Estimation of the anaerobic threshold from the data on lung ventilation and heart rate variability

The goal of the study was to develop methods for estimating the anaerobic threshold from the rate of lung ventilation and heart rate variability during bicycle ergometer and treadmill tests with a stepwise increasing load. At the first stage, the method of estimation of the anaerobic threshold from lung ventilation data was developed. Forty-nine skilled ski racers participated in the experiment. They performed a treadmill ski-walking test with poles, with the slope gradually increasing from 0 to 25 degrees at a rate of one degree per minute. At the second stage, we developed a method for determining the anaerobic threshold from heart rate data. Eighty-six athletes of different sports specialties performed pedaling on a Monarch bicycle ergometer until exhaustion. The initial power was 25 W; the power increased by 25 W every 2 min. The pedaling rate remained constant (75 rpm). The lung ventilation, as well as oxygen consumption and carbon dioxide exhalation parameters, were measured using a COSMED K4 gas analyzer. Arterial blood was sampled from an earlobe or a finger; the blood lactate concentration was determined using an Akusport instrument. The RR intervals were recorded using a Polar s810i heart rate monitor. The results showed that the onset of ventilation anaerobic threshold (VAnT) determined by the graphical method coincided with the moment when blood lactate accumulated to 3.8 ± 0.1 mM in the treadmill test and 4.1 ± 0.6 mM in the bicycle ergometer test. The oxygen consumption at the VAnT level was found to be related to the variance of RR intervals (SD ₁). The following regression equation was derived: VO₂ AnT = 0.35 + 0.01SD ₁ W + 0.0016SD ₁ HR + 0.106SD ₁ (ms), l/min; (R = 0.98, function estimation error, 0.26 l/min, p < 0.001), where W (W) is power, HR is heart rate (bpm), and SD ₁ is the variance of RR intervals (ms) at the moment of recording of the heart rate threshold.     

Physical working capacity of male inhabitants from Upper Surinam

Aerobic power tests were carried out on twenty male Bushnegroes, as part of a medical survey in two villages on the Upper Marowijn river in the interior of Surinam (South America).The subjects were submitted to a discontinuous series of increasing submaximal loads by means of a bicycle ergometer. Heart rate and oxygen uptake were measured at each load. The maximum oxygen uptake was estimated according to Lange Andersen et al. (1971) and used as an index for the physical working capacity.The mean aerobic power of the Bushnegroes was 35 ml O₂/min/kg body weight or 2·2 I O₂/min per individual. These values are low in comparison with results obtained from professional forest workers in Surinam or in other countries.     

Characteristics of ventilatory control during exercise in coronary heart disease patients

The relationship between the carbon dioxide ventilatory equivalent and hemodynamic parameters during exercise was studied in healthy subjects and coronary heart disease (CHD) patients. Gas exchange, ventilatory control, and central hemodynamics during graded exercise were analyzed in 85 subjects, including 32 healthy subjects and 53 CHD patients. Twenty-seven CHD patients had coronary insufficiency but not heart failure and had a left ventricle ejection fraction of ≥50%; 26 patients had chronic heart failure and an ejection fraction of <40%. A high carbon dioxide ventilatory equivalent and its disturbed response (a decrease below 20%) with an increase in physical load, which reflects an imbalance of ventilatory control with decreased parameters of maximum oxygen consumption and hemodynamics, allows the ventilatory equivalent to be used as a marker for stratifying CHD patients with chronic heart failure.     

Effects of altitude on exercise level and heart rate in patients with coronary artery disease and healthy controls

Background. To evaluate the safety and effects of high altitude on exercise level and heart rate in patients with coronary artery disease compared with healthy controls. Methods. Eight patients with a history of an acute myocardial infarction (ejection fraction >5%) with a low-risk score were compared with seven healthy subjects during the Dutch Heart Expedition at the Aconcagua in Argentina in March 2007. All subjects underwent a maximum exercise test with a cycle ergometer at sea level and base camp, after ten days of acclimatisation, at an altitude of 4200 m. Exercise capacity and maximum heart rate were compared between groups and within subjects. Results. There was a significant decrease in maximum heart rate at high altitude compared with sea level in both the patient and the control group (166 vs. 139 beats/min, p<0.001 and 181 vs. 150 beats/min, p<0.001). There was no significant difference in the decrease of the exercise level and maximum heart rate between patients and healthy controls (-31 vs. -30%, p=0.673). Conclusion. Both patients and healthy controls showed a similar decrease in exercise capacity and maximum heart rate at 4200 m compared with sea level, suggesting that patients with a history of coronary artery disease may tolerate stay and exercise at high altitude similarly to healthy controls. (Neth Heart J 2010;18:118-21.)     

Ammonia production following maximal exercise: treadmill vs. bicycle testing.

