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This study combined user-avatar similarity and Proteus effect predictions to incentivize physical activity. 305 participants ran while wearing accelerometers and a heart rate monitor. They were randomly assigned to onscreen motion-capturing avatars displaying either participant or stranger faces dressed in sports or formal clothes. Participants assigned to avatars displaying their own face showed increased cardiac frequency compared with those exposed to avatars with a stranger's face. Relative to the remaining conditions, participants assigned to avatars with their own face also wearing sports clothes showed increased cardiac frequency but participants assigned to avatars with a stranger's face wearing formal clothes showed decreased cardiac frequency. The results imply that user-avatar similarity and the Proteus effect can be harnessed to influence physical activity.

Interoception (the sensing of inner-body signals) is a multi-faceted construct with major relevance for basic and clinical neuroscience research. However, the neurocognitive signatures of this domain (cutting across behavioral, electrophysiological, and fMRI connectivity levels) are rarely reported in convergent or systematic fashion. Additionally, various controversies in the field might reflect the caveats of standard interoceptive accuracy (IA) indexes, mainly based on heartbeat detection (HBD) tasks. Here we profit from a novel IA index (md) to provide a convergent multidimensional and multi-feature approach to cardiac interoception. We found that outcomes from our IA-md index are associated with –and predicted by– canonical markers of interoception, including the hd-EEG-derived heart-evoked potential (HEP), fMRI functional connectivity within interoceptive hubs (insular, somatosensory, and frontal networks), and socio-emotional skills. Importantly, these associations proved more robust than those involving current IA indexes. Furthermore, this pattern of results persisted when taking into consideration confounding variables (gender, age, years of education, and executive functioning). This work has relevant theoretical and clinical implications concerning the characterization of cardiac interoception and its assessment in heterogeneous samples, such as those composed of neuropsychiatric patients. Fil: Fittipaldi, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Abrevaya, Sofia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: de la Fuente de la Torre, Laura Alethia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Pascariello, Guido Orlando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas. Universidad Nacional de Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas; Argentina Fil: Hesse Rizzi, Eugenia Fátima. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Birba, Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Salamone, Paula Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Hildebrandt, Malin. Institute for Clinical Psychology and Psychotherapy; Alemania Fil: Alarco Martí, Sofía. Universidad Favaloro; Argentina Fil: Pautassi, Ricardo Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina Fil: Huepe, David. Universidad Adolfo Ibañez; Chile Fil: Martorell Martorell, Miquel. Universidad Favaloro; Argentina Fil: Yoris, Adrián. Universidad Favaloro; Argentina Fil: Roca, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: García, Adolfo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Sedeño, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina Fil: Ibañez, Agustin Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Instituto de Neurología Cognitiva. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt | Fundación Favaloro. Instituto de Neurociencia Cognitiva y Traslacional. Fundación Ineco Rosario Sede del Incyt; Argentina. Universidad Adolfo Ibañez; Chile. Universidad Autónoma del Caribe; Colombia

Introduction In the field of cardiovascular diseases an ergometer test is a common diagnostical method in which a change in microcirculation can be reached. In this paper cardiac frequency and cutaneous microcirculation during and after exercising will be compared with each other. Materials and methods The cutaneous microcirculation of 6 healthy volunteers (2 females, 4 males) is measured. As an instrument the PeriFlux 5000 combined with a Laser-Doppler-Flow(LDF)-Probe (Perimed Instruments) is used. The cardiac frequency (CF) is measured by the POLAR T31 sensor and as an ergometer the ERGO-FIT ® 457 is used. Results The mean initial LDF (97,7±57,3 PU) decreases at the beginning (64,5±21,7 PU), increases during theexercise, reaches its maximum (247,8±82,1 PU) after the end of the exercise and drops to lower values (256,4±69,5 PU)after a few minutes. Contrasting to the LDF the mean initial CF (86±22/min) increases at the beginning (97±9/min),furthermore during the whole exercise (103±9/min) and then falls after having finished the exercise (96±3/min).Furthermore, during regeneration, one can see the CF decreasing towards its initial value, while LDF reaches its maximum. Conclusion In further studies, realized with volunteers with well-known levels of physical condition, a directconnection between cutaneous microcirculation and physical condition might be found.

