-A2 derivation throughout all night. The FFT was calculated in 4s windows and the mean of delta (0.5-2.0 Hz), delta 2 (2.0-4.0 Hz), theta (4.0-8.0 Hz), alpha (8.0 - 12.0 Hz), sigma (12.0-16.0 Hz) and beta (16.0 - 20.0 Hz) were obtained. Results We found differences during NREM and REM sleep between two groups (U-test, p&amp;lt;0.05). In REM sleep, the delta 2 (U-test, p=0.02)and theta power were higher in early puberty group (U-test p=0.04). The delta power correlated negatively with the duration in minutes of stage 1 (rs=-0.46 p&amp;lt;0.05), and the wake time after sleep onset (rs=-0.48, p&amp;lt;0.05) and correlated positively with sleep efficiency (rs=0.45, p&amp;lt;0.05). Theta power during REM sleep also correlated positively with N3 sleep stage (rs=0.45, p&amp;lt;0.05). Conclusion The REM sleep can be an extremely useful biomarker of brain function for future therapeutic protocols. The present results suggest that there are changes in REM sleep EEG throughout puberty, and that they may be related to puberty brain maturation. The hormone therapy may have an action in the REM behavioral Sleep Disorder. Future studies are need to evaluate this hypothesis. Support N/A

P1743 The contribution of left atrial dysfunction to exercise intolerance in early heart failure with preserved left ventricular ejection fraction

Abstract Background Diagnosis of early heart failure with preserved ejection fraction (HFpEF) may be challenging because exertional dyspnea is not specific for heart failure, and biomarkers and indicators of volume overload may be absent at rest. We aimed to characterize the contribution of abnormal left atrial (LA) mechanical properties to exercise intolerance in early HFpEF (normal left ventricular filling pressures at rest but elevated during exercise). Methods Diastolic stress testing (DST) was performed in 104 patients with left ventricular ejection fraction ≥50%, in sinus rhythm, and no more than LV diastolic dysfunction grade I, referred for assessment of exertional dyspnoea. Patients exercised supine cycle ergometry at 60 rpm starting with a 3-min period of low-level 25-W workload followed by 25-W increments in 3-minute stages to maximum tolerated levels. According to DST, 43 patients were diagnosed with HFpEF (average mitral E-to-annular e′ ratio [E/e′] &amp;gt; 14, and peak TR velocity &amp;gt;2.8 m/sec at maximal exertion) and 61 as non-cardiac dyspnea (NCD). During the test, two-dimensional images, mitral E/e′, peak tricuspid regurgitation (TR) velociry, and two-dimensional LA mechanical parameters (longitudinal LA strain [LASR] and strain rate [LASRR] during reservoir phase and LA stiffness assessed as a ratio of mitral E/e′ ratio to LASR) were analysed at baseline, and at peak. Results HFpEF and NCD patients were similar in regard to the LA volume index (34.4 [30.2;39.4] vs. 33.6 [28.4;37.1] ml/m2), and NT-proBNP level (132 [80;238] vs. 129 [80;197] pg/ml). As compared with NCD patients, HFpEF patients displayed reduced LA reservoir function assessed by LASR (22.3 [18.9;25.6] vs. 24.2 [21.2;29.8] % at rest, and 25.3 [21.4;30.2] vs. 29.0 [24.2;33.3] % with exercise) and LASRR (0.78 [0.58;0.96] vs. 0.90 [0.68;1.12] /s at rest, and 1.10 [0.79;1.31] vs. 1.24 [1.03;1.56] s–1 with exercise) with increased LA stiffness (0.57 [0.44;0.70] vs. 0.42 [0.30;0.49] mmHg/% at rest, and 0.61 [0.46;0.74] vs. 0.40 [0.32;0.51] mmHg/% with exercise, all P &amp;lt; 0.05). Additionally, HFpEF patients showed smaller exercise elevation in LASRR (+31 [-5;77] vs. +47 [12;85] % as compared with resting values, P &amp;lt; 0.05). Exercised LA stiffness and reservoir strain correlated with exercise LV filling pressures estimated by mitral E/e′ ratio (r = 0.72 and r =–0.35, P &amp;lt; 0.001). LA stiffness showed a good diagnostic accuracy (area under the curve 0.75), and LA stiffness &amp;gt; 0.46 mmHg/% demonstrated reasonable sensitivity (79%) and specificity (71%) to diagnose HFpEF. Neither LV global longitudinal strain and ejection fraction at rest nor their exercise-induced elevation differed between HFpEF and NCD. Conclusion Impaired LA reservoir function and increased stiffness are associated with exercise intolerance in patients with early HFpEF, while LV systolic function seems preserved in this stage of the disease. LA stiffness provides HFpEF diagnostic potential in ambulatory patients with dyspnea

