Neurobehavioral meaning of pupil size.

Pupil size is a widely used metric of brain state. It is one of the few signals originating from the brain that can be readily monitored with low-cost devices in basic science, clinical, and home settings. It is, therefore, important to investigate and generate well-defined theories related to specific interpretations of this metric. What exactly does it tell us about the brain? Pupils constrict in response to light and dilate during darkness, but the brain also controls pupil size irrespective of luminosity. Pupil size fluctuations resulting from ongoing "brain states" are used as a metric of arousal, but what is pupil-linked arousal and how should it be interpreted in neural, cognitive, and computational terms? Here, we discuss some recent findings related to these issues. We identify open questions and propose how to answer them through a combination of well-defined tasks, neurocomputational models, and neurophysiological probing of the interconnected loops of causes and consequences of pupil size.

Orexin neurons track temporal features of blood glucose in behaving mice.

Does the brain track how fast our blood glucose is changing? Knowing such a rate of change would enable the prediction of an upcoming state and a timelier response to this new state. Hypothalamic arousal-orchestrating hypocretin/orexin neurons (HONs) have been proposed to be glucose sensors, yet whether they track glucose concentration (proportional tracking) or rate of change (derivative tracking) is unknown. Using simultaneous recordings of HONs and blood glucose in behaving male mice, we found that maximal HON responses occur in considerable temporal anticipation (minutes) of glucose peaks due to derivative tracking. Analysis of >900 individual HONs revealed glucose tracking in most HONs (98%), with derivative and proportional trackers working in parallel, and many (65%) HONs multiplexed glucose and locomotion information. Finally, we found that HON activity is important for glucose-evoked locomotor suppression. These findings reveal a temporal dimension of brain glucose sensing and link neurobiological and algorithmic views of blood glucose perception in the brain's arousal orchestrators.

Exploratory Rearing Is Governed by Hypothalamic Melanin-Concentrating Hormone Neurons According to Locus Ceruleus.

Information seeking, such as standing on tiptoes to look around in humans, is observed across animals and helps survival. Its rodent analog-unsupported rearing on hind legs-was a classic model in deciphering neural signals of cognition and is of intense renewed interest in preclinical modeling of neuropsychiatric states. Neural signals and circuits controlling this dedicated decision to seek information remain largely unknown. While studying subsecond timing of spontaneous behavioral acts and activity of melanin-concentrating hormone (MCH) neurons (MNs) in behaving male and female mice, we observed large MN activity spikes that aligned to unsupported rears. Complementary causal, loss and gain of function, analyses revealed specific control of rear frequency and duration by MNs and MCHR1 receptors. Activity in a key stress center of the brain-the locus ceruleus noradrenaline cells-rapidly inhibited MNs and required functional MCH receptors for its endogenous modulation of rearing. By defining a neural module that both tracks and controls rearing, these findings may facilitate further insights into biology of information seeking.

Control and coding of pupil size by hypothalamic orexin neurons.

Brain orexin (hypocretin) neurons are implicated in sleep-wake switching and reward-seeking but their roles in rapid arousal dynamics and reward perception are unclear. Here, cell-specific stimulation, deletion and in vivo recordings revealed strong correlative and causal links between pupil dilation-a quantitative arousal marker-and orexin cell activity. Coding of arousal and reward was distributed across orexin cells, indicating that they specialize in rapid, multiplexed communication of momentary arousal and reward states.

Rational inattention in mice.

Behavior exhibited by humans and other organisms is generally inconsistent and biased and, thus, is often labeled irrational. However, the origins of this seemingly suboptimal behavior remain elusive. We developed a behavioral task and normative framework to reveal how organisms should allocate their limited processing resources such that sensory precision and its related metabolic investment are balanced to guarantee maximal utility. We found that mice act as rational inattentive agents by adaptively allocating their sensory resources in a way that maximizes reward consumption in previously unexperienced stimulus-reward association environments. Unexpectedly, perception of commonly occurring stimuli was relatively imprecise; however, this apparent statistical fallacy implies "awareness" and efficient adaptation to their neurocognitive limitations. Arousal systems carry reward distribution information of sensory signals, and distributional reinforcement learning mechanisms regulate sensory precision via top-down normalization. These findings reveal how organisms efficiently perceive and adapt to previously unexperienced environmental contexts within the constraints imposed by neurobiology.