In elderly individuals balance disorders and muscle weakness can lead to prescribing a walker. There are several different models. According to the very poor effort tolerance in this population, the energy cost necessary to operate walking technical aids should be taken into account when making a choice.ObjectiveCompare two types of walker in regards to energy cost produced during gait in weakened elderly individuals.MethodThirty subjects over the age of 65 (six men and 24 women, mean age 81.9 years) were admitted in geriatrics care. They all required a walker and performed the same 10-m course with a fixed walker, then with a model bearing front wheels. The walking speed (S) was computed, heart rate at rest (HRrest) and maximum heart rate (HRmax) were recorded during the test. The physiological cost index (PCI=HRmax−HRrest/S) was calculated. Finally a timed get-up-and-go (TGUG) test was performed with each of these technical aids.ResultsWith a rollator walker, HRmax was lower (P

The technology of intrapartum surveillance made rapid strides from the 1960s through the 1980s but then stagnated as increasing resort to caesarean section was made rather than improving measures of fetal condition and labour progress. However, despite caesarean section rates commonly over 30%, medicolegally expensive mistakes continue to be made because it is difficult to teach clinicians to make reliable use of existing technology. It may be that as with aircraft navigation, the safest solution is to replace human judgement with the obstetric equivalent of automatic pilots.

We examined the association between ambient air pollution levels and heart rate variability (HRV) in a panel study of 32 subjects.We used linear mixed models to analyze the effects of fine particles (PM2.5), sulfate (SO4), elemental carbon (EC), and gases on log-transformed standard deviation of normal RR intervals (SDNN), mean square of differences between adjacent RR intervals (r-MSSD), and high- and low-frequency power (HF, LF).An interquartile range (IQR) increase of 5.1 mug/m in SO4 on the previous day was associated with a decrease of -3.3% SDNN (95% confidence = -6.0% to -0.5%), -5.6% r-MSSD (-10.7% to -0.2%), and -10.3% HF (-19.5% to -0.1%). Associations with total PM2.5 were similar. HRV was not associated with EC, NO2, SO2, or O3.In addition to traffic-related particles, elevated levels of sulfate particles may also adversely affect autonomic function.

The purpose of this study was to investigate changes in post-exercise heart rate recovery (HRR) and heart rate variability (HRV) during an overload-tapering paradigm in marathon runners and examine their relationship with running performance. 9 male runners followed a training program composed of 3 weeks of overload followed by 3 weeks of tapering (-33 ± 7%). Before and after overload and during tapering they performed an exhaustive running test (T(lim)). At the end of this test, HRR variables (e.g. HRR during the first 60 s; HRR(60 s)) and vagal-related HRV indices (e.g. RMSSD(5-10 min)) were examined. T(lim) did not change during the overload training phase (603 ± 105 vs. 614 ± 132 s; P = 0.992), but increased (727 ± 185 s; P = 0.035) during the second week of tapering. Compared with overload, RMSSD(5-10 min) (7.6 ± 3.3 vs. 8.6 ± 2.9 ms; P = 0.045) was reduced after the 2(nd) week of tapering. During tapering, the improvements in T(lim) were negatively correlated with the change in HRR(60 s) (r = -0.84; P = 0.005) but not RMSSD(5-10 min) (r = -0.21; P = 0.59). A slower HRR during marathon tapering may be indicative of improved performance. In contrast, the monitoring of changes in HRV as measured in the present study (i.e. after exercise on a single day), may have little or no additive value.

Cold immersion evokes the life-threatening cold shock response (CSR). We hypothesised that anxiety may increase the magnitude of (Study 1), and diminish habituation to (Study 2), the CSR. Study 1: eleven participants completed two 7-min immersions in cold water (15 °C). On one occasion, to induce anxiety, participants were instructed that the water would be 5 °C colder (ANX); it was unchanged. The other immersion was a control (CON). Study 2: ten different participants completed seven, 7-min immersions. Immersions 1-5 induced habituation. Immersions 6 and 7 were counter-balanced to produce anxiety (ANX) or acted as a control (CON). Anxiety (20 cm scale) and cardiorespiratory responses (cardiac frequency [f(c)]), respiratory frequency [f(R)], tidal volume [V(T)], minute ventilation [V(E)]) were measured in both studies. Results of study 1: participants were more anxious in the ANX immersion (mean [SD]; CON 5.3 [3.6] and ANX 8.4 [5.0] cm). f(c) peaked at higher levels in ANX (136.4 [15.0]; CON: 124.0 [17.6] b min(-1)) and was higher pre-immersion and in minutes 3 and 5-7 by 7.2 [2.1] b min(-1). ANX [Formula: see text] was higher pre immersion and in minutes 5-6. Results of study 2: repeated immersion habituated the CSR. Anxiety was greater prior to ANX (CON 1.9 [2.3], ANX 6.6 [4.8] cm). f (c) in ANX was higher prior to immersion and in minutes 1-2, 4-6 cf CON; ANX f (c) was not different to the CSR seen in pre-habituation. f (R) was higher in minute 1 of immersion 1 (cf min 1 CON and ANX) following which it exceeded the CSR in CON. The magnitude and duration of CSR (f(c), V(E)) increased with anxiety. Anxiety diminishes CSR habituation.