Physiological and Perceptual Responses to Step-Wise and Ramp Graded Exercise Tests in Children

Step-wise graded exercise tests are common protocols to measure aerobic fitness in children but have limitations due to the nature of the increments. Modifying these tests to a ramp protocol could overcome some of these limitations. PURPOSE: To examine physiological and perceptual responses to step-wise and ramped graded exercise tests in children (n = 8; age = 13.3 ± 2.2 yrs.). METHODS: The standardized James protocol (STEP) and a modified-ramp James protocol (RAMP) were performed on a cycle ergometer on separate days. Protocol order was counterbalanced. STEP commenced with three 3-min stages, followed by 1-min stages. Work rate increases were based on body surface area. For RAMP, work rate was ramped to match the 3-min and 1-min stages of STEP. Work rate was increased until volitional exhaustion for both tests. Oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (RER) and OMNI ratings of perceived exertion for chest (RPE-chest), legs (RPE-legs) and overall (RPE-overall) were recorded at the end of each 3-minute stage and peak exercise. Physiological and perceptual responses between tests were compared using two-way repeated-measure ANOVAs and test time (TT) and peak power (PP) were compared using repeated measure t-tests. Significance was established at p<0.05. RESULTS: The physiological and RPE responses were similar between tests at the end of each 3-min submaximal stage (p>0.05). At peak exercise, absolute and relative VO2 for STEP were 2.17 ± 0.67 L∙min-1 and 42.5± 5.9 ml∙kg-1 ∙min-1. For RAMP, absolute and relative VO2peak were 2.33± 0.89 L∙min-1 and 45.3 ± 8.9 ml∙kg-1 ∙min-1. The differences were not significant. There were no differences between STEP and RAMP for peak HR (196.3 ± 9.8 bpm vs. 196.1 ± 9.7 bpm) and peak RER (1.24 ± 0.11 vs. 1.21 ± 0.06). At peak exercise, RPE-chest, RPE-leg and RPE-overall were similar between STEP (4.8 ± 4.0, 8.4 ± 2.1 and 7.6 ± 3.0, respectively) and RAMP (5.6 ± 3.4, 8.5± 2.3 and 8.0± 1.8, respectively) (p>0.05). TT and PP for STEP were 11.3± 2.5 min and 196.8 ± 70.7 W and 12.4 ± 2.4 min and 210.3 ± 65.5 W for RAMP (p=0.11 and p=0.12, respectively) CONCLUSION: Although limitations in step-wise protocols exist, submaximal and peak physiological and perceptual responses were similar to a ramp protocol. Both protocols may be appropriate in children to measure aerobic fitness.

Absolute Reliability and Concurrent Validity of the Stryd System for the Assessment of Running Stride Kinematics at Different Velocities.