Perisaccadic perceptual mislocalization is different for upward saccades.

Saccadic eye movements, which dramatically alter retinal images, are associated with robust perimovement perceptual alterations. Such alterations, thought to reflect brain mechanisms for maintaining perceptual stability in the face of saccade-induced retinal image disruptions, are often studied by asking subjects to localize brief stimuli presented around the time of horizontal saccades. However, other saccade directions are not usually explored. Motivated by recently discovered asymmetries in upper and lower visual field representations in the superior colliculus, a structure important for both saccade generation and visual analysis, we observed significant differences in perisaccadic perceptual alterations for upward saccades relative to other saccade directions. We also found that, even for purely horizontal saccades, perceptual alterations differ for upper vs. lower retinotopic stimulus locations. Our results, coupled with conceptual modeling, suggest that perisaccadic perceptual alterations might critically depend on neural circuits, such as superior colliculus, that asymmetrically represent the upper and lower visual fields. NEW & NOTEWORTHY Brief visual stimuli are robustly mislocalized around the time of saccades. Such mislocalization is thought to arise because oculomotor and visual neural maps distort space through foveal magnification. However, other neural asymmetries, such as upper visual field magnification in the superior colliculus, may also exist, raising the possibility that interactions between saccades and visual stimuli would depend on saccade direction. We confirmed this behaviorally by exploring and characterizing perisaccadic perception for upward saccades.

[Parameters of Anaerobic Physiological Profile of Elite Athletes].

INTRODUCTION: Anaerobic capacity is much less evaluated in literature compared to aerobic component. Anaerobic performance of athletes can be measured using different motoric tests, lasting 20 to 30 seconds, one of them being the Wingate anaerobic test (WAnT). OBJECTIVE: The aim of this study was to determine the work performed and power generated by athletes and non-athletes during a 30-second high intensity exercise, as well as to compare explosive characteristics of subjects using a new parameter of WAnT, named explosive power, or slope of power. METHODS: All parameters of anaerobic power were investigated in 152 subjects classed into different groups depending on their physical fitness and sport specialties as follows: non-athletes (n=31), rowers (n=26), volleyball players (n=37), handball players (n=34) and judo players (n=24). The WAnT, as well as basic anthropometric measurements, was administrated to all participants. RESULTS: Values of anaerobic parameters were higher in the group of athletes compared to physically inactive subjects.The highest values of the WAnT parameters were registered in the group of volleyball players (AP=1 006 W; relative AP=11.4 W/ kg, AC=19.8 kJ), compared to athletes of other sport disciplines (volleyball, rowing and judo). The new parameter of the WAnT, explosive power, also showed highest values in volleyball players (EP=1 54 W/s; relative EP=1.74 W/s/kg). These differences were statistically significant (p<0.05). CONCLUSION: The results of laboratory tests can provide useful information on improvements in training processes. The new parameter of the WAnT could be implemented in further analyses of explosive characteristics of muscle contraction.

Changes in strength, endurance, and fatigue during a resistance-training program for the triceps brachii muscle.

CONTEXT: As a result of the adaptation process, some functional properties show different functions over time during strength training. Muscle strength and fatigue may show different adaptation patterns in reaching the improvement plateau after several weeks of training. OBJECTIVE: To follow muscle endurance and fatigue values during resistance training of the elbow extensors in young nonathletes. DESIGN: Descriptive laboratory study. SETTING: Controlled laboratory. PATIENTS OR OTHER PARTICIPANTS: Nineteen healthy young nonathletes (age = 21.0 ± 1.1 years; body mass index = 25.2 ± 2.9 kg/m(2)). INTERVENTION(S): Triceps brachii resistance training was performed on the isoacceleration dynamometer for 10 weeks (frequency = 5 times a week, 5 sets of 10 maximal elbow extensions, 1-minute resting period between sets). MAIN OUTCOME MEASURE(S): Measurements of endurance strength and fatigability were conducted using the same equipment, and endurance strength (ES), fatigue rate (FR), and decrease in strength (DS) were defined. RESULTS: All measured values for triceps brachii strength changed after training (ES increased by 57%, FR decreased by 68%, and DS improved by 59%; P < .001). No correlation was found between ES and the fatigability values-FR and DS (r(2) = 0.37 for FR and r(2) = 0.04 for DS; P > .05). The FR and DS trends showed specific functions, which reached a plateau after 4 weeks of training, and we found no further weekly changes in these values as the training continued. As an adaptation to exercise, ES showed a continuous, yet not linear, increase. CONCLUSIONS: Fatigability in the triceps brachii decreased in the first 4 weeks of training. After that period, muscle functional properties improved as a result of increased endurance.

