Disability type influences heart rate response during power wheelchair sport

PURPOSE: The purpose of this study was to determine the influence of disability type on exercise response during power wheelchair competition. The secondary purpose was to determine the extent to which heart rate responses during competition meet cardiorespiratory fitness training intensities for the general population. METHODS: Forty-eight athletes who had cerebral palsy (CP, N = 31), spinal cord injury (SCI, N = 10), or muscular dystrophy (MD, N = 7), and were competing in the 2003 Power Soccer National Tournament, volunteered to participate. Heart rate was recorded every 5 s throughout pre-game and game conditions by Polar S610 monitors. Average heart rate (HR) values were determined for GAME and RESPONSE (change score between GAME HR and pre-game HR). The Kruskal-Wallis nonparametric test was used to determine whether a significant difference among group medians existed on the dependent measure, RESPONSE (P < 0.05). RESULTS: A significant difference on RESPONSE (P < 0.05) existed among athletes with CP (29 bpm), SCI (17 bpm), and MD (26 bpm). The median RESPONSE for athletes with CP was 12 bpm higher than athletes with SCI, and this difference was significant (P < 0.01). Further, 22 athletes with CP (71%), 5 athletes with MD (71%), and 1 athlete with SCI (10%) exceeded 55% of estimated HR(max) for at least 30 min during competition. CONCLUSION: Disability type influences the heart rate response to power wheelchair sport, and may affect the ability to sustain training intensities associated with fitness improvement.     

Effects of age on heart rate response during a strenuous match of tennis

Ten young women tennis players (YP: 15-30 years) and 10 veteran women tennis players (VP: 40-51 years) of equivalent skill took part in this study. In the laboratory, maximal heart rate (maxHR), VO2max and blood lactate concentration (LA) at exhaustion were measured. On the field, each match was carried out as an official competition. However, in order to obtain a strenuous match, some experimental conditions were imposed (duration, hydration, skill of opponent, etc.). Heart rate (HR) was recorded throughout the match and LA was measured at rest before the match and immediately at the end of the match. While mean heart rate intensity remained relatively steady in YP it tended to increase as the game went on in VP. Due to the lower maxHR and VO2max, VP play at a higher percentage of maxHR and thus probably at a greater relative exercise intensity than YP. For the last part of the match, in some VP, who stopped playing due to exhaustion, HR intensity reached a considerable high level. No significant increase in LA was found at the end of the match in either group. If individual values were considered, no large increase in LA was found in the exhausted women. Obviously fatigue did not result from a muscle lactate accumulation. On the other hand, this moderate LA suggests that the oxygen transport was not a limiting factor of activity, although maxHR, thus probably a maximum cardiac output, was reached. Among the possible factors responsible for the exhaustion a decrease in kinetics of heart rate recovery may be considered in veteran tennis players.     

Pre-exercise food and heart rate during submaximal exercise.

The heart rates of 20 movement studies students were measured during multi-stage cycle ergometer tests. The tests were repeated on five occasions following the ingestion of different pre-exercise meals and the results compared. A glucose solution taken three hours prior to the exercise (G3) resulted in the lowest heart rates at each work rate. The highest heart rates at each work rate were recorded following the ingestion of glucose or protein one hour before the exercise (G1 and P1 respectively). The heart rate values during G3 were on average 10.3 beat.min-1 lower than those used during G1 and P1. Intermediate heart rates were obtained with protein taken three hours prior to the exercise or a complete fast for 12 to 14 hours. The results have implications for those attempting to predict maximum oxygen uptake from submaximal heart rates.     

