Differences In Heart Rate Responses Research Articles

Consumption of probiotic SLAB51 enhances ventilatory acclimatization to high altitude

Ventilatory acclimatization to hypoxia (VAH) is crucial for adjusting to physiologically stressful high-altitude environments. Increased ventilatory and cardiac responses to low-oxygen (O2) may partially mitigate deleterious effects at high altitude. Previous studies show that administration of the probiotic SLAB51 (O2booster; Hecto, Seoul, South Korea) improves O2 saturation in patients suffering from COVID-19 and O2-treated prematurely born babies. Since changes in ventilation may contribute to increase O2 saturation, we hypothesize that acute administration of SLAB51 to sojourners traveling to high altitude will increase respiratory responses to hypoxia. We measured minute ventilation (VI) and heart rate (HR) during normoxia and acute isocapnic hypoxia in 17 healthy participants (9 males, 8 females) of Latino ancestry with residence at sea level in San Diego and surrounding areas. We performed control experiments at sea level and then the participants were taken to White Mountain Barcroft Station (12,470ft / 3,800m) to repeat the measurements. At high altitude, the participants underwent a double-blind, placebo-controlled study with administration of placebo (n=8) or SLAB51 probiotic (n=9) up to three times per day for up to four days. Recordings of physiological parameters were obtained during steady-state at different gas mixtures with continuous monitoring of O2 saturation to target 10% desaturation during the acute hypoxia stimulus. We measured hypoxic ventilatory and heart rate responses (HVR and HHRR, respectively) and compared results between placebo and probiotic groups (mean ± SEM). As expected, high altitude increased VI and HR values compared to sea-level measurements in all participants. However, at high altitude, we found a significant increase of VI (p<0.02) in participants consuming SLAB51 (0.275+0.015 L/min per Kg) when compared to those administered with placebo (0.207±0.025 L/min per Kg) during exposure to acute hypoxia. Administration of SLAB51 did not produce differences in HR responses at high altitude, and HVR and HHRR were not significantly different with SLAB51 treatment. Our results show that consumption of the probiotic SLAB51 increases ventilatory responses to hypoxia at high altitude without affecting hypoxia-induced changes in HR, suggesting that SLAB51 probiotic intervention may contribute to ventilatory acclimatization to hypoxia, although future studies are required to determine the mechanisms underlying this potential response. Supported by LEA Altitude Performance Fund. 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.

Differences in heart rate responses to upright posture are associated with variations in the high-frequency power of heart rate variability.

High resting heart rate is a cardiovascular risk factor, but limited data exist on the underlying hemodynamics and reproducibility of supine-to-upright increase in heart rate. We recorded noninvasive hemodynamics in 574 volunteers [age, 44.9 yr; body mass index (BMI), 26.4 kg/m2; 49% male] during passive head-up tilt (HUT) using whole body impedance cardiography and radial artery tonometry. Heart rate regulation was evaluated using heart rate variability (HRV) analyses. Comparisons were made between quartiles of supine-to-upright heart rate changes, in which heart rate at rest ranged 62.6-64.8 beats/min (P = 0.285). The average upright increases in heart rate in the quartiles 1-4 were 4.7, 9.9, 13.5, and 21.0 beats/min, respectively (P < 0.0001). No differences were observed in the low-frequency power of HRV, whether in the supine or upright position, or in the high-frequency power of HRV in the supine position. Upright high-frequency power of HRV was highest in quartile 1 with lowest upright heart rate and lowest in quartile 4 with highest upright heart rate. Mean systolic blood pressure before and during HUT (126 vs. 108 mmHg) and the increase in systemic vascular resistance during HUT (650 vs. 173 dyn·s/cm5/m2) were highest in quartile 1 and lowest in quartile 4. The increases in heart rate during HUT on three separate occasions several weeks apart were highly reproducible (r = 0.682) among 215 participants. To conclude, supine-to-upright increase in heart rate is a reproducible phenotype with underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. As heart rate at rest influences prognosis, future research should elucidate the prognostic significance of these phenotypic differences.NEW & NOTEWORTHY Subjects with similar supine heart rates are characterized by variable increases in heart rate during upright posture. Individual heart rate increases in response to upright posture are highly reproducible as hemodynamic phenotypes and present underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. These results indicate that resting heart rate obtained in the supine position alone is not an optimal means of classifying people into groups with differences in cardiovascular function.

