Magnitude Of Changes In Heart Rate Research Articles

Performance of Fitbit Charge 3 against polysomnography in measuring sleep in adolescent boys and girls

ABSTRACT We evaluated the performance of Fitbit Charge 3™ (FC3), a multi-sensor commercial sleep-tracker, for measuring sleep in adolescents against gold-standard laboratory polysomnography (PSG). Single-night PSG and FC3 sleep outcomes were compared in thirty-nine adolescents (22 girls; 16–19 years), 12 of whom presented with clinical/subclinical DSM-5 insomnia symptoms (7 girls). Discrepancy analysis, Bland–Altman plots, and epoch-by-epoch analyses were used to evaluate FC3 performance. The influence of several factors potentially affecting FC3 performance (e.g., sex, age, body mass index, firmware version, and magnitude of heart rate changes between consecutive PSG epochs) was also tested. In the sample of healthy adolescents, FC3 systematically underestimated PSG total sleep time by about 11 min and sleep efficiency by 2.5%, and overestimated wake after sleep onset by 9 min. Proportional biases were detected for “light” and “deep” sleep duration, resulting in significant underestimation of these parameters for those participants having longer PSG N1+ N2 and N3 durations, respectively. No significant systematic bias was detected for sleep efficiency and sleep onset latency. Epoch-by-epoch analysis showed sleep-stage sensitivity (average proportion of PSG epochs correctly classified by the device for a given sleep stage) of 68% for wake, 78% for “light” sleep, 59% for “deep” sleep, and 69% for rapid eye movement (REM) sleep in healthy sleepers. Similar results were found in the sample of adolescents with insomnia symptoms. Body mass index was positively associated with FC3-PSG discrepancies in wake after sleep onset (R2 = .16, p = .048). The magnitude of the heart rate acceleration/deceleration between consecutive PSG epochs was an important factor affecting FC3 classifications of sleep stages. Our results are in line with a general trend in the literature, suggesting better performance for the recently introduced multi-sensor devices compared to motion-only devices, although further developments are needed to improve accuracy in sleep stage classification and wake detection. Further insight is needed to determine factors potentially affecting device performance, such as accuracy and reliability (consistency of performance over time), in different samples and conditions.

“WHY WARM UP?”: EXERCISE ONSET AND THE EARLY PEAK IN PULMONARY ARTERY WEDGE PRESSURE IN HEALTHY OLDER ADULTS

Knowledge gaps exist regarding the pulmonary artery (PA) and pulmonary artery wedge pressure (PAWP) responses to exercise in healthy older adults that may contribute to exertional intolerance. A relatively precipitous rise in pressures occur early after exercise onset in older adults and is time-variant: an early peak in PAWP is followed by a decline as exercise becomes sustained. Our objective was to analyze the PAWP response to early exercise and its relationship to demographic, echocardiographic and hemodynamic characteristics. A retrospective analysis was performed using data from 36 healthy sedentary volunteers (18 men and 18 women, no medications, cardiac disease or cardiac risk factors) with a mean age of 56±7 years, who participated in an exercise study undergoing right heart catheterization. Subjects were studied at rest and during two stages of semi-upright cycle ergomety. Work rate was adjusted during the first stage of Light Exercise to achieve a target heart rate (HR) of 100bpm (Early Light, 2min), and then further adjusted to maintain this HR (Sustained Light, five min). Work rate in the second stage was similarly adjusted to achieve a target HR of 120bpm (Early Moderate, two min) and to sustain it (Sustained Moderate, five min). PAWP was measured at each stage. The early peak and sustained PAWP and PA pressure responses during exercise are shown in Table 1. We confirmed that the rise in PAWP occurs early but then declines with sustained light exercise. Neither the early PAWP peak nor the magnitude of change were correlated to any demographic or baseline echocardiographic variables. The early peak PAWP was significantly negatively correlated with resting HR as well as the magnitude of change in HR from rest to early exercise (R2 0.165, p<0.05, Figure). The magnitude of change in the peak PAWP from rest to early light exercise was positively related to the decay in PAWP with sustained exercise (R2 0.391, p<0.05, Figure). The PAWP response to exercise has a negative relationship to resting HR, which may reflect the adjustment to a particular work rate to achieve a HR of 100bpm in early light exercise. We speculate that the PAWP peak with early light exercise observed in this study may be explained by a rapid increase in left ventricular filling pressure as HR increases abruptly with the initiation of exercise. The latent decay in PAWP suggests delayed diastolic accommodation.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Effect of Bout Duration on Exercise Intensity and Technical Performance of Small-Sided Games in Soccer