Cardiac power output and its response to exercise in athletes and non-athletes.

Cardiac power output (CPO) is an integrative measure of overall cardiac function as it accounts for both, flow- and pressure-generating capacities of the heart. The purpose of the present study was twofold: (i) to assess cardiac power output and its response to exercise in athletes and non-athletes and (ii) to determine the relationship between cardiac power output and reserve and selected measures of cardiac function and structure. Twenty male athletes and 32 age- and gender-matched healthy sedentary controls participated in this study. CPO was calculated as the product of cardiac output and mean arterial pressure, expressed in watts. Measures of hemodynamic status, cardiac structure and pumping capability were assessed by echocardiography. CPO was assessed at rest and after peak bicycle exercise. At rest, the two groups had similar values of cardiac power output (1·08 ± 0·2 W versus 1·1 ± 0·24 W, P>0·05), but the athletes demonstrated lower systolic blood pressure (109·5 ± 6·2 mmHg versus 117·2 ± 8·2 mmHg, P<0·05) and thicker posterior wall of the left ventricle (9·8 ± 1 mm versus 9 ± 1·1 mm, P<0·05). Peak CPO was higher in athletes (5·87 ± 0·75 W versus 5·4 ± 0·69 W, P<0·05) as was cardiac reserve (4·92 ± 0·66 W versus 4·26 ± 0·61 W, P<0·05), respectively. Peak exercise CPO and reserve were only moderately correlated with end-diastolic volume (r = 0·54; r = 0·46, P<0·05) and end-diastolic left ventricular internal diameter (r = 0·48; r = 0·42, P<0·05), respectively. Athletes demonstrated greater maximal cardiac pumping capability and reserve than non-athletes. The study provides new evidence that resting measures of cardiac structure and function need to be considered with caution in interpretation of maximal cardiac performance.

Bradykinin type 2 receptor -9/-9 genotype is associated with triceps brachii muscle hypertrophy following strength training in young healthy men.

BACKGROUND: Bradykinin type 2 receptor (B2BRK) genotype was reported to be associated with changes in the left-ventricular mass as a response to aerobic training, as well as in the regulation of the skeletal muscle performance in both athletes and non-athletes. However, there are no reports on the effect of B2BRK 9-bp polymorphism on the response of the skeletal muscle to strength training, and our aim was to determine the relationship between the B2BRK SNP and triceps brachii functional and morphological adaptation to programmed physical activity in young adults. METHODS: In this 6-week pretest-posttest exercise intervention study, twenty nine healthy young men (21.5 ± 2.7 y, BMI 24.2 ± 3.5 kg/m(2)) were put on a 6-week exercise protocol using an isoacceleration dynamometer (5 times a week, 5 daily sets with 10 maximal elbow extensions, 1 minute rest between sets). Triceps brachii muscle volumes were assessed by using magnetic resonance imaging before and after the strength training. Bradykinin type 2 receptor 9 base pair polymorphism was determined for all participants. RESULTS: Following the elbow extensors training, an average increase in the volume of both triceps brachii was 5.4 ± 3.4% (from 929.5 ± 146.8 cm(3) pre-training to 977.6 ± 140.9 cm(3) after training, p<0.001). Triceps brachii volume increase was significantly larger in individuals homozygous for -9 allele compared to individuals with one or two +9 alleles (-9/-9, 8.5 ± 3.8%; vs. -9/+9 and +9/+9 combined, 4.7 ± 4.5%, p < 0.05). Mean increases in endurance strength in response to training were 48.4 ± 20.2%, but the increases were not dependent on B2BRK genotype (-9/-9, 50.2 ± 19.2%; vs. -9/+9 and +9/+9 combined, 46.8 ± 20.7%, p > 0.05). CONCLUSIONS: We found that muscle morphological response to targeted training - hypertrophy - is related to polymorphisms of B2BRK. However, no significant influence of different B2BRK genotypes on functional muscle properties after strength training in young healthy non athletes was found. This finding could be relevant, not only in predicting individual muscle adaptation capacity to training or sarcopenia related to aging and inactivity, but also in determining new therapeutic strategies targeting genetic control of muscle function, especially for neuromuscular disorders that are characterized by progressive adverse changes in muscle quality, mass, strength and force production (e.g., muscular dystrophy, multiple sclerosis, Parkinson's disease).