Effect of age and flying experience on heart rate response of fighter aircrew during high-G exposure in the high-performance human centrifuge

Objectives: Institute of Aerospace Medicine Indian Air Force regularly conducts high-G training in the human rated high-performance human centrifuge (HPHC) for fighter aircrew. It was hypothesized that the cardiovascular response of young and inexperienced pilots who undergo training in the HPHC may be different from the elder and experienced pilots as age and flying experience may have some effect on the CVS response to high-G exposure. Material and Methods: A retrospective analysis of the heart rate data from the data bank of the department of acceleration physiology and spatial orientation was done to understand differences in heart rate response between young and older fighter aircrew. Results: A total of 624 successful HPHC runs were evaluated for the baseline heart rate (before high-G exposure), peak heart rate (PHR) (during the exposure), and heart rate after the exposure of the run. The mean age, height, and weight of the subjects were 27.62 ± 5.5 years, 175.31 ± 4.8 cm, and 72.81 ± 8.4 kg, respectively. Student’s t-test revealed that there was a significant difference in the basal heart rate and PHR during the high-G exposure between young, inexperienced, and older experienced pilots. Higher basal heart rate and PHR during high-G exposure among younger pilots could be explained by anxiety due to inexperience and a tendency to pull harder in comparison to other pilots who with experience tend to be more adjusted and pull slower to meet the desired G-level during the high-G training. Conclusion: The cardiovascular response during exposure to a high-G environment is significantly different between young, inexperienced pilots, and other senior pilots.

DIFFERENCES IN PHYSIOLOGICAL LOAD OF STUDENTS DURING NORDIC WALKING AND JOGGING

Physical activity is important for the physical and mental health of almost everyone. Nordic walking is a physical activity in which participants use specially designed poles while walking, while the term jogging implies light running at speeds less than 10 km/h. PURPOSE: The aim of this research is to monitor the load intensity in real conditions, using a heart rate monitor Team Polar System, during nordic walking and jogging and comparing possible differences in heart rate responses after the fifth minute of activity, at an average speed of 7.5km/h. METHODS: The assessment of heart rate responses for this research was conducted on the 30 male students, at 2 separate days. RESULTS: The results of the variables used in this study show statistically significant differences at the level of significance p=.000. From the mean value results (M) it is obvious that the respondents achieved higher results of heart rate responses during nordic walking compared to the identical tests applied during jogging. CONCLUSION: The results of this study indicate that both Nordic walking and jogging are beneficial but Nordic walking contributes more in achieving higher body loads resulting in increased oxygen consumption and thus calories Key words: load intensity, heart rate, nordic walking, jogging

0157 Physiological responses to acute psychosocial stress in adolescents with insomnia

Abstract Introduction Insomnia often develops during adolescence, with girls being at greater risk than boys. Alterations in response to psychosocial stress have been linked to the etiology of the disorder, but it remains unclear whether the reactivity of the major stress systems (hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS)) in response to stress is altered in adolescents with insomnia. Methods Forty-seven post-pubertal adolescents (age range: 16-20 years, 28 female) with (N=16; insomnia group) and without (N=31; control group) insomnia symptomatology underwent two randomized nights of polysomnographic (PSG) laboratory recordings. Participants underwent an experimental pre-bedtime stress anticipation protocol (stress night) and a control night during which they engaged in neutral activities before bedtime. The morning after the stress night, participants underwent the Trier Social Stress Test (TSST), a standardized protocol that requires participants to complete verbal and arithmetic tasks in front of observers. On both nights, heart rate (HR) was measured across the night and cortisol was collected upon awakening and 30 minutes later to calculate cortisol awakening responses (CAR). Stress perception, salivary cortisol (HPA activity), and HR were measured during the TSST. Results There were no differences in nocturnal HR recovery or in the CAR on the stress night compared with the control night in either group. Morning pre-TSST stress levels did not differ between groups. Both groups exhibited significant increases in HR in response to the TSST (p&amp;lt; 0.05). HR was higher in girls compared to boys in the control group at baseline (p&amp;lt; 0.05). Potential group differences in HPA responses to the TSST were inconclusive due to the apparent confounding effect of the CAR on cortisol responses to stress: many participants did not show a cortisol response to the task and larger CARs were associated with an attenuated cortisol response. Conclusion There were no significant differences in HR responses to anticipation of experimental stress during the night or in response to the morning TSST between adolescents with and without insomnia. Further work is needed to examine whether altered responses to stress may emerge if insomnia becomes chronic. Support (if any) This study was supported by the National Heart, Lung and Blood Institute (NHLBI) grant R01HL139652(MdZ).