García-Pinillos, F, Roche-Seruendo, LE, Marcen-Cinca, N, Marco-Contreras, LA, and Latorre-Román, PA. Absolute reliability and concurrent validity of the Stryd system for the assessment of running stride kinematics at different velocities. J Strength Cond Res 35(1): 78-84, 2021-This study aimed to determine the absolute reliability and to evaluate the concurrent validity of the Stryd system for measuring spatiotemporal variables during running at different velocities (8-20 km·h-1) by comparing data with another widely used device (the OptoGait system). Eighteen trained male endurance runners performed an incremental running test (8-20 km·h-1 with 3-minute stages) on a treadmill. Spatiotemporal parameters (contact time [CT], flight time [FT], step length [SL], and step frequency [SF]) were measured using 2 different devices (Stryd and OptoGait systems). The Stryd system showed a coefficient of variation (CV) <3%, except for FT (3.7-11.6%). The OptoGait achieved CV <4%, except for FT (6.0-30.6%). Pearson correlation analysis showed large correlations for CT and FT, and almost perfect for SL and SF over the entire protocol. The intraclass correlation coefficients partially support those results. Paired t-tests showed that CT was underestimated (p < 0.05, effect size [ES] > 0.7; ∼4-8%), FT overestimated (p < 0.05, ES > 0.7; ∼7-65%), whereas SL and SF were very similar between systems (ES < 0.1, with differences <1%). The Stryd is a practical portable device that is reliable for measuring CT, FT, SL, and SF during running. It provides accurate SL and SF measures but underestimates CT (0.5-8%) and overestimates FT (3-67%) compared with a photocell-based system.

The Effect of Physiological Performance Variables on 3000m Times in Collegiate Mid-Distance and Distance Runners

Collegiate mid-distance (MD) runners and distance (D) runners compete in the 3000m. Previous research has identified VO2max, velocity at lactate threshold (vLT), %VO2max at lactate threshold, and running economy (RE) to correlate with 3000m performance. Research is lacking on if differences in these variables, and pacing strategy, affects 3000m performance between groups. PURPOSE: To identify how physiological performance variables relate to 3000m time, and if differences in these variables, and pacing strategies, occurs between groups. METHODS: 11 male NCAA Division II runners (5 MD, 6 D) were used. Subjects completed a 3000m time trial on a synthetic 200m indoor track, where 3000m time and split times were recorded using a single-beam timing gate. A discontinuous 3-minute stage lactate threshold protocol was used to measure vLT, lactate threshold (LT), and running economy at 14.5km/h, 16km/h, and 17.5 km/h (RE14.5, RE16, RE17.5). A modified Astrand VO2max test was used to assess VO2max, with the speed set at 16.1km/h and grade increasing 2% every two minutes. RESULTS: VO2max (r=-.629), RE14.5 (r=.632), RE16 (r=.756), %VO2max at LT (r=0.675), 600-1200m time (r=.784), 1200-1800m time (r=.962), and 1800-2400m time (r=.719) significantly correlated to 3000m time (p<0.05), when merging subjects. In the D group, %VO2max at LT (r=.875), RE16 (r=.853), 600-1200m time (r=.882), and 1200-1800m time (r=.965) significantly correlated to 3000m time (p<0.05). In the MD group, 1200-1800m time (r=.932) significantly correlated to 3000m time (p<0.05), and VO2max had a trend towards significance with 3000m time (r=-.829, p=.083). Statistically different mean differences in VO2max (D=67.00±2.64 vs MD=63.56±1.52ml/kg/min), and vLT (D=15.10±0.19 vs MD=14.33±0.35km/h) was observed between groups (p<0.05). A graphical difference in pacing strategy was observed between groups. CONCLUSION: 1200-1800m time is the most important split time for 3000m performance. VO2max was the best physiological performance indicator in MD runners, and RE16 was the best physiological performance indicator in D runners. Runners should be trained differently according to their training status, to improve 3000m performance.

Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.

The pattern of sleep stages across a night (sleep architecture) is influenced by biological, behavioral, and clinical variables. However, traditional measures of sleep architecture such as stage proportions, fail to capture sleep dynamics. Here we quantify the impact of individual differences on the dynamics of sleep architecture and determine which factors or set of factors best predict the next sleep stage from current stage information. We investigated the influence of age, sex, body mass index, time of day, and sleep time on static (e.g. minutes in stage, sleep efficiency) and dynamic measures of sleep architecture (e.g. transition probabilities and stage duration distributions) using a large dataset of 3202 nights from a non-clinical population. Multi-level regressions show that sex effects duration of all Non-Rapid Eye Movement (NREM) stages, and age has a curvilinear relationship for Wake After Sleep Onset (WASO) and slow wave sleep (SWS) minutes. Bayesian network modeling reveals sleep architecture depends on time of day, total sleep time, age and sex, but not BMI. Older adults, and particularly males, have shorter bouts (more fragmentation) of Stage 2, SWS, and they transition less frequently to these stages. Additionally, we showed that the next sleep stage and its duration can be optimally predicted by the prior 2 stages and age. Our results demonstrate the potential benefit of big data and Bayesian network approaches in quantifying static and dynamic architecture of normal sleep.