Relationship between peak cardiac pumping capability and indices of cardio-respiratory fitness in healthy individuals.

Cardiac power output (CPO) is a unique and direct measure of overall cardiac function (i.e. cardiac pumping capability) that integrates both flow- and pressure-generating capacities of the heart. The present study assessed the relationship between peak exercise CPO and selected indices of cardio-respiratory fitness. Thirty-seven healthy adults (23 men and 14 women) performed an incremental exercise test to volitional fatigue using the Bruce protocol with gas exchange and ventilatory measurements. Following a 40-min recovery, the subjects performed a constant maximum workload exercise test at or above 95% of maximal oxygen consumption. Cardiac output was measured using the exponential CO(2) rebreathing method. The CPO, expressed in W, was calculated as the product of the mean arterial blood pressure and cardiac output. At peak exercise, CPO was well correlated with cardiac output (r = 0·92, P<0·01), stroke volume (r = 0·90, P<0·01) and peak oxygen consumption (r = 0·77, P<0·01). The coefficient of correlation was moderate between CPO and anaerobic threshold (r = 0·47, P<0·01), oxygen pulse (r = 0·57, P<0·01), minute ventilation (r = 0·53, P<0·01) and carbon dioxide production (r = 0·56, P<0·01). Small but significant relationship was found between peak CPO and peak heart rate (r = 0·23, P<0·05). These findings suggest that only peak cardiac output and stroke volume truly reflect CPO. Other indices of cardio-respiratory fitness such as oxygen consumption, anaerobic threshold, oxygen pulse, minute ventilation, carbon dioxide production and heart rate should not be used as surrogates for overall cardiac function and pumping capability of the heart.

Triceps brachii strength and regional body composition changes after detraining quantified by MRI.

PURPOSE: To determine the triceps brachii functional adaptation and regional body composition changes after 12 months of detraining. MATERIALS AND METHODS: Seventeen healthy young men (22.2 ± 1.0 y, body mass index 24.9 ± 3.1 kg/m(2) ) were put in the detraining regimen for 12 months after completing a 12-week exercise protocol on isoacceleration dynamometer (5 times a week, 5 daily series with 10 maximal elbow extensions, 1 min rest between sets). Triceps brachii muscle strength was measured by isoacceleration dynamometry, using identical protocol as during the training. Muscle volumes, subcutaneous adipose tissue (SCAT), and intermuscular adipose tissue (IMAT) at mid-humerus were assessed by using MRI. RESULTS: Long-term detraining resulted in the significant decrease of 17% and 19% in endurance strength and fatigue rate, respectively. Maximal muscle strength slightly changed, and its 4% decrease was not significant. Triceps brachii volumes of both arms returned to their pretraining values (475.7 ± 54.91 cm(3) for right arm, and 483.9 ± 77.5 cm(3) for left arm). IMAT depots in upper arm significantly increased by 14% after 12 months of detraining, when compared with baseline values (P < 0.05). CONCLUSION: Long-term detraining leads to triceps brachii adaptation with endurance strength decrease, volume return to its baseline values, and significant IMAT accumulation. IMAT values after 12 months of detraining exceed baseline, pretraining values, which is significant accumulation as a result of physiologically decreased muscle activity.

The validity of estimating triceps brachii volume from single MRI cross-sectional area before and after resistance training.