The Acute Effects of a Single Dose of Molecular Hydrogen Supplements on Responses to Ergogenic Adjustments during High-Intensity Intermittent Exercise in Humans.

This research examined the effects of single-dose molecular hydrogen (H2) supplements on acid-base status and local muscle deoxygenation during rest, high-intensity intermittent training (HIIT) performance, and recovery. Ten healthy, trained subjects in a randomized, double-blind, crossover design received H2-rich calcium powder (HCP) (1500 mg, containing 2.544 μg of H2) or H2-depleted placebo (1500 mg) supplements 1 h pre-exercise. They performed six bouts of 7 s all-out pedaling (HIIT) at 7.5% of body weight separated by 40 s pedaling intervals, followed by a recovery period. Blood gases’ pH, PCO2, and HCO3− concentrations were measured at rest. Muscle deoxygenation (deoxy[Hb + Mb]) and tissue O2 saturation (StO2) were determined via time-resolved near-infrared spectroscopy in the vastus lateralis (VL) and rectus femoris (RF) muscles from rest to recovery. At rest, the HCP group had significantly higher PCO2 and HCO3− concentrations and a slight tendency toward acidosis. During exercise, the first HIIT bout’s peak power was significantly higher in HCP (839 ± 112 W) vs. Placebo (816 ± 108 W, p = 0.001), and HCP had a notable effect on significantly increased deoxy[Hb + Mb] concentration during HIIT exercise, despite no differences in heart rate response. The HCP group showed significantly greater O2 extraction in VL and microvascular (Hb) volume in RF during HIIT exercise. The HIIT exercise provided significantly improved blood flow and muscle reoxygenation rates in both the RF and VL during passive recovery compared to rest in all groups. The HCP supplement might exert ergogenic effects on high-intensity exercise and prove advantageous for improving anaerobic HIIT exercise performance.

Heart Rate Responses and Cardiovascular Adaptations to Resistance Training Programs Differing in Set Configuration: A Randomized Controlled Trial

ABSTRACT Purpose: This study explored the changes in blood pressure and cardiac autonomic modulation after training programs differin in set configuration. Methods: Thirty-nine individuals were randomly assigned to a traditional, rest-redistribution, or control group. Throughout five weeks, the traditional and rest-redistribution groups performed 10 sessions of four exercises with the same load, number of repetitions, and total rest time, but with different inter-set rest duration and frequency (traditional group: 4 sets of 8 repetitions, 10 repetition maximum load, 5 min rest between sets and exercises; rest-redistribution group: 16 sets of 2 repetitions, 1 min rest between sets, 5 min rest between exercises). Heart rate and heart rate recovery were recorded during each training session, and heart rate variability, baroreflex sensitivity and effectiveness, blood pressure, and blood pressure variability were evaluated at rest bedore and after the interventions. Results: During the sessions, traditional sets entailed greater peak heart rate compared to rest-redistribution (P = .018) but mean heart rate, minimum heart rate, and heart rate recovery were similar between training programs (P >.05). Baroreflex effectiveness was reduced after the traditional intervention (P = .013). No changes were detected for the rest of the cardiovascular variables obtained at rest after intervention (P > .05). Conclusions: Despite some differences in heart rate response during exercise, neither traditional nor rest-redistribution resistance training protocols produced changes in cardiac autonomic modulation, sympathetic vasomotor tone, and cardiac baroreflex sensitivity of young healthy active individuals. However, traditional sets affected the baroreflex effectiveness.