It is still unknown whether specific components in fine particles are associated with heart rate variability (HRV) reduction.We recruited 46 patients with or at risk for cardiovascular diseases to measure 24-hour HRV by ambulatory electrocardiographic monitoring. Fixed-site air-monitoring stations were used to represent participants' exposures to particles with aerodynamic diameters less than 10 microm (PM 10) and 2.5 microm (PM2.5), and particulate components of sulfate, nitrate, organic carbon (OC) and elemental carbon, and gaseous pollutants.We found that HRV reduction was associated with sulfate, OC, and PM2.5 but not with the other five pollutants in single-pollutant models. Sulfate was found to remain in significant association with HRV reduction adjusting for OC and PM2.5 in three-pollutant models.Exposures to sulfate and OC in PM2.5 were associated with HRV reduction in patients with or at risk for cardiovascular diseases.

The [13C]mixed triacylglycerol (MTG) breath test is a non-invasive measure of fat digestion and can be used to assess the need for enzyme replacement therapy in children with cystic fibrosis (CF). However, it lacks specificity. Quantitation of cumulative percent dose recovered (cPDR) requires knowledge of carbon dioxide production rate (VCO2). A resting value is assumed, but children are unlikely to remain at rest during the test.To improve the specificity and therefore the positive predictive value (PPV) of the MTG breath test using calibrated heart rate monitors to estimate non-resting VCO2.Proof of concept study.Six children with CF, 10 healthy children and eight healthy adults performed [13C]MTG breath tests.Heart rate monitors were worn throughout the test. Non-resting VCO2 was estimated continuously from heart rate. Percentage dose recovered was calculated using predicted resting VCO2, measured resting VCO2 and non-resting VCO2 estimated from heart rate. Physical activity level (PAL) was taken as cPDR calculated using non-resting VCO2 divided by cPDR calculated using measured resting VCO2. The cutoff point was determined using two graph-receiver operator characteristics.Use of calibrated heart rate monitors to estimate non-resting VCO2 improved the specificity of the test. The PPV increased from 0.67 to 0.99. PAL was 1.3 in adults and children who performed the test in hospital, and 1.7 in children who performed the test at home.Individually calibrated heart rate monitors are useful tools to estimate non-resting VCO2 during the [13C]MTG breath test.

This project investigated the sensitivity of oxygen uptake (VO(2)) dynamics to training-induced physiological changes, across a broad spectrum of endurance-training histories. Forty subjects participated: sedentary (n = 10), active healthy (n = 10), regular runners (n = 10), and competitive distance runners (n = 10). Subjects completed a cycle step-function protocol, to elicit a steady state at 60% maximal work rate. Breath-by-breath data were collected for VO(2) and cardiac frequency (f(c)), and modelled mathematically, and used to determine the average response times to attain 20%, 40%, 60%, 80% and 100% of the respective steady states. The between-group comparisons for both VO(2) and f(c) revealed significantly faster response times to 40%, 60%, 80% and 100% of the induced response, for the better trained subjects (P0.05). In general, this technique permitted differentiation between the VO(2) and f(c) response dynamics of non-elite subjects from a broad range of endurance-training histories, with differences becoming more pronounced as subjects approached the steady state.

Cardiac frequency (f c) was recorded in 101 coal-face miners [mean age 32.7 (range 21–49) years, mean height 169.6 (range 150–185) cm, mean body mass 76.9 (range 54–106) kg, mean maximal cardiac frequency (f cmax) 180.2 (range 154–197) beats min−1, mean maximal oxygen uptake $$(\dot VO_{2max} )$$ 2.93 (range 1.9–4.0) l · min−1] with a small-size, nonintrusivef c counter, during the five (n = 76) or at least four (n = 25) work-shifts in a week. Thef cmax and $$\dot VO_{2max} $$ were determined during a progressive test to exhaustion on a treadmill. Overall (four to five work-shifts) mean work-timef c (f c) was 97.7 (range 74.9–122.4) beats · min−1, restingf c (f c rest) 59.1 (range 50–75) beats · min−1, work-time increase inf c (f c —f c rest) 38.5 (range 21.1–55.8) beats · min−1 and percentage off c reserve used (f c reserve =f c max —f crest)32.0(range 18.5–50.9). Multiple regression analysis showed thatf c andf c —f c rest, as dependent variables, correlated with predicted percentage of CO lung diffusion capacity, (D LCOSB%) (r = −0.334 andr = −0.273, respectively) but not with age,f c max, $$\dot VO_{2max} $$ , $$\dot VO_{2max} $$ · kg−1 body mass, effort test Δoxygen uptake/Δf c or percentage of forced expiratory volume in 1 s as independent variables. The percentage off c reserve used as dependent variable, correlated withD LCOSB (r = − 0.265) andf c max (r = − 0.227) but not with any of the other variables listed. Individual differences in worktimef c are thus large and virtually unpredictable. Other physiological variables not taken in account here (i.e. sense of effort, fatigue perception) as well as psychological ones (work satisfaction, motivation) may have played a role in those differences. At peaks of effort, some subjects reachedf c values within the range off c max.