Feasibility and echocardiographic characteristics of a three-minute stage dobutamine stress test in healthy dogs

Introduction. Dobutamine stress test (DST) is used as a method of functional cardiac examination in human medicine due to dobutamine?s effect, which is similar to moderate physical exercise. The aim of this study was to assess the feasibility and echocardiographic characteristics of a conventional DST in dogs. Materials and Methods. Ten clinically healthy German Shepherd dogs were submitted to a conventional 3-minute stage DST protocol (the initial dose 7.5 ?g/kg/min was increased at 3-minute intervals by 5 ?g/kg/min until a maximum dosage of 42.5 ?g/kg/ min; the maximum DST duration was 24 minutes), which is used in human medicine. Dobutamine action was monitored by noninvasive diagnostic methods (simultaneously lead II electrocardiography and transthoracic echocardiography). Left ventricular echocardiographic parameters were measured at baseline and at the peak of DST. Results and Conclusions. The duration of conventional DST in dogs was 19.4?4.06 minutes. During the DST, sinus tachycardia was registered with no abnormalities of cardiac rhythm. The adverse effects registered in this study were excitement, panting and weakness. Interventricular septum thickness in systole (P=0.0093) and diastole (P=0.0080) increased significantly at the peak of DST. The left ventricular end-systolic dimension (P=0.0077) and the diastolic wall stress index (P=0.0125) decreased significantly at the peak of DST. A 3-minute stage with increased doses of dobutamine is a feasible method for the DST in dogs. The registered changes could be explained by the dobutamine effects through ?1 adrenergic receptors. This pharmacological stress test induces significant changes in left ventricular echocardiographic parameters in healthy adult dogs. Dogs exhibit transient signs like sinus tachycardia, excitement, panting and weakness during DST. Additional research on DST should evaluate the diagnostic value of this protocol in dogs suffering from cardiac disease.

A Submaximal Running Test With Postexercise Cardiac Autonomic and Neuromuscular Function in Monitoring Endurance Training Adaptation.

Vesterinen, V, Nummela, A, Laine, T, Hynynen, E, Mikkola, J, and Häkkinen, K. A submaximal running test with postexercise cardiac autonomic and neuromuscular function in monitoring endurance training adaptation. J Strength Cond Res 31(1): 233-243, 2017-The aim of this study was to investigate whether a submaximal running test (SRT) with postexercise heart rate recovery (HRR), heart rate variability (HRV), and countermovement jump (CMJ) measurements could be used to monitor endurance training adaptation. Thirty-five endurance-trained men and women completed an 18-week endurance training. Maximal endurance performance and maximal oxygen uptake were measured every 8 weeks. In addition, SRTs with postexercise HRR, HRV, and CMJ measurements were carried out every 4 weeks. Submaximal running test consisted of two 6-minute stages at 70 and 80% of maximum heart rate (HRmax) and a 3-minute stage at 90% HRmax, followed by a 2-minute recovery stage for measuring postexercise HRR, HRV, and CMJ test. The highest responders according to the change of maximal endurance performance showed a significant improvement in running speeds during stages 2 and 3 in SRT, whereas no changes were observed in the lowest responders. The strongest correlation was found between the change of maximal endurance performance and running speed during stage 3, whereas no significant relationships were found between the change of maximal endurance performance and the changes of postexercise HRR, HRV, and CMJ. Running speed at 90% HRmax intensity was the most sensitive variable to monitor adaptation to endurance training. The present submaximal test showed potential to monitor endurance training adaptation. Furthermore, it may serve as a practical tool for athletes and coaches to evaluate weekly the effectiveness of training program without interfering in the normal training habits.