Relative bradycardia in patients with COVID-19

IntroductionRelative bradycardia(RB) is a relatively low heart rate response to rise in body temperature that occurs in several infectious diseases and can be an important clinical sign. In previous case reports, RB was presented in some patients with Coronavirus disease 2019 (COVID-19) COVID-19.Objective and MethodsTo investigate the correlation between temperature and heart rate, we retrospectively reviewed 249 febrile patients with documented COVID-19 patients. RB was defined as a rise in the heart rate from a basal heart rate of less than 10 beats/minute/°C rise in temperature.ResultsIn this study, the prevalence of RB in patients with COVID-19 was 60.6%. When the HR at peak temperatures for patients with COVID-19 were compared with reference valve (general temperature-heart rate response in infectious disease), our findings demonstrate a relatively lower heart rate at all peak temperatures recorded. Despite differences in heart rate response, there were not significant differences in clinical outcomes (pulmonary manifestation, intensive care unit admission, Death).ConclusionsMost patients with COVID-19 are associated with relative bradycardia, not related to clinical outcomes. RB in COVID-19 can be considered as the clinical features for differential diagnosis from other febrile conditions.

Influence of Menstrual Cycle or Hormonal Contraceptive Phase on Physiological Variables Monitored During Treadmill Testing

Purpose: To examine the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on physiological variables monitored during incremental treadmill testing in physically active women (eumenorrheic, EUM = 16 and monophasic HC-users, CHC = 12).Methods: Four running tests to exhaustion were performed at bleeding, mid follicular (mid FOL)/active 1, ovulation/active 2, and mid luteal (mid LUT)/inactive. HC and MC phases were confirmed from serum hormones. Heart rate (HR), blood lactate (Bla), and O2 were monitored, while aerobic (AerT) and anaerobic (AnaT) thresholds were determined. O2peak, maximal running speed (RUNpeak), and total running time (RUNtotal) were recorded.Results: No significant changes were observed in O2 or Bla at AerT or AnaT across phases in either group. At maximal effort, absolute and relative O2peak, RUNpeak, and RUNtotal remained stable across phases in both groups. No significant fluctuations in HRmax were observed across phases, but HR at both AerT and AnaT tended to be lower in EUM than in CHC across phases.Conclusion: Hormonal fluctuations over the MC and HC do not systematically influence physiological variables monitored during incremental treadmill testing. Between group differences in HR at AerT and AnaT underline why HR-based training should be prescribed individually, while recording of MC or HC use when testing should be encouraged as phase may explain minor, but possibly meaningful, changes in, e.g., Bla concentrations or differences in HR response.

Food olfactory cues reactivity in individuals with obesity and the contribution of alexithymia

Obesity has been associated with increased reward sensitivity to food stimuli, but a few studies have addressed this issue by using odors. This study investigated whether obesity is associated with increased liking and wanting of food odors and whether alexithymia, a psychological construct characterized by diminished affective abilities, contributes to altered responsiveness to food. Liking and wanting for food and pleasant non-food odors were measured through explicit (self-report ratings) and implicit measures (heart rate and skin conductance) in 23 women with healthy weight (HW) and 20 women with overweight/obesity (OW/OB). Differently from the HW group, the OW/OB group explicitly liked food odors less than non-food odors; but, at the implicit level, there were no differences in heart rate response for both types of odors, indicating that they were equally liked. Moreover, at variance with the HW group, the OW/OB group did not exhibit increased skin conductance response for food compared to nonfood odors. Alexithymia was associated with increased implicit liking and explicit wanting of food odors, in particular in the HW group. These findings show that obesity is characterized by high levels of implicit food liking and low levels of implicit food wanting. Moreover, both affective and motivational responses to food reward seem to be affected by alexithymia, which should be taken into account by studies evaluating the effect of cue exposure intervention for obesity treatment.