The effects of hot and cool environments on perceptual and physiological responses during steady-state exercise were examined in men (n = 14) performing 30 min of constant exercise (cycle ergometry) at a perceived exertion of "somewhat hard". Subjects exercised at the same absolute exercise intensity in hot (40 degrees C), neutral (24 degrees C), and cool (8 degrees C) conditions. Data were collected for differential ratings of perceived exertion (RPE), affect, thermal sensation, mean skin (Tsk) and rectal temperatures (Tre), and cardiac frequency (fc). The subjects completed the hot exposure with an average Tsk of 37.5 degrees C (SEM 0.11), while the neutral and cool conditions produced values of 33.8 (SEM 0.09) and 28.2 degrees C (SEM 0.30), respectively. The Tsk was significantly higher in the hot than the neutral and cool conditions throughout exercise (P < 0.05). The fc was significantly lower in the cool than in the other conditions (P < 0.05), and the subjects completed the hot exposure with a mean fc more than 20 beats.min-1 greater than observed in the other conditions. The subjects felt worse (lower affect) in the heat throughout exercise (P < 0.05). Overall RPE was significantly lower in the cool than in the heat, while chest RPE scores for the cool and hot conditions were displaced vertically by approximately two points. Subjects perceived work to be harder, felt worse, and experienced greater thermal sensation in the hot condition, compared with the neutral and cool conditions. Changes in cutaneous vasomotor tone and heat-induced influences on the chest may have accounted for the RPE changes observed in the heat.

Using as subjects 18 mine rescue brigadesmen, thecardiac frequency during stepping exercise at three rates of work has been compared with that during progressive and rectangular exercise on a treadmill and with the Harvard Pack Index of physical fitness. The latter may be predicted with rather greater accuracy from the cardiac frequency during stepping than during treadmill walking. The absolute levels of frequency relative to oxygen uptake are higher during the stepping exercise than during treadmill walking; this should be taken into account when cardiac frequency is used for prediction of energy expenditure. The levels of ventilation with respect to oxygen uptake are similar for the two forms of exercise.

In this article, the authors propose an original analysis of the cardiac frequency after training. The study of rapid diminution (alactic oxygen debt) and of plateau (lactic debt in oxygen) make possible adjustment of the training. The variations observed in young swimmers during their sporting season and note a tangible improvement of the two components for recovery.

1. Ventilation and cardiac frequency were measured during repeated treadmill exercise in three healthy subjects over 36 weeks, before, during and after iron-deficiency anaemia was produced and after iron treatment. The haemoglobin and 2,3-diphosphoglycerate concentrations and the oxygen-binding (P50) were measured. 2. There was an inverse relationship between the haemoglobin concentrations and the 2,3-diphosphoglycerate concentrations and the P50 values. 3. The mean cardiac frequencies during the fourth to tenth minutes of exercise showed a negative correlation with the haemoglobin concentrations in all three subjects, and the mean minute ventilations in two of them.

Sensitivity of heart rate to attentional drive is ofconcern when field evaluating metabolic load by ECG telemetry. With six groups of women at varying levels of heart rate achieved by exercise or heating, an unexpected, explosive noise elicited a mean cardiac startle elevation of 9 beats min-1 in resting subjects with linear attenuation under increasing heart rate. With group mean values of 125 beats min-1 or greater, no significant acceleration from startle remained. Pre-startle, beat by beat variability decreased with elevation of heart rate; startle increased this variability. The attenuation of mean startle responses supports Wilder's Law of Initial Values and indicates that field metabolic evaluations which use telemetered heart rates from work of moderate or greater intensity are not confounded by the intrusion of such attention commanding stimuli.

Recording the fetal cardiac rhythm (FCR) is currently the technique most widely used to assess the well being of the fetus. In view of the importance of the decisions taken on the modifications of the FCR, the authors have recorded and analysed over 24 consecutive hours 10 resting women manifesting a strictly normal pregnancy. They observed no modification in the basal cardiac frequency, very few declarations and above all, never any signs of a flat or sinusoidal rhythm. Flattening of the FCR is invariably pathological. It must not be interpreted as “fetal sleep” period, but it should intensify the surveillance.