To examine whether the increase in bout duration would affect the exercise intensity and technical actions, we manipulated bout duration during a typical small-sided game drill (SSG) in male soccer players. Nineteen players (mean ± SD: age 24 ± 4 years, body mass 74 ± 4 kg, and height 180 ± 5 cm) completed three bouts of a 3-a-side drill at three different bout durations: 2, 4, and 6 minutes. Exercise intensity was quantified using heart rate (HR) and rating of perceived exertion (RPE). A nonsignificant duration × bout interaction was found for HR (p = 0.757). Heart rates of bout 1 were significantly lower than bout 2 (p = 0.004) and bout 3 (p = 0.049). The effect of duration was close to significance for HR (p = 0.057) with 6-minute SSG significantly lower than 4-minute SSG (p = 0.004). Duration × bout interaction did not reach the significance for RPE (p = 0.096). The RPE significantly increased along the bouts (p < 0.001) but was not affected by duration (p = 0.763). No effect of duration was found for number of technical actions per minute (p > 0.111). A significant effect of bout was only found for successful passes (p = 0.018). Partially confirming our hypothesis, the increase in bout duration from 2 to 6 minutes resulted in a decrease in intensity only between the 4- and 6-min SSG. However, duration did not influence the technical actions and proficiency. The magnitude of changes in HR (89.5 vs. 87.8 of maximum) is probably not enough to induce different training adaptations. Therefore, coaches can use different bout durations with minimal impact on exercise intensity and without compromising technical proficiency.

Heart Rate Responses at Onset of Contraction

We tested the hypothesis that the initial heart rate (HR) response at the onset of maximal handgrip contraction is altered after training. 17 volunteers (nine trained and eight controls) performed ten intermittent static handgrip contractions with maximal effort, alternating between 15-s contractions and 15-s pauses. High-intensity static handgrip training was performed using the nondominant arm alone for 4 weeks. Handgrip force (HGF) and HR were analyzed for the initial 7 s of every static handgrip exercise. Peak HR (pre-training: 94.5 +/- 12.8 beats/min; post-training: 89.7 +/- 10.2 beats/min, p < 0.05) decreased. However, the magnitude of HR change at the onset of contraction remained constant (pre-training: 23.0 +/- 7.7 beats/min; post-training: 25.7 +/- 6.5 beats/min, p = 0.0767), while the HR responses in the subsequent bouts increased after training (p < 0.001). The resting HR decreased (pre-training: 71.5 +/- 9.3 beats/min; post-training 64.1 +/- 5.7 beats/min, p < 0.05). Maximal HGF increased by 11.1 % in trained arms and by 8.7 % in untrained arms, although an increase in maximal forearm girth was only observed in the trained arm (2.0 %, p < 0.0001). Although high-intensity training modulated the abrupt HR responses, the magnitude of the response remained unchanged at the onset of maximal forearm contraction and the resting HR significantly decreased.

The Influence of Vagal Withdrawal on Heart Rate During Head-Up Tilt in Persons with SCI