Sex differences in heart rate responses to postural provocations

Sex differences are known in several facets of cardiac electrophysiology, mostly concerning myocardial repolarisation. In this study, heart rate and heart rate variability (HRV) responses to postural provocations were compared in 175 and 176 healthy females and males, respectively (aged 33.1 ± 9.1 years). Two different postural provocative tests with position changes supine→sitting→standing→supine and supine→standing→sitting→supine (15-min standing, 10-min other positions) were performed up to 4 times in each subject. Heart rate and heart rate variability spectral indices were measured in 5-min windows before positional changes. At supine position, females had averaged heart rate approximately 5 beats per minute (bpm) faster than males and this sex difference was practically constant during the postural changes. In both sexes, change supine→sitting and supine→standing increased heart rate by approximately 10 and 30 bpm, respectively, with no statistical differences between the sex groups. At supine baseline, females had normalised high frequency components (nHF) of HRV approximately 7% larger compared to males (p < 0.001). While the same difference in nHF was found at sitting, the change to standing position lead to significantly larger nHF reduction in females compared to males (mean changes 22.5 vs 17.2%, p < 0.001). This shows that despite similar heart rate increase, females respond to standing by more substantial shifts in cardiac sympatho-vagal modulations. This makes it plausible to speculate that the differences in autonomic reactions to stress contribute to the known sex-differences in psychosocial responses to stressful situations and to the known difference in susceptibility to ventricular fibrillation between females and males.

Characterization of Heart Rate Response During Frontside and Backside Wave Riding in an Artificial Wave Pool

There are currently no published data describing the kinetics of the heart rate (HR) response during frontside and backside wave riding on a surfboard, or for wave riding bouts longer than 15 seconds. The purpose of this study was to characterize the HR response of surfers performing frontside and backside wave riding in an artificial wave pool that allowed surfers to ride waves for up to 60 seconds. It was hypothesized that HR response would differ between the two surfing orientations, because their levels of complexity are perceived to be different by surfers. Twenty male (n=17) and female (n=3) junior professional athletes (14.7 ± 1.2 years old) participated in this study. Following parental consent, participants completed a questionnaire and were instrumented with a HR monitor (Polar RCX5 Sports Watch), which recorded HR at 1-second intervals. Researchers initiated HR sampling prior to surfer participation in a one-hour surf session in an artificial wave pool (Kelly Slater Wave Co) and synchronized HR with video recordings of wave riding. Seven subjects that did not ride at least one frontside and backside wave were excluded from the analysis. The average duration of the wave ride was 33.2 ± 8.4 seconds. Average and peak HR while wave riding was 174.1 ± 12.6 and 184.9 ±13.0 bpm, respectively. There were no significant differences in HR response or wave riding duration between frontside and backside directions. These results provide insight into the cardiovascular requirements of wave riding in an artificial wave pool.

A Comparative Study of Bisoprolol with Carvedilol on LV Systolic Function in Patients with Chronic Heart Failure

Background: Chronic heart failure (CHF) is the most common and prognostically unfavorable outcome of many diseases of the cardiovascular system. Recent data suggest that beta-blockers are beneficial in patients with CHF. Among β-blocker class of drugs, bisoprolol is a highly selective β1-adrenergic receptor blocker whereas Carvedilol is non-selective. Many large-scale trials have confirmed that both these β-blockers are superior to placebo and other β-blockers. This study was designed to compare the effects of carvedilol and bisoprolol in patients with chronic HF in a single center.Methods: It was a quasi experimental study. A total of 288 cases of heart failure were selected by purposive sampling, from January 2017 to June 2017. Each patient was allocated into either of the two groups, and was continued receiving treatment with either bisoprolol (Group-I) or carvedilol (Group-II). Each patient was evaluated clinically and echocardiographically at the beginning of treatment (baseline) and at the end of 3rd month. Echocardiography was performed to find out change in left ventricular systolic function.Result: After 3 months of treatment, ejection fraction was found higher in the bisoprolol group (42.6 ± 6.5 versus 38.3 ± 4.6%; P &lt; 0.05). Ejection fraction (EF) changes were 8.4% in bisoprolol group and 4.1% in carvedilol group. A significant reduction in left ventricular end-systolic volume (21.9±2.5 in group I versus 14.9±5.7 in group II; P &lt; 0.05) and left ventricular systolic diameter (3.2±0.1 in group I versus 2.3±0.5 in group II; P&lt;0.05) occurred after 3 months of treatment. But no significant differences were observed in left ventricular end-diastolic volume (10.1±3.2 versus 6.1±6.4; P=0.101) and left ventricular diastolic diameter (1.7±0.8 versus 1.3±0.8; P=0.081) between groups. Three months after treatment, heart rate was reduced in the bisoprolol group from 87.7±9 to 74.5±8.1 and carvedilol group from 88.8±9.1 to 80.1±8.7. Differences in heart rate responses between 2 groups were not statistically significant (P=0.113). Assessment of blood pressure three months later of treatment shows, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were improved in both group but difference between two groups were statistically non significant (p&gt;0.05).Conclusion: In this study, bisoprolol was superior to carvedilol in increasing left-ventricular ejection fraction, improving left ventricular end systolic volume and left ventricular end systolic diameter but no significant difference was observed in LV end diastolic volume, LV end diastolic diameter, heart rate and blood pressure.University Heart Journal Vol. 14, No. 1, Jan 2018; 3-8