The aim of this study was to determine whether triceps brachii muscle volume can be adequately estimated from a single anatomical cross-sectional area (ACSA) and can the same model be used for prediction after training. Thirty-five healthy male non-athletes (age 21.6 ± 2.5 years, body mass index 24.8 ± 3.5 kg · m(-2)) volunteered for this study. The volumes of the upper arm extensors were calculated from magnetic resonance imaging (MRI) sequence scans and regression models were developed, which were used to predict muscle volumes from single MRI cross-sectional scans taken at different points along the humerus length. The same procedure was repeated after 12 weeks of maximal resistance training of the elbow extensors. Correlation coefficients were calculated for Model A with CSA(max), humerus length (HL), and body mass index (r = 0.919), a model with CSA(50%) and HL (r = 0.922), and a model with CSA(60%) and HL (r = 0.920) (P < 0.001). The standard error of estimate for Model A, Model CSA(50%), and Model CSA(60%) was 8.0%, 7.7%, and 7.8% respectively. Thesame prediction formula can be used for the left arm (r = 0.904). If a single ACSA is used for triceps brachii volume prediction, the best fit is with Model CSA(60%) and HL, both before and after training (r = 0.941). By introducing humerus length into the calculation, we simplify the procedure for volume measurement, since it can be obtained during MRI scanning.

Heart rate recovery after submaximal exercise in four different recovery protocols in male athletes and non-athletes.

The effects of different recovery protocols on heart rate recovery (HRR) trend through fitted heart rate (HR) decay curves were assessed. Twenty one trained male athletes and 19 sedentary male students performed a submaximal cycle exercise test on four occasions followed by 5 min: 1) inactive recovery in the upright seated position, 2) active (cycling) recovery in the upright seated position, 3) supine position, and 4) supine position with elevated legs. The HRR was assessed as the difference between the peak exercise HR and the HR recorded following 60 seconds of recovery (HRR60). Additionally the time constant decay was obtained by fitting the 5 minute post-exercise HRR into a first-order exponential curve. Within- subject differences of HRR60 for all recovery protocols in both groups were significant (p < 0. 001) except for the two supine positions (p > 0.05). Values of HRR60 were larger in the group of athletes for all conditions (p < 0.001). The time constant of HR decay showed within-subject differences for all recovery conditions in both groups (p < 0.01) except for the two supine positions (p > 0.05). Between group difference was found for active recovery in the seated position and the supine position with elevated legs (p < 0.05). We conclude that the supine position with or without elevated legs accelerated HRR compared with the two seated positions. Active recovery in the seated upright position was associated with slower HRR compared with inactive recovery in the same position. The HRR in athletes was accelerated in the supine position with elevated legs and with active recovery in the seated position compared with non-athletes. Key pointsIn order to return to a pre-exercise value following exercise, heart rate (HR) is mediated by changes in the autonomic nervous system but the underlying mechanisms governing these changes are not well understood.Even though HRR is slower with active recovery, lactate elimination after high intensity exercise might be more important for athletes than the de-cline of heart rate.Lying supine during recovery after exercise may be an effective means of transiently restoring HR and vagal modulation and a safe position for prevention of syncope.

Morpho-functional response of the elbow extensor muscles to twelve-week self-perceived maximal resistance training.

The aim of this study was to determine morphological and functional changes of the elbow extensor muscles in response to a 12-week self-perceived maximal resistance training (MRT). Twenty-one healthy sedentary young men were engaged in elbow extensor training using isoacceleration dynamometry for 12 weeks with a frequency of five sessions per week (five sets of ten maximal voluntarily contractions, 1-min rest period between each set). Prior to, at 6 weeks and after the training, a series of cross-sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated. Maximal and endurance strength increased (P<0.01) by 15% and 45% at 6 weeks, and by 29% and 70% after 12 weeks compared with baseline values, while fatigue rate of the elbow extensors decreased by 67%. The volume of triceps brachii increased in both arms (P<0.01) by 4% at 6 weeks, and by 8% after 12 weeks compared with baseline values (right arm--from 487.4 ± 72.8 cm³ to 505.8 ± 72.3 cm³ after 6 weeks and 525.3 ± 73.7 cm³ after 12 weeks; left arm--from 475.3 ± 79.1 cm³ to 493.2 ± 72.7 cm³ after 6 weeks and 511.3 ± 77.0 cm³ after 12 weeks). A high correlation was found between maximal muscle strength and muscle volume prior (r² = 0.62) and after (r² = 0.69) the training (P≤0.05). A self-perceived MRT resulted in an increase in maximal and endurance strength. Morphological adaptation changes of triceps brachii as a result of 12-week specific strength training can explain only up to 26% of strength gain.