Persons with spinal cord injury (SCI) are subjected to few gravitational stressors during daily routines and have diminished autonomic cardiovascular control. PURPOSE: To identify cardiovascular autonomic responses to passive head-up tilt (HUT) in persons with central (tetraplegia) and peripheral (paraplegia) autonomic dysfunction compared with a non-SCI control group. METHODS: Subjects included 15 persons with chronic SCI, 7 with tetraplegia (T) and 8 with paraplegia (P), and 8 age- height- and weight-matched controls (non-SCI). Heart rate (HR) was continuously monitored and cardiovascular autonomic responses were assessed during two 5-minute periods at supine rest and at 45° HUT. Change from supine to 45° HUT was calculated for HR, high & low frequency HR variability (HF & LF) and the LF/HF ratio. Data are reported as mean±SD and statistical significance was set at p<0.05. RESULTS: Supine HR was comparable among the groups; however LF was reduced in the T compared with the non-SCI group. Controlling for supine HR, the magnitude of change in HR was reduced in the T compared to the P and non-SCI groups. There was a significant interaction effect among the groups for the relationship between the change in HR and change in HF; and the slope of this relationship was reduced in the T (−1.026: 95% CI: 0.78–2.41) compared with the P (−7.808: 95% CI: 2.27–7.01) and non-SCI (−6.985: 95% CI: 2.09–6.44) groups. The relationship between HR and LF/HF was similar between the T (0.312: 95% CI: 0.27–0.832) and the non-SCI (0.353: 95% CI: 0.345–1.06) but both were reduced compared to the P group (4.893: 95% CI: 1.397–4.31). CONCLUSION: Although the magnitude of vagal withdrawal was comparable among the three groups, the increase in heart rate was attenuated in the group with tetraplegia. This finding may reflect the independent influence of vagal withdrawal on heart rate in the absence of a catecholamine response to upright posture in those with tetraplegia.

Role of C fibers in physiological responses to ozone in rats.

The purpose of this study was to evaluate the role of C fibers in airway responsiveness after exposure to ozone (O3) in rats. The role of C fibers in the decreases in heart rate (HR) and core body temperature (Tc) that occur after inhalation of O3 was also examined. Neonatal rats were treated with capsaicin (Cap) or the vehicle used to dissolve capsaicin (Veh). Cap has been shown to cause permanent destruction of C fibers. When they reached adulthood, conscious minimally restrained rats were exposed to 2 ppm O3 or to air for 3 h. Two hours after the cessation of exposure, rats were anesthetized and instrumented for the measurement of pulmonary mechanics and airway responsiveness to inhaled aerosolized methacholine. O3 had no effect on baseline pulmonary conductance (GL) in either Veh or Cap rats but did cause a decrease in dynamic compliance (Cdyn) in Cap rats (P < 0.05). In Cap rats, O3 exposure caused a marked increase in airway responsiveness; the doses of inhaled aerosolized methacholine required to decrease GL and Cdyn by 50% were 6.5-fold and 9.8-fold lower in O3-compared with air-exposed rats (P < 0.005). In contrast, in Veh rats, O3 did not alter responsiveness. During O3 exposure, there was a profound, almost 50%, decrease in HR as measured with implanted electrodes. A decrease in Tc (measured with a rectal probe) of approximately 2.5 degrees C also occurred during O3 exposure. There was no significant effect of Cap pretreatment on the magnitude of these O3-induced changes in HR and Tc. Our results are consistent with the hypothesis that C fibers act to inhibit the development of hyperresponsiveness elicited by O3 inhalation but do not contribute to O3-induced changes in HR or Tc.

Neonatal responsivity to gustatory stimulation: The gustatory-vagal hypothesis

Sucking frequency, heart rate, and cardiac vagal tone (V) were monitored in neonates during manipulations of sweet gustatory stimulation. In response to increased sweetness, reductions in cardiac vagal tone and increases in heart rate paralleled increased sucking frequency. Individual differences in cardiac vagal tone were correlated with the magnitude of heart rate changes to gustatory stimulation.

Conditioned avoidance reflex and intersignal movements: interrelationship of cardiac and motor components.

The correlation of the heart rate (HR), of a conditioned motoric reaction, and intersignal movements was studied during the development of a conditioned reflex (CR) of avoidance using V.P. Petropavlovskii's methods. The level of defensive motivation, assessed on the basis of the magnitude of changes in HR was maximal against the background of a firmly developed CR during the course of the latent period of the conditioned motoric reaction. A sharp decrease in the level of defensive excitation took place against the background of the latter, expressed in the prolonged holding of the extremity in place in the safety zone (height of rise 5-10 cm, guaranteeing the avoidance of electrodermal stimulation of the extremity). Intersignal movements of two types were described: the first in the form of phasic flexions; the second repeats the conditioned motoric reaction of the holding of the extremity in place. A reduction in defensive excitation took place against the background of the latter, like that which took place during the elevation of the extremity against the background of the combination.