Heart Rate Monitoring in Basketball: Applications, Player Responses, and Practical Recommendations.

Berkelmans, DM, Dalbo, VJ, Kean, CO, Milanović, Z, Stojanović, E, Stojiljković, N, and Scanlan, AT. Heart rate monitoring in basketball: applications, player responses, and practical recommendations. J Strength Cond Res 32(8): 2383-2399, 2018-The aims of this review were to collate the existing literature encompassing heart rate (HR) monitoring in basketball to (a) identify the applications of HR measurement; (b) report HR responses in male and female players during training and game-play; (c) evaluate use of current HR-based training load models; and (d) provide recommendations for future research and best practice approaches for basketball practitioners. Heart rate monitoring in basketball carries 3 primary applications: (a) monitoring exercise intensity; (b) assessing player fatigue status; and (c) quantifying internal training load. When interpreting the available training and game-play HR data in basketball players, key differences have been observed between playing positions and playing levels. Sex- and age-based differences in HR responses during basketball training and game-play are apparent across separate studies; however, further research exploring HR responses in wider player groups is needed, especially in female and junior players. There is also a lack of research directly comparing player HR responses during training and game-play to ascertain the effectiveness of different drills in preparing players for competition. Heart rate-based models have been frequently used to quantify the internal training load in basketball players, including Banister's Training Impulse (TRIMP), Lucia's TRIMP, and Edwards' Summated-Heart-Rate-Zones (SHRZ). The SHRZ model seems to hold practical advantages and better detect changes in player responses across training cycles compared with other approaches. Practical outcomes of this review center on recommendations for position-specific training plans, drills to promote desired cardiovascular stress, analysis of HR outcome measures, and ideal training load monitoring approaches.

Differences in Heart Rate Response and Recovery After 6-Minute Walk Test Between Patients With Atrial Fibrillation and in Sinus Rhythm

Long-term heart rate (HR) control is a management strategy for patients with chronic atrial fibrillation (AF). Nevertheless, the optimal target HR of AF patients is debatable. Our aim was to study HR at rest, during, and after a 6-minute walk test (6MWT) in AF patients, compared with controls with sinus rhythm (SR). Consecutive matched patients with AF (n = 186) or SR (n = 172) were recruited, and 6MWT was performed. HRs at rest, during 6MWT, and recovery periods were recorded. All subjects were divided into 5 subgroups (<80 beats/min, 80 to 89 beats/min, 90 to 99 beats/min, 100 to 109 beats/min, and ≥110 beats/min) according to the HR at rest. No statistical difference was observed in baseline HR at rest, between AF and SR groups (p = 0.30). The exercise HR increase percentage was significantly higher in overall AF patients compared with those in SR (40 ± 15% vs 14 ± 7%, p <0.001). Even with similar mean baseline HRs at rest, the 5 AF subgroups all showed significantly higher mean exercise HR, maximal exercise HR, and maximal exercise HR increase percentage compared with their respective SR subgroups, especially the subgroups with HR at rest >90 beats/min. Unlike the SR patients, the 4 AF subgroups with HR >80 beats/min at the fifth minute after 6MWT did not recover to at rest levels. In conclusion, HR increased excessively during 6MWT and HR recovery was delayed after 6MWT in AF patients, especially when HR at rest is >90 beats/min. The optimal initial HR at rest for AF patients should perhaps be <90 beats/min.