Non-linear dynamics in muscle fatigue and strength model during maximal self-perceived elbow extensors training.

Our aim was to determine the dynamics in muscle strength increase and fatigue development during repetitive maximal contraction in specific maximal self-perceived elbow extensors training program. We will derive our functional model for m. triceps brachii in spirit of traditional Hill's two-component muscular model and after fitting our data, develop a prediction tool for this specific training system. Thirty-six healthy young men (21 +/- 1.0 y, BMI 25.4 +/- 7.2 kg/m(2)), who did not take part in any formal resistance exercise regime, volunteered for this study. The training protocol was performed on the isoacceleration dynamometer, lasted for 12 weeks, with a frequency of five sessions per week. Each training session included five sets of 10 maximal contractions (elbow extensions) with a 1 min resting period between each set. The non-linear dynamic system model was used for fitting our data in conjunction with the Levenberg-Marquardt regression algorithm. As a proper dynamical system, our functional model of m. triceps brachii can be used for prediction and control. The model can be used for the predictions of muscular fatigue in a single series, the cumulative daily muscular fatigue and the muscular growth throughout the training process. In conclusion, the application of non-linear dynamics in this particular training model allows us to mathematically explain some functional changes in the skeletal muscle as a result of its adaptation to programmed physical activity-training.

Comparative analysis of two different methods of anaerobic capacity assessment in sedentary young men.

BACKGROUND/AIM: The Wingate anaerobic test is a valid and reliable method of measuring anaerobic capacity. The aim of this study was to determine whether other modified test can be used instead of the Wingate test. METHODS: A group of 30 sedentary young men were first tested with a cycle ergometer (classic Wingate test), and then with a dynamometer during 30 s of "all out" leg extension exercise (modified Wingate test; WAnTe) in order to test anaerobic capacity. Subsequent correlations between these tests were made. RESULTS: Peak power, mean power on cycling ergometer in absolute and relative values were 463 +/- 105 W, 316.7 +/- 63.8 W, 5.68 +/- 1.17 W/kg, 3.68 +/- 0.78 W/kg, respectively. On a dynamometer absolute and relative values of maximal and mean load in kg and power in Watts were 136.54 +/- 21.3 kg, 1.67 +/- 0.26; 128.65 +/- 19.93 kg, 1.57 +/- 0.24 kg, 657 +/- 125.87 W, and 8 +/- 1.54 W/kg, respectively. There was no correlation between 5 s intervals of the classic Wingate test and WAnTe during the first, fourth and fifth intervals, but in the second (r = 0.49, p < 0.05), third (r = 0.38, p < 0.05) and last 5 s intervals (r = 0.39, p < 0.05), and also in peak power and mean power (r = 0.42, p < 0.05 and r = 0.45, p < 0.05 respectively), a significant positive correlation was detected. CONCLUSION: A modified Wingate test of leg extension on a dynamometer in sedentary young men shows a correlation with the classic Wingate test only in parameters of peak power, and mean power and the second, the third and the last 5 s intervals. Because of that it should only be used for orientation, whereas for precise measurements of anaerobic capacity the classic Wingate test should be used.

Heart rate variability before and after cycle exercise in relation to different body positions.