Analysis of heart rate and heart rate variation during cardiac CT examinations

RATIONALE AND OBJECTIVES: We sought to examine heart rate and heart rate variability during cardiac computed tomography (CT). MATERIALS AND METHODS: Ninety patients (59.0 +/- 13.5 years) underwent coronary CT angiography (CTA), with 52 patients also undergoing coronary artery calcium scanning (CAC). Forty-two patients with heart rate greater than 70 bpm were pretreated with oral beta-blockers (in five patients, use of beta-blocker was not known). Sixty-four patients were given sublingual nitroglycerin. Mean heart rate and percentage of beats outside a +/-5 bpm region about the mean were compared between baseline (free breathing), prescan hyperventilation, and scan acquisition (breath-hold). RESULTS: Mean scan acquisition time was 13.1 +/- 1.5 seconds for CAC scanning and 14.2 +/- 2.9 seconds for coronary CTA. Mean heart rate during scan acquisition was significantly lower than at baseline (CAC 58.2 +/- 8.5 bpm; CTA 59.2 +/- 8.8 bpm; baseline 62.8 +/- 8.9 bpm; P < .001). The percentage of beats outside a +/-5 bpm about the mean were not different between baseline and CTA scanning (3.5% versus 3.3%, P = .87). The injection of contrast had no significant effect on heart rate (58.2 bpm versus 59.2 bpm, P = .24) or percentage of beats outside a +/-5 bpm about the mean (3.0% versus 3.3%, P = .64). No significant difference was found between gender and age groups (P > .05). CONCLUSIONS: Breath-holding during cardiac CT scan acquisition significantly lowers the mean heart rate by approximately 4 bpm, but heart rate variability is the same or less compared with normal breathing.     

Reduced heart rate response to exercise in ischemic heart disease: the fallacy of the target heart rate in exercise testing

When exercise testing 159 patients with prior myocardial infarction, we identified 39 who were limited by fatigue. This group was all in sinus rhythm; none were taking drugs likely to impair the chronotropic response of the heart; none experienced chest pain or developed ischemic ECG changes. In 18 of this group, maximal heart rate achieved with exercise was 2SD or more below the age predicted value, and their heart rate response to exercise was reduced compared to that of the other 21 whose maximal exercise heart rates were within 2SD of age predicted values. A subgroup of 8 subjects with reduced exercise heart rates was studied before and after vagal blockade. In the 4 subjects whose infarction was inferior, the reduction in heart rate response was more profound and persisted after vagal blockade, suggesting either reduced pacemaker responsivness, due to ischemia or infarction, or autonomic imbalance as possible mechanisms. All 8 showed alinear increases in ventilation at higher power outputs and mean blood lactate postexercise was 7.5 mM/I without vagal blockade. Our findings suggest that a reduced heart rate response to exercise, already shown to imply added coronary risk, may be subdivided aetiologically and possibly prognostically. The use of a "Target Heart Rate" in such patients offers no safety margin, and maximal exercise capacity will be grossly over-estimated if extrapolated from the submaximal heart rate response. A cardiovascular limitation to exercise may be detected by an alinear increase in ventilation.     

Validation of simple tests of biathlon shooting ability.

The aim of this study was to validate three simple tests of biathlon shooting abilities. Twelve expert biathletes performed visual reaction time tests adapted for the rifle in the standing (RT-S) and prone positions (RT-P), and a tremometer test adapted for the rifle in the standing position (TT-S). Six consecutive days' measurements showed an acceptable reproducibility for these tests (coefficient of variation = 1.2% for RT-S, 1.1% for RT-P and 6.5% for TT-S). A significant difference was observed between TT-S at rest and after roller skiing 2.1 km at 90 % of maximal heart rate. This finding demonstrates the sensitivity of TT-S to discriminate the effects of fatigue on postural control. Among 24 biathletes of regional to expert level, significant correlations were observed between resting RT-P and prone shooting performance after roller skiing (r2 = 0.23; p = 0.01) and between resting TT-S and shooting performance in the standing position after roller skiing (r2 = 0.68; p = 0.0001), demonstrating the specificity of these tests. From these results, we conclude that TT-S is a valid field test of biathlon shooting performance.     

Factors affecting the relation between heart rate and energy expenditure during exercise.

