P4423Extreme bradycardia in athletes is due to intrinsic changes within the heart

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
M D Flannery ◽  
F Sully ◽  
K Janssens ◽  
G Morris ◽  
J Kalman ◽  
...  
Keyword(s):  
Heart Rate ◽  
Vagal Tone ◽  
Endurance Athletes ◽  
Valsalva Manoeuvre ◽  
Resting Heart Rate ◽  
Maximum Heart Rate ◽  
Vo2 Max ◽  
Heart Rates ◽  
Intrinsic Heart Rate ◽  
Autonomic Blockade

Abstract Background It is well known that athletes and in particular endurance athletes have lower resting heart rates than non-athletes. This has generally been considered a healthy adaptation. Traditionally this was thought be due to increased vagal tone. Several studies have shown that endurance athletes continue to have lower heart rates in the absence of autonomic influence suggesting bradycardia is due to intrinsic changes within the heart. A subset of endurance athletes have very low heart rates with Tour de France cyclists having described heart rates in the 30s. It is unclear whether in these elite athletes with very low heart rates the profound bradycardia is due to autonomic influence or intrinsic changes within the heart. Aim The aim of this study was to determine if extreme bradycardia in athletes is due to excess vagal tone or more profound intrinsic changes within the heart. Methods We recruited three cohorts for this study: non-athlete controls (NA), endurance athletes with a documented resting heart rate >40 (EA) and endurance athletes with a resting heart rate <40 (BA). All participants underwent baseline testing including ECG, echocardiography and VO2 max testing. All participants came back on a second occasion for treatment with dual autonomic blockade (DAB) to determine intrinsic heart rate in the following manner. After resting supine for five minutes resting heart rate was measured. Participants were then administered 0.04mg/kg of intravenous atropine. After five minutes participants were then administered 0.05mg/kg of intravenous metoprolol. This was repeated every five minutes until there was no further drop in heart rate or 0.2mg/kg had been administered. The resting heart rate at this stage was recorded as the intrinsic heart rate. Parasympathetic blockade was confirmed by lack of response to Valsalva manoeuvre and sympathetic blockade was confirmed by lack of response to metoprolol. VO2 max testing was then performed to determine maximum heart rate. Results 9 NA (7 male), 10 EA (8 male) and 5 BA (4 male) participated in this study. The average age was similar in all groups (NA 32.9y, EA 32.4y, BA 31.4y). The average resting heart rate was 71.7 in the NA group, 48.3 in the EA group and 41.6 in the BA group (p<0.05 for comparisons between all three groups). Following dual autonomic blockade resting heart rate was 86.0 in the NA group, 76.9 in the EA group and 64.4 in the BA group (p<0.05 for comparisons between all three groups). Maximum heart rate under DAB was 140.1 in the NA group, 138.0 in the EA group and 140.4 in the BA group. These differences were not significant. Conclusion In athletes with very low heart rates, bradycardia is due to more profound intrinsic changes within the heart. Acknowledgement/Funding NHMRC Project Grant

Stability of Heart Rate at Physiological Thresholds Between Temperate and Heat Stress Environments in Endurance-Trained Males

2020 ◽  
pp. 1-4
Author(s):  
Ed Maunder ◽  
Daniel J. Plews ◽  
Fabrice Merien ◽  
Andrew E. Kilding
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Relative Humidity ◽  
Blood Lactate ◽  
Endurance Athletes ◽  
Heart Rates ◽  
Stress Environments ◽  
Positive Correlations ◽  
Hot Environments ◽  
Stress Training

Many endurance athletes perform specific blocks of training in hot environments in “heat stress training camps.” It is not known if physiological threshold heart rates measured in temperate conditions are reflective of those under moderate environmental heat stress. A total of 16 endurance-trained cyclists and triathletes performed incremental exercise assessments in 18°C and 35°C (both 60% relative humidity) to determine heart rates at absolute blood lactate and ventilatory thresholds. Heart rate at fixed blood lactate concentrations of 2, 3, and 4 mmol·L−1 and ventilatory thresholds were not significantly different between environments (P > .05), despite significant heat stress-induced reductions in power output of approximately 10% to 17% (P < .05, effect size = 0.65–1.15). The coefficient of variation for heart rate at these blood lactate concentrations (1.4%−2.9%) and ventilatory thresholds (2.3%−2.7%) between conditions was low, with significant strong positive correlations between measurements in the 2 environments (r = .92–.95, P < .05). These data indicate heart rates measured at physiological thresholds in temperate environments are reflective of measurements taken under moderate environmental heat stress. Therefore, endurance athletes embarking on heat stress training camps can use heart rate–based thresholds ascertained in temperate environments to prescribe training under moderate environmental heat stress.

Psychophysiological Comparison of Self-Efficacy and Resting Heart Rate

2002 ◽  
Vol 94 (3) ◽  
pp. 720-722
Author(s):  
Matthew S. Wiggins
Keyword(s):  
Heart Rate ◽  
Analysis Of Variance ◽  
Self Efficacy ◽  
Exercise Program ◽  
Resting Heart Rate ◽  
Heart Rates ◽  
Fitness Center ◽  
Significant Difference ◽  
Main Effect ◽  
Individual Self

This study was used to assess the premise that lower resting heart rates should be associated with higher scores on self-efficacy for exercisers. A total of 64 participants, 29 men and 35 women ranging in age from 18 to 38 years old ( M = 23.22, SD = 4.19), currently participating in an exercise program at a fitness center, were assessed using the Exercise Specific Self-efficacy Scale to measure general individual self-efficacy, along with obtaining resting heart rates. Participants were separated into three different groups based on individual resting heart-rate values. Results for a 2 (sex) by 3 (heart rate) two-way analysis of variance indicated a significant difference in self-efficacy scores ( F2.58 = 3.24, p<.05) among the three groups. No interaction or main effect for sex was found.