1. Submaximal bicycle exercise tests have been performed in nine healthy men on seven annual occasions between the ages of 64 and 70 years. Ten younger men (average age 33 years) have also been studied once for comparison. 2. The ventilatory cost of submaximal work at V̇o2 = 1 litre/min rises significantly from 24.3 ±0.8 litres/min at age 64 years to 31.8 ± 1.8 litres/min at age 70 years; the latter value differs significantly from that of the young men (25.6 ± 0.9 litres/min). Similar changes are seen in the ventilation at 75 W and at V̇co2 = 1 litre/min. The rate of change, between 3% and 5% per year, is considerably greater than that found for the change with age in cross-sectional studies of younger men. There is also a rise in the respiratory quotient, consistent with the hyperventilation found. 3. The cardiac frequency at 1 litre/min also rose with age in the older men, and rough estimates of the decline in their aerobic capacity suggest that progressive anaerobiosis could account for at least some of this increase in ventilation seen during submaximal work.

1. Acute hypocapnic hypoxia was induced in ten healthy subjects by the inhalation of O2+N2 (10:90) at rest and during exercise. Transient relief of hypoxia by two breaths of O2 (O2 test) resulted in a decrease in cardiac frequency which was highly significant about 10 s after the tests and never consistently delayed in comparison with the ventilatory changes. 2. β-Adrenergic blockade with propranolol reduced the magnitude of the changes in cardiac frequency but not their time-course. 3. Cholinergic blockade with atropine sulphate (and double blockade) abolished the early changes in cardiac frequency. During continued O2 breathing (3 min) small, still significant, changes were observed. 4. It is concluded that the decrease in cardiac frequency within 10 s of relief of hypoxia is dependent on efferent vagal activity.

In normal males during submaximal exercise at a constant rate of external work on a bicycle ergometor or step test, the oxygen uptake and ventilation are linear functions of body weight. In normal females the mean oxygen uptakes do not differ materially from those for males of comparable weight. However, because of the constant terms in the regression equations, the convention of expressing results per kg body weight or m2 body surface area may give rise to error; for ventilation this may be avoided by the use of the regression on oxygen uptake. Alternatively, the results may be reported at a constant oxygen uptake, for example, for men 1·5 1/min as recommended by J.L.O. and for women 10·l/min; the ventilation is then independent of body weight. By this procedure allowance is also made for differences in oxygen uptake duo to the effects of practise. For the cardiac frequency a similar adjustment to a constant oxygen uptake yields values which are negatively correlated with body weight for walking on a tre...

The cardiac frequency (f H ) and oxygen intake ( $$\dot V_{O_2 } $$ ) responses to submaximal and maximal work with 1- and 2-arms and 1- and 2-legs on suitably modified bicycle ergometers in relation to the prediction of maximal aerobic power output ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ) have been examined in 12 healthy male subjects. The results showed that the physiological responses to the different forms of submaximal and maximal exercise were distinct and dependent upon the effective muscle mass used to perform the work. The observed $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ of 1-limb could be converted to respective 2-limb value with a coefficient of variation ranging from 4 to 7%, but maximal work with the arms gave no guide to that of the legs. Extrapolation of the $$\dot V_{O_2 } $$ /f H curve to the f H max in 1-leg (175 beats/min) and 2-arm (165 beats/min) resulted in an overestimation of $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ of +70 ± 200 ml · min−1 and +70 ± 240 ml · min−1; but in 1-arm work (153 beats/min), $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ was underestimated by −70 ± 270 ml · min−1. The bias in predictions for the 3 forms of exercise could be removed by applying the appropriate regression equations relating predicted to observed $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ , but the overall accuracy of the extrapolation method was limited to ± 8%, ± 15% and ± 23% in 1-leg, 2-arm and 1-arm work respectively. It was concluded that maximal work with the upper and lower limbs should be treated separately and if an accuracy of greater than ± 8 to ± 23% is required in situations where through injury, two limb exercise cannot be performed, attempts should be made to ascertain the $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ of a single limb directly.