This study evaluated the ability to use the relationship between heart rate (HR) and oxygen uptake (VO2) to estimate energy expenditure during physical activity (AEE). General prediction equations were established based on the individual relations between HR and AEE. Forty-two women, (mean age 38.1 [SD 9.8] years, BMI 23.9 [SD 4.4]), and 45 men (40.3 [SD 9.2] years, BMI 24.7 [SD 2.9]), carried out two incremental tests, one with a cycle ergometer and another on a treadmill. Subjects also performed a 10 minute steady-state exercise, cycling and walking. Respiratory gases were obtained from indirect calorimetry. AEE was calculated from VO2 and carbon dioxide production (VCO2). The predicted AEE was compared with the AEE measured during the steady-state exercise. Using the generalised linear model, two alternative models were found to predict AEE and HR. The first showed a three-way interaction between HR, body weight and gender (p = 0.022) and also between HR age and gender (p=0.083). The second produced a three-way interaction between HR, body weight and gender (p=0.057). For cycling and walking, respectively, the predicted AEE overestimated the actual AEE by 17.7 (SD 23.2)% and 6.2 (SD 19.3)% in the first model and by 17.9 (SD 22.7)% and 6.6 (SD 19.8)% in the second during the steady-state exercise. It was concluded that at least gender and body weight should be included when HR is used to predict AEE.     

Blood testing in biathlon: observation of hematocrit values during competitive periods 1994-1997.

The International Biathlon Union, through its own Medical Commission, has undertaken a three-year program aimed at identifying the hematocrit levels of athletes who participate in biathlons. The purpose was to check for hematocrit levels exceeding normal physiological values as well as for any significant modifications within individuals during the course of the competitive season. All of the athletes registered in international biathlon races were, therefore, subjected to venous blood sampling (1 cc) three times a year prior to competition, in the days preceding two World Cup races (December and January) and the World Championships (February). The blood was centrifuged, the micro-hematocrit determined, and the value (rendered anonymous) recorded. This procedure was repeated for three consecutive competitive seasons (Dec. 1994-Feb. 1995, Dec. 1995-Feb. 1996, Dec. 1996-Feb. 1997). During this three-year period, the collected data showed a significant lowering of the average hematocrit level. In fact, from the first February sampling to the third February sampling, the average hematocrit value for the male population dropped from 48.04 +/- 2.36 to 46.33 +/- 1.91, and for the female population from 44.05 +/- 2.44 to 42.52 +/- 1.92. Even the distribution of the absolute hematocrit values was modified from the first to the third competitive season, especially for the February sampling, with a > or = 50% reduction for males and a > or = 48% reduction for females.     

Autonomic response to hypobaric hypoxia assessed by time-dependent frequency decomposition of heart rate.

BACKGROUND: Acute hypoxia tolerance varies substantially among healthy individuals. We hypothesized that this variability results from a difference in autonomic (ANS) response to hypoxic stress. METHODS: Peripheral oxygen saturation, respiration and ECG were recorded from 21 healthy subjects (age, 29 +/- 7 yr) in an altitude chamber during normoxia, severe hypoxia (282 mm Hg), and mild hypoxia (360 mm Hg). Cardiovascular control was assessed by time-frequency decomposition of the heart rate signal applying the Selective Discrete Transform Algorithm (SDA). This procedure uses a variable time window, thus providing reliable physiological data even during transient states. Autonomic activity was quantified by power spectral density integrals over a 3-dimensional time-dependent spectral distribution of heart rate fluctuations. RESULTS: Subjects who had slower peripheral oxygen desaturation during severe hypoxia onset (mean 92.9 vs. 58.4 s) were those who displayed higher ANS activity in all ambient states, namely normoxia and hypoxia. These same subjects withstood hypoxia for significantly longer time periods (mean 313 vs. 244 s). CONCLUSION: Improved hypoxia tolerance is linked to enhanced autonomic activity, involving a better management of peripheral blood flow.     