Sex Differences in Heart Rate Response to Isometric Handgrip Exercise with Concurrent Contralateral Forearm Somatosensory Stimulation

BackgroundPharmacological evidence indicates that baseline cardiovagal mechanisms determine the rapid heart rate (HR) response to the onset of moderate intensity isometric handgrip (IHG) exercise. The HR response at exercise onset expresses sex differences, being less in females. Further, somatosensory nerve stimulation (STIM) appears to affect baseline cardiovagal control in some supine participants.ObjectiveThis study explored the effect of STIM on HR and heart rate variability (HRV) during short‐duration moderate‐intensity IHG in supine healthy adults and explored whether this effect expresses sex differences.ParticipantsTwenty‐four young healthy individuals aged 23 ± 1.9 years (18 females (F): 165 ± 7.4cm, 63 ± 13kg, BMI 23 ± 2kg/m2; 6 males (M): 179 ± 2.2cm, 79 ± 11kg, BMI 25 ± 3.3kg/m2).MethodsParticipants performed six isometric handgrips with their right hand at 30 to 40% of their maximal grip strength, each lasting 20 to 30 seconds and separated by one minute of rest. Three of these IHG contractions were performed during simultaneous administration of sub‐motor STIM provided by transcutaneous electrical nerve stimulation (TENS; 100 Hz, 50 μs) on the medial contralateral forearm through anesthetized skin for the duration of the handgrip. A 3‐lead ECG provided R‐R interval data. Systolic (SBP) and diastolic blood pressure (DBP) were monitored, as well as, heart rate (HR), root mean square of successive differences in R‐R intervals (RMSSD) as a measure of HRV, and respiration. Data were analysed using two‐factor ANOVA with Bonferroni correction, and independent t‐tests.ResultsThe ΔHR from baseline to IHG without STIM was greater in males compared to females (12 ± 6bpm versus 6 ± 6bpm, respectively; d = 1.00). No differences in ΔHR were detected for either sex when STIM was added to the IHG. Of the 18 F participants, 4 provided a minimal HR response (ΔHR &gt; 4bpm) to the IHG without STIM (F1: 77 to 79bpm; F2: 69 to 70 bpm; F3: 50 to 50bpm; F4: 62 to 62 bpm) which resolved in 3 of the 4 F participants with application of STIM (F1:73 to 83bpm; F3: 45 to 59bpm; F4: 54 to 60bpm). Further, no statistically significant differences were observed in ΔRMSSD from baseline to IHG without STIM (p = 0.0321; M: 77 ± 68ms to 30 ± 145ms; F: 74 ± 38ms to 54 ± 39ms) and with STIM (p = 0.953; M: −28 ± 61ms and F: −30 ± 21ms).ConclusionOur preliminary findings suggest that, in supine individuals, sex differences exist in the HR response at the exercise onset but these effects are not modified by concurrent sub‐motor somatosensory nerve stimulation.Support or Funding InformationSupported by Natural Science and Engineering Research Council of CanadaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Anxiety, hostile attributions, and differences in heart rate response to ambiguous situational vignettes in adolescents.

Theoretically, subjective levels of anxiety and hostile attributions of intent may affect physiological responding to ambiguous social situations. This study examined youths' (n = 80 aged 11-17 years; 51% female; 37.5% African American) physiological responding (i.e., heart rate [HR]) to a series of animated vignettes depicting ambiguous social situations. Anxiety, aggression, hostile attributional bias (HAB), and their interactions were tested as predictors of differential physiological responding to the vignettes. Results indicated that there was differential physiological responding to the vignettes such that, as predicted, participants' hearts rates showed a pattern of deceleration followed by acceleration, similar to a threat response. There was support for elevated anxiety as a significant predictor of responses, but only among those participants with higher levels of HABs such that HRs remained elevated with very little deceleration across time. These results suggest a pattern of physiological hyperarousal and blunted reactivity for those with high anxiety and HABs indicating that that youths' interpretation of a situation may interact with subjective levels of anxiety to predict heart rate responses. (PsycINFO Database Record

Relative Bradycardia in Scrub Typhus.