The change in plasma catecholamine concentration (ΔC) has been studied in four healthy male subjects during work, involving different muscle groups, whilst breathing air and 45% oxygen. The results show that during arm and (1- and 2-) leg(s) work ΔC was more closely associated with relative (expressed as a % of $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ) than absolute work load; a rise in C occurred at ∼ 60% $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ in all 3 forms of exercise. However, in arm and 1-leg work the curves relating ΔC to % $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ were displaced to the right indicating the independence of the two variables. Further, breathing 45% oxygen reduced ΔC but was without effect on either $$\dot V_{O_2 } $$ at a given work load or $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . For a given $$\dot V_{O_2 } $$ , ΔC was inversely related to the effective muscle (plus bone) volume used to perform the work and associated with change of blood lactic acid (LA) concentration, but again the use of exercise involving different muscle groups indicated that the changes in C and LA were essentially independent. This was also true of the changes of C with cardiac output but not cardiac frequency (f H ). Plasma C changed as a curvilinear function of f H , the association between the two variables being independent of type of exercise and inspired O2 concentration within the range used in this study. This suggests that the rise in C and f H in exercise may be closely related to circulatory stress and may reflect the degree of vasoconstriction present in ‘non-active’ tissues and efficacy of the body's ability to maintain the integrity of systemic blood pressure in the face of increased demands of the exercising muscles for blood and the transport of oxygen.

The cardiac frequency and consumption of oxygen during submaximal exercise, lean body mass, total body potassium, thigh muscle width and an index of thigh muscle volume have been obtained for seventy-nine healthy men and women, ages 18 to 38 yrs, who were not in athletic training but accustomed to taking some exercise. For these subjects, at any specified submaximal rate of consumption of oxygen, the cardiac frequency is negatively correlated with the indices of body muscle which are themselves inter-correlated (r 〉 0·89). The latter relationships provide a basis for prediction of total body potassium (coefficient of variation 6·1 %). The relationship of exercise cardiac frequency to body muscle is similar in both men and women; it provides a better description of frequency than one based on consumption of oxygen alone (coefficient of variation respectively 12% and 18%). Cardiac frequency is independently related to the level of habitual activity of the subjects. The implications of these findings are discussed.

Four exercise tests have been examined as guides to maximal oxygen uptake measured directly using as subjects 101 volunteer mine rescue brigadesmen. The following indices were compared: (1) maximal O2 uptake per kg body mass during running on treadmill ([ndot]O2maxkg-1), (2) Harvard pack index (HPI), (3) cardiac frequency in the sixth minute of treadmill walking (speed 5 kph, incline 7.5°), (4) cardiac frequency in the sixth minute of stepping exercise (box height 32cm, frequency 20 per minute), (5) workload per kg body mass associated with cardiac frequency of 150 per minute during progressive cycle test (2 min each at 100,125 and 150 W). The scores for tests 3,4 and 5 were intercorrelated (r in the range 0.72-0.80) and each could be used to predict HPI (coefficient of variations ≃ 10%). None of the tests were reliable predictors of [ndot]O2maxkg-1. Thus there is a need for an alternative approach.

Maximum oxygen uptake $$\left( {\dot V_{{\text{O}}_{{\text{2max}}} } } \right)$$ was measured directly and predicted from cardiac frequency measurements in 54 healthy Chilean industrial workers aged 20 to 55 years, together with assessment of their dietary intake, body compositon and blood chemistry. Measurement of $$\dot V_{{\text{O}}_{\text{2}} } $$ was performed on a motor-driven treadmill. The predicted was obtained using a cycle ergometer by two methods: 1) the Astrand-Ryhming nomogram and 2) the linear relationship between “steady state” heart rate (HR) and submaximum work, with subsequent extrapolation to “maximum” heart rate. Extrapolation of the HR/load regression line to 170 bpm permitted determination of the physical working capacity at 170 bpm (W170). $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ for the 20–29 year group (Group I) averaged 3624 ml · min−1 and decreased to 3066 ml · min−1 in the 50–55 year group (Group IV). Lower values were obtained using the Astrand-Ryhming nomogram and HR/load regression (-15% and -9% respectively). W170 was also affected by age (Group I: 190.6 W and Group IV: 158.5 W). No significant correlation were found between $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ and plasma variables, with the exception of cholesterol (r=0.59). On the contrary, anthropometric variables showed significant correlations with $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ , which permitted the prediction of $$\dot V_{{\text{O}}_{{\text{2max}}} } $$ using multiple regression equations. The two best correlations were: 1. $$\begin{gathered} \dot V_{{\text{O}}_{{\text{2 max}}} } = 0.800 - 0225 \cdot \left( {\text{A}} \right) \hfill \\ + 0.0189 \cdot \left( {\text{W}} \right) + 1.26 \cdot \left( {\text{H}} \right) \hfill \\ \left( {r = 0.87;p< 0.001} \right) \hfill \\ \end{gathered} $$ 2. $$\begin{gathered} \dot V_{{\text{O}}_{{\text{2 max}}} } = 0.996 - 0.0176 \cdot \left( {\text{A}} \right) \hfill \\ + 0.025 \cdot \left( {\text{W}} \right) + 0.838 \cdot \left( {\text{H}} \right) + 0.0255 \cdot \left( {{\text{LBM}}} \right) \hfill \\ \left( {r = 0.88;p< 0.001} \right) \hfill \\ \end{gathered} $$ where A=years of age; W=body weight in kg; H=height in m and LBM=lean body mass in kg.