Reflex heart rate response to variable onset +Gz

Rapid onset high sustained +Gz is a frequent requirement in air combat maneuvering. The cardiovascular response is inadequate to fully compensate for this rapid +Gz change. The rate of change in heart rate (HR) during gradual (0.1 G.s-1, GOR), rapid (1.0 G.s-1, ROR), and very high (6.0 G.s-1, VHOG) onset acceleration exposures to sustained (15 s) +7Gz, +8Gz, and +9Gz levels was measured in 81 healthy male subjects in a human centrifuge. The time (s) to reach maximum heart rate (T7) was measured as the time for the preacceleration exposure resting heart rate (RHR) to reach maximum heart rate (MHR). The change in heart rate upon reaching maximum +Gz level (delta HRA) from rest was calculated along with the change in HR from rest to the maximum heart rate achieved before maximum +Gz level was attained. During the ROR and VHOG runs, MHR was not achieved until after maximum +Gz level was attained. The change in heart rate from resting HR (immediately prior to acceleration) to the heart rate achieved at the onset of maximum +Gz level (delta HRA), decreased by 50% as the onset rate increased from GOR to ROR and VHOG. The delta HRB for very high onset rates exposures was significantly greater than that for ROR and GOR exposures. Acceleration exposure to levels of +7Gz and above (+7Gz, +8Gz and +9Gz) exhibited similar HR responses. VHOG to sustained +Gz stress levels of +7 to +9Gz for 15 s did not provide a sufficient length of time to allow maximum cardiovascular response.(ABSTRACT TRUNCATED AT 250 WORDS)     

立位耐力不良飞行员模拟飞行中心理生理反应与心率变异性分析

目的探讨立位耐力不良飞行员模拟空中环境下心脏自主神经功能调节状态和心理生理反应特点，为空中晕厥的诊断提供客观的评价方法。方法对２２名立位耐力不良（不良组）飞行员进行了连续动态心电记录和模拟飞行条件下的心理生理参数测定与心率变异性（ＨＲＶ）分析，并与１５名立位耐力正常的健康飞行员（健康组）做了对比。结果不良组飞行员在模拟仪表飞行中心理生理储备能力明显降低，表现为完成两项任务的质量和处理信息速度的能力较健康组低（Ｐ＜０．０１）；心血管自主神经功能严重失调；心理生理储备值与ＨＲＶ多数指标之间存在明显的相关性。结论结合模拟仪表飞行条件下的心理生理负荷评定和ＨＲＶ分析能较客观地反映立位耐力不良飞行员心血管自主神经功能障碍的发生机制和调节规律，为空中晕厥的诊断提供量化的指标。     

Fetal heart rate measurement during maternal exercise--avoidance of artifact

The purpose of this study was to investigate the possibility that motion artifact may override the recording of fetal heart rate (FHR) with Doppler ultrasound fetal monitors during maternal exercise on cycle ergometers and treadmills, and to test the efficacy of two-dimensional ultrasound directed M-mode echocardiographs for determining FHR during maternal treadmill exercise. Four pregnant women (26 to 30 yr, means = 28, gestational age = 28 to 34 wk) pedaled a cycle ergometer at 25 to 50 W, while a second group (N = 4) (24 to 36 yr, means = 29, gestational age = 30 to 37 wk) walked on a treadmill at either 1.5 or 2.0 mph. Fetal monitor recordings (Hewlett-Packard 8040A) were consistent with pedal rate in the range of 50 to 70 rpm and with stepping rate in the range of 70 to 76 steps per min at 1.5 mph and 100 to 106 steps per min at 2.0 mph on the treadmill. Actual mean FHRs (audible signal from fetal monitor) were in the normal range [150.5 +/- 10.25 bpm (cycle ergometer) and 148.8 +/- 2.3 bpm (treadmill)]. In a separate session, the cycle ergometer group walked on a treadmill at a maternal heart rate of 140 bpm while FHR was determined by two-dimensional ultrasound directed M-mode echocardiographs. Off-line analysis of fetal cardiac cycle time (clinical graphics analyzer) allowed accurate FHR measurements which were not confounded by motion artifact. Mean FHR during maternal treadmill exercise (158.0 +/- 12.0 bpm) was not different (P greater than 0.05) when compared to pre-exercise standing (140 +/- 3.6) and also during the post-exercise period (sitting) (151 +/- 6.5) compared to the sitting pre-exercise measurements (147 +/- 8.2).(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of the perceived and the ECG measured heart rate during cycle ergometer, treadmill and stairmill exercise before and after perceived heart rate training.