Mechanism for slowing of heart rate and associated changes in pulmonary circulation elicited by cold injectate during thermodilution cardiac output determination in dogs.

The authors investigated the mechanism for slowing of heart rate (HR) and associated changes in the pulmonary hemodynamics caused by cold injectate during thermodilution method. To clarify whether the slowing of HR after cold injectate is due to the cooling of the sinoatrial (SA) node or a reflex mediated by the autonomic nerves, we directly measured the myocardial temperature of the SA node region by a thermistor probe, and evaluated the HR responses to iced injectate after autonomic blockade in anesthetized dogs. Additionally, pulmonary blood flow (PBF) was continuously measured by an electromagnetic flowmeter during the delivery of injectate. The direction and magnitude of changes in HR after injectate were significantly dependent upon the injectate temperature (P less than 0.01). Thereby, the changes in HR correlated well with those in myocardial temperature of the SA node region (r = 0.987, P less than 0.01). However, the HR responses to injectate were unaffected by cervical vagotomy or stellate ganglionectomy. A significant decrease in PBF was noted in most cases during the slowing of HR. It was concluded that the slowing of HR after cold injectate during thermodilution in dogs is primarily due to the direct cooling of the SA node.

Cognitive stress and cardiovascular reactivity. II. Relationship to atherosclerosis, arrhythmias, and cognitive control

This is the second of a two-part series on the effects of cognitive stress on cardiovascular disease. This paper reviews the relationship between cognitive stress and cardiovascular reactivity as it relates to the development of atherosclerosis and arrhythmias. In addition, the moderation of cardiovascular reactivity by the opportunity to exercise control over the stressor is discussed. The findings may be summarized as follows. First, recent animal work has suggested that the magnitude of heart rate change in the presence of a conditioned aversive stimulus is positively correlated with the extent of coronary atherosclerosis under diets high and low in atherogenic potential. Second, cardiovascular reactivity in humans may be related to several factors that could have an influence on the pathogensis of atherosclerosis. These factors include: increased beta-adrenergic driving, increased shearing force on the intimal lining of the vessels, changes in pulsatile flow and the subsequent smooth muscle reparatory process. Cognitive (psychological) stress has also been related to ST segment depression, rate-pressure product changes, and changes in cardiac contractility. Animal studies have shown that the susceptibility to ventricular fibrillation may be enhanced by the presence of a conditioned aversive stimulus and may be reduced through adaptation to the aversive environment. The balance between sympathetic and parasympathetic influences on the myocardium may also play a critical role in the susceptibility of an already diseased heart to succumb to fatal arrhythmias during a behavioral stressor. Finally, studies in which subjects may exercise some control over an aversive stimulus suggest that cardiovascular reactivity may be pronounced and sustained in situations requiring frequent adjustment to changes in the criteria for successful performance, and/or the presence of positive incentives.

Win some, lose some: Parental hypertension and heart rate change in an incentive versus response cost paradigm

Fowles (1983), citing evidence from separate studies, suggests that both incentive and response cost paradigms increase heart rate and should be subsumed under Gray's (1975) ‘appetitive motivational system’. Shock avoidance and loss of reward (response cost) contingencies, while aversive, appear to evoke this motivational system; consequently both should elicit heart rate increases independent of anxiety. The present investigation compared magnitude of heart rate changes observed under conditions of winning and losing money. Results showed: (1) no differences between incentive and response cost conditions; (2) no effect of state anxiety on heart rate in these conditions, despite an elevation of state anxiety on the task day relative to a subsequent relaxation day assessment; and (3) some evidence for the presence under both such appetitive conditions of cardiovascular hyperresponsivity among offspring of hypertensive parents. The results suggest a need for systematic parametric studies of experimental conditions.