Amongst 288 healthy male workers in heavy industry the radiographic heart volume was related to the fat-free mass and the percentage body fat which between them explained 27% of the variance. Exercise was performed on a treadmill using a belt speed of 80 m.min-1 (3 mph) and an incline which was increased progressively to 14% when the oxygen uptake was on average 61% of the maximum for these subjects. The exercise cardiac output was related to the uptake of oxygen, the fat-free mass and the ambient temperature; these factors accounted for 52% of the variance. The exercise stroke volume was related to the heart volume, the fat-free mass, the thigh muscle width, the ambient temperature, the Harvard Pack Index and other measurements which between them accounted for 42% of the variance. The exercise cardiac frequency was correlated negatively with the heart volume, the fat-free mass, the age and the Harvard Pack Index. The variates between them described 41% of the variance. The findings provide reference values for heart volume, stroke volume and exercise cardiac frequency in similar subjects.

T HE STRIKING VARIATIONS in heart rate that occur during differing physiologic states in man and other mammals are so well known that they are frequently taken for granted. Cardiac rate frequently rises to over 200/min during maximal exercise in man, ’ to a somewhat higher level in the higher subhuman primate,2 and to over 300/min in the exercising dog.3-” On the other hand, extreme bradycardia may occasionally occur in man during immersion of the head into water, while rates as low as 4/min regularly occur in marine mammals during diving.6,7 A similar intense bradycardia, but much more sustained, occurs in some mammals during hibernation.x In human disease states, ventricular rate may vary over a tenfold range, from as low as 25/min to levels in excess of 250/min. Rates outside these limits may occur for brief periods but cannot be sustained. An understanding of the mechanism of control of heart rate, the importance of normal adjustments, and the consequence of disturbance of these adjustments are of critical importance not only to the cardiovascular physiologist but to the physician called upon to deal with patients with disturbances of impulse formation and a variety of other cardiac disorders. It is the purpose of this review to aid in providing such an understanding by summarizing the results of some of the important relevant experiments.

1. The physiological responses to repeated continuous (progressive) exercise together with the relationship between continuous and discontinuous work tests on an upright bicycle ergometer have been studied in healthy male subjects. 2. The results show a marked decline in mean cardiac frequency (fH) from 145 beats/min to 124 beats/min during the first four experiments at a given submaximal oxygen intake of 1·5 1/min and thereafter a smaller decline to reach 118 beats/min on the final (sixteenth) day of the investigation. This latter decrease was associated with a small but significant rise in maximum oxygen intake (V̇O2 max) which occurred from Day 8 onwards. Pulmonary minute ventilation at an oxygen intake of 1·5 1/min (V̇E 1·5) decreased by about 5 1/min immediately following the first occasion of submaximal work but thereafter remained unchanged. There was however no decrease in O2 cost of exercise, as V̇O2 at a fixed rate of external work remained unchanged throughout the investigation. 3. At maximal effort there was no significant decrease in either V̇E max or fHmax, but the fH at which the V̇O2 max was reached declined significantly from Day 8. Thus the asymptotic nature of the fH/V̇O2 curve which was very pronounced on Day 1 virtually disappeared following the third visit to the laboratory. The accuracy of predicting V̇O2 max from fH and V̇O2 increased noticeably from − 15·4 ± 8·9% on Day 1 to −6·5 ± 10·5% on Day 7 and −0·9 ± 3·4% on Day 15. The possible physiological basis and implications of the results are discussed. 4. No significant differences were found between continuous and discontinuous work. Thus in large scale population studies of work capacity or in the evaluation of training programmes in rehabilitation studies, a continuous test may be used but attention must be paid to familiarization procedures. At least three preliminary test periods are necessary before the results become reproducible and reliable.

Davies, C. T. M., and van Haaren, J. P. M. (1973). British Journal of Industrial Medicine, 30, 335-340. Effect of treatment on physiological responses to exercise in East African industrial workers with iron deficiency anaemia. The physiological responses to exercise on an upright bicycle ergometer have been investigated in groups of anaemic (mean Hb = 7·8 g/100 ml) and control (mean Hb = 13·7 g/100 ml) East African industrial workers before and after treatment with oral iron (Fe 200 mg) tablets and on a third group of anaemic subjects (mean = 7·4 g/100 ml) who received no treatment. Before treatment anaemic subjects exercised with an increased cardiac frequency at a fixed oxygen intake (Vo 2 ) of 1·5 1/min and a marked reduction in predicted maximum aerobic power output when compared to normal controls. The effect of therapy was to reverse these changes so that no significant differences existed between the two treatment groups but both were significantly different from their anaemic controls. The pulmonary minute ventilation at a Vo 2 of 1·5 1/min and the Vo 2 at a work load of 8 820 Nm/min (900 kpm/min) were similar in all three groups of subjects and remained constant throughout the experimental investigation. The findings carry important implications for those engaged in industrial medicine in developing countries and show clearly that the debilitating effects of iron deficiency anaemia can be rapidly eliminated by simple and inexpensive therapy in factory workers without seriously disturbing their normal work routine.