Heat Stress Training Camps for Endurance Sport: A Descriptive Case Study of Successful Monitoring in 2 Ironman Triathletes

2020 ◽  
Vol 15 (1) ◽  
pp. 146-150
Author(s):  
Ed Maunder ◽  
Andrew E. Kilding ◽  
Christopher J. Stevens ◽  
Daniel J. Plews
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Heat Stress ◽  
Well Being ◽  
Self Report ◽  
Endurance Athletes ◽  
Resting Heart Rate ◽  
Resting Heart Rate Variability ◽  
Stress Training

A common practice among endurance athletes is to purposefully train in hot environments during a “heat stress camp.” However, combined exercise-heat stress poses threats to athlete well-being, and therefore, heat stress training has the potential to induce maladaptation. This case study describes the monitoring strategies used in a successful 3-week heat stress camp undertaken by 2 elite Ironman triathletes, namely resting heart rate variability, self-report well-being, and careful prescription of training based on previously collected physiological data. Despite the added heat stress, training volume very likely increased in both athletes, and training load very likely increased in one of the athletes, while resting heart rate variability and self-report well-being were maintained. There was also some evidence of favorable metabolic changes during routine laboratory testing following the camp. The authors therefore recommend that practitioners working with endurance athletes embarking on a heat stress training camp consider using the simple strategies employed in the present case study to reduce the risk of maladaptation and nonfunctional overreaching.

The effect of the presence of heart-rate monitors on the behaviour of group housed sows

1996 ◽  
Vol 1996 ◽  
pp. 193-193
Author(s):  
P.J. Baynes ◽  
K. Graham ◽  
E.J. Hunter ◽  
H.J. Guise ◽  
R.H.C. Penny
Keyword(s):  
Heart Rate ◽  
Resting Heart Rate ◽  
Heart Rate Monitor ◽  
Heart Rate Monitors ◽  
Heart Rates ◽  
Group Behaviour

Heart rate has been successfully recorded in sheep, deer and pigs (Baldock and Sibly, (1986) Price, Sibly and Davies, (1993) Webster et al, 1995). This work has shown that resting heart rate can increase in stressful situations. Being able to record heart rates of group-housed sows would complement behavioural observations, if it could be shown that the presence of the monitor did not alter group behaviour. The aim of this study was to assess in a group of active sows, the effect of the presence of a heart rate monitor on behaviour.

Intrinsic heart rate in the dog determined by pharmacologic denervation

1983 ◽  
Vol 245 (4) ◽  
pp. H592-H597 ◽  
Author(s):  
J. R. Brunsting ◽  
H. A. Schuil ◽  
W. G. Zijlstra
Keyword(s):  
Heart Rate ◽  
Blood Gases ◽  
Conscious Dogs ◽  
Interindividual Variation ◽  
Adrenergic Blockade ◽  
Intrinsic Heart Rate ◽  
Parasympathetic System ◽  
Autonomic Blockade ◽  
Cervical Vagotomy ◽  
The Difference

Intrinsic heart rate was measured in 19 dogs in 76 experiments after autonomic blockade, using various forms of anesthesia. Measurements were made in conscious dogs (n = 16) and in dogs in neuroleptanesthesia (n = 54) or under pentobarbital sodium (n = 6). Temperature, arterial pH, and blood gases were kept within narrow limits. Adrenergic blockade was achieved by phenoxybenzamine (2 mg X kg-1) and propranolol (2 mg X kg-1, followed by 2 mg X kg-1 X h-1). The parasympathetic system was blocked either by atropine (0.5 mg X kg-1, followed by 0.5 mg X kg-1 X h-1) and hexamethonium (20 mg X kg-1, followed by 10 mg X kg-1 X h-1) or by atropine and bilateral cervical vagotomy. Administration of hexamethonium or vagotomy was needed to block the vagal cardioacceleration unmasked by the administration of muscarinic blocking agents in conscious dogs and in dogs in neuroleptanesthesia. The mean denervated heart rate was 142.8 beats/min. This value is higher than that reported for surgically denervated hearts, the difference very likely reflecting the activity of the intact parasympathetic intrinsic cardiac innervation in surgical preparations. The estimated intraindividual and interindividual SD were 9.7 and 19.4 beats/min, respectively. The highly significant interindividual variation (P less than 0.01) contradicts the concept of an intrinsic heart rate as a practically constant species-dependent quantity.

The Effect of Swimming Activity and Section of the Vagus Nerves on Heart Rate in Rainbow Trout

1974 ◽  
Vol 60 (2) ◽  
pp. 305-319 ◽  
Author(s):  
IMANTS G. PRIEDE
Keyword(s):  
Heart Rate ◽  
Maximum Rate ◽  
Critical Speed ◽  
Swimming Activity ◽  
Vagus Nerves ◽  
Maximum Heart Rate ◽  
Heart Rates ◽  
Cardiac Responses ◽  
Different Temperatures ◽  
Speed Up

1. Heart rates associated with swimming activity were measured in intact and vagotomized fish at 6.5 and 15 °C. 2. Low swimming speeds had no effect on heart rate but above a threshold speed it increased logarithmically with swimming speed up to the critical speed and maximum heart rate. 3. Times for recovery after exercise increased rapidly above the critical speed. 4. Bilaterally vagotomized fish at 6.5 °C showed high resting heart rates and erratic cardiac responses to exercise. 5. In bilaterally vagotomized fish at 15 °C heart rates were normal except for a low maximum rate. 6. It is concluded that the vagus nerve can function differently at different temperatures.

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