From a population of 20 healthy male volunteers, half performed constant speed, incremental load maximal aerobic capacity (VO2max) tests on a motor-driven treadmill, while the other half performed similar VO2max tests on a bicycle ergometer. The two groups, matched for size and age, showed no significant differences in VO2max, maximum heart rate, or in post-exercise (4 min ) peripheral venous blood concentrations of lactete or pyruvate. However, post-exercise peripheral venous blood ammonia levels were significantly higher in the group tested on the bicycle ergometer than in the treadmill group.     

Changes in the power of the low- and high-frequency bands of the heart rate variability spectrum in coronary heart disease patients with different severities of coronary atherosclerosis in the course of load tests

The specific features of the changes in the low-frequency (LF) and high-frequency (HF) bands of the heart rate variability (HRV) spectrum were studied in coronary heart disease (CHD) patients with different numbers of coronary arteries affected by hemodynamically significant stenosis in the course of a bicycle exercise test. Male patients (143) with CHD aged 49 ± 8 years participated in the study. Subgroups with hemodynamically siginificant stenosis in one, two, or three coronary arteries; with no stenosis; and with a varying degree of total coronary bed lesion were distinguished. Tachograms were recorded in the course of bicycle exercise tests with loads of 25 and 50 W with spontaneous respiration for 3 min at each stage of a test. The frequency estimates of HRV in the LF and HF bands of the spectrum were obtained using the parametric method for constructing the spectrum based on the autoregressive model. It was shown that hemodynamically significant coronary stenoses significantly influenced the state of the mechanisms of autonomic regulation of the heart, which, in CHD patients with a three-vessel coronary lesion, is characterized by an extremely low adaptability.     

Radio Telemetry of the Electrocardiogram,Fitness Tests,and Oxygen Uptake of Water-Polo Players

During competitive water polo, heart rate in six subjects was monitored by cupped plastic and silver electrodes glued to the skin. Minimum rates during the game averaged 156 beats/min.; maximum rates averaged 186 beats/min. Mean maximum rate with bicycle exercise was 188 beats/min. Maximum oxygen (VO₂ max.) with bicycle exercise of 14 water-polo players was 53.3 ml./kg. Physical working capacity (PWC 170) was 1310 kilopond metres per square metre (k.p.m./sq.m.). PWC 170 correlated well with VO₂ max. in this small group (r = 0.77).Oxygen uptake was measured at three speeds of swimming and four levels of work on a bicycle ergometer. VO₂ max. of swimming was 88% of that obtained on bicycle exercise. The slope of the oxygen uptake vs. pulse rate curves was less for the swimming than for cycling, so that for a given oxygen uptake below the maximal, pulse rate was less in the swimmers. At near-maximal swimming, respiratory quotient was 0.95 compared with 1.27 for cycling, suggesting that the swimmers were underbreathing.     

The role of behavioral conditioning in the cardiovascular adjustment to exercise

The purpose of this study was to determine if normal subjects could be trained to attenuate their cardiovascular responses while exercising on a bicycle ergometer. Ten young, untrained subjects exercised on a bicycle ergometer for five sessions. Half of the group was asked to slow their heart rate while exercising with heart rate feedback during exercise. Their average heart rate increase was 20% less than that of the control subjects, who exercised without feedback. The control subjects subsequently also received feedback during exercise and they were able to attenuate their heart rate responses comparably. Systolic blood pressure was not affected by feedback training. Changes in rate-pressure product paralleled changes in heart rate. These data show that autonomically mediated adjustments to exercise can be brought under experimental control through the use of appropriate behavioral techniques.     

Effect of Rhodiola rosae L. cryopowder on the indices of the cardiorespiratory system and physical working capacity in humans

The effects of snowdon rose (Rhodiola rosae L.) cryopowder on the cardiorespiratory system was studied using a 7-h bicycle ergometer test. The treatment resulted in more rapid activation of the mechanisms of energy supply to the body during physical load as compared to the control. Moreover, the efficiency of the functions of the cardiovascular and respiratory systems was higher, and the indices of fatigue after long-term physical load disappeared. The cryopowder from the crude material for drugs had a strong protective effect and may be recommended for the use under extreme conditions.     

Linear and non-linear analysis of cardiac health in diabetic subjects

Diabetes is a chronic disease characterized by hyperglycaemia, which leads to specific long-term complications: retinopathy, neuropathy, nephropathy and cardiomyopathy. Analysis of cardiac health using heart rate variation (HRV) has become a popular method to assess the activities of the autonomic nervous system (ANS). It is beneficial in the assessment of cardiac abnormalities, because of its ability to capture fast fluctuations that may be an indication of sympathetic and vagal activity.This paper documents work on the analysis of both normal and diabetic heart rate signals using time domain, frequency domain and nonlinear techniques. The study is based on data from 15 patients with diabetes and 15 healthy volunteers. Our results show that non-linear analysis of HRV is superior compared to time and frequency methods. Non-linear parameters namely,correlation dimension (CD), approximate entropy (ApEn), sample entropy (SampEn) and recurrence plot properties (REC and DET), are clinically significant.     