Cardiac frequency (ƒH) and oxygen consumption (V˙o 2) during the transition from rest to exercise in relation to the aerobic capacity for work were studied in an Olympic athlete and a healthy male ...

The “ pulse-deficit ” concept of Davies is critically examined. The deficit is related to intensity of effort, but shows no threshold wrstetw figures for the first minute of activity are excluded. The 0—4 min. deficit is not correlated with lactate accumulation; further, the pulse rate continues to increase in the second five minutes of exercise. This late pulse deficit probably has more industrial significance than data for the period 0—4 min.; however, the concept then differs only marginally from the “ puissance maximale supportee”.

This study was conducted to determine if cardiac frequency is a factor in the rating of perceived exertion. 10 fit male Ss were exposed to a design that used heat to manipulate cardiac frequency. Five treatments of various work loads in neutral and hot-dry environments were used to elicit unequal cardiac frequencies for equal work loads and equal cardiac frequencies for unequal work loads. Respiratory and body temperature variables were also collected. Multivariate analysis showed that there was no significant difference between ratings of perceived exertion of equal work loads even though cardiac frequency had been significantly elevated by the heat. The rating of perceived exertion seemed to follow alterations in work load when an increment of more than 200 to 300 kpm/min. was used. Ss also demonstrated ability to partial out thermal sensations from ratings of perceived exertion.

Background: In patients with a dual dependence on alcohol and tobacco, the spontaneous discourse among doctors is not to encourage them to consider preparing to give up both substances. The argument put forward is that withdrawal would be more difficult. We wanted to compare the intensity of withdrawal symptoms in patients hospitalised for alcohol detoxification between smokers and non-smokers. Subject and methods: We compared patients hospitalised for alcohol detoxification who smoke versus non-smokers who received replacement therapy through benzodiazepines and not nicotine replacement. The blood pressure and the cardiac frequency measure on the first day of hospitalisation, the doses of Diazepam dispensed on the first day, and the Clinical Institute Withdrawal Assessment of Alcohol Scale Revised (CIWA-Ar) score on the second day were compared. Results: a trend emerged whereby smoking patients undergoing alcohol detoxification showed higher blood pressure, higher cardiac frequency and required higher doses of benzodiazepines on the first day of hospitalisation. Patients who smoke also had higher CIWA-Ar scores on the second day of hospitalisation. Discussion: from a physiological point of view, the intensity of the symptoms of alcoholic withdrawal seems to be greater in hospitalised patients who smoke vs. non-smokers in the first two days. Does giving up both substances at the same time result in fewer withdrawal symptoms? And in this case, should a double replacement be recommended: benzodiazepines and nicotine replacement therapy? Conclusion: to be able to refine the recommendations on alcohol-tobacco dual withdrawal programmes, other studies are needed to compare giving up both substances with or without nicotine replacement. © Medicinska naklada.

(1971). Some Further Comments on ‘ Cardiac Frequency in Relation to Aerobic Dapacity for Work’. Ergonomics: Vol. 14, No. 3, pp. 425-426.

The changes in plasma catecholamine concentration (δC) following Β-blockade (practolol, 15 mg) and atropinisation (Atropine, 1.8 mg) have been studied on 5 healthy male subjects during exercise on a motor driven treadmill. The results showed that for a given VO2 and % VO2 max, Β blockade was without effect on δC (except in one athletic subject), but atropine produced a rise in δC. In relation to Q, both drugs produced an increase in δC, but for a given cardiac frequency (f H ) δC was higher with Β blockade, and lower with atropinisation than found in control experiments. The intra- and inter-subject variability of δC in relation to f H was resolved by considering the change in cardiac frequency calculated from baseline value obtained during walking at 6.44 km/h on the level, and expressed as a percentage of the maximal f H attainable for given individuals under the different drug and control conditions (% δf H ). It was concluded that during short term exercise, the rise of δC in relation to % δf H reflects both the myocardial sensitivity to vagal and Β blockade, and the circulatory vasoconstrictor control of blood vessels which is required to sustain increases in systemic and muscle blood flow.