To investigate the relationship between heart rate and temperature, we examined 493 febrile patients with documented disease. These patients were diagnosed serologically and analyzed retrospectively: 337 (68.4%) responded to fever with increased heart rate < 10 beats/minute/°C (relative bradycardia [RB]), and 156 patients had a heart rate response ≥ 10 beats/minute/°C (general heart rate increase [GHRI]). The RB group had a higher median resting heart rate and lower heart rate at maximum temperature than the GHRI group. Despite differences in heart rate response, no significant differences were seen in clinical outcomes (acute kidney injury, systemic inflammatory response syndrome (SIRS), and death). We concluded that most patients with scrub typhus presented with RB. In scrub typhus infection, RB can be included as one of the clinical features for differential diagnosis from other infectious diseases.

Locomotor and Heart Rate Responses of Floaters During Small-Sided Games in Elite Soccer Players: Effect of Pitch Size and Inclusion of Goalkeepers.

To (1)compare the locomotor and heart rate responses between floaters and regular players during both small and large small-sided games (SSGs) and (2)examine whether the type of game (ie, game simulation [GS] vs possession game [PO]) affects the magnitude of the difference between floaters and regular players. Data were collected in 41 players belonging to an elite French football team during 3 consecutive seasons (2014-2017). A 5-Hz global positionning system was used to collect all training data, with the Athletic Data Innovation analyzer (v5.4.1.514) used to derive total distance (m), high-speed distance (>14.4km·h-1, m), and external mechanical load (MechL, a.u.). All SSGs included exclusively 1 floater and were divided into 2 main categories, according to the participation of goalkeepers (GS) or not (PO) and then further divided into small and large (>100m2per player) SSGs based on the area per player ratio. Locomotor activity and MechL performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, whereas differences in heart rate responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO. Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher heart rate responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.

Abstract 115: Primary Hyperadrenergic Postural Tachycardia Syndrome. Evidence From Sympathetic Nerve Recordings

Postural tachycardia syndrome (POTS) is a chronic disabling condition with excessive upright tachycardia and symptoms due to enhanced sympathetic activity in otherwise healthy young individuals. Because it is not clear if sympathetic activation is a primary phenomenon, or an appropriate compensatory response to hypovolemia, deconditioning or partial neuropathy, we analyzed resting supine muscle sympathetic nerve activity (MSNA) in 38 female POTS patients (mean±SD, age 32.1±9.1, BMI 22.7±5.4). MSNA showed a wide range of burst rate (19.7±12.1 bursts/min, range 1.2 to 54, 95% CI: 15.7 to 23.6). We compared the 1 st and 4 th Quartiles of 28 MSNA records (MSNA_Q1: &lt; 7.3; MSNA_Q4: &gt; 23.4 bursts/min) to determine if resting MSNA is related to heart rate (HR) or blood pressure (BP) responses to orthostatic challenge and the Valsalva maneuver (2-way ANOVA with post-hoc tests). Upright HR was inappropriately high in both groups (MSNA_Q1: 120±19 vs. MSNA_Q4: 110±20 bpm, NS), but the MSNA_Q4 group had higher upright diastolic BP than MSNA_Q1 (81±12 vs. 62±8 mmHg, P&lt;0.01). Similarly, there were no differences in HR response to the Valsalva maneuver between groups, but systolic and diastolic BP were higher during late phase 2 in MSNA_Q4 (p&lt;0.05), and this was preceded by higher MSNA spike rate (44.3±16.3 vs. 81.2 ±25 maximal spikes/secs per beat, p&lt;0.01) during early phase 2 of Valsalva maneuver. The greater BP responses, but comparable HR responses, to posture and Valsalva challenges provide evidence that the subset of POTS patients with higher resting MSNA have a primary sympathetic activation. These patients might benefit from sympatholytic therapy in contrast to other POTS patients with low or absent resting MSNA.