The ability to perceive exercise heart rate before and after training was tested in six young male university students, perceptions of heart rate being compared with ECG monitored heart rates during cycle ergometry, treadmill running and stairmill climbing. Between initial and final tests, subjects undertook 13 weeks of running training (2 h/day, 3-4 days/week), and during this period they compared their perceptions of heart rate with values observed on watch-type wrist-mounted pulse monitors. Individual initial perceptions showed only a moderate correlation with ECG values. This correspondence was improved as perceptions were compared with measured heart rates over the course of training, significantly so for the mode of exercise most similar to that adopted in the training sessions (treadmill running at a heart rate of 140 beats/min). The final accuracy of perceptions at a heart rate of 140 beats/min (error 8-9 beats/min during treadmill running) compared favourably with the accuracy of either pulse counting or the traditional rating of perceived exertion as commonly observed in the exercising public. This suggests that there may be an application for perceived heart rates in regulating the intensity of prescribed exercise.     

Serum uric acid, body fatness, and heart rate response to exercise.

Serum uric acid was determined in 2298 males and 2237 females, age 10-64. Body fatness (sum of four skinfolds) and heart rate response to a modified Harvard Step Test were also measured in these subjects. Age and sex specific correlation coefficients between SUA and heart rate response to the standard exercise were low (about 0.15 on the average) but more than half were statistically significant. SUA was more closely related to body fatness than to heart rate response to exercise. Removing the effects of body fatness from the SUA - heart rate response correlations decreased these correlations so that only about one per cent of the variation in SUA among people is associated with one's physical fitness as reflected in heart rate response to exercise.     

The reproducibility and prognostic value of serial measurements of heart rate response to regadenoson during myocardial perfusion imaging

Purpose

The heart rate response (HRR, percentage change from baseline) to regadenoson during myocardial perfusion imaging (MPI) can provide incremental prognostic value in patients with known or suspected coronary artery disease. Our purpose was to evaluate the variability and prognostic value of HRR on serial measurements.

Methods

We studied 648 consecutive patients (61?±?11 years, 48 % with diabetes) who underwent two regadenoson MPI studies (16?±?9 months between studies). HRR <30 % was defined as abnormal. All-cause mortality was determined by chart review and verified using the US Social Security Death Master File.

Results

HRR was well correlated between the two studies (intraclass correlation coefficient 0.72, 95 % CI 0.67?–?0.76) with no systematic bias (mean difference 0.88 %, p?=?0.2) or proportional bias (p?=?0.5) by Bland-Altman analysis in all patients and in those with normal MPI on both studies. Of the 308 patients (48 %) with normal baseline HRR (HRR-1), 33 % had developed a blunted HRR on the second MPI study (HRR-2). Older age, male gender, end-stage renal disease, and abnormal baseline left ventricular ejection fraction were independent predictors of a new-onset abnormal HRR. During a mean follow-up of 2.4?±?1.2 years, 55 patients (8.5 %) died. Patients with a blunted HRR-1 had increased mortality risk irrespective of their HRR-2 (p?=?0.9, log-rank test). Among patients with normal HRR-1, a blunted HRR-2 was an independent predictor of all-cause mortality beyond clinical and traditional MPI data (hazard ratio 2.83, 95 % CI 1.14?–?7.03). Finally, patients with a normal HRR-1 and HRR-2 had the lowest event rate, while those with any abnormal HRR had an increased risk of death (hazard ratio 2.5, 95 % CI 1.2?–?5.4).

Conclusion

There was good correlation in the HRR to regadenoson on serial measurements without systematic or proportional biases. Patients with consistently normal HRR had the best prognosis.