The relationship of the slope of the heart rate graph regression with linear and nonlinear heart rate dynamics in stationary short-time series

The relationship of the slope of the heart rate graph regression curve (b ₁) with periodic (linear) and nonlinear heart rate dynamics has been studied in stationary short-time series (256 points). For estimating nonlinear dynamics, a parameter derived from correlation dimension has been used, which has made it possible to estimate chaotic processes in short-time series. According to the results of the study, the heart rate dynamics in short-time series may be represented as a sum of linear (periodic) and nonlinear (stochastic) processes. The relationships of b ₁ with both the linear and the nonlinear heart rate dynamics have been demonstrated. Equations for calculating the absolute and relative (to the periodic oscillation amplitude) noises in the heart rate dynamics in short-time series are proposed. Stochastic nonlinear dynamics in different physiological states of humans have been compared. It has been found that the increase in the relative noise intensity in the heart rate dynamics with an increase in respiration rate is determined not only by the decrease in the amplitude of respiratory waves, but also by an increase in the amplitude of the noise itself. The absolute noise intensity is decreased in the states of neurotic excitement, fatigue, and, especially, mental stress. In the state of rest, nonlinear (stochastic) processes dominate over linear (periodic) ones.     

Evaluation of commercially available heart rate monitors.

The accuracy and tracking ability of nine commercially available heart rate monitors were assessed. The heart rate of 16 young healthy men was continuously monitored by a single-lead electrocardiograph while they exercised on a stationary bicycle ergometer. Readings were obtained from the devices during exercise. The devices that measured the cardiac electrical potential with a three-electrode system or that incorporated a light transmission device attached to the earlobe were the most accurate and provided suitable monitoring of the heart rate during exercise.     

The effects of negative air ions on various physiological functions during work in a hot environment

The effects of negative air-ions on human physical performance has been investigated. Twenty-one healthy males, 20–25 years old (X=23.6±2.6) were exposed to two 180-min rest and exercise sessions two weeks apart. The subjects were randomly assigned into either an experimental group (n=12) or to a control group (n=9). The experimental group performed the first session in neutral air conditions and the second one in air containing 1.36 to 1.90×10⁵ negative air ions and 1.40 to 1.66×10² positive air ions/ml. The control group performed both sessions under neutral air conditions. All sessions were held at T_a=40±1C and 25±5% RH. Each session included one hour of resting under the respective ionization conditions, followed by 3 30-min cycle ergometer work bouts, separated by 7-min rest periods. The mechanical work-load during the bicycle exercise was 1.64±0.6 W/kg BW. The experimental group showed a significant reduction with negative air-ions in heart rate (HR), in rectal temperature, and in the rating of perceived exertion (RPE), all when compared with their own neutral session. The control group showed no significant changes between the first and the second exposure. Although not statistically significant, being exposed to negative air-ions seems also to reduce total sweat rate and minute ventilation (V_E), and to increase O₂ pulse. It is suggested that under the conditions of this study negative air ions canimprove various cardiovascular and thermoregulatory functions as well as subjective feelings during physical effort. It is felt that such positive influences may be augmented by increasing the exposure time to negative ionized air and/or prolonging the stressful conditions.With the technical assistance of M. Sheinovitz.     

Higher Carbohydrate Antigen 125 Levels Are Associated with Increased Risk of Coronary Heart Disease in Elderly Chinese: A Population-Based Case-Control Study

Background

High carbohydrate antigen 125 (CA-125) level was reported to be associated with some cardiac dysfunctions, such as chronic heart failure, but the relationship between CA-125 level and coronary heart disease (CHD) risk remains unclear. The aim of this study was to explore the potential association in a Chinese older population.

Methods

In a population-based case-control study conducted in a Chinese older population, serum CA-125 levels were measured in 1177 diagnosed CHD patients and 3531 age and sex matched control subjects without CHD.

Results

Serum CA-125 level was significantly higher in CHD patients than controls (P < 0.001) with adjustment for age, gender, smoking, drinking, BMI, physical activity, hypertension, dyslipidemia, diabetes mellitus, medication history and family history of CHD and myocardial infarction. CHD risk was doubled (OR: 2.10, 95%CI: 1.69-2.60) among subjects in the highest quartile compared to those in the lowest quartile of CA-125 level (P _trend < 0.001). Furthermore, CA-125 levels were associated with CHD risks in subjects with age over 60 years (OR: 2.19, 95%CI: 1.75-2.73), current smokers (OR: 2.29, 95%CI: 1.50-3.49), current drinkers (OR: 2.35, 95%CI: 1.57-3.53) and subjects with hypertension (OR: 2.04, 95%CI: 1.71-2.43).