The purpose of this study was to assess the effect of three different body positions on HRV measures following short-term submaximal exercise. Thirty young healthy males performed submaximal cycling for five minutes on three different occasions. Measures of HRV were obtained from 5-min R to R wave intervals before the exercise (baseline) and during the last five minutes of a 15 min recovery (post-exercise) in three different body positions (seated, supine, supine with elevated legs). Measures of the mean RR normal-to-normal intervals (RRNN), the standard deviation of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD) and the low-frequency (LF) and the high-frequency (HF) spectral power were analyzed. Post-exercise RRNN, RMSSD were significantly higher in the two supine positions (p < 0. 01) compared with seated body position. Post-exercise ln LF was significantly lower in the supine position with elevated legs than in the seated body position (p < 0.05). No significant difference was found among the three different body positions for post-exercise ln HF (p > 0.05). Post-exercise time domain measures of HRV (RRNN, SDNN, RMSSD) were significantly lower compared with baseline values (p < 0.01) regardless body position. Post-exercise ln LF and ln HF in all three positions remained significantly reduced during recovery compared to baseline values (p < 0.01). The present study suggests that 15 minutes following short-term submaximal exercise most of the time and frequency domain HRV measures have not returned to pre-exercise values. Modifications in autonomic cardiac regulation induced by body posture present at rest remained after exercise, but the post-exercise differences among the three positions did not resemble the ones established at rest. Key pointsWhether different body positions may enhance post-exercise recovery of autonomic regulation remains unclear.The absence of restoration of HRV measures after 15 minutes of recovery favor the existence of modifying effects of exercise on mechanisms underlying heart regulation.On the basis of discrepancies in HRV measures in different body positions pre- and post-exercise we argue that the pace of recovery of cardiac autonomic regulation is dependent on body posture.

Analysis of anaerobic capacity in rowers using Wingate test on cycle and rowing ergometer.

The 30-s all-out Wingate test has been used in athletes of all sport specialties to measure the capacity for short duration, high power output while cycling. The aim of this study was to establish differences in measuring anaerobic capacity between the classic Wingate test on a cycling ergometer and the modified Wingate test on a rowing ergometer in rowers. A group of20 rowers was tested by both the cycle and rowing ergometers during 30s of maximum power to test anaerobic capacity and to make correlation between these tests. The parameters measured were the peak power and mean power. The peak power on the cycling ergometer was 475 +/- 75.1W and 522.4 +/- 81W (p < 0.05) on the rowing ergometer. The mean power on the cycling ergometer and the rowing ergometer was 344.4 +/- 51.1W and 473.7W +/- 67.2, (p < 0.05) respectively. The maximum values were achieved at the same time on both ergometers, but remained on the higher level till the end of the test on the rowing ergometer. By correlating the anaerobic parameters of the classic Wingate test and a modified Wingate test on the rowing ergometer a significant positive correlation was detected in the peak power (r = 0.63, p < 0.05) as well as in the mean power (r = 0.65, p < 0.05). The results show that the rowers achieved better results of the anaerobic parameters on the rowing ergometer compared to the cycling ergometer due to a better mechanical efficiency. It is concluded that the modified Wingate test on the rowing ergometer can be used in rowers for testing their anaerobic capacity as a sport specific test ergometer since it provides more precise results.

[Identification and analysis of stress factors at nursing workplace: a comparative study of four clinical departments].

INTRODUCTION: Several studies show that nursing is, by its very nature, an occupation exposed to a high degree of stress. The main aims of the present research were to analyze the presence and to identify occupational stress factors and assess stress levels among nurses in clinical/hospital settings. MATERIAL AND METHODS: The research was conducted as a cross-sectional study. The sample included nurses (n=205) employed in different settings, who were also control groups to each other. Expanded Nursing Stress Scale and an additional questionnaire created for the purpose of this investigation were used as research instruments. RESULTS: The results show that stressful situations, in the psychological occupational environment are the greatest stress factors regardless of the workplace: in regard to sociodemographic determinants, married nurses have significantly higher average values as compared to unmarried ones (p<0.05), and the values statistically significantly lower in nurses under 30 years of age, with less than 10 years of work experience (p<0.01). Workload is a potential stress factor from the physical environment, whereas average values of this stress factor highly statistically differ in regard to the workplace (p<0.01). Nurses working in settings without support from their superiors and engaged in inter-professional conflicts, especially between nurses and physicians, face a great problem. CONCLUSION: It is important to promote conditions of work (work space, providing new equipment), organization of work, as well as social relationships, which is in accordance with the recommendations of ICN.