Conclusions

Elevated serum CA-125 level might be associated with increased risk of coronary heart disease in the Chinese older population. Further investigations are needed to identify the possible biological role of CA-125 in CHD development in the future.     

Influence of external periodic stimuli on heart rate variability in healthy subjects and in coronary heart disease patients

Frequency estimates of the heart rate variability (HRV) spectrum influenced by external periodic stimuli were studied in healthy subjects and patients with coronary heart disease (CHD). Sensory stimulation by periodic eye opening at a rate of 15, 10, 8, 6, or 5 times per minute, as well as spontaneous and controlled breathing at a rate of 15, 10, 8, 6, or 5 times per minute, was used. It was found that the spectral response to external periodic oscillations was determined by a frequency-dependent phenomenon, the maximal amplitude of heart rate variations being observed in the case of external stimuli at a frequency of 0.1 Hz. A resonance frequency in the 0.1-Hz range may be suggested to exist in the cardiovascular controls. Significant differences in the HRV frequency characteristics between CHD patients and healthy subjects were shown. CHD patients had a characteristic decline in HRV responses to external oscillations; the power of these responses did not depend on the frequency of external stimuli.     

Anthropometric indices and physical fitness in university undergraduates with different physical activity.

Physical activity and fitness have important health promoting effects with respect to arterosclerosis and coronary heart disease in particular. An intervention study of physical status and physical activity in university undergraduates (University of Tartu) has been carried out. The physically inactive (Group I) consisted of 310 undergraduates (235 females and 75 males) of the Faculty of Medicine. The physically active (Group II) was recruited from among undergraduates (22 females and 23 males) of the Faculty of Exercise and Sport Sciences, who participated in training sessions regularly, 3 to 5 times per week. Anthropometric body measurements, arm force, vital capacity and exercise test on the bicycle ergometer (PWC170) were performed. There were no statistically significant differences between the mean values of anthropometric indices in case of physically inactive and physically active female subjects. In the group of physically active male undergraduates, weight and shoulder width were larger than in students with physically sedentary life style (p < 0.05). Most of the female and male students had normal BMI. There were statistically significant differences in the mean values of vital capacity, arm force and aerobic working capacity between the study groups, while physically active students had higher physical capacity (p < 0.001). Mean anthropometric indices demonstrated a statistically significant increase in both female and male university undergraduates after the interval of 30 years. Normal BMI and anthropometric indices do not serve a as guarantee of physical fitness for university undergraduates who are involved in sedentary life style. Regular physical activity has a strong positive impact on physical fitness, particularly on aerobic capacity which is the most important health promoting component of physical fitness with respect to coronary heart disease.     

Relation between natriuresis and urinary excretion of hydrogen peroxide

Changes in the urinary hydrogen peroxide by exercise or salt load were studied in six healthy male volunteers. Exercise was performed by bicycle ergometer for 30 min at the intensity of 80% of the maximum heart rate predicted by age. Urinary excretion rate of hydrogen peroxide showed a tendency to increase in the salt load experiment, and to decrease by exercise. Correlation coefficient between urinary excretion rate of sodium and hydrogen peroxide one hour after the load was 0.797 (0.1 > p > 0.05) in the exercise experiment, 0.892 (p <0.05) in the salt load experiment and 0.877 (p < 0.001) in both experiments. Correlation coefficient between area under the curve for sodium excretion and hydrogen peroxide excretion was also as high as 0.822 (p < 0.05) in the exercise experiment, 0.909 (p < 0.05) in the salt load experiment and 0.853 (p < 0.001) in both experiments. These results may suggest that urinary excretion rate of hydrogen peroxide is closely related to metabolism of electrolytes and fluid in the renal tubules.     

Correlations Between the Manifestations of Autonomic Regulation Related to the Orthostatic Test and Physical Loading

In 30- to 45-year-old healthy men (workers of the coal mines), we studied using correlation analysis the interrelations between the manifestations of autonomic regulation of the heart rhythm related to the active orthostatic test (AOT) and the state of systemic circulation in the physical loading test (PhLT). It has been concluded that the pattern of correlations is determined by the direction of autonomic regulatory drives within a transitional period of the AOT. In the group of tested persons with clear domination of ergotropic reactions, the variation range and power of a slow wave component of the heart rhythm in the standing posture strictly correlated with the cardial stroke, peripheral resistance, vascular tone, myocardial tension, and aerobic productivity. In persons with relatively balanced ergotropic and trophotropic effects, the AOT transitional period was characterized by correlations of nearly all indices of autonomic regulation of the heart rhythm with the indices of central hemodynamics of the PhLT.